Degenerative disc disease (DDD) is not an uncommon problem as we age. Treatment with conservative care to combat pain, loss of motion, and decreased function is advised first. If nonoperative care fails, then surgery may be the next step.
In this study, a specific type of artificial disc replacement (ADR) (FlexiCore Intervertebral Disc) was compared to spinal fusion. The fusion was a circumferential fusion with bone graft and metal screws. Circumferential means the bones were fused together on at least three sides of the two vertebral bones. Patients with DDD at one level (either L45 or L5S1) were included in both groups.
The FlexiCore is a metal-on-metal ball and socket type of ADR. There are two flat metal plates — one against each vertebral bone. The ball and socket device is sandwiched between the two base plates. This design makes normal intervertebral motion possible. By preserving motion, further degeneration at the next level is avoided.
The surgical techniques for both procedures were described step-by-step by the authors. Several measures were used to compare the results of these two methods. Operative time, blood loss, and length of hospital stay were compared.
Pain levels, range of motion, and disability before and after the surgery were also used. X-rays were used to evaluate motion at the involved disc space. Three types of motion were recorded: translational, angular rotation, and lateral bending.
Previous studies of other ADRs report that the use of these devices for single-level DDD compares favorably with the results of fusion. This study adds to that data. Six weeks after surgery, the FlexiCore group had better pain relief and function than the fusion group. Function continued to improve up to the two-year follow-up visit.
The metal-on-metal ADR had less wear and tear and less translational (sliding) movement than other implants that had polyethylene (plastic) parts. The advantages of ADR over fusion include preserving intervertebral motion and preventing degeneration at the next level.
Choosing patients carefully is a key to success with ADRs. Surgeon skill and experience are also important. As technology and design of the implants improve, we should continue to see better and better results with ADRs.