Radiologic findings for prediction of rehabilitation outcomes in patients with chronic symptomatic os subfibulare.

OBJECTIVE: To retrospectively evaluate the radiologic findings for predicting rehabilitation outcomes in patients with chronic symptomatic os subfibulare.

MATERIALS AND METHODS: 38 patients with chronic lateral ankle pain and os subfibulare underwent a standardized rehabilitation program. Rehabilitation outcome was evaluated after ≥3 months of intervention as the following: good response group (n = 20) without the need for further treatment and poor response group (n = 18) who underwent surgery after rehabilitation. Size, shape and location of os subfibulare, anterior talofibular ligament abnormality and attachment to the os subfibulare, interposition of fluid signal intensity between the os subfibulare and the fibula, and bone marrow edema in the os subfibulare on radiographs and MRI were evaluated by two radiologists blinded to rehabilitation outcomes and were compared between the two groups.

RESULTS: The mean size of os subfibulare was significantly different between good and poor response groups: 7 versus 12 mm (p < 0.01), respectively. The prevalence of interposition of fluid signal intensity between the os subfibulare and the fibula and bone marrow edema in the os subfibulare on MRI was significantly different between the two groups (p < 0.01). However, other radiologic findings were not significantly different (p ≥ 0.08). The optimal size to classify the two groups was 9 mm with sensitivity of 83.3% and specificity of 80%. Inter-observer reliability was good to excellent (ICC = 0.991 for size and kappa = 0.735-0.923 for others).

CONCLUSIONS: MRI may be used to predict rehabilitation outcome in patients with chronic symptomatic os subfibulare.