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Category: Sports; Other Introduction/Purpose: Minimally invasive approaches to Achilles tendon (AT) repair have garnered significant attention due to their reported effectiveness. Due to the limited visibility of the tendon, a crucial factor for the success of these approaches lies in the precise targeting and adequate capture of the tendon substance. Insufficient tendon capture can lead to re-rupture or tendon elongation, potentially leading to poor patient-outcomes. Since many of the current techniques or devices for minimally invasive AT repair rely on needle passage through a single axial plane, it is imperative to understand the axial plane orientation of the AT along its course. This study aims to elucidate the axial plane position and width of the AT from its distal insertion to a level well above its common tear site. Methods: In this retrospective study, magnetic resonance imaging (MRIs) from 82 individuals (mean age: 38.7 years) with no history of AT pathology were reviewed from the foot and ankle registry of a single institution. Any patients with evidence of foot and ankle malalignment or those with poor quality MRIs were excluded from the study. Multiplanar reconstruction of the MRI images was performed to enable synchronized viewing of both the sagittal and axial planes of each MRI scan. Measurements were made to determine the axial axis of the AT at distances of 3, 5, 7, 9, and 11 cm from its insertion. These measurements were taken in relation to both the transmalleolar (TM) axis and the axis at the AT insertion (Figure 1). The width of the AT was also measured at these corresponding levels. Results: The average rotation of the AT across all measurement levels showed an external rotation relative to the TM axis (Figure 2). The least rotation was observed at the 3cm level (2.1 degrees), while the maximum rotation was seen at both the 7cm and 9cm levels (11.2 degrees). There was a pattern where the AT showed an increasing external rotation as it extended proximally from 3cm to 9cm from its insertion. Between 5 cm and 7 cm from the insertion, there was a shift in the tendon's orientation (p<.0001), transitioning from internal to external rotation (Figure 2). Moreover, a noticeable reduction in the width of the AT was observed between the 5 cm and 7 cm measurement levels, distinct from the other levels. Conclusion: The rotational profile of the AT observed in this study indicates the need for caution regarding possible external rotation of the AT, especially when targeting its proximal portion using a minimally invasive approach, compared to its distal part. The considerable variations in AT orientations across different individuals underscore the potential benefits of using intraoperative assistive techniques such as ultrasonography to determine individual rotational profiles. Furthermore, the noted narrower width and rotational differences between the 5 cm and 7 cm levels could explain the frequent instances of AT ruptures within this specific range. [ABSTRACT FROM AUTHOR]

Category: Hindfoot; Basic Sciences/Biologics Introduction/Purpose: Talonavicular and subtalar joint arthrodeses are frequently performed in isolation. While these procedures generally produce good results, patients often experience reduced range of motion (ROM) and adjacent hindfoot arthritis. Several studies have shown that the arthrodesis of a single hindfoot joint considerably limits the motion of the adjacent unfused joints during simplified loading scenarios, but the effect on kinematics during dynamic activity is unknown. This study sought to assess the changes in subtalar and talonavicular kinematics after isolated talonavicular and subtalar arthrodesis, respectively, during simulations of stance and to quantify the motion of the unfused joint after the first hindfoot arthrodesis. We hypothesized that isolated arthrodesis of the subtalar and talonavicular joints would significantly alter kinematics and reduce the remaining unfused joint's ROM. Methods: Fourteen mid-tibia specimens were used. A validated robotic gait simulator of the stance phase of gait was used. An eight-camera motion-capture system tracked reflective markers on the talus, calcaneus, and navicular. Two testing conditions were simulated for each specimen: intact condition and after isolated subtalar or talonavicular arthrodesis. Each specimen was randomized into two groups of seven, either receiving an isolated subtalar (STIso) or talonavicular arthrodesis (TNIso). The subtalar and talonavicular arthrodeses were performed using 7.0-mm