Spinal or spine implant systems made of titanium and other materials, utilizing specially designed spinal instrumentation are often used when spinal conditions require surgery. The implants facilitate fusion, correct deformities, and stabilize and strengthen the spine.
Conditions that often require instrumented fusion surgery include slippage of the spine (spondylolisthesis), chronic degenerative disc disease, traumatic fracture, and other painful forms of spinal instability including scoliosis.
Implants for Spine Surgery are made of metals like titanium, titanium-alloy or stainless steel; some are made of non-metallic compounds. These are available in different shapes and sizes to accommodate patients of all gender and ages.
Scientists and surgeons around the world are constantly working to develop and refine implants. In recent years there have been huge advances, including the advent of a hook, rod and screw systems that enable surgeons to correct spinal deformities 3-dimensionally; the development of special plates and cages that help promote spinal fusion; and the creation of small but strong implants for children.
- Rods–Rods are used, along with hooks and screws, to immobilize involved spinal levels, and to contour the spine into correct alignment. One of the original implants used in the spine, the rods are strong, yet have some flexibility so that the surgeon can shape the rod to match the contours of the patient’s spine.
- Pedicle Screws– Deriving its name from pedicles of the spinal vertebrae, these specially designed screws are carefully implanted into the pedicles. Traditionally used in the lumbar spine, with recent advances in technology and technique, surgeons are now using them in the thoracic spine too. Screws provide strong “anchorage” points to which rods can be attached. Rods can then be contoured to correct deformities and to facilitate fusion.
- Hooks– These are used with rods and other implants to anchor them to vertebrae.
- Plates– Plates are mostly used in the cervical spine. Plates are manufactured to conform to the contour of the spine and are held in place by screws set into adjacent vertebrae. When the plate requires adjustment, a contouring tool is used to customize the fit to the patient’s anatomy.
- Cages– These are most often placed between two vertebrae and are called “interbody” cages. Cages are small hollow devices with perforated walls. Bone graft or BMP is often packed into the cage to promote bone growth between the adjacent vertebrae. Cages are used to restore lost disc height resulting from a collapsed disc and to relieve pressure on nerve roots.
Application of Spine Implants
Implants are carefully chosen to ensure the best choice for the specific patient. For example, “low volume” implants are used because they reduce muscle irritation and cause less post-operative pain. For patients who are slim, “low profile” implants not visible through the skin are used. Titanium is preferred material as it is strong, light and, unlike stainless steel implants, can be used with MRIs. When suitable, use of radiolucent materials such as carbon fiber cages is also followed. Carbon-fiber implants cannot be seen on a scan but allow us to see if a bone is forming and fusion is taking place.
Future of Spine Implants
Scientists are working on developing bio-resorbable implants. These are used to facilitate fusion. However, after a year or so (when fusion should be complete) the implant is not necessary but is left in the body. Bio-resorbable implants are designed to break down when they come in to contact with water (such as body fluids). In a year, most decreases in size by 50% and are completely gone in 2-3 years. Thus the implant is present in the body when it is needed to promote fusion, and then gradually “fades-away” over a 12-36 month period. Though only a few bio-resorbable implants are available, it is hoped that in future a significant step in this field would take place.
In the past two decades, there have been major breakthroughs in the development of spinal implants. The result is a better treatment option for patients.