Coracoid bone block transfer procedure: Correlation between subscapularis volume below the bone graft and shoulder...

Area of Science:

• Orthopedic Surgery
• Sports Medicine
• Anatomy

Background:

• Coracoid bone graft transfer is the standard for recurrent anterior shoulder instability with bony defects.
• The conjoint tendon and subscapularis (SS) muscle sling effect are key to the procedure's stability.
• The relationship between SS volume and postoperative stability needs further investigation.

Purpose of the Study:

• To investigate the correlation between the volume of the subscapularis (SS) muscle below the bone graft and shoulder stability after coracoid bone graft transfer.
• To determine if a larger inferior SS volume impacts clinical outcomes and graft positioning.

Main Methods:

• Prospective study of 40 patients undergoing open coracoid bone graft transfer for recurrent anterior shoulder instability.
• Clinical and CT scan evaluation at 2-year follow-up.
• Correlation analysis of the SS volume index (ratio of SS volume below to above the graft) with Rowe and Walch-Duplay instability scores.

Main Results:

• A significant positive correlation was found between the SS volume index and the postoperative Rowe score (r=0.37, P=0.03).
• A similar trend was observed for the Walch-Duplay score, though not statistically significant.
• Increased inferior SS volume did not lead to limited external rotation, increased fatty infiltration, or graft malposition.

Conclusions:

• Greater subscapularis (SS) muscle volume below the bone block is associated with improved postoperative shoulder stability.
• The study recommends splitting the SS muscle in the middle or higher, rather than at the superior two-thirds/inferior one-third junction, to maximize this benefit.