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Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: Pes cavovarus (PC) is clinically identified as an elevated longitudinal arch. In the setting of Charcot-Marie-Tooth disease this often presents in more severe deformity due to muscular imbalance, however, pes cavus may also present idiopathically. The transverse arch (TA) is thought to play a critical role in foot stiffness and has been applied in progressive collapsing foot deformity (PCFD). This novel approach has never been applied to the pes cavus model. Therefore, the objectives of this study were to evaluate morphological differences in CMT PC and idiopathic PC including recently described measures of the transverse arch. We hypothesize that CMT PC will be more severe than idiopathic PC, as evidenced by preliminary underpowered data, and that CMT PC will have a more pronounced transverse arch. Methods: Weightbearing CT images were retrospectively evaluated in 32 CMT feet with pes cavus (CMT-PC) and 32 idiopathic pes cavus (I-PC) feet. Eleven two-dimensional (2D) measurements and four three-dimensional (3D) measurements were evaluated. Of these, a novel measurement termed the transverse arch plantar (TAP) angle, previously applied in PCFD, was used to assess the TA. (Figure 1a). Other measurements performed in the sagittal plane include calcaneal pitch, talus-first metatarsal angle, cuneiform-to-floor distance, cuneiform-to-skin distance, navicular-to-skin distance and navicular-to-floor distance. Axial measurements included talus first-metatarsal angle (Kite’s angle), and forefoot arch angle. Finally, 3D measurements consisted of foot and ankle offset (FAO), calcaneal offset, and hindfoot alignment angle. Results: Overall, the CMT-PC cohort demonstrated greater deformity for all measures. Specifically, the CMT-PC cohort showed a significantly greater cuneiform-to-floor distance (p=0.018), cuneiform-to-skin distance (p=0.022), Kite’s angle (p < 0.001) and forefoot arch angle (p=0.037) when compared to I-PC (Table 1) (Figure 1 b-c). Assessment of the TA demonstrated that the TAP angle is greater in CMT-PC than in I-PC with a mean angle of mean angle of 93.11° (SD 12.00) compared to 100.81° (SD 9.65) respectively (p=0.006). Patients with CMT-PC also showed a significantly higher TA at all locations measured. This includes a greater distance between the plantar first cuneiform and the plantar second metatarsal (p < 0.001), the first cuneiform and third metatarsal (p=0.005) and the first cuneiform and the fourth metatarsal (p=0.012) (Table 2) Conclusion: To the best of the author’s knowledge, this is the first study to investigate the transverse arch in the pes cavovarus population. The transverse arch as a whole, and each component of the transverse arch, were significantly more affected in CMT-PC than in I-PC. Further, all included measures were greater in CMT-PC than in I-PC including a significantly greater cuneiform height, Kite’s angle and forefoot arch angle. This suggests that not only do these two disease processes differ, but that the transverse arch is implicated in the development of pes cavovarus and should be investigated further. Figure: Two and three dimensional measurements included as well as example images in CMT and idiopathic pes cavus

Category: Bunion; Hindfoot Introduction/Purpose: Progressive collapsing foot deformity (PCFD) and Hallux Valgus (HV) are common foot and ankle pathologies, each associated with over-pronation. Although hindfoot pronation is known to potentially increase forefoot pronation, not all patients with PCFD ultimately develop HV deformity. This study aims to explore the structural differences in patients with PCFD, with and without HV deformities, using weight-bearing computed tomography (WBCT). We hypothesize that specific structural variations exist, which could potentially inform and enhance future therapeutic strategies and preventive measures for HV deformity in patients with PCFD. Methods: Adult PCFD patients underwent WBCT at our institution between May 2023 and December 2023 were included. Semi-automatically measured parameters include Meary angle (axial and sagittal), calcaneal inclination angle, hindfoot moment arm, hindfoot angle, axial talonavicular angle, intermetatarsal angle, HV angle were recorded. WBCT manual measurement include foot and ankle offset, angle between inferior facet of the talus and the ground (inftal-hor), angle between inferior and superior facets of the talus (inftal-suptal), angle between inferior facet of the talus and superior facet of the calcaneus (inftal-supcal), and forefoot arch angle. Additionally, using the ground as a reference, the coronal plane pronation of the navicular, medial cuneiform, first metatarsal base, and first metatarsal head were also recorded. HV deformity was defined as having a Hallux Valgus Angle (HVA) greater than 15 degrees. Pronation/valgus were defined as positive values. Results: Our study included 58 patients (72 feet), 33 feet with HV and 39 without HV. In the coronal plane, the PCFD with HV group exhibited higher inftal-suptal angle (p=0.001), and higher pronation of the first tarsal-metatarsal joint (p=0.006), first metatarsal bone(p=0.002), and first metatarsal head(p< 0.001). Additionally, this group also demonstrated higher navicular-cuneiform joint supination (p < 0.001). In axial plane, the axial talar-1st metatarsal angle higher in the PCFD without HV group (p=0.043). Nominal logistic regression analysis indicated parameters include 1st metatarsal head rotation (p< 0.001), medial cuneiform rotation(p< 0.001), inftal-suptal angle (p< 0.001), axial talar-1st metatarsal angle (p< 0.001), navicular rotation (p=0.007), first metatarsal base rotation (p=0.012), and inftal-hor angle (p=0.016) are significantly correlated with the presence of HV in PCFD patients. (R2 (U)=0.79) Conclusion: Our findings reveal distinct structural differences in PCFD patients with HV compared to those without, which corroborates our hypothesis. Significant correlations exist between HV presence and rotation of the navicular, medial cuneiform, first metatarsal base, and first metatarsal head. Talus morphology, including inftal-suptal and inftal-hor angles, also correlated with HV deformity. Talar-first metatarsal angle was the only traditional two-dimensional radiographic parameter that correlated with HV deformity. Based on our findings, PCFD patients displaying these features might need HV preventive measures. Prospective longitudinal studies or dynamic research may be required to further elucidate the relationships between these two deformities.

