One year changes in bone mineral density of lumbar spine and femoral neck in patients aged 65 years and over undergoing total knee arthroplasty

Objective To determine the percentage of osteoporosis in patients undergoing total knee arthroplasty aged 65 years and over to determine the influence of total knee arthroplasty on general bone mineral density.Methods Thirty-eight patients were recruited between 2006 and 2007.The study population comprised patients with primary knee osteoarthritis.All the BMD of lumbar spine and femoral neck were measured using Dual energy X-ray absorptiometry(LEXXOS,DMS,France) preoperatively,3 months,6 months and 12 months after operation.HSS score was applied to evaluate the knee function.Results The average age was 71.7 years(range 65～83y).Twenty-four patients(63.2%) were combined with osteoporosis.The average range of motion of knee joint was 5°～85° and the median HSS score was 48 points(range 27～67 points) preoperatively.The lumbar spine and operated-sided hip showed no significant changes of BMD during the period of 6 months after prosthesis implantation(P0.05).In contrast,the average bone mineral density on the operated side and lumbar spine after 12 months increased when compared with the presurgical value(P0.05).Conclusion The percentage of comorbidity of osteoporosis was remarkably high in patients with degenerative osteoarthritis.The results indicated that osteoporosis should also be treated simultaneously after total knee arthroplasty.The general bone mineral density increased and the fracture risk of lumbar spine and hip decreased 12 months after total knee replacement.Total knee arthroplasty may improve the function of knee joint and reduce osteoporotic fractures.