The effect of posterior tibial slope on range of motion after total knee arthroplasty.

Posterior slope has been theorized as advantageous to range of motion (ROM) after total knee arthroplasty. This study was undertaken to assess the accuracy of a 0 degrees and a 5 degrees posterior sloped intramedullary (IM) cutting guide and the effect of the posterior tibial slope on postoperative ROM. Thirty-one consecutive patients underwent total knee arthroplasty using a cutting block and intramedullary cutting guide designed to impart a 0 degrees posterior tibial slope (group 1). A 5 degrees tibia cutting block was used in 30 subsequent patients (group 2). The posterior slope measurement represented the angle between a line drawn parallel to the articular surface and a line drawn perpendicular to the long axis of the tibia on a lateral radiograph. Mean postoperative tibial slope measured 1.8 degrees for group 1 and 5.5 degrees for group 2. There was no significant difference between groups for postoperative flexion or improvement of Hospital for Special Surgery score. The tibial cutting guides accurately achieved the intended posterior slope, but increasing posterior slope did not result in a significant increase in ROM or Hospital for Special Surgery functional score.