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Introduction/Purpose: Interpositional arthroplasty (IPA) is a motion-preserving surgery in patients with advanced hallux rigidus. Literature displays several complications after the procedure including transfer metatarsalgia, cock-updeformity and infection. In a finite element model, shortening of the first metatarsal was associated with increased plantar pressure on lateral rays during gait. Additionally, there are reports of a positive correlation between first metatarsal shortening after hallux valgus surgery and transfer metatarsalgia of the second,third and fourth metatarsophalangeal joints. The goals of this study were to report the outcomes and complications of IPA using acellular dermal allograft (IPA-ADA) as well as study the changes in the length of the proximal phalanx of the hallux (P1) and the first metatarsal (M1) following the procedure. Methods: In this IRB-approved retrospective study, we assessed patients who underwent IPA-ADA in a single academic institute from 2019-2022. All patients’ demographic data, surgical details, complications, and patient-reported outcomes (PROs) were extracted. On standing conventional anteroposterior (AP) foot views, we measured the lengths of the first metatarsal (M1), the second metatarsal (M2), the proximal phalanx of the big toe (P1), and the entire length of the hallux (HX). The ratio of M1/M2 and P1/HX were calculated. The first metatarsophalangeal joint space was measured at the medial and lateral aspects of the joint on the APview. All measurements were recorded pre-operatively, at six weeks follow-up, and at the final follow-up. Descriptive statistics were performed, and comparison between groups was performed using analysis of variance(ANOVA) or Kruskal Wallis test according to data normality. The Dunn-Bonferroni test was then performed for pairwise group comparisons. A p-value < 0.05 was considered significant. Results: Eleven patients were included, 9 being females (81.81%). Six were hallux rigidus Coughlin grade III (54.55%), and 5 were grade IV (45.45%). The average age was 59 years (SD±6.78), and the body mass index (BMI) was 26 (SD±4.79). At the final follow- up, there was significant shortening of the first ray in comparison to the pre-operative length evidenced by lower M1/M2 (82.63 SD±2.29 versus 75.42 SD±5.1; p=0.001) and P1/HX ratio53.38 ± 2.29 versus 48.98 SD ± 7.92; p=0.001). Although there was no significant difference between M1/M2 at 6 weeks and at the final follow-up (p=0.716), there was a significant negative correlation between follow-up length and M1/M2 (r= -0.76, p=0.003). Follow-up was (19.95 months; range 3-39). Complications and PROs are listed in Figure 1. Conclusion: Interposition arthroplasty using dermal allograft for HR is associated with progressive shortening of the first ray at the level of the first metatarsal as well as the proximal phalanx. Although the study did show shortening of the first ray, the small sample size didn't allow for a correlation between this shortening and complications such as transfer metatarsalgia and cock-up toe deformity. The potential shortening should be considered in the selection of patients, particularly in the setting of an already short first metatarsal or when simultaneous Akin/Moberg osteotomy is planned. Interposition arthroplasty using dermal allograft for HR is associated with progressive shortening of the first ray at the level of the first metatarsal as well as the proximal phalanx. Although the study did show shortening of the first ray, the small sample size didn't allow for a correlation between this shortening and complications such as transfer metatarsalgia and cock-up toe deformity. The potential shortening should be considered in the selection of patients, particularly in the setting of an already short first metatarsal or when simultaneous Akin/Moberg osteotomy is planned.

Introduction/Purpose: Evidence in the literature suggests the negative effects of using High Heels (HH), becoming a challenge for clinicians and researchers since they are welcomed by women worldwide, mainly due to the subjective power of attractiveness given to them. Although some people blame HH as one of the causes of Hallux Valgus (HV), until now, there are no studies in the literature that effectively prove a cause-effect relationship between HH and HV. The objectives of this study are: (1) to analyze whether the increase in heel height can lead to HV and (2) to evaluate whether HV can increase in severity with increasing heels. We hypothesized that an increase in heel height could cause and increase the severity of HV deformity. Methods: Comparative cross-sectional study. Forty-one feet from twenty-one participants (11 males and 10 females, aged 30.8 ± 8.9 years, and with Body Mass Index 25.5 ± 2.0 m kg2) were recruited. HH shoes were designed for this study with three heights for each participant: 3, 6, and 9 cm. The inclusion criteria were: no regular wearing of heels. The exclusion criteria were: Hallux Valgus diagnosis and/or any orthopedic conditions that affect the Foot and Ankle joints. Hallux Valgus Angle (HVA), Intermetatarsal Angle (IMA), First-Metatarsal Phalangeal Angle, 1st-to-5th Intermetatarsal Angle, First Tarsometatarsal Angle (axial), Second tarsometatarsal angle (axial), Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle and, Foot Ankle Offset (FAO) were measurement using semiautomated software analysis. Multiple comparisons were performed (Bonferroni's for normal distributions and Wilcoxon test for no normal distributions) when there was a main effect on an outcome (p < 0.05). Results: With the increase in HH, we noticed a progressive increase in HVA (p < 0.001), IMA (p < 0.001), First-Metatarsal Phalangeal Angle (p < 0.001), First Tarsometatarsal Angle (axial) (p < 0.001), and the Second tarsometatarsal angle (axial) (p < 0.001). The Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle, and Foot Ankle Offset (FAO) had hindfoot varization behavior. When we stratified the groups and compared them, we noticed that an increase of 3 cm in heels slightly increased HVA and IMA (p > 0.05). However, heel increases above 6 cm significantly increased HVA and IMA (p > 0.001). Based on Coughlin's classification, a 3 cm heel increase promoted a mild HV and increases above 6 cm caused a moderate HV. Conclusion: Based on data from our study with patients without Hallux Valgus through analysis with WBCT versus high heels, we conclude that increasing heel height can lead to Hallux Valgus and can progressively increase the severity with increasing high heels. High heels above 6 cm can lead to moderate Hallux Valgus. These findings may be an essential step toward a better understanding of the effects of increasing high heels on Hallux Valgus pathology.

Introduction/Purpose: Few studies have assessed the long-term outcomes of the Ponseti technique and none have utilized 3- dimensional weightbearing analysis. The goal of this study was to understand how potential residual 3D deformities and abnormalities influence patient reported outcomes (PROs). This was accomplished by assessing anatomical foot and ankle alignment in adult clubfoot patients treated with the Ponseti method using 3D weightbearing CT (WBCT) imaging and then correlating residual foot and ankle malalignment with PROs. Methods: There were 37 consecutive patients (57 feet) included and 14 volunteers healthy controls (28 feet) included in this study. Every participant was evaluated using a WBCT (HiRise © ) in a bipedal standing position. From these scans Cavus, Adductus, and Varus components were evaluated using multiple 3D measurements calculated using the semi-automatic segmentation software Bonelogic ® . Specific Cavus related measurements included sagittal talus-first metatarsal angle and the calcaneal inclination angle. Varus related measurements included talocalcaneal angle in both the sagittal and axial planes as well as the hindfoot moment arm and the hindfoot alignment angle. Adductus deformity was evaluated using talonavicular coverage angle. These measurements were then correlated with patient reported outcome surveys, which included Visual Acuity Scale for pain, PROMIS general health, PROMIS physical function, PROMIS pain interference, pain catastrophic scale, and European foot and ankle society score. Results: There was no significant overall residual 3D-deformity observed in clubfoot patients when compared to controls, with similar FAO measurements observed between the groups, clubfoot=2.63% (95%CI=1.41%-3.85%) and control=3.2% (CI=1.6%- 4.8%,P=0.58). The sagittal talus-first-metatarsal in the clubfoot-patients had a mean-value of -0.12° compared to the controls, −5.2°. Clubfoot patients also had a decreased calcaneal-inclination-angle relative to the controls, 13.01° and 21.5° respectively. Talocalcaneal-angle for clubfoot patients in both the sagittal-plane,44.28°, and axial-plane, 17.74°, were reduced compared to the controls, 57.51° and 25.78°. Talonavicular-coverage-angle in the clubfoot-group (18.63°) was less than the controls (29.19°). Talus- first-metatarsal-angle in the sagittal-plane was significantly correlated with VAS-scores (RSquare=0.19,P=0.0118) and the EFAS- Score (RSquare=0.27,P=0.0025). Talocalcaneal-angle in the sagittal plane was also significantly correlated with the PROMIS-Pain- Interference-score (P=0.038) and PROMIS-Physical-Function-score (RSquare=0.32,P=0.0007). Conclusion: The Ponseti technique is an effective nonsurgical treatment for the overall three-dimensional foot and ankle alignment of Clubfoot. While mild, but statistically significant residual Varus and Adductus deformities were observed in adult clubfoot patients, the overall 3D alignment (FAO) was found to be similar between clubfoot patients and controls. These findings highlight the efficacy of the Ponseti technique and potentially explain the overall good PROs. The results of this study could potentially provide insight into treatment targets that may be applied to help optimize patient outcomes when treating children with Clubfoot in the future. The Ponseti technique is an effective nonsurgical treatment for Clubfoot's overall three-dimensional foot and ankle alignment. While mild, but statistically significant residual Varus and Adductus deformities were observed in adult clubfoot patients, the overall 3D alignment (FAO) was found to be similar between clubfoot patients and controls. These findings highlight the efficacy of the Ponseti technique and potentially explain the overall good PROs. The results of this study could potentially provide insight into treatment targets that may be applied to help optimize patient outcomes when treating children with Clubfoot in the future.

Category: Midfoot/Forefoot; Trauma Introduction/Purpose: Lisfranc complex stability, primarily coming from the tarsometatarsal ligaments, is crucial for midfoot integrity. It has been shown that Lisfranc injuries can lead to midfoot issues, such as midfoot arthritis when not properly diagnosed/treated. Previous studies have estimated the volumes of the articulating joint volumes of surgically confirmed Lisfranc Ligament injuries, but no study has assessed articulating joints and space-of-interest of the Lisfranc Complex in patients with midfoot arthritis. The objective of this retrospective study was to determine if patients with confirmed midfoot arthritis have increased volumes at the Lisfranc complex when compared to controls, particularly between the first and second rays. We hypothesized that volumes would be increased in midfoot arthritis patients, consistent with medial column/first ray instability. Methods: In this IRB-approved, retrospective case-control study, we analyzed WBCT data of 20 consecutive midfoot arthritis patients and 20 healthy controls. Using an automated segmentation method (DISIOR Bonelogic 2.0, Paragon28, USA), 3D volumetric models of the bones of the foot were created from WBCT data. Opposing articular spaces in the Lisfranc joint of the midfoot were selected on the STL models of the bones. Interarticular distance mapping was then performed to characterize the joint space width (JSW) in each of the articulations. Interarticular volume was then estimated using an area-weighted volume measurement. Areas of each triangle from the triangulated surface were multiplied by the JSW at each triangle. The sum of individual volumes was then normalized by the total surface area. The final volume was estimated using the product of the normalized summation and average area of both surfaces. Comparisons were performed with independent t-tests. P-values >0.05 were considered significant. Results: Estimates of joint volume were obtained using the automated method written in MATLAB. These outputs are reported in Table 1. Significant increase of approximately 25% was observed in Midfoot arthritis patients at the 1-2 intercuneiform joint, consistent with intercuneiform instability. Conversely, a decrease in the space between the second metatarsal and medial cuneiform of about 30% was observed, what could be explained by pronation of the first ray secondary to first ray instability. All other changes in joint volumes were not significant (Figure). Conclusion: In this case-control study with midfoot arthritis patients and healthy controls we performed a 3D volumetric assessment of the Lisfranc Complex joints and spaces-of-interest. We found that midfoot arthritis patients have a significant increase in the 1-2 intercuneiform joint consistent with intercuneiform instability. Conversely, a decrease in the Lisfranc space (in between second metatarsal and medial cuneiform) was observed, what could be explained by first ray pronation in the setting of medial column instability. Additional prospective studies assessing angular measurements and patient reported outcomes are needed.

