The Incidence of Subtalar Facet Penetration and Its Impact on Clinical and Radiographic Outcome in Lateral Lengthening Calcaneal Osteotomies

BACKGROUND: Lateral lengthening calcaneal osteotomy (LLOT, Evans and Hintermann) is widely used to treat progressive collapsing foot deformity (PCFD). In the Evans osteotomy, the cut is performed proximal to the calcaneocuboid joint, carrying a risk of violating the anterior or middle subtalar facet. Hintermann proposed a modified technique placing the osteotomy between the middle and posterior facets to reduce risks. Although anatomical studies have shown potential facet involvement, clinical data on the actual incidence and its impact on long-term outcomes remain scarce. This study aimed to determine the incidence of subtalar facet penetration after LLOT and to evaluate its effect on clinical and radiographic results. METHODS: All patients aged ≥18 years who underwent LLOT (Evans or Hintermann osteotomy) at our institution between January 1, 2010, and December 31, 2020, were included. Postoperative computed tomography (CT) was performed 6 weeks after surgery to assess possible subtalar facet violation. At a minimum follow-up of 5 years, magnetic resonance imaging (MRI) was obtained to evaluate cartilage and ligament integrity. Clinical outcomes at the time of MRI were assessed using the Foot Function Index (FFI) and the American Orthopaedic Foot & Ankle Society (AOFAS) score. Demographic variables, including type of osteotomy and outcome measures, were compared between patients with and without facet penetration. RESULTS: Thirty-one patients met inclusion criteria. Subtalar facet penetration was detected in 11 patients (35%) on postoperative CT. No significant differences were observed between groups with respect to demographic variables. MRI analysis revealed no relevant differences in cartilage degeneration. FFI and AOFAS scores were comparable between groups. CONCLUSION: Subtalar facet penetration occurred in one-third of patients after LLOT (Evans and Hintermann). With the numbers available, no significant differences in clinical or radiographic outcomes were detected at a minimum 5-year follow-up, suggesting that minor facet violations may have limited clinical relevance. LEVEL OF EVIDENCE: Level III, retrospective cohort study.