2015 ISAKOS Biennial Congress ePoster #2306

Characterization of Posterior Glenoid Bone Loss

Adam B. Yanke, MD, Chicago, IL UNITED STATES
Rachel M. Frank, MD, Aurora, CO UNITED STATES
Jason J. Shin, MD, Moose Jaw, SK CANADA
Geoffrey S. Van Thiel, MD, MBA, Chicago, IL UNITED STATES
Nikhil N. Verma, MD, Chicago, IL UNITED STATES
Brian J. Cole, MD, MBA, Chicago, IL UNITED STATES
Anthony A. Romeo, MD, Scarsdale, NY UNITED STATES
Matthew T. Provencher, MD, Vail, CO UNITED STATES

Rush University, Chicago, IL, USA

FDA Status Not Applicable

Summary: Accurate description of posterior bone loss will lead to more accurate cadaveric models, aid in developing new techniques for osseous augmentation like distal tibia allograft,7 and ideally improve our ability to obtain satisfying clinical outcomes.

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Abstract:

Introduction

Anterior glenohumeral instability has been well described with regards to glenoid bone loss by several authors.5,9 Though only comprising 2-10% of instability cases, the clinical outcomes of posterior shoulder instability have been reported. 1,2,4,6,8 While the association of glenoid retroversion in posterior instability has been reported, no description has been made of bone loss in patients undergoing posterior stabilization. 1,3 Accurate description of posterior bone loss will lead to more accurate cadaveric models, aid in developing new techniques for osseous augmentation like distal tibia allograft,7 and ideally improve our ability to obtain satisfying clinical outcomes.

Methods

Clinical data was selected for patients that had undergone posterior stabilization (open or arthroscopic) or posterior osseous augmentation (distal tibia or iliac crest). Three surgeons from two institutions contributed patients. Pre-operative computed tomography (CT) data was collected for all patients. The axial cuts were segmented and reformatted in three-dimensions for glenoid analysis using Osirix. From this three-dimensional model, the following was calculated: percent bone loss (Nobuhara), total arc of the defect (degrees), and a clock-face description (start point, stop point, and average or direction). Pearson correlation coefficients were performed using significance of p<0.05.

Results

Fifty shoulders from 50 patients were reviewed. Fourteen had evidence of posterior glenoid bone loss and were included for evaluation. Patients’ age averaged 30 years old with a range of 19 to 39, with 13 of 14 being male. Etiology of bone loss included acute traumatic dislocations and chronic dislocations. Defects on average involved 13.7±8.6% of the glenoid (Range: 2-35%). The average start time (assuming all right shoulders) on the clock face was 10 o’clock ± 40 minutes and stopped at 6:30 ± 25 minutes. The average direction of the defect pointed toward 8:15 ± 25 minutes. The percent bone loss correlated with the total arc of the defect (Pearson: 0.93, p<0.05, R2: 0.86) and the direction of the bone loss (Pearson: 0.64, p<0.05, R2: 0.40). Finally the direction of bone loss significantly moved more posterosuperior the larger the defect became (Pearson: 0.63, p<0.05, R2:0.40.

Discussion

Posterior bone loss associated with posterior glenohumeral instability is typically directed posteriorly at 8:15 on the clock. As defect get bigger, this direction moves more posterosuperior. This information will help guide clinicians in understanding the typical location of posterior bone loss aiding in diagnosis, cadaveric models, and treatment