Category: Ankle Arthritis; Other Introduction/ Purpose: Lower limb alignment assessment is commonly performed using two-dimensional (2D) conventional- radiographs. Weight-Bearing Computed-Tomography (WBCT) imaging that allows concomitant 3D imaging of the hip, knee, ankle, and foot, a more complete and multidimensional assessment of the entire overall lower limb alignment is now possible. The aims of this study were: (1) to characterize the normal relative 3D alignment of the center of the Hip, Knee, and Ankle joints in relation to the weight bearing Foot Tripod in a cohort of healthy control volunteers with no lower extremity pathologies, using WBCT imaging. (2) to perform the same 3D WBCT assessment in a cohort of patients with either hip osteoarthritis (HOA), knee osteoarthritis (KOA) or ankle osteoarthritis (AOA), and to compare the results between arthritic cases and controls. Methods: Prospective comparative and controlled cohort-study contained 7 HOA limbs (4 patients), 17 KOA limbs (10 patients), 7 AOA limbs (4 patients) and 10 control limbs (5 patients) that received WBCT imaging of the full lower extremity. Using multiplanar reconstruction WBCT images, 3D landmark coordinates (on X, Y, and Z planes) were manually measured by two observers. The utilized software (CubeVue ® ) generated an automatic calculation of the Foot-Hip Offset (FHO), Foot-Knee Offset (FKO) and Foot and Ankle Offset (FAO). The relationship between the center of the hip, knee and ankle joints and the bisecting line of the foot tripod was assessed and compared between HOA, KOA, AOA patients and controls. Examples of measurements for arthritic patients and controls is presented in Figure 1. Continuous data was assessed for normality with the Shapiro-Wilk test, and variables were compared using ANOVA or Kruskal- Wallis Rank Sum. P-Values of less than 0.05 were considered significant. Results: The average FAO and 95%-Confidence-intervals-(CI) for respectively HOA, KOA, AOA and controls were respectively: 3.62% (0.4 to 6.8) (neutral), 2.8% (0.78 to 4.9) (neutral), -4.68% (-7.8 to -1.4) (varus), and 2.12% (-0.5 to 4.8) (neutral). The FAO- differences were found to be significant between the groups (p=0.0077), with AOA patients being significantly different than all the other groups (Figure 2). Similarly, the HFO was found to be significantly different-between the groups (p=0.002), with the following average values and 95%CI for respectively HOA, KOA, AOA and controls: 0.7% (-6.4 to 7.8), 2.3% (-2.3 to 6.8), -10.1% (-17.2 to -3.0), and 5.3% (-0.6 to 11.3). Again, the AOA patients were found to be significantly different than the other groups. No significant differences were found between the groups when assessing the KFO (p=0.37). Conclusion: The baseline 3D lower limb alignment and relative position of the hip, knee, ankle and foot was assessed and established for the first time in the literature. When comparing 3D alignment in arthritic patients with hip, knee or ankle OA and controls, we observed that AOA was found to be the one affecting more the overall 3D alignment of the lower extremity, with no complete compensation of the deformity through the other joints, resulting in significantly different values of HFO, KFO and FAO in patients with ankle OA. Additional prospective studies with longer cohorts of patients are needed.

Category: Midfoot/Forefoot; Bunion Introduction/Purpose: Progressive collapsing foot deformity (PCFD), Hallux Valgus (HV), and Midfoot Arthritis (MA) are diseases that benefit from the Lapidus procedure due to its capability to provide a stable medial column while correcting the underlying deformity. However, the technique does not go without complications. First metatarsal shortening/dorsiflexion are not uncommon, which could be exacerbated by local anatomy/revision surgery settings. Restoring length and sagittal plane position (plantarflexion) of the first ray when treating these pathologies is paramount. Performing a primary distraction and plantarflexion fusion with an allograft wedge (LapiCotton) has been advocated in the literature, potentially allowing improved deformity correction, but with the risk of increased non-union rate. The objective of this study was to report medium-term follow-up results of the LapiCotton in patients with collapsed feet. Methods: This IRB-approved comparative prospective study assessed patients diagnosed with PCFD, HV, and MA undergoing a Lapidus bone-block fusion (LapiCotton) between August 2020 and November 2022. All patients were operated on by a single fellowship-trained foot and ankle surgeon after clinical evaluation and a weight-bearing computed tomography (WBCT). After adequate joint preparation and trials, a Lapidus pre-shaped wedge allograft was placed and fixed using available implants. Adjunctive procedures were carried out as needed. Patients were kept non-weight bearing for six weeks and followed clinically, performing a WBCT at three months and subsequent follow-up. Non-Union and complications were documented. Bone healing was determined by at least 50% of bone trabeculae crossing both graft interfaces at the WBCT. Forefoot arch angle (FFA), Meary’s angle, talonavicular coverage angle (TNCA), middle facet subluxation (MFS), and foot and ankle offset (FAO) were also obtained. Two fellowship-trained readers performed all assessments. P-values >0.05 were considered significant. Results: Fifty-eight patients (60 feet) were included, mean age 53.87 (range:18-77)/BMI 31.70 (SD:7.96). Twenty-four PCFD, 19 HV, and 17 MA had an average 15.47 months (4-31) follow-up. Cuneiform-Post implants were used in 62%, plates/screws in 25%, and Lapidus nails in 13%. Median allograft size was 9mm (mode:8mm,5-19mm). Minor complications were observed in 3% (two superficial dehiscences) and major in 7% (three deep infections [5%], and one EHL contracture [2%]). Healing at the 3-month WBCT occurred in 94.8% and only in 66% at the most-recent WBCT (mean:11.08 months; 6-20). The clinical non-union rate demanding reoperation was eight clinical non-unions 13%. Mean FFA (pre:6.89,SD:6.63; postop:14.21,SD:5.48; p< 0.001), Meary (pre:15.17,SD:8.12; postop:6.31,SD:5.61; p< 0.001), TNCA (pre:26.75,SD:11.77; postop:11.59,SD:7.91; p< 0.001), MFS (pre:36.3,SD:26; postop:23.49,SD:17.35; p< 0.001), and FAO (pre:6.71,SD:5.81; postop:2.2,SD:4.33; p< 0.001) improved after the interventions. Conclusion: Although the Lapidus bone-block arthrodesis (LapiCotton) restored many of the markers associated with foot collapse and alignment, non-union rated was noted in 13% what is on the top range of non-union rates reported in the literature for Lapidus arthrodesis. The use of allograft wedges in the fusion site probably explains our findings. The fact that the sample was heterogeneous and composed of considerably severe deformities should also be considered. Also, important to highlight that WBCT findings of fusion site healing was initially 94% at 3-months and only 66% at most recent follow-up). Additional studies and longer-term follow up are needed.

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Minimally invasive surgery (MIS) Chevron-osteotomy for HV treatment offers a surgical alternative to open surgery with minimal surgical dissection and a hypothetical decreased risk for soft-tissue complications. During this procedure, there is a concern regarding the injury to the blood supply of the 1st-metatarsal-head. The objective of this study was to assess the incidence of injuries: (1) to the soft-tissue envelope around the first metatarsal head complex and, (2) to the blood supply of the first metatarsal head and also by using Micro-CT, (3) looking for safe zones close to the first metatarsal head to perform MIS Chevron osteotomy. We hypothesized that the MIS Chevron-type osteotomy procedure would preserve the soft-tissue envelope of the first-metatarsal-head complex and the blood supply of the 1st-metatarsal-head. Methods: Sixteen HV deformity cadaveric specimens were used to perform MIS Chevron-type osteotomy of the first metatarsal head. Anatomical dissection of all specimens was then performed to assess macroscopic injury to the first metatarsal head complex soft-tissue structures, including Extensor Hallucis Longus (EHL) tendon, Extensor Hallucis Brevis (EHB) tendon, Flexor Hallucis Longus (FHL) tendon, Flexor Hallucis Brevis (FHB) tendon, Abductor Hallucis tendon, Adductor Hallucis tendon, Sesamoid complex, Dorsolateral and Dorsomedial digital branches of the first toe and the Dorsomedial digital branch to the second. Macroscopic injuries were classified using a calibrated digital caliper. Any chondral damage to the first metatarsal head was quantified in mm². To assess the amount of first metatarsal head blood supply, specimens were perfused with 200 ml of a low viscosity radiopaque polymer, MV 117 (Flowtech), preoperatively, followed by Micro-CT assessment. Descriptive statistics and percentages were utilized for categorical data. Results: We did not find injuries in the EHL, EHB, FHL, Abductor-Hallucis, and Adductor-Hallucis tendons. We found a 2mm injury in the FHB tendon in one specimen. No injuries were found in the Dorsomedial and Dorsolateral nerves of the first-toe, the Dorsomedial-nerve of the second-toe, and Medial branch of the dorsomedial-nerve of the first-toe. In 3 cases, we found an injury on first-metatarsal-head (1mm) due to the passage of the K-wire and, in 1 case, due to the inadvertent passage of the drill (4.41mm). Macroscopically and using Micro-CT, we did not observe injuries in the First-Dorsal-Metatarsal-Artery (FDMA), Lateral-Dorsal-Branch of FDMA, and Plantar-Metatarsal-Artery. Micro-CT helped estimate a safe distance to finish the proximal exit of Chevron-osteotomy (25mm from the most distal point of the first metatarsal head). Conclusion: In this study, the minimally invasive Chevron osteotomy for treating HV seems to be a technically safe procedure, presenting a low rate of iatrogenic injuries with a low degree of severity. In addition, using Micro-CT promoted a better visualization of the microvasculature that nourishes the first metatarsal head. We observed that a proximal distance of 25 mm from the most distal part of the first metatarsal head could be a safe place to finalize the Chevron osteotomy, minimizing the risk of injury to the blood supply of the first metatarsal head.

Category: Ankle; Trauma Introduction/ Purpose: Previous studies identified a link between increased hindfoot valgus and distal tibiofibular syndesmosis (DTFS) widening in patients with flatfoot deformity using foot-ankle offset (FAO). However, it is not known what the impact of 3D foot alignment is on the DTFS in the presence of a known syndesmotic injury, particularly in varus. Weight-bearing Computed Tomography (WBCT) has emerged as a highly precise tool for diagnosing deformities of the foot and ankle. Under weight-bearing, it is possible to precisely detect deviations in DTFS stability. The objective of this cadaveric study was to determine the relationship between hindfoot alignment, measured by FAO, and DTFS widening in specimens with complete DTFS ligamentous injury. We hypothesized that DTFS widening would be significantly greater in specimens with increased hindfoot valgus. Methods: Two WBCT scans of the foot and ankle were obtained for each of 17 matched pairs (34 legs) of through-knee cadaveric specimens in a radiolucent frame under 80lbs of load to simulate double legged stance, a baseline scan with intact syndesmotic ligaments and a second after surgical ligament sectioning. All syndesmotic ligaments were released through a direct lateral approach to the distal fibula. Models of the bones were created from scans using Disior Bonelogic. Distance mapping was used to evaluate DTFS widening over the entire DTFS interface, as well as the anterior/posterior sections, in the first 1cm, 3cm, and 5cm from the joint after injury. Post-injury distance maps were compared to the contralateral baseline normal scan as a control. FAO was measured post-injury and compared to the difference in DFTS widening between the injured leg and its contralateral, healthy control. Linear regression and Spearman’s correlations were used to evaluate relationships. Results: Significant correlations between hindfoot alignment and DTFS widening were identified at every level in the syndesmosis. The Spearman’s rho values for the entire DTFS interface at 1cm, 3cm, and 5cm were 0.393 (p = 0.0316), 0.458 (p = 0.0101), and 0.369 (p = 0.0446), respectively. Anterior Spearman’s rho values at 1cm and 3cm were 0.453 (p = 0.0119) and 0.420 (p = 0.0209), respectively. Inter-observer variability of the FAO measurements showed no statistical difference (p = 0.4248). Extremely varus FAO measurements (FAO < -10%) showed negligible changes in syndesmotic opening. Linear regression also demonstrates a positive trend. The R2 values for the entire interface at 1cm, 3cm, and 5cm were 0.127, 0.213, and 0.158. Anterior R2 values at 1cm and 1cm were 0.133 and 0.1583. Conclusion: In this cadaveric study, we confirmed our hypothesis showing that valgus FAO was correlated with syndesmosis opening from an uninjured to an injured site. These data are in accord with prior findings relating FAO and DTFS opening in flatfeet and additionally demonstrate a stronger positive trend in the presence of known injury with smaller changes in tibiofibular distances after injury for extreme varus alignments. This study provides important context to the clinically relevant comparison of contralateral feet. The trend in our data allows for predictable results for the degree of injury in patients with valgus foot alignment.

