BACKGROUND:Patients with progressive collapsing foot deformity (PCFD), hallux valgus (HV), and midfoot arthritis (MA) could benefit from a bone-block tarsometatarsal (TMT) arthrodesis. The allograft wedge, producing distraction and plantarflexion, provides a stable medial column while correcting the deformity, but with increased risk of pseudoarthrosis. The objective of this study was to report the clinical nonunion and results of the bone-block first-TMT arthrodesis in collapsed feet. METHODS:In this short-term prospective cohort (mean follow-up 17 months) we evaluated patients with PCFD, HV, and MA who underwent allograft bone-block first-TMT fusion between August 2020 and November 2022. Patients were kept nonweightbearing for 6 weeks and followed, having a WBCT at 3 months and subsequent follow-ups. Bone healing was determined by at least 50% of bone trabeculae crossing both graft interfaces. Complications were documented. Forefoot arch angle (FAA), Meary angle, talonavicular coverage angle (TNCA), middle facet subluxation (MFS), and foot and ankle offset (FAO) were obtained, as well as PROs. RESULTS:Sixty-four patients (67 feet) were included, mean age 54.0 (18-77), body mass index 31.6 (29.6-33.6), 17.3 months (6-33) follow-up. Median allograft size was 8 mm (5-19 mm). Clinical nonunion rate was 11.9%, minor complications 2.9%, and major complications 5.9%. Tomographic healing at 3 months occurred in 86.4% and 66.7% at the most recent WBCT (mean: 10.1 months; 6-29). Improvement (P < .001) in FAA of 6.9 degrees (5.8-7.9), MFS of 22.6% (19.8-25.4), TNCA of 13.5 (12.1-14.3), Meary angle of 8.1 degrees (6.7-9.5), and FAO of 3.8% (3.1-4.6) were found. PROs improved for VAS, PROMIS-PH, PROMIS-PI, Pain Catastrophic Scale, and EFAS (P < .001). CONCLUSION:Although the first-TMT bone-block arthrodesis restored many markers associated with foot collapse and alignment, the clinical nonunion rate was 11.9%, which is in the top range of the literature for TMT fusions. The use of allograft wedges can explain our findings. Tomographic healing, initially 86.4% at 3 months, decreased to 66.7% at the most recent follow-up.

BACKGROUND:Flatfoot, or pes planus, is a common anatomical variation marked by a reduced or absent longitudinal arch. Although it is often considered benign, the condition can progress to progressive collapsing foot deformity (PCFD), a debilitating pathology. This study aimed to identify imaging biomarkers that distinguish asymptomatic flatfoot from PCFD by comparing 3D measurements among normally aligned feet, asymptomatic flatfeet, and feet with PCFD. METHODS:A prospective, comparative, and controlled study was conducted on 561 feet in 475 subjects: 88 control subjects with 98 normally aligned feet, 66 control subjects with 132 asymptomatic flatfeet, and 321 patients with 331 feet with symptomatic PCFD. Bilateral weight-bearing computed tomography (WBCT) scans were performed, and various 3D measurements were analyzed, focusing on hindfoot valgus (Class A deformity), midfoot and/or forefoot abduction (Class B), arch collapse (Class C), and peritalar subluxation (PTS) (Class D). Statistical analysis, including multivariable nominal regression, was used to identify significant predictors of symptoms. RESULTS:Progressive increases in Class A, B, and C deformity parameters were observed from normally aligned feet to asymptomatic flatfeet and finally to feet with PCFD. Significant differences in PTS (Class D deformity) were found only in the comparison between the feet with PCFD and the control groups, with reduced joint coverage and increased sinus tarsi coverage, indicating extra-articular impingement. Multivariable analysis identified the minimum sinus tarsi distance as the strongest predictor of symptoms, with a threshold of 1.9 mm best distinguishing symptomatic from asymptomatic feet. CONCLUSIONS:This study demonstrated that although hindfoot valgus, midfoot and/or forefoot abduction, and arch collapse deformities progressively increase from normal alignment to PCFD, significant subtalar joint subluxation and sinus tarsi impingement were unique to symptomatic PCFD. These findings suggest that PTS can serve as a crucial biomarker for diagnosing pathologic flatfoot (PCFD) and differentiating it from asymptomatic flatfoot. Future research should explore the predictive value of PTS biomarkers in identifying flatfoot at high risk for collapse and their impact on clinical management and surgical decision-making. LEVEL OF EVIDENCE:Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Background:Flatfoot, or pes planus, is a common anatomical variation marked by a reduced or absent longitudinal arch. Although it is often considered benign, the condition can progress to progressive collapsing foot deformity (PCFD), a debilitating pathology. This study aimed to identify imaging biomarkers that distinguish asymptomatic flatfoot from PCFD by comparing 3D measurements among normally aligned feet, asymptomatic flatfeet, and feet with PCFD.Methods:A prospective, comparative, and controlled study was conducted on 561 feet in 475 subjects: 88 control subjects with 98 normally aligned feet, 66 control subjects with 132 asymptomatic flatfeet, and 321 patients with 331 feet with symptomatic PCFD. Bilateral weight-bearing computed tomography (WBCT) scans were performed, and various 3D measurements were analyzed, focusing on hindfoot valgus (Class A deformity), midfoot and/or forefoot abduction (Class B), arch collapse (Class C), and peritalar subluxation (PTS) (Class D). Statistical analysis, including multivariable nominal regression, was used to identify significant predictors of symptoms.Results:Progressive increases in Class A, B, and C deformity parameters were observed from normally aligned feet to asymptomatic flatfeet and finally to feet with PCFD. Significant differences in PTS (Class D deformity) were found only in the comparison between the feet with PCFD and the control groups, with reduced joint coverage and increased sinus tarsi coverage, indicating extra-articular impingement. Multivariable analysis identified the minimum sinus tarsi distance as the strongest predictor of symptoms, with a threshold of 1.9 mm best distinguishing symptomatic from asymptomatic feet.Conclusions:This study demonstrated that although hindfoot valgus, midfoot and/or forefoot abduction, and arch collapse deformities progressively increase from normal alignment to PCFD, significant subtalar joint subluxation and sinus tarsi impingement were unique to symptomatic PCFD. These findings suggest that PTS can serve as a crucial biomarker for diagnosing pathologic flatfoot (PCFD) and differentiating it from asymptomatic flatfoot. Future research should explore the predictive value of PTS biomarkers in identifying flatfoot at high risk for collapse and their impact on clinical management and surgical decision-making.Level of Evidence:Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