Category: Trauma; Sports Introduction/Purpose: Prior studies have shown the potential of a rigid fixation, such as a trans-syndesmotic screw, to produce tibiofibular malreduction. Flexible implants, although capable of allowing forgiveness in these situations, may not provide sufficient initial stability for all injury patterns. The purpose of this study is to assess the malreduction forgiveness of a two-phase syndesmotic device that is designed to transition from a rigid screw construct to a flexible suture-type device upon weightbearing. Methods: Below-knee cadaveric specimens were mounted in a radiolucent frame with a static axial load of 356N under four conditions: native ankle (control), syndesmotic instability (injured ), malreduced with two-phase syndesmotic device engaged (malreduced ), and post-disengagement of the two-phase device (disengaged). A lateral approach was used to destabilize the joint. The malreduction targets for each group were 5mm anterior displacement, 5mm posterior displacement, 15° of rotation, and over-compressed (140N) states. Fixation was performed with a single implant 20mm proximal to the joint. Weightbearing Computed Tomography (WBCT) scans were obtained for each condition. The device was manually disengaged to allow for semi-constrained motion of the syndesmosis, reproducing the release that would occur when a patient initiates weightbearing. Anatomic axes of the tibia and fibula were extracted from WBCT scans to calculate tibiofibular joint position with an established orthogonal joint coordinate system representation. Results were normalized to the control states and compared. Results: A total of 42 limbs were included (anterior=10, posterior=11, rotation=12, over-compression=9). Anterior and posterior malreduction specimens demonstrated 2.50mm (SD: ±1.37mm) and 5.04mm (SD: ±2.23mm) of average malreduction in the malreduced state. The disengaged device condition resulted in an average recovery of 1.79mm (95%CI: 0.72mm, 2.85mm; p=0.0034; 72% recovery) and 1.69mm (95%CI: 0.09mm, 3.28mm; p=0.0006; 33% recovery) toward the control position of the joint, for anterior and posterior malreduction, respectively. Rotational malreduction specimens demonstrated 2.44° (SD: ±2.09°) of average absolute rotational malreduction, with 1.98° (95%CI: -0.13°, 4.09°; p=0.0707; 81% recovery) of recovery. Over-compression specimens demonstrated an average medial translation of 0.89mm (SD: ±1.10mm), and the disengaged device condition had 0.74mm (95%CI: 0.05mm, 1.51mm; p=0.0128; 82% recovery) of joint pose recovery. Conclusion: In this cadaveric study, malreduction forgiveness using a two-phase syndesmotic implant that transitions from a rigid screw to a flexible device was tested. Using the computational methods described, overall syndesmotic malreduction and specific corrective changes in fibular malpositioning following disengagement from a rigid construct were noted. The results support the implant concept on malreduction recovery in multiple planes, potentially impacting the clinical management of syndesmotic injuries. Application of this implant and our study methodology to a clinical cohort of patients with syndesmotic instability is paramount to confirm our findings.

