RADIOLOGIC STUDY OF THE ACCURACY OF A TIBIAL INTRAMEDULLARY CUTTING GUIDE FOR KNEE ARTHROPLASTY

Twenty-one caucasian, adult cadaveric tibiae were prepared as for knee arthroplasty using an intramedullary cutting guide. The instrumentati on was used to produce slots in the proximal tibia into which Kirschne r wires were placed as radioopaque markers for subsequent anteroposter ior and lateral radiographs. The anatomic axis of the tibia and lines perpendicular to the wire markers were drawn on the radiographs and th e angle between the two lines was measured to assess the accuracy of t he cuts. Seventy-one percent of the tibial cuts were found to be withi n 2 degrees of the anatomic axis on the anteroposterior radiograph (me an, 2.1 degrees), while on the lateral radiograph, 81% of the cuts wer e within 2 degrees (mean, 1.8 degrees). There was a significant tenden cy to position the bone cuts in varus (P < .05), although this did not correlate with varus or valgus deformity of the bones. There was no c onsistent tendency to anterior or posterior tilt on the lateral radiog raph (P >.05). The results compare favorably with those obtained from a specialist unit using an extramedullary alignment system. The author s conclude that the tibial intramedullary guide can lead to preparatio n of the proximal tibia for knee arthroplasty as accurately as the con ventional extramedullary system.