Pre-operative Hook-wire Localization of Thoracic Spinal Level for Intraspinal Pathology Requiring a Single Level Laminectomy-Juniper publishers
JUNIPER PUBLISHERS-OPEN ACCESS JOURNAL OF HEAD NECK & SPINE SURGERY
Abstract
The accurate localisation of the levels of the
thoracic spine is important to minimise surgical trauma to the spine and
soft tissue, as well reduce the possibility of spinal instability
especially if bone is removed extensively to enable better exposure. The
availability of techniques to minimise the need for exploration of
multiple levels would go a long way in overcoming these problems. We
reviewed other presently employed methods of localisation such as
traditional intraoperative fluoroscopy, skin marking using radio-opaque
material and dye, and computed tomography (CT) or magnetic resonance
imaging (MRI) based spinal navigation system. We describe here a method
of pre-operative marking of thoracic spinal level using hook-wire under
CT scan control which is a simple technique for accurate identification
of the level for surgery. The patients are placed prone on the CT couch.
Following the performance of scouts, axial images using a spiral scan
(5mm thickness with a pitch of 3) are performed. The level of the
pathology is then localised. This is followed by placement of a
hook-wire under the lamina of the vertebral body or the interspinous
ligament. Final confirmation was obtained by repeating the CT.
Intraoperatively, the vertebral target was identified easily and
immediately. No errors and complications related to the technique were
observed. This technique is employed successfully in our institution for
the removal thoracic intraspinal pathology that requires only a single
level laminectomy. This method immediately and accurately identifies the
desired spinal level and minimizes the operative time.
The accurate localization of a spinal level is
important in any spinal surgery. The importance of this is not only to
localize the pathology (intradural or extradural) but also to minimise
surgical trauma to the spine and soft tissue, as well as reduce the
possibility of spinal instability especially if extensive bone removal
is required to expose the pathology. The availability of techniques to
minimise the need for exploration of multiple levels would go a long way
in overcoming these problems.
Many surgeons use traditional intraoperative
fluoroscopy as the preferred method of identifying the vertebral level
by counting the vertebra beginning from cervical or lumbarsacral
vertebra. When using this technique in identifying thoracic vertebra
levels becomes difficult, due to the superimposed scapular shadow and
ribs.
To overcome this problem, techniques such as skin
marking using radio-opaque material and dye marking using methylene
blue, patent blue V dye or carbon had been used [1-3].
With the advancement in imaging techniques computed tomography (CT) or
magnetic resonance imaging (MRI) based spinal navigation is becoming
popular method for identifying the vertebral target [4,5].
Unfortunately, spinal navigational system is expensive and not
available in most neurosurgical centres. We would like to describe a
method of pre-operative marking of thoracic spinal level using hook-wire
under CT scan control. The hookwire technique are used for preoperative
localization of lesions that are deep, small, or located in an organ
whose shape and position may change with the position of the patient.
This technique is intended to help the surgeon find the lesion during
surgery, thus allowing minimally invasive treatment.
CT-guided hookwire placement had been widely used for
preoperative localization of breast microcalcifications and nonpalpable
breast nodules [6].
The technique has also been used for preoperative localization of
pulmonary nodules that are too small for percutaneous needle biopsy,
deep osteoid osteomas, hepatic lesions, infratemporal fossa foreign
bodies and deep intramuscular hemangiomas [7-9].
The aim of this paper is to describe a simple technique that providing
accurate identification of the vertebral level for intradural or
extradural lesions of the thoracic spine.
The placement of the hookwire is done on the morning
of surgery or a day prior to surgery. The patients were taken to the
radiology department for the procedure and the hook wire placement was
done under CT fluoroscopy (Siemens Somatom Plus, Erlangen, Germany).
The patient is placed in prone position on the CT
scan couch. A temporary radio opaque skin marker is secured to the skin
just lateral to the spinous process of the vertebra corresponding to the
level of pathology which is localized based on previously performed MRI
sagittal scan. A lateral scout CT scan is performed.Axial images using a
spiral scan (5mm thickness with a pitch of 3) performed .The level is
confirmed counting the vertebrae beginning from cervical or lumbarsacral
levels. The level of pathology is again conformed from the previous MRI
and the spinal lamina to be marked identified.
