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

• Published in: The Journal of arthroplasty 2018-08, Vol.33 (8), p.2512-2517
• Main Authors: Park, Min-ho, Bin, Seong-Il, Kim, Jong-Min, Lee, Bum-Sik, Lee, Chang-Rack, Kwon, Young-Hee
• Format: Article
• Language: English
• Subjects: propensity score matching; severe varus deformity; short extension stem; survivorship; total knee arthroplasty
• ISSN: 0883-5403; 1532-8406
• DOI: 10.1016/j.arth.2018.03.058

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. 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. 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). 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 III.