Surgical Correction of Peritalar Subluxation and Patient Reported Outcomes: A Prospective Comparative Outcome Study in Flexible Progressive Collapsing Foot Deformity

Abstract

Category: Ankle; Hindfoot; Other Introduction/Purpose: Peritalar subluxation (PTS) of the hindfoot is a critical finding in Progressive Collapsing Foot Deformity (PCFD). Subluxation of the middle facet and sinus tarsi impingement have recently been shown to represent essential markers of pronounced and potentially progressive deformity. Weightbearing CT (WBCT) imaging and three-dimensional (3D) distance (DM) and coverage maps (CM) allow a complete and accurate assessment of PTS markers across the entire peritalar surface. This prospective comparative study aimed to assess the effectiveness of joint-sparing realignment surgical treatment for flexible PCFD in reducing PTS and to correlate the improvement with patient-reported outcomes (PROs). We hypothesized that surgical treatment would significantly improve PTS markers, mainly decreasing sinus tarsi coverage/impingement and middle facet subluxation, and that this improvement would correlate with increased PROs. Methods: In this IRB-approved prospective and comparative study, we enrolled patients with flexible PCFD, no prior surgeries, and failed conservative treatment. Included patients (n=10, 7 females/3 males, mean age 57.2, range 37-74) underwent joint-sparing surgical realignment procedure by a single surgeon. Standing weightbearing CT (WBCT) was completed preoperatively and 3- months postoperatively. Following automatic bone segmentation, 3D distance maps (DMs) of the entire peritalar surface were generated, and coverage of the subtalar joint articular facets (anterior, middle, and posterior) and sinus tarsi were assessed as markers of PTS. Joint coverage was defined as the percentage of articular space where DMs were <5 mm. Coverage Maps (CM) were built highlighting areas of adequate joint interaction (blue), joint subluxation (pink), and impingement (red). PROs were evaluated preoperatively and at the latest follow-up. Differences between preop/postop measurements and PROs were assessed by independent t-tests/Wilcoxon and bivariate analysis. P-values <.05 were considered significant. Results: The overall follow-up was 8.2 months (6-13 months). Medial displacement calcaneal osteotomies, lateral column lengthening, and first ray realignment procedures (either Cotton osteotomy or Lapidus) were performed in all patients. Foot and Ankle Offset significantly improved from 10.6% preoperatively to 3.1% postoperatively (p=0.0005), on average. Significant averaged improvement was also observed in anterior facet joint coverage (61.6%), as well as a reduction in sinus tarsi coverage/impingement (-43.2%) (both p<0.001). Middle (19.5%, p=0.08) and posterior facet joint coverage (3.5%, p=0.06) also demonstrated improvements, however not significant. PROs improved significantly on average postoperatively, with the European Foot and Ankle Surgery (EFAS) Score increasing from 3.1 to 7.3 (p=0.02) and the Foot Function Index (FFI) improving from 71.5 to 48.7 (p=0.01). Improvements in EFAS scores and FFI significantly correlated with improvements in middle facet coverage (R2 0.89, p=0.0154) and anterior facet coverage (R2 0.80, p=0.04), respectively. Conclusion: Our study was the first to evaluate WBCT 3D distance mapping's role in the assessment of surgical correction of PTS in patients with PCFD. We found significant improvements in subtalar joint anterior facet coverage and sinus tarsi impingement following surgical reconstruction, with a trend to significant improvements in middle and posterior facet joint coverage. More importantly, improvements in middle and anterior facet coverage correlated significantly with improved PROs (EFAS score and FFI, respectively). Based on our study results, optimization of subtalar joint coverage and reduction of PTS should be goals of surgical treatment of PCFD patients.