Abstract
Introduction:
Obesity is one of the biggest issues to harm health so as increase medical costs worldwide. Unfortunately, Japan is no exception. Under a big governmental campaign, obese rate in Japanese elderly begins to decrease very recently. However, we cannot help to have impression that our patients who undergo hip/knee replacement surgery have been getting heavier and heavier. The purpose of this study is to examine the change of body mass in our patients and find related factors.
Patients and methods:
We reviewed hospital record of patients who underwent knee or hip replacement from January 1 to December 31 in 2004 or 2012. Patient who underwent either unicompartmental or total knee arthroplasty was included, however, those who went through femoral head replacement (hemiarthroplasty) was excluded from this study population. Body mass index (BMI) was calculated from body height and weight measured within a week before surgery. Unlike in United States, BMI greater than 25 is categorized as obese, and below 18.5 is considered underweight in Japan. Additionally, gender, age at surgery, operated site (hip or knee), primary surgery or revision, blood loss in operation, surgery time, anesthesia time were evaluated as co-factors.
Results:
Overall, 48 patients from 2004 and 107 patients from 2012 were included to the study population. We included patients with osteoarthritis (OA), rheumatoid arthritis (RA), avascular necrosis (AVN), high energy trauma, low energy trauma, and psoriatic arthritis (PSO). Mean age of patients was 66 years old in 2004, and 68 years old in 2012. Table 1 summarizes characteristics of subjects. Mean BMI of all patients in 2004 was significantly lower than the one in 2012 (23.7 vs. 25.8, p = 0.0019). Especially, BMI of patients underwent knee replacement because of OA in 2012 was significantly higher than those who went through the surgery in 2004 (p = 0.083: Table 2). Whereas, BMI of THA patient with hip OA in 2012 was not significantly higher than in 2004 (p = 0.15). Focus to OA, obese patient was 19% with hip OA and 36% with knee OA in 2004. In 2012, more than 50% of knee OA patients were obese while obese hip OA patients were a little less than half of THA participants (47%: Figure 1). Perioperative blood loss, surgery time and anesthesia time showed significant decrease from 2004 to 2012.
Discussion:
Thanks to the great progress of biological treatment on RA, we perform less knee/hip replacement surgery among RA patients, and then majority of operated patients is now affected by osteoarthritis. According to a Japanese official report, obese rate of women age 40 to 69 was decreased to 23% in 2011 comparing to 24.6% in 2004. Regarding to Japanese age 70 and above, obesity rate is around 26% in both men and women, far lower than our study population of OA patients. In conclusion, BMI of our patients who underwent knee/hip replacement surgery became significantly higher during eight years and nearly half of operated knee/hip OA patients were obese last year.
