Histological Effects of PRP and Corticosteroids Following In Situ Repair of Bursal-Sided Partial Rotator Cuff Tears: An Experimental Rat Study.

Background/Objectives: This study aimed to compare the histopathological effects of subacromial corticosteroid (CS) and platelet-rich plasma (PRP) injections following in situ repair of bursal-sided partial supraspinatus tears in a rat model. Methods: Twenty-seven Wistar Albino rats were included in the study. Partial bursal-sided supraspinatus tears were surgically created and repaired in situ. Animals were randomly assigned to receive a subacromial injection of 0.6 mL of normal saline (control), methylprednisolone sodium succinate (CS; 4.8 mg/kg, 0.6 mL), or 0.3 mL of activated PRP per rat. After four weeks, the repair sites were harvested for histopathological evaluation of cellular morphology, apoptosis, collagen organization, and vascularity. Results: PRP preserved the normal spindle-shaped morphology of tendon cells at the osseotendinous junction, whereas CS induced a rounded cellular morphology (p < 0.05). CS significantly increased apoptosis scores (p < 0.05), while PRP showed apoptosis scores comparable to those of the control group (p > 0.05). Collagen organization was preserved in the PRP group but significantly disrupted following CS administration (p < 0.05). Vascularity was higher in the PRP group than in the CS group (p < 0.05); however, the vascularity findings should be interpreted cautiously. Conclusions: Following in situ repair of bursal-sided partial rotator cuff tears, PRP preserved tendon architecture and was associated with a more favorable histopathological profile than corticosteroids. In contrast, CS adversely affected histopathological characteristics by increasing apoptosis and disrupting cellular morphology and collagen organization. These findings suggest that PRP may represent a biologically favorable adjunct following in situ repair of partial-thickness rotator cuff tears; however, the present histopathological findings do not establish accelerated healing, functional superiority, or clinical benefit, and further clinical studies are needed to determine whether these histopathological differences translate into improved clinical outcomes.