This enables a harmonic rotation of the forearm. The core of the distal radioulnar joint stability is best described with the concept of “tensegrity,” which entails stability through a synergy of ligament tensile and joint compressive forces. Although static joint stability is constituted by osseous and ligamentous integrity, the dynamic elements of joint stability concern proprioceptive control of the compressive and directional muscular forces acting on the joint. Joint stability relies on fine interactions of mechanical and dynamic components. The distal radioulnar joint, together with the proximal radioulnar joint, is responsible for the pronosupination movement of the radius and the ulna. The distal radioulnar joint is one of the most important and unique articulations in the wrist. Lesions of the volar and dorsal radioulnar ligaments have immense consequences not only for mechanical but also for dynamic stability of the distal radioulnar joint, and surgical reconstruction in instances of radioulnar ligament injury is important. The articular disc and ulnolunate ligament rarely are innervated, which implies mainly mechanical functions, whereas all other structures have pronounced proprioceptive qualities, prerequisite for dynamic joint stability. Nociception has a primary proprioceptive role in the neuromuscular stability of the distal radioulnar joint. The intrastructural analysis revealed no differences in mechanoreceptor distribution in all investigated specimens with the numbers available, showing a homogenous distribution of proprioceptive qualities in all seven parts of the triangular fibrocartilage complex.
Ruffini endings free#
Free nerve endings were obtained in each structure more often than all other types of sensory nerve endings (p < 0.001, respectively). More blood vessels were seen in the volar radioulnar ligament (median, 363.62 range, 117.8–871.8/cm 2) compared with the ulnolunate ligament (median, 107.7 range, 15.9–410.3/cm 2 difference of medians: 255.91 p = 0.002) and the dorsal radioulnar ligament (median, 116.2 range, 53.9–185.1/cm 2 difference of medians: 247.47 p = 0.001). The articular disc contained fewer free nerve endings (median, 1.8 range, 0–17.8/cm 2) and fewer blood vessels (median, 29.8 range, 0–112.2/cm 2 difference of medians: 255.9) than all other structures of the triangular fibrocartilage complex (p ≤ 0.001, respectively) except the ulnolunate ligament. Furthermore, free nerve endings were the predominant sensory nerve ending (median, 72.6/cm 2 range, 0–469.4/cm 2) and more prevalent than all other types of mechanoreceptors: Ruffini (median, 0 range, 0–5.6/cm 2 difference of medians, 72.6 p < 0.001), Pacini (median, 0 range, 0–3.8/cm 2 difference of medians, 72.6 p < 0.001), Golgi-like (median, 0 range, 0–2.1/cm 2 difference of medians, 72.6 p < 0.001), and unclassifiable corpuscles (median, 0 range, 0–2.5/cm 2 difference of medians, 72.6 p < 0.001). The articular disc had only free nerve endings. ResultsĪll types of sensory corpuscles were found in the various structures of the triangular fibrocartilage complex with the exception of the ulnolunate ligament, which contained only Golgi-like endings, free nerve endings, and unclassifiable corpuscles. Sensory nerve endings were counted in five levels per specimen as total cell amount/cm 2 after staining with low-affinity neurotrophin receptor p75, protein gene product 9.5, and S-100 protein and thereafter classified according to Freeman and Wyke. The subsheath of the extensor carpi ulnaris tendon sheath, the ulnocarpal meniscoid, the articular disc, the dorsal and volar radioulnar ligaments, and the ulnolunate and ulnotriquetral ligaments were dissected from 11 human cadaver wrists. We aimed to (1) analyze the general distribution of sensory nerve endings and blood vessels (2) examine interstructural distribution of sensory nerve endings and blood vessels (3) compare the number and types of mechanoreceptors in each part and (4) analyze intrastructural distribution of nerve endings at different tissue depth. Therefore, an investigation of the pattern and types of sensory nerve endings gives more insight in dynamic distal radioulnar joint stability. While static joint stability is constituted by osseous and ligamentous integrity, the dynamic aspects of joint stability chiefly concern proprioceptive control of the compressive and directional muscular forces acting on the joint.
The triangular fibrocartilage complex is the main stabilizer of the distal radioulnar joint.
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