Noncemented stem tibial component in total knee replacement: the 2- to 6-year results.

OBJECTIVE

To determine if the addition of a stem to the tibial component in noncemented total knee replacement affects sinkage of that component or micromotion.

DESIGN

A cohort of 176 consecutive cases with no exclusions. Follow-up ranged from 2 to 6 years.

SETTING

A university-affiliated institution specializing in elective orthopedic surgery.

PARTICIPANTS

All 176 patients had arthritis of the knee, mainly osteoarthritis. 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 Special Surgery rating system for clinical results and degree of tibial sinkage and stem lucency seen radiologically.

RESULTS

Eight (4.5%) of the 176 prostheses required revision, none for sinkage. Of the remaining 168 knees, 156 (92.9%) scored good or excellent, 6% fair and 1.2% poor. Sinkage occurred in 3%, but was not of sufficient severity to require revision. No lucency was visible in 33.8% of stems, partial lucency in 62%, complete lucency with the lines being parallel to the stem in 3.5% and complete lucency with divergent lines, indicating a loose implant, in 1.7%. Lucency, when present, was seen mainly in the lateral view, seldom in the anteroposterior view. There was no correlation between radiologic results and clinical results.

CONCLUSIONS

The addition of a metaphyseal stem reduces the incidence of sinkage of the tibial component in total knee replacement. The stem largely solves the problem of mediolateral micromotion but does not completely prevent anteroposterior micromotion.