Abstract
Purpose
When we perform total knee arthroplasty (TKA), the accurate osteotomy and implant setting is important as follows to improve long-term results. As means to perform osteotomy exactly, patient specific surgical instruments (PSI) patient specific surgical instruments planning based on pre-operative MRI (Signature, Materialise) and Image-free navigation system (Navi: Knee unlimited; BrainLAB) exist. However, there is not the report to compare which is exact for the same patient at the same time using two methods. We report to compare the osteotomy plans by two methods.
Materials
Nine cases of TKA (Vanguard Complete Knee System, PS, BIOMET) operated on by one operator in our hospital from October 2012 to September 2013. 78.0 years average age (71–81 years old), sex was 6 cases women, 3 men.
Methods
Intra-operatively measurements of α, β, γ, δ angle, rotation angle of the femoral component and the size of the components were evaluated between the two groups. Coronal cutting angles were considered as outlier the difference between the 3 ° or more from the preoperative planning on computed tomography (CT) scans made one week after surgery.
Results
PSI cases were inclined with respect to Navi cases, coronal plane: average varus 0.4 ° (valgus 1.0° to varus 3.0°), sagittal plane: flexion 1.0° (flexion 5.0° to extension 3.5°), axial plane: internal rotation 0.9° (internal rotation 3.5° to external rotation 0.0°) in the femur. Coronal plane: average valgus 0.5 ° (valgus 1.5° to varus 4.5°), sagittal plane: backward tilt 0.9° (forward tilt 3.0° to backward tilt 4.5°) in the tibia. Three cases of femoral implant were different from PSI plan, 5 cases in tibia. One of PSI cases in the femur and 1 case in tibia is outlier.
Discussion
In the femoral side, fitting of the PSI was good, and error is less. However, in the tibia, some cases of fitting were bad and large error. These PSI were not stable on the bone and looks like seesaw motion at the tibial side. It is necessary to final confirmation by using the extramedullary guide in PSI cases.
Conclusion
Accuracy of Navi was higher than PSI in our study.