Category: Hindfoot; Ankle Introduction/Purpose: Having a flatfoot can be normal. Having a flatfoot that is getting worse is not normal. But how does that happen? What leads to symptoms? Those questions are yet to be answered in the literature. In this prospective comparative study, we recruited patients with asymptomatic flatfoot and controls with normal foot alignment and compared to patients with Progressive Collapsing Foot Deformity (PCFD). We hypothesized that measurements of foot deformity and collapse – Class A for hindfoot valgus, Class B for Midfoot/Forefoot abduction, and Class C for longitudinal arch collapse - would be progressively more pronounced in controls, asymptomatic flatfoot, and PCFD patients. However, only symptomatic PCFD patients would demonstrate signs of Peritalar Subluxation (PTS) or Class D deformity. Methods: In this IRB-approved study, we prospectively recruited adult volunteers with normal foot alignment and with flatfoot morphotype and no history of foot/ankle pain, major injury, or surgeries. We included a total of 88 controls (98 feet) and 66 asymptomatic flatfoot patients (132 feet), as well as a retrospective cohort of 306 symptomatic PCFD patients (311 feet). All patients underwent bilateral Weightbearing Computed Tomography (WBCT). Measurements of alignment and collapse were compared between the groups. Measurements included: Hindfoot Moment Arm (HMA) (Class A deformity); Talonavicular Coverage Angle (TCA) (Class B); Forefoot Arch Angle (FAA) (Class C); as well as distance and coverage maps of the sinus tarsi, anterior, middle, and posterior subtalar joint facets, as markers of PTS (Class D). Data was compared using paired T-tests/Wilcoxon. A multivariate nominal regression analysis and a partition predictive model were utilized to identify measurements influencing the presence of symptoms. P-values < 0.05 were considered significant. Results: Class A, B, and C measurements were significantly and progressively more pronounced in asymptomatic flatfoot and PCFD patients when compared to controls (p-values < 0.0001). However, PTS measurements were similar in control and asymptomatic patients and only significantly more pronounced in symptomatic PCFD patients. PCFD patients had respectively 12.7% and 14.3% less posterior and middle facets coverage and 19.6% increased coverage of the sinus tarsi when compared to asymptomatic flatfoot patients (P-values < 0.0001). Multivariate analysis demonstrated that posterior facet and sinus tarsi coverages, minimum sinus tarsi distances, FAA, and HMA were found to significantly influence the presence of symptoms (p < 0.0001). The partition predictive model demonstrated that minimum values of sinus tarsi distance lower than 1.9mm would lead to 89% chances of a patient having symptomatic PCFD. Conclusion: In this prospective comparative study, we aimed to investigate the differences between a normally aligned foot, an asymptomatic flatfoot, and a symptomatic Progressive Collapsing Foot Deformity, searching for drivers of symptoms. We found that when compared to controls, Class A (hindfoot valgus), B (midfoot/forefoot abduction), and C (arch collapse) measurements were progressively and significantly more pronounced in asymptomatic flatfoot and PCFD patients. However, Class D Deformity (Peritalar Subluxation), including sinus tarsi and subtalar joint coverage, was found to be similar in controls and asymptomatic flatfoot, but significantly more pronounced in PCFD patients, potentially representing the primary driver of symptoms.

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; 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: 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: 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: 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: 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: 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: 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.

Abstract A key element of the peritalar subluxation (PTS) seen in progressive collapsing foot deformity (PCFD) occurs through the transverse tarsal joint complex. However, the normal and pathological relations of these joints are not well understood. The objective of this study to compare Chopart articular coverages between PCFD patients and controls using weight-bearing computed tomography (WBCT). In this retrospective case control study, 20 patients with PCFD and 20 matched controls were evaluated. Distance and coverage mapping techniques were used to evaluate the talonavicular and calcaneocuboid interfaces. Principal axes were used to divide the talar head into 6 regions (medial/central/lateral and plantar/dorsal) and the calcaneocuboid interface into 4 regions. Repeated selections were performed to evaluate reliability of joint interface identification. Surface selections had high reliability with an ICC > 0.99. Talar head coverage decreases in plantarmedial and dorsalmedial (− 79%, p = 0.003 and − 77%, p = 0.00004) regions were seen with corresponding increases in plantarlateral and dorsolateral regions (30%, p = 0.0003 and 21%, p = 0.002) in PCFD. Calcaneocuboid coverage decreased in plantar and medial regions (− 12%, p = 0.006 and − 9%, p = 0.037) and increased in the lateral region (13%, p = 0.002). Significant subluxation occurs across the medial regions of the talar head and the plantar medial regions of the calcaneocuboid joint. Coverage and distance mapping provide a baseline for understanding Chopart joint changes in PCFD under full weightbearing conditions.

Abstract Artificial intelligence (AI) is looked upon nowadays as the potential major catalyst for the fourth industrial revolution. In the last decade, AI use in Orthopaedics increased approximately tenfold. Artificial intelligence helps with tracking activities, evaluating diagnostic images, predicting injury risk, and several other uses. Chat Generated Pre‐trained Transformer (ChatGPT), which is an AI‐chatbot, represents an extremely controversial topic in the academic community. The aim of this review article is to simplify the concept of AI and study the extent of AI use in Orthopaedics and sports medicine literature. Additionally, the article will also evaluate the role of ChatGPT in scientific research and publications. Level of evidence: Level V, letter to review.

