Objective: The aim of our study was to determine how consistent measurements of the distal femoral condyle on 16-MDCT are with intraoperative measurements and the reliability of 16-MDCT for the preoperative planning of total knee arthroplasty.
Materials and methods: Between August 2003 and March 2004, 33 consecutive patients (two men and 31 women; age range, 53-89 years; mean age, 71 years) presenting with osteoarthritis underwent 16-MDCT (Mx 8000 IDT) of a total of 53 knees before total knee arthroplasty. The prospective analysis included measurements of transepicondylar distance, maximum anteroposterior dimension of medial and lateral femoral condyles, and trochlear width on a Rapidia workstation. To increase reliability, we repeated the measurements on a CT workstation after 2 months and compared them with the previous values. The values measured on the CT workstation were compared with the measurements obtained in the intraoperative field. Statistical analysis was performed using kappa statistics. A p value of less than 0.05 was considered statistically significant.
Results: The mean values of transepicondylar distance, maximum anteroposterior dimension of medial and lateral femoral condyles, and trochlear width were 75, 57, 58, and 38 mm at first measurement; 76, 58, 59, and 39 mm at second measurement on the CT workstation; and 79, 57, 60, and 42 mm at intraoperative measurement, respectively. At reliability analysis between the first measurements on the CT workstation and the intraoperative measurements, kappa values were 0.84 for the transepicondylar distance, 0.81 for the maximum anteroposterior dimension of the medial femoral condyle, 0.89 for the maximum anteroposterior dimension of the lateral femoral condyle, and 0.62 for the trochlear width. The kappa values for the second measurements were 0.86, 0.77, 0.84, and 0.61, respectively. Intraoperative measurements and measured values on the CT workstation showed excellent and almost perfect agreement, and intraobserver agreement was almost perfect.
Conclusion: Femoral sizing on a CT workstation had excellent or almost perfect correlation with intraoperative measurements. Therefore, reliable preoperative planning for total knee arthroplasty may be done with 16-MDCT and an advanced workstation.