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Biomechanical understanding of forces and moments required for surgery

Better understanding tissue behaviour during surgical procedures will open the door to improved knowledge of underlying pathologies and will foster the conception of new diagnostic or treatment methods. For example, traditional tissue testing is performed on uniaxial, biaxial, or uniaxial torque testing equipment. However, surgeons do not operate along one or two axes or torques. Therefore, more advanced measuring methods have the potential to improve mechanical modeling. ATI (North Carolina, USA) has developed 6-axis Force/Torque Sensors to measure forces and torques ranging from 0.002N/0.007Nm to 88kN/8kNm. Initial work shows how these devices can be used to measure all the forces and torques present during a surgical step.

In addition, biomechanical tests for new equipment or surgical tools will be conducted by the lab. This will allow us to test current implants/surgical tools to better understand what mechanical loads they can withstand in order to better understand when and why they fail in vivo. An example is proximal junction kyphosis in spine surgery and associated rod breakage or pedicle screw pull-out. The capabilities of running such tests will allow us to design and test innovative surgical tools and equipment but also allow for some industry funded tests as another source of funding.
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VR/AR surgical simulation

The conventional surgical technique of 鈥渟ee one, do one鈥� has various ethical, cost, and time concerns, as it entails training on live patients. The conventional surgical training systems, i.e. on-patient or cadavers, come with ethical and cost issues that limit the residents in their ability to improve their skills in complicated techniques. Therefore, teaching hospitals are moving towards inanimate training systems using synthetic materials and virtual reality (VR), where the latter is preferred for its ability to provide repetitive and intensive training without requiring replacements.

Presently, there is a lack of understanding about the mechanical behavior of the tissues of the spine during a surgery. Using this knowledge, realistic mechanical characterization of the surgery can be developed for an interactive VR/AR system. Understanding the mechanics of the biological tissue and their response to manipulation by surgical tools will be used towards the development of a finite element model of the operating area in the virtual environment.

These models will be integrated into a novel, interactive virtual reality training system, which allow surgical residents to practice intensively and repetitively without risking lives of patients. Using parallel processing, a realistic interaction and manipulation of the operating area will be developed. This VR/AR training system will utilize physics driven haptics to provide an immersive experience to the users.
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Exploration of spine stability

The spine is perhaps the most complex physiological mechanical system in our bodies. Research progress in simulation capabilities now enables biomedical engineers to more accurately explore how the spine functions and, consequently, how it fails. Understanding the mechanisms that contribute to spinal stability, or lack thereof, is the global theme of the proposed research program. Spinal disorders and associated back pain currently represent an epidemic hindering productivity and creating a massive economic burden to developed nations. The presentation of a spinal disorder, mechanically, represents a flawed stability mechanism. This fundamental research seeks to evaluate and quantify the role of passive tissues in spine stability.

Other projects and anatomical models will also be created and used as needed for specific projects. These can include modeling upper and lower extremities before and after surgical reconstructive procedures. These models can then be linked to other research such as gate analysis to predict specific patient outcomes after surgery.
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State of art in silico simulation

In silico (numerical models) simulation is becoming very popular in the age of digital health. Furthermore, regulatory bodies such as the FDA are beginning to accept in silico data at par to ex vivo and in vivo data. This rapid change over the last 10 years opens the door for validated numerical models of the human body, such as that of the Spine by Prof. Driscoll, to be leveraged for objective research and medical device developments. The ORL serves as a compliment to these numerical models in their strive towards clinical validation and thus augment confidence of use.

AR assisted surgery

To create an augmented reality overlay of spine anatomy (soft and hard tissues) workflow for patient specific anatomy. The application could be used for improved surgical training when using analogue surgical models or cadavers. Alternatively, the technology can be leveraged as a medical device (class II, FDA) for use in the operating room with live patients in order to provide safer implant placement. This is of utmost importance in pedicle screw placement when a misplaced screw can lead to catastrophic outcomes for patients.
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Non-invasive characterization of soft tissues and intra-muscular or intra-abdominal pressure

The human abdomen not only contains and protects organs vital to life, but is responsible for the structure and support of the spine. Spinal support, or stability, is made possible by both the activation of abdominal muscles and increase in pressure contained in the abdominal compartment (or, intra-abdominal pressure (IAP)). Given the demands of this anatomical region, abdominal conditions can be frequent and severe, including intra-abdominal hypertension and low back pain. Two physiological properties associated with abdominal conditions are IAP and abdominal compliance (Cab) where Cab, clinically, is the measure of ease of abdominal expansion. Both properties are directly affected by a subject鈥檚 intra-abdominal volume (IAV), the volume of the abdominal compartment at a known time or position and abdominal wall (AW) elasticity. Despite the prevalence of abdominal complications, and the known roles of IAP and Cab, accepted measurement methods for both properties remain invasive or unreliable. Our lab would attempt to quantify these values in a novel non-invasive manner to better understand their role in spinal stability and pathology.
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Improved patient specific fixation after large bony resection

