Surgical techniques for spine fusion surgery

The two primary types of medical devices used in a spinal fusion surgery include pedicle screws and anterior interbody cages. When it has been determined that a spine fusion is appropriate, the surgical technique utilized may vary.

There are several types of spinal fusion, including:

1. Posterior approaches to spine fusion
   The surgical techniques that have historically been used the most comprise spine fusion surgery that is approached from the back (vs. through the abdomen). There are three main posterior fusion techniques: a posterolateral gutter fusion surgery; a posterior lumbar interbody fusion (PLIF) surgery; and a transforaminal lumbar interbody fusion (TLIF) surgery.

2. Anterior approaches to spine fusion
   Because approximately 80% of the forces of the spine are borne through the disc space, it is much more likely that a solid fusion will be achieved and patients will have pain relief if the fusion includes the disc space. There are two primary techniques to accomplish this.

Anterior/posterior lumbar fusion
An anterior/posterior fusion surgery is typically performed through an incision in the abdomen, with removal of the disc and placement of bone graft where the disc material has been removed. A separate incision is made in the back to place the pedicle fixation bone graft. This approach may include a large amount of trauma to the muscles, a long hospital stay, and may at times be associated with a fair amount of blood loss. However, in cases where there is a lot of instability, an anterior/posterior fusion surgery can be necessary as it provides the greatest amount of stability.

Anterior lumbar interbody fusion
An anterior lumbar interbody fusion is a newer back surgery technique that involves the placement of bone graft or bone graft with an anterior interbody cage within the disc space. The most efficient way to place this is through the abdomen into the disc space. Most commonly, persons who have undergone this spine fusion surgery are able to return to their activities much more rapidly. This type of approach can be used in cases where there is not a lot of associated instability.

Additional factors for spinal fusion surgery:
In addition to the approach used, there are a number of other factors to be considered before spine fusion surgery. The following discusses several other considerations.

PLIF and TLIF surgery
The PLIF and TLIF allow for placement of bone or a cage in the disc space, increasing the fusion rate and hopefully a better clinical outcome. There is more neurologic risk because of the need to retract the nerve roots, however, major nerve injury is unusual. It has the advantage of placing a structural graft or device in the major weight-bearing part of the spine while avoiding a separate incision.

Bone graft
Traditionally bone graft has been harvested from the iliac crest (pelvis) to stimulate the fusion site. Cadaver bone often is useful in anterior fusions, but it works poorly in posterior applications. Recent advances have allowed spine surgeons to decrease the need for bone graft harvest by using substitutes, e.g., collagen sponges, demineralized bone matrix, platelet derived growth factors and, most promising, bone morphogenic protein. The bone morphogenic protein currently in use (Infuse) has FDA approval for anterior application only. Further research is ongoing to document the utility of these products, which allow for diminished patient trauma that can occur from harvesting bone graft from the patient's own hip.

Minimally Invasive Surgery (MIS)
Much work is in development to try to decrease the trauma patients incur by placing pedicle screws through smaller incisions. This is thought to result in less muscle trauma and allow for more rapid recovery after spine surgery. Caution needs to be exercised, however, as even though a technique is less traumatic, if the spine fusion rate is much lower, then there is really not an advantage. Also, it has yet to be demonstrated that minimally invasive spine fusion systems actually cause less trauma than some other surgical techniques used in the traditional open approach.