Mechanical comparison of fixation techniques for the tibial tubercle osteotomy

Tibial tubercle osteotomies currently are used as an exposure technique for revision total knee arthroplasty and for distal patellofemoral realignment . A review of the literature reveals no biomechanical studies that evaluate methods of osteotomy fixation in terms of static strength. This study eval uates the fixation strength of common techniques used to repair tibial tube rcle osteotomies. Bevel and stepcut tibial tubercle osteotomies were create d in 36 anatomic specimen knees and were repaired with either two 4.5-mm co rtical screws or 18-gauge stainless steel cerclage wire. The failure load f or the bevelcut osteotomies repaired with two-screws was 1654 +/- 359 N; fo r the bevelcut osteotomies repaired with three cerclage wires, 622 +/- 283 N; for the stepcut osteotomies repaired with three cerclage wires, was 984 +/- 441 N; and for the stepcut osteotomy repaired with four cerclage wires, 1099 +/- 632 N. This study shows that two bicortical screws provide the gr eatest static fixation strength for repairing tibial tubercle osteotomies. When repairing tibial tubercle osteotomies for distal patellofemoral realig nment, screw fixation would provide the most reliable fixation. However, th e placement of screws around the stem of a revision arthroplasty tibial com ponent is difficult. Cerclage wires are easier to place and provide solid s tatic fixation, especially with the addition of a proximal stepcut osteotom y.