Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 70 ppt

Anterior vs Posterior Surgery vs Combined Surgery The classic surgical management of neuromuscular scoliosis comprises a single posterior spinal fusion.. Severe Rigid Spinal Deformities

Figure 4 Luque-Galveston fixation

aEntry point of iliac fixation at the posterior superior iliac spine (PSIS).bBending rod for Galveston fixation comprises

two bends, one 90° and one 45° in two different planes.cContouring of the rod to adapt to the sagittal profile.d

Luque-Galveston fixation for neuromuscular scoliosis

are crucial for the unit rod and Galveston techniques as this will determine if the

pelvis will be leveled after the reduction maneuver For severe pelvic obliquity a

maximal width (MW) segmental pelvic fixation has also been described and

shown to be effective [2] MW pelvic fixation comprises a pedicle screw inserted

in a Galveston fashion down the iliac wing 1 cm above the sciatic notch As an

added lever arm to correct the pelvis, a sublaminar hook pushes or pulls on an

ili-osacral screw, as described by Dubousset [31] The construct has a maximal

The MW fixation allows for a very stable sacropelvic fixation

width fixation across the lumbosacral junction and on the AP and axial imaging

has an “M&W” configuration; hence the eponym MW fixation ( Fig 5 ) The hook

placement obviously is dependent on the obliquity of the pelvis; hence the hook

facing down is on the iliosacral screw of the elevated hemipelvis side while the

hook going up is on the iliosacral screw on the lower hemipelvis Great forces can

be exerted across these iliosacral screws, thus allowing significant correction

Figure 5 MW fixation

The drawings illustrate the placement and appearance of MW fixation The pelvis anchorage points comprise an iliac

screw (1) and iliosacral screws (2) which have downgoing (3) and upgoing hooks (4) to provide leverage in opposite directions to level the pelvis Inset view of pelvis illustrates placement of screws Note the iliosacral screws end in the

promontory of S1 Note the location of the hooks harnessing the added lever arm of the iliosacral screws

Figure 6 Cantilever correction with MW sacropelvic fixation

aThe initial step of reduction is to achieve solid distal pelvic fixation In this illustration MW pelvic fixation is achieved Rods must be as perpendicular as possible to the pelvis.bThe second step is to cantilever the proximal rod to the spine, thus achieving initial correction of the pelvic obliquity.cThe third step consists of correcting if needed the residual pelvis obliquity by distracting down via the hook resting on the iliosacral screw on the higher hemipelvis In contrast, on the lower hemipelvis, the hook will pull up (compressing) the iliosacral screw proximally to level the pelvis

Allograft fusion is well accepted for fusion

of neuromuscular scoliosis

The general consensus is that an allograft is a well-accepted bone grafting

substi-tute for spinal fusion in neuromuscular scoliosis [52] Many factors have led to

this consensus In part the pelvises of neuromuscular patients tend to be small,

never providing enough bone Furthermore they are often used as a fixation

point It is therefore standard treatment to supplement a local bone graft

(spi-nous process, facets and lamina) with an allograft.

Anterior vs Posterior Surgery vs Combined Surgery

The classic surgical management of neuromuscular scoliosis comprises a single

posterior spinal fusion Undertaking anterior spinal surgery has been associated

with an increased morbidity especially in NMD patients [12] Indications for

anterior spinal surgery are threefold:

) skeletal immaturity

) rigidity of the deformity

) risk of non-union

The literature remains unclear on the absolute indications because of the added

morbidity.

Patients at risk of crank-shafting should undergo additional anterior fusion

The general principle is that patients who are at risk of a crankshaft

phenome-non (i.e., progressive rotation of the anterior column around the fused posterior

elements) after posterior fusion should undergo an anterior growth arrest and

fusion Keeping in mind that patients with neuromuscular disorders have altered

growth patterns [16, 25], patients younger than 10 years of age, Risser 0, with

open triradiate cartilage, and who have not yet reached their peak growth

veloc-ity are at risk of crankshaft It is recommended for these patients to proceed with

an anterior spinal fusion if they can tolerate the surgical insult.

Anterior release may be necessary for the correction

of rigid deformity

The second indication for anterior surgery is the need for an anterior release

to allow the pelvis to be leveled If one is unable to correct the pelvis manually by

bringing it within 10° of the perpendicular of the trunk by applying external

forces over the iliac crests and the trunk with the patient in a prone position with

the legs hanging free in flexion, then it is recommended that an anterior release

should be done or even an apical vertebrectomy considered Curve flexibility can

be assessed with traction films and supine bending films However, in some cases

of severe spasticity, only intraoperative examination and imaging with the

patient under general anesthetic will provide curve flexibility ( Case Study 4 ).

