Assesment [sic] of cement augmentation and screw trajectory on pedicle screw fixation in osteoporotic vertebrae

Internal fixation of osteoporotic spines for fracture or deformity is currently difficult, owing to failure at the bone- implant interface. This study aims to ascertain whether pedicle screw trajectory and pedicle cortex retention can independently significantly affect fixation strength in osteoporotic vertebrae."MU Grant #00029187

Characterization of the dorsal ulnar corner in distal radius fractures : implication for surgical decision making

Poster presented at the 2017 Health Sciences Research Day which was organized and sponsored by the University of Missouri School of Medicine Research Council and held on November 9, 2017.Conclusions: 3D segmentation software is effective in producing 3D distal radius fracture models that can be used for analysis. The study demonstrated a pattern in dorsal ulnar corner fragment shape, though the study population size should be increased to improve the power of the results. The data will improve understanding of the morphology and size of the dorsal ulnar corner fracture fragment, which is critical to understanding the optimal method of operative fixation. This information will also lead to development of more accurate intra-articularfracture models for biomechanical studies

Evolution of reproductive development in the volvocine algae

The evolution of multicellularity, the separation of germline cells from sterile somatic cells, and the generation of a male–female dichotomy are certainly among the greatest innovations of eukaryotes. Remarkably, phylogenetic analysis suggests that the shift from simple to complex, differentiated multicellularity was not a unique progression in the evolution of life, but in fact a quite frequent event. The spheroidal green alga Volvox and its close relatives, the volvocine algae, span the full range of organizational complexity, from unicellular and colonial genera to multicellular genera with a full germ–soma division of labor and male–female dichotomy; thus, these algae are ideal model organisms for addressing fundamental issues related to the transition to multicellularity and for discovering universal rules that characterize this transition. Of all living species, Volvox carteri represents the simplest version of an immortal germline producing specialized somatic cells. This cellular specialization involved the emergence of mortality and the production of the first dead ancestors in the evolution of this lineage. Volvocine algae therefore exemplify the evolution of cellular cooperation from cellular autonomy. They also serve as a prime example of the evolution of complex traits by a few successive, small steps. Thus, we learn from volvocine algae that the evolutionary transition to complex, multicellular life is probably much easier to achieve than is commonly believed

Patient specific bone remodeling and finite element analysis of the lumbar spine

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on October 16, 2007)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2007.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The body of work outlined here relates generally to mechanical engineering research in the area of biomechanics. More specifically this work focuses on numerical evaluation of lumbar spine mechanics and bone reactions as they relate to patient specific computer models. Much of this work is accomplished through the use of finite element (FE) modeling. The work is driven by the desire of surgeons to answer biomechanical and physiological questions about patient response to treatment in a noninvasive way. This work is also motivated by the need of researchers to improve upon current solution techniques to the equations of bone remodeling. The objectives of this work are to develop patient specific finite element models of patient anatomy so that patient variation can be examined, adapt current bone remodeling algorithms to address the motivation of the current study, simulate bone remodeling that occurs in the facet joint post operative to spinal fusion surgery, and to evaluate vascularization effects on bone graft growth.Includes bibliographical reference

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Background: Pelvic ringecomminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. Objective: Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of boneeimplant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods: 3D relative motion across sacralerami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacralerami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4e6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05). Results: The model, protocol and 3D optical system have the ability to locate how subcatastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral iliumescrew interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation. Conclusion: Inclusion of external fixation improved resistance only to torsional loading. Translational Potential of this Article: Patients with comminuted transforaminal sacral eipsilateral rami fractures benefit from this fixation

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Background: Pelvic ring–comminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. Objective: Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of bone–implant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods: 3D relative motion across sacral–rami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacral–rami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4–6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05). Results: The model, protocol and 3D optical system have the ability to locate how sub-catastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral ilium–screw interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation. Conclusion: Inclusion of external fixation improved resistance only to torsional loading. Translational Potential of this Article: Patients with comminuted transforaminal sacral–ipsilateral rami fractures benefit from this fixation. Keywords: bone–implant failure, external fixator, fracture stabilisation, pelvic ring injury, pelvic screws, transforaminal sacral fractur

Optimising femoral-head osteochondral allograft transplantation in a preclinical model

