Natural evolution of idiopathic carpal tunnel syndrome with respect to wrist and hand anthropometry: A prospective cohort study.

Objective: A greater wrist depth/width ratio and wrist depth/palm length ratio are known risk factors for carpal tunnel syndrome. We hypothesized that these parameters might also predict progression in patients who were not surgically treated.

Methods: Seventy-eight patients with moderately severe idiopathic carpal tunnel syndrome of at least 10 months duration at recruitment, who declined surgical treatment and steroid injection, underwent repeated neurophysiological assessments after 3 years. A > 10% increase in median SNAP latency was taken as evidence of significant deterioration.

Results: Patients with a wrist ratio ≥ 0.72 showed a statistically significant deterioration in SNAP latency from 5.46 (SD 2.09) to 7.16 (SD 1.56) ms and in SNAP amplitude from 30.19 (SD 13.8) to 16.62 (SD 14.42) µv. For those with a wrist-to-palm ratio ≥ 0.42, SNAP latency deteriorated from 5.27 (SD 1.21) to 7.1 (SD 1.52) ms, and amplitude from 32.78 (SD 13.76) to 19.45 (SD 16.62) µv. Patients with lower ratios did not show significant changes in any neurophysiological parameter. The relative risk of significant deterioration in SNAP latency in patients with a wrist ratio ≥ 0.72 was 2.04 (95% CI 1.27-3.27).

Conclusion: In untreated idiopathic carpal tunnel syndrome, patients with larger wrist and wrist-to-palm ratios are more likely to show neurophysiological progression.