Chapter 24
A Minimally Invasive Open Approach for
Reconstruction of the Anterior Column of the
Thoracic and Lumbar Spine
B. Knowles, I. Freedman, G. Malham, T. Kossmann
24.1
Terminology
Minimally invasive open anterior column reconstruction of the spine describes a surgical technique that
blends elements from both endoscopic and conventional open spine surgery. With the aid of specially designed surgical instruments the procedure is performed under direct vision through a small incision using an endoscopic set-up (Fig. 24.1).
24.2
Surgical Principle
The aim of the procedure is to restore anatomical alignment and integrity to unstable or destroyed segments
of the anterior column of the thoracic and lumbar
spine. An open minimally invasive surgical approach is
used to minimise surgical trauma and to reduce perioperative and postoperative morbidity. The technique
has been developed to combine attractive elements of
both endoscopic and conventional open surgery. The
procedure is based on the use of a table-fixed retractor
system (SynFrame) and is performed with specially
manufactured elongated surgical instruments that are
operated from outside of the patient’s body (Fig. 24.2).
Fig. 24.1. Surgery is performed under direct vision through an
open but minimally invasive approach
A thoracoscope mounted to the retractor frame is used
to illuminate the operating field and is attached to a
video camera for monitoring and teaching purposes.
Vertebral body reconstruction and augmentation with
a variety of materials and spinal canal decompression
is performed via an anterior (ventral) approach using a
mini-thoracotomy or via a mini-retroperitoneal route.
In our experience this procedure is associated with reduced blood loss, shorter hospital stay and less perioperative morbidity than conventional open spine surgery [6, 14, 15]. In contrast to endoscopic spine surgery
this procedure does not require special anaesthetic
procedures such as double-lung intubation. With an experienced and skilled surgeon operating times are
equivalent to those for open procedures [19, 21, 22].
24.3
History
Since the 1970s, the management of thoracolumbar
fractures has evolved from conservative management
to operative intervention with decompression, reconstruction and internal fixation of affected segments.
The spinal column is situated dorsally behind the
visceral cavities of the thorax and abdomen. A posterior approach for decompression and transpedicular
Fig. 24.2. Operating set-up. The SynFrame is mounted onto the
operating table and the retractors and thoracoscope are fixed
onto the ring
24
216
Thoracic/Thoracolumbar Spine – Fractures
screw and rod stabilisation has been the standard of
care for thoracolumbar fractures for some time [13].
However, 80 – 85 % of axial forces on the spine are
transmitted via the anterior vertebral column [8].
Hence, reconstruction of the axial load-bearing anterior spine has been shown to impart a biomechanical and
clinical advantage to fracture outcome [9]. How to
achieve satisfactory anterior fusion has been a topic of
great debate as conventional open spine surgery is associated with significant surgical trauma and complication rates [4, 5, 7, 9, 10, 11, 14, 15, 22].
The thoracic spine (T4 – 10) has traditionally been
accessed via a posterolateral thoracotomy. This involves a large 25-cm incision and is associated with a
significant incidence of acute postoperative pain [5],
chronic intercostal neuralgia and post-thoracotomy
pain syndromes [4]. Conventional open spine surgery
is also associated with a high incidence of other complications, such as wound infections, empyema, aortic
laceration, pneumothorax, haemothorax, chylothorax,
brachial plexus injury, Horner’s syndrome and lung
herniation [10, 11].
Similarly, open surgery in the form of a retroperitoneal thoracolumbophrenotomy has been the standard
approach for fractures of the thoracolumbar region
(T11-L3) [6]. This involves opening the thoracic cavity
along a lower rib and incising the diaphragm to peel
the peritoneal sac away from the lower thoracic spine
down to the fourth lumbar vertebra. The operative approach is extensive and entails wide costophrenic detachment.
Capener described the first anterior approach to the
lower lumbar spine in 1932 [3]. Unfortunately this open
approach is also associated with profound morbidity
[7, 19, 22].
