Assessment of lateral hindfoot pain in acquired flatfoot deformity using weightbearing multiplanar imaging

Background: The etiology of lateral hindfoot pain in flatfoot deformity can be difficult to assess on plain radiographs. We hypothesized that multiplanar measurements obtained in a fully upright, weightbearing position would reliably demonstrate an increase in lateral hindfoot arthrosis and/or impingement in a cohort of flatfoot patients with lateral hindfoot pain compared to a cohort without pain. Materials and Methods: Ten consecutive patients with flexible flatfoot deformity and lateral hindfoot pain (mean age, 55.5 ± 13.9) were compared to 10 consecutive patients with flexible deformity but no pain (mean age, 61.0 ± 8.6). Conventional radiographs and weightbearing multiplanar images were performed on all patients before surgical reconstruction. Flatfoot, hindfoot impingement, and arthrosis parameters were interpreted in a blinded fashion by two musculoskeletal radiologists. Interrater reliability was determined with intraclass correlation coefficients (ICC). All parameters were compared between groups with a Wilcoxon rank sum test (p < 0.05). Results: A significant increase in posterior facet subtalar arthrosis (p = 0.006) and combined anterior and posterior facet subtalar arthrosis (p = 0.022) was evident in the pain group. Calcaneofibular impingement and calcaneocuboid arthritis were increased in the pain group, but did not reach significance (p = 0.057 and p = 0.067 respectively). The multiplanar imaging parameters demonstrated good (ICC = 0.60 to 0.73) to excellent (ICC ≥ 0.74) reliability for most impingement and arthrosis parameters and for many of the standard flatfoot parameters. Conclusion: The results indicate that weightbearing, multiplanar imaging provides a reliable means of assessing lateral pain in patients with flexible flatfoot deformity.