Objective: This cadaveric pilot study was to develop a weight bearing computed tomography (WBCT) three-dimensional (3D) distance mapping algorithm that would allow for detection of syndesmotic instability. Methods: Pilot study, two cadaveric specimens. Syndesmotic instability was induced by release of all syndesmotic ligaments through a conventional lateral ankle approach. WBCT imaging under simulated weight bearing was acquired before and after syndesmotic destabilization. Syndesmotic incisura and ankle gutter distances were assessed using a 3D distance mapping WBCT algorithm. Results: We found increases in the overall mean syndesmotic distances in the injured syndesmosis when compared to pre-injury state, and color coded distance maps allowed easy interpretation of the syndesmotic widening following ligament sectioning and destabilization of the syndesmotic joint. Conclusion: The WBCT 3D distance mapping algorithm has the potential to allow detection of mild syndesmotic instability with a relatively ease of interpretation by using color-coded distance maps. Level of Evidence V; Cadaveric Study.

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Little is known about the intersesamoid crista in Hallux Valgus (HV). However, this structure directly interfaces with the sesamoids and surrounding soft tissues and might play an important role in HV deformity. Our primary objective was to compare the angulation between the crista and first metatarsal (M1) longitudinal axis in HV and controls. Our secondary objective was to assess its correlation with the Distal Metatarsal Articular Angle (DMAA). We hypothesized that the longitudinal axis of the crista will be deviated in valgus in HV and that its position will be correlated with the DMAA. Methods: This IRB approved retrospective case control study evaluated 9 HV and 8 controls matched on age, BMI, and gender. The DMAA was measured as initially described on X-Rays, and then on weight-bearing CT images using a previously validated technique including pronation correction of the M1 called 3d-DMAA. To identify the angle of the inter-sesamoid crista relative to the shaft of the 1st metatarsal, CT scans were semi-automatically segmented to create 3D models of the forefoot. The crista was selected in Geomagic Design X and the resulting STL models were imported into MATLAB for analysis. Principal component analysis was used to identify the direction of both the crista and the 1st metatarsal shaft. The crista-shaft angle is the angle between the directions of greatest variation. Normality was assessed using Shapiro-Wilk tests. Comparisons were made using Student T-tests for normal variables and Mann-Whitney for non-normals. Correlations were assessed using Pearson's coefficients. Results: The crista deviated from the 1st metatarsal shaft in valgus in all the cases (HV and controls). There was a significant increase in valgus deviation of the crista in HV compared to controls (respectively 14.4+/-8.7 degrees and 5.5+/-3.2 degrees; p=0.017). Mean DMAA were respectively 25.1+/-7.9 degrees in HV and 7.4+/-2.9 in controls (p

Category: Bunion; Hindfoot; Midfoot/Forefoot Introduction/Purpose: The presence of hyperpronation of the first metatarsal (M1) seems to have a clinically significant role in Hallux Valgus (HV). Some authors reported a decrease in recurrence rates after M1 hyperpronation correction in HV. However, when measuring the M1 head pronation relative to the ground, we are assessing and quantifying the aggregate coronal rotational profile of each bone and joint throughout the medial column. Therefore, we do not know the location of this hyperpronation. Moreover, studies showed a strong influence of the hindfoot alignment on coronal rotational measurements and Progressive Collapsing Foot Deformity (PCFD) is a condition frequently associated with HV. Our study aimed to assess and compare coronal plane alignment of medial column bones in HV, PCFD, PCFD HV and controls. Methods: We performed a retrospective IRB approved study. We collected 33 feet who consulted our center with combinations of symptomatic PCFD and HV. We then matched 33 HV, 33 PCFD, and 33 controls for BMI, Gender, and Age to this group. We assessed the coronal plane rotation of the navicular, medial cuneiform, M1 at its base and head, the Sesamoid Rotation Angle (SRA) with respect to the ground, and the hallux valgus angle (HVA) using Weight-Bearing CT images (Figure).The positions of the different joints (first naviculocuneiform (NC1), first tarsometatarsal (TMT1) and metatarsosesamoid rotation angle (MSRA)) were found by subtracting the adjacent angles. Intrinsic torsion of M1 was calculated by subtracting the M1 base angle from the M1 head angle.Normality of different variables was assessed using the Shapiro-Wilk test. Groups were compared using t test or ANOVA for normal and Mann Whitney or Kruskal Wallis for nonnormal variables. Results: HV, PCFD and PCFD HV presented higher M1 intrinsic torsion when compared to controls (respectively 7.3°[CI95%:2.9-11.7], p