Patients at risk of non-union (e.g myelodysplasia) should undergo interbody fusion

Thirdly, anterior spinal fusion should be also considered when the risk of

non-union is elevated The typical example is that patients with myelomeningocele

with deficient posterior spinal elements should systematically have an anterior

interbody fusion [45] The biology of posterior grafting remains in tension

mode, while anterior grafting is in compression mode, which favors a solid

fusion Achieving solid anterior fusion can be crucial, as about half of

myelome-ningocele patients with posterior spinal fusion [20] will develop a deep posterior

a b

c

d

e

f

Case Study 4

This is a 16-year-old boy with a T10 myelomeningocele with a progressive severe coronal and sagittal spinal deformity (a–d) His deformity led him to have recurrent pressure sores over the gibbus, constant GI problems secondary to the increased abdominal pressure, as well as severe pulmonary restrictive disease Surgical management required preopera-tive gravity halo traction and aggressive chest physiotherapy to minimize perioperapreopera-tive respiratory collapse The patient

then underwent a kyphectomy with a retroperitoneal extraperiosteal resection of the proximal kyphotic segment ( e) allowing a maximal distal fixation point To minimize distal instrumentation, pull-out Dunn-McCarthy presacral rods were used supplemented with far lateral pedicle screws almost behaving as anterior vertebral screws Once the proximal

bone was excised (yellow shadow), the deformity was corrected in a cantilever maneuver closing the gap (f) and correct-ing the deformity

g h

Case Study 4 (Cont.)

The patient then had an anterior structural tibial graft inserted via a thoraco-abdominal approach to ensure solid

ante-rior spinal fusion across the residual kyphosis (g,h)

spinal infection with the possible necessity of hardware removal [27, 30, 38].

Finally, patients with severe kyphotic deformities requiring significant

correc-tions should also have anterior structural bone grafting (tibia or ribs) to prevent

the deformity from recurring It is preferable to achieve sagittal balance with

nor-malization of the sagittal alignment but moderating the urge to overcorrect the

kyphosis.

Single anterior only surgery

is indicated only in minor curves without the need for sacropelvic fixation

Single anterior only spine surgery can be done for specific curve patterns and

patients with specific contraindications to posterior surgery, i.e., chronic

infected wounds The surgical indications that Sponseller recommends for

ante-rior spinal fusion in myelomeningocele are: a relatively small supple curve of less

than 70 degrees with no need to extend the fusions down to the pelvis [44].

If combined anterior and posterior surgery is required, the ideal timing of the

anterior surgery is still controversial [10] Anterior surgery can be done on the

same day or staged with a period of halo traction, achieving some gradual

cor-rection over time Gravity halo traction [5] and intraoperative halo femoral

traction [17] are options Irrespective of the type of traction, close neurological

examination including cranial nerve testing, muscle strength in the upper and

lower extremities, sensory examination and long tract signs is mandatory to

avoid injury to the spinal cord Complications in staged surgery have been found

to be higher and some advocate same day front and back surgery [10].

Severe Rigid Spinal Deformities

Some of the neuromuscular spinal deformities can be severe, and particularly

rigid spinal osteotomies, vertebrectomies, or even kyphectomies may be

required to rebalance patients When one needs to proceed to a kyphectomy, the

neuromuscular kyphoscoliosis has reached its end stage disease and is an

exam-ple of what can happen with neuromuscular curves The severe spinal deformity can lead has led to significant loss of spinal column height, resulting in signifi-cant disability and morbidity This child’s kyphotic deformity was not addressed

at an early age, as there was a false perception that delaying surgical manage-ment would allow for better pulmonary function The problem is that kyphosis will always progress in this population and that the complexity of the case will only increase There are two types of kyphosis in myelomeningocele The more

classic collapsing C shape type kyphosis that can be addressed by pedicle

sub-traction type osteotomies [27] is classically performed in the newborn and young infant by removing the ossific nuclei The second type is described as Rigid S shape kyphosis

requires spinal column

resection

a so-called rigid S shape kyphosis [21] due to the associated thoracic lordosis

above the lumbar kyphosis To address such a deformity a spinal column resec-tion is required.

