2021 ISAKOS Biennial Congress Paper
Defining Critical Glenoid Bone Loss In Posterior Shoulder Capsulolabral Repair
Justin W. Arner, MD, Pittsburgh, PA UNITED STATES
Joseph J. Ruzbarsky, MD, Aspen, CO UNITED STATES
Kaare Midtgaard, MD, Oslo NORWAY
Liam A. Peebles, BA, Vail, CO UNITED STATES
James P. Bradley, MD, Pittsburgh, PA UNITED STATES
Matthew T. Provencher, MD, Vail, CO UNITED STATES
The Steadman Clinic, Vail, CO, UNITED STATES
FDA Status Not Applicable
Summary
Risk factors for failure of arthroscopic posterior shoulder capsulolabral repair include smaller glenoid bone width and greater glenoid bone loss percentage. A threshold of 11% posterior glenoid bone loss implicated a 10 times higher surgical failure rate while a threshold of 15% lead to a 25 times higher surgical failure rate.
Abstract
Background
Although critical bone loss for anterior instability is well defined, a clinically significant threshold of posterior bone loss has not been elucidated.
Hypothesis
Patients who fail arthroscopic posterior shoulder capsulolabral repair will have increased posterior glenoid bone loss with a defined critical threshold.
Study Design: Case-Control
Methods
Athletes greater than 18 years of age with unidirectional posterior instability treated with arthroscopic repair were evaluated at 2 year minimum follow-up. Failure was defined as revision surgery, ASES <60, or subjective stability score >5. MRIs measurements from 19 patients who failed arthroscopic posterior shoulder capsulolabral repair were compared with 56 patients who did not. MRIs measures included glenoid version, labral version, glenoid width, labral width, percent bone loss using the circle technique, labral height, percent subluxation, and recently described measures of defect slope, bone loss angle, and defect length. The p-value threshold was set at 0.05 and a multivariable logistic regression analysis was performed for evaluation of risk of surgical failure.
Results
Smaller glenoid width and greater percent glenoid bone loss (25.5 + 0.68 mm vs 28.8 + 0.47 mm, p<0.001; 6.8 + 0.64% vs 4.6 + 0.43%, p=0.008) was seen in those that failed surgery. There was no difference in glenoid version or other measurements between the failures and non-failures. A cutoff of 11% glenoid bone loss resulted in a 10 times statistically higher surgical failure rate, while 15% bone loss resulted in a 25 times statistically higher failure rate. Six patients had bone loss greater than 11% (range, 11.1 - 19.3) and 1 patient had greater than 15% bone loss
Conclusion
Risk factors for failure of arthroscopic posterior shoulder capsulolabral repair include smaller glenoid bone width and greater glenoid bone loss percentage. A threshold of 11% posterior glenoid bone loss implicated a 10 times higher surgical failure rate while a threshold of 15% lead to a 25 times higher surgical failure rate. Surgical failure of posterior capsulolabral repair, however, is relatively rare as it is an overall successful intervention.