Histologic and ultrastructural degeneration of rotator cuff tendons in elderly patients with glenohumeral arthritis and cuff tear arthropathy

Abstract

Background

This study aimed to examine the degree of rotator cuff (RC) tendon histological degeneration in elderly patients with osteoarthritis (OA) without RC tears, patients with cuff tear arthropathy (CTA), and those with proximal humeral fractures.

Methods

RC tendon samples were harvested from 13 shoulders in 10 consecutive OA patients without RC tears (mean age, 77.6 (71–83) years; number of samples = 15; OA group) and 20 shoulders in 20 consecutive CTA patients (mean age, 77.4 (70–87) years; number of samples = 24; CTA group) at the time of reverse shoulder arthroplasty between February 2018 and March 2022. Additionally, we harvested the supraspinatus tendons in two shoulders in two patients who underwent surgery for a proximal humeral fracture, which served as the control group. Histological and ultrastructural characteristics were assessed using light and transmission electron microscopy, respectively. The results of the light microscopic analysis were classified using the Bonar score.

Results

The mean Bonar score did not differ significantly between the OA and CTA groups (5.7 vs. 6.4, respectively; P = 0.160). The mean Bonar score was higher in the OA and CTA groups than scores in the control patients (0 and 2 points, respectively). In the OA and CTA groups, collagen fibers were irregularly orientated and separated; several blood vessels and inflammatory cells were also observed. The supraspinatus tendons from the fracture patients demonstrated well-oriented collagen fibers with tightly cohesive, well-demarcated bundles. The ultrastructural analysis showed that collagen fibrils were arranged irregularly within a heterogenous extracellular matrix in the OA and CTA groups. Fibril diameter did not differ significantly between the groups (P = .219). The distribution of fibril diameters was similar in both groups.

Conclusions

Our histologic and structural results showed that rotator cuff tendons in elderly OA patients without RC tears had relatively high mean Bonar scores, indicating degenerative change of the tendon, which was comparable to the degree of tendon degeneration in elderly CTA patients. In elderly OA patients, it is important to recognize that some degree of tendon degeneration may exist even in patients without RC tears.