Radiologic Progression of Talar Osteochondral Lesions With Subchondral Cyst: A Median 98-Month Observational Study

Background: This retrospective observational cohort study aims to evaluate long-term radiologic progression in nonoperatively managed cystic osteochondral lesions of the talus (OLT), and to (1) identify predictors of radiologic cyst progression, particularly related to subchondral bony integrity, and (2) examine whether radiologic progression is dissociated from changes in clinical outcomes. Methods Among 78 cases of OLT with subchondral cysts, 56 patients treated non-operatively for a median of 98 months (>6 years) were included and categorized into 3 groups based on the annual rate of cyst volume change (mm 3 /y): (1) increased, (2) not changed, and (3) decreased. Factors were assessed using standing ankle radiographs, computed tomography, and magnetic resonance imaging. Additionally, the correlation between radiologic progression and clinical outcomes was analyzed. Results: Approximately three-quarters of patients clustered around minimal change, with less than an 8-mm 3 /y increase or even a decrease in cyst volume, and the median annual cyst volume change for the entire cohort was only 0.3 mm 3 /y. In contrast, cases in the upper quartile of the distribution demonstrated substantially faster cyst enlargement, with a mean annual increase of approximately 137 mm 3 /y. The ±8-mm 3 /y thresholds corresponded to the 25th and 75th percentiles of the annual cyst volume change distribution and were used to define radiologic progression groups. Multivariable regression analysis identified 3 significant factors: larger initial cyst volume (odds ratio [OR] 1.002, 95% CI: 1.000-1.004, P = .03), bone marrow (BM) edema (OR 10.189, 95% CI: 1.68-61.97, P = .012), and wall breakage (OR 16.942, 95% CI: 2.73-105.35, P = .002). However, cyst size progression showed no correlation with clinical symptoms ( P > .05). Notably, none of the cases progressed to OA. Conclusion A substantial number of OLT with subchondral cysts demonstrated radiologic stability, spontaneous reduction, or slow progression in cyst volume during long-term observation. We found no correlation between changes in cyst size and clinical symptoms.