Graphical representation of range of motion in the assessment of total hip arthroplasty : innovation report

Total Hip Arthroplasty (THA) is a successful technique restoring lost mobility to patients suffering from osteoarthritis. A successful THA normalises the biomechanics of the hip joint so that a patient can achieve the required range of motion to fulfil their daily activities. A recent development in THA implant technologies has been the introduction of femoral neck modularity. Assessment of femoral neck modularity has been limited by two factors. Firstly, range of motion requirement is not well understood and secondly previous clinical reports have lacked a comparison against an established successful THA implant. This study has successfully addressed these limiting factors by developing an innovative range of motion benchmark which considers the activities a person is required to undertake during their daily routine. The benchmark was developed using a systematic review of the literature focussing on hip joint biomechanics. This has been the first study to provide a clinically meaningful representation of hip joint range of motion which permits operative outcome to be directly compared against an established benchmark. Integration of the range of motion benchmark within the surgical environment was achieved by using a surgical navigation measurement device. Intra-operative measurement meant that post-operative range of motion could be simulated and compared against the requirement set by the range of motion benchmark. Distinct outcome measures have been able to be developed using this comparison which has allowed the surgical process to be assessed like a manufacturing system. Using these outcome measures, it was found that femoral neck modularity has greater potential to adjust implant orientation in comparison to non-modular femoral neck implants to achieve the ideal range of motion. However, this potential is being limited due to the current modular neck options available and because of difficulty experienced by the surgeon in assessing implant orientation. These findings have been used to develop a medical device which provides guidance to the surgeon about the THA implant orientation and thus allow them to able to make the correct modular neck choice to maximise range of motion and improve the operative outcome for the patient

Femoroacetabular impingement

There is evidence that Femoroacetabular Impingement (FAI) is a major aetiological factor in end stage Osteoarthritis (OA) of the hip, particularly in the young adult. These patients are usually very active who suffer with persistent or intermittent groin pain. Recent studies have found that the majority of these investigated cases have evidence of mild bone abnormalities. These deformities can occur on either the pelvic or femoral side or a combination of both. They interact to reduce the amount of clearance between the femoral neck and acetabular rim. This results in repetitive early contact between these osseous prominences which if left untreated will eventually progress to OA. This study reviews the clinical presentation, diagnosis and research with regard to FAI. Significant findings include the confirmation that there are gender differences in FAI morphology as well as a strong correlation between the clinical diagnosis of FAI with motion simulations and the soft-tissue damage observed intra-operatively. However, it has been shown that FAI morphology is common within the normal population and presence of this morphology alone does not necessarily mean that subjects will experience motion restriction or joint degeneration. Consequently, the type and intensity of activity a person undertakes as well as presence of more than one radiological indication of FAI contribute to the progression towards OA. Further, the analysis of the activities that a person with FAI undertakes must consider the motion of the pelvis as well as the relative alignment of the femur and pelvis in the neutral posture. These factors along with the bone morphology dictate whether impingement will occur as well as its overall severity. This should be the basis of further development with regard to the motion analysis and simulation of FAI patients to obtain a more accurate diagnosis which the surgeon can respond to have a more effective surgical plan

Femur first navigation can reduce impingement severity compared to traditional free hand total hip arthroplasty.

Impingement is a major source of dislocation and aseptic loosening in total hip arthroplasty (THA). We compared impingement free range of motion (ROM) using a novel computer navigated femur first approach to conventional THA. In addition, impingement between genders was also explored. In a retrospective analysis of 121 THA patients, subject-specific post-operative ROM was simulated using post-operative 3D-CT data, and compared with the benchmark ROM, essential for activities of daily living. Three parameters were defined to express both implant-to-implant (ITI) and bone-to-bone (BTB) impingement - coverage percentage, third angle, and impingement severity. Although coverage percentage was similar between the navigated and conventional group for both ITI (p = 0.69) and BTB (p = 0.82) impingement, third angle was significantly reduced in the navigation group for both ITI (p = 0.02) and BTB (p = 0.05) impingement. Impingement severity for both ITI (p = 0.01) and BTB (p = 0.05) was significantly decreased in the navigation group compared to the conventional. Impingement severity in men was considerably higher compared to women for both ITI (p = 0.002) and BTB (p = 0.02). Navigation guided femur first THA is able to improve alignment of ROM axis, and consequently, to reduce impingement in THA. Men seem to be more prone to impingement than women

Evaluating the capability of laser scanning to measure an automotive artefact : a comparison study of touch trigger probe and laser-scanning

Abstract: In the automotive industry dimensional quality control is an important part of the production process, often carried out using coordinate measuring machines (CMMs). However, CMMs used in conjunction with touch probes have a relatively low measurement speed. There is also a close link between the cost of measurement and the number of discrete points captured, leading to a trade-off between the number of points that can be measured and the measurement time. Laser scanners offer a faster alternative to touch probe measurement, but have certain limitations. A number of studies have considered the accuracy of laser scanning using small artefacts; however, little work has been done on the verification of on-CMM laser scanning systems for large volume, industry-relevant measurement applications. In this research, a nominal representation of a vehicle body was used and 104 standard features were measured. The results show that the laser scanning sensor and CMM used in this study would, for the majority of measurements, provide a level of accuracy and repeatability better than which is typically required by automotive manufacturers for body shell quality inspection applications

Moving towards in-line metrology : evaluation of a Laser Radar system for in-line dimensional inspection for automotive assembly systems

