Periprosthetic bone remodelling after total knee arthroplasty: early assessment by dual energy X-ray absorptiometry

The present investigation aims to evaluate periprosthetic bone remodelling after total knee arthroplasty by the use of dual-energy X-ray absorptiometr y (DXA). Twelve patients affected by osteoarthrosis of the knee joint under went primary total knee arthroplasty at an average age of 70.5 years. None of them had received a knee prosthesis before on the contralateral side. An teroposterior and lateral DXA measurements of the femur, tibia and total kn ee (both sides) were taken 2 weeks, 3 and 9 months postoperatively. The 2-w eek measurement was used as an individual reference value to be compared wi th the 3- and 9-month findings. In addition, the contralateral knee was inv estigated also in order to estimate how far bone mineral loss was due to im plantation or to an individual decline in bone mineral density (BMD). The c omparison of BMD values after knee arthroplasty revealed a conspicuous decr ease of bone density within 9 months. Bone mineral loss amounted to an aver age of 9.2% in anteroposterior and 17.8% in lateral DXA measurements. Later al femur shots showed an average decrease of density of even 21.5%. In cont rast, the BMD values of the contralateral knees remained almost unchanged. DXA. especially lateral shots of the femur, promises to be a suitable metho d for early assessment of periprosthetic bone remodelling after total knee arthroplasty.