3D Kinematics

Does Corrective Surgery in Femoroacetabular Impingement Improve Joint Kinematics During Squatting?

INTRODUCTION: Cam femoroacetabular impingement (FAI) is characterized by an osseous overgrowth on the femoral head-neck junction [1], leading to pain and limited range of motion (ROM) during daily life activities [2]. Corrective surgery is highly recommended and performed in order to reduce or eliminate pain and further development of osteoarthritis (OA). However, it is still unclear whether it would lead to improved functional mobility. The purpose was to compare kinematic variables of the operated limb between FAI patients when performing a squat task pre-surgery and at around 2-year follow-up. A secondary objective consisted of express the results in a biomechanical functional score to quantify the joint kinematics of FAI patients compared to healthy control (CTRL) participants. METHODS: Eleven male patients (7 arthroplasty: 34.6±8.1 years, 25.7±3.2 kg/m2; 4 open: 33.3±7.1 years, 24.9±1.9 kg/m2) and 21 CTRL (2F/19M, 33.4±6.7 years, 25.4±3.3 kg/m2) participants were recruited from the orthopaedic surgeon’s clinical practice. Patients were assigned to either an arthroplasty or open FAI surgery correction. The participants signed prior to their participation a consent form approved by the hospital and university ethics board. Patients agreed to undergo motion analysis prior to and 2 years after the surgery. The CTRL were selected based on similar age and BMI as the FAI group and underwent the same motion analysis protocol. At the local hospital, CT scan was performed in all participants to confirm an alpha-angle higher than 55º and also establish their pelvic and knee bony landmarks. At the motion laboratory, the participants were outfitted with 45 reflective markers and performed a minimum of five trials of deep squat at a self-selected pace. Three-dimensional joint kinematics (200 Hz) of the lower limbs were captured using a ten-camera motion analysis system (Vicon, UK). Kinematics data were processed in Nexus 1.8.3 (Vicon, UK) using a modified Plug-In-Gait model and exported with a custom MATLAB script (Mathworks, USA) to calculate group averages and extract relevant variables. All trials were time-normalized based on a full squat cycle (descent and ascent phases) and individual averages for each participant were calculated across the trials. Four kinematic variables were included in the analysis: pelvis, hip, knee, and ankle sagittal angles. The normalized root-mean-square deviation (nRMSD) was calculated between the FAI and the CTRL groups for both pre- and post-surgery conditions, expressed by
Listed In: Biomechanical Engineering, Biomechanics, Orthopedic Research


Knee Biomechanics of Selected Knee Unfriendly Movement Elements in 42-Form Tai Ji

Tai Ji is one of the recommended non-pharmacologic treatments for knee osteoarthritis (OA), but it is not clear if all Tai Ji movements would be suitable and beneficial for knee OA patients. PURPOSE: To examine knee biomechanical characteristics of the selected knee unfriendly Tai Ji movement elements performed in high-pose position compared to slow walking. METHODS: Seventeen healthy participants (age: 23.9 ± 2.7 years, height: 1.73 ± 0.08 m, body mass: 69.0 ± 13.0 kg) performed three trials in each of the following five test conditions: level walking at 0.8 m/s and four identified knee unfriendly Tai Ji movement elements: lunge, pushdown and kick performed in high-pose position (35 ± 5°) and pseudo-step. Simultaneous collection of 3D kinematics (120 Hz) and ground reaction forces (1200 Hz) was conducted. A one-way ANOVA was performed with post hoc paired samples t-tests to determine differences of the high-pose lunge, pushdown, and kick, and pseudo-step and walking. RESULTS: Knee flexion range of motion for high-pose lunge (29.5°), pushdown (24.3°) and kick (11.1°) was lower than pseudo-step (45.0°, p<0.001 for all comparisons) and walking (47.8°, p<0.001 for all comparisons). Peak knee extensor moment was lower in high-pose lunge (1.04 Nm/kg), pushdown (1.01 Nm/kg) and kick (0.48 Nm/kg) than pseudo-step (1.46 Nm/kg, p<0.001 for all comparisons), but higher than walking (0.38 Nm/kg, p<0.001 for all comparisons) except for kick. Peak knee abduction moment was higher in pseudo-step (-0.61 Nm/kg) than high-pose pushdown (-0.43 Nm/kg), kick (-0.44 Nm/kg), and walking (-0.45 Nm/kg, for all comparisons p<0.001). CONCLUSION: These findings demonstrate higher peak knee extensor moment in most of the Tai Ji knee unfriendly movement elements compared to slow walking. It is recommended that Tai Ji participants with knee OA and other knee pathological conditions modify knee unfriendly movement elements (e.g. lunge) and reduce the size of their movements to minimize knee joint loading. The Tai Ji movement elements including pushdown and pseudo-step should be avoided in the Tai Ji exercises designed for knee OA patients.


Listed In: Biomechanics


Are static and dynamic squatting activities comparable?

Background: Numerous studies have described 3D kinematics, 3D kinetics and electromyography (EMG) of the lower limb during quasi-static or dynamic squatting activities. However there is only little information on the comparison of these two squatting conditions. Only one study compared these activities in terms of 3D kinematics, but no information was available on 3D kinetics and EMG. The purpose of this study was to compare simultaneous recordings of 3D kinematics, 3D kinetics and EMG of the lower limb during quasi-static and fast dynamic squats. Methods: Ten subjects were recruited. 3D knee kinematics was recorded with a motion capture system, 3D kinetics was recorded with a force plate, and EMG of 8 muscles was recorded with surface electrodes. Each subject performed a quasi-static squat and several fast dynamic squats from 0° to 70° of knee flexion. Findings: Mean differences between quasi-static and dynamic squats were 1.6° for rotations, 1.8 mm for translations, 38 N ground reaction forces (2.1 % of subjects’ body weight), 6 Nm for torques, 13.0 mm for center of pressure, and 7 µV for EMG (6.3% of the maximum dynamic electromyographic activities ). Some significant differences (P < 0.05) were found in anterior-posterior translation, vertical forces and EMG. Interpretation: All differences found between quasi-static and fast dynamic squats can be considered small. 69.5% of the compared data were equivalent. In conclusion, this study show for the first time that quasi-static and dynamic squatting activities are comparable in terms of 3D kinematics, 3D kinetics and EMG.


Listed In: Biomechanical Engineering, Biomechanics, Gait, Orthopedic Research, Posturography