Varus tension testing of fixation devices used in proximal tibial osteotomy.

Varus tension testing was performed on 26 matched pairs of tibias after high tibial osteotomy with three different fixation techniques--Coventry stepped staple, Mansat staple blade, and modified tension-band. Biomechanical testing revealed that in group I the Coventry stepped staple and Mansat staple blade yielded similar force at failure values of 132.44 +/- 29.29 and 137.34 +/- 40.84, respectively. In group II, the varus force at failure value was 170.45 +/- 83.95 for the modified tension band device versus 115.27 +/- 67.21 for the Coventry stepped staple device. In group III, the varus force at failure value was 180.26 +/- 82.36 for the modified tension band device versus 109.14 +/- 60.96 for the Mansat staple blade. The findings in this study suggest that the modified tension band technique provides a greater varus force at failure value, approximately 160-170%, compared to the other two techniques. In addition, this device is easy to apply and less expensive, and most orthopaedic surgeons are already familiar with its use.