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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. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: The transverse tarsal arch (TTA) is perpendicular to the medial longitudinal arch (MLA) and enhances the intrinsic stiffness of the longitudinal curvature. Given the importance of TTA/MLA, a collapse of this complex may indicate a point of TA/MLA uncoupling, resulting in a decreased foot stiffness and a gradual flattening observed in Progressive Collapsing Foot Deformity (PCFD). A recently described angle, the transverse arch plantar (TAP) angle, was found to be significantly increased in PCFD compared to controls, indicating a transverse as well as longitudinal collapse. The objective of this study is to assess the TAP angle in patients who underwent surgical treatment for PCFD and to determine whether surgical intervention has the potential to enhance or alter the transverse arch. Methods: This retrospective cohort, single-center study received institutional review board approval. Patients presenting with symptomatic PCFD who underwent weight-bearing CT (WBCT) assessment at our institution were included in this study. All patients included underwent a PCFD surgical correction. Exclusion criteria comprised individuals under 18 years old, those with a history of prior foot surgery, individuals with tarsal coalition, inflammatory diseases, or neuropathic pain. Demographic data, including sex, age, body mass index (BMI), surgery date, date of WBCT, and the number of procedures performed to correct PCFD, were collected. As previously described in the literature, the TAP angle was measured as the angle between the most plantar side of the first, second, and fifth tarsometatarsal joints. The foot and ankle offset (FAO) was also measured (Figure 1). The normality of all quantitative variables was assessed using the Shapiro-Wilk test, and the measurements were compared using a Student t-test or Wilcoxon test. Results: The sample comprised 26 patients, of which 20 are female. The mean age was 47 years, the mean BMI was 34.1, and the average time between surgery and weight-bearing CT (WBCT) was 108 days (Table 1). The mean number of interventions during the surgical procedure was 4.9 (min. 2; max. 8). The pre-operative TAP mean angle was 113.6º (SD 7.1º; CI 95% 110.7º-116.5º), while the post-operative TAP mean angle was 106.0º (SD 7.3º; CI 95% 103.1º-109.0º), and the difference is statistically significant (p=0.0001). Additionally, the pre-operative mean FAO was 9.4% (SD 3.3%; CI 95% 8.0%-10.7%), and the post-operative mean FAO mean was 1.9% (SD 2.8%; CI 95% 0.8%-3.0%), with a statistically significant difference as well (p=0.0001) (Table 2). Conclusion: This study indicates that surgical correction of PCFD significantly reduced the collapse of the TAP angle by 6.7% postoperatively (p=0.0001). Considering the critical role of TA/MLA coupling in maintaining intrinsic foot stiffness, targeting this specific collapse for correction may be a key objective for the success of surgical interventions. Additional research investigating functional outcomes is essential to assess the correlation between TAP angle correction and patients' reported outcome (PROMs) as well as their overall satisfaction. [ABSTRACT FROM AUTHOR]

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 screwtype 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. [ABSTRACT FROM AUTHOR]