Spinal Disorders: Fundamentals of Diagnosis and Treatment Part 69 ppt

These patients tend not only to have severe deformities, but they also have associated pathologies that are directly or indirectly related to their spinal deformity that puts them at hig

Neurological Examination

Always check abdominal reflexes

The treating surgeon must complete a thorough physical examination not limited

to the musculoskeletal examination Literally, a head to toe examination is

required to search for NMD Missing abdominal reflexes can be a subtle sign of

neurogenic scoliosis Flaccid faces can be suggestive of subtle myopathies while

asymmetrical shoe size can be a subtle sign of syringomyelia Having the patient

walk and run while looking for gait pattern and upper extremity posturing can

elucidate a subtle spastic diplegia Lower extremity morphological asymmetry

such as a unilateral cavus must alert the surgeon that there may be underlying

spinal cord pathology warranting further investigation A detailed neurological

examination must be carried out to assess for both sensory and motor deficits

Testing reflexes and looking for long tract signs such as Babinski’s and Hoffman’s

signs, clonus, and spasticity are all part of a first visit examination of a newly

diagnosed scoliosis If weakness is present, differentiating proximal from distal

distribution may help in differentiating neuropathies from myopathies Looking

for proximal girdle strength should also be tested by asking the child to stand

unassisted from a sitting position If the child is unable to do so or uses their

hands to push themselves up by adapting a wide base gait and locks the knees in

extension with the hands and uses the hands to push themselves along on their

legs, then this is considered a positive Gower test Romberg’s test should also be

performed to test cerebellar function (testing balance with eyes closed, feet side

by side and arm forward flexed) Signs of calf hypotrophy are also documented as

a diagnosis of Charcot-Marie-Tooth disease can be made

Diagnostic Work-up

Medical Assessment

Pulmonary function less than 35 % of predicted

is associated with increased risk of ventilation

dependency

Confirming the diagnosis of neuromuscular scoliosis is best done in a

multidisci-plinary fashion by including the neurologist and geneticist To achieve a final

diagnosis, nerve and muscle biopsy may be warranted Managing spinopelvic

deformity in the neuromuscular patient remains a challenging task These

patients tend not only to have severe deformities, but they also have associated

pathologies that are directly or indirectly related to their spinal deformity that

puts them at higher risk of morbidity and mortality (Case Study 2) This

multi-disciplinary team should include a pulmonologist, a cardiologist, dieticians, a

physiotherapist, and an occupational therapist Particular attention must be paid

to pulmonary functions as many patients have severe restrictive pulmonary

dis-ease Pulmonary function of less than 35 % predicted is associated with a

pro-tracted postoperative course with an increased risk of ventilation dependency

Cardiac arrhythmias secondary to conduction abnormalities and even possible

ventricular hypokinesis can be seen in dystrophy patients, in particular those

with Duchenne muscular dystrophy A large proportion of patients with

neuro-muscular scoliosis have concomitant dietary problems leading to malnutrition

Check for the nutritional status

(low total protein and a low leukocyte count) As nutritional status [51] has a

direct impact on the risk of deep wound infections, perioperative nutritional

optimization in the form of continuous feeds via a nasogastric tube or total

par-enteral nutrition (intravenous caloric and protein supplements) during

hospital-ization is recommended

a b

c

d

e

f

Case Study 2

An 11-year-old girl with a mid-tho-racic functional myelomeningocele presented with progressive neuro-genic kyphosis (a,b) The patient had had a tracheotomy for central apnea since the age of 6 years Sitting and wheelchair adaptation had become progressively more difficult The tho-racolumbar kyphosis was compound-ing her already compromised respira-tory status due to loss of spinal height The pathophysiology of mye-lomeningocele kyphotic progressive

g h

Case Study 2 (Cont.)

deformities is secondary to the

fol-lowing “mechanical” considerations:

loss of posterior tension band,

erec-tor spinal musculature becoming a

“flexion” vector as it subluxes

ante-rior laterally, and anteante-rior column

deficiency A hyperextension X-ray

shows the kyphosis to have

cor-rected but only partially (c) Surgical

treatment included first stage

poste-rior spinal instrumentation and

cor-rection with a pedicle subtraction

osteotomy at L2 Distal fixation was

achieved by using a Donn McCarthy

presacral ala rod supplemented with

a far lateral pedicle screw preventing

distal fixation pull-out Proximal

ped-icle screws were used flanking the

osteotomy while proximally the

fusion and instrumentation was

extended to T2 to avoid junctional

kyphosis (d,e) The patient had 2nd

stage anterior interbody fusion

across the kyphotic segment as

pos-terior bone mass was inadequate for

solid fusion In the span of 5 months,

the patient developed severe

junc-tional kyphosis (f) with required

extension of the instrumentation to

the first lordotic cervical segment.

