Occurrence of Lateral Ankle Ligament Disease With Stage 2 to 3 Adult-Acquired Flatfoot Deformity Confirmed via Magnetic Resonance Imaging: A Retrospective Study.

Lateral hindfoot pain associated with stage 2 to 3 adult-acquired flatfoot is often attributed to subfibular impingement. Preoperative magnetic resonance imaging (MRI) is generally performed to assess the extent of degeneration within the posterior tibial tendon, attenuation of medial soft tissue constraints, and degeneration of hindfoot and/or ankle articulations. The purpose of this study is to determine the incidence of lateral collateral ligament disease/injury associated with stages 2 and 3 adult-acquired flatfoot. The subjects were identified using a searchable computerized hospital database between 2015 and 2017. Stage 2 or 3 adult-acquired flatfoot deformity was confirmed in patients via chart review and MRI analysis. Lateral ankle ligament injury was confirmed using patient MRI results per the hospital radiologist and documented within the patients' chart. Inclusion criteria required that patients be diagnosed with Johnson and Strom stage 2 or 3 flatfoot deformity with documented lateral ankle pain and that preoperative MRI scans be available with the radiologist's report. Patient exclusion criteria included patients <18 years of age, patients with flatfoot deformity caused by previous trauma, tarsal coalition, neuropathic arthritis, patients with previous surgery, or patients with incomplete medical records. In total, 118 patients were identified with these parameters. Of the 118 patients, 74 patients (62.7%) had documented lateral ankle ligament injury on MRI. Of the 77 patients with stage 2 adult-acquired flatfoot, 55 (71.4%) had confirmed lateral ankle ligament injury on MRI. Of the 41 patients with stage 3 adult-acquired flatfoot, 19 (46.3%) had confirmed lateral ankle ligament injury on MRI. This study demonstrates a relatively high incidence of lateral ligament disease associated with adult-acquired flatfoot deformity. These findings might have long-term implications regarding ankle arthritis after surgical management of adult-acquired flatfoot.