Ankle Biomechanics during Pregnancy using Markerless Motion Capture

Research Type: Level 2 - Prospective comparative study, Meta-analysis of Level 2 studies or Level 1 studies with inconsistent results Introduction/Purpose: Pregnancy causes many physiologic changes, including increased body mass, postural adjustment, and circulating hormones that may affect mobility and contribute to musculoskeletal pain and falls [1,2,3]. Ankle biomechanics during pregnancy is chronically understudied and high-throughput patient testing can be leveraged to identify early predictors of pregnancy related pain, disability, and fall risk through studying the ankle joint. Markerless motion capture is a new technique that allows for participants to wear street clothes and avoid marker placement [4]. The overall goal of this study was to use markerless motion capture to compare ankle kinematics and kinetics of third trimester pregnant participants and nulligravida female control participants to identify compensatory ankle maneuvers during gait due to pregnancy. Methods: We recruited a cohort of third trimester pregnant participants (n = 37, gestational week = 35.4 ± 1.4 weeks, age = 33.4 ± 4.7 years) and a cohort of nulligravida female control participants (n = 19, age = 27.6 ± 3.5 years) with IRB approval and written informed consent. Participants performed six walking trials at their self-selected normal walking speed over a 6-meter distance. We used a high-definition 8-camera markerless motion capture system (Optitrack) to quantify gait biomechanics as we previously described [5]. Specifically, we used commercially available markerless motion capture (Theia 3D) and biomechanical analysis (Visual3D) software to compute lower extremity sagittal inverse kinematics and inverse dynamics for each gait cycle. We used a statistical parametric mapping two-sample t-test (Spmd1, α = 0.05) to evaluate ankle kinematics and kinetics. Results: Increased dorsiflexion in the third trimester pregnant cohort during the terminal swing phases of gait may be a potential maneuver to maintain a safe toe clearance and prepare for the following heel strike (Figure 1.). Also, increased ankle dorsiflexion during gait corresponds to results from the chronic ankle instability population in which increased dorsiflexion is a compensatory maneuver to increase stability in the ankle joint [6,7]. Heightened production of reproductive hormones and increased mass likely contribute to instability in the ankle joint, therefore causing these compensatory maneuvers to occur. Additionally, pregnant individuals experienced higher ankle plantarflexion moments during midstance, likely to support mass distribution and ankle instability while walking (Figure 1.). This adaptation may contribute to the high frequency of leg cramps during pregnancy [8,9]. Conclusion: We found significant differences in ankle biomechanics during walking in third trimester pregnant individuals. Using markerless motion capture allows us to increase our participant population by lowering the experimental burden imposed on this population, ultimately increasing our knowledge regarding compensatory gait strategies during pregnancy. This opens the door to initiate work on preventative treatments and specialized musculoskeletal care for pregnant individuals to improve pain and decrease falls. Figure 1 Nulligravida controls (green) and third trimester pregnant participants (blue) ankle angle (top) and ankle moment (bottom) during gait. *Grey shading represents statistically significant