Summary

TKA designed to restore normal position and normal motion may substitute the function of the anterior cruciate ligament with an implant shape.

Abstract

Background

Total knee arthroplasty (TKA) with an anatomical articular surface shape and physiologic sagittal geometry between the tibia and femur position was developed for purpose of acquisition of the normal knee function. However, it is unclear how the implant influences gait kinetics and muscle activation. Therefore, we evaluated the TKA prosthesis designed for normal knee function using three-dimensional gait analysis synchronized with surface electromyogram and compared the results with those of conventional TKA prosthesis.

Methods

We examined six osteoarthritis patients (>60 years old) who had undergone unilateral TKA more than 6 months ago. Three patients received a TKA prosthesis designed for normal knee function (J group), and the other three patients received conventional TKA prosthesis (L group). The subjects underwent three-dimensional motion capture analyses to acquire the kinematic and kinetic data of three trials of the 10-m walking test. Electromyography (EMG) data of 6 lower limb muscles were simultaneously collected during walking. The muscles of interest included vastus lateralis, vastus medialis, rectus femoris, semitendinosus, biceps femoris, and gluteus medius. We calculated the muscle activity ratio of the maximum voluntary contraction during walking maximal muscle contraction and compared the values between the groups. We compared the motion and EMG data between the groups.

Results

The maximal knee flexion angle during a gait cycle was 56.1±3.4 degrees in the L group and 61.8±3.9 degrees in the J group. The maximal hip flexion angle was 37.7±7.5 degrees in the L group and 21.7±4.9 degrees in the J group. Moreover, the J group showed double-knee action. The rectus femoris muscle activity was higher in the J group than in the L group.

Conclusion

A decreased knee flexion angle during walking and a decrease in double knee action are observed in patients with osteoarthritis and conventional TKA. We showed that walking properties are like normal gait in the J group. Moreover, the muscle activity of the quadriceps femoris muscle was higher in the J group than in the L group. These results indicate the possibility that a TKA designed to restore normal position and normal motion substitutes the function of the anterior cruciate ligament with an implant shape. Using the implant, the quadriceps femoris muscle is effectively exerted compared to the conventional TKA, which is an ACL-deficient knee.