DIFFERENCES IN THE REPAIR PROCESS OF LONGITUDINAL AND TRANSVERSE INJURIES OF CARTILAGE IN THE RAT KNEE

Objective: To clarify the relationship between type or direction of ca rtilage injury and its repair process, we investigated defects produce d in rat knees histologically, immunohistochemically, and histomorphom etrically. Methods: A full-thickness cartilage injury (1 mm wide and 5 mm long) was produced on the patellar groove of one knee (L-injury) a nd transversely on the other knee (T-injury) in 42 male Wistar rats. S ix rats each were sacrificed at 1, 2, 3, 4, 6 and 8 weeks after surger y, and cartilage tissues were obtained, prepared into 4 mu m-thick his tologic specimens, and stained with hematoxylin and eosin. Cartilage t hickness, cartilage area, and surface roughness were measured using a computer system. Localization of S-100 proteins was evaluated with imm unohistochemistry. Results: Grossly, there were no difference in repai r process between L-and T-injuries, However, histological and histomor phometric differences became apparent after the third week: cartilage thickness, repair area, and surface roughness showed better recovery i n L-injury than in T-injury. Appearance of S-100-positive protein prec eded the appearance of chondrocytes, and L-injury presented S-100 in t he entire defect while S-100 in T-injury appeared mainly on the margin s of the defect. Conclusions: Repair mechanism of cartilage injury dif fers according to injury direction. Better repair call be obtained in the injury which is parallel to the direction of joint motion.