Category: Hindfoot; Midfoot/Forefoot; Other Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a complex three-dimensional (3D) deformity characterized by peritalar subluxation (PTS) of the hindfoot through the triple joint complex. In this context, adjacent structures adopt different positions, and bone relations change, producing areas of higher or less contact and stress. The objective of this study was to use 3D distance maps (DMs) and coverage maps (CMs) from weightbearing CT (WBCT) images to assess subluxation across the Chopart joint in PCFD patients. We hypothesized that CMs would show decreased coverage indicative of subluxation through regions of the Chopart joint in PCFD patients when compared to controls. Methods: In this IRB-approved, retrospective case-control study, we analyzed WBCT data of 20 consecutive patients with flexible PCFD and 20 controls. Using principle component analysis, coverage area was divided into six regions on the talar head and 4 on the calcaneal-cuboid articular surface. Novel 3D distance mapping (DM) technique was used to objectively characterize joint coverage across the entire Chopart surface on both talus and calcaneus. Distance maps were measured in millimeters and colored to highlight covered areas. Distances less than 4mm were defined to be covered, while areas with distances greater than 4mm uncovered. Joint coverage was defined as percentage of articular area with DMs lower than 4 mm. Coverage Maps (CM) were built highlighting areas of coverage (teal) versus non-coverage (pink). The Foot and Ankle Offset (FAO) was used as a reference semi-automatic three-dimensional measurement. Comparisons were performed with independent t-tests, assuming unequal variances and p-values 0.05). The FAO was found to be correlated with changes in talar and calcaneal coverages (rs=0.90; R2=0.81). Conclusion: Our results support the hypothesis that significant changes occur at the Chopart joint in early flexible PCFD cases. Increased coverage in the lateral region of the talar head and decreased coverage in the medial and plantar regions point to internal rotation of the talus indicating subluxation through the entire joint. This behavior was also translated in the calcaneal- cuboid, where plantar and medial areas had a decrease in coverage. Coverage 3D mapping enabled objective subluxation quantification through the Chopart joint in early-stage PCFD. These findings may assist clinical assessment of normal joint alignment restoration during PCFD corrections.

Category: Hindfoot; Basic Sciences/Biologics; Other 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

Category: Basic Sciences/Biologics; Hindfoot; Other Introduction/Purpose: The use of bio-integrative implants in orthopedic surgery is growing rapidly. While many biomechanical and histological studies have been able to demonstrate their structural and biological properties, few clinical reports are available to support their advantages, such as good osteosynthesis, lower rates of removal, and diminished implant-related artifact in imaging studies. This clinical information is vital to providers when choosing the proper material and planning postoperative treatment. Hounsfield Units (HU) algorithms have been used as an objective assessment of joint space width. This pilot data analysis intends to test the capacity of the bio-integrative screws in reaching similar radiographical outcomes of the current metallic screws when analyzing medial displacement calcaneus osteotomies (MDCO). Our hypothesis is that both types of implants would present similar results. Methods: In this prospective comparative IRB-approved study, three patients undergoing MDCO with bio-integrative screws were compared to two patients undergoing the same surgery with metallic screws. Surgeon, primary diagnosis, technique, and displacement were the same for both groups. Patients were assessed using weight-bearing computed tomography at weeks 2, 6, and 12 postoperatively. Using a dedicated software, a 40x40x40mm cube, which defines a volume of interest (VOI), is centered at the osteotomy site. Within the VOI, initial computational analysis focused on image intensity (Hounsfield Units) profiles along lines perpendicular to the osteotomy line, crossing the osteotomy line and spanning approximately 8mm on either side. The HU intensity profiles were recorded, and graphical plots of the HU distributions were generated for each line. The plots were then used to calculate the HU contrast, a proxy for bone healing at the osteotomy site. Results: At 2 weeks, mean HU intensity in the metallic and bio-integrative were respectively 403.25 and 416.28 at the centerline (p=0.312), 513.24 and 386.57 at the inferior (p

Category: Midfoot/Forefoot; Other Introduction/Purpose: Lateral Column Lengthening (LCL), Medial Displacement Calcaneal Osteotomy (MDCO) and Cotton Osteotomy (CO) are considered the work-horse surgical procedures for Progressive Collapsing Foot Deformity (PCFD) correction. The amount of three-dimensional correction induced by each isolated procedure cannot be established in the clinical setting since procedures are frequently performed in combination based on deformity severity and surgeon's preference. Understanding the influence of each one of the procedures, as well as their magnitudes, in the overall 3D correction of the deformity would be extremely helpful in the surgical planning of PCFD. Therefore, our simulated weightbearing cadaveric study aimed to assess the amount of 3D correction induced by different magnitudes of isolated and combined LCL, MDCO, and CO procedures, using weightbearing CT (WBCT) imaging. Methods: In this cadaveric study 12 below-knee specimens with no deformity were used. They were mounted on a frame under 360N of axial load, while keeping conventional stance level tension to tendinous structures. Each group of four specimens underwent isolated and progressive magnitudes of MDCO (6, 10 and 14mm), LCL (6, 8 and 10mm) and CO (4, 8 and 12mm). Following isolated correction, the specimens were randomized into different amounts of combined correction, first with two procedures (only moderate correction; four specimens each combination) and then with three procedures (combined mild, moderate and large corrections; four specimens each). The 3D measurement Foot and Ankle Offset (FAO), representing the relative position between the center of the ankle joint and the weight bearing tripod of the foot, was calculated from WBCT datasets for each specimen in each one of the tested corrected conditions. Comparison between the different conditions was performed using Paired T-Test/Wilcoxon. Results: All isolated performed corrective procedures (MDCO, LCL and CO) significantly influenced FAO measurements (All p- values

