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Motion analysis deals with determining what and how activities are being performed by a subject, through the use of sensors. The process of answering the what question is commonly known as classification, and answering the how question is here referred to as characterization. Frequently, combinations of inertial sensor such as accelerometers and gyroscopes are used for motion analysis. These sensors are cheap, small, and can easily be incorporated into wearable systems. The overall goal of this thesis was to improve the processing of inertial sensor data for the characterization of movements. This thesis presents a framework for the development of motion analysis systems that targets movement characterization, and describes an implementation of the framework for gait analysis. One substantial aspect of the framework is symbolization, which transforms the sensor data into strings of symbols. Another aspect of the framework is the inclusion of human expert knowledge, which facilitates the connection between data and human concepts, and clarifies the analysis process to a human expert. The proposed implementation was compared to state of practice gait analysis systems, and evaluated in a clinical environment. Results showed that expert knowledge can be successfully used to parse symbolic data and identify the different phases of gait. In addition, the symbolic representation enabled the creation of new gait symmetry and gait normality indices. The proposed symmetry index was superior to many others in detecting movement asymmetry in early-to-mid-stage Parkinson's Disease patients. Furthermore, the normality index showed potential in the assessment of patient recovery after hip-replacement surgery. In conclusion, this implementation of the gait analysis system illustrated that the framework can be used as a road map for the development of movement analysis systems.

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Although poor walking is the most common symptom of peripheral artery disease (PAD), reported results are inconsistent when comparing gait parameters between PAD patients and healthy controls. This inconsistency may be due to frailty, which is highly prevalent among PAD patients. To address this hypothesis, 41 participants, 17 PAD (74 +/- 8 years) and 24 aged-matched controls (76 +/- 7 years), were recruited. Gait was objectively assessed using validated wearable sensors. Analysis of covariate (ANCOVA) tests were used to compare gait parameters between PAD and non-PAD groups, considering age, gender, and body mass index as covariates, while stratified based on frailty status. According to the Fried frailty index, 47% of PAD and 50% of control participants were non-frail and the rest were classified as pre-frail. Within non-frail participants, gait speed, body sway during walking, stride length, gait cycle time, double-support, knee range of motion, speed variability, mid-swing speed, and gait initiation were significantly different between PAD and control groups (effect size d = 0.75 +/- 0.43). In the pre-frail group, however, most of the gait differences were diminished except for gait initiation and gait variability. Results suggest that gait initiation is the most sensitive parameter for detecting gait impairment in PAD participants when compared to controls, regardless of frailty status (d = 1.30-1.41; p<0.050). The observed interaction effect between frailty and PAD on gait parameters confirms the importance of assessing functionality in addition to age to provide more consistency in detecting motor performance impairments due to PAD.

The goal of this research work was to introduce the whole process of developing and validating a 3D lower extremity musculoskeletal model and to test the ability of the model to predict the muscles recruitment of the different muscles involved in human locomotion as well as determining the corresponding forces and moments generated around the different joints in the lower extremity. Therefore the model can be applied in one of the important fields of orthopaedics which is joint replacement; the case study used in such application is the total knee replacement. The knee reaction forces were compared to the pattern obtained by Harrington (1992), where the hip moment components (Flexion/extension, internal/external, and abduction/adduction) were all compared to the patterns obtained from the Hip98 data base. It was shown in the different graphs of joints forces and moments that the model was able to produce very close results when comparing pattern and magnitude to the literature data. Thus, this 3D biomechanical model is sophisticated enough to be used for surgery evaluation such as in total knee replacement, where the damaged cartilage and bone are removed from the surface of the knee joint and replaced with a man-made. The case study of the second part of the research work presented involved the comparison of the gait pattern between two main knee joint types, Metallic and Allograft knee joints against normal subjects (Control group). A total of fifteen subjects participated in this study, five subjects in each group. It was concluded that based on the study conducted and the statistical evidence obtained that the introduced model can be used for applications that involves joint surgeries such as knee replacement that ultimately can be utilized in surgery evaluation.

