Joint capsule innervation does not explain the difference in symptoms between scaphotrapezial and trapeziometacarpal...

Peritrapezial osteoarthritis (OA) includes scaphotrapezial and trapeziometacarpal OA. In clinical practice, scaphotrapezial OA seems better tolerated than trapeziometacarpal OA, with fewer complaints and better tolerance. The difference in pain could be linked to a difference in joint capsule innervation, perhaps with fewer nerve fibers in the scaphotrapezial than the trapeziometacarpal joint.

We performed a histologic evaluation of these two joints to compare their respective innervation in 17 cadaveric specimens with peritrapezial OA. Radiographic scoring confirmed the presence of peritrapezial OA. Mean Kellgren-Lawrence score was 2.2 ± 1.1 in the trapeziometacarpal joint and 1.5 ± 0.7 in the scaphotrapezial joint (p = 0.08).

There was no difference between scaphotrapezial and trapeziometacarpal joints in number of neurofilaments: 5.2 ± 3.9 and 4.4 ± 4.5, respectively (p = 0.20). A significant difference was found in S100 staining (myelinated structures), with a higher rate in the scaphotrapezial joint: 11.8 ± 7.5 vs 6.6 ± 5.2 (p = 0.005).

The present study suggests that lower tolerance of trapeziometacarpal OA is not due to a difference in joint capsule innervation. On the contrary, we found a higher rate of myelinated tissues in the scaphotrapezial joint. These results suggested other pain pathways to explain clinical observations.