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: 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.

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.

Tarso-metatarsal joints and naviculocuneiform joints comprising midfoot is the second most commonly involved joints following the first metatarsophalangeal joint in the foot. However, related factors of midfoot arthritis (MA) have been rarely reported. The bony structure and alignment can be more precisely assessed using Weight-Bearing Computed Tomography (WBCT) than conventional radiographs. Therefore, the aim of this study was to investigate risk factors for MA related to medical history and comorbid foot deformities using WBCT. WBCT data from September 2014 to April 2022 were extracted from a single referral hospital. All cases were divided into two groups by the presence of MA. Twenty-five potential related factors including demographics, etiology, and common co-occurring foot deformities were collected for comparison. Six hundred six cases (247 males and 359 females) among consecutive 1316 cases between September 2014 to April 2022 were selected. One hundred thirty-nine male cases (56.3%) and 210 female cases (58.5%) showed MA. In stepwise multiple logistic regression analysis, 5 factors remained statistically significant. The multivariate-adjusted odds ratios for age, laterality, body mass index (BMI), Progressive Collapsing Foot Deformity (PCFD), and lesser toe deformities (LTD) were 1.08, 1.54, 1.05, 6.62, and 3.03 respectively. Risk factors for MA associated with medical history and foot deformities included age, laterality, BMI, PCFD, and LDT.

BACKGROUND:The Zadek osteotomy modified by Taylor (ZO) is a surgical technique used to treat insertional Achilles tendinopathy (IAT) by reducing the heel's prominence and elevating the Achilles tendon insertion. This study aims to analyze the biomechanical consequences of IAT after ZO using a virtual surgical simulation with a specific software. METHODS:A retrospective analysis of 20 wtbearing computed tomography (WBCT) scans of IAT patients was conducted. Using Disior's BonelogicTM software, 3D models were created from WBCT images. Virtual ZO was performed on these models, and various biomechanical parameters were measured before and after the virtual osteotomy. RESULTS:The virtual ZO showed significant statistical differences in the average of the calcaneal length (p < 0.001), Fowler Philips angle (p < 0.001), calcaneal pitch (p < 0.001), and the sagittal talocalcaneal angle (p < 0.001). CONCLUSIONS:The virtual ZO analysis suggests that this procedure can decrease the Fowler Philips angle, shorten the calcaneus, modifying specifically the sagittal alignment. LEVEL OF EVIDENCE:IV; case series.

Background: The outcomes of first metatarsal (M1) distal osteotomies in hallux valgus (HV) can be improved, especially for intermetatarsal angle (IMA) correction, which is mainly based on lateral displacement of the M1 head (i.e., translation) through the osteotomy. Conversely, there is a spontaneous reduction in the IMA in first metatarsophalangeal joint (MTP1) arthrodesis. But we do not know whether this can be applied to distal osteotomies. We propose a distal osteotomy, called 3D chevron, which combines supination and varization of the M1 head. This might realign soft tissues around the MTP1, potentially leading to a spontaneous reduction in the IMA by an analogous mechanism to MTP1 fusion. Therefore, our study aimed to assess whether spontaneous reductions in IMAs exist in distal M1 osteotomies in the absence of lateral translations of M1 heads. Methods: A prospective continuous series of 25 3D chevrons was performed. Two groups were formed during surgery. Patients requiring no M1 head lateral displacement were included in the “successful correction without translation” group, and patients requiring M1 head lateral displacement were included in the “failed correction without translation” group. Radiographic analysis was performed preoperatively and at 1 year postoperatively. Results: Twenty-two women and three men, with a mean age of 44.8 ± 14.2 years and a mean body mass index of 22.6 ± 4.1 kg/m2, underwent follow-up at one year after surgery. The “successful correction without translation” group was composed of HV with milder deformities (13/25 HVs, median preoperative IMA = 13 (IQR 2)) compared to the “failed correction without translation” group (median IMA = 16 (IQR 2.25) p < 0.001). Spontaneous reductions in IMAs were observed in the “successful correction without translation” group, with a median decrease in the IMA of 6 degrees (CI95%[5.5; 8.0]; p < 0.001) between preoperative and 1-year radiographs. Conclusion: Distal osteotomies allow for spontaneous reduction in the IMA in HV. First metatarsal head translation through an osteotomy should not be considered as the only procedure to correct IMAs in distal osteotomies.

