EVALUATION OF A PROPRIOCEPTION PATHWAY IN PATIENTS WITH STABLE AND UNSTABLE SHOULDERS WITH SOMATOSENSORY CORTICAL EVOKED-POTENTIALS

Histologic studies have documented the presence of mechanoreceptors in the glenohumeral ligaments, capsule, and labrum; however, direct evid ence of an intact afferent electrical pathway originating in structure s in the shoulder is lacking. Because somatosensory cortical evoked po tentials are transmitted by way of the dorsal columns of the spinal co rd and carry proprioceptive information, this technique can be easily applied to evaluate the potential proprioceptive Function of various i ntraarticular structures For shoulder stability. Patients have somatos ensory cortical evoked potentials monitored while undergoing shoulder arthroscopy. The inferior glenohumeral ligament, middle glenohumeral l igament, subscapularis tendon, biceps tendon, supraspinatus rotator cu ff capsule, glenoid labrum, and humeral head were evaluated. The intra articular structures were stimulated with a monopolar electrode probe inserted through the anterior portal, and the evoked potentials were r ecorded with scalp electrodes. Generated wave forms were recorded and evaluated by measuring the peak-to-peak amplitude and latency. Three g roups of patients with shoulder complications were studied: (1) no int raarticular pathologic condition and stable, (2) anterior instability with a Bankart lesion, and (3) anterior instability with a loose capsu le. The articular cartilage of the humeral head generated no wave form in any subject. All other intraarticular structures generated consist ent wave forms. No statistically significant difference was seen among the three groups when both amplitude and latency for the intraarticul ar structures were compared.