This thesis examined the immediate biomechanical effects of valgus unloader brace application in participants with moderate medial compartment knee osteoarthritis during gait. Thirty-three individuals were prescribed a valgus unloader brace. 3D knee moments and angles were calculated during walking with and without the brace. Principal Component Analysis identified amplitude and temporal changes of the moment and angle waveforms during gait. Three groups were identified based on the change in knee adduction moment magnitude with brace application. Two-Way ANOVA tested for differences among groups and conditions in principal component scores, as well as discrete varus thrust values. There existed three subgroups of participants identified by different gait adaptations to brace application. The brace had temporal and magnitude effects on 3D kinetics and kinematics for the participant group. This study showed that the brace does not provide a consistent change to knee joint mechanics. These results have implications for brace prescription.

The purpose of this thesis was to investigate gait analysis methods used to minimise soft tissue artefact (STA) when measuring the kinematics and kinetics of human gait. STA affects all gait analysis methods and is considered to be one of the major sources of error in clinical motion analysis. A systematic review was initially performed to quantify the magnitude of STA for different areas of the lower limbs during gait analysis. Despite the high quality of the existing literature, the results of the review were inconclusive regarding the exact magnitude of STA during human gait analysis. Previously, there were no methods used consistently throughout the reviewed studies to assess STA. The primary aim of this thesis was to determine the most valid method for minimising STA during human gait analysis. / Whilst the systematic review provided equivocal results on the magnitude of STA, it was able to confirm that STA at the tibia is less than for the femur segment. As a result, the tibial segment was investigated to determine marker locations that are least susceptible to STA. Twenty unimpaired young adults were included in the study and were instrumented with 36 markers, including 10 markers on each shank segment. The markers were well spread across the tibial segment in order to assess as many locations as possible. Four markers located on the tibia were less susceptible to STA. These were the proximal and distal anterior tibial crest markers as well as the medial and lateral malleolar markers. These markers were rigid to one another thus were rigid to the underlying bone. / In order to assess the modelling methods proposed in the literature a gold standard comparison was required. A potential new gold standard method was identified as 3-D freehand ultrasound (3-DUS). This was believed to be a non-invasive and cost effective method for locating internal bony structures. A validation of the new method (3-DUS) against MRI was performed to ensure the new gold standard was a valid methodology. The two methods, 3-DUS and MRI were compared for their accuracy in determining the location of the HJC within the pelvis segment. Twenty unimpaired participants were included in this study. The participants were of variable ages and physical composition. The difference between 3-DUS and MRI determined distance between the left and right HJC was 4.0 ± 2.3mm. It was determined that the results from 3-DUS were clinically not significantly different to MRI. The results of this investigation indicated that 3-DUS could be used as a gold standard measurement for three dimensional gait analysis (3-DGA) research. / The new gold standard method was used to validate existing 3-DGA modelling methods to determine which obtained the most accurate location of the HJC. To date, the greatest clinical application for gait analysis is as a test for people with central nervous system disorders associated with spasticity, especially children with cerebral palsy (CP) (Simon 2004). For this reason, 53 patients with gait abnormalities who had been referred to the Royal Children’s Hospital gait laboratory for a 3-DGA were tested. The participant sample represented patients who were referred to the Hugh Williamson Gait Analysis Laboratory (HWGAL). This was apparent because from 2008-2009 69% of patients at HWGAL had a diagnosis of CP, of the sample included in this study, 67% had a CP diagnosis. / Patients underwent a 3-DGA in addition to a 3-DUS of their left and right femoral heads. Resultant ultrasounds were assessed for the quality of the images and 46 patients were included for data analysis. Seven different methods were investigated for the determination of the HJC and four of these were analysed in two different ways, as such there were 11 models compared to 3-DUS. The Harrington et al method obtained the most accurate and repeatable results where the 3-D location error was 14.3 ± 8.0mm. That method considerably outperformed the functional techniques that had previously been proposed in the literature. This highlighted the importance of testing research techniques in target populations. / To conclude, this thesis has identified locations on the tibia which are most rigid to the underlying bone as well as a new gold standard measurement tool suitable for use in 3-D gait analysis research. The thesis has also demonstrated the validity of using functional methods for determining the HJC in pathological populations. Limitations of previous research were identified, including a lack of translation of research findings into clinical practice. Future work following on from this thesis should aim to address this issue.