BackgroundThe aim of this study was to investigate the epidemiology of Midfoot Arthritis (MA) and Lesser toe deformity (LTD) using Weight-Bearing Computed Tomography (WBCT).Methods606 cases (247 male, 359 female) among 1316 consecutive cases with WBCT data from September 2014 to April 2022 were retrospectively reviewed at a single referral institution. The Cochran-Armitage test was performed to evaluate the trend of prevalence with respect to age group and obesity classification.Results139 male (56.3%) and 210 female cases (58.5%) showed MA. 157 male (63.6%) and 222 female cases (61.6%) showed LTD. 115 male (19.0%) and 157 female cases (25.9%) showed both MA and LTD. The prevalence of MA and LTD increased with age in both genders. The incidence of MA in males showed an increasing tendency until obesity class II and then was slightly decreased in obesity class III. This is contrary to females whose prevalence increased with increasing obesity groups. LTD had a similar pattern in both genders to obesity classification.ConclusionsThe prevalence of MA and LTD increased with age and increasing obesity groups for both genders.Level of EvidenceLevel III, Retrospective Comparative Study.

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

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

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

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

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

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

Category: Midfoot/Forefoot; Basic Sciences/Biologics; Hindfoot Introduction/Purpose: A recent study published in Nature (Venkadesan et al.) demonstrated that coupling the transverse arch (TA) with the medial longitudinal arch (MLA) significantly increased midfoot intrinsic stiffness. The contribution of the TA is substantial, suggested as the evolutionary advancement providing the foot stiffness required for human bipedalism. Progressive collapsing foot deformity (PCFD) is a complex deformity ultimately resulting in loss of stiffness and collapse of the MLA. The novel understanding of the TA may play a key role in the pathogenesis of this deformity. The objectives of this study were to assess and compare the TA curvature in PCFD and controls and to evaluate its relationship with accepted PCFD measures. We hypothesized that the curvature of the TA will be decreased in PCFD. Methods: A retrospective review was conducted for 32 PCFD and 32 controls. Measurements were performed using weight- bearing CT (WBCT). A novel measurement, the transverse arch plantar (TAP) angle, was designed to directly measure the TA in both PCFD (Figure 1a) and controls (Figure 1b). TA curvature was calculated using the equation described by Venkadesan et al. (Figure 6) utilizing width, length (Figure 3a), 3rd metatarsal thickness (Figure 3b), and 4th metatarsal torsion (Figure 4a, 4b). Finally, uni- and multivariate analyses were performed to analyze the relationship between the TAP angle, Foot and Ankle Offset (FAO), peritalar subluxation, and measurements associated with PCFD classes: hindfoot moment arm (class A), talonavicular coverage angle (class B), Meary angle (class C), medial facet uncoverage angle (class D), and talar tilt (class E). Normality of different variables was assessed using the Shapiro-Wilk test. Two groups were compared using t-test for normal, and Mann-Whitney for non-normal variables. Results: Measurements of the TAP angle were found to be significantly higher in the PCFD group than the control group with a mean angle of 115.24° (SD 10.68) and 100.76° (SD 7.92) respectively (p<0.001) (Figure 2).No significant difference was found in the calculated TA curvature between PCFD and controls with mean values of 17.84 (SD 4.41) and 18.18 (SD 3.68) respectively (p=0.741) (Figure 5).The univariate analysis performed showed a moderate positive correlation between the TAP angle and the FAO (ρ=0.58;r2=0.34;p <0.001).The multivariate analyses showed, among the different PCFD class measurements and the TAP angle, only the middle facet uncoverage (β=0.08,p<0.001) and hindfoot moment arm (β=0.32, p<0.001) were associated with higher values of FAO, while only the Meary (β=0.49,p=0.004) and the talonavicular coverage angles were associated with higher values of peritalar subluxation (β=0.75,p<0.001). Whereas, Meary's angle was the only predictive factor of higher TA collapse (β=0.55,p<0.001). Conclusion: Our direct measurement showed a collapsed of the TA in PCFD. However, this did not appear to be a consequence of insufficient bone torsion, but rather some other etiology, possibly a soft tissue failure. Considering the implication of the TA among the different PCFD classes, it did not appear to play a significant role on the overall PCFD deformity. TA collapse seemed mainly influenced by Meary's angle, which assess the MLA. This further supports the idea behind TA and MLA coupling suggesting that when the TA is collapsed, the foot does not possess the required stiffness to maintain the MLA.

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.