Basic scienceThe anterior deltoid's importance in reverse shoulder arthroplasty: a cadaveric biomechanical study
Section snippets
Specimen preparation
Eight fresh-frozen cadaveric right shoulders, 6 male and 2 female, with ages ranging between 46 and 68 years were obtained. The specimens were stored at -20°C and thawed for 24 hours before testing. Specimens were excluded from use if they were found to have prior surgery or deltoid muscle compromise.
The skin, subcutaneous, and adipose tissues were removed around exposing the underlying muscles. The planes dividing the anterior (clavicular head), middle (acromial head), and posterior (posterior
Direction of rotation (DOR)
The 3D mechanical action measured by DOR for each segment of the deltoid before and after the surgery is listed in Table I. The most inferior portion of the anterior deltoid (anterior deltoid #1) changed from an adductor to an abductor after implantation of the reverse shoulder prosthesis at 0° of glenohumeral abduction. There were no other significant changes in the DOR. Our model also reaffirms that the deltoid is an important flexor of the glenohumeral joint.
Moment arms
Although the DOR remained
Discussion
The reverse shoulder prosthesis has revolutionized the way we treat cuff tear arthropathy, failed shoulder arthroplasty, and fractures in cuff deficient shoulders. This prosthesis functions by recruiting deltoid muscle fibers to initiate glenohumeral abduction and rotation. Unfortunately, many patients who have these problems have had prior surgery that may compromise the integrity of the anterior deltoid muscle. Thus it is important to not only understand how reverse shoulder arthroplasty
Conclusion
Three-dimensional moment arms (internal-external rotation, flexion-extension, and adduction-abduction) of 6 portions of deltoid before and after reverse total arthroplasty were evaluated. After arthroplasty, abduction and flexion moment arms were both increased. By sequentially unloading the anterior deltoid and recording the changes in moment arms, it was confirmed that the anterior deltoid is vital to flexion and abduction following reverse total shoulder arthroplasty. This study lends
Disclaimer
There was no source of external funding for this project. The implanted prostheses used were donated from DJO Surgical, Austin, TX, USA. The authors, their immediate families, and any research foundations with which they are affiliated did not receive any financial payments or other benefits from any commercial entity related to the subject of this article.
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Anterior deltoid muscle reflection using a deltopectoral approach is safe and does not influence outcome of reverse shoulder arthroplasty
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