Sensory nerve endings in the coracoacromial ligament and in the periligamentous bursal tissue were observed under a light microscope. The specimens were immunohistochemically stained with a protein gene product 9.5 (PGP9.5) and Calcitonin-Gene Related Peptide (CGRP). Two distinct nerve endings (Ruffini corpuscles and free nerve endings ) were identified in the periligamentous bursal tissue with PGP9.5.
CGRP positive nerve fibers were similarly stained with PGP9.5 except those around vessels and Ruffini corpuscles.
The results of the quantitative analysis of nerve fibers showed that in each staining method the average density on the coracoidal side of the coracoacromial ligament and periligamentous bursal tissue resected from patients with a rotator cuff tear was higher than that on the acromial side. it is of great interest that the average nerve density on the coracoidal side was higher than that on the acromial side with each staining method, which suggests that not only free nerve endings on the acromial side but also those on the coracoidal side must be involved in the pain of rotator cuff tears.