and 5.5-mm partially-threaded screws, respectively. The difference in subtalar and talonavicular joint kinematics between the intact and arthrodesis conditions was calculated using bootstrapped bias-corrected 95% confidence intervals of the joint kinematics. Significant differences (P< 0.05) were defined as areas where the intervals of the intact and arthrodesis conditions did not overlap. ROM for each joint was calculated by subtracting minimum from maximum joint motion, and the difference between conditions was analyzed using paired t-tests. Results: The TNiso demonstrated significant changes in the subtalar kinematics. After the TNiso, mean subtalar plantarflexion decreased during late stance from 3.2º to 0.1º (P< 0.05). Mean subtalar inversion decreased in both early and late stance from 1.2° to 0.3° and 7.5° to 2.7°, respectively. Conversely, subtalar inversion increased during mid-stance from 1.7° to 2.8° after arthrodesis. In the axial plane, mean subtalar adduction decreased in the early and late stances from 1.6° to 0.4° and 4.8° to 0.4°, respectively. The subtalar ROM was significantly reduced in the sagittal and coronal planes by 40%(P=0.009) and 46%(P=0.002), respectively. No significant differences in talonavicular kinematics were observed after isolated subtalar arthrodesis; however, the absolute ROM was significantly reduced by 61%(P=0.007) and 50%(P=0.003) in the coronal and axial planes, respectively. Conclusion: Our study showed that both types of isolated hindfoot arthrodesis decreased the ROM of the remaining unfused hindfoot joint. However, we only observed significant changes in subtalar kinematics following isolated talonavicular arthrodesis. Conversely, isolated subtalar joint fusion did not significantly affect talonavicular kinematics, confirming previous findings that have identified the talonavicular joint as the key hindfoot joint. Isolated subtalar fusion may represent a viable treatment option, as it may have a lesser impact on the overall hindfoot function. However, isolated talonavicular arthrodesis should be avoided when possible since the procedure significantly affects the kinematics of the unfused subtalar joint. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux valgus(HV) is a triplanar deformity that includes the pronation of the first ray. Although there is little data regarding the effect of pronation on clinical outcomes, the rotational component of HV may play an important role. One study suggested that the modified Lapidus technique effectively decreased the pronation of the first ray. However, there is no evidence for alternative procedures such as minimally invasive(MIS) bunionectomy. This study sought to assess if MIS bunionectomy can effectively correct the first ray's pronation and determine the correlation with improved PROMIS scores. In addition, the association between postoperative first-ray pronation and the sesamoid station was investigated. We hypothesized a significant decrease in first-ray pronation after MIS bunionectomy, which would be associated with improved PROMIS scores. Methods: Sixty-three consecutive patients who underwent MIS bunionectomy with available pre- and at least 5-month postoperative WBCT-scans were included. Pre- and postoperative measurements of HV deformity, including the intermetatarsal angle(IMA) and hallux valgus angle (HVA) on plain radiographs, and triplanar pronation angle (TAP – a measure of first ray pronation) and sesamoid station from WBCTs, were performed as previously described. The TAP was referenced to the dorsal aspect of the second metatarsal base. Pre- and 1-year postoperative PROMIS scores were reviewed. Sample t-tests were used to compare pre- and postoperative values. The Kruskal-Wallis test assessed statistical differences between postoperative sesamoid station groups regarding postoperative TAP or IMA. Spearman rank (rho) was used to assess correlations between pre- to postoperative change in TAP with PROMIS scores in the physical function (PF), pain interference (PIF), and pain intensity (PI) domains. Scatterplots were simultaneously presented to visualize potential trends between TAP and PROMIS scores. Results: The mean TAP significantly decreased by 8.21º(95%CI -9.62,-6.8) after MIS bunionectomy (p< 0.05). Mean(SD) pre- and postoperative TAP values were 31.57º(8.3) and 23.36º(7.6), respectively. Similarly, mean HVA and IMA values decreased by 21.98º and 11.41º, respectively. Mean preoperative sesamoid station was 1.84, which decreased to 0.95 after surgery. Forty-four patients reduced their sesamoid position by one station. There was