General innervation pattern and sensory corpuscles in the scapholunate interosseous ligament

The scapholunate interosseous ligament (SLIL) is biomechanically important in maintaining wrist motion and grip strength in the hand, but its possible sensory role in the dynamic muscular stability of the wrist joint has not been examined. The aim of this study was to use immunohistochemical methods to analyze the general innervation and the possible existence of sensory corpuscles in the SLIL. The ligament was excised in its entirety from 9 patients. Antibodies against the low-affinity p75 neurotrophic receptor (p75) were used to reveal sensory corpuscles as well as general innervation. Furthermore, antibodies against the general nerve marker protein gene product 9.5 (PGP 9.5) and the glial marker S-100 were used to additionally depict innervation and corpuscular structures. Blood vessels occurred in areas interspersed throughout the homogeneous collagenous structure. In these vascularized areas, the SLIL was found to be supplied with nerve fascicles and sensory corpuscles of both the Ruffini and lamellated type. p75 immunoreactivity (IR) was detected in association with the nerve fascicles and the corpuscles, particularly in their capsule. S-100 IR was found in the Schwann cells in the central regions of the corpuscle, and PGP 9.5 IR marked the axonal structures in the corpuscles. New information on neurotrophin receptor distribution in ligaments has been obtained here. The presence of nerve fascicles and particularly sensory corpuscles in the SLIL suggests that the ligament has a proprioceptive role in the stability of the wrist. The marked p75 IR further indicates that neurotrophins play a part in a proprioceptive system in the ligament, given the importance of neurotrophins in maintaining sensory function.