Intramedullary versus extramedullary tibial alignment systems in total knee arthroplasty.

One hundred twenty consecutive total knee arthroplasties were performed to compare the accuracy of intramedullary versus extramedullary tibial resection guides. An intramedullary guide (group 1) was used in 60 cases and an extramedullary guide (group 2) was used in another 60 cases. In group 2, the distal portion of the extramedullary guide was shifted 3 mm medial to the midpoint of the ankle in order to position it over the center of the talus. Postoperative tibial component alignment angles were similar in both groups (group 1, 0.43 degrees varus; group 2, 0.36 degrees valgus). However, 88% of tibial components in group 2 were aligned within 2 degrees of the 90 degrees goal versus only 72% of tibial components in group 1. Satisfactory alignment can be obtained with either intramedullary or extramedullary resection guides, although a wider range of error was encountered with intramedullary guide use. Distal positioning of the extramedullary guide over the center of the talus rather than the midpoint of the ankle is important to avoid varus tibial resection. Extramedullary guides avoid the potential complications of intramedullary guide use, including fat embolization and hypoxia, intraoperative fracture, loss of polymethyl methacrylate pressurization, and inability of intramedullary rod passage due to deformity, retained hardware, or pathologic bone disease.