Developing capacity for assessment of early interventions in the hip

Lead Research Organisation: University of Leeds
Department Name: Mechanical Engineering

Abstract

Hip osteoarthritis causes debilitating pain and function loss. Current treatment includes pain relief, then possibly early intervention surgery if a patient is less than 50 years old and has a bony deformity accelerating osteoarthritis progression, and finally total hip replacement (THR). Significant scope to optimise early interventions exists by developing novel computational and anatomical experimental simulations that will enable stratification of patient variables related to their effect on outcomes, and inform the surgical intervention.
The hip is a ball and socket joint with conforming cartilage surfaces, and the acetabulum socket is deepened by a fibrocartilage rim (labrum). Factors associated with hip damage include trauma, labral tears and extremes in anatomical shape including femoroacetabular impingement (where there is excessive bone at the anterior neck-head junction or a deepened acetabulum) and dysplasia (shallow, less constraining acetabulum).
In both conditions, there is scope for surgery to restore more "normal" contact mechanics reducing bony impingement and repairing the labrum. These interventions are rapidly increasing in frequency, but support for technique efficacy is limited, with a lack of scientific evidence to demonstrate the extent of the intervention that might indicate patient benefit. Research to date in the iMBE has demonstrated the potential for whole joint natural hip testing in a hip simulator (Pallan PhD thesis) and parametric geometric analysis in computational models (Cooper et al, Numerical Method in Biomedical Engineering, 2017). The aim of this project is to develop and assess experimental simulations of the natural hip joint that can inform early intervention hip surgery to optimise patient outcomes.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512291/1 01/10/2017 30/06/2022
2091200 Studentship EP/R512291/1 01/10/2017 30/09/2021 Mudit Dubey
 
Description Current research has involved recreating the initial investigations conducted by Pallan, 2016, in simulating the biomechanics of natural porcine hip tissue in a single station hip simulator and characterising the structure of the triagular rim of the hip socket, the acetabular labrum.

Preliminary method development has been completed, during which methods used by Pallan, 2016 have been optimised and corrected for experimental errors, including improvements to equipment used to mount tissue into the simulator, investigation of the loading profiles used for natural tissue testin used to mimic physiological loading, improvements to the overall method from dissection, to recreating the alignment and positioning requried to mimic human gait with a porcine model and finally, using hisological staining of porcine hip labrum tissue to determine the structure of the porcine labrum, how it compares with human labrum and how it differs along its length at different regions of the acetabulum (anteriorly, superiorly, posteriorly and inferiorly to the transverse acetabular ligament).

Furthermore, initial biological characterisation of the labrum resulted in a collaboration with the Biophysics department at the University of Exeter with Dr. Peter Winlove and Dr. Ellen Green where the regional variation and microstructure of the labral tissue was investigated comparing the different transitional zones and comparing it to articular cartilage.

Finally, the novel techniques are being implemented to start recreating damage found via cam or picer type deformities using the single station hip simulator through the use of altered positioning or modified gait cycles on porcine hip tissue which do not present with cam deformities (bump on femoral head or neck) or deformed acetabula.
Exploitation Route The aim of this research is to develop a experimental model which can reproduce damage or tearing to the acetabular labrum which is found clinically with patients with femoroacetabular impingement or hip dysplasia. Outcomes of the research will result in a model which can reproduce labral tears on porcine hips in the simulator which can help understand the behavior of damage found clinicially, the opportunity to evaluate currently available interventions on damaged tissue, such as labral repair techniques. By evaluating early interventions for labral tears and non-arthroplasty procedures, surgeons and healthcare practitioners will be able to determine the best course of treatment for patients. Additionally, by understanding the nature of these conditions and the corresponding damage, the industry will be able to develop new solutions and product lines for patients. Finally, by continuing the research, further complexity can be added to the experimental model for combined cases of impingement and instability caused by dysplasia and the functional role of the labrum in preventing damage and consequent relation to the early onset of osteoarthritis.
Sectors Education,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description Multiphoton Imaging for Characterising Labral Damage 
Organisation University of Exeter
Department School of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution During the collaboration, dissected porcine hip tissue samples were transported from Leeds to Exeter for investigation. In the future, this will translate onto porcine tissue which has been previously loaded under physiological loads, or abnormal loading conditions or damaged labrum samples where the presence of internal rupturing or collagen fibre damage will be investigated. Additionally, knowlegde of labrum structure was provided via previous imaging work conducted at the University of Leeds, including biological characterisation methods such as histology.
Collaborator Contribution Exeter has a multiphoton imaging and spectroscopy lab with three multiphoton contrast mechanisms in a single microscope. The benefits of this setup include non-invasive image contrast, strain-free imaging of multiple species within a single sample and detailed spectroscopic information to detect and characterise biomolecules in vivo. Additionally, this method offers more resolution other medical imaging modalities such as MRI and CT. At Exeter, the biophysics group have investigated the structural organisation (Thomas et al., 2013) of elastin and collagen fibres which determine the mechanical properties of biological tissue. The group have recently developed a novel method using light polarisation which can be used to determine the angular disorder of elastin and collagen. Mansfield et al., 2019 developed two different methods to take multiphoton images in different areas on the articular surface at a depth of 3┬Ám from the articular surface observing various different arrangements of fibres including parallel, crossed and sparse arrangement in the different regions of the equine metacarpophalangeal joint. Therefore, the technique to my own research as it can provide high resolution detail on the orientation and arrangement as well as the disruption that takes place when cartilage is damaged. When this method is applied to the labrum, it will enable validation the findings observed though histology and immunohistochemistry as well as the recreation of damage found using the natural hip simulator. These experiments will require the second harmonic generation multiphoton imaging (SHG). The requirements for this method are an environment without a centre of symmetry which produces signals, which is the case in the labrum. In this process two photons are mixed in with the sample to generate a third proton generating label free images. Collagen fibres have been known to exhibit SHG.
Impact During the placement, all the imaging modalities (multiphoton, polarised, CARS) were investigated seperately during placement. The polarised light microscope was very sensitive and prevented images from being collected easily between samples. The multiphoton polarised light microscope can provide details of individual fibre strands and follow the orientation. Additonally the method can trace the reorientation of the dipoles thus allowing measurements of changes in strain through intrafibrillar tension/compression, or similar loading as would be expected from physiological loads. In the future, combined imaging capabilities can develop the method for a more clinically relevant application to study and compare to compare tissue damage at microscale and matrix disruption using multiphoton+CARS or polarisation. In addition, when the equipment is upgraded, a rig used for applying tensile or compressive forces up to 1mm of strain can help determine the matrix interactions of collagen fibres and where the first presence of tearing occurs. The method is non-destructive, rapid does not require staining,therefore has the potential to allow consistent, semi-quantitative and efficient method for investigating microscale damage/changes.
Start Year 2019