Prophylactic Tibial Stem Fixation in the Obese: Comparative Early Results in Primary Total Knee Arthroplasty

PURPOSE: Obesity is a risk factor for aseptic loosening after total knee arthroplasty (TKA). Prophylactic use of tibial stems may enhance tibial fixation in obese patients. The aim of this study was to determine whether a tibial stem extension decreases rates of early failure in obese patients. MATERIALS AND METHODS: This study included 178 consecutive primary TKAs (143 patients) with a body mass index ≥35 kg/m2. Fifty TKAs were performed with the use of a 30 mm tibial stem extension, and 128 TKAs were performed with a standard tibial component. Patients with two-year clinical follow-up were included. The primary outcome was revision for aseptic loosening. Secondary outcomes were all-cause revision and radiolucent lines (RLLs) on radiographs. RESULTS: Average follow-up was 34 months (range, 24 to 46 months). No failures for aseptic loosening occurred. The occurrence of secondary procedures was not significantly different between groups. Quantification of RLLs revealed no difference between groups. CONCLUSIONS: At early follow-up, no difference was measured in revision rates, need for subsequent procedures, or RLLs between groups.

Prospective Study of Central versus Peripheral Obesity in Total Knee Arthroplasty

PURPOSE: Body mass index (BMI) is often used to predict surgical difficulty in patients receiving total knee arthroplasty (TKA); however, BMI neglects variation in the central versus peripheral distribution of adipose tissue. We sought to examine whether anthropometric factors, rather than BMI alone, may serve as a more effective indication of surgical difficulty in TKA. MATERIALS AND METHODS: We prospectively enrolled 67 patients undergoing primary TKA. Correlation coefficients were used to evaluate the associations of tourniquet time, a surrogate of surgical difficulty, with BMI, pre- and intraoperative anthropometric measurements, and radiographic knee alignment. Similarly, Knee Injury and Osteoarthritis Outcome Score (KOOS) was compared to BMI. RESULTS: Tourniquet time was significantly associated with preoperative inferior knee circumference (p=0.025) and ankle circumference (p=0.003) as well as the intraoperative depth of incision at the quadriceps (p=0.014). BMI was not significantly associated with tourniquet time or any of the radiographic parameters or KOOS scores. CONCLUSIONS: Inferior knee circumference, ankle circumference, and depth of incision at the quadriceps (measures of peripheral obesity) are likely better predictors of surgical difficulty than BMI. Further study of alternative surgical indicators should investigate patients that may be deterred from TKA for high BMI, despite relatively low peripheral obesity.