Cervical Laminoforaminotomy with Working Channel Endoscope

47 Cervical Laminoforaminotomy with Working Channel Endoscope

Gun Choi and Akarawit Asawasaksakul

47.1 Introduction

Posterior cervical foraminotomy has been applied extensively in the management of unilateral cervical radiculopathies, either due to a foraminal disk or due to bony spurs projecting into the foramen.1 Keyhole laminoforaminotomy with the use of an operating microscope has limited morbidity of the paraspinal soft tissue and enhanced safety of the neural structures.^1,2,3 Sequential dilator systems like the METRx have also reduced intraoperative bleeding and surgical times. The results are equivalent between open and minimally invasive approaches.^3,4,5,6,7 To further benefit the patient in terms of the most minimally invasive approach possible, we have combined keyhole surgery with a working channel endoscope (Video 47.1).

47.2 Surgical Technique

47.2.1 Position and Anesthesia

• The patient is placed in the prone position and general anesthesia is preferred (Fig. 47.1).

• The patient is positioned on a radiolucent table with the neck in either neutral or slight flexion to facilitate interlaminar approach and drilling.

• Shoulders need to be strapped and pulled caudally to allow visualization of lower cervical levels on lateral view fluoroscopy.

• Level marking is done before scrubbing/draping to facilitate changes in position if needed.

47.2.2 Needle Insertion

• The target point for the needle tip is the V point of the cranial lamina on the symptomatic side—i.e., the lateral-most part of the lamina approximately correlating with the location of the pedicles (Fig. 47.2).

• It is always safe to target the needle toward the inferior margin of the cranial lamina, because in the cervical spine the laminae are significantly overlapped and targeting the caudal lamina may result in inadvertent entry of the needle into the interlaminar space toward the spinal cord.

• An 18 G 90-mm spinal needle is directed toward the target point under lateral view fluoroscopy (Fig. 47.3).

• Inclination of the needle trajectory is highly variable depending on the level, but the needle should be perpendicular to the lamina, in the mediolateral plane, and slightly cranial to caudal.

• The needle advancement is stopped when the bone is encountered and the needle is replaced with a 0.9-mm guidewire.

Fig. 47.1 Patient in prone position with slight neck flexion. Also shown is initial level marking.

Fig. 47.2 The V point of the cervical lamina is formed where the inferior border of the upper lamina and the superior border of the lower lamina converge.

Fig. 47.3 Skin entry point for needle insertion.

47.2.3 Instrument Placement

• A 1-cm skin incision allows passage of sequential dilators over the guidewire (Fig. 47.4).

• It is essential to ensure that the serial dilators are held securely against the lamina to make sure that no soft tissue obliterates the endoscopic view.

• Serial dilators avoid the need for soft tissue dissection by pushing the tissue away, resulting in reduced postoperative pain and bleeding.

• The dilators are followed by the passage of a 7.5-mm round working cannula, which accommodates the working channel endoscope, and continuous-pressure cold irrigation with antibiotic-instilled normal saline (Fig. 47.5).

Fig. 47.4 (a,b) Sequential serial dilators are used for splitting the paraspinal muscles before establishing the working portal.

Fig. 47.5 (a) The working cannula, (b) anchoring point on AP view, and (c) anchoring point on lateral view.

Fig. 47.6 Endoscopic view of bleeding control using the bipolar RF probe.

Fig. 47.7 (a) Endoscopic view of diamond bur touching laminae at V point; (b) initial starting point and drilling; (c) view after partial removal of lamina.