Abstract
Purpose
Aseptic loosening of the tibial component of total knee prosthesis is a common cause of revision surgery. While micromotion at the bone-implant interface can now be accurately measured with Radiostereometric Analysis (RSA), mechanisms responsible for loosening remain poorly understood. The purpose of this study was to investigate the association between bone density in the proximal tibia and post-operative knee implant migration.
Method
Fifty-one subjects who received total knee arthroplasty surgery with the Wright Medical Advance Biofoam (uncemented) implant were recruited. Bone density of seven regions of the proximal tibia (medial, lateral, anterior, posterior, and three regions below implant tip) was measured with DEXA post operatively at two, six, 12 and 24 weeks. RSA exams were also taken immediately post-operatively, and at six, 12 and 24 weeks. Correlations between bone mineral density and RSA migration were examined at 24 weeks post-operatively.
Results
There was no significant correlation between bone density and maximum total point motion (MTPM) of the tibial implant component. There were, however, significant correlations between the medial region under the tibial tray density and the distal (r2 = 0.341, P = 0.003) and anterior (r2 = 0.230, P = 0.018) translation of the implant; and between the region under the tip of the implant and lateral translation (r2 = 0.176, P = 0.042).
Conclusion
These results support that a portion of the variability in post-operative implant migration can be attributed to the quality of the subchondral bone, which has important implications for post-operative treatment strategies to remove implant micromotion and prevent aseptic loosening.
