Proximity of the Ulnar Neurovascular Structures in Endoscopic Carpal Tunnel Release Surgery: A Cadaveric Study

Abstract

To evaluate the proximity of the ulnar neurovascular structures to the endoscopic blade during endoscopic carpal tunnel release (CTR). Ten fresh-frozen cadaver hands were used to perform endoscopic CTR using devices from two manufacturers. The skin was excised from the palm, and the endoscopic carpal tunnel blade was deployed at the distal edge of the transverse carpal ligament (TCL). The blade's proximity to the ulnar neurovascular bundle, deep ulnar motor branch, superficial palmar arch, and median nerve was recorded. Following release of the TCL, the device was turned ulnar to the maximal extent to determine if direct injury to the ulnar neurovascular bundle was possible. The average longitudinal distance from the end of the TCL to the superficial palmar arch was 13.3 mm (range, 8.4-20.9) and to the ulnar motor branch was 10.8 mm (range, 4.0-15.0). The average transverse distance from the end of the TCL to the ulnar neurovascular bundle was 5.9 mm (range, 3.1-7.8) and to the median nerve was 3.3 mm (range, 0-6.5). In two of our specimens, the median nerve subluxated volarly over the cutting device. When placing the blade at the distal edge of the TCL, injury to the deep motor branch of the ulnar nerve, ulnar neurovascular bundle, or superficial palmar arch was not possible in any specimens using the tested devices, even when turning the blade directly toward these structures. There is a low likelihood of direct injury to the ulnar neurovascular bundle during endoscopic CTR. These results suggest that injury to the ulnar neurovascular bundle is unlikely during endoscopic CTR if the distal aspect of the transverse carpal ligament can be clearly identified prior to release. Control of the median nerve is also important to prevent subluxation over the cutting device.