O1078 FIXATION STRENGTH OF HAMSTRING FIXATION METHODS WITH ABILITY FOR CIRCUMFERENTIAL GRAFT INGROWTH. EXPERIMENTAL STUDY WITH RSA

Abstract

Aims: The purpose was to evaluate the biomechanical properties of Hamstring graft fixation methods with ability for circumferential graft ingrowth in a standardized experiment with high precision Radiostereometric Analysis (RSA). Methods: We used 30 porcine specimens for the study. A fourstranded graft was sutured with a baseball stitch. Ten trials were performed in each group. The sutured end of the graft was fixed with a Washer-Lock (WL) or two resorbable Cross-Pins (CP). In the Suture-Disc (SD) group 8 polyester sutures (Ethibond 5USP) were knotted over a titanium button. The tibial bone and the tendon-graft were marked with tantalum beads. The grafts were loaded axially under RSA control increasing the force in steps of 50N to load of failure. Micromotion between tendon graft and tibial bone was measured with RSA. Results: Load at failure was significantly higher for the WL and CP fixation (722±173N; 647±129N) compared to SD fixation (445±37N). Stiffness of fixation was significantly higher for WL and CP fixation 492N/mm; 416N/mm) compared to SD fixation 111N/mm). Graft displacement started at low loads for SD fixation (47N) compared to WL and CP (344N; 250N). Graft motion at 200N load was significantly higher in the SD group (1.85mm) than for the WL (0.33mm) and CP (0.3mm) fixation. Bungee cord effect at 200N for the SD was measured 1.32mm, for the CP 0.50mm and for the WL 0.22mm in average. Conclusions: Direct fixation of a quadrupled tendon graft with WL or CP is preferable to SD fixation. Low linear stiffness of SD fixation with linkage suture material allows for a high amount of elastic deformation.