Complications of fixed infrared emitters in computer-assisted total knee arthroplasties

BACKGROUND The first stage in the implant of a total knee arthroplasty with computer-assisted surgery is to fasten the emitters to the femur and the tibia. These trackers must be hard-fixed to the bone. The objectives of our study are to evaluate the technical problems and complications of these tracker-pins, the necessary time to fix them to the bone and the possible advantages of a new femoral-fixed tracker-pin. METHODS Three hundred and sixty seven tracker-pins were used in one hundred and fifty one computer-assisted total knee replacements. A bicortical screw was used to fix the tracker to the tibia in all cases; in the femur, however, a bicortical tracker was used in 112 cases, while a new device (OrthoLock) with percutaneous fixation pins was employed in the remaining 39. RESULTS Technical problems related to the fixing of the trackers appeared in nine cases (2.5%). The mean surgery time to fix the tracker pin to the tibia was 3 minutes (range 2-7), and 5 minutes in the case of the femoral pin (range: 4-11), although with the new tool it was only three minutes (range 2-4) (p < 0.001). No complications were observed with this new device. CONCLUSION The incidence of problems and complications with the fixing systems used in knee navigation is very small. The use of a new device with percutaneous pins facilitates the fixing of femoral trackers and decreases the time needed to place them.