Innervation of the triangular fibrocartilage complex of the human wrist: Quantitative immunohistochemical study

Abstract

The distribution of neural elements in the triangular fibrocartilage complex (TFCC) of the human wrists was studied via immunohistochemical staining of protein gene product (PGP) 9.5 and calcitonin gene-related peptide (CGRP). Articular branches projecting to the TFCC arose from the dorsal branch of the ulnar nerve in all wrists examined. The TFCC is subdivided into the following six regions: the articular disc proper (ADP), meniscus homolog (MH), radio-ulnar ligament (RUL), loose part of ulnar collateral ligament (lUCL), dense part of ulnar collateral ligament (dUCL), and internal portion (IP). The IP consists of a mixture of dense and loose connective tissues enclosed by the ADP, MH, RUL, and UCL, and resides deep in the prestyloid recess, which is a pit in the MH. The densities of PGP 9.5-positive neural elements, including free nerve endings, single nerve fibers, nerve fascicles, and perivascular neural nets, were significantly higher in the IP than in other regions. Some of the neural elements except for the perivascular neural nets were positive for CGRP. The high density of neural elements in the IP suggests that sensory nerves projecting to the TFCC enter into the IP and from there distribute to adjacent regions such as the MH and RUL. Free nerve endings are responsible for pain transmission. The high density of free nerve endings in the IP suggests that the IP is a source of ulnar side wrist pain.

Immunohistochemical Mapping of Sensory Nerve Endings in the Human Triangular Fibrocartilage Complex

“…Free nerve endings were the predominant mechanoreceptor type in all of the examined structures of the triangular fibrocartilage complex, which is in accordance with a previous study [24] and studies of the human ankle [21], fat tissue in the human sinus tarsi [23], and the human knee capsule [12]. The predominance of free nerve endings indicates an important role in perceiving noxious, chemical, mechanical, and inflammatory stimuli.…”

“…Furthermore, in the current study, all seven parts of the triangular fibrocartilage complex were dissected separately and analyzed in five levels, respectively. An additional study of innervation of the triangular fibrocartilage complex only detected free nerve endings, but no Ruffini, Pacini, or Golgi-like corpuscles, using PGP 9.5 and calcitonin gene-related peptide [24]. However, the analyzed sections had a thickness of 100 lm, and the amount of each neural element was counted in randomly selected areas of each structure at only one level.…”

“…The general innervation of the triangular fibrocartilage complex has been described and consists of innervation by dorsal sensory branches of the ulnar nerve in 100%, by the medial antebrachial cutaneous nerve in 91%, by volar branches directly from the ulnar nerve in 73%, by the anterior interosseous nerve in 27%, by the posterior interosseous nerve in 18%, and by volar cutaneous branches of the median nerve in 9% [7,16,24].…”

Nerve Fiber Staining Investigations in Traumatic and Degenerative Disc Lesions of the Wrist

“…[2][3][4] Previous anatomical and immunohistochemical investigations regarding the innervation of the TFCC were conducted using biopsies from cadaver discs and revealed no evidence of nerve fibers in the healthy disc. [5][6][7] In non-disc parts of the TFCC, however, nerve fibers could be detected. [5][6][7] It is thus plausible that in the context of degenerative restructuring or regenerative processes after trauma, nerve fibers could grow into the disc and cause pain; analogous to the findings that in the intervertebral disc of the spine, nerve fibers grow from the periphery into the degenerative or injured disc and cause pain.…”

“…[5][6][7] In non-disc parts of the TFCC, however, nerve fibers could be detected. [5][6][7] It is thus plausible that in the context of degenerative restructuring or regenerative processes after trauma, nerve fibers could grow into the disc and cause pain; analogous to the findings that in the intervertebral disc of the spine, nerve fibers grow from the periphery into the degenerative or injured disc and cause pain. 8 -10 To test for the presence of nerve fibers, we used the antibody protein gene product 9.5 (PGP 9.5), first detected as a brain-specific protein over 28 years ago.…”