Malfunction of the Infraspinatus Muscle as a Dynamic Stabilizer of the Shoulder in a Case of Posterior Subluxation

Yoshikawa G., Maeno M., Fukuda S., Murakami M., Hata M., Makikawa M.

doi:10.11296/katakansetsu1977.16.2_208

Existence of a dynamic stabilizing system of the glenohumeral joint is still controversial. According to Murakami the infraspinatus muscle works as a main stabilizer of the joint when a backward stress is loaded to the humeral head. We revealed a disorder of the infraspinatus muscle in a case of posterior subluxation of the shoulder by electrophysiological examination.<BR>Backward stress was loaded to the humeral head of a patient with posterior subluxation of the right shoulder, while the active potentials of the infraspinatus, supraspinatus and deltoid muscles were quantitatively measured.<BR>Electrical activdt y of the infraspinatus muscle was weaker on the affected side than on the healthy side, although no muscle atrophy was observed. The supraspinatus and deltoid behaved alike on both sides.<BR>If the infraspinatus muscle works as a dynamic stabilizer in response to the signals arising from the sensors in the posterior capsule when it is extended, our findings are thought to show that the feedback mechanism of the joint capsule is disturbed in the subluxation of the shoulder.

Malfunction of the Infraspinatus Muscle as a Dynamic Stabilizer of the Shoulder in a Case of Posterior Subluxation

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