Abstract
Introduction
Bicruciate-retaining (BiCR) total knee replacements (TKRs) were designed to improve implant performance; however, functional advantages during daily activity have yet to be demonstrated. Although level walking is a common way to analyze functionality, it has been shown to be a weak test for identifying gait abnormalities related to ACL pathologies. The goal of this study is to set up a functional motion analysis test that will examine the effects of the ACL in TKR patients by comparing knee kinematics, kinetics, and muscle activation patterns during level and downhill walking for patients with posterior-cruciate retaining (PCR) and BiCR TKRs.
Methods
Motion and electromyography (EMG) data were collected simultaneously for 12 subjects (4/8 m/f, 64±11 years, 31.3±7.3 BMI, 6/6 right/left) with BiCR TKRs and 15 subjects (6/9 m/f, 67±7 years, 30.5±5.1 BMI, 4/11 right/left) with PCR TKRs during level and downhill walking using the point cluster marker set. Surface electrodes were placed on the vastus medialis obliquus (VMO), rectus femoris (RF), biceps femoris (BF), and semitendinosus (ST) muscles. EMG data are reported as percent relative voluntary contraction (%RVC), normalizing the signal during downhill walking to the mean maximum EMG value during level walking.
Results
For level walking, there were no significant differences between groups in knee kinematics, kinetics, and EMG patterns. During downhill walking, subjects with BiCR implants showed significantly lower peak muscle activity in the VMO (73.9 ± 49.1%RVC for BiCR vs. 113 ± 24.0%RVC for PCR; p=0.045) and RF (96.0 ± 25.7%RVC for BiCR vs. 128 ± 28.6%RVC for PCR; p=0.018). There was also a trending higher knee peak flexion moment for the BiCR subjects (2.0 ± 0.6% BW*HT vs. 1.5 ± 0.6% BW*HT, p = .076), as well as significantly more knee flexion at heel strike (5.1 ± 4.7 degrees vs. 1.8 ± 2.8 degrees, p = 0.044) compared with the PCR group.
Discussion
Retention of the ACL led to altered muscle recruitment during downhill walking in BiCR subjects compared with PCR subjects. In BiCR subjects, quadriceps activity was reduced during downhill walking compared to level walking. PCR subjects on average did not show this reduction, possibly in compensation for decreased knee stability. While there were only a few significant kinematic/kinetic differences, it appears that BiCR TKRs may offer some neuromuscular benefits during more strenuous tasks like downhill walking. In conclusion, level and downhill walking knee kinematics and kinetics together with the corresponding quadriceps and hamstrings EMG signals begin to build an overall picture of implant functionality during motion analysis testing.
