X23D-Intraoperative 3D Lumbar Spine Shape Reconstruction Based on Sparse Multi-View X-ray Data

Visual assessment based on intraoperative 2D X-rays remains the predominant aid for intraoperative decision-making, surgical guidance, and error prevention. However, correctly assessing the 3D shape of complex anatomies, such as the spine, based on planar fluoroscopic images remains a challenge even for experienced surgeons. This work proposes a novel deep learning-based method to intraoperatively estimate the 3D shape of patients' lumbar vertebrae directly from sparse, multi-view X-ray data. High-quality and accurate 3D reconstructions were achieved with a learned multi-view stereo machine approach capable of incorporating the X-ray calibration parameters in the neural network. This strategy allowed a priori knowledge of the spinal shape to be acquired while preserving patient specificity and achieving a higher accuracy compared to the state of the art. Our method was trained and evaluated on 17,420 fluoroscopy images that were digitally reconstructed from the public CTSpine1K dataset. As evaluated by unseen data, we achieved an 88% average F1 score and a 71% surface score. Furthermore, by utilizing the calibration parameters of the input X-rays, our method outperformed a counterpart method in the state of the art by 22% in terms of surface score. This increase in accuracy opens new possibilities for surgical navigation and intraoperative decision-making solely based on intraoperative data, especially in surgical applications where the acquisition of 3D image data is not part of the standard clinical workflow

Low Back Pain Pathogenesis and Treatment

Low back pain is a common disorder which affects the lumbar spine, and is associated with substantial morbidity for about 80% of the general population at some stages during their lives. Although low back pain usually is a self-limiting disorder that improves spontaneously over time, the etiology of low back pain is generally unknown and the diagnostic label, "non-specific low back pain", is frequently given. This book contains reviews and original articles with emphasis on pathogenesis and treatment of low back pain except for the rehabilitative aspect. Consisting of three sections, the first section of the book has a focus on pathogenesis of low back pain, while the second and third sections are on the treatment including conservative and surgical procedure, respectively

Short and Long Term Immobilization on the Lumbar Spinal Joints: An Experimental Study Using Large Animal Model

Low back pain (LBP) is a common, widespread social and economic problem. Degenerative disc disease has been considered as a main risk factor for the LBP. In order to develop safe, effective and cost-efficient treatments, it is important to explore the pathomechanisms of this disease. In vivo animal models have an irreplaceable role in detecting long-term reactions to environmental factors, biology or biomechanical risk factors, and preclinical evaluation of therapeutics. Large animal models, due to their similarity in cellular populations, anatomy and biomechanics, are more closely comparable to the human intervertebral disc than smaller animal models. The major goal of current thesis was characterizing the effect of short and long term immobilization on the magnetic resonance imaging, radiological, histological and biomechanical characteristics of the in vivo ovine lumbar spine joints. To achieve this target, four experimental projects were performed. In the first experimental portion, a three-dimension motion capture system was set up and validated. A reliable method of the spinal kinematic analysis was established. The second experimental portion evaluated the biomechanical aspect of a synthetic biomimetic spine model with a validated spinal biomechanical test system combined with the motion capture system set up in the first study. This established the whole system applicability to the specific goal of examining spinal biomechanics. The third experimental chapter is an in vitro ovine biomechanical study. The purpose of this study was to characterize the effect of loading and soaking conditions on the spinal segment biomechanical property. Results indicated the biomechanics of spinal samples with hydration and dehydration discs differ considerably. Thus, the suitable pretest conditions need to be considered during in vitro spinal biomechanical test. The fourth experimental portion was the in vivo ovine model study. The aim of this chapter was evaluate the effect of the short and long term immobilization on the ovine lumbar spinal joints. The posterior pedicle screw instrumentation was applied on skeletally mature sheep lumbar spine. The immobilized level and adjacent levels spinal joints were evaluated at 0, 6 and 26 weeks. Results demonstrated the both short and long term immobilization can induce spinal joint degeneration on sheep model. This work presents a novel degenerative disc model without the need for annulus violation or chemical treatmen

Biomechanical investigation of the factors related to pedicle screw fixation strength

