Abstract
Background:
Bipolar bone loss – glenoid and humeral bone loss – is a risk factor for recurrent instability.1,2 Adolescent athletes with anterior shoulder instability present with bone loss more often than adult patients yet limited literature exists in this population. The purpose of this study is to evaluate the factors that affect bipolar bone loss presentation in the adolescent athlete.
Hypothesis:
Bipolar bone loss risk factors will include demographics, sport specialization, and history.
Methods:
A retrospective review of an IRB approved study of patients 10-19 years old diagnosed with shoulder instability from January 2022 to March 2024 was performed. Demographics, mechanism of injury, and number of dislocations were collected. Glenoid bone loss, humeral bone loss (Hill-Sachs interval – HSI), On-track vs Off-track, and distance to dislocation (DTD) were determined by MRI measurements. Bipolar bone loss was analyzed against patient demographics and clinical risk factors. Categorical variables were analyzed with chi-squared test and continuous variables were analyzed with Mann-Whitney U and Kruskal-Wallis tests.
Results:
181 patients with a mean age of 15.8±1.6 years (79.0% male) were included. 74.6% of patients presented with bone loss (glenoid/humeral/bipolar), while 34.3% had bipolar bone loss. 35.9% reported glenoid bone loss and 72.9% reported humeral bone loss with a mean HSI of 9.67±6.80 mm. 9.6% of shoulders with bone loss were considered Off-track. Of the On-track shoulders, 61.5% had a DTD<10mm. 27.7% of patients reported 2 or more prior dislocations, 16.5% of which reported 5+. 82.6% of patients reported that their instability event occurred during sports, with 78.2% injured during high impact sport. Bipolar bone loss was related to older age (16.29 vs 15.61; p=0.012), male sex (96.8% vs 69.7%; p<0.001), high impact sport at time of injury (92.9% vs 69.2; p<0.001), and 5+ prior dislocations (28.8% vs 9.9%; p=0.003).
Conclusion:
Adolescent athletes who present with a history of anterior shoulder instability have a high incidence of bipolar bone loss. Risk factors of bipolar bone loss are older age, male sex, significant recurrent instability and high impact sport participation. Of patients with bone loss, 9.6% have an Off-track lesion and 61.5% of patients with an On-track lesion have DTD<10mm, both of which may increase risk of failure following a Bankart repair without the addition of a remplissage or an open bone block procedure. Further research is necessary to understand the impact of bipolar bone loss and predict potential risk factors for its occurrence.