Technology Update: CD HORIZON® LEGACY™ PEEK Rod System

PEEK Technology: Paving the Way for Improved Spinal Load Sharing

For patients requiring spinal fusion surgery, the CD HORIZON® LEGACY™ PEEK Rod System offers a semi-rigid alternative to metal fixation instrumentation.

For some years, spinal fusion has been considered the "gold standard" for surgically treating the spines of patients whose back pain has become so severe and/or debilitating that conservative, non-surgical measures have failed to provide relief. Using bone grafts along with instrumentation such as metal plates, rods and screws, this procedure fuses, or creates a bond between, two adjacent vertebrae, ideally stabilizing the segment and easing the patient's pain, numbness, weakness and/or lack of mobility.

Recently, advances in spine surgery technology - including a greater focus on the principles of spinal load sharing - have led to significant advancements in the instrumentation that surgeons use for spinal fusion procedures. One of these is the development of semi-rigid alternatives to the metal rods that have traditionally been used. An example of this technology is the CD HORIZON® LEGACY™ PEEK Rod System, which has components made of polyetheretherketone (PEEK), a biocompatible polymer that provides stability, thus reducing stress on spinal elements.

Unlike their titanium and stainless steel counterparts, PEEK rods allow for some degree of adaptability. The elasticity of a PEEK rod is similar to that of the inner (cancellous) and outer (cortical) layers of natural bone.

Load Sharing: The Importance of Proper Spinal Balance

Load sharing principles apply to all regions of the spine, and the concept is based on the mutual integrity of two anatomic components. The first is the multi-layer series of muscles in the back, called the tension band. Collectively, these muscles provide the dynamic, compressive force to the posterior (rear) elements of the spine that keep our body in an erect position. Individual segmental muscles provide motion to the functional spinal units, called motion segments.

The second component critical to load sharing is the anterior (front) column of the spine, consisting of vertebrae and discs. Unlike the voluntarily-controlled posterior muscles, the anterior spinal column acts only as a passive restraint to the axial compression forces, or body weight, of the trunk. In a sense, the vertebrae and discs are like a column supporting a building.

In the normal lumbar spine, the anterior column supports the majority of the body's weight, or axial load, while the posterior elements, mainly the facet joints, support a much lesser amount. Normal spinal load sharing requires that both the anterior column and posterior tension band remain intact. If either becomes diseased or damaged, efficient load sharing can be compromised and the spine can become unbalanced, leading to significant muscle fatigue and localized or radiating back pain. The purpose of spinal fusion is to restore the integrity of these components and stabilize the spine.

Spinal Fusion and its Impact on Load Sharing

Spinal fusion typically involves placing bone graft into the disc space between two vertebrae, then fastening rods to the vertebrae with screws to create a fixed vertebral unit. In the lumbar spine, many spinal fusion procedures involve accessing the spine and implanting the rods and screws from the back, a fixation approach that often places the bulk of the body's weight onto the posterior elements and instrumentation rather than the anterior column, where it's normally carried. The posterior elements and instrumentation are now essentially load bearing rather than load sharing.

As a result, spinal instrumentation may be more prone to breakage and the anterior column may be less likely to fuse because it's no longer subject to normal loads. Extra pressure on the posterior facet joints and intervertebral discs may result in an excessive outward curvature of the spine (kyphosis, or "dowager's hump").

The CD HORIZON® LEGACY™ PEEK Rod System:
More Flexible Fixation, Reducing Stress While Retaining Strength

Recently, there has been a progressive shift by research specialists and surgeons toward reconstructing the spine in a way that reproduces normal spinal mechanics with instrumentation that's rigid enough to provide sufficient immobilization while fusion takes place, but not so stiff that it places excessive pressure on the adjacent facets and discs.

The CD HORIZON® LEGACY™ PEEK Rod System offers reproducible semi-rigid fixation. Designed on a "tension band" approach, based on Wolff's Law - that bone forms where it is needed - it incorporates rods made of PEEK, a biocompatible, semi-crystalline thermoplastic polymer with a long history of use in surgical implants.

When combined with Medtronic's CD HORIZON® Spinal System-based pedicle screws and minimally invasive approach options such as the MAST QUADRANT™ Retractor Set, the CD HORIZON® LEGACY™ PEEK Rod System offers surgeons and their patients an option for semi-rigid fixation with a streamlined surgical technique that preserves natural spinal anatomy.

For more information about the CD HORIZON® LEGACY™ PEEK Rod System, talk to your spine surgeon. To find a spine surgeon near you, visit our Find A Doctor locator.

It is important that you discuss the potential risks, complications, and benefits of the CD HORIZON® LEGACY™ PEEK Rod System with your doctor prior to receiving treatment, and that you rely on your physician's judgment. Only your doctor can determine whether you are a suitable candidate for this treatment.

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