Spinal pathologies or injuries can severely compromise the quality of life for the patients. The surgical intervention is often performed using internal fixation devices. Fixation with pedicle screws is a well-established method providing spinal stability and deformity correction. However, reported rates of fixation failure because of screw loosening have become a major concern, especially with the appearance of new and more powerful surgical techniques. Numerous experimental studies have been devoted to pedicle screw fixation strength evaluation. The evaluation methods are commonly including preoperative measurements of bone mineral density, screw insertional torque measurement and pullout tests. Bone mineral density measurement gives only to some extent an estimation of the pedicle screw fixation strength. Several studies indicated that the screw insertional torque measurement can provide predictive information on the fixation strength. However, the latter was not confirmed by other studies. This controversy illustrates the need for improving the understanding of factors related to pedicle screw fixation strength. In addition, there is a need for better understanding the mechanisms of pedicle screw loosening leading to failure and their effects on the fixation strength. The main objective of this doctoral thesis was to improve the understanding on the mechanisms of pedicle screw loosening and the factors related to pedicle screw fixation strength. This objective is related to two hypotheses: 1) the indentation force measured while performing the pilot hole and the torque observed during screw insertion are related to the screw pullout force and stiffness; 2) cyclic bending load (toggling) on pedicle screw in craniocaudal (CC) and mediolateral (ML) directions loosens the screw and affects the pullout force and stiffness. Three specific objectives were defined to verify the hypotheses using two experimental protocols. The first specific objective was to develop and validate tools measuring the indentation force while performing the pilot hole and the insertional torque during pedicle screw insertion. The second objective was to compare the screw loosening mechanisms through toggling in different modes and evaluate their effects on pedicle screw pullout force and stiffness. Finally, the third objective was to establish the relationships between the indentation force, the insertional torque and the screw pullout force and stiffness. The first protocol was performed on synthetic bone surrogates mainly to explore the first specific objective. Furthermore, to account for the effect of various bone densities and toggling modes on pullout force and stiffness, pedicle screw were pulled out with and without toggling from synthetic bone surrogates of three different densities. With five repetitions, a total of 36 trials have been completed. Finally, potential relationships between the indentation force and the insertional torque with the pullout force and stiffness were explored. The second protocol was performed on porcine vertebrae to investigate the second and the third specific objectives. As the second specific objective, three toggling modes (CC, ML and no toggling (NT)) were performed on porcine lumbar vertebrae ranging from L1 to L3. The screws were then submitted to axial pullout test. A complete design of experiment with two factors and three levels (32 = 9 trials) was used to investigate on the main effect of toggling mode and vertebral level on screw pullout force and stiffness, as well as their quadratic interactions. With five repetitions, a total of 54 trials were performed on 27 isolated vertebrae, using both pedicles. Finally, potential relationships were investigated between the indentation force while performing a pilot hole, the insertional torque during screw insertion, and the pullout force and stiffness with and without toggling. The results of the first protocol suggest that screw toggling significantly affects the pullout force (P = 0.01) and stiffness (P < 0.0001). A higher pullout force and stiffness was demonstrated for higher density without toggling. The effect of density was higher than the effect of toggling on pullout force. The indentation force while performing the pilot hole was significantly correlated to pullout force and stiffness (r = 0.99, P < 0.0001 and r = 0.92, P < 0.0001 respectively). Strong correlations were also shown between the insertional torque during screw insertion and the pedicle screw pullout force and stiffness (r = 0.98, P < 0.0001 and r = 0.91, P < 0.0001 respectively). The study on porcine vertebrae showed that screw toggling significantly affects the pullout force (P = 0.0004) and stiffness (P 0.85, P < 0.0001). For pullout force without toggling BMD and pedicle area were the main contributing factors to the regression model. For the stiffness with and without toggling, the indentation force was the single best factor with highest contribution to the regression model. In conclusion, pedicle screw toggling significantly affects the pedicle screw pullout force and stiffness. Screw toggling, in particular CC toggling, should be considered in the biomechanical evaluation of pedicle screw fixation strength. Furthermore, the contribution of toggling was more important on the stiffness than the pullout force. The effect of vertebral level should be considered in determining the fixation strength. The developed instruments and methods for indentation force measurement during pilot hole creation and insertional torque measurement during screw insertion were reproducible, and provide valuable data to estimate pedicle screw pullout force and stiffness. The relationship between the pilot hole indentation force and screw insertional torque, and the screw pullout force and stiffness are a affected by the toggling mode. Indentation force and insertional torque measurements, together with BMD measurement, are recommended for a better estimation of pedicle screw fixation strength after CC toggling

The biomechanics of lumbar total disc replacement impingement: In silico Investigations of polyethylene damage modes of lumbar total disc replacement

Ph.D., Biomedical Engineering -- Drexel University, 201

The Influence of Design Features in the Biomechanical Performance of a Fixator for the Lumbar Spine

