Preoperative planning of total knee arthroplasty: reliability of axial alignment using a three-dimensional planning approach

Background Preoperative templating of total knee arthroplasty (TKA) can nowadays be performed three-dimensionally with software solutions using computed tomography (CT) datasets. Currently there is no consensus concerning the axial orientation of TKA components in three-dimensional (3D) planning. Purpose To assess intra-/inter-observer reliability of detection of different bony landmarks in planning axial component alignment using axial CT images and 3D reconstructions. Material and Methods Intra- and inter-observer reliability of determination of four predefined axial femoral and tibial axes was calculated using data from CT scans. Axes determination was performed on the axial slices and on the 3D reconstruction using preoperative planning software. In summary, 61 datasets were analyzed by one medical student (intra-observer reliability) and 15 datasets were analyzed by four different observers independently (inter-observer reliability). Results For the femur, clinical epicondylar axis and posterior condylar axis showed the best reliability with an inter-observer variability of 0.7° and 0.5°, respectively. For the tibia, posterior condylar axis provided best reliability (inter-observer variability: 1.7°). Overall variability was greater for tibial than for femoral axes. Reliability of axis determination was more accurate using axial CT slices rather than 3D reconstructions. Conclusion The femoral clinical epicondylar axis is highly reliable. Landmarks for the tibia are not as easily identifiable as for the femur. The tibial posterior condylar axis presents the axis with highest reliability. Based on these results, clinical epicondylar axis for orientation of the femoral TKA component and posterior condylar axis for the tibial implant, both defined on axial slices can be recommended.

Incidence of Femoral Component Malrotation Using Posterior Condylar Referencing in Total Knee Arthroplasty

Proper femoral component rotation in total knee arthroplasty (TKA) is important, given the prognostic impact of a poorly positioned component. The purpose of this observational study was to determine the incidence of femoral component malrotation using posterior condylar axis (PCA) referencing. A total of 100 knees in 92 patients with varus gonarthritis of the knee undergoing primary TKA using a standard medial parapatellar approach were evaluated intraoperatively. After distal femoral resection, the standard femoral sizing guide referencing the posterior condylar axis was used to set femoral component rotation. This was then compared with both the transepicondylar (TEA) and trochlear anteroposterior axes (TRAx). Disparites were recorded and corrected in line with the epicondylar axis. Rotational adjustment for addition of further external rotation was made in 13 (13.0%) cases. In seven cases, the medial pin sites were raised between 1 and 3 mm, and in six cases, the lateral pin site was lowered between 1 and 3 mm (based on risk of notching the femoral cortex). It is critical to not rely exclusively on the PCA to confirm rotational positioning of the femoral component as predicted by posterior condylar referencing guides. Intraoperative adjustment and confirmation using the TEA and TRAx occurred in 13% of primary TKA cases, which might have, otherwise, had a significant effect on the clinical outcome.

Consistency Between Posterior Condylar Axis (+3˚ external rotation) Line and Clinical Transepicondylar Axis Line in Primary Total Knee Arthroplasty

Objectives: Purpose of this study is to as certain consistency between posterior condylar axis (PCA) + 3˚ external rotation line and clinical transepicondylar axis (cTEA) line in primary total knee arthroplasty cases. Materials-Methods: During surgery, following distal femoral cut PCA +3 degree external rotation line and cTEA line drawn on the distal femoral cutting surface by ruler and pencil. The both lines on distal femur were recorded by digital camera and relationship between lines was ascertained in reference to PCA +3 degree external rotation [parallel (P), Internal rotation (IR) and External Rotation (ER)]. Results: 9 knees of 9 patients [1 men, 8 women; average age 67 (59-80 age)] were constituted the study group. Evaluation results of the photographs revealed that clinical TEA line in comparison PCA +3 degrees external rotation line was ER in 9 knees (100%) whose mean angles 2.7˚ (1-6) and detected external roation with mean angle 4.7˚ (2-7) in 9 knees. Conclusion:: For determination of FC rotation in surgery setting, different results between cTEA and PCA + 3 degrees techniques possibly may due to disadvantages of techniques and anatomic variation of distal femur. Thus, using both techniques for check each other’s results seems unsafe. In custom made prosthesis, which can be done in the future it will be measured by CT. Keywords: Total knee arthroplasty, femoral component, rotational alignment, femoral transepicondylar axis, posterior condylar axis

Distal Femoral Rotational Axes in Indian Knees

Purpose. To measure the angular relationships of distal femoral rotational axes in 100 normal Indian knees. Methods. 42 men and 8 women aged 26 to 40 (mean, 31) years, with 100 normal non-arthritic knees were recruited. Anatomic landmarks were measured using computed tomography. They included the posterior condylar axis, the transepicondylar axis, the anteroposterior axis (Whiteside's line), the posterior condylar angle (PCA), the Whiteside-epicondylar angle (W-EP), and the Whiteside-posterior condylar angle (W-PC). Results. The mean PCA, W-EP, and W-PC were 5°, 90.8°, and 95.8°, respectively. The mean femorotibial alignment was 179.6°. The differences between the left and right sides were significant only for the W-EP and W-PC. Only the PCA and W-EP were weakly correlated ( r=0.338, p=0.001). Conclusion. There are differences in distal femoral rotational axes among Indian, Caucasian, and Japanese knees. Our data can be used to evaluate changes in those axes in ageing or arthritic patients.