Surgical instruments are inserted through a small, thin tube, with visualization provided by an endoscope, which is attached to a video camera. Imaging from the camera is viewed by the surgeon on a monitor. Small instruments are used to remove deteriorated disc material and insert bone graft and an implant into the disc space.
Confining all instruments to the tube (or sometimes two tubes) is designed to minimize disruption to surrounding tissue and bone, with the goal of less tissue damage and faster healing times.
A minimally invasive ETDIF usually involves two or three relatively small incisions (e.g. 1/2 to 3/4 inch) in the skin. A tube is inserted through the skin and soft tissues and through a natural opening in the spine called the neuroforamen, or foraminal opening. This approach to the disc is called "transforaminal" because it is through or "trans" the "foraminal" opening. The tube(s) create access—called a working channel—for the surgeon to the operative area.
Minimally Invasive ETDIF Step by Step
Here is an outline of a typical ETDIF:
Preparation for the procedure
- The patient lies face down to prepare for the procedure. General anesthesia is usually used. There is some possibility that general anesthesia may be avoided in select patients.1
- An incision of about one centimeter is made on the most symptomatic side of the spine at the level of the problematic disc.
- Fluoroscopic (live X-ray) visualization is used to identify the appropriate disc.
Preparing the disc space for fusion
- A thin tube is inserted through the incision and into the disc area through the neuroforamen opening, the channel through which the nerves exit the spinal canal. A dilator is used to enlarge the size of the tube and provide a working channel for the operative instruments.
- The endoscope is inserted through the tube into the disc to allow the surgeon to assess the disc.
- The disc area is irrigated with antibiotic solution minimizing the risk of post-operative infection.
- Special instruments are inserted into the tube(s) to remove damaged portion of the disc, and the parts that are cut away are extracted through the tube(s).
- Cartilage covering the surfaces of the bones bordering the disc is removed and extracted through the tube.
- Dilators are then inserted into the disc to restore the disc height and normal spacing between the vertebrae, as necessary.
- This concludes the part of the operation that prepares the disc space for the fusion. The success of the disc preparation is confirmed endoscopically. This part of the process is essential to ensure that bone graft inserted into the disc space is likely to fuse to the bone surfaces bordering the disc.
Inserting bone graft for the fusion
- The disc space is then packed with bone graft. The bone graft material may include bone chips from the patient’s hip bone, cadaver bone mixed with bone marrow from the patient, and cadaver bone inserted with a bullet-shaped cage (implant).
- Absorbable sutures are used to close the wound and the surgical track is infiltrated with local anesthetic for immediate post-operative pain control. Antibiotic dressing is placed on the wound.
In some cases, screws, reinforced with rods, may be attached to the back of the vertebra to add stability and prevent movement in the area while the bone graft sets. The bone graft fosters bone growth around these rods, and they are typically left in place even after the bone graft takes hold.
ETDIF at L5-S1
There are added challenges in this type of approach concerning a fusion in the lowest disc in the lumbar spine (L5-S1) needs fusion. Endoscopic transforaminal interbody fusion of L5-S1 is performed through a small window in the hip bone, minimizing the risk of injury to the important structures in the spine or back wall of the abdominal cavity.
An endoscopic ETDIF operation usually takes about one and a half to two hours to complete, but may take longer.