ANTERIOR CRUCIATE LIGAMENT GRAFT FIXATION - INITIAL COMPARISON OF PATELLAR TENDON AND SEMITENDINOSUS AUTOGRAFTS IN YOUNG FRESH CADAVERS

The initial biomechanical properties of semitendinosus and patellar te ndon autografts and their fixation strengths were investigated. Twenty fresh cadaveric knees from donors under 42 years of age were used in the study. After removing all soft tissues other than the anterior cru ciate ligament, we determined the ultimate tensile strength (2195 +/- 427 N) and stiffness (306 +/- 80 N/mm) of the anterior cruciate ligame nt in nine knees. In six knees, anterior cruciate ligaments were recon structed using an autologous patellar tendon graft with proximal and d istal interference fit screws; this resulted in an ultimate tensile st rength of 416 +/- 66 N. Five knees were reconstructed with quadruple-s tranded (double-looped) semitendinosus tendons fixed proximally by a t itanium button and braided tape and distally by tibial post screw. Thi s resulted in an ultimate tensile strength of 612 +/- 73 N, which was significantly higher than the strength in the patellar tendon group. G raft stiffness did not differ between the groups and was 47 +/- 19 N/m m (N = 11). This study demonstrates that the reconstructed knees had o nly 20% to 30% of the ultimate tensile strength of the normal anterior cruciate ligament. In summary, the semitendinosus reconstruction usin g a button for proximal fixation is, at the time of surgery, approxima tely 50% stronger than patellar tendon reconstructions with similar st iffness.