NONCEMENTED STEM TIBIAL COMPONENT IN TOTAL KNEE REPLACEMENT - THE 2-YEAR TO 6-YEAR RESULTS

Objective. To determine if the addition of a stem to the tibial compon ent in noncemented total knee replacement affects sinkage of that comp onent or micromotion. Design: A cohort of 176 consecutive cases with n o exclusions. Follow-up ranged from 2 to 6 years. Setting. A universit y-affiliated institution specializing in elective orthopedic surgery. Participants: All 176 patients had arthritis of the knee, mainly osteo arthritis. All agreed preoperatively to prolonged postoperative follow -up. Intervention: Noncemented total knee replacement with the Tricon M long-stem tibial component. Main Outcome Measures: Hospital for Spec ial Surgery rating system for clinical results and degree of tibial si nkage and stem lucency seen radiologically. Results: Eight (4.5%) of t he 176 prostheses required revision, none for sinkage. Of the remainin g 168 knees, 156 (92.9%) scored good or excellent, 6% fair and 1.2% po or. Sinkage occurred in 3%, but was not of sufficient severity to requ ire revision. No lucency was visible in 33.8% of stems, partial lucenc y in 62%, complete lucency with the lines being parallel to the stem i n 3.5% and complete lucency with divergent lines, indicating a loose i mplant, in 1.7%. Lucency, when present, was seen mainly in the lateral view, seldom in the anteroposterior view. There was no correlation be tween radiologic results and clinical results. Conclusions: The additi on of a metaphyseal stem reduces the incidence of sinkage of the tibia l component in total knee replacement. The stem largely solves the pro blem of mediolateral micromotion but does not completely prevent anter oposterior micromotion.