Keywords
spine - endoscopy - ultrasonography - interventional
Palavras-chave
coluna - endoscopia - ultrassonografia intervencionista
Introduction
Degenerative diseases of the lumbar spine have a high prevalence, reaching 27.3% of
the population and increasing with age and risk factors such as obesity.[1] Degenerative disc disease occurs in 12.2% of the patients, and is frequently associated
with low back pain and lumbosciatalgia.[2]
Minimally invasive spine surgery includes procedures that have the common aim of avoiding
biomechanical complications, preventing damage to crucial posterior stabilizers, and
preserving the stability and structural integrity of the spine.[3] So it is possible to perform surgeries with less tissue aggression, faster postoperative
recovery, and shorter hospital stays with viability and efficiency, increasing its
accessibility in the last two decades.[2]
The percutaneous endoscopic, or full-endoscopic, discectomy technique has been scientifically
proven to be a good alternative to open discectomy, especially for lumbar disc herniation,
and the main surgical field has been shifted from the intradiscal space to the epidural
space.[4] Percutaneous endoscopic lumbar discectomy becomes particularly attractive for sequestrectomies,
with the advent of angled scopes allowing 360° visualization and enabling the removal
of extruded lumbar disc fragments while preserving the disc.[5]
The two major approaches of endoscopic spine surgery are transforaminal and interlaminar,
with different techniques and indications.[6] The interlaminar endoscopic technique is used for discectomies involving mostly
central-lateral disc herniations, specially at the L4 to 5 and L5 to S1 levels, which
correspond to the majority of lumbar disc hernias.[7] Classically, the approach is performed with the aid of fluoroscopy during the surgical
procedure, which assists in the puncture of the interlaminar window and the positioning
of the working cannula for the endoscope insertion.
Ultrasonography can visualize spine anatomy, including the ligaments, erector spinae
muscles, facet joints, transverse processes, foramina, and interlaminar spaces; it
can also guide injections and interventional procedures.[8]
The use of radioscopy can pose risks to patients and healthcare professionals related
to radiation. To minimize the use of intraoperative radioscopy and its risks, we describe
in this paper an unprecedented technique, consisting of the ultrasound-guided, in-plane,
interlaminar, lumbar endoscopic approach, with a smartphone-adapted endoscope and
portable light source.
Materials and Methods
The technique was demonstrated in a cadaveric specimen using the Sonosite M-Turbo
Ultrassound (FujiFilm SonoSite, Bothell, WA, USA) to perform the interlaminar in plane
lumbar L4–5 and L5-S1 approach bilaterally with the puncture of the interlaminar window
guided by ultrasound using a 2–5MHz curvilinear probe. An optical smartphone camera
adapter MedEasy (MedEasy, São Paulo, SP, Brazil) was attached to the endoscope in
addition to a portable LED lamp PhlatLight (Luminus Devices Inc., Woburn, MA, USA)
([Fig. 1]).
Fig. 1 Optical smartphone camera adapter attached to the endoscope in addition to a portable
LED lamp
The punctures were then performed in the L4 to 5 and L5 to S1 interlaminar windows
bilaterally, guided by ultrasound and directed to the V point, which corresponds to
the intersection of the inferior articular process of the superior vertebra with the
superior articular process of the inferior vertebra and ligamentum flavum.
The step-by-step technique was didactically elaborated in 10 steps, which are presented
in the results.
Subsequently, an open dissection of the specimen was performed with identification
of the opening sites of the flavum ligament.
Results
Technical Note
-
With the specimen in the prone position and using a low frequency (2–5 MHz) curvilinear
ultrasound probe oriented longitudinally in the midline, the sacrum is identified
by seeing an hyperechogenic ramp on ultrasound ([Fig. 2]).
-
In the midline, the transducer is directed cranially, allowing the identification
of the spinous processes of L5 and L4, which appear as more superficial hyperechoic
structures with a deeply acoustic shadow ([Fig. 3]).
-
From the midline, the transducer is moved laterally by 1 cm, making it possible to
visualize the non-continuous, hyperechoic structures that resemble the image of a
“horses' race”, constituting the sonographic image of the laminas. Between the laminas,
it becomes possible to identify the flavum ligament as part of the posterior complex
([Fig. 4]).
-
Going laterally, it is also possible to see the anterior complex, formed by the posterior
longitudinal ligament, disc, and ventral dura mater ([Fig. 5]).
-
Proceeding with the transducer for approximately 1 cm more laterally, it is possible
to identify more rounded hyperechoic structures resembling “mountains and valleys”,
which corresponds to the facet joints ([Fig. 6]).
-
With the ultrasound positioned longitudinally in a paramedian position for approximately
1 to 1.5 cm, having identified the most lateral portion of the laminas and visualizing
it on the ultrasound screen, the puncture needle is introduced in a caudal to cranial
direction in-plane with the ultrasound probe. The puncture needle is inserted with
its direct visualization by the ultrasound screen, progressing from a caudal to cranial
direction, parallel to the laminas, until it touches the flavum ligament of the correspond
level. At this point, resistance is felt due to the presence of the flavum ligament.
The puncture needle is inserted with its blade positioned posteriorly, and the bevel
opening is in a cranial direction in order not to enter the lamina of the superior
vertebra ([Fig. 7]).
-
After contact with the flavum ligament, a guide wire is inserted through the needle
up to the flavum ligament. The needle is removed, and an incision of approximately
1 cm is made in the skin and muscle fascia ([Fig. 8]).
