Paper 90: Histopathology of Rotator Cuff Tendons in Elderly Patients with Glenohumeral Arthritis without Cuff Tears
Authors: Mori Daisuke 
Published: July 2022

Objectives: Some surgeons prefer reverse shoulder arthroplasty to total shoulder arthroplasty in elderly patients with osteoarthritis (OA) and without cuff tears because these patients may subsequently develop cuff tears. However, other studies have shown total shoulder arthroplasty provides good to excellent results in elderly patients with intact rotator cuffs, even in patients ≥ 80 years of age. We conducted the following studies to clarify potential rotator cuff degeneration in elderly OA patients, histologically analyzing the torn edges of ruptured rotator cuff tendons from patients with cuff tear arthropathy (CTA) with a proximal humeral fracture with an intact cuff (control) or en bloc cuff tendon remaining on the greater tuberosity from patients with OA after harvesting such tissues at the time of RSA. Then, we compared the clinical results of elderly patients undergoing total shoulder arthroplasty (TSA) and reversed shoulder arthroplasty (RSA) when these patients reached ≥ 80 years of age. We hypothesized that rotator cuff tendons were more severely degenerated microscopically in elderly patients with OA and intact cuff tendons compared with tendons in elderly patients with proximal humeral fractures, and comparable to those with CTA. Methods: We histologically evaluated torn rotator cuff tendon samples harvested from 13 samples in 11 shoulders in 9 patients with OA without cuff tears, 18 samples in 14 shoulders in 14 patients with CTA, and 2 shoulders in 2 patients with proximal humeral fractures using the Bonar score and electron microscopic analysis. In addition, we compared the clinical results of TSA in 7 shoulders in 6patients and RSA in 19 shoulders in 15 patients when these patients reached ≥ 80 years of age. Bonar scores were compared between the OA and CTA patients (OA and CTA groups), and Constant scores, and range of motion were compared between the two procedures (TSA and RSA groups). Two patients with proximal humeral fractures served as controls. We identified patients with secondary rotator cuff dysfunction by the presence of either moderate or severe superior subluxation of the humeral head base on radiographic assessment of humeral superior subluxation. Results: There were no significant differences in patients’ age, sex, BMI, heart disease, DM, hyperlipidemia, sample site, and preoperative Constant and ASES scores (except regarding the number of affected dominant arms), between the CTA and OA groups. There were no significant differences in the distribution of each category for tenocytes, ground substance, and collagen; and vascularity (P = .227 .107, .509, .848, respectively). In addition, there was no significant difference in the Bonar scores between the CTA and OA groups (P = .140). In the both groups, irregularly-orientated collagen fibers showing fiber separation and numerous blood vessels and inflammatory cells were observed in the sections with HE staining (Fig. 1A-C, A, OA patients; B and C, CTA patients). In the sections with AB/PAS staining, increase in alcianophilia indicating glycosaminoglycans among collagen fibers were observed (Figure 1, D, CTA patient). The control supraspinatus tendons from the patients of a four-part proximal humeral fracture demonstrated well-oriented collagen fibers with tightly cohesive well-demarcated bundles. The two control shoulders had 0 points and 2 points for the Bonar score, respectively (Figure 2). The ultrastructural analysis showed that collagen fibrils were arranged irregularly, with a heterogenous extracellular matrix, in the OA group. Similarly, in the CTA group, some collagen fibrils were oriented in different directions, and that there were empty spaces between the fibrils, representing non-collagenous extracellular matrix (Figure 3, A, C; OA patient, B,D; CTA patient). We found no significant difference in the fibril diameter (nm) between the two groups (mean,66.9 for the CTA group and 65.0 for the OA group) (P = .219) (Figure 3 C and D). There were significant improvements between preoperative and postoperative clinical scores in both groups. In addition, patients in the TSA group had significantly lower Constant scores, Constant ROM scores, and ROM in flexion and abduction at the final follow-up (P; .009, < .001, .003, .009, respectively). Upward migration of the prosthetic humeral head was observed in 7 shoulders (100%) overall and was graded as mild in 3 shoulders (42.9%), moderate in 4 shoulders (57.1%) as secondary cuff dysfunction. Conclusions: The most important finding in the present study was that rotator cuff tendons in elderly OA patients without cuff tears had relatively higher mean Bonar scores than the scores in the cuff tendons in two patients with proximal humeral fractures (control shoulders), and scores were comparable to the scores in cuff tendons in the elderly CTA patients. In addition, our clinical results showed that the TSA group had significantly lower clinical variables than those of the RSA group regarding the Constant score, Constant ROM score, and ROM in flexion and abduction in our cohort who were ≥ 80 years of age at the latest follow-up. Furthermore, 4 shoulders (57.1%) in the TSA group had moderate superior subluxation of the prosthetic humeral head as possible secondary cuff tendon dysfunction, at the final follow-up. Considering these histologic and clinical results, severe histological degeneration of rotator cuff tendons in elderly OA patients without cuff tears may be a risk of secondary rotator cuff dysfunction and poor clinical outcome after TSA.