Treatment of shoulder instability with bipolar lesions: the on-track/off-track concept

Background: The glenohumeral joint is the most frequently dislocated joint in the body, often resulting in bipolar bone loss characterized by concomitant anteroinferior glenoid defects and posterolateral humeral head compression fractures, known as Hill-Sachs lesions. While arthroscopic Bankart repair (ABR) is the standard treatment for soft tissue injuries with minimal bone loss, high recurrence rates are observed in patients with significant bipolar lesions, particularly athletes in contact sports.

Objective: This article aims to delineate the glenoid track concept and its application in surgical decision-making for bipolar shoulder instability, while detailing the technical execution of remplissage and the indications for alternative stabilization procedures.

Key Points: The glenoid track represents the contact zone between the glenoid and humeral head during end-range motion; lesions extending medially beyond this track are classified as "off-track" and carry a higher risk of engagement and recurrence. Quantification of bone loss via 3D computed tomography or arthroscopic measurement allows for categorization into four treatment groups. Management strategies include ABR alone for on-track lesions with less than 25% glenoid loss, and ABR augmented with remplissage (infraspinatus tenodesis) for off-track lesions. For glenoid defects exceeding 25%, the Latarjet procedure or iliac crest autografting is indicated to restore the articular arc and provide a dynamic sling effect.

Conclusion: Successful management of recurrent anterior shoulder instability requires precise quantification of bipolar bone loss. Utilizing the glenoid track concept to guide the selection between soft tissue augmentation and bone grafting procedures optimizes clinical outcomes and reduces the risk of postoperative recurrence.