Structures contributing to the shoulder contracture in brachial plexus birth palsy. An intraoperative biomechanical study.

Internal rotation contracture of the shoulder is a common sequel of the brachial plexus birth palsy. The purpose of this study is to describe the surgical method used in our centre and to measure the effect of sequentially releasing several anatomical structures that have been ascribed as the cause of the contracture. Twenty-four consecutive patients were operated on with an open release. We documented the increase in passive external rotation after each surgical step. We found small gains in passive external rotation when performing coracoidectomy and division of the upper part of the subscapularis tendon; 4° (95% confidence interval [CI] 2°-6° p < 0.01) and 6° (95% CI 4°-8° p < 0.01), respectively. A substantial gain in external rotation occurred when dividing the entire subscapularis tendon, 43° (95% CI 38°-48°, p < 0.01). Our findings indicate that a clinically relevant surgical release of the contracture requires lengthening of the entire subscapularis musculo-tendinous unit.Level of evidence: IV.