CT-based and CT-free navigation in total knee arthroplasty - A prospective comparative study with respects to clinical and radiological results

Aim: Optimal component position in all planes and well-balanced soft tissues are factors for clinical outcome and survival time after total knee arthroplasty (TKA). With regard to clinical and radiological parameters, a comparative study between CT-based and CT-free navigation techniques was performed. Method: In this prospective study 44 patients (44 surgeries) were enrolled. One half of the surgeries were performed using a CT-based navigation system (group A), the other half using a CT-free system (group B). Pre-operatively and three months post-operatively the patients were physically examined (Insall score, step test, anterior knee pain, subjective feeling of instability and patient satisfaction) and limb alignment was measured by radiographs (mechanical axis, tibial slope, lateral distal femur angle [LDFA], medial proximal tibia angle [MPTA]). The tolerable inaccuracy range for all radiological measurements was +/- 3. Results: The radiological measurements showed a high accuracy but no significant differences (patients within tolerable range group A/B: mechanical axis 85.7/81.0%, tibial slope 95.2/90.5%, LDFA 100/95.2%, MPTA 90.5/95.2%). For physical parameters we found a better ligament balancing in group B. Conclusion: The CT-based module has an optimal planning procedure but costs more. The CT-free system provides equal radiological results and the availability of a useful ligament balancing module.