PhDSpinal fixation systems using pedicular screws have gained popularity in manging the damaged spine. However, the loading to which individual components of a fixator are exposed are largely unknown. This thesis describes the use of a Corpectomy injury model to investigate the mechanical response of a commercial internal spinal fixator and the resultant loads acting on its rods and screws, under four separatelo ading regimens. The fixator was instrumentedw ith strain gaugesa nd tested using specially designed jigs. The results were then compared to theoretical models and any differences highlighted. An evaluation was also performed on a range of transpedicular screw designs under tensile loads. An increase in the tightening torque of the fixator clamps, ranging from 5 to 15Nm, and the inclusion of transverse elements across its vertical rods produced a combined increase in overall torsional rigidity of 89%. However, no such changes were found under axial compression and both simulated flexion and extension tests. The relative ineffectivenesso f the transversee lementsu nder sagittal loads was probably due to their spatial relationship with the fixator. The results from the instrumented fixator indicated several load response pathways, as predicted by the theoretical analysis. These pathways were influenced by several factors including, the screw angulation, the boundary conditions of the test and the addition of the transverse elements. Clamp design was critical in minimising rotational slippage of both screws and transverse elements. The results from the instrumented fixator revealed that the transpedicular screws were exposed to complex loads under each of the tests. Under tensile loads, both the increasei n screw insertion depth and a decreasein screw pitch were found to be the important parameters which affect screw performance. Analysis showed the state of stress and strain along the thread was the overriding factor in the tensile performance of these screws. This work hase mphasisedth e importance of a full biornechanicale valuation of any future designs of spinal fixators

Determination and Comparison of In Vivo Forces and Torques in Normal and Degenerative Lumbar Spines

In vivo motions of normal and degenerative lumbar spine patients performing extension/flexion were obtained using video fluoroscopy. 3-D models of each patient’s vertebrae were registered to the 2-D fluoroscopy images using a process developed at Rocky Mountain Musculoskeletal Research Laboratory. Temporal equations representing the motions were input into a math model and the forces at the contact point between vertebral levels and the body torques between the vertebrae were the output. The vertical forces in the normal and degenerative patients were similar and ranged from 0.35-0.42 times the body weight of the patient. The maximum torques were higher in the degenerative patient than in the normal patient. The maximum torques between L4 and L5 were 11.1 N*m in the degenerative patient and 9.72 N*m in the normal patient. At L3/L4, the maximum torque was 10.3 N*m in the degenerative and 9.03 N*m in the normal patient. The maximum torques in the degenerative patient were also higher than in the normal patient at the L2/L3 and L1/L2 levels. Left untreated these higher torques could cause deterioration of other levels as the spine tries to compensate for existing degenerative levels. This model will lead to a better understanding of the lumbar spine and could aid in treating lower back pain and in the design of spinal prostheses

Mechanical and electromechanical characterization of a novel composite cellular solid for orthopaedic applications

This document presents investigations concerning the feasibility of manufacturing a novel active composite cellular structure to be used in surgical applications such as spinal fusion. The development of a biomimetic spinal fusion implant was motivated by two main factors. The population of patients whose metabolic conditions jeopardize the success of this surgical operation keeps increasing. Current implants and techniques present financial, technical, and health drawbacks. The new medical device would feature enhanced mechanical and electromechanical properties that would overcome these issues and could accelerate bone healing. A simple one-dimensional piezoelectric re-entrant structure was created from piezoceramic plates positioned between metallic bowtie open cells. Various sizes of this structure were prepared by hand and by a solid free-form process. These ductile cellular solids were tested to verify if they presented a nonlinear mechanical behavior at small strains along with mechanical parameters and an electromechanical behavior that could be tailored for orthopaedic applications. The tensile strength of a gradual composition material used as an interface between the metallic and ceramic elements of the structure was also evaluated. Despite the small number of specimens and limitations in the current manufacturing process, the investigations showed that the mechanical and electromechanical properties of the re-entrant structure can be controlled and tailored via their relative density. Also, the gradual composition interfacing material presented a linear change in tensile strength that could eliminate the problems of stress concentration in the structure. This work provides base data for future finite element analyses of such and evolved versions of the piezoelectric re-entrant structure

Augmented Reality: Mapping Methods and Tools for Enhancing the Human Role in Healthcare HMI

Background: Augmented Reality (AR) represents an innovative technology to improve data visualization and strengthen the human perception. Among Human–Machine Interaction (HMI), medicine can benefit most from the adoption of these digital technologies. In this perspective, the literature on orthopedic surgery techniques based on AR was evaluated, focusing on identifying the limitations and challenges of AR-based healthcare applications, to support the research and the development of further studies. Methods: Studies published from January 2018 to December 2021 were analyzed after a comprehensive search on PubMed, Google Scholar, Scopus, IEEE Xplore, Science Direct, and Wiley Online Library databases. In order to improve the review reporting, the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were used. Results: Authors selected sixty-two articles meeting the inclusion criteria, which were categorized according to the purpose of the study (intraoperative, training, rehabilitation) and according to the surgical procedure used. Conclusions: AR has the potential to improve orthopedic training and practice by providing an increasingly human-centered clinical approach. Further research can be addressed by this review to cover problems related to hardware limitations, lack of accurate registration and tracking systems, and absence of security protocols