Category: Ankle; Sports Introduction/Purpose: A ligament-centered analysis is currently incorporated in the assessment of joint stability in malleolar fractures. Although several imaging tests are available, in the setting of acute isolated non-displaced posterior malleolar fractures Bartoníček/Rammelt types II and IV diagnosing syndesmotic instability remains challenging. The objective of this multi-center cross- sectional study was to evaluate the syndesmotic and fracture instability using conventional ankle CT with external rotation and dorsiflexion in the setting of acute, isolated non-displaced Bartoníček and Rammelt type II posterior malleolar fractures. Methods: Between March 2018 and September 2022, a consecutive sample of 123 individuals with an ankle sprain were assessed for eligibility. In total, 33 participants met the inclusion criteria. All participants underwent a CT scan (CTSM), comprising a first phase with the ankles in a neutral position, then a stress phase with the ankles in external rotation and dorsiflexion and semiflexed knees. Investigators used the patterns of ligament tear found at MRI and instability at CTSM to classify all participants into West Point grades I, IIA, IIB, or III. Mann-Whitney test was used to test the differences in the numerical variables between injured and uninjured syndesmoses. The Spearman correlation tested the strength of the association between the tibial joint surface involved in posterior malleolus fracture and syndesmotic instability. Results: In MRI reading parameters two patterns of syndesmotic ligament injury predominated. A completely torn AITF and IO ligaments and a completely torn AITF was combined with a partially torn IO. Regarding the deep layer of the deltoid ligament, participants were classified as normal, strained and partially torn. In CT scan reading parameters in the neutral phase, the median difference of 0.2 mm in d measurements between injured and uninjured syndesmoses was not statistically significant (P = 0.057). During the stress phase, the injured and uninjured syndesmoses had distinct behavior, and the 2.3 mm median difference for d measurement was statistically significant (P < 0.0001). Conclusion: The conventional computed tomography with external rotation and dorsiflexion represent a reproducible and accurate diagnostic option for the detection of syndesmosis instability and fracture instability in acute isolated posterior malleolar fractures Bartonícek and Rammelt type II.

Category: Lesser Toes; Midfoot/Forefoot Introduction/Purpose: Women wearing high heels for 20 years without Hallux valgus angle alterations make it debatable that causes Hallux valgus deformation. A recent systematic review determined that 4.13 ± 0.34 cm of heel height would improve foot weight-bearing . Wearing high heels would realign the foot, causing an inversion of the foot, which locked the navicular-cuneiform and cuneo-metatarsal joints rather than primarily rotate the metatarsophalangeal joint. Nowadays, weight-bearing scans could favor understanding the alignment mechanism involved in the foot and ankle with different shoe heights. Therefore, we aimed to determine the acute foot alignment in non-frequent HH users without Hallux valgus during stand posture. Here, we hypothesize that high heels studied by weight-bearing scans shows radiology changes linked to hindfoot alignment rather than primary forefoot rotation. Methods: This comparative cross-sectional study, participants were randomly submitted to a tridimensional weight-bearing CT. Foot alignment for barefoot and wearing custom high heels of 3, 6, and 9 cm. Forty-one feet from twenty-one participants (11 males and 10 females, aged 30.8 ± 8.9 years, and Body Mass Index 25.5 ± 2.0 m kg-2) were submitted to a tridimensional weight- bearing scan in barefoot and wearing high heels of 3, 6, and 9 cm. The inclusion criteria were: Aged between 20 and 50 years, and no regular wearing of heels.Participants were instructed to bear weight in their regular standing upright posture, dispensing the body weight uniformly between the lower limbs with the feet set at shoulder width. Declination talar, forefoot arch, foot ankle offset, 1st, 2nd, and 3rd metatarsophalangeal dorsiflexion, and metatarsal rotation and sesamoid rotation angles were compared with repeated measurement analysis and multiple comparisons as well as the raters intraclass coefficient. Results: When height increases, the declination talar angle decrease (p < 0.001), the foot ankle offset decreases (p < 0.001), the 1st, 2nd, and 3rd dorsiflexion angle increases (p < 0.001), and metatarsal rotation angle (p=0.696) and sesamoid rotation angles (p=0.649) did not change. The forefoot arch for 6 cm was higher than 3 cm (p < 0.001) and then 9 cm (p=0.001), and the forefoot arch for 9 cm was higher than 3 cm (p=0.049). Conclusion: The main finding was that increased forefoot arch, lower ankle offset, no metatarsal rotation angle, and no sesamoid rotation angle strongly suggest an acute primary hindfoot alignment adaptation mechanism rather than forefoot rotation with increase of heel heigth. The most critical mechanism combines the activation of the windlass mechanism together with a stiffer alignment of Hindfoot. Our interpretation here is supported by the lower FAO, and increased forefoot arch and metatarsophalangeal joints, giving insight into pathology foot deformation like Hallux valgus. Thus, our findings suggest that it is debatable that wearing high heels can trigger forefoot deformity,

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: To properly treat osteoarthritis-(OA) patients, a grading-system is used to diagnose the stage-of-the- disease. The current gold-standard system, which relies on plain-2D-radiographs, is subjective, categorical, and lacks reliability. Using WBCT-images, 3D-Hounsfield-Unit-(HU) algorithms have been developed to measure the intensity of each image voxel across the joint-space, highlighting transitions between cancellous/subchondral bone and joint-space. The purpose of this study was to analyze and define normal standard values of joint-space-width (JSW) in the four essential joints of the foot-and-ankle (tibiotalar (ankle), subtalar (ST), talonavicular (TN), and first-metatarsophalangeal- (MTP) -joints) using an objective computational WBCT-HU algorithm in healthy non-arthritic feet. We hypothesized that the measurements of JSW and HU distributions across each of the four-essential-joints of the foot-and-ankle would be significantly different from each other, respecting local anatomy and unique functional characteristics of each joint. Methods: Retrospective-comparative-study, we evaluated WBCT-scans of 30 healthy ankle-joints, 28 ST-joints, 26-TN joints, and 30 1st-MTP-joints of control volunteers with no radiographic signs of foot-and-ankle OA. For each-joint, we used dedicated software to define a volume-of-interest (VOI) cube centered on the joint space. Five HU linear search arrays were then defined within this 3D VOI perpendicular to the articular-surface of each-joint, including four projections in each quadrant, and one in the center of the VOI (Figure 1). Image intensity profiles were generated for each search array crossing the transition from cancellous- to-subchondral bone, across the joint-space, back to subchondral-and-cancellous-bone (Figure 2). This profile was used to calculate JSW and to measure HU contrast in the region. Comparisons between the JSW of each joint and within each-joint were accordingly performed using paired t-tests or paired Wilcoxon. Significance was considered for p-values < 0.05. Results: The median-value and 95%-Confidence-Intervals-(CI) for JSW were 4.07mm [CI:3.73–4.20] for the ankle-joint; 4.07mm [3.95–4.44] for the ST-joint; 3.24mm [3.19–3.46] for the TN-joint; and 3.70mm [3.64–4.12] for the 1st-MTP-joint. The TN JSW was significantly narrower than the JSW in the ankle (p=0.0007), ST (p < 0.0002), and 1st-MTP-joints (p=0.0034) (Figure-3). JSW- values were similar across the entire ankle, ST and 1st-MTP-joints. In the TN-joint, the dorsal aspect of the joint was found to be slightly but significantly wider-than the plantar-aspect (p < 0.001). Regarding HU-contrast, we found a progressive increase in the overall contrast from proximal-to-distal (p < 0.001), with a mean HU contrast-value and 95%-CI of respectively 71.8[67.3–76.3] for ankle, 92.4[87.8–97.1] for ST, 84.1[79.2–88.9] for TN, and 101.3[96.9 – 106.8] for 1st-MTP-joints. The only joints with similar HU-contrast were ST and TN. Conclusion: We utilized a novel WBCT-3D-HU measurement algorithm to assess the normal JSW and HU contrast of the four- essential mobile joints of the foot-and-ankle. We found the JSW to be similar (~4mm) in the ankle, ST, and 1st-MTP joints. The TN-joint however, demonstrated a significantly narrower JSW when compared to the other 3 joints. HU-contrast increased progressively from proximal-to-distal, being less prominent in the ankle, similarly increased in TN and ST, and maximum at the 1st-MTP joint. This study's joint characteristic normality data provide a foundation for future-work developing an objective WBCT-based 3D HU-algorithm staging-system for OA-disease-progression in the foot-and-ankle joints.

Category: Hindfoot; Other Introduction/Purpose: The use of bio-integrative implants in orthopedic surgery is growing exponentially. Advantages, such as reduced implant-related artifact production, lower removal rates, and superior bone interaction, have been advocated. However, while many biomechanical and histological reports could sustain its structural and biological properties, only some clinical studies were produced that could support its use. Therefore, this trial intended to determine the bio-integrative screws' capacity to reach the same clinical and radiographical outcomes of current metallic screws in calcaneus osteotomies. Our main hypothesis was that metallic and bio-integrative screws would not present differences when comparing bone healing and complications. Methods: This was a single center, in parallel groups, randomized non-inferiority clinical trial (NCT05018130) that included patients undergoing a calcaneal sliding osteotomy from November 2021 to January 2023. Patients were randomized in a 1 to 1 ratio by software in the metallic or bio-integrative groups, and allocation occurred after anesthesia was carried out. Surgeries were performed by a single surgeon respecting the same technique, using two canulated 4mm screws, either titanium or fiber, according to the treatment group. The primary outcome was determined by bone using weight-bearing computed tomography (WBCT) in the 6th postoperative week. At least 50% of bone trabeculae crossing the osteotomy site needed to be observed to be considered positive. Secondary outcomes included minor and major complications and bone healing, assessed in the 2nd, 4th, 6th, 12th, 24th, and 48th weeks of follow-up. Two assessors performed readings. Between-group differences were measured with ANOVA and chi-square tests. Results: After twenty-nine patients were assessed initially, 22 subjects were found eligible and included in the study. Groups were similar demographically (ps>0.37), with ten patients allocated to the bio-integrative and 12 to the metallic group. The mean follow- up was 31.64 weeks (min 6; max 48) with no losses through the endpoints. Considering WBCT bone healing at six weeks, the bio (80%) and the metallic (75%) groups had similar rates (p=0.58). At 12 weeks, bone healing was slightly higher in the bio-integrative group (100% vs. 92%; p=0.004). No major complications were observed. Minor complications were similar between groups (10% in bio; 16% in metallic; p=0.56) and composed of superficial infections (one bio, one metallic) and delayed wound healing (one metallic), all resolved by six weeks. Conclusion: Bio-integrative screws presented similar results to metallic screws when used in calcaneus osteotomies, considering bone healing and complications. No differences were found in a medium to long-term follow-up, and no major complications were reported. This non-inferiority clinical trial could contribute to the body of literature supporting the use of bio-integrative screws in clinical practice. Larger and longer trials are necessary to determine the superiority of any implant and its impact on orthopedic surgery.

