Intramedullary versus extramedullary tibial alignment guides in total knee arthroplasty

The intramedullary alignment guide is superior to the extramedullary guide for preparation of the femur in total knee arthroplasty. However, there is controversy over which guide is more appropriate for the tibial sector. We retrospectively compared the accuracy of the intramedullary and extramedullary guides for tibial cutting in patients undergoing total knee arthroplasty. Total knee arthroplasty was performed in 100 knees (68 patients) during a 2-year period. The intramedullary rod was used for preparation of the femur in all cases. For the tibia, each guide system was used in 50 knees. The intramedullary rod was not used in tibias with extreme deformity where the rod could not pass at least two-thirds of the way through the medullary canal. Standing anteroposterior radiographs of the hip to the ankle were taken before surgery and 2 to 6 months postoperatively. The angle formed by the intersection of the tibial mechanical axis and the undersurface of the tibial component (tibial component angle) was measured to check the accuracy of the tibial alignment system. We found no significant differences in the mechanical axis, tibiofemoral alignment, or the tibial component angle between the two groups. The proximal tibial cuts were within 2 degrees of the ideal (90 degrees) in 84% of knees treated with the intramedullary guide, and in 82% of those with the extramedullary guide (p > 0.1). These findings suggest that both guide systems can yield satisfactory alignment. If the tibia is not badly deformed, the intramedullary rod can produce tibial cuts as accurately as the extramedullary system.