Keywords
endoscopic spine surgery - interlaminas approach - minimally invasive
Palavras-chave
cirurgia endoscópica da coluna - abordagem interlaminar - minimamente invasiva
Introduction
The increased life expectancy has brought an increase in the incidence of degenerative
pathologies of the spine.[1] The increment in comorbidities in the older population makes the use of less invasive
techniques attractive and with lower risks.[2]
[3] Early rehabilitation, less post-operative local pain, minimized muscle damage, and
reduced hospital stay are some advantages of endoscopic spine surgery.[4]
[5]
[6]
Endoscopic access to the lumbar spine essentially consists of transforaminal and interlaminar
techniques. The more caudal the level, the larger the size of the interlaminar space,
making it more favorable to perform the interlaminar approach, especially at the levels
L4-5 and L5-S1.[7]
With the evolution of spinal endoscopy instruments, especially bone drills, the interlaminar
approach has been routinely used for centrolateral disc herniations and spinal canal
stenosis. The interlaminar window is the door to all kinds of pathologies and could
be opened with the endoscopic burr and Kerrison, widening the interlaminar window
and broadening the indications of the endoscopic lumbar spine surgery.[8]
The learning curve for the interlaminar approach requires training and getting used
to handling the endoscope independently of the working cannula. Sequentially, the
correct exposure and identification of the anatomy of the interlaminar window is crucial
for safe access and complication reduction. Direct access with the opening of the
ligamentum flavum may result in non-exposure and identification of the shoulder of
the descending root, access through the axilla and an increased rate of manipulation,
and injury to neurological structures.
Objectives
To increase the safety of the interlaminar approach and minimize complications, the
authors propose in this paper the systematization of an expanded interlaminar approach
in a pragmatic way through the Castro-Brock technique.
The main point is direct visualization of the correct anatomy is crucial for successful
endoscopic navigation.
The technique described is based on 2 principles:
-
Initial puncture is on the bone (upper lamina) and not on the yellow ligament. Subsequently
identification of the bone structures (spinous process basis, upper lamina, and inferior
articular process in a craniocaudal direction is performed
-
Drilling and enlarging the interlaminar bone window is routinely performed, followed
by en bloc flavectomy with customary identification of the descending root shoulder
before accessing the disc.
Methods
Here we describe the step-by-step of the Castro-Brock technique, didactically divided
into 10 steps and with representative images aiming to increase the safety of the
interlaminar approach and reducing the risk of injury to neurological structures.
Results
The description of this new technique for performing what we call an expanded interlaminar
approach named the “Castro-Brock technique”, is systematized in the following steps:
-
The upper lamina is marked with radioscopy ([Fig. 1]) and the puncture is carried out towards the upper lamina with the dilator after
incision of the skin and muscular fascia ([Fig. 2]), feeling through the haptic with the dilator the base of the spinous process, moving
in a lateral direction until feeling the step between the lamina and the interlaminar
window at the junction of the lamina with the IAP (Inferior Articular Process).
-
Introduction of the working cannula and endoscope, identifying the base of the spinous
process, upper lamina, and IAP as well as visualization of the interlaminar window
medial to these structures ([Figs. 3] and [4]) and creation of a virtual cavity for the flow of saline solution. The sequence
of identification from medial to lateral is therefore: spinous process basis, upper
lamina, IAP, interlaminar window
-
The facet capsule in de desinserted medially in a cranial-caudal direction until the
tip of the IAP is identified ([Figs. 5] and [6]), continuing with the drilling of the upper lamina and IAP in a medial-lateral direction
for approximately 6 mm (twice the size of the 3mm drill), from cranial to caudal,
becoming the flavum ligament and the SAP (Superior Articular Process) more evident
([Fig. 7]); the SAP is in a deeper anatomical situation than the IAP ([Fig. 8]).
-
Drilling of the SAP in a cranial-caudal and medial-lateral direction ([Fig. 9]) until the disinsertion of the flavum ligament from the SAP and the inferior lamina
([Fig. 10]).
-
After yellow ligament disinsertion it is possible to identify the descending root
and proceed with the foraminotomy using a Kerrison ([Fig. 11]) to promptly release the compression on the descending root and locate it to avoid
injury ([Fig. 12]).
-
Opening the flavum ligament next to the superior lamina ([Fig. 13]) in a medial to lateral direction ([Figs. 13], [14], [15]) and cranial to caudal until finding the previous opening performed at the level
of the SAP and inferior lamina ([Fig. 16])
-
Opening the flavum ligament in its medial portion in a cranio-caudal direction to
the inferior lamina ([Fig. 17])
-
Removal of the flavum ligament en bloc ([Fig. 18]) allowing to visualize the dural sac and descending nerve root ([Fig. 19]), including its axila and shoulder ([Fig. 20])
-
The approach is mandatorily performed through the shoulder of the descending nerve
root ([Fig. 21]), with its detachment along the entire length exposed ([Fig. 22])
-
The descending root is dislocated medially with the working cannula (the lamina is
gently and cautiously rotated 180 degrees) and the disc/hernia is exposed ([Fig. 23])
Fig. 1 Upper lamina is marked with radioscopy.
Fig. 2 Puncture of the upper lamina with the dilator.
Fig. 3 After introducing the working cannula and endoscope it is crucial to identify from
medial to lateral the following structures: 1. spinous process basis / 2. Upper lamina
/ 3. IAP / 4. interlaminar window.
Fig. 4 IAP and facet capsule (*) and the interlaminar window medially (**).
Fig. 5 The facet capsule is desinserted medially in a cranial-caudal direction with scissors.
Fig. 6 The tip of the IAP is identified (*). It is also possible to visualize the inferior
lamina (**).
Fig. 7 Upper lamina drilled (1); IAP drilled (2); SAP bellow IAP (3); Yellow ligament exposed
(4).
Fig. 8 IAP drilled (1); SAP deeper than IAP (2); Articular cartilage (3).
Fig. 9 SAP is drilled from medial to lateral and cranial to caudal in the direction of the
inferior lamina.
Fig. 10 Disinsertion of the yellow (flavum) ligament from the inferior lamina by drilling.
Fig. 11 Foraminotomy is performed using a Kerrison.
Fig. 12 Descending nerve root promptly decompressed and identified (1); SAP drilled (2);
Inferior laminar drilled (3).
Fig. 13 Superior and medial portion of the yellow ligament will be opened (1); previous opening
and descending nerve root foraminotomy (2).
Fig. 14 The tip of the scissors must be visualized.
Fig. 15 The thicker superficial layer (1) and thinner deeper layer (2) of the flavum ligament.
Fig. 16 The two openings are connected.
Fig. 17 The flavum ligament is divided in its medial portion in a craniocadal direction until
the inferior lamina.
Fig. 18 After detachment, the flavum ligament is removed en bloc.
Fig. 19 After flavum ligament removal it is possible to identify the dural sac (1) the descending
nerve root (2).
Fig. 20 Dural sac (1); descending nerve root (2) and its axila (3) and shoulder (4).
Fig. 21 A detacher/dissector is inserted through access to the descending nerve root shoulder.
Fig. 22 The descending nerve root is detached and mobilized along its entire length.
Fig. 23 Disc / herniation exposed after the root dislocation maneuvers.
Conclusions
The Castro-Brock technique described here provides two main advantages through an
expanded interlaminar approach: it allows good visualization of the anatomy and promotes
itself decompression of neurological structures before accessing the disc/herniation.
In this way, inadvertent injury to neurological structures as well as unwanted surgical
complications are avoided, increasing the safety of performing the interlaminar approach.
