The effect of humeral component anteversion on shoulder stability with glenoid component retroversion

BACKGROUND: Posterior glenoid bone loss is often seen in association with glenohumeral osteoarthritis. This posterior asymmetric wear can lead to retroversion of the glenoid component and posterior instability after total shoulder arthroplasty. Options for the treatment of this asymmetric wear include eccentric reaming of the so-called high side, bone-grafting, and/or anteverting the humeral component. Although anteverting the humeral component has been advocated by many, it has not been substantiated on the basis of biomechanical data. The purpose of the present study was to determine whether anteverting the humeral component increases the stability of a total shoulder replacement with a retroverted glenoid component. METHODS: A total shoulder arthroplasty was performed in eight human cadaveric shoulders. The glenoid component was placed in 15 degrees of retroversion. Two humeral versions were tested for each specimen: anatomic version and 15 degrees of anteversion relative to anatomic version. The specimens were mounted supine in a custom fixture on a servohydraulic testing system. The humerus was translated posteriorly by one-half of the width of the glenoid. Three positions of humeral rotation were tested for each position of humeral version. Both the energy and the peak load were analyzed as measures of joint stability. RESULTS: There was no significant difference in either energy or peak load between the tests performed with the humeral component in 15 degrees of anteversion and those performed with the component in anatomic version in any of the three rotational positions (p > 0.05). CONCLUSIONS: Although anteverting the humeral component during total shoulder arthroplasty to compensate for glenoid retroversion has been advocated, these data suggest that compensatory anteversion of the humeral component does not increase the stability of a shoulder replacement with a retroverted glenoid component.