Preoperative CT Assisted Planning for Primary Total Knee Arthroplasty

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.