Cyclic joint loading can affect the initial stability of meniscal fixation implants

Objective. To identify the effect of cyclic joint loads on the initial fixation strength of different meniscal repair techniques. Design. Three different meniscal refixation implants and one suturing technique were tested for initial stability in porcine knee joints after cyclic joint loading. Background. Existing studies tested the initial pull out strength of meniscal fixation implants. It remains unknown how such implants perform under cyclic joint loading. Methods. The Meniscal Fastener, the Meniscal Arrow, the ClearFix Screw, and a horizontal suture (PDS 1) were implanted in 64 porcine knee joints after setting a tear in the posterior horn of the medial meniscus. In one group of each device the menisci were excised directly after implantation and subsequently subjected to a pull out test. The knee joints of the other groups were exposed to 5000 axial load cycles between 10 and 200 N prior to the pull out test. Results. The horizontal suture showed the highest pull out force (103 N, SD 19 N). Arrow (52 N, SD 18 N), Meniscal Fastener (29 N, SD 3 N), and Meniscal Screw (22 N, SD 8 N) failed at significantly lower loads. Cyclic loading led to a decreased initial pull out force only for the horizontal suture (82 N, SD 26 N) and the Meniscal Fastener (23 N, SD 5N). Conclusions. Cyclic joint loading can lead to reduced fixation strength especially of meniscal refixation implants and sutures with relatively low stiffness. However, it remains unclear which fixation strength is necessary to provide conditions for meniscal healing.