Rotational Alignment of the Distal Femur Measured Using Magnetic Resonance Image in Korean Population and Its...

This study aimed to obtain accurate axes for rotational alignment of the distal femur using magnetic resonance imaging (MRI) and evaluate their correlation with X-ray measurements.

A total of 160 participants were included in the osteoarthritis (OA) group, and 160 were included in control group. The participants were placed in the supine position with fully extended knee joints and the patella facing forward for MRI examination. A series of axial MRI images of the distal femur overlapped using an imaging program to achieve more accurate rotational alignment of the distal femur. Rotational angles of the distal femur were measured along the posterior condylar axis (PCA), transepicondylar axis (TEA) and anteroposterior (AP) axis. Teleradiographs and weight-bearing anteroposterior radiographs of the entire lower extremity were obtained in the standing position for all participants. The hip-knee-ankle (H-K-A) angle measured on teleradiographs and the X-ray TEA-PCA angle measured in the Rosenberg view were compared with the rotational angle measured on MRI images.

The AP-TEA and AP-PCA angles in the OA group were more externally rotated than those in the control groups. The TEA-PCA angle was significantly greater in the OA group than in the control group. Increased H-K-A was negatively correlated with the AP-TEA and AP-PCA angles and positively correlated with the TEA-PCA angle. The increased radiographic TEA-PCA angle was negatively correlated with the AP-TEA angle and positively correlated with the TEA-PCA angle. These results may help surgeons to determine the rotational alignment of femoral implants for successful TKA.

When determining the rotational alignment of the distal femur in TKA, the differences in rotational alignment according to the patient must be considered. Moreover, even in the absence of a preoperative axial MRI, the TEA-PCA angle can be measured indirectly using the X-ray TEA-PCA angle in the Rosenberg view.