Modified conventional gait model vs. Six degrees of freedom model: A comparison of lower limb kinematics and associated error

A new method called MiKneeSoTA to minimize knee soft-tissue artifacts in kinematic analysis

The use of marker-based optical motion capture to estimate joint kinematics during gait is currently limited by errors associated with soft-tissue-induced motion artefacts (STIMA) and ambiguity in landmark palpation. This study therefore presents a novel protocol aiming to Minimize Knee Soft-Tissue Artefacts (MiKneeSoTA) and their effect on kinematic estimates. Relying on an augmented marker set and a new inverse kinematics approach, our method leverages frame-by-frame optimization to adjust best-fit cylinders that have been automatically generated based on the relative position of lower limb markers during an initial static trial. Tibiofemoral rotations and translations are then calculated along the anatomical joint axes based on the relative 3D motion of these cylinders. When compared against the conventional Helen-Hayes approach, in vivo assessment of fifteen healthy subjects revealed the MiKneeSoTA approach led to kinematic profiles with significantly lower standard deviations in joint rotations across trials, and even visibly reduced the presence of high frequency fluctuations presumably associated with e.g. soft-tissue vibration. In addition to agreeing with previously published bone pin and fluoroscopy datasets, our results illustrate MiKneeSoTA's ability to abate the effect of STIMA induced by lateral knee ligaments. Our findings indicate that MiKneeSoTA is in fact a promising approach to mitigate knee joint STIMA and thus enable the previously unattainable accurate estimation of translational knee joint motion with an optoelectronic system.

Exploring the issue of 'functionality' in isokinetic dynamometry

Strength is a primary and modifiable contributor to performance, injury risk, and rehabilitative success. The gold standard measure of strength is the isokinetic dynamometer, providing the clinician with the opportunity to manipulate contraction modality, range, and speed about a joint. However, criticism has highlighted a lack of functional relevance, with arbitrary selection of speed across the full range. To better understand function, biomechanical analysis of movement can inform a bespoke isokinetic data collection protocol. In this case, we use walking gait, a function goal for daily living and clinically assessed following knee replacement surgery for example. Concentric knee flexor and extensor demand was evident at an average angular velocity of 70°·s-1, whilst eccentric knee flexor and extensor demands were evident at speeds of 192°·s-1 and 165°·s-1, respectively. The efficacy of isokinetic dynamometry can be enhanced with bespoke data collection protocols, which better reflect the functional demands of the clinical movement objective.

Comparison of plugin and redundant marker sets to analyze gait kinematics between different populations

BACKGROUND

Gait model consists of a marker set and a segment pose estimation algorithm. Plugin marker set and inverse kinematic algorithm (IK.) are prevalent in gait analysis, especially musculoskeletal motion analysis. Adding extra markers for the plugin marker set could increase the robustness to marker misplacement, motion artifacts, and even markers occlusion. However, how the different marker sets affect the gait analysis's kinematic output is unclear. Therefore, this study aims to investigate the effect of marker sets on the kinematic output during level walking in different populations.

RESULTS

In all three planes, there are significant differences (P < 0.05) between marker sets in some kinematic variables at the hip, knee, and ankle. In different populations, the kinematic variables that show significant differences varied. When comparing the kinematic differences between populations using the two marker sets separately, the range of motion (ROM) of hip flexion was only found to be a significant difference using the redundant marker set, while the peak internal rotation at the knee was only found a significant difference using plugin marker set. In addition, the redundant marker set shows less intra-subject variation than the plugin marker set.

CONCLUSION

The findings in this study demonstrate the importance of marker set selection since it could change the result when comparing the kinematic differences between populations. Therefore, it is essential to increase the caution in explaining the result when using different marker sets. It is crucial to use the same marker set, and the redundant marker set might be a better choice for gait analysis.

The gait abnormality index: A summary metric for three-dimensional gait analysis

BACKGROUND

This paper proposes an easy to calculate and adaptable summary gait metric, the Gait Abnormality Index (GAI), which is capable of simultaneously including kinematic and kinetic data, overcoming a key limitation of existing metrics.

RESEARCH QUESTION

To determine the validity, reliability and sensitivity of the GAI.

METHODS

The GAI is calculated by averaging Gait Abnormality Scores, which are normalised distance metrics used to describe the deviation of pathological gait data from that of healthy controls. Validity was assessed using Pearson's correlation analysis to explore relationships between the GAI and the Gait Profile Score. Test-retest reliability of the GAI was assessed using intra-class correlation coefficients (ICC) and standard error of the measurement (SEM), and data from total hip arthroplasty patients. An independent samples t-test was used to compare GAI scores between knee osteoarthritis and total hip arthroplasty patients to explore the metrics sensitivity.

RESULTS

A strong positive correlation (r ≥ 0.896; p < 001) was reported between the GAI and the Gait Profile Score. Good test-retest reliability (ICC =0.830) was reported for the GAI. Knee osteoarthritis patients displayed significantly (p = .017; Hedge's g effect size = 0.98) greater GAI scores compared to total hip arthroplasty patients, with the mean difference (0.34 a.u) above the SEM (0.15 a.u).

