Innervation pattern at the undersurface of the extensor carpi radialis brevis tendon in recalcitrant tennis elbow.

We investigated the general, sensory, and sympathetic innervation patterns at the undersurface of the extensor carpi radialis brevis (ECRB) origin in patients with recalcitrant tennis elbow. Eight elbows in eight consecutive patients (6 females and 2 males) with tennis elbow who underwent arthroscopic surgery were included in this study. The mean age was 45 years (38-66 years), and the mean duration of symptoms before surgery was 23 months (13-52 months). Operative treatment consisted of an arthroscopic inspection and debridement of the ECRB origin. Control tissues were obtained from biopsy of the ECRB capsule in two patients with osteochondritis dissecance of the capitellum who underwent arthroscopic resection of loose bodies. The tissue specimens were investigated immunohistochemically with antibodies delineating general (PGP9.5), sensory (SP/CGRP), and sympathetic (NPY) nerve patterns. In the non-tendinosis control tissue, SP/CGRP and NPY immunoreactions were heterogeneously distributed in association with blood vessels. Pathologic evaluation of the biopsy tissue showed atypical fibrous granulation containing numerous vessels and nerve structures in all eight patients. Marked reactions to PGP 9.5 took the form of nerve fibers associated with arteries and arterioles in the atypical granulation. Most of the perivascular innervation was found to express NPY. The immunoreactions for SP and CGRP were invariably weak. Increased perivascular sympathetic innervation accompanied with loss of sensory innervation at the undersurface of the ECRB tendon may play a role in chronic pain generation in recalcitrant tennis elbow. Diagnostic, Level IV.