Risks of loosening of a prosthetic glenoid implanted in retroversion (original) (raw)

2006, Journal of Shoulder and Elbow Surgery

Osteoarthritis of the shoulder is frequently associated with posterior glenoid wear, which may be difficult to correct during shoulder arthroplasty. This study was designed to evaluate the risks that a prosthetic glenoid implanted in retroversion will loosen. The scapula, the humerus, the rotator cuff, and a total shoulder prosthesis were reconstructed with a 3-dimensional finite element model. The glenoid was placed in 5 different angles of retroversion (0°, 5°, 10°, 15°, and 20°). Location of the glenohumeral contact point, articular pressure, bone and cement stress, and micromotion around the glenoid implant were calculated during internal and external rotation. Glenoid retroversion induced a posterior displacement of the glenohumeral contact point during internal and external rotation, inducing a significant increase of stress within the cement mantel (ϩ326%) and within the glenoid bone (ϩ162%). Furthermore, a major increase of micromotion was measured at the bone-cement interface (ϩ706%). According to this study, glenoid retroversion exceeding 10°should be corrected during total shoulder arthroplasty. If the correction is impossible, not replacing the glenoid should be considered. (J Shoulder Elbow Surg 2006;15:521-526.) Osteoarthritis of the shoulder is frequently associated with posterior glenoid wear. 6,15,23 The reasons remain unclear, but are probably multifactorial. The excessive stiffness of the anterior soft tissues after previous surgical procedures performed through an anterior approach is classically recognized as a cause of posterior glenoid erosion. 1,7,13 Posterior glenoid wear is also frequently seen without any previous surgery, however. In recent years, primary glenoid dysplasia, associated with increased glenoid retroversion and sometimes with a static posterior subluxation, has also been evoked as a cause of shoulder osteoarthritis. 24,25 Among the other possible causes, the effects of muscular imbalance (eg, in association with neurologic problems) and the influence of the humeral side of the joint (especially retroversion of the humeral head) are less frequently reported.