[Innervation of metacarpophalangeal joint and distal interphalangeal joint: an anatomical and histological study].

Using 131 fingers for the metacarpophalangeal (MP) joint and 124 fingers for the distal interphalangeal (DIP) joint obtained from 30 hands of human cadavers, the innervation of the MP and DIP joints was investigated anatomically in detail. Two articular branches developing from a dorsal branch of the ulnar nerve and a superficial branch of the radial nerve, and entering the dorsal side of the MP joint from the ulnar side and radial side, respectively, were found in every finger. In addition, articular branches from the deep branch of the ulnar nerve were found in every middle, ring and little finger. However, articular branches from the proper palmar digital nerve were found to exist in 62.7% of the fingers. Articular branches developing from the proper palmar digital nerve and going towards the DIP joint were found in every case, and 97.3% of 244 branches developed directly from the proper palmar digital nerve, while some of the remaining branches were from a dorsal branch of the proper palmar digital nerve and others developed neural loop penetration. Articular branches ran parallel to the distal transverse artery and entered the joint, and some of them went towards the volar plate, dorsal joint capsule, and tendon sheath. Many nerve endings existed in the surface layer of the articular capsule and arthrosynovial membranes in the form of Pacinian corpuscles and corpuscles of Ruffini. The existence of a neural loop in the finger should be taken notice of during somatoscopy in patients with neurovascular symptoms in the fingertip or surgical operation on a vascular pedicular island flap. Further, it was suggested that injury of the articular branch of the DIP joint could induce Heberden nodes due to its anatomical characteristics.