The lumbar spine consists of five vertebrae in the lower back, and it is crucial for supporting much of the upper body’s weight and it helps facilitate various movements in the body. Intervertebral disks work as separators so that when a person moves, the bones of their vertebrae don’t rub against each other and break. Disk degeneration occurs, causing the disk to wear out and become non-functional.
The current standard care option is to perform spinal fusion which removes the degenerated disk and welds the vertebrae together, in order to diminish pain associated with the rubbing of the bones. Recently, there has been a spike in research for an artificial disk that could replace the damaged one, thereby removing the need for spinal fusion surgery. Despite the existing research, no artificial disks have produced significant clinical outcomes. Furthermore, there has not been any specific testing done on the L5-S1 disk due to the complicated nature curvature that exists in the body and the amount of shear force that it sustains. A disk that was created for the cervical spine could not be easily repurposed for the lumbar spine due to the angle and asymmetrical nature of the L5-S1 disk. Within the L5-S1 region, this intervention is most needed as there is the greatest sign of reduced signal intensity and degeneration but it also has the highest percentage of grade 3 disk degeneration. Degenerative disk disease can cause problems such as scoliosis, herniated disk, spinal stenosis or spondylolisthesis. It is most commonly found in adults over the age of 40 and some factors that increase the development of disk degeneration are acute injuries, obesity, smoking and physically demanding exercise.
Project Scope
There is a need to develop a long-term, minimally invasive treatment for patients experiencing a degenerative disk disease or injury, such as spondylolysis or a herniated disc, in order to relieve pain in the lumbar spine and restore movement and stability.
A pressing need exists for the development of a sustainable, minimally invasive treatment option for patients with degenerative disk disease or injuries such as spondylosis or a herniated disc, in order to relieve pain in the lumbar and sacral regions of the spine and thereby restore movement and stability. The designers/developers propose the following specifications for the prototype of an artificial disk, slated for delivery on the final day of class in April of 2024. Such specifications of the prototype include but are not limited to:
- Allows for the replacement of the L5-S1 spinal joint, thereby enabling adjacent spinal vertebrae to press together.
- Proper integration is ensured to prevent dislocation of the artificial disk to unintended areas of the body.
- Proper integration to maintain possible inward curves towards the spine.
- Sustains shear and translational forces further than compression.
- Allows for natural range of motion including flexion and extension in the sagittal plane, lateral bending in the frontal plane, and rotation and compression in the axial plane.
- Restricts translation and sliding of the disk beyond the normal range of motion and prevents vibration; thereby able to bear the load of the body.
- Is composed of a material that is biocompatible and possesses elastic resistance to optimally absorb a wide variety of shocks reverberating throughout the spine.
A 3D printed model will be developed thereby serving as a physical prototype. Subsequently, the project plans to adhere to comprehensive evaluations of the prototype, utilizing both finite element analysis and modeling to ensure the integrity and functionality of the product. Important to note, forms of the prototype along with its subsequent iterations, will undergo rigorous physical examinations to assess its resilience against pertinent compressive, shear and translational forces. These assessments thereby aim to validate the capacity of the prototype in congruence to physiological specification, as well as refine the design for optimal performance.
Design Specifications
- Sustain shear forces up to 700 N in the anterior-posterior direction.
- Sustain compression forces up to 2000 N in the upright (0 degrees) position.
- Sustain compression forces up to 3400 N for small trunk flexion angles (30 and 45 degrees).
- Provide six degrees of freedom and tri-planar motion.
- Thickness/height of 6.15-10.33 ± 1.0 mm with an angle of 15.28 degrees.
- Width of 55.37-58.60 ± 2.0 mm dependent on patient’s physiology.
- Anteroposterior diameter of 15.5 ± 1.5 mm depending on the age and gender status of the patient/client.
- Weight of approximately 20 ± 5 g.
- Cost of approximately $10,000.
- Plate adherence mechanics requirements, such as minimal slippage and compression and shear forces.
- Biocompatibility in the L5-S1 spinal region.