An in vitro study of glenohumeral performance after suprascapular nerve entrapment.
OBJECTIVE
The functional performance of athletes with suprascapular nerve entrapment remains unaddressed biomechanically. The purpose of this study was to investigate the glenohumeral joint kinematics, stability, and characteristics of joint contact.


METHODS
The investigation used an in vitro model simulating muscle palsy due to the suprascapular nerve entrapment. The experiment was performed in three clinically relevant positions: inferior, one by sulcus test; posterior, one with 90 degrees flexion and maximal internal rotation; and anterior, one with 90 degrees abduction and 90 degrees external rotation (which is critically involved in several sports activities).


RESULTS
Simulated palsy due to suprascapular nerve entrapment had effects on glenohumeral joint stability and contact characteristics. Changes in the humeral head displacement and the glenohumeral joint contact characteristics were the most significant in the anterior direction when the arm in 90 degrees abduction and 90 degrees external rotation.


CONCLUSIONS
Glenohumeral function is affected by muscle weakness at the position that is critical in sports activities. Because the infraspinatus supplies 90% of the external rotation power of the shoulder and the supraspinatus stabilizes the humeral head in the glenoid during elevation, residual weakness due to suprascapular nerve entrapment may preclude a safe return to athletics.
Luo
Zong-Ping
ZP
Department of Orthopedic Surgery, Baylor College of Medicine, 6560 Fannin Drive, Houston, TX 77030, USA. luo@bcm.tmc.edu
Hsu
Horng-Chaung
HC
An
Kai-Nan
KN
D000368:Aged; D001265:Athletic Injuries / Q000150:complications; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D006811:Humerus / Q000503:physiopathology*; D066298:In Vitro Techniques; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology; D009408:Nerve Compression Syndromes / Q000209:etiology / Q000503:physiopathology*; D016059:Range of Motion, Articular; D012785:Shoulder Joint / Q000294:innervation* / Q000503:physiopathology*