I know that artificial disc implants for the neck come in different sizes and types. My basic understanding is that one type has some movement of the core (center part) while others are stationary and don't move. If I have this surgery done, which type should I go with?
Each patient undergoing this surgical procedure to replace a degenerated or otherwise damaged disc in the cervical spine (neck) is evaluated by the surgeon. It's important to select the correct size and shape of implant that will best suit each individual.
But there are also different types of implants. The main difference is whether or not the device has a moveable center. If it has a core that shifts, glides, or moves over the lower plate, it is referred to as an unconstrained implant with a mobile core. If the center does not move, it is constrained with a fixed core.
The moveable core tends to put more pressure on the facet (spinal) joints. The fixed core takes more of the pressure and load on itself and translates only half as much pressure to the spinal joints compared with the replacement with the mobile core.
Whether or not these differences result in more (or less) pressure on the adjacent vertebral segments is currrently being studied. Likewise, the long-term effects and differences with these two different types of implants is under investigation.
Most surgeons train using one particular type of implant so your choices may be determined by the surgeon you see. The type of degenerative damage and number of disc/vertebral levels affected may impact the type of implant you receive. Once the surgeon evaluates you and reviews imaging studies, then the specifics of the surgery can be discussed. That would be a good time to bring this question up.
Sang-Hun Lee, MD, et al. Comparison of Cervical Spine Biomechanics After Fixed- and Mobile-Core Artificial Disc Replacement: A Finite Element Analysis. In Spine. April 20, 2011. Vol. 36. No. 9. Pp. 700-708.
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