An automated system for polymer wear debris analysis in total disc arthroplasty using convolution neural network

Introduction: Polymer wear debris is one of the major concerns in total joint replacements due to wear-induced biological reactions which can lead to osteolysis and joint failure. The wear-induced biological reactions depend on the wear volume, shape and size of the wear debris and their volumetric concentration. The study of wear particles is crucial in analysing the failure modes of the total joint replacements to ensure improved designs and materials are introduced for the next generation of devices. Existing methods of wear debris analysis follow a traditional approach of computer-aided manual identification and segmentation of wear debris which encounters problems such as significant manual effort, time consumption, low accuracy due to user errors and biases, and overall lack of insight into the wear regime.Methods: This study proposes an automatic particle segmentation algorithm using adaptive thresholding followed by classification using Convolution Neural Network (CNN) to classify ultra-high molecular weight polyethylene polymer wear debris generated from total disc replacements tested in a spine simulator. A CNN takes object pixels as numeric input and uses convolution operations to create feature maps which are used to classify objects.Results: Classification accuracies of up to 96.49% were achieved for the identification of wear particles. Particle characteristics such as shape, size and area were estimated to generate size and volumetric distribution graphs.Discussion: The use of computer algorithms and CNN facilitates the analysis of a wider range of wear debris with complex characteristics with significantly fewer resources which results in robust size and volume distribution graphs for the estimation of the osteolytic potential of devices using functional biological activity estimates

An automated system for polymer wear debris analysis in total disc arthroplasty using convolution neural network

Introduction: Polymer wear debris is one of the major concerns in total joint replacements due to wear-induced biological reactions which can lead to osteolysis and joint failure. The wear-induced biological reactions depend on the wear volume, shape and size of the wear debris and their volumetric concentration. The study of wear particles is crucial in analysing the failure modes of the total joint replacements to ensure improved designs and materials are introduced for the next generation of devices. Existing methods of wear debris analysis follow a traditional approach of computer-aided manual identification and segmentation of wear debris which encounters problems such as significant manual effort, time consumption, low accuracy due to user errors and biases, and overall lack of insight into the wear regime. Methods: This study proposes an automatic particle segmentation algorithm using adaptive thresholding followed by classification using Convolution Neural Network (CNN) to classify ultra-high molecular weight polyethylene polymer wear debris generated from total disc replacements tested in a spine simulator. A CNN takes object pixels as numeric input and uses convolution operations to create feature maps which are used to classify objects. Results: Classification accuracies of up to 96.49% were achieved for the identification of wear particles. Particle characteristics such as shape, size and area were estimated to generate size and volumetric distribution graphs. Discussion: The use of computer algorithms and CNN facilitates the analysis of a wider range of wear debris with complex characteristics with significantly fewer resources which results in robust size and volume distribution graphs for the estimation of the osteolytic potential of devices using functional biological activity estimates.</p

The Biological Response to Nanometre-sized Polymer Particles

Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1-1.0 µm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20 nm, 60 nm, 200 nm and 1.0 µm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNC’s). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20 nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNC’s at a concentration of 100 μm3 particles per cell after 12 and 24 hours. The micrometre-size UHMWPE wear particles (0.1-1.0 μm) and 60 nm, 200 nm and 1.0 µm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNC’s. These results indicated that particles below circa 50 nm fail to activate PBMNC’s and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages

Investigation of wear and wear particles from a UHMWPE/multi-walled carbon nanotube nanocomposite for total joint replacements

Ultra high molecular weight polyethylene (UHMWPE) has been extensively used as a bearing surface in joint prostheses. However, wear debris generated from this material has been associated with osteolysis and implant loosening. Alternative materials, such as polymer composites, have been investigated due to their exceptional mechanical properties. The goal of the present work was to investigate the wear rate, size and volume distributions, bioactivity and biocompatibility of the wear debris generated from a UHMWPE/Multi-walled carbon nanotube (MWCNT) nanocomposite material compared with conventional UHMWPE. The results showed that the addition of MWCNTs led to a significant reduction in wear rate. Specific biological activity and functional biological activity predictions showed that wear particles from the UHMWPE/MWCNT nanocomposite had a reduced osteolytic potential compared to those produced from the conventional polyethylene. In addition, clinically relevant UHMWPE/MWCNT wear particles did not show any adverse effects on the L929 fibroblast cell viability at any of the concentrations tested over time. These findings suggest that UHMWPE/MWCNT nanocomposites represent an attractive alternative for orthopaedic applications

Biological effects of cobalt-chromium nanoparticles and ions on dural fibroblasts and dural epithelial cells.

