Cone Beam Intraoperative Computed Tomography-based Image Guidance for Minimally Invasive Transforaminal Interbody Fusion

This method can help answer key questions in the neurosurgical field as its main advantage is the utilization of intraoperative navigation and the minimization of required fluoroscopy and associated radiation effects. After inducing general anesthesia, position the patient in the prone position on a Jackson table with a chest bolster and heat pads and prep and drape the patient's back according to standard protocols. Use a number 15 blade to make a small stab incision over the posterior superior iliac spine contralateral to the side of the planned transforaminal lumbar interbody fusion and place a Jamshidi needle through the stab incision into the ilium to harvest the bone marrow aspirate.

Drive the navigation reference frame into the posterior superior iliac spine in a trajectory that places the reference arc inferior and medial to the posterior superior iliac spine and cover the wound with the sterile drape with the reference arc exposed. Perform an intraoperative computed tomography scan using the navigation system to plan the pedicle screw trajectories. Then use a high-speed drill equipped with the navigated drill guide and a two to three millimeter bit to cannulate the pedicles and place cannulated pedicle screws with reduction towers over the K-wires on the side opposite the transforaminal lumbar interbody fusion.

To determine the trajectory of the dilator along the disc space, use the navigation system to orient the tubular dilators for the placement of additional dilators in the transforaminal lumbar interbody fusion. Confirm the retractor positioning via navigation and use the high-speed drill to perform a laminotomy and facetectomy according to standard protocols under a dissecting microscope taking care that the lateral border of the laminotomy is the medial aspect of the facet joint and that the medial border of the laminotomy is the medial edge of the lamina. Use a Woodson Elevator to dissect the ligamentum flavum from the dura.

Once this is achieved, use a two or three millimeter Kerrison rongeur to remove the ligamentum flavum from the bone. If contralateral decompression is required, angle the retractor across the midline and use the rongeur to remove the underside of the contralateral lamina, ligamentum flavum, and hypertrophic facet capsule. Use the navigation again to identify the trajectory along the disc space to facilitate a safe and thorough discectomy and use shavers and distractors to prepare the disc space.

After completing the decompression and facetectomy, the thecal sac can be gently retracted medially to visualize the disc space. The trajectory can be confirmed using image guidance. The thecal sac is gently retracted medially and a number 15 blade is used to perform an annulotomy.

The discectomy is completed using a combination of pituitary rongeurs, curets, and rasps. Upon completion of the discectomy, use intermittent fluoroscopy to visualize the degree of distraction required during the interbody cage trial placement to ensure preservation of the end plates. Now mix the allograft cellular bone matrix with the harvested autologous bone marrow aspirate and carefully pack the mixture into the disc space.

Insert the interbody cage and confirm the cage position via lateral and anteroposterior fluoroscopy. Once the transforaminal lumbar interbody fusion has been completed, place the remaining pedicle screws and carefully drive a pre-bent rod through the screw heads below the dorsal lumbar fascia using periodic fluoroscopy to confirm an adequate rod length has been achieved. Gently compress the rods to induce lordosis before securing the rods with locking set screws.

After obtaining a final fluoroscopy, close the thoracodorsal fascia with a zero polyglactin 910 suture and the subcutaneous tissue with a 3-0 polyglactin 910 suture. Then approximate the skin edges with skin closure strips and apply a water tight dressing to the wound. In this representative study, 50 patients presented with a variety of pathologies 10 of whom had undergone a previous surgery at the level of pathology.

In half of the patients, a left-sided approach was used and a single level was fused in most of the patients with a significant increase in the operative time observed in patients with multiple level fusions. After watching this video, you should have a good understanding of minimally invasive transforaminal lumbar interbody fusion procedures using image guidance for the placement of the pedicle screws and minimal fluoroscopy for the placement of the interbody cage.