The Journal of Arthroplasty , Volume 33 , Issue 8 , 2512 - 2517

Using a Tibial Short Extension Stem Reduces Tibial Component Loosening After Primary Total Knee Arthroplasty in Severely Varus Knees: Long-term Survival Analysis With Propensity Score Matching

Park, Min-ho et al.
Knee

Background

Patients with severe preoperative varus deformity have been reported to have high rates of loosening after total knee arthroplasty (TKA), primarily on the tibial side. This study investigated whether a short extension stem for the tibial component in severely varus knees would reduce the failure rate due to loosening on the tibial side.

Methods

Patients who underwent TKA, performed by a single surgeon using a single implant between November 1998 and January 2009, were retrospectively evaluated. Patients diagnosed with primary osteoarthritis, having a hip-knee-ankle axis greater than varus 8° on preoperative long-film radiographs, and postoperatively followed up for more than 2 years were included. Patients were divided into “stem” and “nonstem” groups, followed by 1:1 propensity score matching according to age, gender, body mass index, preoperative mechanical axis, and postoperative alignment. Tibial loosening rates in the 2 groups were compared.

Results

The study cohort included 602 patients, divided into “stem” and “nonstem” groups. Propensity score matching yielded 88 pairs of patients. Mean follow-up duration was similar in the stem and nonstem groups (109.22 vs 103.81 months, P = .451). None of the patients in the stem group, compared with 5 in the nonstem group, experienced aseptic loosening. The overall implant survival rate was significantly higher in the stem group than in the nonstem group (P = .0201).

Conclusion

Using a short extension stem for the tibial component in primary TKA in patients with severe varus deformity greater than 8° may reduce the rate of loosening of the tibial side and increase the longevity of the implant.

Level of evidence

Level III.


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