Category: Midfoot/Forefoot Introduction/Purpose: Weight-Bearing Computed Tomography (WBCT) measurements represent a reliable tool for radiographic analysis of the first ray, including multiplanar assessment in the axial, sagittal, and coronal planes. WBCT can allow for more reliable studies of pathologies, such as Hallux Rigidus (HR), which permits several anatomical points to be evaluated for a correct clinical-radiographic diagnosis. In addition, new software with an advanced semi-automated segmentation system obtains semi-automatic 3D measurements of WBCT scan data sets, minimizing the errors in reading angular measurements. The study`s objective was (1) to assess the reliability of WBCT computer-assisted semi-automatic imaging measurements in HR, (2) to compare semi-automatic to manual measurements in the setting of HR, and (3) to compare semi-automatic measurements between a pathologic (HR) group and a control standard group. Methods: This was a retrospective, IRB approved study of patients with Hallux Rigidus deformity. The sample size calculation was based on the Metatarsus Primus Elevatus (MPE). A control group consisting of 20 feet without HR and a pathologic group consisting of 20 feet with HR was necessary for this study. All WBCT manual and semiautomatic 3D measurements were performed using the following parameters: (1) first Metatarsal-Proximal Phalanx Angle (1stMPP) (sagittal plane), (2) Hallux Valgus Angle (HVA), (3) first to second Intermetatarsal Angle (IMA), (4) Hallux Interphalangeal Angle (IPA), (5) first Metatarsal Lengths (1stML), (6) second Metatarsal Length (2ndML), (7) first Metatarsal Declination Angle (1stMD), (8) second Metatarsal Declination Angles (2ndMD), and (9) MPE. The semiautomatic 3D measurements were performed using the Bonelogic Software. The differences between pathologic and control cases were assessed with a Wilcoxon test and P

Category: Bunion; Lesser Toes; Midfoot/Forefoot Introduction/Purpose: Hallux valgus deformity (HVD) is a complex 3D distortion that involves varus, dorsiflexion and pronation of the first metatarsal. Deformity is usually assessed by conventional 2D measurements such as hallux valgus and intermetatarsal angle. Weightbearing CT (WBCT) 3D Distance Mapping (DM) and Coverage Mapping (CM) allow assessment of relative positioning between opposing articular surfaces, providing information in regards to articular coverage and joint subluxation, that can potentially influence development of arthritic degeneration and symptoms, as well as dictate outcomes. The aim of this study was to develop a DM and CM algorithm to assess metatarsophalangeal (MTP) and metatarso-sesamoid (MS) joint interaction in HVD patients and compare it to healthy controls. We hypothesized that significant MTP and MS joints lateral subluxation would be observed. Methods: In this IRB-approved study, we included 9 HVD patients (mean age 37.1y; 6F/3M) and 5 controls (mean age 39y; 4F/1M) that underwent foot WBCT foot. Bone segmentation of WBCT images for the first and second metatarsals, first and second proximal phalanxes as well as tibial and fibular sesamoids was performed using specific software. Joint interaction with DM and CM of the first and second MTP joints, as well as MS joints were calculated. The surface of the MTP joints were divided in a 2x2 grid using principal axes to provide a more detailed analysis. DMs were color coded to facilitate data interpretation (Figure). Blue color represented expected normal joint interaction (distances from 1 to 3 mm), yellow/red color symbolized increased joint distances (distances from 3 to 5 mm) and pink color indicate completely uncovered articular areas (distances >5mm). Comparisons were performed with independent t-tests/Wilcoxon. P values