Background/Objective: Osteochondral autografting and allografting of the femoral head have been described as treatments for avascular necrosis without segmental collapse, fracture, osteochondritis dissecans, and tumours. One long-term study reported that 80% of nonsteroid-treated patients had successful outcomes. Most data are compiled from small case reports or series. Although these results are encouraging, to the authors’ knowledge, there is no basic scientific evidence regarding optimal graft source or technique reported in the peer-reviewed literature. The objective of this study was to create a translational canine model to compare femoral-head osteochondral autografts and allografts with respect to safety and efficacy. Methods: With Institutional Animal Care and Use Committee approval, skeletally mature hound-mix dogs (n = 6) weighing >20 kg underwent aseptic surgical implantation of osteochondral grafts using a craniolateral approach to the hip, without dislocation. Three graft options were evaluated: small auto (n = 3), 6-mm-diameter autograft from the trochlear ridge of the ipsilateral knee; small allo (n = 3), 6-mm-diameter fresh (21-day storage) allograft from a size-matched canine femoral head; or large allo (n = 3), 14-mm-diameter fresh (21-day storage) allograft from a size-matched canine femoral head. Small grafts were implanted into the same femoral head of three dogs, and large grafts were implanted alone in the other three dogs. The dogs were allowed unrestricted activity in their runs, and were walked on a leash for 15 minutes 5 times/wk. The outcome measures included functional, radiographic, and arthroscopic assessments at 8 weeks, and functional, chondrocyte viability, and histologic assessments at 6 months after surgery. The pre- and postoperative data were compared for statistically significant (p 30-mm diameter) size-matched femoral-head grafts. The radiographic, quality of life, and functional assessments were captured postoperatively. Results: All grafts had >80% chondrocyte viability at the time of implantation. All grafts showed radiographic evidence for integration into host bone. Small auto and small allo showed significant (p 30 mm) was performed in the four human patients. Due to the defect size, three out of the four human patients required two large allografts at the time of implantation. At the time of this manuscript's acceptance, patient follow-up ranged from 4 months to 18 months. All human patients were full weight-bearing without an assistive device, and showed no evidence of graft failure or progressive arthrosis. Conclusion: These data provide initial translational and clinical evidence for large osteochondral allografts as a potential option for functional resurfacing of full-thickness cartilage defects of the femoral head

Characterization of the MPS I-H knock-in mouse reveals increased femoral biomechanical integrity with compromised material strength and altered bone geometry

Mucopolysaccharidosis type I (MPS I), is an autosomal recessive lysosomal storage disorder caused by a deficiency in the α-L-iduronidase enzyme, resulting in decreased enzymatic activity and accumulation of glycosaminoglycans. The disorder phenotypically manifests with increased urine glycosaminoglycan excretion, facial dysmorphology, neuropathology, cardiac manifestations, and bone deformities. While the development of new treatment strategies have shown promise in attenuating many symptoms associated with the disorder, the bone phenotype remains unresponsive. The aim of this study was to investigate and further characterize the skeletal manifestations of the Idua-W392X knock-in mouse model, which carries a nonsense mutation corresponding to the IDUA-W402X mutation found in Hurler syndrome (MPS I-H) patients. μCT analysis of the microarchitecture demonstrated increased cortical thickness, trabecular number, and trabecular connectivity along with decreased trabecular separation in the tibiae of female homozygous Idua-W392X knock-in (IDUA−/−) mice, and increased cortical thickness in male IDUA−/− tibiae. Cortical density, as determined by μCT, and bone mineral density distribution, as determined by quantitative backscattered microscopy, were equivalent in IDUA−/− and wildtype (Wt) bone. However, tibial porosity was increased in IDUA−/− cortical bone. Raman spectroscopy results indicated that tibiae from female IDUA−/− had decreased phosphate to matrix ratios and increased carbonate to phosphate ratios compared to Wt female tibiae, whereas these ratios remained equivalent in male IDUA−/− and Wt tibiae. Femora demonstrated altered geometry and upon torsional loading to failure analysis, female IDUA−/− mouse femora exhibited increased torsional ultimate strength, with a decrease in material strength relative to Wt littermates. Taken together, these findings suggest that the IDUA−/− mutation results in increased bone torsional strength by altering the overall bone geometry and the microarchitecture which may be a compensatory response to increased porosity, reduced bone tensile strength and altered physiochemical composition