Innervation of the Proximal Interphalangeal Joint: An Anatomical Study.

PURPOSE: To describe the innervation of the proximal interphalangeal (PIP) joint of the fingers as well as the anatomical relations of the articular branches. METHODS: In this anatomical study, 52 fresh-frozen index, long, ring, and little fingers of 6 male and 4 female cadavers were dissected after injection of a colored latex composite. The anatomical dissections were performed under ×3.5 and ×6.0 magnifications. The numbers of articular nerve branches that penetrated the PIP joint on both sides of the fingers were quantified and patterns of innervation were established. We also measured the origin of the branches regarding the PIP articular line, the angle of emergence, and the diameter of the nerves. RESULTS: The PIP joint was innervated by one articular branch of the proper palmar digital nerve at each side of the finger (pattern 1). Less frequently, an additional distal branch from the same proper palmar digital nerve was found (pattern 2). Dorsal articular branches were identified innervating only the little finger. CONCLUSIONS: The findings suggest that PIP joints of the fingers have a consistent articular nerve anatomy predominantly provided at the palmar aspect of the joint. These findings provide an anatomical basis for procedures to denervate the PIP joint. CLINICAL RELEVANCE: An accurate understanding of peripheral nerve anatomy of the PIP joint is essential to improve outcomes in denervation techniques.

Extended Posterior Interosseous Artery Flap: Anatomical and Clinical Study.

PURPOSE: A reverse-flow pedicled flap from the posterior interosseous artery (PIA) has been used to cover defects on the dorsal and volar aspects of the hand. However, the original description of this flap does not reach further than the metacarpophalangeal joints of the 4 ulnar digits. In the present study, we describe a distal variant (type 2) of the PIA flap, which changes the pivot point of the classic variant (type 1) and which can provide full coverage of single or multiple digits in the entire dorsum and palmar surface of the fingers. METHODS: An anatomical study was performed on 26 cadaveric specimens to assess the presence of the anastomosis between the PIA and the dorsal intercarpal arch (DIA). In addition, the gain in pedicle length using the DIA anastomosis as a pivot point was compared with the classic pivot point at the anterior interosseous artery. A clinical study in 19 patients with soft tissue defects distal to the proximal interphalangeal joint of the fingers was also performed to assess the viability and clinical outcomes of the new variant of the PIA flap. RESULTS: The PIA was identified reaching the dorsal carpal arch in all anatomical specimens. The mean pedicle length of the fifth extensor compartment artery was 4.8 cm (range, 4.1-5.3 cm). The mean arterial diameter was 0.8 mm (range, 0.6-1.2 mm). In the clinical study, 17 flap reconstructions were done for posttraumatic lesions and 2 postburn contractures. All extended PIA flap procedures were performed successfully without loss of the flap or significant partial necrosis. We had only 1 superficial infection. There was no need for revision of the flap in any case. CONCLUSIONS: By extending the pivot point of the PIA flap through the DIA, instead of the anastomosis with the anterior interosseous artery, the flap distance can be increased by about 8.5 cm, allowing complete coverage of the fingers. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.