Peri-prosthetic bone mineral density after total knee arthroplasty

Abstract

We compared peri-prosthetic bone mineral density between identical cemented and cementless LCS rotating platform total knee arthroplasties. Two matched cohorts had dual energy x-ray absorptiometry scans two years post-operatively using a modified validated densitometric analysis protocol, to assess peri-prosthetic bone mineral density. The knee that was not operated on was also scanned to enable the calculation of a relative bone mineral density difference. Oxford Knee and American Knee Society scores were comparable in the two cohorts. Statistical analysis revealed no significant difference in absolute, or relative peri-prosthetic bone mineral density with respect to the method of fixation. However, the femoral peri-prosthetic bone mineral density and relative bone mineral density difference were significantly decreased, irrespective of the method of fixation, particularly in the anterior distal portion of the femur, with a mean reduction in relative bone mineral density difference of 27%. There was no difference in clinical outcome between the cemented and cementless LCS total knee arthroplasty. However, both produce stress-shielding around the femoral implants. This leads us to question the use of more expensive cementless total knee components.

Proximal Tibial Bone Density Is Preserved After Unicompartmental Knee Arthroplasty

“…Based on reports of BMD loss in other studies [1,13,16], we do not believe BMD loss less than 5% will make a difference to implant survival or function with UKA. Demographic data were similar for the two patient groups ( Table 1).…”

“…Fourth, our study was only powered to detect a 5% difference in BMD and may be underpowered to detect a smaller change than this. As mentioned earlier several studies [1,13,16] have not been able to correlate implant migration and failure with BMD loss well above 5% (Table 4). We do not believe a smaller loss of BMD would result in migration and loosening of UKA components.…”

“…Tibial BMD decreases after TKA [1,13,15,16,18,20,28] (Table 4). This has been suggested as a factor contributing to implant migration and loosening in TKA [18,31] and UKA [14,29,30].…”

“…Tibial bone mineral density (BMD) decreases after TKA by 5% to 12% at 2 years [1,16,28], 26% at 5 years [20], and by as much as 36.4% at 8 years [13]. Although these studies with limited numbers did not correlate BMD loss with clinical failure, some authors believe diminished BMD is a factor in implant migration and loosening [18,31].…”

Do bisphosphonates reduce early micromotion and Periprosthetic bone loss in total knee arthroplasty? A review of the evidence

“…Second, since uncemented implants are thought to promote periprosthetic BMD by improving stress transfer to trabecular bone, the effect of bisphosphonates may go undetected [7]. However, a two-matched cohort study has recently failed to demonstrate periprosthetic BMD difference between cemented and uncemented fixation of the same type of implant for TKA [13].…”