Category: Hindfoot; Sports Introduction/Purpose: Insertional and non-insertional Achilles tendinopathy (AT) are prevalent diseases in the active, working-age population. Ultrasound (US) and magnetic resonance imaging (MRI) are frequently utilized in the assessment and grading of AT. Use of these imaging modalities are limited by operator interpretation/variability and costs, respectively. Also, these assessments are performed in the non-weight bearing positioning of the lower extremity, thus poorly evaluating the functional position of the loaded tendon. Validation of weight-bearing computed tomography (WBCT) for Achilles tendon imaging could provide a novel and functional means of quantifying tendon pathology. The study’s purposes were to: 1) Correlate Achilles tendon tissue structural findings when assessed by WBCT and US imaging, and 2) Compare WBCT Achilles tendon tissue changes between AT patients and controls. Methods: This was a prospective-comparative IRB-approved cohort study including 10 adults with AT (Age = 54.7 ± 10.3 years, BMI = 40.65 ± 10.07 kg/m 2 , 8F/2M), 10 age-matched controls (Age = 54.6 ± 11.33 years, BMI = 37.9 ± 9.55 kg/m 2 , 8F/2M), and 4 younger controls (Age = 32.25 ± 8.3 years, BMI = 24.32 ± 5.14 kg/m 2 , 2F/2M). WBCT scans (Curvebeam HiRise/PedCAT) and US imaging (Butterfly iQ+) of the Achilles tendon were collected. Tendons were manually segmented in WBCT images (3D Slicer software) and tendon thickness was measured at the maximum anterior-posterior (AP) diameter of the tendon (insertion and midportion regions). Radiodensity was quantified by the average Hounsfield Units (HU) of each tendon region and normalized to the radiodensity of each participant’s talus (segmented using Disior Bonelogic). US measures of the tendon thickness were similarly completed by independent observers who were blinded to the WBCT measurement. Intraclass correlation coefficient (ICC) assessed correlation between WBCT and US findings. Paired T-tests compared WBCT HU between patients and controls. P-values < 0.05 were considered significant. Results: There was excellent correlation (ICC= 0.83-0.94, Table 1) between WBCT and US imaging regarding tendon thickness, with WBCT overestimating thickness by only 0.27-0.55mm (4-9% of total tendon thickness). These findings could be explained by decreased US tendon thickness measurements secondary to the tendon’s compression by the US probe. WBCT imaging demonstrated a higher radiodensity (HU) within the Achilles tendon (for both insertion and midportion regions) in AT patients when compared to controls (Table 2), with p-values of 0.009 and 0.001 for insertional and midportion regions, respectively. Findings are consistent with tendinopathic differentiation of the Achilles tendon substance in the AT patients. Color-coded maps demonstrating HU distributions across the Achilles tendon were created to facilitate interpretation of tissue characteristics (Fig. 1). Conclusion: In this prospective, comparative, and controlled study, we observed a high correlation between US and WBCT imaging in the assessment of Achilles tendon thickness in AT patients and controls. We also found that WBCT HU distribution in the Achilles tendon was significantly increased in the AT patients when compared to controls. Findings are likely explained by tendinopathic tissue changes in the diseased tendons, potentially related to the well-known chondroid metaplasia observed in Achilles tendinopathy pathological process. WBCT imaging and color-coded maps can represent a promising tool in the assessment of AT patients.

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: Flattening of the longitudinal arch of the foot (Flatfoot) can represent a normal spectrum of foot morphology and alignment. The issue comes when the foot is collapsing progressively, what is now termed Progressive Collapsing Foot Deformity (PCFD). Literature on asymptomatic flatfoot is scarce since asymptomatic patients do not seek medical attention. Alignment differences between asymptomatic flatfoot and PCFD have not been established and might represent a key-step in understanding predictors of PCFD. The objective of this prospective study was to compare established PCFD measures in a cohort of asymptomatic flatfoot, PCFD patients and healthy controls. We hypothesized that asymptomatic flatfeet alignment would differ from both symptomatic PCFD patients and healthy controls. Methods: In this prospective comparative study, patients with asymptomatic flatfeet were recruited to undergo a weight-bearing CT (WBCT) scan. This cohort (22 feet, 10 males, 12 females) was compared to two other prospective cohorts (22 symptomatic PCFD and 22 healthy controls). Along with demographic data, PCFD measurements performed include Foot and Ankle Offset (FAO), Forefoot Arch Angle (FAA), Middle Facet Uncoverage, and the Transverse Arch Plantar (TAP) angle. Normality of variables was assessed using the Shapiro-Wilk test. Chi-squared or analysis of variance (ANOVA) test was performed to compare each parameter between the three groups. A post-hoc Bonferroni test was then performed to assess significance between each group pairing. P-values of >0.05 were considered significant. Results: All three groups were comparable on BMI (p=0.10), Age (p=0.75) and Gender (p=0.78). All measurements taken differed significantly between the symptomatic PCFD and healthy controls (Table 1). FAO was significantly different between controls vs asymptomatic (p < 0.001) and asymptomatic vs symptomatic (p < 0.001). FAA was also significantly different between asymptomatic and both symptomatic (p=0.001) and control groups (p=0.001). Middle facet uncoverage differed between the asymptomatic and control group (p=0.001) but the asymptomatic and symptomatic group were similar (p=0.106). While the TAP angle was significantly different between asymptotic and symptomatic groups (p=0.013), the asymptomatic and control groups failed to reach significance (p=0.061) (Table 1). On average, deformity measurements for asymptomatic flatfeet were in between the values for healthy controls and symptomatic PCFD (Figures 1-3). Conclusion: To our knowledge this is the first prospective study to compare healthy controls, asymptomatic flatfoot and symptomatic PCFD patients. We observed that asymptomatic flatfoot patients usually had measurements of PCFD that would fall in between normal alignment asymptomatic controls and symptomatic PCFD patients. Further, the asymptomatic group differed significantly from both other groups on every measure but two. Our data supports the idea that asymptomatic flatfoot should be considered a risk factor for Progressive Collapsing Foot Deformity. Our data can hopefully shine light in finding predictive markers for the development of PCFD.

Category: Bunion Introduction/Purpose: Three-dimensional (3D) Distance-Mapping (DM) and Coverage-Mapping (CM) use WBCT images to evaluate multiplanar elements of Hallux Valgus (HV), such as sesamoid subluxation, through analyzing joint space and joint coverage across entire bony interfaces. Previous methods have struggled to characterize sesamoid subluxation consistently, and the reliable assessment of these deformity patterns is essential in guiding HV treatment and impacts recurrence rates following correction. The objective was to (1) develop a 3D WBCT CM and DM algorithm to characterize the surface interaction of the 1st metatarsophalangeal-joint (MTPJ) and metatarsal-sesamoid joints in HV patients and controls (2) correlate DM and CM measurements with WBCT semi-automatic angular measurements in HV patients and controls (3) correlate DM, CM, and angular measurements with Visual Analog Scale (VAS) scores in HV patients. Methods: Retrospective case-control study assessing HV patients. 51-feet with HV who underwent a WBCT of the affected foot and 54-feet were included. Semi-automatic segmentation protocol extracted bone models, which were analyzed with specialized software. The 1st-MTPJ surface was divided into two-by-two grids to provide a more detailed analysis. Distance measurements obtained were used to create color-coded distance maps. Blue color represented expected distances in joint interaction (1 to 5 mm), red or yellow color represented arthritis or impingement (0 to 1mm), and pink color represented subluxation (>5mm). Further, color-coded coverage maps highlighted areas of relative coverage ( < 5mm) or uncoverage (>5mm) contrasting areas with normal joint interaction or subluxation (Figure). Pearson’s correlations were used to describe association between intraarticular distances, or JSW (joint space width), and coverage measurements with the following: intermetatarsal angle (IMA), Hallux-Valgus- Angle (HVA), Distal-Metatarsal-Articulation-Angle (DMAA), Visual-Analog-Scale (VAS), and Body-Mass-Index (BMI). P-values less than 0.05 were statistically significant. Results: Interobserver reliability was high for 1st-metatarsal-head (ICC 0.846,p < 0.001), medial-sesamoid-articulation (ICC 0.854,p < 0.001), and lateral-sesamoid-articulation (ICC 0.832,p < 0.001). HV patients demonstrated significantly decreased coverage in comparison to controls (42.7% vs. 50.1%,p < 0.001) and a relative decrease in 1st-MTPJ-coverage (-14.7%,p < 0.001) in comparison to controls. In HV, articular coverage was higher in patients for the plantar lateral quadrant (HV 88.6% vs. 83.0% Controls,p=0.0002) and decreased in dorsal-medial (HV 8.8% vs. 18.7% Controls,p < 0.0001) and plantar-medial quadrants. (HV 46.2% vs. 78.8% Controls,p < 0.0001). Significantly decreased coverage was observed in HV-patients in both the medial sesamoid- articulation (HV 31.1% vs. 54.4%, p< 0.0001) and lateral sesamoid-articulation (HV 22.6% vs. 46.0%,p < 0.0001). Correlations between the first-metatarsal-head distance/coverage measurements and BMI, pre-op VAS, IMA, HVA, and DMAA are summarized in figure. Conclusion: We developed a quantifiable WBCT distance and coverage map algorithm to assess 3D-joint-interaction, joint- coverage, and subluxation in patients with HV. We observed significant subluxation of the 1st-MTPJ in patients with HV when compared to controls, as well as significant subluxation of the metatarsal-sesamoid joint at the medial and lateral sesamoid-joints, with an apparent medial and dorsal deviation of the first-metatarsal, lateral and plantar deviation of the proximal-hallux-phalanx and Lateral subluxation of the sesamoids. Increased coverage of the 1st-metatarsal-head was associated with decreased IMA and DMAA. However, we found no significant correlation between the Visual-Analogue-Scale-(VAS) and DM, CM, and semi-automatic measurements.

