Prevalence of osteoporosis in female patients with advanced knee osteoarthritis undergoing total knee arthroplasty.

This study sought to demonstrate bone mineral density (BMD) conditions in elderly female patients with knee osteoarthritis (OA) undergoing total knee arthroplasty (TKA). In addition, we sought to determine whether their BMD conditions differ from those of community-based females without knee OA. Finally we sought to determine whether clinical statuses are related to BMD in the knee OA patients. BMD conditions in 347 female patients undergoing TKA and 273 community-based females were evaluated. Additionally, comparative analyses of BMD between age and body mass index-matched knee OA groups (n=212) and the control groups (n=212) were performed. In the pre-matched knee OA group, regression analyses were performed to determine whether preoperative clinical statuses were related to BMD. Considerable prevalence of coexistent osteoporosis (31%) was found in the pre-matched knee OA patients undergoing TKA. We found no significant differences of the BMD T-scores and the prevalence of osteoporosis between the age and body mass index-matched knee OA and control groups. In the pre-matched knee OA patients, poorer preoperative clinical scores were related to poorer BMD T-scores in the proximal femur and/or lumbar spine. Our study suggests that more attention should be paid to identify and treat osteoporosis in elderly female patients with advanced knee OA undergoing TKA. Graphical Abstract Keywords: Bone Density, Osteoporosis, Female Knee Osteoarthritis Patient, Arthroplasty, Knee INTRODUCTION Osteoarthritis (OA) of the knee is a common cause of pain and disability in the elderly (1). In the progressively aging population, the number of patients with advanced knee OA undergoing total knee arthroplasty (TKA) is increasing (2, 3). A female gender is another critical risk factor of advanced and symptomatic knee OA (4, 5). These two risk factors of advanced knee OA, aging and female gender, are also known to be major risk factors of osteoporosis, which is another issue of major concern (6, 7). Nonetheless, orthopedic surgeons, particularly those caring for patients with advanced knee OA, have shown relatively little interest in the management of osteoporosis (8, 9, 10). This may be due to the traditionally held belief that patients with advanced knee OA are less likely to develop osteoporosis. Several previous studies have reported the existence of an inverse relationship between osteoporosis and OA, particularly in the hip and knee (11, 12, 13, 14). Furthermore, a higher body mass index has been reported to increase the risks of the development and progression of OA of the knee (15, 16), but to decrease the risk of osteoporosis (17, 18). However, in our experience, a considerable proportion of elderly female patients with advanced knee OA undergoing TKA also have osteoporosis. These anecdotal observations seemingly contradict the previously held inverse relationship between knee OA and osteoporosis. However, this inverse relationship had been demonstrated by the studies using community-based populations with various stages of OA (11, 12, 13, 14); and it is still unclear whether this relationship would also be found in patients with advanced knee OA undergoing TKA. If our observation is the case, more functional deterioration in the knee OA patients might be related to lower bone mineral density (BMD) (19, 20). However, little information is currently available regarding this speculation. The first aim of this study was to demonstrate BMD T-scores and prevalence of osteoporosis in the elderly female patients with advanced knee OA undergoing TKA. The second aim was to determine whether elderly female patients with advanced knee OA undergoing TKA differ from age- and body mass index-matched community-based female cohort without advanced knee OA in terms of BMD T-scores and the prevalence of osteoporosis. The third aim was to determine whether preoperative clinical statuses are related to BMD T-scores in patients with advanced knee OA undergoing TKA.