Category: Sports; Ankle; Ankle Arthritis; Arthroscopy; Trauma Introduction/Purpose: Diagnosing syndesmotic injuries is challenging. Avoiding intra-operative syndesmotic malreduction is even more challenging. Malreduction can be devastating to the long-term health of the ankle joint and has been shown to be more frequent and unforgiving with rigid screw fixation when compared to flexible implants. Syndesmotic position assessment postoperatively is usually performed using bilateral CT. Evaluation is frequently subjective or based on conventional distance, angular, area, and volumetric measurements. Diagnostic accuracy of these measurements is still questionable. The goal of this study was to utilize a 3D Weightbearing CT distance mapping algorithm to objectively assess syndesmotic position in a cadaveric model simulating different patterns of syndesmotic malreduction. We also aimed to evaluate the relative changes in syndesmotic position when fixation was converted from rigid to flexible. Methods: In this cadaveric experimentation, four below-knee specimens were utilized. Specimens were mounted in an external frame simulated weightbearing condition (350N of axial load). Specimens underwent sequential WBCT imaging in four different conditions: native normal ankle, syndesmotic instability, malreduced, and released conditions. In the instability condition, syndesmotic ligaments were surgically released using a conventional limited lateral approach. The malreduced position consisted of controlled 5mm anterior displacement, 5mm posterior displacement, 15o of internal rotation, and over-compressed (160N) states. Fixation was performed with a single implant 20mm proximal to the ankle joint. Implant utilized allowed initial rigid screw- type fixation, followed by implant flexibilization similar to a suture-type fixation (released position). Tibia, fibula, and talus WBCT images were segmented, and syndesmotic incisura and gutter distances were assessed using a 3D distance map algorithm. The syndesmotic position was compared between normal, unstable, malreduced, and released positions. Color-coded representations of the observed differences were presented (Figure). Results: When comparing normal to unstable condition, we observed significant widening of the syndesmotic posterior aspect (average, 13.9%; p=0.004). Overall, all four malreduced positions lead to significantly decreased tibiofibular distances when compared to the unstable state, consistent with syndesmotic over-compression (average, 19.8%; p=0.01), particularly in the posterior aspect of the joint (average, 26.9%; p=0.04). This over-compression was also more pronounced in the anterior displacement (31.5%) and internal rotation malreductions (23.1%). In the released flexible position we found a non-significant trend towards widening of the tibiofibular distances (average, 12%; p=0.08) when compared to the malreduced conditions, indicating partial restoration the syndesmotic relationship. The syndesmotic distances in the released position were also not significantly different from the normal condition. When compared to normal, the lateral gutter demonstrated significant widening in the unstable condition (average 16.7%; p=0.02), narrowing in the malreduced state (average 6.6%; p=0.04), and widening in the released position (average 3.7%; p=0.002). Conclusion: In this study we used 3D WBCT distance mapping to assess syndesmotic position in a cadaveric model simulating syndesmotic instability and multiple syndesmotic malreduction conditions (anterior and posterior displacement, internal rotation and over-compression). We observed significant widening when the syndesmotic ligaments were sectioned, followed by significant tibiofibular narrowing in the malreduced and fixed rigid states. When the implant fixation was released, we observed a trend towards restoration of normal syndesmotic alignment, with relative widening that was however not significantly different from the malreduced rigidly fixed state. Increased sample size cadaveric assessment and clinical studies are necessary to validate our results.

Summary: Quantifying tRNAs is crucial for understanding how they regulate mRNA translation but is hampered by their extensive sequence similarity and premature termination of reverse transcription at multiple modified nucleotides. Here, we describe the use of modification-induced misincorporation tRNA sequencing (mim-tRNAseq), which overcomes these limitations with optimized library construction and a comprehensive toolkit for data analysis and visualization. We outline algorithm improvements that enhance the efficiency and accuracy of read alignment and provide details on data analysis outputs using example datasets.For complete details on the use and execution of this protocol, please refer to Behrens et al. (2021). : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Objective: To develop distance-mapping and coverage-mapping algorithms to assess metatarsophalangeal and metatarsal-sesamoid joint interaction in hallux valgus patients, comparing them to a control group. Methods: A total of 9 hallux valgus patients (mean age 37.1 y; 6 F/3 M) and 5 controls (mean age 39 y; 4 F/1 M) underwent weight-bearing computed tomography. Specific software was used to obtain bone segmentation images of the first and second metatarsals, the first and second proximal phalanxes, and the tibial and fibular sesamoids. Joint interaction based on distance mapping and coverage mapping of the first and second metatarsophalangeal joints and the metatarsal-sesamoid joints were calculated. The surfaces of the metatarsophalangeal joints were divided in a 2-by-2 grid using the principal axes to provide a more detailed analysis. P-values

Category: Basic Sciences/Biologics; Hindfoot Introduction/Purpose: Implant-related artifact (IRA) represents an important limitation in Computed Tomography (CT) assessment of osteotomy and fracture healing, bone-implant integration, and success of fusion procedures. Metallic implants are the most used in foot and ankle surgery and are recognized as important IRA generators. Absorbable and bio-integrative (BI) implants are attractive options for bone fixation when postoperative CT imaging is likely, particularly in procedures with higher risk for nonunion. However, the literature comparing IRA with metallic and BI implants is scarce. The objective of this study was to assess the degree of IRA around metallic and BI cannulated screws. Our hypothesis was that BI implants would demonstrate significantly decreased IRA around the inserted screws. Methods: In this cadaveric/CT imaging study, 2 below-knee specimens were used. Medial displacement calcaneal osteotomy was performed through a 5-cm long lateral heel approach. Calcaneal tuberosity was displaced medially by 10mm and fixed provisionally with 2 parallel K-wires under fluoroscopic guidance. Specimens were fixed with two headless 4.0 millimeters cannulated screws, either metallic or BI. Cone-beam CT imaging of both specimens was acquired following osteotomy screw fixation (120kVp, 5.5mA, 0.25mm isotropic). Using a dedicated software, the overall dispersion of Hounsfield units (HU) in a 3D cube of 30mm edge length was assessed. Four HU lines were then traced parallel to the screws, crossing the osteotomy site. Lines 1, 2, 3 and 4 were positioned respectively: In close proximity, over, inside the cannulation and away from the implant. The HU dispersion in these lines was measured and compared between metallic and BI implanted specimens, using T-tests/Wilcoxon analysis. P-values