As many of these complications were approach specific [7], less traumatic approaches for accessing the
spine became desirable. Muscle-sparing thoracotomies
have since been shown to reduce postoperative pain
[9]. Since the early 1990s “minimally invasive techniques” that utilise endoscopic technology to reduce
surgical soft tissue trauma have also emerged [20]. In
1993 video-assisted thoracoscopic surgery (VATS)
techniques were applied to the treatment of thoracic
spinal disorders. Similar endoscopic procedures were
developed for the thoracolumbar junction and lumbar
spine [12, 16, 17]. Endoscopic procedures have since
demonstrated a significant reduction in postoperative
pain, blood loss, recovery time and improved postoperative respiratory function. However, pure endoscopic
thoracic and lumbar spine approaches have required
invasive double-lumen tube intubation, increased anaesthetic monitoring and longer operative times. More
significantly, complications are more difficult to manage and surgeons experience long “learning curves”
before they feel familiar with the procedure.
In an effort to rectify the disadvantages of closed endoscopic approaches surgeons have begun to blend
minimally invasive techniques with a limited open approach. Mayer pioneered the use of mini-thoracotomy
and mini-retroperitoneal open approaches to access
the thoracic, thoracolumbar and lumbar spine for the
treatment of degenerative disorders [19, 21]. This chapter outlines our development of the treatment of fractures of the thoracic and lumbar spine by a minimally
invasive open technique and gives an overview of our
experience [14, 15].
24.4
Advantages
No extensive preoperative anaesthetic work up,
e.g. double-lung intubation, required.
Small surgical incision, i.e. mini-intercostal and
flank surgical approaches.
Direct three-dimensional intraoperative view of
spine using a stable easily adjusted retractor.
Excellent direct illumination of the operative field
by a thoracoscope.
Direct view of the anterior spine allows safer
mobilisation of blood vessels and nerves.
Faster decompression of spinal canal.
Easier reconstruction of the anterior spine column.
Reduced blood loss and transfusion requirements.
Reduced wound pain.
Lower complication rates.
Accelerated rehabilitation.
Suitable for a range of pathology including traumatic fractures, pseudoarthroses and reconstruction of vertebrae destroyed by malignancy.
24.5
Disadvantages
A “learning curve” is necessary but with experience operating times are equal.
It is more difficult to manage intraoperative complications than with conventional open approaches
but easier than with closed endoscopic surgery.
Initial financial investment in mandatory equipment is required.
24.6
Indications
The anatomical location determines whether the minimally invasive procedure is performed via a right-sided
mini-thoracotomy (T4-8; Fig. 24.3b), left-sided minithoracotomy (T9-L2; Fig. 24.3a), left-sided mini-retro-
24 A Minimally Invasive Open Approach for Reconstruction of the Anterior Column of the Thoracic and Lumbar Spine
Fig. 24.3. Male patients following left-sided (a) and
right-sided (b) mini-thoracotomies for fractures of the
11th and 7th thoracic vertebrae, respectively
a
peritoneal approach (L3-4) or minimally invasive retroperitoneal access (L4-S1). Depending on the fracture
type the overall management may include a preceding
posterior stabilisation with or without decompression.
The indications for a minimally invasive open approach to the anterior column of thoracic and lumbar
spine fractures are as follows:
T4-L5 unstable spine injuries as per Magerl classification [18]
Neurological deficit
Sagittal angulation of greater than 25°
Axial compression of greater than 50 % of vertebral
height
Multiple fractures
24.7
Contraindications
Apart from contraindications to general anaesthesia
there are no absolute contraindications for this approach. Individual consideration should, however, be
made in patients with:
Pleural empyema
Previous thoracic/retroperitoneal surgery on the
same side as access
Severe coagulopathy
Osteoporosis
b
24.8
Patient’s Informed Consent
The patient is explained the aim and benefits of surgery
and the expected postoperative course. The following
approach-specific risks are outlined:
Injury to spinal cord, spinal nerves, sympathetic
plexus
Lung contusion and/or pleural effusion necessitating
an intercostal catheter for 24 – 48 h postoperatively
Blood loss and possible transfusion-related risks
Injury to thoracic or abdominal viscera including
heart, spleen, kidney, ureter and bowel
Postoperative pain
Diaphragmatic herniation
Postoperative deep venous thrombosis, pulmonary
embolus and need for prophylactic treatment
Superficial and deep wound infections
Pneumonia
Pseudoarthrosis
Implant loosening/failure
24.9
Surgical Technique
24.9.1
Preoperative Planning
Comprehensive imaging of the spine, spinal cord and
cauda equina enables the surgeon to anticipate the pathology at surgery. Plain films in anteroposterior and
217
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Thoracic/Thoracolumbar Spine – Fractures
a
b
Fig. 24.4. a Preoperative MRI in a 46-year-old female patient
with metastatic renal carcinoma, demonstrating extensive vertebral body destruction. b Postoperative plain X-rays in this
woman demonstrate vertebral reconstruction with a Synex
cage. c Incision for the minimally invasive resection and reconstruction for metastatic renal carcinoma
c
lateral positions are followed by computed tomography
(CT) scanning in multiple planes, which is particularly
useful for imaging bony structures. Magnetic resonance imaging (MRI) is useful in patients with neurological symptoms, in those unable to cooperate with
clinical assessment and in patients with spinal canal
compromise on CT scan (Fig. 24.4a).
