DISCREPANCY BETWEEN CT- AND MRI-BASED PATIENT-SPECIFIC MATCHED GUIDES FOR TOTAL KNEE ARTHROPLASTY FROM THE SAME MANUFACTURER

Abstract

A comparative study on CT- and MRI-based patient specific matched guides (PSG) from the same manufacturer for the implantation of total knee arthroplasty (TKA) has not been undertaken.

A total of 64 knees operated with CT based PSG was divided into two groups, with (n=32, CT^HK) or without (n=32, CT^NA) a history of a knee operation, and matched with a control group operated with MRI based PSG(n=64). Alignment of the biomechanical axis of the leg (HKA angle) and accuracy of individual implant alignment were measured on digital long-standing AP and sagittal radiographs. HKA and implant angles <3° deviation of the preoperative planned alignment were defined as correct. Peroperative implant size, OR time (min) and blood loss (ml) were compared.

The average HKA angle in the CT^HK group (177.0, 170.5 to 181.5, p=0.016) and mean varus-valgus alignment of the tibia component in the MRI group (90.6, 85.6 to 94.1, p=0.003) were statistically significant different. None of the outcome on the frontal femoral and lateral tibial component were statistically significant different. Percentage <3° deviation of the preoperative planned femoral flexion-extension alignment was better in the MRI group (84%, p=0.002), compared to the CT^HK and CT^NA group (respectively 30% and 42%). Average operation time was statistically significant shorter in favour of the MRI group (53.1, 34 to 80, p≤0.00), compared to the CT^HK(70.8, 44 to 114) and CT^NA group (59.2, 41 to 78).

There is discrepancy between CT and MRI based PSG from the same manufacture because of patients who were not suitable for MRI due to history of a knee operation in the past. Whether these differences are clinically relevant is questionable. Future research needs to emphasise whether one of these two modalities, MRI or CT is superior compared to the other.