Abstract
Background
Finding the anatomical landmarks used for correct femoral rotational alignment can be difficult. The Posterior Condylar Line (PCL) is probably the easiest to find during surgery. The aim of this study was to analyze if a predetermined fixed angle referencing of the PCL could help obtain good femoral alignment in TKA patients.
Methods
2637 CT scans used for preoperative planning and creation of patient-specific instrumentation (PSI) were used to analyze the Posterior Condylar Angle (PCA) between the Surgical Epicondylar Axis (SEA) and the PCL.
Results
The mean PCA was 3.99° +/− 1.35° of external rotation. A significant relation was found between more external rotation and more varus of the tibia and more valgus of the femur. In 132 patients bilateral CT's were available and 94 (71%) had rotation within 1° of the opposite side. 96% of patients would receive the right amount of external rotation with 6°. On 105 (4%) CT's external rotation between 7° to 11° was measured and 77 (73%) of those were in varus or neutral alignment.
Conclusions
After substracting a correction of 1° for cartilage remnants, a posterior condylar angle of 5° external rotation is proposed which should cover 96% of the population. For 4% of patients, both varus and valgus knees, 5° of external rotation will not be sufficient. The epicondylar axis should be explored during surgery, determined with patient-specific instruments, or a balancer should be used for this group.
