Evaluation of a proprioception pathway in patients with stable and unstable shoulders with somatosensory cortical...

Histologic studies have documented the presence of mechanoreceptors in the glenohumeral ligaments, capsule, and labrum; however, direct evidence of an intact afferent electrical pathway originating in structures in the shoulder is lacking. Because somatosensory cortical evoked potentials are transmitted by way of the dorsal columns of the spinal cord and carry proprioceptive information, this technique can be easily applied to evaluate the potential proprioceptive function of various intraarticular structures for shoulder stability. Patients have somatosensory cortical evoked potentials monitored while undergoing shoulder arthroscopy. The inferior glenohumeral ligament, middle glenohumeral ligament, subscapularis tendon, biceps tendon, supraspinatus rotator cuff capsule, glenoid labrum, and humeral head were evaluated. The intraarticular structures were stimulated with a monopolar electrode probe inserted through the anterior portal, and the evoked potentials were recorded with scalp electrodes. Generated wave forms were recorded and evaluated by measuring the peak-to-peak amplitude and latency. Three groups of patients with shoulder complications were studied: (1) no intraarticular pathologic condition and stable, (2) anterior instability with a Bankart lesion, and (3) anterior instability with a loose capsule. The articular cartilage of the humeral head generated no wave form in any subject. All other intraarticular structures generated consistent wave forms. No statistically significant difference was seen among the three groups when both amplitude and latency for the intraarticular structures were compared.