Junctional kyphosis was assessed

and noted to be relatively flexible on

extension film; thus no anterior

release was done prior to final

sur-gery (g, h) Inferior facettes were

resected, providing adequate

correc-tion and sagittal balance.

Imaging Studies

Plain Radiographs

Standard radiographs (standing or sitting) remain the imaging modality

of choice

Obtaining reliable spine X-rays is a challenge in this patient population as some

are unable to stand, to sit or even to lie still for the X-rays Taking this into

consid-eration, standard unassisted upright standing or sitting AP and lateral X-rays

have an added variability, thus making curve monitoring more difficult In some

cases supine X-rays are the only X-rays feasible As part of the preoperative

imag-ing, supine bending films and/or traction films should be obtained to guide

sur-gical planning The bending films and even the traction films will provide some

insight into the spinal muscular atrophy patient; however, in the spastic quad

lit-tle will be gained as the patient will not relax for the surgeon to see the residual

rigid deformity Obtaining an intraoperative X-ray with the patient under

gen-eral anesthesia can provide added information to decide whether the patient

needs an anterior release More important is an intraoperative physical

examina-tion to assess curve and pelvis flexibility An absolute Cobb measurement must

NMD curve typically presents with a long collapsing C-shaped curve

not be taken without clinical correlation

A long collapsing C-shaped curve pattern is the classic spinal deformity found

in the neuromuscular patient (Case Study 1) Granted that this is the classic curve

But NMD can present

with any other curve pattern

pattern, any curve pattern can be found Left-sided curves, particularly in males, have been associated with syringomyelia The absence of Dickson’s apical lordo-sis [9] on the lateral X-ray should raise the suspicion of neuromuscular scoliolordo-sis [39] Stagnara described that as the spine rotates 90° the lateral deviation (scolio-sis) of the spine is then oriented in the sagittal plan, resulting in apparent kypho-sis [46] (Fig 3 ) The other type of kyphotic deformity in neuromuscular scoliosis

is secondary to loss of the posterior tension band such as in myelomeningocele [20] (Case Study 2) or in myopathy scoliosis This kyphosis can result in signifi-cant loss of spinal height, resulting in internal organ crowding and skin break-down over the gibbus

a

b

Figure 3 Neurogenic kyphoscoliosis

The rotational deformity of scoliosis causes an apparent kyphosis.a,bThe clinical coronal deformity appears moderate However, due to the severe rotational deformity compounded by severe pelvic obliquity, the PA X-ray is actually more of

a lateral of the spine.c,dThe apparent severe sagittal kyphotic deformity is in fact the coronal scoliotic deformity This

is apparent as one notes the lumbar vertebrae are oriented in a PA orientation This case illustrates the true three-dimen-sional nature of spinal deformities.

Magnetic Resonance Imaging

Rule out intradural pathology by MRI

Any scoliotic patients with a hint of neurological signs or symptoms [8, 49] or

with neuroectodermal skin lesions must have MRI performed of the entire spine

(occiput to sacrum) to assess the presence of any intradural lesions:

syringomye-lia, tethered cord, and spinal tumor Malignant curve progression warrants MRI

as it may also be a sign of intradural pathology

Non-operative Treatment

When consulting patients for the type of treatment, a thorough knowledge of the

natural history is mandatory The natural history in neuromuscular scoliosis is

closely linked to the underlying disease

Natural History

The life expectancy of NMD patients is diminished

In general, patients with neuromuscular scoliosis have a diminished life

expec-tancy compared with the general population which is mainly secondary to their

underlying neuromuscular diagnosis Spinal deformity if severe can negatively

impact their life expectancy, particularly scoliotic deformities leading to

cardio-pulmonary compromise [18] (Table 1)