Category: Other; Hindfoot Introduction/Purpose: Clubfoot deformity (CFD) is one of the most common congenital deformities of the foot and ankle and is characterized by different severities of foot equinus, cavus, varus, and adduction. The gold-standard treatment is the Ponseti technique, characterized by serial casting and an Achilles tenotomy. Few studies have assessed long-term outcomes of this treatment, and none have utilized three-dimensional (3D) weightbearing analysis of residual CFD. The goals of this study were to elucidate residual 3D foot deformities in CFD patients treated with the Ponseti technique and to compare them with healthy controls. We also aimed to assess how these deformities influenced patient-reported outcomes (PROs). We hypothesized that significant residual deformities would be observed in CFD patients and that these deformities would negatively impact PROs. Methods: IRB-approved, prospective, comparative, and controlled study. We recruited 37 CFD patients (57 feet) treated with the Ponseti technique that had no additional foot and ankle surgical procedures. We also included 14 healthy control volunteers (28 feet) with no history of foot/ankle injuries/deformities. All patients underwent WBCT imaging (CurveBeam, HiRise). Tarsal bones were semi-automatically segmented (Bonelogic ® , Disior), and several automatic measurements assessing cavus, varus, adductus, and overall 3D deformity (Foot and Ankle Offset – FAO) were performed. Measurements were then correlated with PROs, which included Visual Analogue Scale for pain, PROMIS general health, PROMIS physical function and pain interference, pain catastrophizing scale (PCS), and European Foot and Ankle Society (EFAS) score. Paired T-tests or Paired Wilcoxon were utilized to compare measurements between CFD patients and controls, depending on normality distribution. A multivariate regression analysis assessed the relationship between residual deformities and PROs in CFD patients. P-values < 0.05 were considered significant. Results: No significant overall residual 3D-deformity was found, with similar FAO measurements in CFD and controls (respectively, 2.63% and 3.2%/P=0.58). Slight cavus overcorrection was observed in CFD, with sagittal plane talus-first metatarsal angle of -0.12° versus -5.2o (p=0.04) and calcaneal inclination angle of 13.01° versus 21.5°, respectively. Varus under-correction was identified in CFD patients, with decreased sagittal and axial talocalcaneal angles (44.3o vs. 57.5o/p < 0.0001 and 17.7o vs. 25.78o/p=0.0012, respectively). Similarly, adductus under-correction was observed in CFD, with talonavicular coverage angle 18.63o vs. 29.19o (p < 0.0001). In the multivariate regression analysis, cavus overcorrection (sagittal talus-first metatarsal angle) was the only deformity influencing VAS (R2=0.19/P=0.02) and EFAS-Scores (R2=0.27/p=0.002). Residual varus deformity (sagittal plane talocalcaneal angle) was the only deformity influencing PROMIS Pain Interference (R2=0.14/p=0.038) and Physical Function (R2=0.32/p=0.0007). Conclusion: This study highlights the efficacy of the Ponseti technique in treating the overall 3D foot and ankle deformity in CFD patients, realigning the ankle joint and the weightbearing foot tripod. However, residual CFD components were identified, including overcorrection of the cavus and under-correction of the adductus and varus deformities. Overcorrection of the cavus negatively influenced VAS pain and EFAS scores, and under-correction of the varus negatively influenced PROMIS scores. The results of this study could potentially guide CFD treatment with the Ponseti technique, with focus on improved correction of the varus and avoidance of overcorrection of the cavus deformities.

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux valgus (HV) and progressive collapsing foot deformity (PCFD) are very common foot and ankle conditions in the adult population. Both could potentially disrupt the tripod construct of the foot which leads to chronic pain and arthritis. Several procedures were described to address HV deformity depending on deformity characteristics. PCFD could alter the management plan for HV if they occur simultaneously. The aim of this study was to detect the prevalence of PCFD in HV patients and study the frequency of individual PCFD classes. Methods: In this retrospective IRB approved study, patients > 18 years old who were evaluated for symptomatic hallux valgus and had a weight bearing computed tomography (WBCT) imaging were included. Patients were considered for further analysis if they have a hallux valgus angle (HVA) > 15° or inter-metatarsal angle (IMA) > 9°. All relevant demographic data were extracted. Two fellowship trained foot and ankle orthopaedic surgeon measured the following parameters: foot and ankle offset (FAO%) (Class A), talo-navicular coverage angle (TNCA) (Class B), Meary’s angle (Class C) and middle facet subluxation (MFS%) (Class D). Cases that showed FAO% > 4.6% and MFS% > 28.7% were diagnosed as PCFD. The prevalence of PCFD classes (A,B,C and D) was calculated using threshold values for its respective radiographic marker. Descriptive statistics were performed. Results: Thirty-four cases were included. 16 cases were females (46.06%) and 16 (46.06%) were right side. The average age was 52.51 years (SD ± 17.75), the average BMI was 30.14 (SD ± 7.15). The average HVA was 26.82 (SD ± 9.98) and the average IMA was 15.41 (SD ± 3.53). 13 patients (38.24%) had MFS% and FAO% above the threshold values. The average FAO was 4.75% (SD ± 4.92) and the average MFS was 29.17% (SD ± 15.89). Prevalence of Class A (FAO%) was 20 (58.82%), Class B (TNCA) was 12 (35.29%), Class C (Meary’s angle) was 15 (44.12%) and Class D (MFS%) was 16 (47.06%). Conclusion: Progressive collapsing foot deformity is prevalent in the hallux valgus population (38.24%). Class C which indicates medial column instability was prevalent in 44.12% of the cases. Given this high prevalence of PCFD, we believe that in addition to the classic hallux valgus parameters, PCFD classes evaluation could favor a surgical approach over another such as first tarsometatarsal joint procedures over isolated distal first metatarsal procedures to correct the HV deformity and simultaneously halt PCFD progression.

Category: Hindfoot Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a complex three-dimensional foot deformity that is characterized, in part, by peritalar subluxation (PTS). The subtalar joint has been analyzed in PCFD using distance mapping as a measure of subfibular impingement (Figure 1). However, the progression of PCFD from healthy to asymptomatic to symptomatic and painful, specifically within the subtalar joint, is largely unknown. Therefore, investigating asymptomatic PCFD may offer clinical insight into both the pathology of PCFD within the subtalar joint and how the disease progresses. The objective of this study was to use a three-dimensional distance mapping algorithm of the subtalar joint for asymptomatic PCFD patients to describe and compare this stage of the deformity with a previously described cohort of symptomatic PCFD patients and healthy controls. Methods: In this prospective comparative study, patients with asymptomatic flatfeet were recruited to undergo a weight-bearing CT (WBCT) scan. This cohort (20 feet, 8 male, 12 female) was compared to a previously described cohort of both control (n=10, 4 male, 6 female) and symptomatic PCFD (n=20, 8 male, 12 female). Using a commercially available software package (Disior Bonelogic), models of the talus and calcaneus were created and analyzed. Distance mapping was then used to measure the distance along the normal direction of vectors projected from the calcaneal subchondral surface to the opposing talar surface. In this manner, the subtalar joint was objectively measured across the entire peritalar surface, including articular and nonarticular regions (Figure 1). Mean distances over the described articulations of the subtalar joint were compared using an analysis of variance (ANOVA) test to compare each parameter between the three groups. Results: Regarding mean distance values, the asymptomatic group was significantly higher than symptomatic measures in 10/13 articular surfaces and 3/4 sinus tarsi regions. Asymptomatic distances were also significantly greater than control measures in 11/13 articular surfaces (Table 1, Table 2) but were smaller and without significance in the sinus tarsi region. (Table 3). When looking at the sinus tarsi as a whole, asymptomatic distances (mean 3.21mm) were greater than both control (mean 2.73mm, p=0.01,) and symptomatic distances (mean 2.63, p=0.002) (Table 1). More specifically, asymptomatic distances were different than both symptomatic and control distances in the anteromedial, posteromedial and posterolateral regions of the sinus tarsi (Table 3). Conclusion: To our knowledge, this is the first study to examine the asymptomatic flatfoot within the subtalar joint. Asymptomatic distances were found to be largely greater than both symptomatic and control distances. This suggests that the bones are unstable and moving in patients who have flatfeet but no symptoms. When PTS, in an unstable asymptomatic foot, produces sinus tarsi impingement, that may be the trigger to further collapse and subsequent pain. Our data supports the idea that asymptomatic flatfoot should be considered a risk for progression to PCFD and represents a step toward finding predictors for development painful flatfoot.

Category: Bunion Introduction/Purpose: The original fixation for minimally invasive Chevron-Akin ( MICA) was described with two screws: a proximal screw reaching two cortices before fixing the metatarsal head and a distal parallel screw that can reach only one cortical before fixing the head. Despite this, some authors questioned the need for two screws and were able to reproduce good results from this technique using only one screw to fix the osteotomy. Notably, no biomechanical studies evaluate this osteotomy's most stable and safe fixation. This work aims to perform a biomechanical analysis based on finite element analysis (FEM) to compare different MICA fixation configurations using screws. Our hypothesis is that the fixation of the original technique with two screws is the safest. Methods: A Three-dimensional (3D) virtual model of a foot computer tomography (CT) image was made using the Rhinoceros™ program. The element finite analysis was performed with the SimLab™ program using the Optistruct solver. From these 3D virtual models, an extracapsular chevron osteotomy with 130 degrees with 70% of lateral translation was done and fixated. Five internal fixation configurations with screws were used for fixation of MICA and assessed by FEM -: original MICA fixation with 2 screws, 2 intramedullary screws, 2 bicortical screws, 01 intramedullary screw, and 01 bicortical screw. The simulated 150 N and 300 N loads were applied to the middle foot. The FEM evaluated the total and localized displacements of the osteotomy site. For the analysis of stresses, the variables maximum principal (traction) and minimum principal (compression) were used. The equivalent von Mises stress (VMS -S) was used for the metallic implants and for the bone (VMS -O). Results: The classical fixation for MICA showed the lowest values for total and localized displacement, minimum and maximum total stress, and VMS-S and VMS-o in both conditions( 150 and 300 N). The localized displacement was statistically lower for MICA screws compared to the other fixation configurations (p < 0.05) The maximum total stress was statistically lower for MICA screws compared to the other fixation configurations (p < 0.05) Conclusion: The classical fixation for MICA yields better results in terms of total and localized displacement, minimum and maximum total stress, and VMS in both conditions. These results demonstrate that the classical fixation for MICA described in the original technique is biomechanically the most efficient and safe.

Category: Other; Hindfoot Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a complex three-dimensional (3D) deformity where adjacent structures may adopt subtle differences in positioning that result in increased contact or subluxation. Recent studies have highlighted the need for and utility of 3D analyses in PCFD using weightbearing CT (WBCT) and bone segmentation. Beyond the limitations of triplanar imaging, 3D distance and coverage mapping analyses have further highlighted key regional differences like sinus tarsi narrowing ahead of impingement and early middle facet uncoverage ahead of collapse. However, these analyses rely upon manual identification of subregions hindering the utility of 3D mapping clinically. The objective of this study was to compare an automated selection process with manual selections in the context of subtalar regional distance and coverage maps in PCFD. Methods: In this IRB-approved retrospective study, WBCT data of 20 consecutive patients with flexible PCFD and 10 controls were analyzed. Subregions of the peritalar surface (middle and posterior facets of the calcaneus and talus; sinus tarsi area) were manually selected by two experts on manually generated bone surfaces of all 30 feet. An automated algorithm for selecting coverage area was applied to identify the same regions on the semi-automatically generated bones (Figure). A 3D distance mapping (DM) technique was used to create coverage maps (CMs) across the entire peritalar surface where areas with distances less than 4mm were defined as covered. DM and CM percentages were compared using intra-class correlations and t-tests between PCFD and control groups. The Sørensen–Dice index, or Dice coefficient, was used for comparisons of selections on the semi-automated surfaces to evaluate reproducibility of expert selections. Results: The automated process produced identical selections resulting in perfect intra-method ICCs of 1.00 for all regions and Dice coefficients of 1.00. The average Dice coefficient for all manual selections was 0.903 (range: 0.865-0.935) indicating that observers were able to reliably select the same regions with 90% overlap. When assessing reliability of manual selections, intra- observer ICCs ranged from 0.41-0.92 while inter-observer ICCs ranged from 0.47-0.99 were found. Despite strong significant correlations, average coverage was significantly lower in the sinus tarsi region of the automated selections vs the manual selections (34.3±16.8% vs 23.1±12.7%, p< 0.005). However, mean distances in each region were not significantly different in the middle facet or the sinus tarsi regions (p=0.323, p=0.095, respectively). Conclusion: Understanding of the complex 3D deformities that constitute PCFD requires sensitive and reproducible measures. Fully automated 3D assessments of coverage and bone relations can help improve understanding these deformities aiding in diagnosis, staging, and objective evaluation of treatment effects. Prior work with this method has specifically identified the middle facet and sinus tarsi regions as being of particular importance. Compared to manual selections, these regions were well identified by the automated process. This represents a major step toward viable use of fully automated 3D coverage and distance mapping when evaluating PCFD patients.

