ACCURACY OF INTRAMEDULLARY VERSUS EXTRAMEDULLARY TIBIAL ALIGNMENT CUTTING SYSTEMS IN TOTAL KNEE ARTHROPLASTY

The postoperative standing 51-inch radiographs of 352 total knee arthr oplasties were reviewed, The angle formed by the tibial tray to the me chanical axis of the tibia in the coronal plane was measured. The mean deviation from a perpendicular cut to the tibial mechanical axis was not significantly different between tibial cuts made with extramedulla ry alignment and with intramedullary alignment. With extramedullary al ignment, 92% of the cuts were +/-4 degrees of the ideal 90 degrees cut (perpendicular to the mechanical axis), whereas 94% of the cuts with intramedullary alignment were within 4 degrees of ideal. An analysis o f the cuts that erred greater than or equal to 4 degrees with intramed ullary alignment showed that for the majority the intramedullary guide rod, if passed down the middle of the tibial shaft in the coronal pla ne, directly led to the less than ideal cut. In these tibias, bowing d eformity in the coronal plane made passage of the intramedullary rod p arallel to the tibial mechanical axis impossible.