Low Preoperative BMD Is Related to High Migration of Tibia Components in Uncemented TKA-92 Patients in a Combined DEXA and RSA Study With 2-Year Follow-Up.

BACKGROUND: The fixation of uncemented tibia components in total knee arthroplasty may rely on the bone quality of the tibia; however, no previous studies have shown convincing objective proof of this. Component migration is relevant as it has been shown to predict aseptic loosening.

METHODS: We performed 2-year follow-up of 92 patients who underwent total knee arthroplasty surgery with an uncemented tibia component. Bone mineral density (BMD; g/cm2 ) of the tibia host bone was measured preoperatively using dual energy X-ray absorptiometry. The proximal tibia was divided into 2 regions of interest (ROI) in the part of the tibia bone where the components were implanted. Radiostereometric analysis was performed postoperatively and after 3, 6, 12, and 24 months. The primary outcome was maximum total point motion (MTPM; mm). Regression analysis was performed to evaluate the relation between preoperative BMD and MTPM.

RESULTS: We found low preoperative BMD in ROI1 to be significantly related to high MTPM at all follow-ups: after 3 months (R2  = 20%, PBMD  = 0.017), 6 months (R2  = 29%, PBMD  = 0.003), 12 months (R2  = 33%, PBMD  = 0.001), and 24 months (R2  = 27%, PBMD  = 0.001). We also found a significant relation for low BMD in ROI2 and high MTPM: 3 months (R2  = 19%, PBMD  = 0.042), 6 months (R2  = 28%, PBMD  = 0.04), 12 months (R2  = 32%, PBMD  = 0.004), and 24 months (R2  = 24%, PBMD  = 0.005).

CONCLUSION: Low preoperative BMD in the tibia is related to high MTPM. Thus, high migration of uncemented tibia components is to be expected in patients with poor bone quality.