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: The current classification system of progressive collapsing foot deformity (PCFD) is comprised of 5 possible classes. PCFD is understood to be a complex, three-dimensional deformity occurring in many regions along the foot and ankle. The question remains whether a deformity in one area impacts other areas. The objective of this study is to assess how each one of the classes is influenced by other classes by evaluating each associated angular measurement. We hypothesized that positive and linear correlations would occur for each class with at least one other class and that this influence would be high. Methods: We retrospectively assessed weight-bearing computed tomography (WBCT) measurements of 32 feet with PCFD diagnosis. The classes and their associated radiographic measurements were defined as follows: class A (hindfoot valgus) measured by the hindfoot moment arm (HMA), class B (midfoot abduction) measured by the talonavicular coverage angle (TNCA), class C (medial column instability) measured by Meary’s angle, class D (peritalar subluxation) measured by the medial facet uncoverage (MFU), and class E (ankle valgus) measured using the talar tilt angle (TTA). Multivariate analyses were completed comparing each class measurement to the other classes. A p-value < 0.05 was considered significant. Results: Class A showed a substantial positive correlation with class C (ρ=0.71; R2=0.576; p 0.001). Class B was substantially correlated with class D (ρ=0.74; R2=0.613; p 0.001). Class C showed a substantial positive correlation with class A (ρ=0.71; R2=0.576; p 0.001) and class D (ρ=0.75; R2=0.559; p 0.001). Class D showed a substantial positive correlation with class B and class C (ρ=0.74; R2=0.613; p 0.001), (ρ=0.75; R2=0.559; p 0.001) respectively. Class E did not show correlation with class B, C, or D (ρ=0.24; R2=0.074; p=0.059), (ρ=0.17; R2=0.071; p=0.179), and (ρ=0.22; R2=0.022; p=0.082) respectively. The average values of each class radiographic markers are listed in Figure 1. Conclusion: This study was able to find relations between components of PCFD deformity with exception of ankle valgus deformity (Class E). Measurements associated with each class were influenced by others, and in some instances, with pronounced strength such as between class A and C as well as between Class B and D. Surgical procedures to address certain class deformities could indirectly address other classes as well, which ultimately decreases surgical procedures numbers or complexity. The presented data may support the notion that PCFD is a three-dimensional complex deformity and suggests a possible relation among its ostensibly independent features.

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: Progressive Collapsing Foot Deformity (PCFD) can present with independent deformities, characterized by five classes: hindfoot valgus (Class A), midfoot abduction (Class B), forefoot varus (Class C), Peritalar Subluxation (PTS) (Class D) and ankle valgus (Class E). Conservative treatment includes the use of corrective insoles and orthotics. Arch support inflatable Ankle-Foot orthoses (IAFO) can help control symptoms in PCFD patients. However, the ability of IAFOs to correct deformities in PCFD is unknown. The aim of this prospective comparative and controlled study was to assess the ability of arch support IAFOs to correct 3D overall PCFD alignment as well as the five different PCFD classes independently. We hypothesized that IAFOs would correct PCFD 3D overall alignment as well as the five independent classes of deformity. Methods: After IRB approval, we enrolled 24 symptomatic PCFD and 24 controls matched on age, sex, and BMI. Flexible PCFD patients and controls were scanned using Weight-Bearing CT (WBCT) with and without an arch support IAFO. The Foot and Ankle Offset (FAO) was used to assess the 3D foot overall alignment. We measured the Hindfoot moment arm (HMA, Class A), the Talonavicular coverage angle (TNCA, Class B), the Meary’s angle and medial cuneiform-to-floor distance (C1-floor) for the Class C and the middle facet uncoverage (MFunco, Class D). No Class E patients were included. Measurements were performed by two fellowship-trained surgeons. A power-analysis hypothesizing that IAFOs would be two times less efficient than the PCFD surgery in correcting the FAO, the requisite number of subjects was 24 per group. Data normality was assessed by Shapiro-Wilk test. Comparisons used normality based paired T-tests or paired-Wilcoxon tests. P-values < 0.05 were considered significant. Results: PCFD measurements performed in controls were all significantly less pronounced than unbraced PCFD patients, confirming the presence of collapse (ps < 0.0001). Comparing PCFD without and with IAFO, the FAO did not show significant improvement (respectively 6.6+/-3.7% vs 5.5+/-4.2%, p=0.101). The HMA (8.8+/-5.8 vs 8.1+/-5.8, p=0.66), the TNCA (24.2+/-10.6 vs 21.9+/-9.7, p=0.44) and the MFunco (37+/-12% vs 31+/-18%, p=0.17) also did not portray significant improvements when applying the IAFOs. The Meary’s angle (17.6+/-7.2 vs 10.8+/-7.3, p=0.002) and C1-floor (17.2+/-3.3mm vs 24.1+/-5.3mm, p< 0.001) were the only to improve significantly with use of IAFOs. When comparing braced PCFD and controls, the only measurement that improved to normal values, similar to controls, in braced PCFD was the C1-floor (24.1+/-5.3mm in PCFD with IAFO vs 25.7+/- 5.4mm in controls, p=0.31). Conclusion: In this prospective comparative and controlled study, we found that arch support IAFOs was not able to correct overall 3D deformity and most of the specific classes in PCFD. The orthosis did not improve hindfoot valgus (Class A), midfoot abduction (Class B) or peritalar subluxation (Class D) in PCFD. The only deformity pattern to improve with the use of IAFOs was the medial longitudinal arch height (Class C). These improvements were expected by the presence of the inflatable bladder of the IAFO on the plantar aspect of the foot, pushing the longitunal arch up but not correcting the entire PCFD.

Category: Ankle; Hindfoot Introduction/Purpose: Foot and Ankle Offset (FAO) is a clinically relevant measurement technique used to objectively evaluate the foot and ankle that has been shown to be reliable and validated in common mild foot deformities. It represents a measurement of the offset between the body weight vector and the ground reaction force vector, thus making it a biomechanically relevant measurement. However, FAO has not been validated in the setting of severe ankle deformity. The goal of this paper was to evaluate the validity of FAO measurements in the setting of severe foot and ankle deformities by utilizing a novel rotational FAO measurement technique to account for the deformity. Methods: This study included 57 feet (36 patients) that had a history of severe cavovarus deformity. Each participant received a Weightbearing CT (WBCT) scan that was then used to measure FAO. This measurement was taken three times, once using the traditional measurement technique and two additional times using a modified technique with a 15-day washout period between each measurement. This modified technique allowed for alignment of the talus in a neutral position through rotational correction in the axial, coronal, and sagittal planes to identify the most proximal and central point of the talus. Patients were broken into three groups based on the alignment of their foot and ankle. Normal alignment was defined as a FAO of 2.3% ± 2.9%, varus alignment as -11.6% ± 6.9%, and valgus alignment as 11.4% ± 5.7%. The measurements from the different techniques were compared to identify validity between them and the intraobserver reliability was assessed. Results: The mean traditional FAO was 2.37 ± 4.65% (95% CI=1.16–3.59) and modified FAO was 2.51 ± 4.6 (95% CI=1.3–3.71). The mean modified FAO values between the different alignment groups were found to be significantly different (p

Category: Other; Midfoot/Forefoot Introduction/Purpose: WBCT provides anatomical imaging that allows for extraction of metrics characterizing three-dimensional (3D) joint surface interactions. Three-dimensional (3D) Distance-Mapping (DM) and Coverage-Mapping (CM) use WBCT images to evaluate multiplanar elements of Hallux Rigidus (HR) through analyzing joint space and joint coverage across entire bony interfaces. Previous methods have struggled to characterize reliable assessment of these deformity patterns is essential in guiding HR treatment and impacts recurrence rates following correction. The objective was to (1) develop a 3D WBCT CM and DM algorithm to characterize the surface interaction of the 1st metatarsophalangeal-joint (MTPJ) and metatarsal-sesamoid joints (MTSJ) in HR patients and controls (2) correlate DM and CM with Body-Mass-Index (BMI), Coughlin and Shurnas classification- score (CGS), and pre-operative Visual-Analog-Scale (VAS). Methods: Retrospective case-control-study with Forty-one patients (20 HR and 21 controls). Semi-automatic segmentation protocol extracted bone models, which were analyzed with specialized-software. The 1st-MTPJ-surface was divided into two-by- two grids to provide a more detailed analysis. Distance measurements obtained were used to create color-coded distance maps. Blue color was represented expected distances in joint interaction (1 to 5 mm), red or yellow color represented arthritis or impingement (0 to 1mm), and pink color represented subluxation (>5mm). Further, color-coded coverage maps highlighted areas of relative coverage( < 5mm) or uncoverage(>5mm) contrasting areas with normal joint interaction or subluxation (Figure). Pearson correlations were computed between mapping metrics and the following for HR patients: Body-Mass-Index (BMI), Coughlin and Shurnas classification-score (CGS), and pre-operative Visual-Analog-Scale (VAS). Intraclass correlation coefficients (ICCs) were calculated to evaluate the interobserver reliability of the CCA selections and CGS obtained by two raters. One rater’s CCA selections and CGS were used for analysis. Results: HR patients displayed joint space narrowing at the first MTP joint when compared to controls (difference in means (DIM) = -11.8%,p=0.02). Quadrant analysis revealed first MTP joint space narrowing in HR patients for the plantar medial quadrant (DIM = -16.8%,p=0.002). Overall coverage in first MTPJ interaction for HR was increased, but not significant compared to controls (DIM = 9.2%,p=0.084). Quadrant analysis revealed increased coverage in first MTP joint surface-to-surface interaction for the plantar medial quadrant of the first metatarsal head (DIM = 13.7%,p=0.005) in HR patients when compared to controls. BMI was moderately positively correlated with mean first metatarsal head JSW (Joint space width) in HR patients (r=0.552,p=0.011). CGS was negatively correlated with mean first metatarsal head JSW for the HR cohort (r= -0.534,p=0.015). Conclusion: We developed a quantifiable WBCT distance and coverage map algorithm to assess 3D joint interaction, joint coverage, and subluxation in patients with HR. Compared to healthy controls, HR patients had increased joint space narrowing at the first metatarsal joint, both overall and specifically at the plantar medial aspect of the joint. Significantly increased coverage at the plantar medial quadrant was also observed in HR patients. Significant narrowing was not observed at the MTSJ. We found a significant correlation between Distance/Coverage mapping, Body-Mass-Index, and Coughlin and Shurnas classification score.

Category: Midfoot/Forefoot; Bunion Introduction/Purpose: First ray or medial column instability has been linked to the development of hallux valgus deformity (HVD), in part due to potential instability of Lisfranc joints and ligamentous complex. However, no study has assessed the 3D weight- bearing (WB) relationship of the Lisfranc complex in patients with confirmed hallux valgus, particularly at the articulating surface of the first tarsometatarsal joint and the second metatarsal and medial cuneiform space, commonly described as the primary region- of-interest of the Lisfranc complex. In this case-control study, we aimed to assesses WB 3D volumetric measurements in the entire Lisfranc joint, as well as in between first and second rays, and to compare HVD patients and controls. We hypothesized that volumes would be increased in HVD patients. Methods: In this IRB-approved, retrospective case-control study, we analyzed weight-bearing Computed Tomography (WBCT) data of 20 consecutive HVD patients and 20 healthy control patients. Using an automated segmentation method (DISIOR Bonelogic 2.0, Paragon28, USA), 3D volumetric models of the bones of the foot were created from WBCT data. Opposing articular spaces in the Lisfranc joint were selected on the STL models of the bones. Interarticular distance mapping was then performed to characterize the joint space width (JSW) in each of the articulations. Interarticular volume was then assessed using an area-weighted volume measurement. Areas of each triangle from the triangulated surface were multiplied by the JSW at each triangle. The sum of individual volumes was then normalized by the total surface area. The final volume was estimated using the product of the normalized summation and average area of both surfaces. Comparisons were performed with independent t-tests. P-Values < 0.05 were considered significant. Results: Estimates of volumetric assessment of the Lisfranc Complex were obtained using the automated method written in MATLAB. These outputs are reported in Table 1. As expected, the first tarsometatarsal joint volumes were the highest for both HVD patients and controls. No significant differences in the volumes were observed when comparing HVD patients and controls for any of the joints or spaces assessed (Figure). Particularly, no differences in the volumetric analysis of the first tarsometatarsal joint, 1-2 intercuneiform space or Lisfranc space (medial cuneiform-second metatarsal) were confirmed. Conclusion: In this retrospective case-control study, we hypothesized that joint volumes of the articulating surfaces and spaces-of- interest within the Lisfranc complex would be higher in HVD patients, consistent with first ray/medial column instability. Our study results demonstrated however no significant volume increases in Lisfranc joints or spaces assessed, particularly with no increases in the volumetric measurements at the first tarsometatarsal joint or between first and second rays. Even though our study could be underpowered to demonstrate potential differences between HVD and controls, our results support that no significant first ray instability in present when volumetric WBCT assessment is used.

