Abstract
Obesity is linked to early tibial tray failure after primary total knee arthroplasty
(TKA) for osteoarthritis (OA), especially in patients with preoperative varus. This
study compared standard and stemmed tibiae TKAs in patients with class I and II obesity
with varus deformity. Between April 2013 and June 2020, a prospective study was conducted
including patients with end-stage OA, body mass index between 30 and 40 kg/m2 , and varus <15 degrees. Patients were randomly assigned to TKAs with either standard
or long-stemmed tibiae and evaluated 5 years after surgery using the Knee Society
Scoring (KSS). The knee society and modified radiographic evaluation systems were
used for radiological evaluation. In total, 264 TKAs were performed in 264 patients
(134 in the standard group and 130 in the stemmed group). The mean preoperative hip–knee–ankle
angles for the standard and stemmed groups were 8.2 ± 3.2 degrees/varus and 9 ± 2.9 degrees/varus,
respectively (p = 0.2), which improved to 5.1 ± 3 degrees/valgus and 5 ± 3.5 degrees/valgus after
surgery (p = 0.52). There was no statistically significant difference between the objective
KSS (92 vs. 92.9; p = 0.84) and the functioning KSS (73.4 vs. 74.8; p = 0.28). There were no aseptic loosening cases or radiographic differences. In-group
analysis revealed significant outcomes differences in both groups if preoperative
varus was >10 degrees irrespective of the stem design (p < 0.0001). Complications occurred in two patients; one with a late infection and
one had a stem-related tibial fracture. Standard tibia TKAs yielded comparable results
in obese patients to long-stemmed tibias. No aseptic tibial loosening was observed
regardless of stem type, and worse clinical outcomes were associated with greater
varus.
Clinical trial registry: registered at http://www.researchregistry.com (researchregistry5717).Level of Evidence II; a prospective randomized trial.
Keywords obesity - primary total knee arthroplasty - stemmed tibia - aseptic loosening
