Shoulder exostoses in hereditary multiple exostoses: probability of surgery and malignant change

Abstract

Hypothesis: Patients with hereditary multiple exostoses (HME) in association with palpable shoulder exostoses are more severely affected by their disease.

Materials and methods: From a prospective database of 78 families with HME identified, 172 patients were identified. Demographic details, deformity, functional scores, standing height, number of exostoses, site, exostosin genotype (EXT1 and EXT2), surgical excision, and malignant change were recorded. Nonparametric tests were used to compare patients with and without shoulder exostoses (clavicle, scapula, and humerus).

Results: There were 5361 palpable exostoses, of which 14% were of the shoulder and were present in 145 patients (84.3%). There was a younger mean age (26.8 vs 37.9 years) and a male predominance in those individuals with shoulder exostoses (P = .0005). Patients with shoulder exostoses had significantly worse disease (P < .05). EXT1 mutations were more commonly observed in those with shoulder exostoses (odds ratio [OR], 20.6; 95% confidence interval [CI], 11.2-28.5; P = .001). The likelihood of surgical excision was greater in those with shoulder exostoses (OR, 2.8) and highest for scapular exostoses (OR, 3.7). Risk factors for surgical excision of shoulder exostoses were younger age (P = .03) and male gender (P < .008). Seven chondrosarcomas occurred, 2 scapular and a proximal humeral. The probability of malignant change of was highest for palpable scapular exostoses relative to any other anatomic site (OR, 12.3; P = .05).

Conclusion: Shoulder exostoses have a male predominance, and patients are more likely to have an EXT1 mutation. The presence of shoulder exostoses could serve as a tool to identify those individuals at high probability of malignant change.

Discussion: The existence of shoulder exostoses identifies those individuals with a high probability of having an EXT1 genotype (OR 20.6, 94.4% sensitivity, 84.8% positive predictive value), which is associated with sarcomatous change.