When planning a spinal resection, one must achieve solid fixation above and below the resection Distal fixation can be problematic if distal vertebrae have been resected, thus keeping as many distal spinal vertebrae as possible, to maxi-mize distal spinal anchorage points Pelvic/sacral fixation is best achieved with a

modified Dunn-McCarthy presacral rod [28] augmented with pedicle screws in

the most distal vertebral bodies The entry points for these screws tend to be much more lateral (in the remnant pedicle) and must converge much more than the usual pedicle screws As the Dunn-McCarthy rods are anterior to the sacrum and sacral alae, one is able to exert a significant corrective force across an osteo-porotic pelvis and sacrum With such a construction one is able to flex in a canti-lever fashion the distal spine and pelvis, thus correcting the deformity Proximal fixation can be performed with sublaminar wire, hooks or pedicle screws

Shar-rard first described this as apical vertebral resection [43] We tend to identify and

isolate the dural sac [40] If it poses a physical barrier to our dissection, we ligate the sac and transect the cord; however, we prefer to spare it by mobilizing it and then transecting the roots We then proceed in an extraperiosteal dissection just

as one would do a classic anterior approach We identify the disc levels, then, by Apical vertebral resection is

technically very demanding

and associated with

significant blood loss

using a blunt dissection we reflect the great vessel and the peritoneum off of the spine from either side We then ligate the segmental vessels, and reflect anteriorly the peritoneum and the abdominal contents This is facilitated by the prone posi-tion as the abdominal contents fall forward Once the vertebrae identified have been circumferentially dissected, we place blunt retractors around the spine and proceed to cut the vertebra at a bony surface with an oscillating saw above and below the planned resected spine, thus providing bony apposition As one does this, significant blood loss is encountered, and it persists until the two ends of the vertebrectomy are reapproximated Therefore the spinal anchorage points must already be in place and the actual kyphectomy is done last ( Case Study 4 ).

Spinal Cord Monitoring

Spinal cord monitoring

remains mandatory though

not always feasible

In patients with neuromuscular scoliosis, one sometimes cannot have any form

of intraoperative spinal monitoring due to inadequate somatosensory evoked potential (SSEP) or even motor evoked potential (MEP) and one must rely on the Stagnara wake-up [14, 50] Sometimes, the wake-up test is also not feasible if patients are uncooperative.

The wake-up test

is often unreliable

In such situations we tend to keep all our instruments sterile on the back table until well after the surgery has ended and until the patient has moved all limbs.

If there is a problem then we do not need to wait for the resterilization of the instruments and proceed to immediate hardware removal or decrease the amount of correction.

mity and the greater the deformity will be.

Pathogenesis. The pathophysiology of neurogenic

spinal deformities remains unclear.

Clinical presentation The classical spinal

deformi-ties encountered in NMD consist of kyphoscoliosis,

scoliosis, kyphosis, lumbar hyperlordosis and pelvic

obliquity On taking the history one needs to find

clues, which may confirm the presence of

neuromus-cular scoliosis Clues suggestive of neuromusneuromus-cular

scoliosis are birth anoxia, delayed developmental

milestone, acquired or familial neuropathies and/or

myopathies, spinal deformity before the age of

7 years, or a painful scoliosis A systemic examination

is mandatory of head to toes and further clues can be

found confirming the presence of neuromuscular

spi-nal deformity Neurocutaneous skin markings such as

hairy patches or midline nevi (or vascular lesion) can

be superficial clues to intradural pathologies If pelvic

obliquity is present, one should assess whether its

or-igin is: suprapelvic, intrapelvic, or infrapelvic

Dubo-usset saw the pelvis as the 6th lumbar vertebra and

the pelvis being a simple extension of the scoliotic

deformity resulting in pelvic obliquity In contrast,

in-frapelvic obliquity is secondary to hip contractures,

which result in pelvic obliquity The contractures,

which drive the pelvic obliquity, tend to be abduction

or adduction hip contractures It is crucial to know if

the patient is a walker, sitter (wheelchair bound) or

non-sitter In the walker, one must determine gait

pattern and mode of ambulation, as it determines the

extent of instrumented fusion (whether or not to

in-clude the pelvis) The neurological examination

needs to be thorough: Flaccid faces can be

sugges-tive of subtle myopathies while asymmetrical shoe

size can be a subtle sign of syringomyelia.

Diagnostic work-up. Confirming the diagnosis of

neuromuscular scoliosis is best done in

multidisci-plinary fashion by including the neurologist and

geneticist Patients with neuromuscular scoliosis

tend to have severe deformities with associated

pa-of ventilation dependency Cardiac dysfunctions

can be seen in the muscular dystrophic patients A large proportion of patients with neuromuscular scoliosis have concomitant dietary problems

lead-ing to malnutrition which may require

supplemen-tation Part of the preoperative imaging, supine bending films and/or traction films should be ob-tained to guide surgical planning Any scoliotic pa-tients with a hint of neurological signs or symptoms

or with neuroectodermal skin lesions must have an

MRI scan of the entire spine taken (occiput to

sa-crum) to assess any presence of intradural lesions:

syringomyelia, tethered cord, or spinal tumor.