The natural history of neuromuscular spinal deformity is one of curve

pro-gression irrespective of etiology Granted that there are many different factors

influencing curve progression, there are some neuromuscular curves which do

not progress; however, the majority will

Factors influencing curve progression are as follows:

) age of onset of NMD

) severity and rapidity of weakness

) evolving or static neuromuscular disease

) skeletal maturity

) ambulation status

) severity of curves

Few papers have specifically looked at the natural history and curve progression

of patients with neuromuscular scoliosis [15, 20, 25] Their curve progression has

Severe curve progression occurs mainly during peak growth

been reported to be from 7° to 40° per year The severe progression occurs mainly

during patients’ peak growth compounded with loss of an autoregulatory spinal

alignment process which their underlying neuromuscular condition impedes

For example, in Duchenne muscular dystrophy, the rate of curve progression

in untreated boys overall averages 7° per year Oda et al [36], after reviewing the

natural history of scoliosis in DMD, found that there were three courses of curve

progression:

) Type I curves comprise progressive collapsing kyphoscoliosis with

signifi-cant rotatory deformity extending into the pelvis which always reach 30°

before the age of 15 years, with a rapid progression of 15°–20° per year

thereafter

) Type II curves are characterized by hyperlordosis with a progressive

scoli-otic deformity The patients with double major curves tend not to have

pel-vic obliquity and have stable curves, while patients with lumbar or

thoraco-lumbar curves tend to have pelvic obliquity and progress as type I curves

) Type III curves have straight sagittal spines and have non-progressive

scoli-otic curves that never reach 30°

Patients with cerebral palsy

have a highly variable

onset of puberty

In Becker’s muscular dystrophy, curves tend not to be severe and non-progres-sive [29], as the patients tend to be older In contrast, 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

Scoliosis in cerebral palsy

can progress into adulthood

It has also been shown that scoliosis in patients with cerebral palsy continues

to progress even into adulthood [16, 25]

Non-operative Treatment Options

Non-operative treatment

must be individualized

The non-operative management of neuromuscular spinal deformities must be adapted to each patient’s specific requirements When patients are still able to be upright, then initial treatment consists of encouraging prolongation of an upright position while maintaining standing/ambulation status

Once a patient is wheelchair dependent, then seating modifications are

war-ranted to provide lateral trunk support, as well as accommodation of sagittal

deformities such as hyperlordosis or kyphosis The seating surface must also be

carefully chosen to minimize skin breakdown while providing enough support to minimize pelvic obliquity Controlling and compensating hip contractures must also be taken into consideration to favorably influence the pelvis to minimize an oblique take-off of the spine

Bracing is usually not

helpful in neuromuscular

scoliosis

Bracing in neuromuscular scoliosis should not be seen in the same light as

bracing for idiopathic scoliosis Bracing has not been shown to prevent curve progression in neuromuscular scoliosis [37]; thus its usage is not oriented towards the treatment of these curves [6, 32]

The bracing used for neuromuscular scoliosis is functional bracing It

pro-vides external support to the spine, allowing some patients to be more func-tional Its goal is to maximize functional positioning by controlling some of the spinal collapse, improving posture, and facilitating seating in some cases One must realize that in some patients with neuromuscular scoliosis bracing is con-traindicated since it may result in compromising what is left of their respiratory reserve Bracing can seriously limit gastric motility, worsening the nutritional status of these patients Some will simply not tolerate the braces, with uncontrol-lable behavioral problems Obviously in any of these situations, bracing should

be discontinued, since it is counterproductive to a functional bracing Early rec-ognition of neuromuscular spinal deformity is important, since treatment plans must be instituted as soon as possible

Operative Treatment Surgical Indications

The decision to proceed with major spine surgery for neuromuscular scoliosis remains somewhat controversial, particularly when looking at the elevated mor-bidity and mortality of this type of surgery Yet a consensus is emerging that with adequate pre- and perioperative multidisciplinary management and with a suc-cessful outcome, most patients and caregivers feel the surgery is beneficial to their overall well-being [3]