After thorough skin cleaning, local anaesthetic is
infiltrated. The hookwire is then placed vertically over the lamina of
the vertebral body or within the interspinous ligament (Figure 1a & 1b).
The final conformation is obtained by repeating the CT scan. The level
at which the hookwire is placed is clearly recoded in the case note.
Then the hookwire is cut 3cm above the skin and secured in placed with
gauze.
At surgery, patient is placed on prone position under general anaesthesia and the hook wire is exposed (Figure 2a).
The patient is cleaned and draped. A midline skin incision is done at
the site of the hookwire and the dissection is continued along the wire,
care is taken not to burn the wire if monopolar diathermy is being used
for the dissection. Once the tip is reached and the lamina is
identified, the hookwire is removed (Figure 2b).
The dissection is continued until the entire lamina is exposed and
adequate exposure is archived. The planed laminectomy is then performed
and excess to the pathology archived (Figure 3a & 3b).
This technique had been used in 13 patients
undergoing surgery for single level thoracic spinal lesion (intradural
and extradural extramedulary lesion) located between T1 to T10. In all
except one patient we were able to successfully remove the lesion using a
single level laminectomy based on hook wire localization. The
identification of level of lesion had been accurate with shorter
operative time. There was no complication encounter using this
technique.
In the single patient in whom this technique was
unsuccessful, the patient was obese and we had problems in inserting the
wire. The operation required an extension of the laminectomy into the
next level to identify and remove the lesion.
Intraoperative use of X-ray for localization of
spinal vertebra level for intraspinal pathology had been a standard
practice in most spinal surgical centers. In thoracic vertebra level,
counting the level on lateral intraoperative fluoroscopy had been made
difficult by the scapular shadows. The use of intraoperative fluoroscopy
poses drawbacks such a prolonged operating time and exposure to
ionizing radiations. To avoid these problems, other reliable techniques
had been used. Paolini et al. [2]
used methylene blue dye injection to the tip of the spinous process
rather than the skin surface; they virtually eliminated the risk of
error. The advantage of this technique is minimally invasive with
markedly reduced operation time and allows identification of the marked
vertebra through immediate, visual and coloured information. The
limitation of the technique, is unwanted diffusion of the dye toward
adjacent spinous processes but in their experience, it was avoided by
taking care not to drive the needle into the interspinous ligament and
injecting no more than 0.5ml of blue dye [2].
MRI-based technique involves preoperative application
of skin markers. Several variants of this technique had been reported,
each proposing a different kind of skin marker such as capsule filled
with halibut liver oil, longitudinal grids of oily substance and
adhesive disposable skin markers [1,10,11]. This technique has its own limitation which is pointed out by Rosahl et al. [1],
that obesity, heavy skin folding and thoracic hypermobility make the
procedure unreliable because of the skin shifting, which occurs while
the patient is being positioned [1].
The authors recommended that application of markers in prone position
would decrease the error. Even by doing so, minimal shift of these
markers during positioning for surgery would shift the marker over the
adjacent spinous processes which would cause an inaccurate laminectomy
being done.
Spinal-navigation systems weather MRI-based or CT
based is being used in many centres, this technique requires expensive
equipment, extra-time in preparing the patient and the overall cost of
surgery increased [4 ,5]. The use of hookwire for spinal level marking had only been reported by Lesoin F et al. [12]
in 1986.They described the technique for localization of spinal level
for dorsal disc pathology but failed to mention the success rate of this
technique [12].
We used hookwire marking for localising the thoracic
spinal level for intraspinal pathology which requires a single level
laminectomy. We found this technique simple, fast and more reliable than
the other non-navigational localizing methods. By marking the lamina or
spinous process itself, rather than the skin surface, we virtually
eliminated the risk of error in identifying the desired laminectomy
level. This technique is also minimally invasive with limited tissue
trauma. We visually eliminated the use of ionizing radiations
intraoperatively. Hence, the overall operation time is markedly reduced.
Potential limitation to this technique includes
dislodgement of the hookwire, breakage of wire during dissection using
monopolar diathermy and infection. These problems can be avoided by
attention to sterility during the insertion of wire and ensuring that
the wire is well plastered down to the skin to avoid dislodgment. Dural
puncture is another problem if the operator is not careful. In our
experience, we did not encounter any of these problems.
This method immediately and accurately identifies the desired spinal level and minimizes the operative and anesthetics time.
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