New implant mimicks the intervertebral disc to relieve neck pain
Celien Jacobs defended her thesis at the Department of Biomedical Engineering on April 19th.
Neck pain is often a nagging pain that can radiate to the arms, and can even result in tingling in your hands and fingers. This then usually leads to physical hindrance during daily activities. A common cause of neck pain is wear and tear of the intervertebral disc, the soft tissue in the spine that in part facilitates movement in the neck. For her PhD research, Celien Jacobs developed a new implant, trying to mimic the natural structure of the intervertebral disc with synthetic materials.
Most of the time, neck pain can be relieved with painkillers or treatments at the physical therapist. But if this does not help to relieve the pain, surgical treatment may be necessary. Until now, fusion treatment was often chosen, in which the worn intervertebral disc is removed and the adjacent vertebrae are fused together. The disadvantage of this treatment is that the loss in motion of the treated segment is compensated by adjacent segments, which become overloaded as a result. In the long run, this often causes wear and tear in the adjacent segments as well, putting you in an endless vicious cycle of problems.
An alternative treatment is to replace the worn out intervertebral disc with an implant, which can maintain the range of motion of the treated segment. This reduces the risk of overloading the adjacent vertebrae. A major drawback is that the current implants are very similar to knee and hip replacements, while they have a totally different anatomy and physiology than the natural intervertebral disc. Because of this mismatch, the risk of overloading the adjacent vertebrae remains.
Biomaterial and biomechanical design
Therefore, Jacobs developed a new implant, trying to mimic the natural structure of the intervertebral disc with synthetic materials. Similar to the natural intervertebral disc, this new implant consists of three components. The gel-like water-rich core of the natural intervertebral disc is mimicked with a hydrogel that can also absorb water. The surrounding fibrous structure of the natural disc is mimicked with a jacket made of textile. The final component is a metal ring with pins that, like cartilage, connects the intervertebral disc to the adjacent vertebrae.
To further develop this new implant, Jacobs looked at its biological and mechanical behavior during her research. She tried to further optimize the current design, testing different textile structures to find out which one works best for this application. In addition, she investigated how to ensure that this implant would grow attached to the bone of the adjacent vertebrae by testing different surface treatments. After the design optimization, she began to investigate different functional aspects.
Since the purpose of the implant is to maintain range of motion to reduce overload on the adjacent vertebrae, she also investigated whether this new implant could reproduce the motion mechanism of a natural disc. The results showed that this new design was not only able to maintain motion, but also better mimics the mechanism of motion, hopefully leading to less overloading of the surrounding structures. Finally, she was able to show that the current design could also mimic the viscoelastic properties of a natural disc. Similar to a natural disc, this new implant can absorb and release water throughout the day to provide shock absorption.
In conclusion, Jacobs' research has shown that mimicking the natural structure can lead to similar biomechanical properties. She hopes that her design can contribute to improved treatments for people with severely worn intervertebral discs.
Title of PhD thesis: “A biomimetic artificial cervical disc replacement: biomaterial and biomechanical design characterization”
Supervisors: Keita Ito and Sandra Hofmann