Takao Tokioka

An investigation of the digital nerves of the thumb.

With the use of a stereoscopic microscope, observations were made on the course of the proper digital nerve of the thumb on ten upper limbs in adult cadavers. By observation from the dorsal side after removal of the bone, it was possible to clearly see the ramification of the digital nerve from the subcutaneous tissue to the dermis. Ramification from the palm to the level of the interphalangeal joint was segmental. The digital nerve of the thumb trifurcates from the proximal site of the distal palmar thumb crease into the main, medial, and lateral branches. The main branch is thick and extends from the center of the pulp toward the fingertip. Ramification at the pulp of the thumb is of a radiating rather than segmental type, and its control can be considered as spotty or intermittent. Distribution of pacinian corpuscles is dense in the subcutaneous tissue of the distal palmar thumb crease. These observations are of clinical importance not only for avoidance of injury to the digital nerve in surgical procedures such as the incision and drainage for felon and the trigger thumb release but also for precise repair of the digital nerve in the reconstructive surgery of the thumb.