Distal Femoral Rotational Alignment Based on Mechanical Axis of the Femur: A 3-Dimensional Computed Tomographic Scan in Vivo Assessment / 대한정형외과학회잡지

PURPOSE: To measure and to analyze the relationships among the rotational axes of the distal femoral region by means of 3-dimensional (3D) computed tomographic (CT) images taken perpendicularly to the mechanical axis and a 3D rendering program. MATERIALS AND METHODS: Fifty cases involving the lower extremity were included in this study, which used 3D computed tomographic angiograms. CT images of the perpendicular cross-sections to the mechanical axis of the femur were obtained by processing 3D recombinant images using Aquaris NET(R). The following anatomical angles were obtained from axial imaging using the 3D reconstructed bone model: transepicondylar axis, surgical transepicondylar axis, anteroposterior axis, and real posterior condylar axis. RESULTS: In the tomographic images, the angles to the real posterior condylar axis formed by the anatomical femoral transepicondylar axis, the anatomical femoral transepicondylar axis, and the anteroposterior axis were 6.34+/-1.23degrees, 2.43+/-1.56degrees, and 96.52+/-1.77degrees, respectively. The angles to the anatomical femoral transepicondylar axis formed by the anteroposterior axis and the surgical femoral transepicondylar axis were 90.19+/-1.61degrees and 3.91+/-0.90degrees, respectively. In the recombinant 3D femur model, the angles to the real posterior condylar axis formed by the anatomical femoral transepicondylar axis and the anteroposterior axis were 6.29+/-1.86degrees, and 93.33+/-3.76degrees, respectively. And, the angle for anteroposterior axis from anatomical transepicondylar axis was 87.04+/-4.11degrees. CONCLUSION: The method of measuring the rotational axes of the distal femur using the CT image taken perpendicularly to the mechanical axis is considered reproducible. In particular, the measurement method using the anatomical transepicondylar axis is more accurate than that using the anteroposterior axis.

Rotational Axes of the Femoral Componentin Total Knee Arthroplasty / 대한정형외과학회잡지

PURPOSE: The degree of external rotation produced by the gap technique in total knee arthroplasties (TKA) was measured and compared with other methods. MATERIALS AND METHODS: Thirty-nine TKA patients (52 cases) were enrolled in this study. The transepicondylar axis (TEA) and the perpendicular line to the anteroposterior axis (APA) were drawn on the images of the computerized tomographs (CT). After resecting the posterior condyles using the gap technique, the maximal depths of the resected fragments were measured, and the resected lines (RL) were drawn on the same CT images. The differences in the angles between the RLs and the TEAs, the perpendicular lines to the APAs, and the lines that were externally rotated 3o from the posterior condylar axes, were evaluated. RESULTS: The posterior condylar axes formed 5.1+/-2.5 degrees angles with the RLs, 5.3+/-1.6 degrees angles with the TEAs, and 4.5+/-2.1 degrees angles with the lines that were perpendicular to the APAs. The RLs showed similar TEAs, and the APAs (0.2+/-2.6 degrees and 0.6+/-3.0 degrees, respectively). However, the lines of 3 degrees external rotation (2.1+/-2.5 degrees) were significantly different. CONCLUSION: A more ideal flexion gap could be obtained with the TEAs compared with other methods. However, resections of the posterior condyles using the gap technique might be more effective than with the TEAs due to the individual variations and errors in obtaining symmetric flexion gaps with this value.

Rotational Axis in Total Knee Arthroplasty: Transepicondylar axis and Anteroposterior axis of Femur

PURPOSE: We compared the tansepicondylar axis and the anteroposterior axis used as the references for the rotational axis of the femur when performing total knee arthroplasty and determined effect of varus deformity on two axes. MATERIALS AND METHODS: This study was conducted in 49 patients (69 cases of knees) with osteoarthritis who underwent preoperative computerized tomography (CT). The control group included 53 patients having no arthritis (53 cases) who underwent preoperative MRI for meniscal injury. On CT and MRI images, angle between tansepicondylar axis and the posterior condylar axis (posterior epicondylar angle) and angle between anteroposterior axis and posterior condylar axis (anteroposterior angle) were measured. Then, the data of two groups were compared. RESULTS: The average posterior epicondylar angle in the knee osteoarthritis group was 5.4 degrees +/-1.8, whereas that in the control group was 5.9 degrees +/- 1.6. The average anteroposterior angle in the osteoarthritis group was 3.8 degrees +/-1.6, whereas it was 3.9 degrees +/- 1.5 in the control group showing a significant difference from westerners. There was significant difference between posterior epicondylar angle and anteroposterior angle. But, no significant difference was seen in posterior epicondylar angle and anteroposterior angle between two groups. CONCLUSION: According to this study, the transepicondylar axis showed an average external rotation of 5.4 degrees , which was larger than 3 degrees recommended in usual total knee arthroplasty. The anteroposterior axis showed an average external rotation of 3.8 degrees . Varus deformity due to osteoarthritis had no significant effect on two axes. When femoral component is inserted, using only one axis to obtain correct rotational alignment caused problems because of considerable individual differences of two axes and we should consider two axes for correct rotational alignment.

Measurement of the Axial Rotational Axis of Distal Femur Using Different Landmarks

PURPOSE: To know the discrepancy of rotational alignment using human femur. MATERIALS AND METHODS: We used 22 adult human femurs which were not able to distinguish age and sex and absent articular cartilage. In a horizontal plane, we made a cross-section perpendicularly at supra-condyle of femur to a mechanical axis and took a simple roentgenogram in coronal plane focusing on the center of transepicondylar axis. In terms of roentgenogram and gross specimen, the angle between per-pendicular to the anteroposterior axis and the posterior condylar axis, the angle between the transepi-condylar axis and the posterior condylar axis were measured by 5 observers. According to t-test in statisti-cal method, we figured out the difference between two angles and made a significance at p<0.05. RESULTS: About posterior condylar axis, the line perpendicular to anteroposterior axis was observed the average 4.8(+/-1.5)degree, 6.0(+/-1.9)degree external rotation in roentgenogram and gross specimen respectively. The transepicondylar axis was observed the average 3.5(+/-1.2)degree, 3.9(+/-1.4)degree external rotation in roentgenogram and gross specimen respectively. There was statistically significant difference between two angles. Moreover, angles measured by 5 observers were found that to have a line perpendicular to the anteroposterior axis has much more external rotation respectively and there was a statistically significant difference also. CONCLUSIONS: On determination of a rotational alignment using human femur, there is statistically sig-nificant difference between the anteroposterior axis and the transepicondylar axis in gross specimen as well as roentgenogram.

Radiographic measurement study of two reference axes for rotational alignment of the femoral component in total knee arthroplasty / 解放军医学杂志

0.05). Conclusion Compared with the Whiteside′s line, the transepicondylar axis seems to be more reliable to determine the rotational alignment of femoral component in total knee arthroplasty. The posterior femoral condylar angle of the Chinese people is larger than that of the Caucasians. If the widely used way of 3? lateral rotational orientation of the femoral component referring to the posterior condylar surfaces of the femur in total knee arthroplasty is adopted, it tends to produce internal malrotation of the femoral prosthesis after operation.