Histological Evaluation of Early-Phase Changes in the Osteochondral Unit After Microfracture in a Full-Thickness Cartilage Defect Rat Model:

Background:The microfracture (MF) technique is an established surgical treatment for cartilage injury. However, the early-phase histological changes in full-thickness cartilage defects (FTCDs) after MF and the concomitant changes in the subchondral bone are still unknown.Purpose:To determine the early-phase histological changes in FTCD associated with subchondral bone remodeling after MF in rat model.Study Design:Controlled laboratory study.Methods:Rats were subjected to FTCD, followed by MF at the trochlear groove. For histological analysis, experiment and untreated control rats were sacrificed at 0, 1, 3, 7, 14, 28, and 56 days postoperatively (n = 6 knees per time point). Cartilage healing response was evaluated with the Pineda score. Osteoclast activity was evaluated by counting and locating the number of tartrate-resistant acid phosphatase (TRAP)–positive cells in the subchondral bone. MF hole diameter and bone mineral density in the subchondral bone were measured sequentially in 3 rats (n = 6 knees)...