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: The first-ray and the medial column play a crucial role in preserving the tripod of the foot. Changes to structural properties of the first-ray, along with collapse of the medial-longitudinal-arch, have been associated with hallux valgus (HV). Thus, restoring the first-ray plays an important role when correcting the mechanical function of the foot tripod in the setting of HV combined with medial-longitudinal-arch collapse. The LapiCotton technique combines the mechanical advantages of Cotton osteotomy and modified Lapidus procedures by maintaining the length of the first-ray and preserving the medial- longitudinal-arch by plantar inclination of the distal part of first-ray. The aim of this study was to evaluate the effectiveness of the LapiCotton procedure in correcting selected radiographic parameters in patients with combined VH with medial-longitudinal arch collapse. Methods: Preoperative and postoperative Weight Bearing CT (WBCT) scans were obtained from HV patients who underwent unilateral LapiCotton procedure. Postoperative scans were obtained roughly three months after the date of surgery. Semi- automatic measurements were applied to 22 WBCT images across a total of 11 patients enrolled into the study using the Disior ® Bonelogic ® Software. Measurements of the hallux valgus angle (HVA), meary sagittal measurement, and intermetatarsal angles were taken from preoperative and postoperative scans. These scans were then compared using intraclass correlation coefficients and paired t-tests to evaluate the efficacy of the Lapicotton technique in treating HV with P-valus < 0.05 being significant. Results: HVA was found to be significantly larger (p=.026) in the preoperational group (Mdn = 27.52) than the postoperational group (Mdn = 20). In addition, the Meary sagittal measurement was found to be significantly different between groups (p=.033), with a larger value seen in the preoperational group (Mdn = -14.28) compared to the post-operational group (Mdn = -11.15). It was also observed that the IMA was significantly larger (p=.003) in the preoperative group (Mdn = 15.68) compared to the postoperative group (Mdn = 11.26). The sesamoid rotation was found to be higher in the preoperative group (Mdn = -17.71) than the post operative group (Mdn = -24.98), however, these values were not significantly different from one another (p=.203). Conclusion: The LapiCotton procedure proved to be effective in correcting radiographic parameters in patients with HV combined with collapse of the medial longitudinal arch. Reliable correction of HV, along with correction of medial longitudinal arch collapse, was quantified based on semi-automated WBCT measurements of HVA, IMA and Meary angle. LapiCotton produced significantly different measurements for both HVA and IMA postoperatively, providing evidence that the LapiCotton procedure can successfully correct medial longitudinal arch collapse in patients with HV, as well as radiographically reduce the severity of the deformity.

Category: Hindfoot; Sports Introduction/Purpose: Zadek's procedure is a surgical option to treat insertional Achilles tendinopathy(IAT). This procedure consists of a closing wedge osteotomy of the calcaneus with biomechanical consequences. Great modifications in the hindfoot alignment can result in poor functional outcomes for athletes. Additionally, some authors stated that Zadek osteotomy is a good choice for patients with IAT associated with cavovarus foot. This study aims to analyze the hindfoot alignment and the parameters related to Haglund's syndrome after Zadek's osteotomy using a virtual surgical simulation by specific software. The authors hypothesize that the Zadek is an effective technique to decompress the Achilles tendon against the Haglund deformity without major modifications in the alignment. Methods: A total of 20 WBCT scans of patients with IAT were included. The WBCT images were run through the Foot & Ankle module of Disior's BonelogicTM software, creating a 3D virtual model. With this 3D model built into this software, 20 virtual Zadeck osteotomies standardized with a 10 mm resection wedge were performed using the virtual osteotomy module of Bonelogic®. The Calcaneal Inclination angle (sagittal view)7; Talocalcaneal angle (sagittal view)8; Talocalcaneal angle (axial view)8; Saltzman angle (45 degrees view)9; Saltzman angle (20 degrees view)9; Hindfoot moment arm angle;10 Hindfoot angle10; Fowler Philips angle11 and the calcaneal length7 were measured before and after the virtual osteotomy. These results were compared and statistically analyzed. Results: A virtual Zadek osteotomy was realized in 20 WBCT from patients with an insertional Achilles tendinopathy. Most of the patients were female, and the mean age was 55 years. There were significant statistical differences in the average of the calcaneal length (79 mm to 73 mm), Fowler Philips angle (57º to 43º), calcaneal pitch ( 24º to 20º ), sagittal talocalcaneal angle (55º to 47º ), and the hindfoot moment arm angle (20 º to 21,8º). The axial talocalcaneal angle, Saltzman view 45 º and 20 º, and Hindfoot moment arm showed subtle modifications. Conclusion: The virtual analysis of Zadek's osteotomy decreased the Fowler Philips angle, shortened the calcaneus, and modified the alignment in the sagittal view. It suggests that Zadek's procedure reduces the bone impingement with Achilles and the Achilles push. The effect of this osteotomy in Hindfoot Alignment was subtle, modifying only the sagittal plane.

Category: Sports; Arthroscopy Introduction/Purpose: Rotational ankle injuries are frequent and mostly benign. However, chronic pain and residual instability following an index rotational trauma can happen. The diagnostic elucidation of the pain source is challenging, with ligamentous insufficiency, osteochondral injuries, and impingement/arthritis representing potential causes for symptoms. The prevalence and pattern of the residual isolated or combined ligamentous ankle instability following rotational injuries are not entirely elucidated in the literature. In this prospective cohort study, we aimed to assess the frequency of combined ligamentous instability (lateral, medial, and syndesmotic) in patients with chronic ankle pain (>6 months) following rotational ankle injuries that failed conservative treatment and underwent surgical treatment. We also aimed to assess improvement in patient-reported outcomes (PROs) following treatment of the diagnosed conditions. Methods: IRB-approved prospective cohort study. We included patients with history of chronic pain (>6 months) following a rotational ankle injury, with clinical signs of combined ligamentous instability of at least two ligamentous complexes (lateral, medial, and syndesmotic), and that failed conservative treatment (>3 months). All patients underwent surgical treatment. Diagnostic arthroscopic assessment was performed. Syndesmotic instability was considered positive if a metallic sphere of 3mm could be inserted in the anterior syndesmotic space. Deep deltoid instability was confirmed with a “pass-through sign” when a 4.0mm shaver could be introduced in the medial gutter. Lateral ankle instability was confirmed with a positive rotatory drawer test under fluoroscopic assessment. Presence of isolated or combined ligamentous instability was noted and patients received appropriate open surgical treatment for the confirmed ligamentous insufficiencies. Presence of associated osteochondral injuries, peroneal pathology and anterior bony impingement was also recorded. PROs were collected pre-operatively and at most recent follow-up. Results: A total of 27 patients were included (9 males/18 females), mean age 35.9 years (range, 18-68) and average BMI 31.3kg/m 2 (CI, 28.1-34.5). Eighty-nine percent had ankle sprains, and 11% rotational ankle fractures treated conservatively. Intraoperative assessment demonstrated positive lateral, medial, and syndesmotic instability in respectively 96%, 81%, and 78% of the patients. Most common combined instabilities were: 59% multidirectional (all three complexes), 19% rotational (medial+lateral), 15% anterolateral (lateral+syndesmotic), and 4% anteromedial (medial+syndesmotic). Isolated lateral instability was present in only one patient (4%). Peroneal tendon pathology, osteochondral injuries and anterior bony impingement were found in respectively 67%, 19%, and 26% of the patients. The average postoperative follow-up was 22.2 months (3-39 months). Significant improvements in VAS (P=0.0024), PROMIS Pain Interference (p=0.024), and EFAS scores (p=0.022) were observed. Conclusion: In this prospective cohort study, combined multiligament instability was extremely frequent in patients with chronic pain following rotational ankle injuries. Ninety-six percent of patients had confirmed intraoperative instability of at least two of the three ankle ligamentous complexes. Multidirectional (lateral, medial, and syndesmotic) (49%), rotational (lateral and medial) (19%), and anterolateral (syndesmotic and lateral) (15%) instabilities were the most frequent injury patterns. Following ligamentous repair/reconstruction, significant improvements in PROs were observed at an average follow-up of 22-months. Our study highlights that the diagnosis of residual multiligament ankle instability should be considered in patients with chronic ankle pain following rotational injuries.

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Evidence in the literature suggests the negative effects of using High Heels (HH), becoming a challenge for clinicians and researchers since they are welcomed by women worldwide, mainly due to the subjective power of attractiveness given to them. Although some people blame HH as one of the causes of Hallux Valgus (HV), until now, there are no studies in the literature that effectively prove a cause-effect relationship between HH and HV. The objectives of this study are: (1) to analyze whether the increase in heel height can lead to HV and (2) to evaluate whether HV can increase in severity with increasing heels. We hypothesized that an increase in heel height could cause and increase the severity of HV deformity radiographically. Methods: Comparative cross-section4-one feet from twenty-one participants (11 males and 10 females, aged 30.8 ± 8.9 years, and with Body Mass Index 25.5 ± 2.0 m kg2) were recruited. HH shoes were designed for this study with three heights for each participant: 3, 6, and 9 cm. The inclusion criteria were: no regular wearing of heels. The exclusion criteria were: Hallux Valgus diagnosis and/or any orthopedic conditions that affect the Foot and Ankle joints. Hallux Valgus Angle (HVA), Intermetatarsal Angle (IMA), First-Metatarsal Phalangeal Angle, 1st-to-5th Intermetatarsal Angle, First Tarsometatarsal Angle (axial), Second tarsometatarsal angle (axial), Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle and, Foot Ankle Offset (FAO) were measurement using semiautomated software analysis. Multiple comparisons were performed (Bonferroni's for normal distributions and Wilcoxon test for no normal distributions) when there was a main effect on an outcome (p < 0.05). Results: With the increase in HH, we noticed a progressive increase in HVA (p < 0.001), IMA (p < 0.001), First-Metatarsal Phalangeal Angle (p < 0.001), First Tarsometatarsal Angle (axial) (p < 0.001), and the Second tarsometatarsal angle (axial) (p < 0.001). The Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle, and Foot Ankle Offset (FAO) had hindfoot varus behavior. When we stratified the groups and compared them, we noticed that an increase of 3 cm in heels slightly increased HVA and IMA (p > 0.05). However, heel increases above 6 cm significantly increased HVA and IMA (p > 0.001). Based on Coughlin's classification, a 3 cm heel increase promoted a mild HV, and increases above 6 cm caused a moderate HV. Conclusion: Based on data from our study with patients without Hallux Valgus through analysis with WBCT versus High Heels, we conclude that increasing heel height can radiographically lead to Hallux Valgus deformity and progressively increase the severity. High heels above 6 cm can lead to radiographically moderate Hallux Valgus. These findings may be an essential step toward a better understanding the effects of increasing high heels on Hallux Valgus pathology. More studies are needed to support this data clinically.

