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An in vitro study of glenohumeral performance after suprascapular nerve entrapment


Medicine & Science in Sports & Exercise: April 2002 - Volume 34 - Issue 4 - p 581-586
CLINICAL SCIENCES: Clinical Investigations

LUO, Z-P., H-C. HSU, and K-N. AN. An in vitro study of glenohumeral performance after suprascapular nerve entrapment. Med. Sci. Sports Exerc., Vol. 34, No. 4, pp. 581–586, 2002.

Purpose 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° flexion and maximal internal rotation; and anterior, one with 90° abduction and 90° 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° abduction and 90° external rotation.

Conclusion 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.

Department of Orthopedic Surgery, Baylor College of Medicine, Houston, TX; Department of Orthopedic Surgery, China Medical College Hospital, Taichung, TAIWAN; Biomechanics Laboratory, Department of Orthopedics, Mayo Clinic, Rochester, MN

Submitted for publication October 2000.

Accepted for publication August 2001.

© 2002 American College of Sports Medicine