Hooks - Rods - Screws - and Cables
When is instrumentation used?
Hooks, rods, screws, and cable are types of medically designed implants used during instrumentation procedures. Trauma, deformity, and instability may be treated using spinal instrumentation.
Often, these implants are combined during a procedure - for example, screws may be used to anchor rods in place. Prior to surgery, the spine specialist determines what implants are appropriate based on the patient's deformity (eg, scoliosis), anatomy, and the corrective procedure to be performed.
What are implants made of?
Like other types of implants used in spinal instrumentation, these are made from medical grade stainless steel, Titanium, or Titanium-alloy, all of which are body-friendly. Implants made from Titanium are highly resistant to corrosion and fatigue and are MRI compatible.
There are many types of hooks - such as pedicle, sublaminar, or infralaminar hooks - named to describe where they anchor on the spine. For example, a pedicle hook is designed to anchor at a vertebral pedicle. Sublaminar means above the lamina and infralaminar - below the lamina. Hooks may be used alone or to secure rods or cable in place.
Some rods are rounded and smooth, others are threaded. Rods are usually used in pairs and are available in many pre-cut lengths. In some cases, the spine specialist will modify the length to fit the patient's anatomy, which may include contouring the rod to match the curve of the spine. The instrumentation system provides the surgeon with specialized tools to cut and contour rods.
Screws are used to secure plates and rods in place and to compress bony structures together (e.g. fracture). Bone screws are available in different lengths, widths, and at fixed or variable angles.
Medical grade cable is flexible and strong. The surgeon can sequentially tighten (or loosen) the cable to apply a precise amount of tension to a particular area of the spine. Special tools assist the surgeon to measure and apply tension, cut, and crimp the cable prior to locking into place.