Neck dissection shoulder syndrome: quantification and three-dimensional evaluation with an optoelectronic tracking system.

Objective 3-dimensional biomechanical changes of the shoulder at rest or during arm elevation were measured by means of a new specific method using an optoelectronic detection system that was developed for computer-aided surgery. Additionally, the shoulder syndrome following neck dissection was evaluated by the recognized orthopedic shoulder Constant score. The statistical evaluation encompassed 12 patients with unilateral radical neck dissection (RND), 12 patients with unilateral modified radical neck dissection (MRND) with preservation of the accessory nerve, and 10 healthy subjects. The healthy shoulders showed normal kinematic behavior, the so-called "scapulohumeral rhythm" (SHR). After MRND, the static scapular position and SHR showed no significant 3-dimensional variations. In contrast, RND produced a highly significant scapular displacement at rest (p < .01) and a near-total abolition of SHR. The Constant scores were significantly lower after RND than after MRND (p < .01). Three-dimensional evaluation of the shoulder syndrome supports the Constant score, quantifying what can be measured objectively.