Progressive Collapsing Foot Deformity Correction using Longitudinal Arch Support Inflatable Ankle- Foot Orthosis: A Prospective Case-Control Study

Abstract

Category: Midfoot/Forefoot; Ankle; Hindfoot Introduction/Purpose: Progressive Collapsing Foot Deformity (PCFD) comprises five independent deformities represented by five classes: hindfoot valgus (class A), midfoot abduction (class B), forefoot varus (class C), peritalar subluxation (class D) and ankle valgus (class E). Conservative treatment includes the use of corrective insoles and orthotics. Longitudinal arch support inflatable ankle-foot orthoses (IAFO) help control pain in PCFD patients. But we have no knowledge about the ability of IAFOs to correct deformities in PCFD. The aim of this prospective case-controlled study was to assess the ability of longitudinal arch support IAFOs to correct 3D overall PCFD alignment as well as the five different PCFD classes independently. We hypothesized that IAFOs will correct PCFD 3D overall alignment as well as the five independent classes. Methods: After IRB approval we enrolled 24 symptomatic flexible PCFD and 24 controls matched on age, sex, and BMI. Patients were scanned using Weight-Bearing CT with and without a longitudinal 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 the distance between the floor and the medial cuneiform (C1-floor) for the Class C and the middle facet uncoverage (MFunco, Class D). We did not have any Class E deformity in our PCFD cohort. Data normality was assessed by Shapiro-Wilk test. Comparisons used normality based paired T-tests or paired-Wilcoxon tests. Hypothesizing that the IAFOs would be two times less efficient than the surgery (Day et al.) in correcting the FAO in PCFD, the requisite number of subjects was 24 per group. Results: Control measurements were all significantly different than unbraced PCFD measurements confirming our PCFD selection process. Comparing PCFD without and with IAFO via 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) did not show any significant improvement when applying the IAFOs. The Meary's angle (17.6+/-7.2 vs 10.8+/-7.3, p=0.002) and the C1-floor (17.2+/-3.3mm vs 24.1+/-5.3mm, p<0.001) were significantly improved by the IAFOs. The only measurements which was normalized when compare the PCFD to the control group after applying the IAFO 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 case-control study, we found that longitudinal arch support IAFOs were less than half as effective as surgery in correcting overall 3D deformity in PCFD. Likewise, IAFOs were not efficient in correcting hindfoot valgus (Class A), midfoot abduction (Class B) and peritalar subluxation (Class D) in PCFD. On the other, IAFOs were effective in correcting forefoot varus and medial longitudinal arch collapse (Class C). This study provides relevant information to guide medical treatment and longitudinal arch support IAFO prescription in PCFD.