2015 ISAKOS Biennial Congress ePoster #1010

Does Axial Rotation of the Tibia Require a Systematic Correction When a Total Knee Arthroplasty is Planned with an MRI?

Derrick Sean Ross, BS in Mechanical Engineering, Davis, CA UNITED STATES
Alexander J. Nedopil, MD, Lodi, CA UNITED STATES
Stephen M. Howell, MD, Sacramento, CA UNITED STATES
Maury L. Hull, PhD, Davis, CA UNITED STATES
University of California, Davis, Davis, California, USA

FDA Status Not Applicable

Summary: There is no justification for a systematic correction of the I-E rotation of the tibia on the femur in TKA planned with non-weight bearing MRI images.

Abstract:

Background

Correction of varus, valgus, and flexion rotational deformities of the knee is an accepted practice when performing a total knee arthroplasty (TKA). It is unclear whether the internal or external (I-E) rotation of the tibia on the femur as measured by the angle between a tibial and femoral reference line is different between the normal and osteoarthritic (OA) knee with an intact or torn anterior cruciate ligament (ACL).

Methods

Two methods determined the I-E rotation of the tibia on the femur (- internal, + external) with use of magnetic resonance image (MRI) scans obtained from 75 patients with a normal knee, 75 patients with OA and an intact ACL, and 75 patients with OA and a torn ACL. Method 1 measured the angle between a line connecting the medial border of the tibial tubercle and the center of the posterior cruciate ligament and a line perpendicular to the posterior condylar axis of the femur (- internal, + external rotation). Method 2 measured the angle between the posterior condylar axis of the tibia and the posterior condylar axis of the femur.

Results

For methods 1 (and 2), the mean ± standard deviation of I-E rotation of the tibia on the femur was 1° ± 5° (-4° ± 5°) for the normal knee, -1° ± 5° (-3° ± 4°) for the knee with OA and an intact ACL, and -2° ± 5° (-2° ± 5°) for the knee with OA and a torn ACL. The intraclass correlation coefficients of 0.94 (and 0.81) indicated high reproducibility.

Conclusion

These results suggest there is not a systematic malrotation of the tibia on the femur in the osteoarthritic knee with an intact ACL or torn ACL, therefore a systematic correction of I-E rotation is not required when performing total knee arthroplasty.