The FDA recently approved the Medtronic Prestige LP Cervical System for treating degenerative disc disease at two adjacent vertebral levels (between C3 and C7). The device is said to be Medtronic’s third clinically-proven cervical implant and its first to be approved for use in both one-level and two-level procedures. The system was approved to treat single-level cervical disc disease in July of 2014, and approval for use at two adjacent levels was granted earlier this month. As described in Medtronic’s press release, the ball-and-trough design of the Prestige LP allows a variety of movements including bending, rotation, and translation.
Fig. 1: Medtronic Prestige LP Cervical Implant System
According to Medtronic, the Prestige LP Cervical System serves as a complete replacement for one or two intervertebral discs. The human spinal column is composed of twenty four vertebral bones stacked on top of each other. The uppermost seven bones are referred to as the cervical vertebrae, and they are labeled C1 – C7. Flexible intervertebral discs (Fig. 2 below) act as shock absorbers between adjacent vertebrae. Each disc is composed of an inner jelly-like material called the nucleus pulposus and a tough outer wrapping called the annulous fibrosus. In addition to cushioning shock, the discs allow bending, twisting, and flexion of the spine.
Fig. 2: Cross-sectional view of healthy intervertebral disc
According to the Arthritis Foundation, wear and tear on intervertebral discs is part of normal aging. As we grow older, the discs can dry out and lose their shock absorbing capacity. Stress from daily activities can cause tears in the annulous fibrosus resulting in herniation of the inner jelly-like core. Furthermore, because intervertebral discs have little blood supply, their ability for self-repair is limited. As a result, once a disc is injured, it may continue to deteriorate. Studies using Magnetic Resonance Imaging (MRI) show that nearly everyone over age 60 has at least some disc degeneration. However, not all people affected by disc degeneration will experience discomfort. According to the American Academy of Orthopaedic Surgeons, pain and disability due to cervical disc degeneration are often treated with physical therapy, anti-inflammatory medications, and steroid injections. When these options fail to alleviate symptoms, surgical options may be considered.
According to the UCLA Spine Center, the traditional surgical approach to treating cervical disc disease involves removing the affected disc (called discectomy) and using metal hardware to fuse the vertebrae above and below it. The preferred procedure is called Anterior Discectomy and Cervical Fusion (ADCF). During ADCF, the diseased disc is removed and replaced with bone graft or a plastic spacer. Adjacent vertebrae are then fused using a metal plate and screws. Because normal cervical discs are flexible and permit movement of adjacent vertebrae, cervical discectomy and fusion can restrict neck motion. However, compared to this traditional approach, replacing a diseased disc with an implant can allow for greater neck motion after surgery and reduce stress on remaining vertebral bodies (Fig. 3 below).
Fig. 3: Cervical range of motion in two-level cervical disc replacement (left) anterior discectomy and fusion (right)
The Medtronic Prestige LP Cervical Disc joins others that are FDA approved for use at two vertebral levels. In August, 2013 the Mobi-C Cervical Disc (Fig. 4 below) made by Zimmer Biomet (formerly LDR Global) became FDA approved for this indication. A 2015 study published in the Journal of Neurosurgery: Spine concluded that two-level implantation of the Mobi-C Cervical Disc was statistically superior to traditional spine fusion. According to the study’s lead investigator Robert Jackson, MD, several studies have shown implants to be superior to spinal fusion. However, few studies have investigated two-level implantation in the cervical spine.
Fig. 4: Zimmer Biomet Mobi-C Cervical Disc
Several clinical trials have investigated the safety and effectiveness of the Medtronic Prestige LP Cervical Disc System. A 2015 study published in the Journal of Neurosurgery: Spine investigated use of the implant in one-level procedures. It reported a 24 month success rate of 93.5% for the Prestige LP investigational group of 280 patients compared to 83.5% for ACDF controls. Criteria for success included at least 15 points of improvement on the neck disability index (NDI), maintenance or improvement of neurological status (including reflexes and sensory & motor function), maintenance of disc height, and the absence of adverse events. According to the study authors, patients who received the Prestige LP reported “significantly improved pain and disability outcomes” as good as or better than spinal fusion up to 24 months after surgery. As reported by Medtronic, a two-level trial including 209 investigational patients (and 188 controls) was conducted at 30 sites throughout the United States. At 24 months, the overall success rate for the Prestige LP was 81.4% compared to 69.4% for controls who received two-level ADCF.
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