GUYONS CANAL REVISITED - AN ANATOMIC STUDY OF THE CARPAL ULNAR NEUROVASCULAR SPACE

The boundaries of the space through which the ulnar neurovascular bund le crosses the wrist have been reinvestigated. Using gross dissections , transverse and sagittal sections, and histologic study, we determine d that the roof of Guyon's canal, the ''carpal ulnar neurovascular spa ce,'' does not directly connect to the hamate bone, as is currently ac cepted. The roof of this space extends radially to the hook of hamate and attaches to the flexor retinaculum. This anatomic arrangement allo ws the ulnar artery and sensory component of the ulnar nerve to course radially to the hook of hamate, where they lie on the flexor retinacu lum (transverse carpal ligament). The roof and radial border have thre e segments: (1) a proximal segment that begins near the pisiform and e xtends distally to the level of the hook of hamate but does not attach directly to it (2) a central segment that contains only adipose tissu e, and (3) a distal fascial layer that includes the palmaris brevis mu scle. The floor of the space consists of the muscles of the hypothenar eminence, their fibers of origin, and the flexor retinaculum (transve rse carpal ligament). Guyon accurately described the proximal portion of the carpal ulnar neurovascular space, but his description has been misinterpreted; the hook of hamate does not serve as the radial bounda ry of Guyon's canal. The anatomic relationships of the ''carpal ulnar neurovascular space'' need to be appreciated to avoid complications du ring carpal tunnel surgery.