Risk Factors for Tibial Component Oversizing in Total Knee Arthroplasty among African Americans

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.