Category: Basic Sciences/Biologics; Hindfoot; Midfoot/Forefoot Introduction/Purpose: Progressive collapsing foot deformity (PCFD), formerly termed Adult-Acquired Flatfoot Deformity (AAFD), is a complex 3D deformity characterized by peritalar subluxation (PTS) of the hindfoot through the triple joint complex. In this context, adjacent structures may adopt different positions and boney relations can change, producing areas increased contact or subluxation. The objective of this study was to use 3D distance maps (DMs) and coverage maps (CMs) from weightbearing CT (WBCT) images to assess subluxation across the Chopart joint in PCFD patients. We hypothesized that CMs would show decreased coverage indicative of subluxation through certain regions of the Chopart joint in PCFD patients when compared to the controls. Methods: In this IRB-approved, retrospective case-control study, we analyzed WBCT data of 18 consecutive patients with flexible PCFD and 10 controls. Using principle component analysis, candidate coverage area was divided into nine regions on the talar head and 4 regions on the calcaneal-cuboid (CC) articular surface. Novel 3D distance mapping (DM) technique was used to objectively characterize joint coverage across the entire Chopart joint surface on both the talus and calcaneus. Distance maps were measured in millimeters and colored to highlight covered areas. Areas with distances less than 4mm were defined to be covered, while areas with distances greater than 4mm were considered to be uncovered. Joint coverage was defined as percentage of articular area with DMs lower than 4 mm. Coverage Maps (CM) were created to highlight areas of coverage (teal) versus non- coverage (pink). Comparisons were performed with independent t-tests, assuming unequal variances. P values

Category: Ankle Introduction/Purpose: Recently, weightbearing computed tomography (WBCT) has been utilized to provide more comprehensive and accurate assessment of complex foot and ankle deformities, notably to diagnose and stage Progressive Collapsing Foot Deformity (PCFD). The 3D data provided by WBCT has enabled the developed of novel tools like distance mapping (DM), coverage mapping (CM), and volume measurements. Over the past year, novel DM and CM have shown promise in providing sensitive automated measures of peritalar subluxation, a major component of PCFD. However, the early effects of PCFD on the tibiotalar joint have not yet been quantified. This study sought to use DM and CM to objectively characterize the effects of PCFD on the tibiotalar and tibiofibular joints. We hypothesized that changes seen in early PCFD will be identified. Methods: IRB approval for retrospective review of patient data from 2014-2020 was obtained to identify patients with clinical and radiographic diagnoses of PCFD. The first consecutive 20 patients with symptomatic flexible PCFD and high-resolution weightbearing CT examination without arthritis that had not undergone prior surgery were selected and compared with 20 controls. Fully automated volume measurements of the syndesmosis at 1cm, 3cm, and 5cm from the tibiotalar joint were performed as well as of the medial and lateral tibiotalar gutters based on models created in Disior Bonelogic. Distance Maps (DMs) were obtained for the tibiofibular incisura, tibiotalar joint, and gutters. Coverage maps (CMs) were created using the measured 3DDMs to identify joint interaction, subluxation, and impingement. Data were checked for normality using the Shapiro- Wilk W test. Two-tailed independent samples student t-tests or Wilcoxon Tests were used to assess differences between groups. Results: There were significant decreases in coverage of all 3 anterior regions of the tibiotalar joint in PCFD patients when compared to controls along with corresponding significant increases in coverage of all 3 posterior regions (Figure). There were no significant differences in mean or minimum distances in any region of the tibiotalar joint surface. Significant increases in average and minimum DMs of the anterior medial (36%, p

Objective: To assess interobserver reliability of previously described coronal plane rotation measurements of medial column bones and to assess their ability to accurately quantify changes in rotational profile. Methods: Two cadaveric below-knee specimens were implanted with pins in each bone of the medial column. Weight-bearing computed tomography (CT) scans were acquired in a simulated standing position under neutral, supinated, and pronated conditions. For each specimen and condition, 2 observers measured the coronal plane rotation of the navicular, medial cuneiform, first metatarsal base, shaft, and head, and proximal phalanx of the hallux as previously described. The rotation of each pin was measured relative to the ground in the coronal plane for each condition. These measurements were defined as benchmarks for the rotational profile of each bone. The correlation between these benchmarks and direct bone measurements was then assessed. Intraclass correlation coeficiente was used to assess interobserver reliability. Pearson’s coefficient was used to evaluate correlations. Results: The interobserver reliability of direct bone measurements ranged from 0.98 to 0.99. Correlations between pin rotation and direct measurements ranged from ρ=0.87 to 0.99 across the neutral, supinated, and pronated conditions. Conclusion: Coronal plane rotation measurements of medial column bones described in this study are reliable tools. Level of Evidence III; Case-Control Study.