a statistically significant difference in TAP between postoperative sesamoid station groups (p=0.038). Mean(SD) postoperative TAP according to sesamoid station was 25.93º(6.2) for group 1, 23.83º(7.9) for group 2, and 18.75º(6.6) for group 3. No significant differences between groups were observed regarding IMA (p=0.25). There was a modest correlation between TAP change and PROMIS PF (rho = 0.046), PIF (rho = -0.30), and PI (rho = -0.03). Conclusion: Our study suggests that MIS bunionectomy is an effective tool for reducing first-ray pronation in patients with HV. Although there was a statistically significant correlation between first-ray pronation and sesamoid station, our results showed that patients with higher first-ray pronation had less reduced sesamoids. Therefore, these should be considered separate deformities, and the sesamoid station shouldn't be used as a guide for pronation correction. It appears that correction of the first-ray pronation is poorly associated with 1-year PROMIS scores. Consequently, future studies assessing mid-to-long-term effects of first-ray pronation on clinical outcomes, such as recurrence, are still warranted. [ABSTRACT FROM AUTHOR]

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux Valgus (HV) is a common foot condition often requiring surgical intervention. Minimally invasive bunionectomy (MISB) has gained popularity for HV correction. While previous research has focused on distal foot width changes following surgery, this study introduces a novel midshaft measurement to assess proximal transverse midfoot width. The study aims to provide a comprehensive evaluation of foot width changes post-MISB. Methods: A retrospective review of prospectively collected data was conducted for 44 patients who underwent MISB for HV via an institutional outcome registry. Demographic data, surgical details, radiographs, and foot width measurements were collected. Changes in hallux valgus angle (HVA) and intermetatarsal angle (IMA) were also measured. The novel midshaft bony and soft tissue foot width measurements were included. Two independent observers conducted all preoperative and postoperative measurements. Results: Intraclass correlation coefficients (ICCs) demonstrated high interobserver reliability (all ICCs >0.70) for all measurements. MISB resulted in a consistent reduction in distal foot width, both bony (8.17%) and soft tissue (5.24%)(p < 0.001). These reductions correlated with changes in HVA and IMA, suggesting the extent of deformity correction influenced distal foot width (all r > 0.375, p < 0.05). However, the study revealed that proximal foot width, as measured by midshaft bony width, increased (5.27%) in the majority of cases (p < 0.001). Changes in midshaft foot width showed no correlation with HVA or IMA alterations. Conclusion: MISB for HV leads to an increase in midshaft foot width due to the unique mechanics of the procedure. Simultaneously, there is a decrease in distal foot width, which correlates with the extent of deformity correction. This results in a more uniform foot width. These findings may influence patient satisfaction, comfort, and shoe wear capabilities post-surgery. Further research should assess patient perception and comfort regarding these foot width changes after MISB. [ABSTRACT FROM AUTHOR]

Category: Ankle; Basic Sciences/Biologics Introduction/Purpose: Although double hindfoot arthrodesis (subtalar and talonavicular) provides pain relief and deformity correction for patients with end-stage arthritis, altered ankle biomechanics may occur following these procedures. Furthermore, it has been reported that hindfoot fusions may lead to progressive ankle degenerative changes and a higher failure rate in patients undergoing total ankle arthroplasty. Previous biomechanical studies demonstrated that hindfoot fusion altered ankle joint kinematics and contact mechanics during simplified loading scenarios, but the effect during dynamic activity is unknown. Therefore, this study sought to quantify the changes in ankle kinematics after a double hindfoot arthrodesis during the stance phase of simulated gait. In addition, we sought to assess whether the sequence in which joints are fused plays a role in altering ankle kinematics. Methods: Fourteen mid-tibia specimens underwent stance phase simulations of level walking using a validated six-degree of freedom robot. All specimens had neutral hindfoot alignment. An eight-camera motion system tracked reflective markers in the tibia, talus, calcaneus, and navicular bones. Simulated arthrodeses of the subtalar and talonavicular joints were performed