Assessment of implant position after total knee arthroplasty by dual-energy computed tomography

Background: Correct alignment of prosthetic components is the most important factor for the success of total knee arthroplasty (TKA). Dual-energy computed tomography (DECT) may be a reliable method in determining implant position after TKA. Purpose: To evaluate the accuracy and reproducibility of DECT in determining implant position after TKA. Material and Methods: Institutional review board approval was obtained. Forty-five patients (age 75.2=6.4 years) prospectively underwent TKA at our institution between May and December 2012. DECT was performed 1 year after surgery, using an alignment similar to a standing position and generating images at an extrapolated energy of 120 kVp, in order to reduce metal artifacts. Implant position was evaluated by two independent readers. Intra-and inter-observer agreements were calculated. DECT measurements on implant position were compared with the preoperative planning based on radiographs. Additional clinical and DECT findings were taken into account. Results: Metal artifact reduction was judged satisfactory in all cases. Regarding implant position assessed with DECT, good to excellent intra-observer (k: 0.74-0.87 and k: 0.75-0.88, respectively), and inter-observer agreement (k: 0.72-0.82) were found. In the comparison with preoperative planning, the widest limits of agreement were within 3.9 for the sagittal orientation of tibial component. A single patient with postoperative knee pain and stiffness had periprosthetic osteopenia, quadriceps femoris tendon calcifications, articular effusion, and excessive intrarotation of the femoral component. Conclusion: DECT is an accurate and reproducible tool for determining implant position after TKA.