Change in Axial Rotation of the Talus Following Reconstruction of the Progressive Collapsing Foot Deformity

Category: Hindfoot; Other Introduction/Purpose: In addition to peri-talar subluxation of the foot, previous studies have demonstrated that the talus is more internally rotated with respect to the trans-malleolar axis of the ankle in PCFD patients compared with normal patients. However, no studies have investigated the change in rotation of the talus in PCFD postoperatively and its association with outcomes. The primary aim of this study was to investigate the preoperative to postoperative change in rotation of the talus following reconstruction of the flexible PCFD. Secondary aims were to determine whether changes in rotation of the talus were associated with radiographic measurements of PCFD or specific reconstructive procedures and whether postoperative talar rotation was associated with two-year patient-reported outcome scores. Methods: Thirty-four consecutive patients over the age of 18 years old who underwent reconstruction of a flexible PCFD with preoperative and at least 5-month postoperative weightbearing CT (WBCT) scans and plain radiographs and had preoperative and at least two-year postoperative PROMIS scores were included in the study. Patients were excluded if they underwent a talonavicular fusion. Talar axial rotation was the angle between the transmalleolar axis and talar axis on preoperative and postoperative WBCT scans as previously described by Kim et al (2023) with smaller angles representing more internal rotation. Hindfoot moment arm, Meary’s angle, and talonavicular angle were measured on plain radiographs. Due to small sample sizes, descriptive statistics are reported as median and interquartile ranges (IQRs). Wilcoxon signed rank and Mann Whiney U tests were used to investigate differences between groups. Spearman correlation coefficients were employed to detect associations between variables and reported using 95% confidence intervals (95% CIs). Results: Median preoperative and postoperative talar axial rotation were 39.9° (IQR 36.7°, 45.3°) and 49.7° (IQR 45.9°, 57.3°, P < 0.001), respectively. The talus externally rotated by a median of 8.3° (IQR 4.1°, 13.1°) following surgery. The preoperative to postoperative change in talar rotation was not associated with changes in any plain radiographic parameter (Table 1). Increasing external rotation of the talus was associated with an increase in postoperative PROMIS Pain Intensity (rho=0.38, 95% CI 0.00, 0.67) with similar trends in the PROMIS Physical Function (rho=-0.22, 95% CI -0.55, 0.18) and Pain Interference (rho=0.19, 95% CI -0.21, 0.53) domains (Figure 1). Lateral column lengthening and subtalar fusion procedures were not associated with changes in talar rotation (both P > 0.10). Conclusion: Reconstruction of the flexible PCFD distal to the talus results in external rotation of the talus within the ankle mortise. Talar rotation was not associated with common measures of deformity or specific procedures. Kim et al. found that control patients had approximately 40°-60° of talar axial rotation, which is similar to the corrected position of the talus in our study. However, increasing talar external rotation resulted in worse postoperative PROMIS Pain Intensity scores with a similar trend seen in other PROMIS domains and raises the possibility of overcorrecting the internal rotational deformity of the talus in flexible PCFD.