-
The dilator is inserted up to the flavum ligament ([Fig. 8]).
-
The working cannula is inserted over the dilator, with its blade directed laterally
and the bevel opening medially until it reaches the flavum ligament ([Fig. 8]).
-
A 30° endoscope is introduced with an optical adapter from the endoscope camera to
a smartphone and portable endoscopic lighting, visualizing the flavum ligament. The
ligament is opened at this site with endoscopic scissors. These steps are performed
in L4 to 5 and L5 to S1, bilaterally ([Fig. 8]).
Fig. 2 Sacrum is identified by seeing an hyperechogenic ramp on ultrasound
Fig. 3 Spinous processes of L5 and L4, which appear as more superficial hyperechoic structures
with a deeply acoustic shadow
Fig. 4 Laminas are visualized as non-continuous hyperechoic structures that resemble the
image of a “horses race” (arrow); between then it becomes possible to identify the
flavum ligament as part of the posterior complex (circle)
Fig. 5 Anterior complex formed by the posterior longitudinal ligament, disc and ventral
dura mater
Fig. 6 Facet joints resembling to “mountains and valleys”
Fig. 7 Needle tip going through the flavum ligament. A resistance is felt at this moment
Fig. 8 Needle, guide wire, dilator, working cannula and endoscope insertion
The ultrasound enabled the identification of the interlaminar space in all the punctures
performed.
In all punctures, the opening of the ligamentum flavum was performed in the most lateral
part of the interlaminar window, near the junction of the superior and inferior articular
processes of the corresponding vertebrae ([Fig. 9]).
Fig. 9 Punctions sites
Discussion
Endoscopic spine surgery has been increasingly used to treat spinal cord and nerve
roots pathologies, promoting a paradigm shift in minimally invasive spine surgery.[9] The beginnings of this technique date back to 1983, when Forst and Hausmann[10] used an arthroscope to access the intervertebral disc, followed by the first description
of an endoscopic discectomy by Kambin et al., in 1988.[11]
The intraforaminal, or transforaminal, approach Is the oldest technique allowing intradiscal
and extradiscal access.[12] The transforaminal endoscopic approach was initially the most used procedure for
performing endoscopic discectomies.[13] However, in 2006, Choi et al.[14] reported for the first time the successful endoscopic removal of a herniated L5
to S1 disc using the interlaminar approach, which is currently one of the most used
techniques for percutaneous decompression procedures.
The interlaminar approach is an interesting option for the most caudal levels of the
spine, especially L5 to S1, making it possible to avoid the iliac crest and to access
more medially based pathologies.[15] The chance of herniated lumbar disc to occur either at L4 to 5 or L5 to S1, in patients
between 25 and 55 years old, is approximately 95%.[16] Besides, medial disc herniations (central and subarticular) are more common than
lateral ones (foraminal and extra foraminal), corresponding to 79 and 21%, respectively.[7] These are some of the reasons associated with the growing indication of the interlaminar
approach.
In a recent meta-analysis, Kim et al.[17] showed the endoscopic lumbar discectomy having better results than the open lumbar
discectomy concerning improvement to the visual analogue scale for pain and the Oswestry
disability index, resulting in lower hospital stay and operative times.
The radiation dose to which patients and medical professionals who work with the use
of fluoroscopy in the intraoperative period are exposed is of great concern, and it
is good practice to develop strategies that can minimize the use of such methods.
Ahn et al.[18] published a prospective study aiming to determine the radiation dose to which surgeons
are exposed during percutaneous endoscopic lumbar discectomy; their results demonstrated
that, without proper radiation protection, a surgeon performing 291 endoscopic discectomies
annually would be exposed to the maximum allowable radiation dose.
Ultrasonography has been used either as a complement or a replacement to the use of
radioscopy for surgical procedures in several areas. To visualize the lumbosacral
spine sonoanatomy, a low frequency (2–5MHz) curvilinear ultrasound probe is used,
as the adult lumbar spine's neuraxial structures are situated in a depth of 5 to 7 cm.[19] In the spine, ultrasound allows medical professionals to perform percutaneous procedures
such as facet and foraminal infiltrations, enabling the visualization of spinal structures
to reduce the use of intraoperative radioscopy with favorable results.[20] While radioscopy-guided procedures are based in the extrapolation of the position
of soft tissues, such as muscles, blood vessels, and nerves, based on their anatomical
relationship to the bone structures visualized, the ultrasonography makes it possible
to visualize bones, muscle layers, nerves, and blood vessels directly, while also
eliminating, or at the very least reducing, radiation exposure for both patients and
healthcare professionals. Moreover, this method enables the visualization in real
time of the needle's insertion, facilitating the use of instruments during the procedures.[21]
This is the first publication in the literature describing the step by step use of
ultrasound to guide the in-plane, interlaminar, lumbar endoscopic approach ([Fig. 10]). The technique is feasible and viable, minimizing the risks of exposure to radiation
for the patient and surgical team, as well as making it possible to visualize bone
and ligament structures.
Fig. 10 Ultrasound Guided lumbar interlaminar in plane endoscopic approach
Conclusions
The in-plane, interlaminar, endoscopic approach can be successfully performed under
ultrasound guidance. Herein, we describe the step by step process to an unprecedented
technique of the ultrasound-guided, in-plane, interlaminar, lumbar approach for endoscopic
spine surgeries, with a smartphone-adapted endoscope and portable light source. This
technique has the potential to minimize the exposure of patients and health care professionals
to radiation while using fluoroscopy.
