Multifactorial retrospective analysis of pathological fracture risk and treatment strategies in unicameral bone cysts

Abstract

Unicameral bone cysts (UBCs) are benign fluid-filled bone lesions that primarily affect children and adolescents and carry a clinically relevant risk of pathological fracture. This study explored radiological and clinical variables associated with fracture and recurrence in a histologically confirmed retrospective cohort. Seventy-two patients with histologically confirmed UBCs treated between 2010 and 2021 were retrospectively analysed. Median follow-up was 38 months (range 24-132). Primary outcomes were pathological fracture and radiological recurrence. Because only eight fractures were observed, multivariable analyses were treated as exploratory. Pathological fractures occurred in 8/72 patients (11.1%). Fracture rates were 0/46 (0%), 2/20 (10%) and 6/6 (100%) for Capanna stages 1, 2 and 3, respectively (p < 0.001). Latent cysts had a higher fracture rate than active cysts (21.4% vs 4.5%; p = 0.049). Recurrence occurred in 7/71 evaluable patients (9.9%), exclusively in the interventional group (7/23, 30.4% vs 0/48; p < 0.001). In this retrospective, histologically selected cohort, higher Capanna stage, younger age, latent activity and diaphyseal localisation were associated with fracture risk. Given the limited number of fracture events, the mixed paediatric-adult population and the selection bias inherent to histological inclusion, these findings are best interpreted as exploratory and hypothesis-generating. Overall, they may be more compatible with structured, individualised risk assessment than with a prescriptive Capanna-guided treatment algorithm.