The increasing interest towards intelligent systems has led to a demand for the development of zero-defect strategies, with a paradigm shift from off-line and dedicated to in-line metrology with integrated robotic systems. However, a major barrier preventing the systematic uptake of in-line metrology is the lack of evaluation of system capability in terms of accuracy, repeatability and measurement time, when compared to the well-established coordinate measuring machine (CMM). In this study, a robotic Laser Radar (LR) solution is assessed in the context of automotive dimensional inspection of Body-In-White (BIW) applications. The objective is both to understand the effect of robot re-positioning error on measurement accuracy and repeatability and to compare measurement results against a CMM. Eighty-one surface points, six edge points, twenty-five holes and sixteen slots were selected from an industry standard measurement plan. Whilst LR exhibits a lower measurement accuracy than twin-column CMM, its repeatability is well within the specification limits for body shell quality inspection. Therefore, as a real-time in-line metrology tool, it is a genuine prospect to exploit. This research makes a significant contribution toward in-line metrology for dimensional inspection, for automotive application, for rapid detection and for correction of assembly defects in real time, with subsequent reduction of scrap and number of repairs/re-works

Evaluation of a multi-sensor horizontal dual arm Coordinate Measuring Machine for automotive dimensional inspection

Multi-sensor coordinate measuring machines (CMM) have a potential performance advantage over existing CMM systems by offering the accuracy of a touch trigger probe with the speed of a laser scanner. Before these systems can be used, it is important that both random and systematic errors are evaluated within the context of its intended application. At present, the performance of a multi-sensor CMM, particularly of the laser scanner, has not been evaluated within an automotive environment. This study used a full-scale CNC machined physical representation of a sheet metal vehicle body to evaluate the measurement agreement and repeatability of critical surface points using a multi-sensor horizontal dual arm CMM. It was found that there were errors between CMM arms and with regard to part coordinate frame construction when using the different probing systems. However, the most significant effect upon measurement error was the spatial location of the surface feature. Therefore, for each feature on an automotive assembly, measurement agreement and repeatability has to be individually determined to access its acceptability for measurement with a laser scanner to improve CMM utilisation, or whether the accuracy of a touch trigger probe is required

Passive diastolic modelling of human ventricles : effects of base movement and geometrical heterogeneity

Left-ventricular (LV) remodelling, associated with diastolic heart failure, is driven by an increase in myocardial stress. Therefore, normalisation of LV wall stress is the cornerstone of many therapeutic treatments. However, information regarding such regional stress–strain for human LV is still limited. Thus, the objectives of our study were to determine local diastolic stress–strain field in healthy LVs, and consequently, to identify the regional variations amongst them due to geometric heterogeneity. Effects of LV base movement on diastolic model predictions, which were ignored in the literature, were further explored. Personalised finite-element modelling of five normal human bi-ventricles was carried out using subject-specific myocardium properties. Model prediction was validated individually through comparison with end-diastolic volume and a new shape-volume based measurement of LV cavity, extracted from magnetic resonance imaging. Results indicated that incorporation of LV base movement improved the model predictions (shape-volume relevancy of LV cavity), and therefore, it should be considered in future studies. The LV endocardium always experienced higher fibre stress compared to the epicardium for all five subjects. The LV wall near base experienced higher stress compared to equatorial and apical locations. The lateral LV wall underwent greater stress distribution (fibre and sheet stress) compared to other three regions. In addition, normal ranges of different stress–strain components in different regions of LV wall were reported for five healthy ventricles. This information could be used as targets for future computational studies to optimise diastolic heart failure treatments or design new therapeutic interventions/devices

Microtomography-based numerical simulations of heat transfer and fluid flow through β-SiC open-cell foams for catalysis

β-SiC open-cell foams are promising materials for catalytic supports with improved heat and mass transfer at moderate pressure drops. In this work, 3-dimensional (3D) models of a 30 ppi (pores per inch) β-SiC open-cell foam were generated using X-ray microtomography data. The resulting foam models were then used for finite element analysis (FEA) and computational fluid dynamics (CFD) simulations of heat transfer and fluid flow on the pore-scale. The FEA results demonstrate that (i) the overall effective thermal conductivity from direct simulations is comparable to the results estimated by experimental measurement, and are in the order of 10−1 W m−1 K−1 and (ii) thermal transport through fluid-saturated β-SiC foams depends on the solid-to-fluid conductivity ratio. By employing realistic foam models, pore-scale CFD simulations of fluid flows revealed the microscopic characteristics of laminar flow through open-cell foams. The anisotropic feature of realistic foam models promotes the axial and radial mixing of fluids in and after the foam element. The diffusion coefficient of laminar flow within foams was estimated at 10−4 m2 s−1, which is much larger than the molecular diffusion coefficient in a typical laminar flow in an open channel

Evaluation of range of motion restriction within the hip joint

In Total Hip Arthroplasty, determining the impingement free range of motion requirement is a complex task. This is because in the native hip, motion is restricted by both impingement as well as soft tissue restraint. The aim of this study is to determine a range of motion benchmark which can identify motions which are at risk from impingement and those which are constrained due to soft tissue. Two experimental methodologies were used to determine motions which were limited by impingement and those motions which were limited by both impingement and soft tissue restraint. By comparing these two experimental results, motions which were limited by impingement were able to be separated from those motions which were limited by soft tissue restraint. The results show motions in extension as well as flexion combined with adduction are limited by soft tissue restraint. Motions in flexion, flexion combined with abduction and adduction are at risk from osseous impingement. Consequently, these motions represent where the maximum likely damage will occur in femoroacetabular impingement or at most risk of prosthetic impingement in Total Hip Arthroplasty