Non-operative treatment The natural history of neuromuscular spinal deformity is one of curve pro-gression irrespective of etiology Factors influencing curve progression are as follows: age of onset of

NMD, severity and rapidity of weakness, evolving or static neuromuscular disease, skeletal maturity, am-bulation status, and severity of curves Their curve progression has been reported to be from 7° to 40°

per year In patients with cerebral palsy, because their onset of puberty is highly variable (8 – 20 years), it is difficult to quantify the risk of curve progression and

it has been shown that their scoliosis does progress into adulthood Bracing for neuromuscular scoliosis

is “functional bracing” It provides an external

sup-port to the spine, allowing some patients to be more functional Bracing has not been shown to prevent curve progression in the neuromuscular scoliosis.

Operative treatment. In contrast to idiopathic

sco-liosis, neuromuscular deformities tend to alter the patient’s functional status by interfering with their

ability to sit, stand, and walk This loss of function is the more common indication to proceed with sur-gical management as all of these curves progress.

One must prepare for and expect longer surgical

times with greater blood loss Surgical planning is crucial not to miss the associated sagittal

deformi-ties The majority of these patients will need the postoperative intensive care unit mainly to monitor

for fluid shift and respiratory status The cornerstone

of the surgical management of these types of curve

is to achieve perfect spinal balance both in the

coronal and sagittal planes Classically these

patients do not have compensatory mechanisms

(muscle tone, intact proprioception) to rebalance

themselves Their curves tend to be long and they

often have associated pelvic obliquity necessitating

long fusions to the pelvis Treating

neuromuscular-spinal deformity requires a vast knowledge of pelvic

and spinal fixation techniques such as the Luque-Galveston techniques, unit rods, and MW pelvic fix-ation One should apply all the modern principles of

spinal deformity correction to these cases in order to minimize the extent of the approach, to maximize their postoperative function (walking capacity or sit-ting balance) and to achieve a successful outcome with no postoperative immobilization.

Key Articles

Mazur J, Melelaus MB, Dicksen DR, et al ( 1986) Efficacy of surgical management for scoliosis in myelomeningocele: correction of deformity and alteration of functional sta-tus J Pediatr Orthop 6:568

Paper summarizing the impact of spinal surgery on the myelomeningocele patient

Askin G, Hallett R, Hare N, Webb JK ( 1997) The outcome of scoliosis surgery in the severely physically handicapped child: An objective and subjective assessment Spine 22(1):44–50

A broad summary of the subjective impact of spinal surgery on patients with neuromus-cular scoliosis

Lonstein J, Akbarnia B ( 1983) Operative treatment of spinal deformities in patients with cerebral palsy or mental retardation J Bone Joint Surg Am 65:43–55

Landmark paper providing insight into management of neuromuscular scoliosis

Winter S ( 1994) Preoperative assessment of the child with neuromuscular scoliosis Orthop Clin North Am 25:239–245

Thorough review and clear recommendations for preoperative work-up of patients with neuromuscular scoliosis going for surgery

The following papers describe surgical techniques for pelvic fixation, which are required for management of spinal surgery in this patient population:

Allen BL, Ferguson RL ( 1984) The Galveston technique of pelvic fixation with L-rod instrumentation of the spine Spine 9(4):388–94

This article describes the classic sacral fixation technique in neuromuscular scoliosis

Bulman W, Dormans J, Ecker M, et al ( 1996) Posterior spinal fusion for scoliosis in patients with cerebral palsy: a comparison of Luque rod and unit rod instrumentation.

J Pediatr Orthop 16:314–323

In this study the results of 15 patients who underwent arthrodesis with dual Luque rod instrumentation are compared with the results of 15 patients in whom unit rod instru-mentation was used The unit rod instruinstru-mentation allowed a significantly greater correc-tion of both the major curve and pelvic obliquity

McCarthy RE, Bruffett WL, McCullough FL ( 1999) S rod fixation to the sacrum in patients with neuromuscular spinal deformities Clin Orthop Relat Res 364:26–31

This article describes a new form of pelvic fixation for use in patients with neuromuscular spi-nal deformities to overcome the problems imposed by the Galveston technique One end of

a Luque rod is prebent into an S-shaped configuration and placed over the sacral ala, supply-ing firm fixation across the lumbosacral junction without crosssupply-ing the sacroiliac joint It fixes firmly against the sacral ala by distracting against a hook or screw in the lumbar spine

Arlet V, Marchesi D, Papin P, Aebi M ( 1999) The ‘MW’ sacropelvic construct: an enhanced fixation of the lumbosacral junction in neuromuscular pelvic obliquity Eur Spine J 8(3):229–31

The authors introduce a new fixation system, in which iliosacral screws are combined with iliac screws This is made possible by using the AO Universal Spine System with side opening hooks above and below the iliosacral screws and iliac screws below it The whole sacropelvis is thus encompassed by a maximum width (MW) fixation, which gives an ’M’ appearance on the pelvic radiographs and a ‘W’ appearance in the axial plane

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