Loss of Pinch Movements with Carpal Tunnel Syndrome
Loss of strength, coordination, and movement of the fingers from carpal tunnel syndrome (CTS) make it difficult to pick up and hold objects. In this study, scientists measure the effect of CTS on precision pinch movements between the thumb and index finger.

Two groups of people were included in the study. The control group was normal adults with no evidence of CTS. They were matched by age and gender with the second group (subjects with CTS). Everyone in both groups was right handed.

Patients with CTS reported numbness, pain, and night awakening. Clinical and electrodiagnostic tests were all positive for CTS. Severity of symptoms was determined using several special tests. These included the Levine-Katz questionnaire, Semmes-Weinstein monofilament tests, and two-point discrimination. According to the combined results of these tests, the CTS group had mild-to-moderately severe CTS.

A special video-based motion analysis system was used to measure precise pinch movements. The equipment used surface markers to help trace the movement without interfering with normal movement. The arm was put in a special holder to stabilize the elbow, forearm, and wrist.

Each person completed two sets of 15-pinch cycles. One cycle was from a position of fingers opened to contact of the tips and return to an open hand position. Each cycle took approximately three seconds to complete. Using a grid of coordinates, the researchers measured the variability of pinch closures. They looked at joint angles, placement of pinch positions, and joint motion of the thumb.

They found there was a difference between the two groups. Patients with CTS had much more variability in joint angles and tip position of the thumb and index finger at the point of pinch closure.

These differences show how finger coordination is affected by CTS. Precise pinch movements are more difficult when nerve impairment from CTS causes numbness of the fingertips and loss of muscle strength in the thumb and fingers.

Certain movements of the thumb were more impaired than others. For example, thumb abduction (moving the thumb toward the other hand) was affected more than flexion or extension. This is most likely because the median nerve affected by CTS is the main nerve to supply the thumb abductor muscles.

Nerve damage means less input to the hand from the skin, joints, and tendons. The result is a loss of accuracy when trying to put the thumb and finger together for pinching. During everyday activities this means grasping, picking up, and holding of objects can be difficult. Precise finger manual tasks are important to keep from dropping things.

Other studies have shown a change in the angle of the tips of the index finger and thumb during pinch for patients with CTS. Change in joint posture was not evident between the two groups in this study. The authors suggest this may be because patients with CTS did not have severe, chronic CTS.

The authors conclude that using measures of variability in repetitive movements like pinch is a good way to measure or quantify hand dysfunction. This information can be used to establish a baseline of function.

The baseline can be used to identify if and when the condition is getting better or worse. And measurable results of treatment can be determined. Improvement in precision pinch movements might be a good way to tell which intervention(s) work best.
Sebastian Gehrmann, MD, et al. Variability of Precision Pinch Movements Caused By Carpal Tunnel Syndrome. In The Journal of Hand Surgery. September 2008. Vol. 33A. No. 7. Pp. 1069-1075.