The patient is positioned on the left (for upper thoracic intervention) or on the right side (for the thoracolumbar junction and lumbar spine), with the surgeon
standing at the patient’s back. The site for the surgical
incision is selected according to the level of the affected
vertebra [15].
24.9.2
Upper Thoracic Spine (T4-8) and the Thoracolumbar
Junction (T9-L2)
Anterior reconstruction of the upper thoracic spine
(T4-8) is performed via a right-sided mini-thoracotomy (Figs. 24.3b, 24.4c). The thoracolumbar junction
(T9-L2) is accessed via a left-sided mini-thoracotomy,
which allows a retroperitoneal approach down to the
level of the second lumbar vertebra via a minimal incision in the diaphragm (Fig. 24.3a). For these different
access levels (as well as for the lumbar spine and lumbosacral junction) one assistant on the opposite side to
that of the primary surgeon is required. A highly
trained scrub nurse may be capable of fulfilling this
role. No intensive anaesthetic intervention such as double-lung intubation is needed. Induction prophylactic
antibiotics and dexamethasone are administered routinely. In patients with neurological injury we give
methylprednisolone as per the NASCI III protocol [1].
Controlled hypotension is maintained at a MAP of
75 – 80 mm Hg. The cellsaver is utilised.
Once the patient is correctly positioned the affected
vertebra is localised with an image intensifier. A 6- to 8cm incision (independent of location) is then made and
underlying muscles are dissected bluntly. After opening the thoracic cavity the lung is identified and is then
briefly disconnected from the ventilator so that it can
be gently pushed aside to allow space for the surgery.
The lung is protected with a moist surgical towel and
ventilation to the lung is recommenced. The retractors
are placed onto the table-fixed SynFrame (Stratec Medical, Switzerland) and adjusted according to the surgeon’s requirements. The SynFrame is a stable, adjustable ring system fixed sterile by two adjustable arms
onto the operating table (Fig. 24.2). The permanent sta-
24 A Minimally Invasive Open Approach for Reconstruction of the Anterior Column of the Thoracic and Lumbar Spine
bility of the operating field is a major advance and allows the surgeon to operate without further manipulations of the surgical field. A thoracoscope is inserted
via a separate incision with an 11.5-mm-diameter trocar. This incision is later used for insertion of an intercostal catheter that remains in place for 24 – 48 h postoperatively. An endoscope is secured onto the frame to
illuminate the operating field and is adjusted directly
by the surgeon. As only the surgeon has a direct view of
the operating field the endoscope is attached to a video
screen so that nurses, assistants and trainees can observe the procedure. The vertebral reconstruction procedure can then commence.
24.9.3
Lumbar Spine (L3-4)
The lower lumbar spine (L3/4) is accessed via a left-sided minimally invasive pure lumbotomy. The affected
vertebra is identified with the image intensifier and its
projection is marked laterally on the flank. A 6- to 8-cm
skin incision is then made and is followed by dissection
of the three layers of the abdominal wall along their fibres until the retroperitoneal space is reached after
penetrating the transversus abdominis fascia and muscle. The peritoneal sac is dissected off the fascia bluntly
by a finger or a wet sponge mounted on a stick until the
psoas muscle is reached. This potential space is kept
open using retractors mounted on the SynFrame ring.
Care should be taken not to damage the ureter, which
can be gently pushed aside together with the peritoneum. The psoas muscle is mobilised in part to enable the
surgeon to reach the lumbar vertebral bodies. Tilting of
the table towards the surgeon can facilitate this. Muscular patients may require splitting of the psoas muscle
along its fibres to reach the lateral aspect of the vertebral bodies. Attention must be paid to the lumbar plexus embedded deep within the psoas muscle and the iliohypogastric and ilioinguinal nerves crossing the surgical field.
24.9.4
Lumbosacral Junction (L5-S1)
The lumbosacral junction is accessed via a prone minimally invasive transperitoneal route. The abdomen is
opened in the midline below the navel. The table is then
tilted head down (Trendelenburg position) to allow the
intestines to be pushed upwards. The peritoneum is incised on the left side of the aorta. It is advisable to isolate and secure the aorta and both iliac arteries. Access
to the lumbosacral junction is then accomplished from
the left side behind the anterior longitudinal ligament.
24.9.5
Reconstruction of the Anterior Column
After exposing the spine laterally, the level of the affected
vertebra is identified with the image intensifier and the
adjacent disc spaces are marked with K-wires. The location of the anterior longitudinal ligament and spinal canal can be calculated from the position of the K-wires. In
most cases the overlying segmental vessels of the affected
vertebra need to be clipped. The sympathetic chain is
identified and where possible preserved. The abdominal
aorta lies in front of the affected vertebra and directly anterior to the anterior longitudinal ligament. The ligament
is not resected and serves as a safety marker for protecting the aorta and inferior vena cava on the lower aspect
of the operating field. The vertebral discs are cut with a
specially designed long-handled knife. After their removal the corresponding vertebral end plate is cleaned
with specialised curettes (Synthes Spine USA). Care is
taken not to penetrate the end plates. The vertebral body
is then removed in part or completely using long osteotomes and rongeurs (Synthes Spine USA) and again special
care is taken to preserve the anterior longitudinal ligament. For reconstruction of the void space, various materials such as autologous iliac crest bone grafts, allografts
and cages (Synex; Stratec Medical Switzerland) filled
with bone from the corporectomy have been used. Additional iliac crest harvesting or acrylic cement is occasionally used to fill the cage. In the last 3 years we have mainly
utilised cages as they avoid problems of donor site morbidity (with autologous iliac crest bone graft harvest)
and other autoimmune obstacles (with allografts).
24.10
Postoperative Care and Complications
The typical postoperative course for a patient is:
Immediate extubation after operation.
Low molecular weight heparin thromboembolic
prophylaxis.
Chest tube removed after 24 – 48 h.
Mobilisation and physiotherapy to commence on
the first postoperative day. Once the chest tube is
removed the patient can commence rehabilitation.
Anteroposterior and lateral X-rays of the operative
site on the first postoperative day.
CT assessment prior to the patient leaving hospital
to check the exact location of the cage and for
quality control purposes.
Return to work after 6 – 12 weeks.
Potential complications of the procedure itself include:
Poor patient positioning resulting in difficult access,
longer operating time and potential inaccessibility.
219
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Thoracic/Thoracolumbar Spine – Fractures
Segmental vascular injury causing bleeding which
compromises the visual field.
Damage to major thoracic or abdominal vessels
may necessitate conversion to conventional thoracotomy and/or laparotomy.
Injury to heart, lungs or abdominal viscera.
Dural tear.
Peritoneal tear.
Displacement of bone or disc into spinal canal
during corporectomy and/or grafting.
Suboptimal fracture reduction.
Other potential postoperative complications are:
Haemothorax or pneumothorax requiring thoracotomy.
Infection of wound, body cavities or prosthesis that
may require debridement and removal of implant.
Implant failure or displacement.
Ileus.
Recurrent pleural effusions.
24.11
Results
We initially reported a series of 65 consecutive patients
(28 women, 37 men) who were treated with minimally
invasive open surgery to the anterior column between
July 1999 and July 2000 [15]. Subsequently, by early 2004
we have gained additional experience with more than
200 minimally invasive operations on the thoracic and
lumbar spine using minimally invasive open approaches. In 4 patients in our first series [15] surgery
was performed for treatment of a pseudoarthrosis following previous intervention and in 6 patients for metastatic destruction of a single vertebra in the thoracic or
lumbar spine (Fig. 24.4a). The remaining 55 patients
had traumatic injuries. Of these, 30 patients had isolated spine injuries whereas 25 patients had additional
(sometimes multiple) injuries to the head (n = 10),
thorax (n = 9), pelvis (n = 4) and extremities (n = 12).
Traumatic injuries to the spine were categorised according to Magerl’s classification [18]. Thirty-four patients
had type A, 14 had type B and 7 had type C fractures.
There were 9 fractures of the thoracic spine (T4-10),
35 fractures involving the thoracolumbar junction
(T11-L1) and 11 fractures of the lumbar spine (L2-4).
Out of the 65 patients, 29 received stabilisation with
a posterior Universal Spine System (USS; Synthes, Switzerland) prior to the anterior spine surgery. In 8 patients a right-sided mini-thoracotomy was performed
to access the midthoracic spine (T4-8), a left-sided
mini-thoracotomy to reach the thoracolumbar junction
(T9-L2) was used in 50 patients and a mini-retroperitoneal approach was used in 7 patients for lumbar spine
intervention. Spinal clearance was performed in 11 pa-
tients via anterior mini-thoracotomy or retroperitoneal
approaches. Autologous iliac crest bone was harvested
in 11 patients, autologous spongiosa in 12 patients, femur allografts in 2 patients and iliac crest allografts in
2 patients. Expandable (Synex) cages were used for vertebral reconstruction in 38 patients. The cages were
filled with spongiosa from the corporectomy and in 7
patients additional autologous spongiosa was harvested from the iliac crest.
The operating time (OT) from incision to closure was
recorded. It must be emphasised that this time included
the learning period of using this technique. The mean
OT was 170 min (range 90 – 295 min) but this varied depending on the magnitude of the intervention. For a
left-sided mini-thoracotomy (n = 42), the mean OT was
141 min. Addition of spinal clearance and iliac bone
grafting saw the mean OT increase to 167 min. A rightsided mini-thoracotomy (n = 7) averaged 152 min. An
additional 60 min were needed in cases that required
spinal clearance and another 20 min were require for iliac crest bone graft harvesting. The mean OT was
165 min for the mini-retroperitoneal approach (n = 10)
and 194 min when spinal clearance and iliac crest bone
harvesting were required. With increased experienced
our operating time has improved to approximately
120 – 140 min.
No patients required conversion to an open procedure and no complications related to the minimal access technique and neither visceral nor vascular injuries were observed. One patient with multiple metastases died intraoperatively due to an acute thromboembolic event. Four cases of mild postoperative ileus that
settled with conservative management were noted. No
patients developed intercostal neuralgia or post-thoracotomy pain syndromes. Most patients reported mild
pain at the site of intervention but in all cases this resolved completely after several days. No postoperative
wound infections or deep venous thrombosis were recorded. Patients with isolated spinal pathology were
discharged from hospital after an average of 13 days
(range 2 – 30 days). Patients with additional injuries
stayed in hospital for an average of 20 days (range
2 – 86 days). The mean blood loss was 912 ml. The subgroup requiring spinal clearance (n = 11) had a greater
mean blood loss of 1,716 ml (range 300 – 5,000 ml). This
is less than in conventional open procedures and similar to endoscopic-based reconstructions of the anterior
column [2]. Only 7 of the 65 patients required blood
transfusions.
24.12
Critical Evaluations
Minimally invasive but open surgery for repair of the
anterior thoracic and lumbar spine column has only re-
24 A Minimally Invasive Open Approach for Reconstruction of the Anterior Column of the Thoracic and Lumbar Spine
cently been described and as such there are few published reports of the technique. Nevertheless, our published series of 65 prospectively collected minimally invasive open procedures demonstrated a marked reduction in postoperative pain and a faster return to function for the patient compared to historical controls
[15]. The minimally invasive techniques avoided the
access-related morbidity associated with conventional
open approaches in that postoperative pain, bleeding
and surgical trauma were greatly reduced. There is also
less inadvertent intraoperative organ injuries than has
been reported with endoscopic approaches [12, 16].
This is largely due to the fact that the open, minimally
invasive procedure enables the surgeon to directly visualise the operative field in three dimensions. This direct
visualisation helps with vessel and nerve preparation,
in performing a corporectomy and with spinal clearance. This view of the surgical field and the physical
verification of events facilitated by open surgery is
more familiar to surgeons not experienced with the
magnified two-dimensional images in pure endoscopic
procedures. The learning curve with the procedure is
consequently rapid, and potentially serious complications and extended operation times are more easily
avoided. Subsequently, we have performed more than
200 minimally invasive but open approaches for reconstruction of the anterior column of the thoracic and
lumbar spine. The described approaches offer distinct
advantages as compared to “pure” endoscopic or conventional open spine surgery and have become the
standard method for anterior reconstruction of the
thoracic and lumbar spine at our institution.
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