Correcting Excessive Glenoid Retroversion in Combination With Posterior Glenoid Bone Grafting Leads to Improved Glenohumeral Contact Pressures in a Cadaveric Posterior Instability Model.

Abstract

The extent to which excessive glenoid retroversion leads to increased glenohumeral contact pressures and whether these increases can be mitigated surgically is unknown. To evaluate the effect of excessive glenoid retroversion and posterior iliac crest bone grafting (ICBG) with or without glenoid osteotomy on glenohumeral contact patterns. Controlled laboratory study. Six fresh-frozen shoulders had a posterior open-wedge glenoid osteotomy allowing glenoid retroversion to be set at 0°, 10°, and 20°. Four conditions were simulated consecutively on the same specimen at each retroversion angle: intact glenohumeral joint, posterior Bankart lesion, 20% posterior glenoid deficiency, and posterior ICBG (at 20° of retroversion; corrected to 10° and 0° of retroversion). The contact pattern for each specimen was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring mean and peak contact pressures (megapascals), peak contact pressure distance (millimeters), and mean contact area (square millimeters). In the intact condition, retroversion of 20° resulted in a significant decrease in contact area but did not significantly affect contact pressure. Creating a posterior Bankart lesion and/or posterior glenoid deficiency showed a significant increase in mean and peak contact pressure at all 3 retroversion angles (<i>P</i> < .05). Correcting glenoid retroversion to 0° in combination with ICBG resulted in comparable contact area and mean and peak contact pressure of the intact condition (<i>P</i> > .05). At 10° and 20° of glenoid retroversion, ICBG resulted in significantly higher peak and mean contact pressure (mean not significantly different at 10°) and significantly lower contact area as compared with the intact condition (<i>P</i> < .05). Glenohumeral contact patterns highly depend on the amount of glenoid retroversion and posterior labral and/or bony glenoid integrity. Only the combination of ICBG and glenoid osteotomy to correct glenoid retroversion to 0° resulted in glenohumeral contact patterns comparable to the native condition with 0° of retroversion. The combined effect of posterior glenoid bone grafting and correcting excessive glenoid retroversion (20°) may correct abnormal glenohumeral contact patterns.