Prevalence of anatomic variations encountered in elective carpal tunnel release

PURPOSE: To determine the prevalence of aberrant or unexpected anatomic structures within one surgeon's elective experience of carpal tunnel releases and their association with pathologic compression. METHODS: A total of 31 anomalies of median nerve, muscle, and tendon, median artery persistence, and ulnar nerve were documented in 30 hands during the course of 526 elective carpal tunnel releases in one surgeon's practice. The data collected were reviewed retrospectively. All carpal tunnel releases were performed open, exposing the median nerve from the palmar arch to the proximal wrist crease. Anomalies were categorized into those involving the median nerve and its motor and sensory branches, the ulnar nerve, a persistent median artery, and anomalies of muscle/tendon units traversing the carpal tunnel area. RESULTS: Seven hands were noted to have aberrant muscle/tendon variations within the carpal tunnel region (1.3%). Anomalies of the median nerve or its palmar cutaneous or motor branches were observed in 5 hands (1.0%). An anomaly of the ulnar nerve with an aberrant branch crossing the carpal tunnel incision occurred in one hand. A persistent median artery (>or=1 mm) was noted in 18 hands (3.4%). One hand had 2 anomalies present. One anomaly was high bifurcation of the median nerve and the second anomaly was an anomalous muscle to the long finger superficialis. CONCLUSIONS: The specific anatomic variations described may be anticipated and more readily recognized by hand surgeons during such open surgery, thus increasing the efficacy and safety of this common procedure.