Abstract
Incidences and risk factors for tibial component oversizing in total knee arthroplasty
(TKA) have been well described, predominantly in Caucasian samples. Component oversizing
has been linked to variations in proximal tibial shape and morphology, which has been
found to be objectively different in African Americans compared with Caucasians. These
anthropometric differences may affect the conformity of modern TKA systems to the
anatomy of African Americans undergoing TKA. We sought to investigate the incidence
and risk factors for tibial baseplate oversizing in an exclusively African American
population undergoing TKA with a symmetric tibial baseplate. We reviewed the records
of self-reported African American patients who had undergone a primary TKA at a single
academic institution between 2005 and 2016. The primary outcome was incidence of tibial
baseplate oversizing in the coronal and sagittal planes as determined by a single
set of appropriately rotated postoperative orthogonal radiographs. Logistic regression
models identified trends in oversizing within the population based on age, sex, body
mass index (BMI), and TKA model. Among all 525 knees being evaluated, the occurrences
of medial and lateral overhang were 14.2 and 15.2%, respectively. Increase in age
was associated with lower risk of medial tibial overhang (odds ratio = 0.97 for each
1-year increase in age). Simple linear regression models described a linear relationship
between BMI and overhang, with every one-unit increase in BMI, medial tibial overhang
is 0.031 mm higher and posterior tibial overhang is 0.062 mm higher. Mediolateral
oversizing was approximately twice more likely in females than males. Among TKA models
used, the Stryker Triathlon had the least risk for mediolateral oversizing and the
P.F.C. SIGMA demonstrated the least propensity for anteroposterior oversizing. To
conclude, incidence of mediolateral tibial oversizing in this population was common.
Previously identified variables affecting proximal tibial morphology, including age,
body morphotype, and gender, may be equally applicable to the conformity of tibial
baseplates in this population. Surgeons must pay particular attention to avoid mediolateral
tibial oversizing in this population, especially in obese and older patients.
Keywords
total knee arthroplasty - prosthesis implantation - rotation
