Abstract
Bone mineral density (BMD) in the femoral condyle after total knee arthroplasty (TKA) was measured with the passage of time using DEXA. We evaluated it with X-rays and clinical findings. The subjects, whose average age was 71.6, were 8 patients (9 joints) with osteoarthritis and 3 patients (4 joints) with rheumatoid arthritis. The follow-up periods were from 12 months to 25 months, with the BMD of total skeleton (T), anterior (A) and posterior (P) femoral condyle measured at 1, 2, 3, 6 and 12 months. As the BMD in total skeleton changes in accordance with the bone metabolism of patients and their ages, the BMD was calculated from the BMD in total skeleton divided by that in ROI of A and P.
The A/T BMD decreased drastically, from 46.1% at one month to 29.0% at 3 months. There was a tendency of gradual decrease after that. However, though the P/T BMD decreased from 73.2% at one month to 50.8% at 3 months after TKA, it increased at 6 months, and did not show much change after that.
As for ROM, an A/T BMD of 43.0% was seen in knees with less than 90 degrees of flexion and of 23.5% in knees of over 110 degrees. Thus the A/T BMD showed a tendency to decrease in patients with a better range of knee motion. There also seemed to be a relationship between stress shielding and ROM.
