Abstract
Introduction
Minimally invasive, computer navigated techniques are gaining popularity for total knee replacement (TKA). While these techniques may have the potential to provide improved functional outcomes with more rapid recovery, little quantitative data exists comparing long-term gait function following surgery with different exposure approaches. This study compares functional gait differences between surgical approach groups two year following TKA. Kinetics, kinematics, and temporospatial parameters were assessed to determine if differences exist between groups in long term follow-up.
Methods
This study was approved by the Banner IRB (Sun Health Panel). 95 subjects volunteered to participate in the study and signed informed consent prior to testing. The subjects were prospectively randomized to one of four surgical approach groups, mini-midvastus (MV), mini-subvastus (SV), mini-parapatellar (MP), and standard parapatellar (SP). These subjects were also compared to 45 age-matched, asymptomatic controls. Surgery was performed by one of two fellowship trained orthopedic surgeons specializing in adult reconstruction. Subjects were assessed in the gait laboratory two years after receiving surgery. Three dimensional kinetic and kinematic data were captured using a ten-camera passive marker system, a modified Helen Hayes marker set (Eagle-4, Motion Analysis, Santa Rosa, CA), and four floor embedded force platforms (AMTI Inc., Watertown, MA). Subjects were instructed to walk at a self selected speed down an 8 meter walkway. Kinetic and kinematic data were post processed using EVaRT and OrthoTrak 6.23 biomechanical software (Motion Analysis, Santa Rosa, CA). Statistical analyses were performed using SPSS (v14.0, SPSS Inc, Chicago, IL) and included a one-way ANOVA and post hoc testing.
Results
50 subjects returned for a two year gait analysis. Selected results are provided in Table 1. All approach groups regained near normal knee function compared to age matched controls. Motion analysis provided specific statistical differences between parameters about the knee and hip. The MV approach group maintained greater flexion than other groups at the knee and hip throughout the gait cycle. The MP group maintained the most extended knee postures throughout the task with significant differences from controls being noted during peak flexion in swing (p = 0.039) and at foot strike (p = 0.034). They also had reduced external knee rotation angles (p = 0.010) and a larger pelvic rotation range of motion (p = 0.020). Although not significant, the MP group had a concurrent increase in pelvic obliquity on the operative limb during weight acceptance. The MP group also had the highest velocity, cadence, stride length, and the earliest toe off when compared to other groups.
Discussion
The results indicate that there are subtle differences in gait strategy between approach groups at the two year time point. The MV group maintains increased flexion angles at the hip and knee throughout the gait cycle which could be characterized as a “bent-hip bent-knee” gait. This could be due to differences in capsular and muscle scarring between the different surgical approach groups. The MP approach group maintained more extended knee postures with improved velocity, cadence, and stride length. No differences in pain were detected in clinical scores.
