Biomechanical effects of meniscal repair techniques on articular contact pressure at various knee flexion angles (SS-23)

      Objective: Articular cartilage injury can occur after meniscal repair with biodegradable implants. Previous contact pressure analysis of the knee have been based on the tibial side of the meniscus at limited knee flexion angles. We investigated articular contact pressures on the posterior femoral condyle with different knee flexion angles and surgical repair techniques. Methods: Medial meniscus tears were repaired in 30 fresh bovine knees (10 suture, 10 biodegradable screw implant, 10 biodegradable arrow implant). Knees were mounted on a 6 degrees-of-freedom jig and statically loaded to 200 N at 45, 70, 90, and 110 degrees of knee flexion under three conditions: normal meniscus, with 2 cm posterior medial meniscal vertical tear, and after repair of tear. For each repair, three sutures or biodegradable implants were used. A Tekscan pressure sensor was used to determine the contact area and peak pressure. Peak pressures over each implant position were also measured. Statistical analysis was preformed using the ANOVA test and P < .05 defined statistical significance. Results: Peak pressure increased significantly as knee flexion increased in normal, injured, and repaired knees. The change in peak pressure in knees with implant repairs were significantly higher than suture repairs at all knee flexion angles. The most medial and/or middle implant had higher peak pressures among the 3 implants, but statistical significance was found only with the biodegradable screw. Conclusions: Articular contact pressure on the posterior femoral condyle increases with knee flexion. Meniscal repair with biodegradable implants showed higher peak pressure than suture repair, particularly at the most medial location. Implants in the more posterior meniscus demonstrated smaller increases in peak pressure, and may have less potential for articular cartilage injury. These results suggest that avoidance of deep knee flexion angles postoperatively may limit increases in articular contact pressures and potential chondral injury.