A radiological analysis of the difference between MRI- and CT-based patient-specific matched guides for total knee arthroplasty from the same manufacturer

Aims

This prospective randomised controlled trial was designed to evaluate the outcome of both the MRI- and CT-based patient-specific matched guides (PSG) from the same manufacturer.

Patients and Methods

A total of 137 knees in 137 patients (50 men, 87 women) were included, 67 in the MRI- and 70 in the CT-based PSG group. Their mean age was 68.4 years (47.0 to 88.9). Outcome was expressed as the biomechanical limb alignment (centre hip-knee-ankle: HKA-axis) achieved post-operatively, the position of the individual components within 3° of the pre-operatively planned alignment, correct planned implant size and operative data (e.g. operating time and blood loss).

Results

The patient demographics (e.g. age, body mass index), correct planned implant size and operative data were not significantly different between the two groups. The proportion of outliers in the coronal and sagittal plane ranged from 0% to 21% in both groups. Only the number of outliers for the posterior slope of the tibial component showed a significant difference (p = 0.004) with more outliers in the CT group (n = 9, 13%) than in the MRI group (0%).

Conclusion

The post-operative HKA-axis was comparable in the MRI- and CT-based PSGs, but there were significantly more outliers for the posterior slope in the CT-based PSGs.

Take home message: Alignment with MRI-based PSG is at least as good as, if not better, than that of the CT-based PSG, and is the preferred imaging modality when performing TKA with use of PSG.