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A critical review of studies related to the modelling of the human locomotor system is given. Kinematic and dynamic modelling and analysis of the pelvis-leg apparatus as an ensemble of four rigid body segments are described. Experiments were performed on two patients with custom-made instrumented massive proximal femoral prostheses implanted after tumour resection. Telemetered axial forces transmitted along the prostheses, together with kinematic, force plate and electromyographic data, were recorded synchronously during level walking, single and double leg stance, and isometric tests of the hip muscles. A sagittal plane model of the locomotor system, with an anatomical model of the knee joint, was developed from an existing model and used for a comparative study of methods for the calculation of the internal forces. A three-dimensional computer graphics-based animated model of the locomotor system was developed, with the hip as a ball-and-socket joint, the knee as a parallel spatial mechanism and the ankle as a two-hinge complex. Thirty-four muscles or muscle groups were included. A method for the determination of the orientation of multi-joint systems from surface markers was developed to take account of measurement errors including skin movement artefacts. Both the 2D and 3D models of the locomotor system were evaluated and validated quantitatively with the telemetered femoral axial forces. It is concluded that (a) a significant part of the bending moments along limbs are transmitted by a combination of tensile forces in muscles and compressive forces in bones so that moments transmitted by the bones are much less than the limb moments, (b) bi-articular muscles play a major role in modulating forces in bones, (c) appropriate simulation of muscle forces is important in experimental or theoretical studies of load transmission along bones, (d) computer graphics-based modelling and animation are important tools in bridging the gap between clinical users and biomechanists.

Walking is the most common form of human locomotion and the systematic study thereof is known as gait analysis. Measurement and assessment thereof have application in many fields including clinical diagnosis, rehabilitation and biomechanics. The process of gait evaluation is typically done using an optical motion analysis system combined with stationary force platforms. This is considered the gold standard, but unfortunately, has several drawbacks. It is expensive, requires dedicated laboratories with spatial restrictions, calls for lengthy set up and post-processing times and cannot be used in 'real-world' environments. Alternative systems based on wearable sensors have been developed to overcome these limitations. The Council for Scientific and Industrial Research (CSIR) has therefore developed a prototype wearable sensor unit consisting of an inertial measurement unit (IMU). The objective of the current study is, therefore, to advance the prototype to a wearable multi-sensor system for quantitative gait analysis. The focus is on the development of the pre- and post-processing algorithms and methods used to transform the measurements into interpretable information. The focus outlined includes establishing techniques for synchronising the data from the sensors offline, pre-processing the signals, developing algorithms for stride and gait event detection, selecting an appropriate gait model and defining methods for estimating gait parameters. The determined parameters were the spatio-temporal and joint kinematics (hip, knee and ankle). The algorithms and new system were validated against the Vicon motion capture system through gait analyses. The twenty able-bodied volunteers that took part were required to walk across the laboratory six times at three self-selected walking speeds (slow, normal and fast). For the sake of simplicity and due to various limitations, only data in the sagittal plane of the right lower limb of each volunteer was used to validate the wearable system and associated algorithms. The results obtained were then evaluated against several validation criteria. The absolute mean difference between the estimated timing of detected gait events of the two systems was consistently small (between 0.021 and 7.25% of the gait cycle overall). The spatially dependent parameters, stride length and walking speed, had significant maximum mean absolute percentage errors (31.9 and 34.5% respectively), but with little variation. Excluding outliers, that of the temporal parameters, stride time and cadence, was significantly lower (5.7 and 5.6% respectively). The kinematic results were substantially comparable with a minimum correlation co-efficient of 0.86 and a maximum RMSE of 7.8 degrees with little variation implying repeatability. Although there were some discrepancies between the outputs, the wearable sensor system and its corresponding algorithms were considered feasible and potentially beneficial to developing countries like South Africa. Recommendations for future work include synchronising data between the wearable and reference system for stride-to-stride comparisons and validating algorithms using a known reliable wearable system. / Dissertation (MEng)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / MEng / Unrestricted