Biomechanical comparison of quadriceps tendon fixation with patellar tendon bone plug interference fixation in cruciate ligament reconstruction

Purpose: The purpose of this study was to use current fixation techniques a nd compare the stiffness and ultimate tensile failure of the tendinous end of the quadriceps tendon (QT) with the bone plug end of the bone-patellar t endon-bone (BPTB) graft using current techniques of fixation. Type of Study : Randomized trial of elderly cadaver knees. Materials and Methods: Tibial and femoral biodegradable interference fixation and femoral EndoButton (Smi th & Nephew, Acufex, Mansfield, MA) fixation in bone tunnels with the QT an d the BPTB graft were compared by using 10 pairs of elderly cadavers and bi omechanical testing, Two groups, fixation at time zero (simulating fixation in the operating room) and testing after 1,000 loading cycles (simulating patient rehabilitation exercises), were used. Results: At time zero fixatio n, stiffness of the soft tissue QT tibial tunnel interference fixation was 59% less stiff than the stiffness of the interference fixation of a BPTB pl ug in a femoral tunnel (P = .11). The EndoButton femoral fixation resulted in a decrease in stiffness at time zero compared with femoral tunnel interf erence fixation of the soft tissue QT (P = .03). All groups improved stiffn ess with cycling the construct to 1,000 cycles. Conclusions: Placement of t he QT tendinous end of the graft in the femoral bone tunnel when using a in terference fixation will approximate the stiffness of a bone plug in the ti bial bone tunnel with interference fixation. The EndoButton fixation is not as stiff as either of the femoral interference fixation options. The addit ion of more than 20 loading cycles could remove laxity from the graft fixat ion-graft cruciate ligament complex and improve its stiffness.