No description available.

Rates of lumbar fusion surgery have been increasing with an estimated 192,000 procedures performed annually. However, satisfactory outcomes of lumbar fusion vary considerably and often emphasize technical success, such as arthrodesis, rather than Ill functional and quality of life outcomes. Interbody cage fusion was recently developed and touted as a superior alternative to existing lumbar fusion procedures. There is, however, a paucity of research to support these claims, particularly with regards to functional and quality of life outcomes. Moreover, predictive correlates of outcomes for interbody cage fusion have not been given adequate attention in the literature. The aims of this study were to characterize patients undergoing this new procedure, examine functional and multidimensional outcomes, and investigate the predictive efficacy of presurgical variables. A retrospective cohort research design was employed and entailed medical record reviews for presurgical data and telephone outcome surveys at least 18 months following surgery. Seventy-three patients who had undergone lumbar interbody cage fusion were identified from the private practice of an orthopedic surgeon and the Workers' Compensation Fund of Utah. Presurgical variables coded for analysis included age at the time of surgery, severity rating of presurgical spinal pathology, smoking tobacco, depression, and pursuing litigation at the time of surgery. Of the total sample, 56 patients (76.7%) completed outcome surveys that assessed patient satisfaction, back-specific functioning, disability status, and physical and mental health functioning. While arthrodesis was achieved for most patients (84%), almost half were dissatisfied with their current back condition. Outcomes regarding disability and functioning were mixed. Arthrodesis was only moderately associated with better outcome and for a quite limited set of measure s. Three of the five presurgical variables (tobacco use, depression, and litigation) were consistently predictive of patient outcomes. Findings are discussed and compared to existing data on lumbar fusion procedures , and clinical implications for improved patient selection and possible interventions are highlighted. Consideration is given to the limitations of this study, such as retrospective design, no matched controls , and sample size. Directions for future research are suggested.

No description available.

M.Ing. (Mechanical Engineering) / A stand-alone anterior lumbar interbody fusion device is used to stabilise the spine and restore the disc space height without any other instrumentation. The stand-alone anterior lumbar interbody device is fixed to the adjacent vertebrae using titanium screws. In this research an experimental and numerical investigation on the structural strength of the SASCATM stand-alone anterior lumbar interbody fusion device are presented. The outcome of the investigation will be used as part of the device validation documentation necessary for market approval. The SASCATM device is manufactured from PEEK (a high strength polymer). Tensile and compressive testing was conducted to determine the appropriate mechanical properties of PEEK. The structural integrity of the SASCA device was evaluated by conducting full scale compression testing on a limited number of different design revisions. Comparisons as regards to their loaddisplacement behaviour were made. All specimens were visually inspected. The Finite Element Analysis (FEA) method was used in the numerical investigation of the SASCATM stand-alone anterior lumbar interbody device. Three studies were conducted. The first study aimed at comparing the full scale experimental compressive testing results with the FEA simulation. Although the desired results weren’t achieved, the model gave a fair representation of the initial region of the experimental setup in the sense that it had a similar slope. It was concluded that the nominal stress (4.1 MPa) fell within the proportional limit (35 MPa) as measured during the materials testing. The second study was aimed at determining the displacement at a worst-case load determined from the literature (2.7 kN). The study showed that the maximum Von Mises stress does not exceed the yield strength of the material. The third and final (parametric) study aimed at geometric optimisation of the cages. The motivation for the changes was based on the literature and customer suggestions for improvement. The geometric optimisation intended to show whether a desired increase in graft hole size would have an effect on the structural integrity of the device. The suggestion to move the screw holes of the threehole version closer to the center of the cage was also assessed. It was shown that enlarging the two graft holes does have an effect on the compressive strength. Higher stresses were presented in all but one case. Combining the holes also had an effect on the compressive strength. Movement of the screw holes more medially did have an impact on the compressive strength of the cages. The effect was significant. The closer the holes were to the center of the cage, the higher the Von Mises stress was. This change should therefore be considered before implementation. The results showed that different shapes and sizes of the graft holes do have an impact on the stress of this particular cage. None of the models exceeded the compressive yield strength of the material. The proposed graft hole opening design changes are therefore not warranted for the current SASCATM stand-alone anterior lumbar interbody device.

No description available.

Implants used in lumbar spinal fusion and lumbar total disc replacement procedures have improved substantially over the years, however, the opportunity remains to improve either the adjustability, durability, motion, or minimally invasive characteristics which could aid in achieving optimal surgical outcomes. It is hypothesized that the inherent advantages of compliant mechanisms specifically Deployable Euler Spiral Connectors (DESCs) and a new mechanism known as the interior contact aided rolling element (I-CORE) are well suited for each of these applications and will be explored and utilized as the basis of these proposed designs. By addressing these challenges, the research endeavors to improve patient outcomes in both lumbar fusion and lumbar disc replacement procedures and advance the field of lumbar spinal surgery. Expandable cages, ideal for minimally invasive lumbar fusion, can be implanted in a compact form and then expanded. Differences in shape, size, material, and adjustability of cages are often overlooked. A systematic review revealed that design variations, such as rectangular titanium cages with medial-lateral and vertical expansion, and those with adjustable lordosis, are linked to better patient outcomes. Deployable Euler Spiral Connectors were leveraged to create an expandable fusion cage while also including recommended features from the systematic review. Finite element analysis, benchtop mechanical testing, and validation via in vitro device insertion were performed. The design highlights the potential of compliant mechanism devices for advancing minimally invasive lumbar fusion. A new compliant mechanism called the Interior Contact-Aided Rolling Element (I-CORE) is described and modeled using the pseudo-rigid-body method. The new mechanism included two degrees of rotational freedom at a tailorable stiffness combined with tailorable vertical compressibility and a mobile center of rotation. The model is outlined and validated using FEA and benchtop mechanical testing. The model is shown to be sufficiently accurate for initial design work. A novel motion preserving spinal implant using the I-CORE mechanism is described. Prototypes were manufactured from Ti6Al4V and validated using benchtop mechanical and in vitro biomechanical testing. Properties including compressive, shear, and torsional stiffness were quantified. The device was tested for expulsion and subsidence forces, showing results comparable to current devices. In vitro testing with human cadaveric lumbar segments demonstrated that the compliant interbody device maintained robust compressive, shear, and torsional strength, closely replicating the motion quality of intact segments when properly placed.