The introduction of metal-on-metal total disc replacements motivated studies to evaluate the effects of cobalt-chromium (CoCr) nanoparticles on cells of the dura mater. Porcine fibroblasts and epithelial cells isolated from the dura mater were cultured with clinically-relevant CoCr nanoparticles and the ions, generated by the particles over 24 h, at doses up to 121 μm(3)per cell. Cell viability and production of proinflammatory cytokines was assessed over 4 days. The capacity of the particles to induce oxidative stress in the cells was evaluated at 24 h. The CoCr particles and their ions significantly reduced the viability of the dural epithelial cells in a dose-dependent manner but not the fibroblasts. Both cell types secreted IL-8 in response to particle exposure at doses of 60.5 μm(3) (epithelial cells) and 121 μm(3) (fibroblasts, epithelial cells) per cell. No significant release of IL-6 was observed in both cell types at any dose. Reactive oxygen species were induced in both cell types at 50 μm(3) per cell after 24 h exposure. The data suggested novel differences in the resistance of the dural epithelial cells and fibroblasts to CoCr nanoparticle/ion toxicity and demonstrated the inflammatory potential of the particles. The data contributes to a greater understanding of the potential biological consequences of the use of metal-on-metal total disc prostheses

Developing Novel Fabrication and Optimisation Strategies on Aggregation-Induced Emission Nanoprobe/Polyvinyl Alcohol Hydrogels for Bio-Applications

The current study describes a new technology, effective for readily preparing a fluorescent (FL) nanoprobe-based on hyperbranched polymer (HB) and aggregation-induced emission (AIE) fluorogen with high brightness to ultimately develop FL hydrogels. We prepared the AIE nanoprobe using a microfluidic platform to mix hyperbranched polymers (HB, generations 2, 3, and 4) with AIE (TPE-2BA) under shear stress and different rotation speeds (0&ndash;5 K RPM) and explored the FL properties of the AIE nanoprobe. Our results reveal that the use of HB generation 4 exhibits 30-times higher FL intensity compared to the AIE alone and is significantly brighter and more stable compared to those that are prepared using HB generations 3 and 2. In contrast to traditional methods, which are expensive and time-consuming and involve polymerization and post-functionalization to develop FL hyperbranched molecules, our proposed method offers a one-step method to prepare an AIE-HB nanoprobe with excellent FL characteristics. We employed the nanoprobe to fabricate fluorescent injectable bioadhesive gel and a hydrogel microchip based on polyvinyl alcohol (PVA). The addition of borax (50 mM) to the PVA + AIE nanoprobe results in the development of an injectable bioadhesive fluorescent gel with the ability to control AIEgen release for 300 min. When borax concentration increases two times (100 mM), the adhesion stress is more than two times bigger (7.1 mN/mm2) compared to that of gel alone (3.4 mN/mm2). Excellent dimensional stability and cell viability of the fluorescent microchip, along with its enhanced mechanical properties, proposes its potential applications in mechanobiology and understanding the impact of microstructure in cell studies

The Effect of Anterior-Posterior Shear on the Wear of CHARITÉ Total Disc Replacement

STUDY DESIGN: An in-vitro study of the wear rates of the Charité lumbar total disc replacement. OBJECTIVE: To investigate the effect of anterior-posterior shear on the in-vitro wear rates of the Charité lumbar total disc replacement. SUMMARY OF BACKGROUND DATA: Current standards prescribe only 4 degree of freedom (DOF) inputs for evaluating the in-vitro wear of total disc replacements, despite the functional spinal unit incorporating 6DOF. Anterior-posterior shear has been highlighted as a significant load, particularly in the lumbar spine. A previous study investigated the effect of an anterior-posterior shear on the ProDisc-L, finding that wear rates were not significantly different from 4DOF wear tests. METHODS: 6 Charité lumbar discs were mounted in a 5 active DOF spine wear simulator and tested under 4DOF (ISO18192) conditions. 6 further Charité lumbar discs were tested under 5DOF conditions, consisting of 4DOF conditions plus an anterior-posterior shear displacement of +2/-1.5mm. The displacement was decreased and then increased by a factor of 2, to investigate the effect of the magnitude of displacement. µCT scans were taken of the discs before and after wear testing, and the height loss of the discs calculated. These were compared to the same measurements taken from explanted Charite discs, µCT scanned at another institution. RESULTS: 4DOF wear rates (12.2±1.0mg/MC) were not significantly different from 4DOF tests on the ProDisc-L. Wear rates were significantly increased (p<0.01) for ‘standard’ 5DOF conditions (22.3±2.0 mg/MC), decreased 5DOF (24.3±4.9 mg/MC) and increased 5DOF (29.1±7.6mg/MC). The height loss of the explants and in-vitro tested discs were not significantly different (p>0.05). CONCLUSION: The addition of anterior-posterior shear to wear testing inputs of the Charité lumbar total disc replacement increases the wear rate significantly, which is in direct contrast to the previous 5DOF testing on the ProDisc. This study highlights the importance of clinically relevant testing regimens, and that test inputs may be different for dissimilar design philosophies