The effect of a meniscal prosthesis on knee biomechanics and cartilage

A meniscal prosthesis made of Dacron with polyure thane coating was tested as a substitute for the medial meniscus in a rabbit experimental model concentrating on biomechanical behavior of the knee joint and gross and histologic evaluation 3 months after surgery. The results were compared to sham-operated knees, knees with a peripheral incision of the medial meniscus, and knees with a total meniscectomy. Knees with prosthe sis implantation had the same stiffness as knees with sham-operation or meniscal incision, but knees with meniscectomy were stiffer (P < 0.05). Knees with pros thesis showed lower energy storage during relaxation than knees with sham-operation or meniscal incision (P < 0.05). Energy storage in the prosthesis group was similar to the meniscectomy group. Partial or total ingrowth of synovial tissue into the prosthesis was present in 93%, and 63% of the incised menisci had healed. Cartilage changes were present in 70% of the prosthesis group, in 25% of the knees with meniscal incision, and in all knees with meniscectomy. The sham- operated knees were free from cartilage degeneration. Knees with prosthesis had the same frequency of car tilage changes on the femur, but had less changes on the tibia compared to knees with meniscectomy. A high rate of osteophyte formation was observed after pros thesis implantation as well as following meniscectomy, but the osteophytes were larger in the prosthesis group (P < 0.01). The most frequent and severe effect on the synovium was found in the prosthesis group (92%), but no foreign body reaction or loose Dacron particles were found. The Dacron prosthesis had a cartilage-protecting effect, but the biomechanical behavior of the knee joint was similar to meniscectomy. Knees with peripheral meniscal incision were similar to sham-operated knees.