Identifying the Optimal Placement for Evans and Hintermann Lateral Column Lengthening (LCL) Osteotomies in Progressive Collapsing Foot Deformity (PCFD)

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: In the treatment of Progressive Collapsing Foot Deformity (PCFD), Lateral Column Lengthening (LCL) osteotomies are commonly performed. Two popular techniques for this procedure are the Evans (EO) and Hintermann osteotomy (HO). The EO involves a parallel cut 10-14mm proximal to the calcaneocuboid joint (CCJ), between the anterior facet (AF) and middle facet (MF). The HO starts at the angle of Gissane and runs obliquely between the MF and posterior facet (PF). However, due to anatomical variations in the calcaneus and articular facets, the entry point for LCL can vary, leading to frequent iatrogenic injury to the articular facets. This study aimed to identify a single ideal entry point for LCL that would allow for reliable cuts between the anterior/middle or middle/posterior facets. Methods: Retrospective-cohort study with a total 70 consecutive PCFD patients (70 feet, 35 females/35 males, mean age 47 years ±4) that underwent weightbearing CT (WBCT). The calcaneus was segmented semi-automatically. Only calcanei with independent AF and MF were utilized. AF, MF and PF were identified and marked. Two points were identified initially: entry-points for classic EO (12.5mm proximal to CCJ) and HO (Angle of Gissane). The distance between the CCJ and the Angle of Gissane, as well as the angles between HO entry-point and the edges of AF/MF and MF/PF were measured. We then determined the location of an ideal entry-point in the lateral wall of the calcaneus, that would optimize the angulation tolerance for performing either an EO (between AF/MF) or HO (between MF/PF) for each individual patient. To calculate that we utilized the optimum yields of the largest minimum tolerance statistics. Measurements were reported utilizing descriptive statistics. Results: By utilizing the traditional EO point and angulation (12.5mm proximal to CCJ), 91% of MF would be injured. HO entry-point (Angle of Gissane) was found to be positioned on average 20.1mm±2.7mm (range, 13.7-26.8mm) posterior to the CCJ. Utilizing the HO entry-point, cuts could be performed in between AF/MF and MF/PF, with an average angulation range of respectively 7.5o±1.6o (18o anterior margin/25.6o posterior margin) and -6.8o±2.6o (-3.8o anterior margin/-10.7o posterior margin). The ideal entry-point was found to be positioned on average 19.4mm±3mm posteriorly to the CCJ and just 0.7mm±2.5mm anteriorly to the angle of Gissane (HO point). The average angulation ranges from the ideal entry-point to AF/MF was 7.4o±1.4o (16.8o anterior margin/24.2o posterior margin) and to MF/PF -7.4o±1.4o (-4.6o anterior margin/-12.1o posterior margin). Conclusion: This study identifies an ideal entry-point for lateral column lengthening (LCL) osteotomies that maximizes angulation tolerance while minimizing the risk of iatrogenic injury to the articular facets. The proposed entry-point, located on average 19.4mm posterior to the CCJ and slightly anterior to the Angle of Gissane, offers a more reliable approach for positioning the osteotomy line in between the anterior and middle facets or between the middle and posterior facets. These findings provide valuable guidance for surgical planning in Progressive Collapsing Foot Deformity (PCFD) and may contribute to optimize accuracy for LCL osteotomies and to improve patient outcomes. Schematic drawings of a 3D rendering of calcaneus from weightbearing CT imaging, demonstrating the anterior, middle and posterior facets of the subtalar joint, the calcaneocuboid joint line, the point of the angle of gissane (hintermann osteotomy classic entry-point) and the identified ideal entry-point for a lateral column lengthening osteotomy, maximizing the range of angulations allowed to be utilized, avoiding iatrogenic injuries to the subtalar joint articular facets.