[Influence of body mass index and age on deep vein thrombosis after total hip and knee arthroplasty]

Abstract

Objective: To analyze the influence of the body mass index (BMI) and age on deep vein thrombosis (DVT) after the total hip arthroplasty (THA) or total knee arthroplasty(TKA) in Chinese patients who received prophylactic treatment for DVT.

Methods: We used a randomized clinical case-control study. From April 2004 to August 2004, we performed THA and TKA for 95 patients (128 hips and knees). There were 27 men and 68 women with an average age of 60 years (range, 23-78) at surgery, and with an average BMI of 25.88 kg/m2 (range, 14.34-40.39) before surgery. All the patients were given low-molecular-weight heparin for 7-10 days pre- and postoperatively to prevent DVT. Color Doppler ultrasonography was used to detect DVT of bilateral lower extremities in all the patients before operation and 7-10 days after operation. The patients were divided into 4 groups according to their BMI:the non-obese group (BMI < or = 25.00 kg/m2), the overweight group (BMI, 25.01-27.00 kg/m2), the obese group (BMI, 27.01-30.00 kg/m2), and the morbidly obese group (BMI > 30.00 kg/m2); and they were also divided into 4 groups according to their ages (< or =40, 41-60, 61-70, >70 yr) so as to analyze the influence of the BMI and age on DVT.

Results: The total incidence of DVT in all the patients was 47.4% (45/95) and the incidence of proximal DVT was 3.2%. Forty-five patients had DVT and 50 patients had no DVT. The average BMI of the patients with DVT was significantly higher than that of the patients with no DVT (P < 0.05). The overweight, obese, and morbidly obese patients had an odds ratio of 7.04, 4.8, and 9.6 for DVT compared with the non-obese patients (P < 0.05); but the obese group had a less risk than the other 2 groups. The 41-60, 61-70, and > 70-year-old patients had an odds ratio of 24.0, 38.2, and 24.4 for DVT compared with the < or = 40-year-old patients (P < 0.05).

Conclusion: Obesity (BMI> 25 kg/m2) and an increasing age (>40 yr) are identified as statistically significant risk factors for DVT after THA or TKA, and patients aged 61-70 years are more likely to have DVT than the other patients. We should pay more attention to those obesity and aged patients when they are undergoing the total joint replacement, and we should give them enough prophylaxis and closely observe the symptoms in their bilateral lower extremities after operation, taking ultrasonography or venography to check DVT if necessary, so that we can give them prompt treatment and prevent fatal pulmonary thromboembolism.