Biomechanics of shoulder capsulorrhaphy procedures Christopher S. Ahmad, MD, a Vincent M. Wang, PhD, b Matthew T. Sugalski, MD, a William N. Levine, MD, a and Louis U. Bigliani, MD, a New York, NY Nonanatomic capsulorrhaphy procedures and recon- structions used to treat shoulder instability create me- chanical alterations to the glenohumeral joint that lead to eventual arthrosis. Current capsulorrhaphy proce- dures have evolved toward restoring normal anatomy and have stimulated relevant anatomic research. Anal- ysis of the subscapularis insertion has demonstrated a superior tendinous insertion and an inferior muscular insertion with the inferior glenohumeral capsule consis- tently located beneath the muscular insertion of the subscapularis. In addition, 2 types of inferior humeral capsular attachments have been identified. The ante- rior capsular insertion may bifurcate into a superior internal fold adjacent to the articular cartilage and an inferior external fold on the humeral surgical neck. Al- ternatively, 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 capsulor- rhaphy procedures. Biomechanical studies allow direct study of the different parameters involved in capsulor- rhaphy procedures, and several recent studies have improved our understanding. Anterior tightening pro- cedures such as the Putti-Platt or Magnuson-Stack pro- cedure, as well as a tight Bankart repair, result in a loss of external rotation and maximum elevation. Fur- thermore, this type of operative intervention creates greater posterior joint loads and abnormal posteroinfe- rior humeral head subluxation, leading to pain and arthrosis. Anatomic capsulorrhaphy procedures pro- duce more normal joint mechanics. Current and future studies will evaluate new arthroscopic capsulorrhaphy techniques. (J Shoulder Elbow Surg 2005;14: 12S-18S.) INTRODUCTION Long-term follow-up for nonanatomic surgical pro- cedures addressing shoulder instability such as the Putti-Platt and Magnuson-Stack procedure have dem- onstrated satisfactory stability; however, these proce- dures have often resulted in restricted motion. The mechanical alterations related to overconstraining the joint have led to progressive arthrosis in many clinical studies. 10,13,14,21-23 With this knowledge, advances in surgery for the treatment of glenohumeral instability have evolved toward procedures that restore normal anatomy. 1,2,11,18,31 Therefore, precise knowledge of normal capsular and labral anatomy, which are the primary pathologic elements involved in shoulder in- stability, must be clearly delineated. This knowledge will allow anatomic restoration that accurately bal- ances soft tissues and repairs labral defects as a means of eliminating the exact pathology that is en- countered. Many areas of controversy exist regarding the specific capsulorrhaphy techniques. Biomechani- cal studies have increased our understanding of these technique parameters and have elucidated the exact mechanisms that lead to post-capsulorrhaphy arthro- sis. 3,25 The following is a description of recent ad- vances in capsular anatomy and biomechanical eval- uation of capsulorrhaphy procedures. PATHOLOGY The exact pathology that contributes to shoulder instability has been a focus of significant research. Bankart lesions refer to detachment of the labrum corresponding to the anchoring point of the inferior glenohumeral and middle glenohumeral ligaments to the glenoid rim. These lesions have been considered the primary and most common pathology leading to recurrent anterior dislocations. Townley 29 then de- scribed capsular stretch injury as a component of the pathology. Biomechanical studies suggest, however, that dislocations require plastic deformation of the capsule in addition to the Bankart lesion. 24 Bigliani et al 5 studied the tensile properties of the inferior gleno- humeral ligament and observed significant stretch injury to the ligament before failure. Clinically, repet- itive stresses on the capsule that occur with recurrent subluxations or frank dislocations can cause cumula- tive stretching of the joint capsule beyond its physio- From the a Center for Shoulder, Elbow, and Sports Medicine, De- partment of Orthopaedic Surgery, Columbia University, and b Department of Orthopaedics, Mount Sinai School of Medicine. Reprint requests: Christopher S. Ahmad, MD, Department of Or- thopaedic Surgery, Columbia University, 622 W 168th St, PH-11th Center, New York, NY 10032. Copyright © 2005 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2005/$30.00 doi:10.1016/j.jse.2004.09.015 12S