using two 7.0mm and two 5.5mm crossing screws, respectively. The subtalar alignment was set at 5º valgus, and the talonavicular at neutral abduction/adduction. Fluoroscopic images confirmed proper screw position and hindfoot alignment. Each specimen was tested in three conditions: pre-arthrodesis(intact), isolated arthrodesis(subtalar or talonavicular joint), and double arthrodesis(double). Specimens were further divided into two groups depending on whether the subtalar(STDouble) or talonavicular(TNDouble) joint was fused first. Ankle kinematics were calculated for each condition for the entire cohort of specimens and each of the two groups. Bias-corrected 95% confidence intervals of the difference in ankle kinematics relative to the intact condition were constructed. Results: Double hindfoot arthrodesis significantly altered ankle kinematics(Figure1A). Ankle plantarflexion decreased during heel strike by up to 2.0° on average and increased during toe-off by 6.5° compared to the intact condition. Ankle eversion increased by 1.5º and 2.5º on average during mid- and late stance, respectively. Internal rotation decreased during midstance by 1.1º on average and increased in late stance by 4.5°. The order in which hindfoot joints were fused significantly influenced ankle kinematics(Figure1B). On average, the TNDouble condition produced 2.3º and 3.5º more ankle eversion during the mid- and late stance, respectively, and 2.10° more ankle internal rotation during the early stance compared to the STDouble condition (not shown). Significant changes were also present after isolated hindfoot arthrodeses and remained consistent after the double arthrodesis. Conclusion: Double hindfoot arthrodesis significantly altered ankle kinematics throughout stance. Ankle kinematics also differed depending on which joint was fused first. Notably, the TNDouble condition produced more ankle internal rotation during early stance and more ankle eversion during mid- and late stance compared to the STDouble condition. This finding suggests that the sequence in which joints are fused affects the resultant ankle kinematics. Finally, the kinematic changes after isolated hindfoot arthrodesis remained consistent after incorporating the second joint into the fusion. It appears that once one joint needs to be fused, avoiding the double arthrodesis may not necessarily protect the ankle. [ABSTRACT FROM AUTHOR]

Category: Ankle Arthritis; Ankle Introduction/Purpose: Establishing a surgical plan for ankle arthritis requires a thorough understanding of the deforming forces involved. While ankle morphology-based classification and application are common in the surgical treatment of varus ankle arthritis (i.e., Takakura stage), such an approach has not been described for valgus ankle arthritis. Progressive collapsing foot deformity (PCFD) has been identified as the major cause of non-traumatic valgus ankle arthritis. However, mounting evidence suggests that it can also develop without PCFD, which may mean that the etiology and possibly the outcomes of treatment are different when comparing the two groups. Therefore, this study aimed to investigate whether weightbearing ankle radiographs can be used to differentiate PCFD origin from non-PCFD origin in valgus ankle arthritis. Methods: This study retrospectively reviewed patients who were surgically treated for asymmetric valgus ankle arthritis at our institution between 2017 and 2021. Patients with valgus tibiotalar tilt (TT >4 degrees and Meary's angle>30 degrees) were included in the PCFD group (n=24). A control group (non-PCFD group [n=24]) with valgus tibiotalar tilt>4 degrees and Meary's angle < 4 degrees was also established. In the weightbearing ankle anteroposterior (AP) view, the TT and medial distal tibial angle (MDTA) were measured. Additionally, to assess mediolateral position of the talus, the talar center migration (TCM) and lateral talar dome-plafond distance (LTD-P) ratio was measured (Figure 1A). Other PCFD radiographic parameters were also measured. In weightbearing computed tomography (WBCT), the degree of axial plane talocalcaneal subluxation was assessed using transmalleolar axis method as previously described, and the prevalence of sinus tarsi bony impingement was assessed. All parameters were compared between groups using Student t- or chi-square tests. Results: Both groups demonstrated a similar degree of TT, with a mean and standard deviation of 11.1±7.8 degrees in the PCFD group and 12.7±5.9 degrees in the non-PCFD group (p=0.2013, Table 1). However, the PCFD group showed a significantly greater TCM and LTD-P