Sitting and prone are the two most common positions used for posterior cervical laminoforaminotomy, but other positions like the lateral decubitus have been described. In the prone position (Fig. 75.2), the patient is carefully placed prone typically upon gel rolls with the head in three-pin fixation within a Mayfield head holder. A slight bend in the bed with the knees flexed can promote venous return in the distal lower extremities. The head is positioned in a flexed posture to widen the intralaminar space to facilitate decompression between the lamina. Neck flexion is limited, due
to potential for endotracheal tube kinking, to a position that allows two fingerbreadths between the chin and the chest. Some reverse Trendelenburg adjustment to the bed bringing the operative site above the level of the heart can improve venous return and reduce bleeding. However, the surgeon and anesthesiologist must consider the possibly of air embolism as the surgical site is raised above the heart.

To prepare for the sitting position, the patient is initially placed in the supine position upon the operating table and the Mayfield head holder is affixed to the patients head, but not attached to the bed frame. The operating table is gradually adjusted to the sitting position with the back at approximately 90 degrees in relation to the floor. The attachment frame for the Mayfield is placed over the patients’ waist, and the Mayfield is secured to the frame with the patients’ head in a flexed posture. The C-arm is arced in front of the patient for a lateral image (Fig. 75.3). During the procedure, the surgeon is typically seated behind the patient using an operating chair. A narrow table (we use an instrument stand that has been modified so that the top is a 3 by 18 inch plate that is padded and draped) can be positioned within the sterile field in front of the operating chair to allow the surgeon to rest his or her arms to reduce fatigue.

Advantages of the sitting position, in comparison to the prone position, include improved fluoroscopic imaging as the patients’ shoulders tend to fall with gravity facilitating better radiographic visualization of the lower cervical spine, improved venous return that reduces venous bleeding during surgery, improved access to the patient by the anesthesiologist, and improved patient ventilation since they are not lying on their chest. Disadvantages of the sitting position include increased risk for air embolism, issues with surgeon arm fatigue, and the need to change the usual setup of the operating microscope to effectively utilize it in a horizontal position parallel with the floor. When using the sitting position, the anesthesiologist should place a precordial Doppler detector, and end-tidal carbon dioxide should also be monitored for early detection of air embolism. These modalities are very sensitive in detecting even minute amounts of entrained intravascular air. Air embolization is a very rare occurrence, but if it is detected, the anesthesiologist should notify the surgeon and elevate the venous pressure by increasing positive end-expiratory pressure or jugular vein compression. This will reveal the source of the entrainment and allow the surgeon to eliminate it, typically with bipolar cautery or bone wax. Intracardiac catheters, previously recommended prior to such sensitive detection devices, to allow aspiration of the air are no longer used as the air initially detected does not remain in the heart, and the above maneuvers will stop further entrainment of air before it becomes hemodynamically significant.

Intraoperative confirmation of the level is performed with either fluoroscopy or lateral x-ray. Fluoroscopy is beneficial in guiding the opening to avoid unneeded soft tissue injury of a more extensive exposure. The use of a K-wire to mark the level is discouraged as it may inadvertently enter the spinal canal between the lamina and injure the spinal cord. Midline exposure of the spinous process, lamina, and facets can be utilized, or a lateral muscle-splitting technique may be used. It is important to note that the cervical spinous process projects caudally, and the corresponding facet joint is at least a centimeter rostral to the tip of the spinous process. Hence, midline incision should be made a level above the corresponding spinous process to expose the desired foramen. A perfect midline incision through the avascular midline plane can limit blood loss in midline exposures. When the spinous process is identified, subperiosteal dissection is carried laterally to the medial aspect of the facets. For a single-level foraminotomy, a longitudinal incision of about 4 cm in length in the midline is often needed to facilitate the amount of lateral retraction to expose the medial facet. It is important to preserve the supraspinous as well as the interspinous ligaments to maintain stability of the posterior tension band. The dorsal musculature is retracted laterally and can be held in position by a number of commercially available retractors.