Biomechanics and Motion Analysis

'High Definition' 3-D Imaging of Mechanoreceptors in Dorsal Radiocarpal Ligament of Human Wrist

Principal Investigator: Richard A. Berger, M.D.
Project Coordinator: Evelyn Berger — berger.evelyn@mayo.edu

Figure 1: Reconstructed 3-D image.

Freeman and Wyke developed the first classification scheme for joint mechanoreceptors based upon studies using traditional histological staining methods from light microscopy. However, utilizing a newly developed protocol of nerve-specific fluorescent immunohistochemistry and confocal laser microscopy, we have observed a quantum leap in the specificity and resolution of joint mechanoreceptors and seen a large number of receptors that defy the Freeman and Wyke scheme. The study reports “high-definition” three dimensional characteristics of mechanoreceptors found in the human dorsal radiocarpal (DRC) ligament of ten fresh cadavers. Labeled mechanoreceptors were measured, reconstructed 3-dimensionally and categorized (Fig. 1). Many mechanoreceptors had similar shape characteristics. The average long axis of mechanoreceptors consistent with the Type I category was 222m (55-650). Those mechanoreceptors were olive shaped, spherical and oval. The long axis of mechanoreceptors with the Type III was 365m (80-900). Those were rectangular, cylindrical and fusiform shapes. The shapes agree, but there is a large discrepancy in the sizes. Over 25% of the mechanoreceptors defied classification, and are thus in a new group called NOTT (nontype one, two, three). Combined fluorescent immunohistochemistry and confocal technology provide “high definition” imaging that significantly increases the analysis of the morphology and the 3-D measurements of joint mechanoreceptors, afferent nerves. We are grouping them into a new category called NOTT which awaits further study and definition.

These findings suggest that in patients with CTS the fibrosis of the SSCT has altered the gliding characteristics of the tendons, which may affect their ability to effectively and efficiently transmit load to the fingers, or to glide independently from each other, or from the nearby median nerve.