RESEARCH - Continue bisphosphonates after knee replacement to protect new joint

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Continue bisphosphonates after knee replacement to protect new joint

Rheumawire

Mar 3, 2006

Janis

Kaohsiung, Taiwan - The decrease in bone-mineral density (BMD) seen

after total-knee arthroplasty is suspected of weakening fixation of the

prosthetic joint. Short-term treatment with bisphosphonates such as

alendronate (Fosamax, Merck) after surgery can increase BMD around the knee,

but Dr Ching-Jen Wang (Chang Gung Memorial Hospital, Kaohsiung, Taiwan)

warns in the February 2006 issue of the Journal of Bone and Joint Surgery

that bones begin to soften again within 36 months if alendronate is

discontinued [1].

" It would be reasonable for the patient who has had total-knee

arthroplasty to take alendronate as a long-term maintenance regimen. This

would be especially important in patients with existing osteoporosis prior

to surgery, " Wang told rheumawire.

Alendronate maintains bone around knee prosthesis

This prospective, randomized study enrolled 60 women with

osteoarthritis (OA) who were about to undergo total-knee replacement.

Exclusion criteria included metabolic bone disease, rheumatoid arthritis

with osteoporosis, neuromuscular disorders, established osteoporosis that

required drug therapy, or a history of knee infection.

Patients were randomized to six months of treatment with oral

alendronate (10 mg/day) or to no treatment. Wang reported data for 54

patients who completed the trial (29 in the alendronate group, 25 in the

control group). BMD was measured by dual-energy x-ray absorptiometry (DEXA)

at baseline and six, 12, and 36 months after total-knee arthroplasty. BMD

changes in the proximal part of the tibia and distal part of the femur were

compared for the treatment vs control groups.

" In the control group, bone-mineral density decreased postoperatively

during the 36-month period. In the study group, bone-mineral density

initially increased at six and 12 months but decreased at 36 months, " Wang

writes. The changes were statistically significant at five and 12 months,

but the treatment group had lost as much BMD as the control group by the

36-month assessment.

Wang says that further work is needed to determine whether continuous

use of alendronate can maintain the BMD increases and " whether continued

therapy will protect the knee indefinitely. " Seki et al have reported that

that BMD can decrease by as much as 57% after total-knee arthroplasty, and

Wang said that similar bone loss has been reported after total-hip

replacement.

" We strongly feel that orthopedic surgeons should be more aware of

this problem and treat patients accordingly, " Wang said.

Source

1. Wang CJ, Wang JW, Ko JY, et al. Three-year changes

in bone mineral density around the knee after a six-month course of oral

alendronate following total knee arthroplasty. A prospective, randomized

study. J Bone Joint Surg Am 2006; 88:267-272.

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