Spinal instrumentation, also known as spinal implants, devices or hardware, uses surgical procedures to implant titanium, titanium-alloy, stainless steel, or non-metallic devices into the spine. Instrumentation provides a permanent solution to spinal instability. There are many different types, shapes and sizes of medical implants designed specifically to treat spinal disorders in people of all ages.

Examples of spinal implants include:

• Plates
• Pedicle screws
• Expandable cages
• Artificial discs
• Rods
• Connectors
• Interspinous stabilization devices (designed to fit between your spinous processes in the back of your spine)
• Vertebral body tethering
• Sacroiliac (SI) joint fixation devices
• Interbody devices (cage-like structures that support bones, either between bones or in place of them, while new bone growth occurs through and around them)

Spinal fusion is a process using bone graft to cause 2 opposing bony surfaces to grow together. In medical terminology, spinal fusion is called arthrodesis. Bone graft can be taken from the patient (termed autologous or allograft bone) during the primary surgical procedure or harvested from other individuals (termed allograft bone). Another option for some patients undergoing lumbar (low back) spine surgery is bone morphogenetic protein (BMP). BMP helps to stimulate new bone to grow.

Why Instrumentation and Fusion Are Performed Together

Instrumentation is used during spinal fusion because it helps maintain spinal stability while facilitating the process of bone fusion. These procedures are used to restore stability to the spine, treat spinal deformity (such as scoliosis), and bridge space created by the removal of a spinal element (eg, intervertebral disc) during a spinal decompression procedure.

Both procedures work together to immobilize the involved spinal level(s). This does not necessarily mean the patient is unable to move (eg, bend over). Many patients report that they actually feel more mobile because their pain has been reduced or eliminated as a result of spinal fusion surgery.

With instrumentation, there is less need for rigid external spinal bracing after spinal fusion. Much like a cast stabilizes a broken bone to heal, instrumentation stabilizes the 2 bony components of a fusion while they heal. The hardware basically functions like an internal brace. In fact, most instrumented spinal fusions are so stable that bracing may only recommended for comfort.
Instrumentation placed without fusion can result in hardware failure. All metal fatigues with repetitive stress. Continual stress on an implant, unsecured by a solid bone growth (healed fusion), can lead to screw pullout or even fracture of the metal. This can result in broken screws, rods, and even complete breakdown of the construct. Consequently, a solid bony fusion is crucial to the proper healing of a spinal fusion.

Factors such as osteoporosis and smoking are known to impair bone healing and reduce the success of fusion. These patients are more likely to have a pseudofusion (false fusion), which can result in continued pain at the surgical site and implant/device failure. A bone growth stimulator may be prescribed by the surgeon to help avoid fusion problems.