The indication for scoliosis

correction in NMD patients

remains controversial

Absolute surgical indications remain controversial [22] for globally disabled children The classic surgical indications of idiopathic scoliosis, i.e., curves > 50°

or curve progression in the immature patient, also apply to the management of

neurogenic scoliosis However, these tend not to be the main factors influencing

the decision to operate Loss of function is the more common indication to

pro-ceed with surgical management of neurogenic scoliosis As their spinal deformity

progresses, the ensuing spinal deformity and trunk shifts result in decreased

pul-monary function and increased respiratory disease, deterioration of comfort

and loss of the activities of daily living, inability to walk or sit independently, as

well as a decrease in quality of life Sitting patients end up supporting themselves

with one of their hands, resulting in a functional triplegia Such functional losses

are surgical indications The development of pressure sores and the inability to

use further adapted wheelchairs to compensate for their spinal deformity are also

surgical indications since the spinal deformity has a real impact on the activities

of daily living In contrast to idiopathic scoliosis, where it is rare that the

defor-mity negatively impacts on the child’s well-being, neurogenic scoliosis

com-pounds an already fragile individual (Table 5):

Table 5 Indications for surgery

) severe (> 50 degrees) progressive curves

) curve progression in Duchenne muscle dystrophy

) loss of sitting balance

) cardiopulmonary compromise

) deteriorating general well-being

One must not forget that indications will vary depending on the underlying

etiol-ogy of the scoliosis For example, in Duchenne muscular dystrophy, knowing that

90 % of patients with DMD will have a progressive spinal deformity as well as a

In Duchenne patients surgery is indicated early

declining pulmonary function [33], one tends to intervene at a lower Cobb angle

and/or when the curve is progressive In fact a loss of pulmonary function is

more influential than a rise in Cobb angle As patients get older, their curves

increase while their pulmonary functions decrease Due to this reverse

relation-ship there is a window in which surgery is recommended, and if it is missed

mor-bidity rises to unacceptable levels When treating patients with cerebral palsy

who are skeletally immature with a progressive curve between 40° and 50°, or

skeletally mature cerebral palsy patients with curves greater than 50°, it is

recom-mended to proceed with a spinal arthrodesis [48]

General Principles

Do not blindly apply the classic principles

of idiopathic scoliosis management

The first principle, and probably the only steadfast rule when managing

neuro-muscular deformities, is not to blindly apply the classic principles of surgical

management of idiopathic scoliosis The second principle in managing

neuro-muscular scoliosis, which is the cornerstone of all surgical management of any

spinal deformity, is to achieve perfect spinal balance in both the coronal and

sag-Aim for coronal and sagittal balance

ittal planes [42] Classically these patients do not have compensatory

mecha-nisms (muscle tone, intact proprioception) to rebalance themselves

Patients’ curves tend to be long and they often have associated pelvic

obliq-uity, necessitating long fusions to the pelvis Therefore, the coronal and sagittal

balance must be perfect when performing spinal fusions for neuromuscular

sco-liosis Thirdly, a word of caution: a thorough preoperative and perioperative

medical management is mandatory in managing patients with neuromuscular

scoliosis These patients tend to have cardiac pathology, severe pulmonary

dis-Consider the comorbidities

ease, and malnutrition [51] to name a few associated conditions If these medical

problems are left unattended or are ignored, they will lead to catastrophic

com-plications

Surgical Techniques

Levels of Fusion

The Harrington principle, fuse the Cobb angle, also holds true for neuromuscu-lar scoliosis However, in contrast to idiopathic scoliosis, it is usual to actually span beyond the Cobb for two reasons:

) associated kyphosis ) associated pelvic obliquity Selective fusion should

not be done for NMS

In contrast to idiopathic scoliosis, selective spinal fusion should not be done since the underlying neuromuscular condition will continue to exert its force on the non-fused segment and new deformities will present themselves The fusion

is often extended proximally to address the sagittal kyphotic deformity

d

Case Study 3

A 14-year-old boy with cerebral palsy was referred for a severe and

particu-larly rigid spinal deformity with a rigid pelvic obliquity (a,b) His wheelchair

could no longer be adapted to provide comfortable positioning The

patient had developed a pressure sore on his left ischium Preoperative

X-ray confirmed both sagittal and coronal imbalance with little correction on

supine bending (c,d).

e f

Case Study 3 (Cont.)