Category: Hindfoot; Other Introduction/Purpose: Treatment of Progressive Collapsing Foot Deformity (PCFD) is controversial and surgical procedures utilized usually depend on the type and rigidity of deformities present (PCFD classes and stages), degree of soft tissue involvement, and surgeon’s preference. Multiple surgical procedures are usually performed concomitantly to achieve adequate correction. Prospective data regarding the utilization of hindfoot joint-sparing reconstructive procedures in the treatment of flexible PCFD is scarce, and little is known about the influence of the different procedures utilized to treat PCFD in deformity correction and patient-reported outcomes (PROs). The objective of this prospective study was to evaluate the most used hindfoot joint-sparing procedures utilized by a single-surgeon to treat flexible PCFD, and the influence of the utilized procedures in deformity pattern corrections, and PROs. Methods: IRB-approved, prospective, and comparative cohort study. Adult PCFD patients with flexible deformity (stage 1), no history of surgical treatment, and that failed conservative treatment for >3-months were enrolled. Patients underwent surgical treatment by a single-surgeon. Patients were excluded if a hindfoot fusion procedure was needed intra-operatively to achieve correction. Types, numbers, and sizes of surgical procedures utilized were recorded. Weight-bearing CT (WBCT) measurements of overall 3D deformity, Classes A (hindfoot valgus), B (abduction), C (medial column instability), D (peritalar subluxation), and E (ankle valgus tilt) were assessed preoperatively, and at first 3-months WBCT. PROs were recorded preoperatively and at the most recent follow-up. Descriptive statistics were used to report the frequency of deformity and procedures utilized. Pre and postoperative measurements and PROs were compared with paired T-tests/Wilcoxon. Multivariate regression analysis was used to correlate procedures utilized with deformity correction and PROs. P-values of >0.05 were considered significant. Results: A total of 29 patients included (28 feet, 79%F, 21%M), mean age and BMI of respectively 47.6-years and 34kg/m 2 . Average number of procedures performed was five and mean follow-up was 19.1 months (range, 3 to 40). Frequency and sizes of medial displacement calcaneal osteotomy (MDCO), first ray plantarflexion procedure (Cotton/LapiCoton), and lateral column lengthening (LCL) procedures were, respectively: 100% (8.9mm displacement), 100% (66% Lapicotton/34% Cotton, 8.3mm wedge-opening) and 39% (6.8mm wedge-opening). Soft-tissue procedures performed: 83% Posterior tibial tendon (re-tensioning/FDL transfer/allograft reconstruction), 34% peroneal tendon (brevis-to-longus and brevis lengthening), 76% gastrocnemius-recession, 38% spring ligament (re-tensioning/reconstruction/augmentation) and 31% deltoid ligament (re- tensioning/reconstruction/augmentation). Significant improvement postoperatively was observed in all PCFD measurements performed and PROs (Figure). However, no direct correlation was found between procedures performed/measurement improvements and PROs. Conclusion: In this prospective comparative cohort study of flexible PCFD patients undergoing surgical treatment with hindfoot joint sparing surgical procedures, we observed significant postoperative improvement in all deformity patterns assessed (Classes A, B, C, and D) as well as PROs. MDCO and first ray plantarflexion procedures (Cotton or LapiCotton) were the most commonly utilized procedures and were performed in all cases. Even though deformity correction and PRO improvements were observed postoperatively, no direct correlation was observed between PROs and specific surgical procedures performed or deformity pattern corrections (PCFD classes).

Category: Ankle Arthritis; Ankle Introduction/Purpose: Ankle osteoarthritis is a degenerative joint disease characterized by the narrowing of the tibiotalar joint space and in late stages, eventual tibiotalar contact and subchondral bone loss. Traditional methods of assessing changes in the joint space (such as assessment on 2D radiographs) are subjective and do not fully consider the three-dimensional nature of articular surfaces. Weight-bearing CT (WBCT) provides a unique perspective by placing the joints of the lower extremity in a loaded, functional position, and may help to better quantify changes in joint space. Determining the presence and progression of ankle arthritis is difficult. It is our hope that novel 3D distance mapping technologies using images acquired from WBCT may assist with the detection and characterization of progression of ankle osteoarthritis. Methods: In this IRB-approved, retrospective case-control study, we analyzed WBCT data of 9 ankle osteoarthritis patients and 20 healthy controls. Patients included in this study had no identifiable talar tilt. Segmentations were created using an automated segmentation software package (DISIOR Bonelogic 2.0) Principal component analysis was used to divide the talar dome into nine subregions. The articular facet of the medial malleolus was also analyzed. We used 3D distance mapping to objectively measure joint space width across the tibiotalar joint and assessed changes in distance in each of the nine subregions of the talar dome articular surface. Overall mean distances for each subregion analyzed were calculated. Comparisons between the control and ankle arthritis cases were performed with independent t-tests, assuming unequal variances. P-values < 0.05 were considered significant. Results: Changes in the mean distances are reported in the attached figure. The medial side of the talar experienced significant decreases in mean joint space width. The middle medial subregion experienced the largest decrease in mean joint space width with a reduction of 35% when compared to controls (p = 0.017). Increases in joint space width were observed on the lateral aspect of the talar dome, However, these increases were not found to be significant. Conclusion: The purpose of this study is twofold: to quantify changes in joint space using 3D distance mapping technique and to evaluate the utility of a commercial automated segmentation software package. In this cohort, there was a significant decrease on the medial side of the talar dome – this change can be attributed to cartilage degeneration. To our knowledge, this is the first study to analyze changes in ankle osteoarthritis using a fully automated segmentation method. Automated segmentation and 3D distance mapping provide a useful tool for the quantification of osteoarthritis-associated joint space changes.

Category: Ankle; Sports Introduction/Purpose: Syndesmotic injuries and residual chronic subtle distal tibiofibular syndesmotic instability (DTFSI) are relatively common injuries, especially in athletes prone to suffering high ankle sprains. The diagnosis of subtle DTFSI remains challenging, with a high prevalence of false-negative results using conventional non-invasive clinical-radiographical diagnostic tools. The current gold standard for diagnosis, arthroscopy, is a surgical operation, which is invasive and, therefore, not ideal. Weightbearing Computed-Tomography (WBCT) has emerged as a possible dynamic non-invasive alternative diagnostic option, with proven high diagnostic accuracy for syndesmotic incisura area measurements in major DTFSI. Our study aimed to assess the capability of semiautomatic weight-bearing computed tomography (WBCT) syndesmotic incisura area in diagnosing subtle chronic syndesmotic instability. Methods: In this diagnostic case-control study, patients with suspected unilateral chronic subtle DTFSI underwent bilateral standing weight-bearing CT (WBCT) before surgical treatment. All patients had gold-standard arthroscopic assessment for DTFSI, introducing a 3mm diameter arthroscopic sphere into the syndesmotic incisura for diagnosis. Bilateral syndesmotic incisura areas were measured 10mm proximally to the apex of the distal tibia articular dome using a semiautomatic measurement algorithm. Two tangent lines marked the anterior and posterior borders of the syndesmotic incisura to the anterior and posterior edges of the distal tibia and fibula. Once borders were marked, the incisura area was automatically calculated by the software based on a Hounsfield units (HU) contrast algorithm. A HU threshold of 200HU was utilized. Measurements were done independently by two fellowship-trained readers. Comparisons between injured and control ankles were made using Student T-test or Wilcoxon, according to normality. Measurements' reliability was assessed with the Intraclass Correlation Coefficient (ICC). Results: From an initial sample of 32 patients, 20 patients (12 female) with arthroscopically confirmed DTFSI (11 right sides) with a mean age of 31.7 years (range 18 to 55 years) and a mean BMI of 30.35kg/m² (SD +/-8.29 kg/m²) were included in the study. All patients had a history of an old ankle sprain 6 to 182 months before the assessment, and athletic lesions were reported in 53% of the population. ICCs were above 0.98 for both intra and interobserver reliability. The average syndesmotic area was 96.91mm 2 (SD +/-27.9mm 2 ) in injured ankles compared to 84.61mm 2 (SD +/-26.9 mm 2 ) in uninjured ankles. The difference between injured and non-injured tibiofibular areas was 12.31mm 2 (95%CI: 9.04-15.58mm 2 ), which was shown statistically significant (p < 0.001; effect size: 1.43). Conclusion: In this case-control study, we assessed the accuracy of semiautomatic WBCT syndesmotic incisura area measurements in diagnosing subtle chronic DTFSI. We found an increased syndesmotic area in injured ankles that reached statistical significance. Due to the minimal differences between injured and uninjured contralateral ankles, larger cohorts would likely solidify this study's findings further. The use of external rotation stress, volumetric assessment, distance, and coverage maps could increase the diagnostic accuracy in DTFSI. However, automatic area measurements have a higher overall reproducibility and applicability in the clinical setting, which could help providers make therapeutic decisions.

Category: Midfoot/Forefoot; Bunion Introduction/Purpose: Interpositional arthroplasty (IPA) is a motion-preserving surgery in patients with advanced hallux rigidus. Literature displays several complications after the procedure including transfer metatarsalgia, cock-up deformity and infection. In a finite element model, shortening of the first metatarsal was associated with increased plantar pressure on lateral rays during gait. Additionally, there are reports of a positive correlation between first metatarsal shortening after hallux valgus surgery and transfer metatarsalgia of the second, third and fourth metatarsophalangeal joints. The goals of this study were to report the outcomes and complications of IPA using acellular dermal allograft (IPA-ADA) as well as study the changes in the length of the proximal phalanx of the hallux (P1) and the first metatarsal (M1) following the procedure. Methods: In this IRB-approved retrospective study, we assessed patients who underwent IPA-ADA in a single academic institute during the period 2019-2022. All patients’ demographic data, surgical details, complications, and patient-reported outcomes (PROs) were extracted. On standing conventional anteroposterior (AP) foot views, we measured the lengths of the first metatarsal (M1), the second metatarsal (M2), the proximal phalanx of the big toe (P1) and the entire length of the hallux (HX). The ratio of M1/M2 and P1/HX were calculated. The first metatarsophalangeal joint space was measured at the medial and lateral aspects of the joint on the AP view. All measurements were recorded pre-operatively, at six weeks follow-up and at the final follow-up. Descriptive statistics were performed, comparison between groups was performed using analysis of variance (ANOVA) or Kruskal Wallis test according to data normality. The Dunn-Bonferroni test was then performed for pairwise group comparisons.A p-value < 0.05 was considered significant. Results: Eleven patients were included, 9 being females (81.81%). Six were hallux rigidus Coughlin grade III (54.55%) and 5 were grade IV (45.45%). The average age was 59 years (SD±6.78) and the body mass index (BMI) was 26 (SD±4.79). At the final follow- up, there was significant shortening of the first ray in comparison to the pre-operative length evidenced by lower M1/M2 (82.63 SD±2.29 versus 75.42 SD±5.1; p=0.001) and P1/HX ratio 53.38 ± 2.29 versus 48.98 SD ± 7.92; p=0.001). Although there was no significant difference between M1/M2 at 6 weeks and at the final follow-up (p=0.716), there was a significant negative correlation between follow-up length and M1/M2 (r= -0.76, p=0.003). Follow-up was (19.95 months; range 3-39). Complications and PROs are listed in Figure 1. Conclusion: Interposition arthroplasty using dermal allograft for HR is associated with progressive shortening of the first ray at the level of the first metatarsal as well as the proximal phalanx. Although the study did show shortening of the first ray, the small sample size didn't allow for a correlation between this shortening and complications such as transfer metatarsalgia and cock-up toe deformity. The potential shortening should be considered in the selection of patients, particularly in the setting of an already short first metatarsal or when simultaneous Akin/Moberg osteotomy is planned.