An Anatomical Study of At-Risk Nerves During Carpal Tunnel Release: Considerations for the Prevention of Iatrogenic Nerve Injury.

Despite carpal tunnel release (CTR) being a common procedure in hand surgery, variation in the location of the nerves supplying the palm leads to a high risk of iatrogenic damage. Recommendations have been made for a surgical incision placement that would avoid such damage, yet injury persists in clinical practice. These studies infrequently consider the safety of multiple at-risk nerves when making their recommendation, often optimizing the safety of one and subsequently jeopardizing another's. Sixty-one dissections were performed on formalin preserved cadavers to define a safe zone in the palm and recommend an incision placement for CTR. Detailed measurements examining the anatomy of the palmar cutaneous branch of the median nerve (PCBMN), the palmar cutaneous branch of the ulnar nerve (PCBUN), and the thenar motor branch (TMB) were taken relative the scaphoid tubercle, pisiform, or the A line. The PCBMN was located 3.3 ± 4.1 mm ulnar to the scaphoid tubercle and 8.7 ± 3.9 mm radial to the A line. The PCBUN was located the 6.5 ± 2.4 mm radial and 6.6 ± 3.7 mm ulnar from the pisiform and A line respectively. The TMB was found 8.0 ± 3.3 mm from the A line and was classified as 56% extraligamentous, 31% subligamentous, and 13% transligamentous. We conclude that an area approximately 6 mm ulnar and 7 mm radial from the A line is the safe zone for CTR and recommend an incision placement in line with the radial aspect of the fourth digit. This knowledge may aid surgeons performing CTR and help reduce iatrogenic damage.