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Tendon‐defect and muscle‐unloaded models for relating a rotator cuff tear to glenohumeral stability
Author(s) -
Hsu HorngChaung,
Boardman N. Douglas,
Luo ZongPing,
An KaiNan
Publication year - 2000
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.1100180615
Subject(s) - rotator cuff , tendon , supraspinatus muscle , medicine , biomechanics , rotator cuff injury , anatomy , orthodontics , physical medicine and rehabilitation
Rotator cuff tear and glenohumeral instability are closely related. Any tear may disturb muscle force generation due to pain inhibition. In addition, a full‐thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon‐defect model, dynamic and static elements of the joint were sacrificed. In a muscle‐unloaded model, only the dynamic element was removed. The location and size of the defect were also investigated. The effect on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand, with a larger tear the defect had a greater effect than muscle‐unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention, therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer.