Keywords
burst fracture - thoracolumbar - minimal invasive spine surgery
Introduction
Thoracolumbar burst fractures are one of the most common traumatic pathologies seen
in any trauma service. A myriad of management options exists for thoracolumbar burst
fractures (TLBFs). Management options vary from nonoperative to operative. Bracing
and bed rest are used in the nonoperative approach. The disadvantage of this approach
is continued pain, residual and possibly progressive kyphosis, and late neurological
impairment.[1]
Due to these problems, more and more patients prefer an operative intervention in
the form of open screw and rod fixation for these pathologies. The purpose of surgery
is to decompress the spinal cord, reduce any deformity, and stabilize the spine in
normal alignment. The advantage of surgical stabilization over nonoperative intervention
includes early mobilization and thereby decreased complications of bed rest. However,
not all patients can undergo surgery, for example, patients with comorbidities, and
patients with polytrauma, may not be fit for undergoing long surgical procedure.[2]
[3] Another option in surgical fixation is by minimal invasive fixation.
Minimal invasive spine surgery (MISS) techniques for spinal fixation were originally
described nearly 40 years ago by Magerl and Dick when they first placed a spinal internal
fixator in 1977 in nontraumatic cases.[4] MISS technique is becoming the favored approach recently and several retrospective
case series have been published on minimally invasive fixation techniques for spinal
trauma, most notably the use of percutaneous pedicle screw fixation without fusion.
We shall discuss an example followed by the role of various MISS techniques in the
management of TLBFs in this article.
Advantages and Disadvantages of Open Fixation
There are many advantages and disadvantages of one technique over the other. One gets
clear operative field and exposure to the vertebrae in the open surgical approach.
It is easier to decompress the thecal sac and reduce any deformity by open approach.
One can achieve fusion with open techniques, which is the ultimate goal in any kind
of spinal fixation surgery. However, these approaches are associated with a large
amount of blood loss and slow postoperative recovery. Long-term results of open fixation
are available and are highly satisfactory.
Advantages and Disadvantages of MISS Approach
MISS approach using percutaneous screws is usually associated with lesser operation
time and blood loss and at the same time it has the advantages of open approach like
restoration of sagittal alignment and stabilizing fractures. There is less damage
to the paraspinal soft tissue and hence postoperative pain is also less. Fusion cannot
be attempted in purely percutaneous techniques as bone graft cannot be placed. This
remains an important downside of these techniques as there may be implant failure
due to loosening of screw–bone interface due to the absence of fusion. However, mini-open
approaches allow access for arthrodesis. Other potential drawbacks of this approach
include loss of fixation, delayed kyphosis, and nonhealing of the fracture.3–5 There
is paucity of literature describing the long-term efficacy of percutaneous pedicle
screw fixation for traumatic thoracolumbar fractures.
There are many different types of minimally invasive techniques available, which can
be used as per the fracture type and need of decompression and/or corpectomy. We will
review the technique and results published for each technique.
Percutaneous Pedicle Screw Fixation
Percutaneous pedicle screw fixation is attempted when there is instability and direct
decompression is not required. Slight deformity can be corrected by this technique
and ligamentotaxis can also be done by distraction. It is the simplest technique and
can be done pretty quickly, which is important in patients who are medically not so
fit for long duration surgery and cannot tolerate blood loss.
Surgical Technique
After induction, the patient is positioned prone on a spine table or any other radiolucent
table as X-rays in anteroposterior (AP) view are required during the surgical procedure.
Pedicles are localized in AP view X-rays, and an approximately 1.0 to 2.0 cm skin
incision is made over the lateral aspect of the pedicle and the underlying fascia
is split. A Jamshidi needle is positioned on the lateral and superior edge of the
pedicle (2 O’clock position for the right side and 10 O’clock position for the left-sided
pedicles) and is slowly advanced into the pedicle under fluoroscopic guidance without
breaching the medial pedicular wall. A lateral X-ray can be done at this stage to
check that the needle has gone past the pedicle into the vertebral body. Following
that, a guide wire is inserted into the vertebral body through the needle, and the
needle is carefully removed. The dilator is placed through the guidewire, and tapping
is done for screw insertion. After tapping to the junction of the pedicle and vertebral
body, a cannulated percutaneous pedicle screw is placed over the guide wire into the
pedicle and vertebral body, and the guide wire is then removed after the screw has
entered the vertebral body. Proper positioning of the screw is checked under fluoroscopy.
Under fluoroscopic guidance, a longitude rod is placed in the percutaneous pedicle
screw heads through a small incision made cranially or caudally. Compression can be
performed prior to placement of locking nuts. Incisions for screws and rods placement
are irrigated and closed. The procedure can also be done under image guidance using
PAK needle (Medtronic) using navigation.
Review of Literature
Grossbach et al described a series of 11 patients who underwent posterior percutaneous
pedicle screw placement for flexion-distraction injury of the thoracolumbar junction.[5] They then compared kyphotic angulation, American Spinal Injury Association (ASIA)
grade, operative time, and blood loss with a group of 27 patients treated with open
fixation and fusion surgery. They found that there were no differences between the
open and MISS treatment groups in regard to ASIA grade and kyphotic angulation. They
did find significantly lower blood loss in the MISS group and a trend toward shorter
operative time in the MISS group (not statistically significant). One patient in each
group required hardware revision for misplaced screws. The only clinical outcome measure
used by the authors was the ASIA grade; however, all patients who underwent MISS were
neurologically intact preoperatively and remained so after surgery. The authors provided
only an average length of follow-up of 11.8 months for the MISS group and did not
disclose if any patients were lost to follow-up.
Lee et al studied 59 patients, who underwent either percutaneous (n = 32) or open (n = 27) short-segment pedicle screw fixation for stabilization of TLBF between December
2003 and October 2009.[6] They studied the Cobb angle, vertebral wedge angle, and vertebral body compression
ratio among the radiologic parameters. Visual analogue scale (VAS), the Frankel grading
system, and Low Back Outcome Score (LBOS) were measured for functional assessment.
They found that regional kyphosis (Cobb angle) showed significant improvement immediately
after surgery in both the groups and it was maintained until the last follow-up, compared
with preoperative regional kyphosis. Postoperative correction loss showed no significant
difference between the two groups at the final follow-up. In the percutaneous surgery
group, there were significant declines of intraoperative blood loss, and operation
time compared with the open surgery group. Clinical results showed that the percutaneous
surgery group had a lower VAS score and a better LBOS at 3 and 6 months after surgery;
however, the outcomes were similar in the last follow-up. They concluded that although
both groups showed favorable clinical and radiologic outcomes at the final follow-up,
percutaneous pedicel screw fixation without bone graft provided earlier pain relief
and functional improvement, compared with open fixation with posterolateral bony fusion.
Similar good results with percutaneous fixation in TLBF has been shown by another
study.[7] One hundred sixty-six patients were included in a recent meta-analyses involving
8 studies.[8] Average age was 46 years and 27% of patients had polytrauma. Average surgery time
was 91 minutes, with an average blood loss of 95 mL. Reported complications were nonhealing
fracture in three (2%), infection in one (0.6%), malpositioned screw in one (0.6%),
and hematoma in one (0.6%) at a median follow-up time of 26 months. Pain improved
by an average of 6 points after surgery according to VAS, and mean kyphosis correction
in these studies was 8.5 degrees. The authors concluded that minimally invasive, percutaneous
pedicle screw fixation is a viable option for the management of traumatic thoracolumbar
fractures in neurologically intact patients especially those who are older and/or
present with polytrauma may most benefit from this type of intervention.
Posterior Minimally Invasive Corpectomy
Corpectomy can also be performed via a mini-open posterior transpedicular or posterolateral
approach apart from the open anterior or lateral approaches. Chou and Lu reported
a series of eight patients, which included majority of patients with metastasis along
with one patient with a traumatic L1 burst fracture, who underwent a mini-open transpedicular
corpectomy.[9] A single midline posterior skin incision was made and reflected over the fascia.
Percutaneous pedicle screw fixation was done at two levels above and below the level
of the fracture using stab incisions through the fascia. An open midline fascial opening
at the level of the corpectomy was then made. Expandable tubular retractors were then
used and a complete laminectomy at the index fracture level as well as a partial laminectomy
above and below the index level was then done. A transpedicular corpectomy was done
as is done in routine open surgeries. The authors compared their small series to a
cohort of patients, including one trauma patient, who underwent open surgery. They
did not see a significant difference in outcomes or complications. However, the follow-up
was quite short in their series and was only 8 months in the patient with traumatic
fracture.
Lateral Minimally Invasive Corpectomy
Recently, mini-open lateral approaches are gaining popularity for various etiologies
like degenerative diseases. The advantage of these approaches is that they provide
direct visualization while minimizing approach-related soft-tissue dissection. Smith
et al described their experience of treating 52 patients for traumatic thoracic or
lumbar fractures with a mini-open lateral approach for corpectomy.[10] The majority of patients (94.2%) presented with traumatic burst fractures with instability
and neurologic deficit. Patients were treated with mini-open lateral corpectomies
from T7 to L4, the majority at T12 and L1, and followed for 2 years after surgery.
Supplemental internal fixation was used in all patients: 75% anterolateral plating
and 46.1% transpedicular fixation (11 [21.2%] patients with combined). Complications
included pleural effusion in one patient, intercostal neuralgia in one patient, and
dural tears in two patients. No patient required reoperation. Neurologic status improved
significantly postoperatively, with 73% of patients either completely neurologically
intact or with only slight residual deficits. While 83% of the patients underwent
follow-up at 1 year, only half of the patients had 2 years of follow-up.
Anterior Thoracoscopic Treatment of Thoracolumbar Fractures
Kim et al published their experience of treating thoracolumbar spine fractures with
a thoracoscopic minimally invasive approach.[11] The authors’ surgical technique involved a left lateral transpleural approach using
multiple portals via a thoracoscopic approach to the fractured vertebra. They then
performed a thoracoscopic vertebrectomy and reconstruction with either an expandable
cage or a bone graft. Patients with flexion distraction injuries underwent posterior
pedicle screw fixation in addition to corpectomy. The authors reported an overall
11% complication rate, which included aortic injury in one patient, conversion to
open surgery in three patients, hardware failure in five patients, and neurological
deterioration in one patient. However, these thoracoscopic techniques require a significant
amount of training, as the endoscopic image is two-dimensional.
Management Algorithm
Dhall et al proposed management algorithm in choosing an appropriate approach for
a patient with TLBF.[3] They combined decision making with Thoracolumbar Injury Classification and Severity
(TLICS) scoring system. There is no confusion regarding the management of patients
with a TLICS score of less than 4, and an external brace is recommended.
External brace and surgical fixation are equally good options for patients with a
TLICS score of 4. The minimal invasive options for such patients include either corpectomy
by minimal invasive approach via anterior or lateral route and instrumented fixation
or a posterior percutaneous screw fixation resulting in instrumented fixation and
possibly fusion. Since no fusion can be attempted in the latter approach, there is
always a concern regarding the increased risk of implant failure. Moreover, long-term
follow-up data regarding the rate of fusion following percutaneous fixation is not
yet available. It has been seen that the rate of fusion following traumatic fractures
are very high in patients with ankylosing spondylitis or diffuse idiopathic skeletal
hyperostosis. Hence, these patients can be good candidates for a posterior percutaneous
screw-rod fixation and reduction of the fracture, if their TLIC score is more than
3.[3]
Some authors have suggested to remove the pedicle screws inserted percutaneously after
fusion has occurred suggesting an “internal brace” like role of the pedicle screws.
Definite advantage of this strategy is not clear though. Moreover, the second surgery
has its own risks and morbidity.
It has been claimed that percutaneous fixation is a good option in patients with polytrauma,
as mentioned earlier. However, it has to be kept in mind that this is true only for
the surgeons who are routinely doing percutaneous fixations and take short time to
insert percutaneous screws.
In patients with a TLICS score of more than 4, standalone percutaneous posterior fixation
is not a good option as without fusion the chances of hardware failure will be very
high. It can be used to supplement open or mini-open instrumented fusion via either
an anterior/lateral or a posterior approach as described earlier in this article.
Conclusion
Minimal invasive techniques are becoming popular in the management of patients with
TLBF. However, one has to be very careful in selecting patients to be managed with
minimal invasive techniques. Patients with a TLICS score of 4 can be managed with
percutaneous pedicle screw fixation. There is no sound scientific rationale available
as of now in taking out the hardware after some time in these patients. Patients with
TLICS score of more than 4 always need arthrodesis and should never undergo percutaneous
pedicle screw fixation alone.
