A Prophylactic Tibial Stem Reduces Rates of Early Aseptic Loosening in Patients with Severe Preoperative Varus Deformity in Primary Total Knee Arthroplasty.

BACKGROUND

Patients with a preoperative varus deformity >8 degrees are at increased risk of aseptic loosening after total knee arthroplasty. This study analyzes the effect of a tibial stem on the rate of aseptic loosening in patients with a severe preoperative varus deformity.

METHODS

Patients with a preoperative varus deformity of >8 degrees and 2-year minimum follow-up with a stemmed tibial component (n = 67) were matched 1:2 to patients with a similar preoperative varus deformity with a standard tibial component (n = 134). Radiolucent lines were measured on the tibia at 6 weeks, 1 year, and 2 years postoperatively using the Knee Society Radiographic Evaluation System. Failure was defined as revision due to aseptic loosening of the tibial component. Outcomes were evaluated using Student's t-tests and log-rank tests.

RESULTS

Patients with tibial stems had greater preoperative deformity (12.9 vs 11.3 degrees, P = .004). There was no difference in postoperative alignment (1.7 vs 2.1 degrees varus, P = .25) or tibial component angle (1.8 vs 2.1 degrees varus, P = .33). Patients with stems were more likely to have more constraint (44.8% vs 1.5%, P < .001). Progression of radiolucent lines >2 mm was observed in 17.6% (23/134) vs 5.97% (4/67) of patients in the stem group (P = .03). Rates of aseptic loosening were lower in the stem group (0% vs 5.15%, P = .05).

CONCLUSION

Despite worse preoperative deformity and higher utilization of constraint, tibial stem use in patients with severe preoperative varus deformity resulted in lower rates of aseptic loosening. Prophylactic use of stems in these patients may help increase implant survival.