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SPINe: Numerical and Experimental Repair strategies

Periodic Reporting for period 2 - SPINNER (SPINe: Numerical and Experimental Repair strategies)

Reporting period: 2020-01-01 to 2021-12-31

SPINNER is a doctoral training programme for Bioengineering early stage researchers (ESRs) aiming to train people in multidisciplinary aspects of spine treatments.

Back pain is an common problem with more limited solutions than limb joints. Together with other musculoskeletal disorders back pain creates a long term financial burden due to the costs to health services and social care and loss of income; 60% of people on early retirement or long term sick leave state that musculoskeletal problems are the reason. The number of patients requiring complex spine surgery is rapidly expanding, and the biomedical engineering industry needs suitably trained innovators to produce economic solutions to support healthy ageing for the people of Europe.

Therefore, the aim of SPINNER was to train bioengineers to be in a position to design the next generation of repair materials and techniques for spine surgery. SPINNER brought together partners from the biomaterials (Finceramica), implantable devices (Aesculap), and computational modelling (Ansys, Adagos, RBFMorph) industries together with orthopaedic clinicians (National Centre for Spinal Disorders, NCSD) and academic experts in cell, tissue and organ scale biomaterials and medical device testing (Universities of Sheffield and Bologna).

SPINNER had the objectives:
1) Training of orthopaedic Bioengineers able to integrate in vitro (in the laboratory), ex vivo (outside the body) and in silico (in a computer) data across scales for a holistic approach to spine reconstruction.
2) Development of bioactive, bioresorbable, mechanically competent materials for restoration of the bones of the spine – the vertebrae that could be used in a spinal fusion procedure.
3) Mechanical characterisation of implant materials and reconstructed spines using laboratory and computational modelling techniques.
4) Integrated, user-friendly, computer models of the mechanics of damaged and reconstructed spinal segments that can be used for predictive design, patient specific analysis and surgical navigation.

Despite COVID-19, SPINNER was completed on time, all researchers completed their 36 months training and have collected data for a PhD thesis. The researchers attended multidisciplinary training events where specialists in biomaterials, biomechanics and computer modelling described their methodologies. Industry representatives and clinicians were involved throughout and led to real-world examples of spine repair being used for the research. Our key objectives were achieved and SPINNER researchers work will lead to improved surgical techniques using multidisciplinary analysis of the materials and mechanics of the entire system in a holistic way.
This was achieved by the six ESR projects:

ESR1 developed multisubstituted hydroxyapatite (SrMgHA) and developed a composite material that could be 3D printed into the shape required to fit a spinal cage and act as a bone graft substitute, this material was demonstrated to be biocompatible and to support bone-forming cells. This result indicates it can be an advanced implantable material for bone repair.

ESR2 collaborated in the development of the hydroxyapatite materials and then devised methods to coat these on commonly used spinal implant materials such as polymers (PEEK) and metals (titanium) used in spinal cages. The coating was demonstrated to be biocompatible and to support bone-forming cells. This result indicates it can be an advanced method to create better bone conducting materials for spine repair.

ESR3 developed in vitro methods to quantify the mechanical competence of natural, diseased, and treated spine segments. She compared two different types of surgery; nucleotomy - taking out the central portion of the cartilage disc that separates the vertebrae and discoplasty - reinforcing the damages disc with bone cement . The results showed that nucleotomy decreases disc height whereas discoplasty restored height, did not restrict range of motion and decreased average strain over the disc compared to nucleotomy.

ESR4 developed a protocol for the measurement of spinal movement in patients and captured these measurements for patients before and after spine surgery, as well as for healthy control subjects. These measurements were used to analysis the stability and range of motion of the spine to determine how successful a surgery was.

ESR5 developed a subject specific finite element model of spinal fixation and automatic insertion of screws in the vertebral body. This work showed that the diameter of the screw should be optimised for each patient as it has a large impact on the stress in the screw. The size and orientation of screws within the vertebra could be optimised using a computational technique termed reduced order modelling for a large number of inputs.

ESR6 developed machine learning computational techniques called ‘deep learning’ and ‘statistical shape analysis’ for the calculation of stresses in vertebrae, thus drastically reducing the time of the computer predictions compared with time-consuming biomechanical simulations. The artificial neural network approach was able to reduce the computational cost to 1% of the equivalent older style of computer model – finite element analysis.

All ESRs attended training events to provide the background to their project and enable them to understand each other’s work. These events have provided the ESRs with the background, knowledge, insight and skills to engage with their PhD research projects. All of the

ESRs have either already completed or are writing up a PhD thesis based on the results that gained during the SPINNER project.
Despite dissemination being challenging during the COVID, all ESRs presented at international conferences. Most notably 4 ESRs presented virtually and the European Society of Biomechanics annual meeting. 4 ESRs presented at BioMedEng21. 2 ESRs presented their work remotely at the Orthopaedic Research Society Annual meeting. ESR 5 has published in ‘Frontiers in Bioengineering and Biotechnology’ as well as two articles aimed at industry in ‘Robotics and Automation’ and ‘Design news’. The final showcase was held online, hosted by NCSD.
The key outputs are:
Biomaterials could provide improved materials for spine surgery, enhancing the patients’ prognosis.
Biomechanics will provide insights into the effects of spine disease and its treatment.
In silico modelling will assist spine surgeons in planning spine surgery, through the real-time evaluation of possible interventions.

To improve orthopaedic biomaterials for spine repair different compositions of hydroxyapatite (based on the calcium phosphate found in bone) were used to create a polymer composite that can be used instead of bone graft as a filler material to encourage bone growth and a coating that can be placed on metal spinal cages to improve spinal fusion surgeries. To better understand the biomechanics of spine repair, studies were undertaken on the effects of different surgeries on range-of-motion. To improve how we construct models of spine surgery, enabling the use of patient-specific, large data sets computer models using machine learning methods were developed.
Spinner Fellows watch telecast of live spine surgery at Istituto Ortopedico Rizzoli, Bologna, Italy.
The Spinner Fellows at their first training event host by Aesculap AG, Tuttlingen, Germany.
Spinner Fellows and Supervisors apply spinal fixations to cervical and lumbar spines, in Aesculap.