Do manual cutting guides for total knee arthroplasty introduce systematic error?

INTRODUCTION: Conventional cutting guides in total knee arthroplasty can potentially cause unintentional deviation from the planned direction and depth of bone resection resulting in malaligned components. The purpose of this study was therefore to investigate the accuracy of bone cutting jigs for both the femur and tibia using imageless navigation.
MATERIAL AND METHODS: A total of 125 patients with a mean age of 66.7 ± 9.9 years underwent primary total knee arthroplasty with a Stryker Triathlon™ fixed bearing posterior cruciate retaining implant using imageless navigation. Coronal and sagittal position of the secured cutting jig was recorded and bone resection was checked with a rectangular probe attached to a navigation tracker.
RESULTS: There were significant within group differences for the femoral sagittal cut (mean δ = 0.9° [31 %]; p = 0.00001), femoral depth medial compartment (mean δ = 0.5 mm [5 %]; p = 0.001), femoral depth lateral compartment (mean δ = 0.7 mm [7 %]; p = 0.00001), proximal tibial cut (mean δ = 0.3 mm [25 %]; p = 0.001), tibial depth medial compartment (mean δ = 0.6 mm [10 %]; p = 0.0001) and tibia depth lateral cut (mean δ = 0.4 mm [5 %]; p = 0.002). Deviation of more than 2° was observed for the distal cut in the sagittal plane in 17 % and in 9.6 % for the proximal tibial cut in the sagittal plane of all patients.
CONCLUSION: The results of this study demonstrated significant differences between the dialed in cut and "actual" bone resection achieved for all planes for both the femur and tibia. The femur sagittal cut demonstrated a tendency for an extended cut and the tibia showed a tendency for varus.