Development of a Pneumatic Tensioning Device for Gap Measurement during Total Knee Arthroplasty

The goal of total knee arthroplasty (TKA) is to achieve a well-aligned tibiofemoral and patellofemoral joint surrounded by a well-balanced soft-tissue envelope.[1][2][3] Soft tissue balancing in TKA should create a symmetric medial and lateral joint gap throughout the range of motion.4) Tight gaps may lead to limited motion, a less than satisfactory result, or adverse wear of the polyethylene component.5) Knee instability has been documented as a cause of pain and poor results after cruciate-retaining or posterior-Background: Despite the importance of soft tissue balancing during total knee arthroplasty (TKA), all estimating techniques are dependent on a surgeon's manual distraction force or subjective feeling based on experience.We developed a new device for dynamic gap balancing, which can offer constant load to the gap between the femur and tibia, using pneumatic pressure during range of motion.Methods: To determine the amount of distraction force for the new device, 3 experienced surgeons' manual distraction force was measured using a conventional spreader.A new device called the consistent load pneumatic tensor was developed on the basis of the biomechanical tests.Reliability testing for the new device was performed using 5 cadaveric knees by the same surgeons.Intraclass correlation coefficients (ICCs) were calculated.Results: The distraction force applied to the new pneumatic tensioning device was determined to be 150 N. The interobserver reliability was very good for the newly tested spreader device with ICCs between 0.828 and 0.881. Conclusions:The new pneumatic tensioning device can enable us to properly evaluate the soft tissue balance throughout the range of motion during TKA with acceptable reproducibility.