Abstract
Total knee arthroplasty (TKA) has been established as the most effective treatment
for end-stage, symptomatic osteoarthritis of the knee. However, improper polyethylene
size selection has been proposed to predispose patients to postoperative stiffness
following TKA. The aim of this study is to evaluate if there is a correlation between
the use of the thinnest tibial implant thickness and implant manufacturer with the
likelihood of undergoing manipulation under anesthesia (MUA). A retrospective review
of unilateral TKAs performed between January 2012 and November 2015 was performed.
Each knee implant system was normalized by total tibial component thickness for each
individual implant system (metal back plus polyethylene) and reaggregated to assess
the difference in MUA rates when comparing the thinnest tibial component thickness
against the next two sizes. Subset analysis was performed comparing the thinnest tibial
component thickness for each individual implant system versus (1) all other tibial
component sizes and (2) tibial components one and two sizes larger. A total of 2,728
patients were retrospectively evaluated, of which 71 (2.60%) underwent MUA. Combined
tibial component thickness ranged from 8 to 21 mm. When aggregated together to compare
the MUA rate between the thinnest liner and the next two sizes, no statistically significant
difference was observed (p = 1). Subset analysis demonstrated inconsistent significant differences in MUA rates.
Our results suggest that the polyethylene liner thickness alone is not a predictor
of postoperative knee stiffness necessitating MUA. When selecting a polyethylene liner,
a proper fit maximizing flexion/extension stability is the most crucial factor.
Keywords
total knee arthroplasty - polyethylene thickness - tibial resection - knee stiffness
- manipulation under anesthesia