Furthermore even under GA with manual traction it was not possible to level the patient’s pelvis (e) Hence an anterior

release was performed as well as an apical corpectomy (f) Subsequently the patient was placed in gravity halo traction

(g) One week later the patient had completion of apical vertobrectomy and posterior instrumentation and fusion with

restoration of sagittal and coronal correction (h,i).

Sagittal kyphotic deformities must be addressed and fused

Therefore, it is critical not only to choose your fusion levels with coronal and

bending films but to closely scrutinize the lateral X-ray to avoid stopping the

fusion at the apex of the kyphotic deformity (Case Study 3) The fusion must

extend out of the kyphosis to the first lordotic segment; this holds true both

prox-imally and distally [19] Fusing long will avoid problematic revision surgery for junctional kyphosis

Selective spinal fusion

must be avoided

In general, T2 is the proximal fusion level for neuromuscular scoliosis Fusing too short or excessive kyphotic correction leads to junctional kyphosis as patients with neuromuscular kyphoscoliosis want to drift back to their initial sagittal alignment, placing tremendous forces at the distal end of fixation Fixation to the sacrum

is a major challenge

More often than not, if the distal level of the fusion exceeds the Cobb angle, it

is to address the associated pelvic obliquity In general, L5 or the sacrum is the

distal fusion level for neuromuscular spinal deformities There remains some debate as to whether the pelvis should be included or not in the fusion Patients with pelvis obliquity of less than 10° can have their fusion down to L5 to avoid the complications associated with fixation to the pelvis Trying to fuse across the lumbosacral junction is associated with a high rate of non-union Secondly, as there is one level left of mobility, overall spinal alignment can be forgiving, and spinal balance may be achieved by patient volition The downside of stopping the fusion short of the pelvis is that there is a possibility that the patient decompen-sates out of balance as the pelvis tilts, thus leading to further spine surgery in already frail patients

Spinal Fixation

Sublaminar wires have been

the gold standard treatment

The classic spinal implant for neuromuscular curves comprises sublaminar wires with Luque rods [24] The advantages of this classic segmental spinal fixation are that one achieves a gradual reduction of each segment (mainly by spinal transla-tion), thus minimizing the risk of fracturing the spinal anchorage points Poor bone quality

challenges the instrumentation

This is of particular concern when treating non-ambulatory patients with an osteoporotic spine either from disuse and/or induced by long-term antiepileptic medication The disadvantages of wires are the potential risk of injuring the spi-nal cord during insertion and the risk of considerable epidural bleeding Consider the risk of spinal

anchorage point fracture

and pull out

The alternative construct is a combination of multiple sublaminar hooks, ped-icle hooks and/or pedped-icle screws at each level, distributing the forces across the entire spine The use of multiple pedicle screws can provide enough corrective forces for the anterior release to be avoided, and to allow for single stage poste-rior spinal fusion and instrumentation [30] The liberal use of pedicle screws (lumbar and thoracic) rather than sublaminar wires serves two purposes Firstly, they allow for a much more thorough decortication, which obviously helps to achieve a better fusion Secondly, pedicle screws allow for much more radical bilateral facetectomies, which facilitates greater correction Both of these can be done without fear of weakening the spinal fixation points

Sacral and Pelvic Fixation

The classic spinal implant for the management of pelvic obliquity associated with

neuromuscular scoliosis is the Luque-Galveston construct [11] This fixation

from T2 to pelvis spans the lumbosacral junction by inserting the distal rods into Sacral and pelvic fixation

remain a major challenge

in NMD

the posterior superior iliac spine (PSIS) between the inner and outer tables just

above the sciatic notch (Fig 4) Adding an S1 pedicle screw to the base of the con-struct and a cross-link proximally adds significant stability to the concon-struct [26] The unit rod [35] has been shown to be a more effective means of addressing the pelvic obliquity and the spinal deformity [7] The reduction maneuver for

cor-recting pelvic obliquity consists of a cantilever maneuver This entails fixing the

rods distally to the pelvis at a 90-degree orientation to the ischial tuberosities Then the rods are levered across and attached to the proximal spine, thus leveling the pelvis perpendicular to the balance of the spine The entry points in the PSIS