How Can Surgeons Predict Kinematic Pivot Patterns?

Can surgeons predict intraoperative pivot patterns based on a measure of intraoperative tibiofemoral compartment contact force during total knee arthroplasty (TKA)? Yes, says a new study from the Indiana University School of Medicine and the Indiana University Health Physicians.

The research, “Tibiofemoral Contact Forces Influence Intraoperative Kinematic Pivot Pattern Dependent on Posterior Cruciate Ligament Resection in Primary Total Knee Arthroplasty,” appears in the April 2022 edition of the Journal of the American Academy of Orthopaedic Surgeons.

Study co-author Michael Meneghini, M.D., director of the Indiana University Hip and Knee Center explained to OTW the genesis of the study: “We have been studying kinematics in total knee arthroplasty for the past 6-7 years and have suspected that three things contribute to knee kinematic patterns: preoperative and native knee motions, alignment and component position, and finally, ligament balance. This study explored that one aspect…ligament balance as documented by compartment forces.”

Meneghini and his team collected data from 157 TKAs and used sensor-embedded tibial trials to measure intraoperative medial and lateral compartment forces. The team also used the associated condylar contact points to calculate kinematic pivot patterns between preceding flexion angles.

“Our hypothesis,” explained Dr. Meneghini to OTW, “was that a compartment, either medial or lateral, with higher forces would minimize the motion/translation of the femoral condyle on the tibia and therefore, impart a particular kinematic pattern. Our data supported the hypothesis. We were a bit surprised that in early flexion, compartment forces did not correlate with a pivot pattern.”

“Our most important results were that having a knee with greater force on the medial side of the knee in flexion (i.e., tighter on the medial side than the lateral side) will have a greater probability of enacting a beneficial medial pivot pattern in flexion. Ironically, this is the pattern that the majority of implant manufacturers are hoping to accomplish through their tibial polyethylene bearing topographies…so called, ‘medial pivot,’ ‘medial congruent,’ etc.”

Reaching Forward to Make a Dent In the 20% Unsatisfied Patient Population

“As we employ advanced technology such as robotics, augmented reality, and others, we MUST have our alignment and balance targets clearly identified, which we currently do not. Our study is a step toward the ultimate goal of performing a TKA for a patient that feels like their own knee…and gives the surgeon the ligament balancing target to facilitate that.”