'On-track' and 'off-track' shoulder lesions

Area of Science:

• Orthopedics
• Biomechanics
• Sports Medicine

Background:

• Shoulder stability relies on capsulo-ligamentous structures, intra-articular pressure, and concavity-compression effects, varying with arm position.
• Glenoid bone loss and Hill-Sachs lesions (HSL) are common in anterior shoulder instability, often occurring together as bipolar lesions.
• The glenoid track describes the contact zone between the glenoid and humeral head during arm movement.

Purpose of the Study:

• To explain the biomechanical factors influencing shoulder stability.
• To define and differentiate types of glenoid bone loss and Hill-Sachs lesions.
• To introduce and validate the clinical utility of the "on-track/off-track" concept for predicting HSL engagement and recurrence.

Main Methods:

• Review of biomechanical principles of shoulder stabilization.
• Classification of bone lesions in shoulder instability.
• Clinical validation of the glenoid track and "on-track/off-track" classification for predicting lesion engagement.

Main Results:

• The "on-track/off-track" concept accurately predicts the engagement risk of Hill-Sachs lesions with the glenoid.
• "Off-track" lesions pose a significant risk for recurrent dislocations.
• Treatment decisions for "off-track" lesions depend on glenoid defect size and recurrence risk, often involving remplissage or Latarjet procedures.

Conclusions:

• The glenoid track and "on-track/off-track" classification are crucial for understanding and managing shoulder instability.
• Accurate assessment of HSL and glenoid bone loss is essential for surgical planning.
• Remplissage or Latarjet procedures are indicated for "off-track" lesions to prevent recurrence.