The Influence of Subscapularis Muscle Split Location on Subscapularis Function After the Latarjet Procedure

Area of Science:

• Orthopedic surgery
• Biomechanics
• Shoulder anatomy

Background:

• Subscapularis splitting in the Latarjet procedure affects muscle mechanics.
• The precise impact of split level on postoperative function is not well understood.

Purpose of the Study:

• To evaluate how midlevel, lower-third, and upper-third subscapularis splits influence muscle action lines and moment arms.
• To assess these effects in various shoulder positions, including abduction and external rotation (ABER).

Main Methods:

• A controlled laboratory study using cadaveric specimens.
• Simulated Latarjet procedure with different subscapularis split levels.
• Radiographic quantification of muscle lines of action and moment arms.

Main Results:

• Midlevel and lower-third splits deformed subscapularis fibers, increasing inferior inclination of muscle lines of action.
• This effect was more pronounced in ABER and apprehension positions.
• Midlevel splits showed greater adduction moment arms in the mid-superior subscapularis, indicating enhanced depressor capacity.

Conclusions:

• Latarjet surgery alters subscapularis leverage and force direction based on split location.
• A midlevel subscapularis split provides superior mechanical advantage for depressor function and stability, particularly in unstable shoulder positions.