Clinical and radiologic effects of diaphyseal stem extension in noncemented total knee replacement

Abstract

Objective: To determine the clinical and radiologic effects of the addition of a diaphyseal stem extension to the tibial component in noncemented total knee replacement.

Design: A cohort study.

Setting: A university-affiliated institution specializing in elective orthopedic surgery.

Participants: One hundred and twenty-one patients with arthritis of the knee underwent noncemented total knee arthroplasty with a diaphyseal stem extension. All agreed preoperatively to prolong postoperative follow-up. Forty-six of the patients had a 100-mm stem extension, 56 had a 50-mm stem extension and 19, who had good bone with no intraoperative micromotion, had no stem extension. One patient died 6 weeks after operation and was excluded, leaving 120 knees available for study. Follow-up was 6 months to 3 years.

Intervention: Noncemented total knee replacement with the Tricon II prosthesis.

Main outcome measures: Clinical effects of the diaphyseal stem extension as determined by the Hospital for Special Surgery rating system and radiologic effects as determined by the Cameron classification.

Results: Clinically there was little difference between the three groups, with more than 90% in all groups scoring good or excellent. Radiologically, after elimination of single-zone lucency, both stem-extension groups showed a profound decrease in stem lucency. In patients who had a 100-mm stem extension, 90.9% had type IA lucency and 9.1% had type IB; no type II or type III lucency was seen. There was no correlation between radiologic and clinical results.

Conclusion: The addition of a diaphyseal stem extension to the Tricon II prosthesis reduces the amount of radiolucency in the tibial component in noncemented total knee replacement.