Septic arthritis of the shoulder in children may result in deformity of the proximal humerus, humeral shortening or subluxation of the shoulder joint; however, there are very few reports with a long-term follow-up. The purpose of this study was to clarify a sequel of septic arthritis in infants. Sixteen shoulders in 15 patients were retrospectively evaluated from clinical records and plane radiographs. Follow-up terms ranged from 5.0to 17.9 years (average: 11.3 years). The average age at first onset and final X-ray examination was 0.8 years old and 11.6 years old, respectively. Arthrotomy was performed in 6 shoulders (Group A) within 10 days after the first onset. Of the remaining 10 shoulders,4 shoulders (Group B) were treated with arthrotomy more than 10days after first onset and 6 shoulders (Group C) were managed conservatively with needle aspiration and intravenous antibiotics. The mean follow-up terms were 11.0,11.9 and 11.3 yeas in Group A, B and C, respectively. In the latest follow-up radiographs, deformity of proximal humerus was identified in 2 humeri in Group A,4 in Group B and 5 in Group C. Inferior subluxation of the shoulder was not observed in Group A, however, it was observed in 2 shoulders in Group B and 3 in Group C. The mean discrepancy of the humeral length at final X-rays were 0.1 cm,3.2 cm and 5.3 cm in Group A, B and C, respectively. The difference between Group A and C was statistically significant (ANOVA combined with Fisher's PLSD: p=0.014). Humeral shortening was related to inferior subluxation and 3cm-shortening seemed to be critical in these cases. Early drainage by arthrotomy was necessary to avoid humeral shortening and consequent subluxation of the shoulder.
