Loss of Tibial Bone Density in Patients with Rotating- or Fixed-platform TKA

Abstract

Little is known about tibial bone remodeling with TKA and its clinical relevance. We performed a randomized clinical trial to compare tibial bone density changes in cemented components with different bearing designs. Bone density changes were assessed using quantitative computed tomography (qCT)-assisted osteodensitometry. Twenty-eight rotating-platform and 26 fixed-platform cemented TKAs were included. The nonoperated contralateral side was used as a control. CT scans were performed postoperatively and 1 year and 2 years after the index operation. Cancellous bone density loss (up to 12.6% at 2 years) was observed in all proximal tibial regions in both cohorts. In contrast, we found lower cortical bone density loss (up to 3.6% at 2 years). We found no differences in bone loss between fixed-and rotating-platform implants. The decrease of cancellous bone density after TKA suggests stress transfer to the cortical bone.

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].…”

“…This model was chosen because it allows us to consider the effects of multiple variables on our primary variable (measured change in BMD). We previously used this statistical method in a similar study for TKA [16]. Before analysis, the Durbin-Watson test indicated the need to use this type of model to account for multivariate effect.…”

“…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].…”