Total knee arthroplasty is one of the most common management methods of knee osteoarthritis. Patellar complications are one of the important causes of revision total knee arthroplasty. Proper placement of the components in the best rotational and axial alignment would achieve better patellar tracking and the best functional outcomes. Preoperative CT scan can add information regarding the coronal and rotational alignment of the prosthesis components.

Total knee arthroplasty is the gold standard treatment for advanced knee osteoarthritis. In spite of the great advance in the prosthesis design, surgical techniques and rehabilitation programs, only 85% (75% to 92%) of patients with total knee arthroplasty are satisfied with their operations and 30% develops patellofemoral complications.

Femoral and tibial components malrotation is a crucial cause of postoperative knee pain, patellar instability, and may lead to revision. In measured resection technique the surgical epicondylar axis (SEA) is the center of rotation of the knee and the femoral component must be parallel to this axis. The surgical epicondylar axis is difficult to be determined intraoperative by palpation.

Commonly, surgeons routinely set the femoral posterior condyle resection at three degrees fixed from the posterior condylar line (PCL) because the PCL was found to be three degrees internally rotated from the (SEA).

The posterior condylar angle on a three-dimensional structure reconstruction of the CT scans in osteoarthritic knees has also been shown as 3.3° ± 1.5°, However, another study documented the posterior condylar angle (PCA) in osteoarthritic knees as 1.6° ± 1.9°. Also there is a two to three degree difference between the surgical epicondylar axis and the anatomical epicondylar axis. Therefore, a routine bone resection of three degrees from the PCL is not universal for all cases and may create malrotation of the femur.

CT scan can provide an adequate template with good but not excellent inter and intra observer reliability for exact determination of the surgical epicondylar axis and femoral component rotation.

2. AIM/ OBJECTIVES

1. What is the mean of distal femoral rotation in Egyptian population?
2. What is the effect of osteoarthritis on femoral rotation?
3. How much is the accuracy of CT scan in detecting anatomical landmarks to choose the intraoperative femoral component rotation (correlation between radiological and intraoperative findings?
4. Is the relation between the anatomical epicondylar axis (AEA) in comparison to surgical epicondylar axis (SEA) a fixed ratio?
5. What is the relation between thde femoral component malrotation and the coronal alignment and flexion gap balance?
6. Can CT scan add a simple planning tool for accurate placement of femoral component and the reproducibility of the preoperative plan in surgery?

Inclusion Criteria:

• Advanced knee osteoarthritis in which total knee arthroplasty is indicated

Exclusion Criteria:

• Revision total knee arthroplasty