The Effect of Body Mass Index on the Biomechanics Before and After Total Knee Arthroplasty

  • Author / Creator
    Wayne, Christopher A
  • Osteoarthritis (OA) is prevalent, commonly affecting weight-bearing joints, such as the knee. In Canada, approximately 40% of Canadians aged 50 to 64 are diagnosed with OA, of which 38% experience knee pain. When conservative treatments do not help those with end-stage knee OA, total knee arthroplasty (TKA) is an elective surgical option that can provide pain relief and improve knee function. Individuals living with obesity (Body Mass Index [BMI] > 30.0 kilogram/meter squared [kg/m2]) are at increased risk for developing knee OA compared to normal weight people, partly due to altered knee kinematics and kinetics. Approximately 7 million Canadians were living with obesity in the year 2013. Quantitative gait analyses via three-dimensional (3D) motion capture have shown that individuals living with obesity or OA have altered knee kinematics and kinetics compared to those of normal weight or those without OA. However, there is a paucity of research on the effect of obesity and OA on knee biomechanics after TKA, particularly in individuals living with Class II obesity (BMI 35.0-39.99 kg/m2). Understanding the impact of BMI on knee kinematics and kinetics after TKA may inform surgical and rehabilitation protocols to improve individual outcomes. The purpose of this prospective matched series was to evaluate the impact of obesity on time series and parameters of kinematics (angles of flexion-extension, abduction-adduction, internal-external rotation) and external kinetics (non-normalized and normalized moments to body weight of flexion-extension, abduction-adduction), and spatio-temporal parameters (velocity, cadence, stride length) at pre-TKA, post-TKA, and change from pre-to-post TKA, in 20 adults aged 50 to 70 years. Comparisons were made between 5 females/5 males with class II obesity (OB group) and 10 age- and sex-matched normal/overweight adults (BMI 18.5-29.9 kg/m2 [N/OW group]) using 3D motion capture on level ground. Participants received a 3D gait assessment within one-month before and 12-weeks after TKA. Optoelectronic motion capture and synchronized floor-embedded force platforms collected motion and forces during 10-meter walking at a self-selected speed. A hybrid biomechanical model was created, with inertial properties of body segments estimated via the participant’s body height and weight. The data were first screened and interpolated using Eva Real-Time Software and then processed using Visual3D. To evaluate group differences in kinematic, kinetic and spatio-temporal parameters at pre- and post-TKA, a Wilcoxon rank-sum test was used to compare group medians and interquartile ranges. To evaluate changes over time from pre- to post-TKA between groups in kinematic, kinetic and spatio-temporal parameters, a two-way repeated measures analysis of variance was performed.The mean BMI for the OB group was 37.1 kg/m2 (standard deviation [SD] 1.79), and 27.0 kg/m2 (SD 2.15) for the N/OW group (p=0.0005, 95%CI [29.4, 34.8]). Both groups were age and sex matched, with the OB group having mean age of 64.2 years (SD 6.04) with 5 females and 5 males, and the N/OW group having a mean age of 66.8 years (SD 2.86) with 5 females and 5 males. Twenty participants completed the preoperative gait assessment, with 17 (85%) participants (8OB, 9N/OW) completing post-TKA assessment.At pre-TKA, the OB group had greater maximum flexion angle during swing phase (p=0.05) and greater non-normalized extension moment during swing phase (p=0.03) compared to the N/OW group. At post-TKA, the OB group had greater maximum adduction angle during stance (p<0.001), greater maximum non-normalized moment in adduction (p<0.001), greater minimum flexion non-normalized moment during stance phase (p=0.01), and greater maximum extension non-normalized moment during swing phase (p<0.001), compared to the N/OW group. From pre- to post-TKA, the OB group increased in adduction angle whereas the N/OW group decreased in adduction angle (p=0.02) and the OB group decreased in extension non-normalized moment whereas the N/OW group increased in extension non-normalized moment (p=0.02) during swing. The groups did not differ in any spatio-temporal parameters either pre- or post-TKA.While future work is warranted, this thesis contributes to the knowledge of the impact of obesity on the knee time series and parameters of kinematics and kinetics, and spatio-temporal parameters of level walking in adults undergoing TKA. Exploring this relationship can further our understanding of how these factors interact and may allow us to individualize rehabilitation approaches to address modifiable gait differences or to accommodate differing recovery trajectories to improve patient outcomes.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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