To better understand the evolving future of artificial discs, it is
helpful to understand the basic parameters of existing, first generation
disc technology for treating back pain.
First Generation
First generation discs exist today, created from proven artificial disc
technology in use for over fifteen years. These discs have a constrained
design, allowing movement with no more than three independent degrees of
freedom (Figure 1). First generation designs often allow only rotation,
front to back bending (flexion/extension), and side to side (lateral)
bending.
In comparison, a healthy human disc allows six independent degrees of freedom (Figure 2). These six degrees include the motions described above and also front to back sliding (anterior/ posterior translation), side to side sliding (lateral translation), and an up and down motion (axial stretching and compression).
A healthy spine allows minimal axial (up/down) motion. As such, disc designs often address axial motion last, as it is the least critical in replicating anatomic motion.
A first generation artificial disc with its constrained design cannot properly replicate the natural anatomic disc motion. Some surgeons believe a design that limits movement is better; that an artificial disc should only allow critical spine movement. However, unique stresses occur when artificial discs limit natural disc movement. The stresses displaced normally with spine movement then transfer either to the implant (the artificial disc) or to other parts of the body.
A majority of surgeons believe the artificial disc should try to re-create as much of the natural spine motion as possible. In an ideal world, artificial discs should have six independent degrees of freedom and work with adjacent discs to avoid putting undue forces either on the implant or other areas of the spine and body. The emerging artificial discs offer multiple advantages to the patient, as well as the surgeon implanting the product.
Second Generation Discs
Improving on what already existed, surgeons and engineers involved in
first generation designs created the second generation of artificial
discs. Spine experts realized the need for a disc that better replicated
natural anatomic movements. They also recognized that surgeons and
patients would benefit from more advanced instrumentation that allowed
disc surgery to be more simply and potentially more safely done.
This site highlights second generation technology available to patients and surgeons. Additional resources covering spine anatomy, disc disease, disc history, and an ongoing clinical study should give a base of information about this exciting, fast changing technology. LDR Spine welcomes your feedback and encourages you to send any comments or questions to secondgeneration@ldrspine.com.
What about artificial discs in the future? Many spine experts agree that first generation discs have now gained acceptance after years of limited availability, making way for second generation discs to improve upon the initial designs, and predict that revolutionary third and fourth generation discs will unfold over the next ten to fifteen years.
Third Generation Discs
Spine experts anticipate third generation discs will utilize new
materials, new bearing surfaces, elastomer cores (rubber/polymer) and
advanced instrumentation with computer-guided assistance.
These new concepts and materials theoretically will improve patient outcomes; however, new technologies require more time to develop and test before use on humans. Several third generation designs are currently in progress; most have yet to be proven safe.
While these new technologies offer exciting advancements, first and second generation artificial discs remain valuable. Experts forecast the need for different technologies and approaches will persist to address patients varying anatomies, complicated injuries, and personal preferences. For example, an athletic, younger patient with back or neck problems might benefit from a device quite different from the implant best suited for an older, less active person.
Fourth Generation Discs
Experts and observers speculate widely regarding fourth generation
discs. The authorities generally agree that future technology will help
to repair and/or augment the existing disc when possible. New materials,
both synthetic and natural, will probably be used. Fourth generation
technology will attempt to restore and repair the disc to its natural
state with as little disruption as possible.
LDR Spine encourages study of the rich history of artificial discs, a technology available and now accepted after 15 years of clinical use in many parts of the world. Artificial disc pioneers applied what they learned from initial designs to create the next generation of artificial spine implants.
It remains to be seen what medicine and science will create for artificial disc designs in the future.