Summary

The goal of this biomechanical study was to determine the maximum amount of the coracoid that can be resected during arthroscopic coracoplasty without leading to coracoid fracture or avulsion of the conjoint tendon during simulated activities of daily living.

Abstract

Background

Arthroscopic coracoplasty is a commonly performed procedure in orthopedic surgery for patients affected by subcoracoid impingement. To date, there is no consensus on how much of the coracoid can be resected with the shaver without compromising its stability. This biomechanical study aimed to determine the maximum amount of the coracoid that can be resected during arthroscopic coracoplasty without leading to coracoid fracture or avulsion of the conjoint tendon during simulated activities of daily living.

Methods

A biomechanical cadaver study was performed with 24 shoulders (15 male, 9 female). Specimen were randomized into three treatment groups with similar distribution based on age, gender, and bone mineral density: group (A): native coracoid; group (B): 3 mm coracoplasty; group (C): 5 mm coracoplasty. Coracoid anatomic measurements were documented before and after coracoplasty. The scapula was potted, and a traction force was applied through the conjoint tendon. The stiffness and load-to-failure (LTF) were determined for each specimen.

Results

The mean coracoid thickness in group (A) was 7.2 mm, 7.68 mm in group (B), and 7.81 mm in group (C). The mean LTF was 428 N (± 127 SD) in group (A), 284 N (± 77 SD) in group (B), and 159 N (± 87 SD) in group (C). Group (B) showed a significantly lower LTF in comparison with group (A) (p=0.016), as did group (C) (p<0.001). The stiffness of specimens between group A and group B showed no significant difference postoperatively (p=0.077), whereas the difference between group A and group C was significant (p=0.005). Postoperative coracoids with a thickness of 5 mm or greater were able to withstand activities of daily living.

Conclusion

Depending on the amount of bone resected, arthroscopic coracoplasty can weaken the coracoid in a potentially clinically relevant manner. A 3 mm coracoplasty did not weaken the coracoid significantly in most patients. The critical value of 5 mm of coracoid thickness should be preserved to ensure its stability. In correspondence with the findings of this study, careful preoperative planning should be used to measure the maximum reasonable amount of coracoplasty to be performed.