Lumbar disc replacement considerations
In our extensive experience with lumbar disc replacement we have found that the best results involve avoidance of the need for revision surgery, due to postoperative implant subsidence, migration or vertebral instability, and ability of the implant to replicate natural movement of the spinal segments. This success depends on several important factors. These factors include; reducing or eliminating excess distraction/separation of the vertebrae during preparation, a disc replacement implant design which provides excellent immediate attachment and subsequent vertebral adhesion, insertion tools which allow the use of full width endplates, and an implant design which allows for a posterior center of flexion and rotation without slippage.
In order to reduce the required distraction required for disc replacement insertion the most recent implants have the ability to attach to the vertebra using a keel like design which is inserted into a prepared channel. The use of textured coatings on the endplate surfaces also improves vertebral adhesion. These designs allow for implant placement without excess distraction and insure good attachment is achieved.
The use of insertion tools which secure the disc replacement using only the outermost surface have allowed for wider endplate selection. With previous designs allowance had to be made for clearance of the tool. This wide endplate design is likely to be a critical factor in reducing the incidence of postoperative plate subsidence.
A simple two piece design allows for flexion and rotation in a position posterior of the vertebral centerline. This prevents the slippage sometimes seen in the sliding core designs and lowers the risk of damage to the facet joints.
Surgeons must carefully consider these factors when considering the patient indications for lumbar disc replacement and when selecting the best implant.
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