Delay of supraspinatus repair by up to 12 weeks does not impair enthesis formation: A quantitative histologic study in rabbits

Abstract

The purpose of this study was to find out whether supraspinatus repair delayed by up to12 weeks affects the formation of a new enthesis when compared to an immediate repair. In 67 rabbits, the supraspinatus fibrocartilaginous enthesis of one shoulder was resected. The tendon was attached to the greater tuberosity either immediately, after a 6-week, or after a 12-week delay. Five histologic variables were used to assess enthesis formation: number of non-chondrocytes, number of chondrocytes, alignment of chondrocytes in rows, area of metachromasia on toluidine blue (TB)-stained sections indicating proteoglycan content, and area of diffracted polarized light indicating spatial alignment of collagen fibers. For every variable, progressive enthesis formation was observed. Again, for every variable and at every time point studied, no statistically significant difference was observed between tendons repaired immediately, after 6, or after 12 weeks (all p>0.05). Supraspinatus tendon repairs delayed by 6 and 12 weeks constituted an enthesis which proceeded identically to one immediately repaired. Formation of a fibrocartilaginous enthesis depended on the elapsed time after repair and not on the duration between detachment and repair. Despite stated limitations, these results support both a trial of conservative treatment after a rotator cuff tear and a positive outcome of rotator cuff repair even if delayed by up to 12 weeks.

Contributions of the different rabbit models to our understanding of rotator cuff pathology

“…They repeated this study with the same method but delayed repair to either 6 or 12 weeks after rotator cuff injury. 16 They showed that although this delay in repair did not have an effect on enthesis formation, the formation of this fibrocartilaginous structure was dependent on the time elapsed after repair. These studies on the normal enthesis formation after surgical repair of the rotator cuff are critical as we move forward to determine better ways to improve healing.…”

rhPDGF-BB Promotes Early Healing in a Rat Rotator Cuff Repair Model

“…Image J (National Institutes of Health, Bethesda, MD, USA) software was used to determine the area of new fibrocartilage formation by manually outlining the metachromasia at the tendon-bone repair site on the safranin-O-stained slides at a total magnification of 9 40 on three sequential coronal sections. Total area of metachromasia was recorded for each specimen as squared micrometers and the mean ± SD for each group was determined [19].…”

Calcium-Phosphate Matrix With or Without TGF-β3 Improves Tendon-Bone Healing After Rotator Cuff Repair

“…The total area of metachromasia was recorded for each specimen. 23 Using polarized light microscopy, 2-week and 4-week tissue sections were stained with picrosirius red for semiquantitative analysis of collagen fiber alignment and organization at the repair site. By quantifying the collagen birefringence under polarized light, differences in collagen deposition and maturation in the healing tendon could be detected.…”