Which one restores in vivo knee kinematics effectively-medial or lateral pivot?

Abstract

Introduction: Total knee arthroplasty (TKA) usually provides good pain relief and improved function but has generally been unable to fully restore normal knee kinematics. Does Medial or Lateral Pivot TKA designs guide us to native knee kinematics needs to be elucidated?

Methods: Kinematic assessment of 13 knees with Medial Pivot TKA and 13 knees with Lateral Pivot TKA was done. The subjects were asked to perform step-up and weight bearing deep knee bend exercise under fluoroscopy for kinematic assessment. Patellar Tendon Angle (PTA) was measured after correcting f luoroscopic images for distortion against Knee Flexion Angle (KFA).

Results: During the weight bearing deep knee bend, the average active maximum flexion achieved with Medial Pivot design was 113.8 ͦ as compared to 102.9 ͦ with Lateral Pivot design. There was no significant difference in PTA in step up and deep knee bend exercise between both the designs.

Conclusion: The kinematic assessment of both the Medial and Lateral Pivot TKA designs revealed linear trend of PTA with increasing KFA as described for normal knee. Both the designs were able to achieve functional knee range of motion.

Keywords: Constraint; Kinematics; Lateral pivot; Medial pivot.

Fig. 1

PTA values of MP and LP Prosthesis with increasing KFA.

Fig. 2

PTA/KFA graph between MP and LP Prosthesis showing linear trend.

Fig. 3

a & b: PTA and KFA in Knee flexion and Knee extension.