Background: The extent to which excessive glenoid retroversion leads to increased glenohumeral contact pressures and whether these increases can be mitigated surgically is unknown.
Purpose: To evaluate the effect of excessive glenoid retroversion and posterior iliac crest bone grafting (ICBG) with or without glenoid osteotomy on glenohumeral contact patterns.
Study design: Controlled laboratory study.
Methods: 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).
Results: 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 (P < .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 (P > .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 (P < .05).
Conclusion: 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.
Clinical relevance: The combined effect of posterior glenoid bone grafting and correcting excessive glenoid retroversion (20°) may correct abnormal glenohumeral contact patterns.
Keywords: glenohumeral contact pressure; glenoid osteotomy; glenoid retroversion; posterior glenoid bone grafting; posterior shoulder instability.