Introduction The tissue changes associated with spectrum of rotator cuff tendinopathy are poorly understood. The aim of this study was to describe the tissue characteristics of the onset and progression of rotator cuff tendinopathy by using a novel, ultrasound-guided biopsy technique to obtain tissue samples from the supraspinatus tendon in several accurately phenotyped groups representing the spectrum of rotator cuff tendinopathy from normal, healthy tissue through to patients with a full thickness tear of the supraspinatus tendon.
Methods Participants were grouped using ultrasound or arthroscopic diagnosis of cuff integrity and subdivided by the treatments being undertaken.
Control—under 35 years, no history of rotator cuff tendinopathy.
Injection—patients over 35 years with a history of rotator cuff tendinopathy without a full thickness tear undergoing subacromial injection of glucocorticoid.
SAD—patients over 35 years with a history of rotator cuff tendinopathy without a full thickness tear undergoing arthroscopic subacromial decompression due to failed glucocorticoid injection therapy.
FTT—patients over 35 years with a full thickness rotator cuff tear undergoing rotator cuff repair surgery.
Samples were taken under ultrasound guidance from the supraspinatus tendon. The biopsies were obtained in clinic under local anaesthetic for the injection group and in the operating theatre for the surgical and control groups. The tissue samples were wax embedded, sectioned and stained using the following markers: H&E to assess cellularity; CD34 to identify vascular endothelial tissue; CD45 Leucocyte common antigen to identify white cells as a marker of inflammation; MIB-1 to identify proliferating cells; Active Caspase-3 to identify cells undergoing apoptosis.
Slides were imaged using a Zeiss Axio Imager M1 light microscope. Analysis used computer software to calculate the cellular density from the H&E images and the proportion of positively stained tissue from the immunohistochemistry images.
Results Table 1 details the composition of the study groups. The quantitative histological analyses (figure 1) demonstrate a significant reduction in vascularity and cell proliferation in line with progression of pathology. There was no significant change in cellularity. A significant increase in inflammatory cells and apoptotic cells was seen in early tendinopathy represented by the injection group compared to controls.
Discussion This study has demonstrated significant changes in tissue characteristics across the progressive stages of rotator cuff pathology from a unique group of tissue samples obtained consistently from a focal area of the supraspinatus tendon in normal and tendinopathic tissue using a novel ultrasound guided biopsy method. The results suggest an early inflammatory component to the condition in patients with clinical signs of impingement but without tearing of the tendon. As the tendinopathy progresses to require subacromial decompression and eventually rotator cuff repair due to full thickness tearing of the supraspinatus tendon, the viability and healing potential of the tissue deteriorates significantly with reduced vascularity and proliferative activity within the tendon tissue.