ratio compared to those of the non-PCFD group (p < 0.0001), indicating that PCFD patients have a more medially translated talus in ankle AP radiographs (Figure 1A). WBCT showed that the PCFD group had a greater axial plane talocalcaneal subluxation (p < 0.0001) and a higher prevalence of sinus tarsi bony impingement (p=0.0077) compared to the non- PCFD group, indicating a different degree of subtalar joint subluxation between the two groups. Conclusion: This study demonstrates that weightbearing ankle radiographs reveal different morphologies based on the etiology of valgus ankle arthritis. While both groups exhibited similar degrees of valgus tibiotalar tilt, PCFD patients demonstrated medial translation of the talus compared to non-PCFD patients. We propose a morphology-based classification (Figure 1B) that may assist in differentiating between the PCFD and non-PCFD origins of valgus ankle arthritis. Also, the different morphology of the valgus tibiotalar tilt in the each group may mean that they may require different treatments, as well as potentially different outcomes of treatment for the valgus tibiotalar tilt. [ABSTRACT FROM AUTHOR]

Category: Ankle Arthritis; Ankle Introduction/Purpose: Restoring the native joint line correlates with better clinical outcomes in total knee arthroplasty. Yet, the effect of joint line elevation on clinical outcomes after total ankle arthroplasty (TAA) remains unclear. A previous study reported that pre- and post-TAA joint line heights, as measured by the joint line height ratio (JLHR), were elevated compared to non- arthritic ankles. However, the clinical impact of this has yet to be determined. Therefore, this study assessed the relationship between the TAA joint line level with post-TAA range of motion (ROM) and PROMIS scores. We hypothesized that an elevated joint line would be associated with restricted post-TAA dorsiflexion and worse postoperative PROMIS scores. Methods: This is a single-center review of 150 patients who underwent primary TAA. Patients with (1)fibular or medial malleolar osteotomy, (2) component subsidence, and (3) incomplete radiographs or outcome scores were excluded. Demographic data, surgical protocol, pre- and postoperative radiographs, and 1-year postoperative PROMIS scores were reviewed. Radiographic measurements included JLHR, pre- and post-TAA tibiotalar dorsiflexion and plantarflexion, and tibial component sagittal alignment. Two graders measured post-TAA JLHRs, and the average of the two graders was used for the analysis. Rater agreement was assessed using intraclass correlation coefficients (two-way random effects model). Relationships between JLHR, post-TAA tibiotalar ROM, and PROMIS scores were investigated using Pearson correlation. Multiple linear regression models were used to investigate the association of JLHR with post-TAA tibiotalar total ROM, dorsiflexion, and plantarflexion, after adjusting for pre- TAA ROM, tibial component sagittal alignment, gastrocnemius release (GR), Tendo-Achilles lengthening (TAL), and polyethylene size. Results: The interobserver reliability of the JLHR was excellent (r=0.98). Mean JLHR decreased from 1.66 pre-TAA to 1.55 post- TAA (P < 0.001), indicating the joint line was significantly lowered postoperatively. Greater elevation of the post-TAA JLHR was associated with significantly decreased post-TAA dorsiflexion (r=-0.26, P< 0.001) and worse 1-year PROMIS physical function (r=- 0.22, P=0.046), pain intensity (r=0.22,P=0.042), and pain interference scores (r=0.29,P=0.007). There was no correlation between JLHR and post-TAA plantarflexion (P=0.76). Regression analysis identified a 5º reduction in post-TAA dorsiflexion with each 1.0 unit increase in JLHR (Coef=-5.13, P=0.005). Post-TAA total ROM (Coef=-3.6,P=0.21) and plantarflexion (Coef=0.91, P=0.67) were not associated with JLHR. Additionally, there was no association between post-TAA total ROM and tibial component sagittal alignment, GR, TAL, or polyethylene size. Conclusion: In this study, the joint line of the ankle was lowered after TAA, and the JLHR was a reliable and clinically applicable method for assessing it. An elevated joint line significantly correlated with restricted post-TAA dorsiflexion, but this may only be clinically relevant for patients with significant (>1.0 unit) changes in the joint line level. In addition, a higher joint line was correlated with worse 1-year PROMIS scores. These results suggest that surgeons should consider the joint line level during TAA preoperative planning to obtain improved clinical outcomes and ankle dorsiflexion. [ABSTRACT FROM AUTHOR]