Position Change of the Neurovascular Structures around the Carpal Tunnel with Dynamic Wrist Motion

OBJECTIVE: The purpose of this study was to determine the anatomic relationships between neurovascular structures and the transverse carpal ligament so as to avoid complications during endoscopic carpal tunnel surgery. METHODS: Twenty-eight patients (age range, 35-69 years) with carpal tunnel syndrome were entered into the study. We examined through wrist magnetic resonance imaging in three different positions (neutral, radial flexion, and ulnar flexion) and determined several anatomic landmark (distance from the hamate hook to the median nerve, ulnar nerve, and ulnar vessel) based on the lateral margin of the hook of the hamate. The median nerve and ulnar neurovascular structure were studied with the wrist in the neutral, ulnar, and radial flexion positions. RESULTS: The ulnar neurovascular structures usually passed just over or ulnar to the hook of the hamate. However, in 12 hands, a looped ulnar artery coursed 0.6-3.3 mm radial to the hook of the hamate and continued to the superficial palmar arch. The looped ulnar artery migrates on the ulnar side of Guyon's canal (-5.2-1.8 mm radial to the hook of the hamate) with the wrist in radial flexion. During ulnar flexion of the wrist, the ulnar artery shifts more radially beyond the hook of the hamate (-2.5-5.7 mm). CONCLUSION: It is appropriate to transect the ligament greater than 4 mm apart from the lateral margin of the hook of the hamate without placing the edge of the scalpel toward the ulnar side. We would also recommend not transecting the transverse carpal ligament in the ulnar flexed wrist position to protect the ulnar neurovascular structure.

The Safety of Entrance Reference Line in Endoscopic Carpal Tunnel Release: A Cadaveric Anatomical Evaluation

OBJECTIVE: The purpose of this study is to investigate the anatomic relationship between the neurovasular structures and transverse carpal ligment(TCL) to avoid complications during endoscopic carpal tunnel release. METHODS: Sixteen fresh cadaver hands from 3 men and 5 women(age range, 58~74 years) were used. Neurovascular structures around the TCL were meticulously dissected under a loupe magnification and several morphometric indices were calculated. RESULTS: We found an average length of TCL is 41mm and average distance between the TCL distal margin and superficial palmar arch along the flexor tendon of the ring finger is 9.2mm. In 3 hands, the looped ulnar artery, coursed 1 to 4mm radial to hook of hamate, continuing to the superficial palmar arch. During radial-to-ulnar flexion of the wrist, the looped ulnar artery beyond the hook of hamate shifts more radially (2 to 7mm) with proximal carpal bone. We also noted a Berretini branch located adjacent to the edge of the distal TCL. CONCLUSION: It is appropriate to transect the ligament at least 4mm radial from the radial margin of the hook of hamate or transect the proximal ligament in the radially deviated hand position to protect ulnar neurovascular structure. The proximal portal could be made just ulnar to the palmaris longus tendon to avoid the vascular injury in the proximal portion of the TCL.