Biomechanics of shoulder capsulorrhaphy procedures

Abstract

Nonanatomic capsulorrhaphy procedures and reconstructions used to treat shoulder instability create mechanical alterations to the glenohumeral joint that lead to eventual arthrosis. Current capsulorrhaphy procedures have evolved toward restoring normal anatomy and have stimulated relevant anatomic research. Analysis of the subscapularis insertion has demonstrated a superior tendinous insertion and an inferior muscular insertion with the inferior glenohumeral capsule consistently located beneath the muscular insertion of the subscapularis. In addition, 2 types of inferior humeral capsular attachments have been identified. The anterior capsular insertion may bifurcate into a superior internal fold adjacent to the articular cartilage and an inferior external fold on the humeral surgical neck. Alternatively, the capsule may insert over a broad area on the surgical neck. Therefore, releasing the muscular portion of the subscapularis and both capsular folds or the entire broad capsular insertion enhances proper shifting of the capsule during laterally based capsulorrhaphy procedures. Biomechanical studies allow direct study of the different parameters involved in capsulorrhaphy procedures, and several recent studies have improved our understanding. Anterior tightening procedures such as the Putti-Platt or Magnuson-Stack procedure, as well as a tight Bankart repair, result in a loss of external rotation and maximum elevation. Furthermore, this type of operative intervention creates greater posterior joint loads and abnormal posteroinferior humeral head subluxation, leading to pain and arthrosis. Anatomic capsulorrhaphy procedures produce more normal joint mechanics. Current and future studies will evaluate new arthroscopic capsulorrhaphy techniques.