The goal is to redesign bone cement in order to be able to create customizable, patient specific constructs that can be created in a matter of minutes in the operating room. The secondary advantage is to use material that has a proven track record to decrease infection and provide temporary fixation to improve initial post-operative patient functional outcome. To achieve this, we intend to modify existing bone cement. This can be done by using common civil engineering cement techniques in order to strengthen tensile and compressive strength of bone cement. In addition, 3D-printed customizable molds would be used to provide patient specific temporary implants. This new cement will be tested to assess feasibility and possible implementation for use in large bony resection done for cancer. For example, in a hemipelvectomy, the standard of care remains to leave the leg flail due to lack of appropriate implants to reduce infection in these large cases. This means patients being bed ridden for longer periods of time and in turn means a very high complication rate, as high as 90% in the literature. A simple improvement in cement biomechanical properties can address this shortcoming and allow for less infection, customisable implants, and for early mobilisation for these patients.

Low back pain is a global age-related health听problem that is directly associated to intervertebral disc (IVD) degeneration. It is experienced by ~ 80% of individuals at some time in their life and is globally the number one cause of years lived with disability. Despite its prevalence, little is known about the cellular and molecular mechanisms leading to painful IVD degeneration, leaving surgical removal and vertebral fusion in end-stage disease as the most common treatment. The personal costs in reduced quality of life and the economic cost to healthcare systems are enormous and exceeds $100 billion per year in the US alone. There is a direct link between load, degeneration and pain in human IVDs, but the cellular and molecular responses to mechanical injury are not well established. Key methodology has been developed at the ORL facilitating studies of load injury on isolated disc cells and intact non-degenerate human IVDs. A Bioreactor system for long-term culture of intact IVDs under defined axial loading conditions was designed and fabricated. IVDs are cultured under cyclic physiological loading with maintenance of disc height and cell viability. The system can be used to model physiological or pathophysiological loading and evaluate metabolically responsiveness to load. The system has also been used to demonstrate the feasibility of tissue repair strategies such as cell supplementation and of novel therapeutic interventions for degenerative and painful IVD degeneration. We have, through a unique collaboration with Transplant Quebec, collected more than 200 lumbar spines over the past decade, providing clinically relevant tissue for the studies. Our culture model is the closest system available to mimic the human in vivo condition and provides a unique opportunity to evaluate and compare treated and untreated IVDs from the same individual, avoiding confounding results related to lifestyle and genetics.

Our vision in the is the globalization of safe surgery through the utilization of simulation and artificial intelligence. In surgery, technical skills are of paramount importance where less-skilled performance can result in poor patient outcomes. Most surgical skills learning occurs in immersive operating room environments, where the staff surgeon continuously evaluates trainee performance, provides coaching to improve skills and error mitigation. The shift towards a competency-based approach in surgery necessitates the development of novel platforms, including the application of advanced virtual reality and artificial intelligence technologies to provide objective feedback and augment components of the formative assessment roles of expert operative room instructors. Our group has assisted in the development of a number of high-fidelity virtual reality simulators with haptic feedback and created complex realistic virtual reality cranial and spinal scenarios to aid learners master operative skills. These virtual reality platforms generate extensive datasets and artificial intelligence/machine learning systems were used to uncover new features and group participants according to technical ability. A robust artificial neural network was designed to classify 3 groups of participants based on expertise with 83.3% accuracy and uncover previously unrecognized expertise composites along with outlining the relative weights of specific metrics for a spine procedure. To provide competency-based frameworks to help assess and quantitate complex psychomotor technical skills, advanced virtual reality platforms such as the Virtual Operative Assistant, powered by artificial intelligence, were created. These frameworks are transparent and based on quantifiable objective metrics. Whether creating expert performance benchmarks to which learner鈥檚 scores were compared or using artificial intelligent algorithms to classify participants into pre-defined categories, data were analyzed at the completion of the surgical event in the post-hoc manner. Limitations of these platforms are the provision of classification and performance data following task completion and therefore the inability to improve performance during the task. Real-life operative feedback occurs in real-time and is relevant to the precise action being performed. We are developing deep learning artificial intelligence applications to continuously monitor bimanual technical skills during operative performance. These intelligent tutoring systems reproduce the roles of expert instructors by providing continuous assessment, intelligent feedback to improve technical performance and mitigate error.

As we navigate through these unprecedented times, the full impact of COVID-19 on surgical education programs is yet to be ascertained. With continued research, increased development, and dissemination of intelligent tutoring systems, we can be better prepared for ever evolving future challenges. Our expertise in the application of artificial intelligence technology will be integrated into the multiple research and education programs in the Orthopaedic Research Laboratory.