SIGNIFICANCE

The GAI offers an easy to calculate summary metric for three-dimensional gait analysis, which displays good validity and reliability, and is sensitive to different pathological conditions.

Influence of quality of reduction using radiological criteria on kinematics and kinetics in ankle fractures with unstable syndesmotic injury

BACKGROUND

In ankle fractures with syndesmotic injury, the anatomic reduction of the ankle mortise is crucial for preventing osteoarthritis. Yet, no studies have analysed the effect of surgical reduction after unstable ankle fractures on patients' active functional outcome.

METHODS

The Intraoperative 3D imaging data of patients surgically treated between 2012 and 2019 for ankle fracture with concomitant syndesmotic injury were reviewed. 58 patients were allocated to two groups depending on whether the criteria for radiologically optimal reduction were met (39 patients) or not (19 patients). Criteria for optimal reduction were composed of objectively measured and subjectively rated data. After undertaking the Olerud/Molander ankle score, a gait analysis and several active function tests using 3D motion capture were performed in order to evaluate kinetic and kinematic differences between both groups.

FINDINGS

Patients showed deficits of range of motion and balance parameters on the injured ankle, however, there were no significant differences between both groups.

INTERPRETATION

Although, the data did not show that radiological reduction criteria have a statistically significant effect on active functional outcome after a mean follow up time of 5.7 years, tendencies for a better outcome of patients that met the criteria could be seen. It also must be taken into consideration that results are limited by case number and allocation ratio, which made a sub-analysis of the separate reduction criteria unfeasible.

Exploring pelvis and thigh movement and coordination patterns during walking in patients after total hip arthroplasty

BACKGROUND

Patients after total hip arthroplasty (THA) have altered hip kinematics compared to healthy controls, specifically hip extension and range of motion are lower. Exploring pelvis-thigh coordination patterns and coordination variability may help to elucidate why differences in hip kinematics are evident in patients following THA.

RESEARCH QUESTION

Do sagittal plane hip, pelvis and thigh kinematics, and pelvis-thigh movement coordination and coordination variability differ between patients following THA and healthy controls during walking?

METHODS

Sagittal plane hip, pelvis and thigh kinematics were collected using a three-dimensional motion capture system while 10 patients who had undergone THA and 10 controls walked at a self-selected pace. A modified vector coding technique was used to quantify pelvis-thigh coordination and coordination variability patterns. Peak hip, pelvis and thigh kinematics and ranges of motion, and movement coordination and coordination variability patterns were quantified and compared between groups.

RESULTS

Patients after THA have significantly (p ≤ .036; g ≥ 0.995) smaller peak hip extension and range of motion, and peak thigh anterior tilt and range of motion compared to controls. Additionally, patients following THA have significantly (p ≤ .037; g ≥ 0.646) more in-phase distally and less anti-phase distally dominated pelvis-thigh movement coordination patterns compared to controls.

SIGNIFICANCE

The smaller peak hip extension and range of motion displayed by patients following THA is due to smaller peak anterior tilt of the thigh, which in turn limits thigh range of motion. The lower sagittal plane thigh, and in turn hip, motion used by patients after THA may be due to increases in the in-phase coordination of pelvis-thigh motion patterns, which cause the pelvis and thigh to work as a singular functional unit.

Wand-mounted lateral markers are less prone to misplacement and soft-tissue artefacts than skin-mounted markers when using the conventional gait model

BACKGROUND

The conventional gait model (CGM1) is extensively used for 3D clinical gait analysis. It uses lateral wand-mounted markers for the thigh and shank segments to avoid colinearity of the tracking markers. However, gait analysts may be tempted to use skin-mounted markers instead.

RESEARCH QUESTION

Does it matter if the lateral markers for the thigh and shank segments are mounted on wands or directly taped to the skin when using the CGM1?

METHODS

Gait sessions from 147 and 73 patients equipped with wand-mounted and skin-mounted markers, respectively, were extracted from the database of a single clinical gait laboratory. The marker trajectories were reprocessed with the CGM1. The risk of marker colinearity was assessed from the planar angle constructed from the proximal joint center, the lateral joint marker and the lateral segmental marker (i.e. skin or wand). We assessed the effect of marker misplacement and soft-tissue artefact on kinematics.

RESULTS

The averaged planar angles calculated from static ranged from 10° to 30° and 7° to 21° for the skin-mounted thigh and shank markers respectively, while planar angles were always larger than 25° with wand-mounted markers. One cm misplacement of the thigh marker altered hip rotation by 10° if skin-mounted against 5° if wand-mounted. Soft tissue artefact led to 7.6° or 4.3° depending if it was skin- or wand-mounted, respectively.

SIGNIFICANCE

Our analysis showed moderate risk of collinearity, increased effect of STA, and larger potential effect of marker misplacement with the use of skin- rather than wand-mounted markers.