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° of
retroversion. Two humeral versions were tested for each specimen: anatomic
version and 15° 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° 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.
Clinical Relevance: These data further suggest that restoring a more
neutral glenoid surface might be preferred when the surgeon is presented with
posterior glenoid bone loss.