Percutaneous Endoscopic Decompressive Laminectomy and Foraminotomy

9 Percutaneous Endoscopic Decompressive Laminectomy and Foraminotomy


Gun Choi, Ketan Deshpande, and Akarawit Asawasaksakul


9.1 Introduction


Technical advances in endoscopic instruments are allowing spine surgeons to take on the challenge of lumbar decompression by the most minimally invasive approach possible. But the procedure is still in developmental phases, with indications limited to selective cases. We wish to present a brief discussion about the current application of endoscopy in lumbar canal stenosis (Video 9.1).1,2,3,4


9.2 Choice of Patient


Indications:


• Lower limb radiculopathy or claudication from neurologic origin with or without back pain not responding to conservative treatment


• Evidence of stenosis on magnetic resonance imaging and/or computed tomography correlating with clinical presentation Contraindications:


• Degenerative spondylolisthesis (grade 2 or more)


• Profound neurological deficit


• Cauda equina syndrome


9.2.1 Classification


For all practical purposes, canal stenosis can be divided based on location:


• Central stenosis


• Lateral recess stenosis


• Foraminal stenosis


9.3 Central Stenosis


9.3.1 Technique


Step 1: Position and Anesthesia

• Conscious sedation (with propofol and remifentanil) supplemented with a caudal block with patient prone, with hips and knees in flexion and abdomen supported over bolsters.


• Level marking—target level end plates and the interlaminar window are roughly marked under fluoroscopic guidance.


• Entry point—approximately midway between the spinous process and the lateral extension of the interlaminar window (Fig. 9.1).


• Skin and intended tract infiltration—with 1% lidocaine ~ 2 to 3 mL.



Step 2: Skin Entry

• Target point—base of spinous process of proximal vertebra in antero-posterior (AP) view and posterior to the lamina in lateral (LAT) view


Step 3: Needle Insertion and Dilation

• Needle insertion—from the mentioned entry point an 18G 90-mm spinal needle is directed toward the base of the spinous process in slightly medial and cranial direction till it reaches the desired point in both AP and LAT views.


• Serial dilation—needle is replaced by a blunt tip guide wire and after a skin incision of ~ 9 to 10 mm, the tract is serially dilated until the 4th dilator (Fig. 9.2, Fig. 9.3) under fluoroscopic guidance, a circular working cannula, is passed over the final dilator and the scope is passed through it.


• This complete procedure is performed under continuous pressure irrigation using cold, antibiotic instilled normal saline. RF is used initially to clear the fat and paraspinal soft tissue and to enhance visibility.



Step 4: Decompression

• Decompression is begun by locating the junction of the superior lamina and the base of the spinous process (SP) (Fig. 9.4; Fig. 9.5).


• One should always keep the ligamentum flavum intact till the end of bony decompression, as it acts to shield the thecal sac and protect it from any inadvertent injury.


• The next step is to make an opening in the flavum, which can be done either with a blunt tip probe or endoscopic scissors and further widened using an endo punch or a side-firing laser.


• Central stenosis cases do not require diskectomy as post-operatively the thecal sac along with its contents will fall posteriorly away from the disc, so we can keep the disk intact.


• Also in the majority of the cases visualization of the traversing root is not essential but can be easily visualized, if need arises, by tilting the scope laterally.


• At this stage, one can replace the circular cannula with a beveled cannula and use the beveled end as a root retractor to get a visual confirmation of the adequacy of decompression (Fig. 9.6).


• Hemostasis is achieved using the RF cautery, and a hemo-vac drain can be inserted with a single stay suture at the skin.


9.4 Lateral Recess Stenosis


Depending on the etiology and the target level, the choice of approach may vary (Table 9.1).


9.4.1 Interlaminar Technique


There are two aspects of choosing an interlaminar approach to perform lateral recess decompression, ipsilateral interlaminar and contralateral interlaminar, with both the techniques having their own advantages and limitations (Table 9.2).


Ipsilateral Interlaminar

image Step 1: Position and Anesthesia

• General anesthesia is preferred with patient in prone position with hips and knees in flexion and abdomen supported over bolsters.


• Level marking—target level end plates and the interlaminar window are roughly marked under fluoroscopic guidance


image Step 2: Skin Entry Point

• Lateralmost point of the interlaminar window (Fig. 9.7)


• Target point—lateral end of the proximal lamina in AP and posterior to the lamina in LAT view C-arm


image Step 3: Needle Insertion and Dilation

• From the mentioned entry point an 18-gauge 90-mm spinal needle is directed toward the junction of the lamina with the facet till it reaches the desired point in both AP and LAT views.



image


Table 9.2 The pros and cons of both interlaminar approaches in lateral recess decompression














Contralateral interlaminar


Ipsilateral interlaminar


• Ease of access to lateral recess


• Maximum facet can be preserved


• Good even for central decompression, as base of spinous process and superior lamina can be accessed


• Maximum soft tissue preservation


• Familiar approach


• Retraction of root may be difficult/painful


• Needs more facetal decompression


Mar 29, 2020 | Posted by in ORTHOPEDIC | Comments Off on Percutaneous Endoscopic Decompressive Laminectomy and Foraminotomy
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