Conservative Treatment with Arch Support Inflatable Ankle-Foot Orthosis Does Not Correct Progressive Collapsing Foot Deformity: A Prospective Comparative and Controlled Study
Authors: Iehl Caleb J. , Mansur Nacime Salomao Barbachan , Carvalho Kepler A.M. , Tazegul Tutku , VandeLune Christian , Ahrenholz Samuel , McGettigan Lily , Dibbern Kevin , Schmidt Eli , Lalevee Matthieu , de Cesar Netto Cesar 
Published: December 2023

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.