Motor control impairment of the contralateral wrist in patients with unilateral chronic wrist pain

Objective: Assessment of the quality of fine motor control in patients with unilateral chronic wrist pain seldom focuses on the possibility that control of movements is effector independent at the cerebral level. This mechanism may be involved in an impairment of motor function in the unaffected wrist. We studied the possible motor impairment in the unaffected wrist in patients with chronic wrist pain. Design: Eighteen patients with chronic wrist pain in their dominant hand and 20 healthy controls performed, using their nondominant hand, back-and-forth, left-to-right stroke patterns with a pen on a digital writing tablet connected to a computer. Fluency of movement, defined as the number of zero-crossings of the acceleration curve (pZC), average stroke size, and average velocity were calculated. Results: The controls moved significantly more fluently than the patients (pZC, 0.26 ± 0.07 for controls and 0.46 ± 0.20 for patients; P < 0.001), suggesting that long-term afferent disturbances may compromise cerebral motor control mechanisms. Conclusions: This result is in accordance with the view that chronic pain complaints may be maintained by persistently abnormal cerebral motor control. This finding opens a new perspective on the understanding and treatment of chronic wrist pain.