Variations of the median nerve in the carpal canal.

Eight hundred twenty-one median nerves were retrospectively and prospectively reviewed for variations during operations to treat carpal tunnel syndrome. Ninety-two cadaver median nerves were also dissected to document the incidence of variations within the carpal canal. The combined incidence of anomalies at operation (Lanz groups 1 to 4) was 9.8% and in the cadaver series 18%. The discrepancy reported by Poisel, 54% in the Lanz group 1 series, versus ours of 1.42% cannot be explained.