Natural history of solitary osteochondroma

Aims: The aim of this study was to analyze the natural history of solitary osteochondroma and determine how skeletal maturity influences tumour behaviour and treatment outcomes. Methods: A retrospective analysis of 236 patients with solitary osteochondroma (151 skeletally immature, 85 skeletally mature) was undertaken. Skeletal maturity was defined as bone age ≥ 18 years in males and ≥ 17 years in females. Tumour characteristics, disease progression, indications for surgery and recurrence rates were evaluated. Interobserver reliability for bone age assessment was excellent (intraclass correlation coefficient (ICC) 0.92 (95% CI 0.88 to 0.95)). Results: Spontaneous regression occurred exclusively in skeletally immature patients (17.2% (n = 26) vs 0%; p < 0.001). Skeletally immature patients predominantly presented with sessile lesions (76.2%; n = 115), had lower surgical needs (31.8%; n = 48), but higher progression rates (9.9% (n = 15) vs 1.2% (n = 1); p = 0.013). Skeletally mature patients showed more stable disease but required surgery more often (54.1%; n = 46). Among skeletally immature patients with regression, independent predictors were younger age at diagnosis (odds ratio (OR) 0.82 (95% CI 0.73 to 0.92); p < 0.001), proximal humeral location (OR 10.59 (95% CI 2.01 to 55.85); p = 0.005), and humeral shaft location (OR 38.93 (95% CI 4.81 to 315.10); p = 0.001). The optimal cutoff age for regression prediction was 14.8 years. No local recurrence occurred in the 94 operated patients. Conclusion: Skeletal maturity fundamentally determines the natural history of osteochondroma. Conservative management with serial radiological follow-up is recommended for young patients, particularly those with humeral lesions, given their substantial potential for spontaneous regression. Earlier surgical intervention should be considered for skeletally mature patients with persistent symptoms.