Does Scapular and Thoracic Morphology Affect Latarjet Alpha Angle?

Area of Science:

• Orthopedic surgery
• Radiology
• Biomechanical analysis

Background:

• The Latarjet procedure is a common surgical treatment for recurrent anterior shoulder instability.
• Optimizing screw placement, reflected by the alpha angle, is crucial for successful outcomes.
• The influence of patient-specific thoracic morphology on surgical parameters like the alpha angle remains under-explored.

Purpose of the Study:

• To investigate the relationship between thoracic diameters and the alpha angle post-Latarjet procedure.
• To identify thoracic morphology metrics that correlate with or predict the alpha angle.
• To enhance understanding of factors influencing surgical outcomes in Latarjet procedures.

Main Methods:

• Retrospective analysis of 74 patients undergoing Latarjet procedures for recurrent anterior shoulder instability.
• Evaluation of postoperative chest CT scans to measure alpha angle, thoracic diameters (anteroposterior/transverse ratio - AP/T), scapular inclination, and glenoid version.
• Statistical correlation analysis and receiver operating characteristic (ROC) curve analysis to assess predictive value.

Main Results:

• A significant positive correlation was found between the AP/T ratio and the alpha angle (r = 0.407, p < 0.001).
• Scapular inclination, glenoid version, and thoracoscapular angle also showed significant correlations with the alpha angle.
• An AP/T ratio threshold of 1.2545 predicted poorer outcomes (AUC = 0.660, p = 0.018), with alpha angles >15 degrees associated with worse results.

Conclusions:

• Thoracic morphology, particularly the AP/T ratio, directly influences the alpha angle achieved during Latarjet procedures.
• Higher AP/T ratios are associated with larger alpha angles, posing potential challenges for optimal screw placement.
• Preoperative assessment of thoracic morphology may aid in anticipating and managing challenges in achieving target alpha angles.