Article - Spinal Deformity and Ehlers-Danlos Syndrome

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Spinal Deformity and Ehlers-Danlos Syndrome

By Mr. P.J. Webb FRCS, Consultant Orthopaedic Surgeon

The Royal National Orthopaedic Hospital, Stanmore

Control of Spinal Shape

Spinal shape is maintained in the normal person by the shape of the spinal

joints, strength of ligaments, and action of the muscles under control of

the central nervous system.

There is thus a complex of control mechanisms, abnormality in any of which

may result in an abnormality of spinal shape.

Spinal Deformity

'Scoliosis' is not a diagnosis in itself, but a description of the spinal

shape and implies a lateral curvature, usually with rotation, which may

arise from any of a large number of causes.

Scoliosis, it should be noted, is never part of the normal spinal shape

pattern, which contrasts of course with kyphosis and lordosis, both of which

are angulations in the frontal plane and may be part of the normal shape.

They are only considered abnormal if they are increased in size or

stiffness.

Development of the Spinal Shape

Spinal shape changes with age. The maximum occurring within the first 12

months. A child in utero is born with a spinal shape which is virtually 'C'

shaped. At six weeks, control occurs in the neck muscles, which results in

the foetal kyphos being changed to include a lordosis in the cervical

segment.

As the child begins to sit up, lordosis is also encouraged to occur in the

lumbar region. Thus adult shape develops with kyphosis in the dorsal region

balanced by a lordosis above and below.

Function of the Spine

The shape of the spine is important for the safe passage of the contents of

the spinal canal, attachment of muscles to support the limbs, preservation

of function of the spinal cord and an ability to defend itself against

increasing load. Deflection from the normal range results in a loading of

the spine which occurs in the direction of the pre-existing curves which,

because they are pre-determined by the shape of the joints and ligaments

under the control of muscles and are able to resist the increasing loads

placed upon the spine by allowing deformation in a controlled manner, which

of course contrasts with the buckling which may or may not take place if the

spinal column was merely straight.

Types of Spinal Deformity

Spinal deformity exists in the general population in about 5%. Some authors

have reported a very much higher level

Idiopathic Scoliosis

Of the overall group with spinal deformity 80% have scoliosis without an

identifiable cause, known as idiopathic. This is likely to occur either in

the earlier age group between 0-3 years of age, or at the adolescent growth

spurt. The pattern of abnormality is quite typical and although the

diagnosis of idiopathic implies 'no known cause' the particular clinical

pattern is easy to identify. There are no other abnormalities associated

with this sort of scoliosis.

The majority of the earlier group will spontaneously resolve, whereas the

majority of the older group get worse, until the end of the growth spurt,

and only those with a curve over a certain degree have problems later on in

life. These problems are related to pain arising within the joints and on

occasion, difficulty breathing because of the deformation of the shape of

the spine supporting the chest with the associated abnormality of rib shape.

It is not true to say that all curves will stop progressing when growth

stops. It is unfortunately only true that smaller curves behave in this

way.

Neuromuscular Scoliosis

Approximately 12% of the group with spinal deformity may coexist in

association with neuromuscular problems such as muscular dystrophy. The

natural history of spinal deformity in this group will depend upon the

prognosis of the condition and the progression of the condition with which

the deformity itself associated.

Osteogenic Scoliosis

A smaller group of spinal shape abnormalities exist because the spine has

developed abnormally. This group is difficult to assess because the

deformity, which exists, depends upon the growth potential of the spine

itself, which is difficult to assess. Ideally the rate of progression of

the curve needs to be assessed early in the growth period, certainly during

the first 2-3 years, in order that a logical treatment can be planned.

Syndrome Scoliosis

A very small group of spinal shape abnormalities develop in association with

named syndromes, that is, a collection of commonly related abnormalities.

The Ehlers-Danlos Syndrome is a member of this group which is thus not

particularly common in the general population.

Ehlers-Danlos Syndrome

As has been implied above, the reason for the shape of the abnormality in

Ehlers-Danlos Syndrome almost certainly relates to the lack of support which

the soft tissues provide, that is, the fragility of the collagen which is a

part of the Ehlers-Danlos Syndrome.

Modern biochemical analysis of the collagen defects have been defined the

molecular basis and although it is clear tat spinal deformity may exist in

the group of patients with Ehlers-Danlos Syndrome, it is not clear which

particular defects carries the greatest risk.

Pattern of Development in Ehlers-Danlos Syndrome

Review of Ehlers-Danlos patients with spinal deformity nevertheless

demonstrates a similar pattern of spinal shape in all of them, that is,

short multiple curves which exist in comparison with the adolescent

idiopathic curve which is usually a longer curve. Furthermore, the rate of

progression of the curve is faster than the adolescent idiopathic.

Treatment: Conservative methods of treatment, that is,

exercises and bracing, are likely to effect the smaller curves only. It is

to be noted that with the skin problems which exist in Ehlers-Danlos

Syndrome, bracing may be difficult to maintain because the skin is not tough

enough to withstand the continual stress placed upon it by brace wearing.

Brace effectiveness is also reduced by the shape of the spinal deformities,

it being very difficult to brace very short, very sharp curves. Multiple

curves may make it difficult to apply adequate pressures of correction

within the brace.

It is the experience of the author of this article that Ehlers-Danlos

Syndrome patients are unlikely to be successful brace wearers in the long

term. Surgical stabilization is thus likely to be offered if the spinal

shape is not controlled by conservative methods. If it is clear during the

course of treatment that the deformity is likely to be greater than a

certain degree by the time growth has stopped, then surgical treatment is

likely required.

Surgical Treatment Spinal fusion's are undertaken to increase the intrinsic

strength of the spine by joining together the spinal vertebrae involved in

the deformity, by excision of the joints and addition of bone to the joint

spaces as well as additional bone on the surface of the vertebrae. This may

be undertaken either in front (anteriorly) or behind (posteriorly).

Internal fixation devices such as Harrington Rods or similar devices serve

to provide some control and to maintain the spine in the corrected position

with as little movement as possible until the fusion has taken place. This

process, which is similar to the repair of a fracture, takes approximately 6

months, or longer, during which time the patient needs to wear some form of

brace support in the usual case, not so much as a corrective force but

merely as a protection against too much movement.

The Ehlers-Danlos Syndrome results in softer bones as well as more fragile

soft tissues and it is thus advisable to consider a spinal fusion earlier so

that the surgical problems are reduced and there is a lesser requirement for

firm corrective forces to be applied.

Techniques of spinal fusion vary from patient to patient but, in general,

the younger patients, or those with profound curves, are best stabilized

from both the front and the back of the spine.

Although a large segment of the spine may need to be treated this way, the

loss of function from this is not profound, but nevertheless needs to be

weighted against a tendency for progression of the curve. Although surgical

techniques have improved considerably in the last 10 years, nevertheless,

Ehlers-Danlos Syndrome remains a special problem as a result of the collagen

fragility, which needs to be carefully evaluated before surgery can be

safely considered.

Summary

Ehlers-Danlos Syndrome patients have an increased risk of spinal deformity

compared with the general population, which results in a typical multiple

curved pattern which should be treated early rather than late and may

require surgical intervention more commonly than any other types of spinal

deformity.

Screening

It is important therefore to look for spinal deformity, for example by

forward bending positions. If there is a asymmetry between the two sides of

the spine when viewed from behind, in either the upright or forward bending

position, then an explanation should be sought as early as possible. It is

all too easy for significant deformity to be missed, particularly since

these curves are rather smaller than the usual and can be hidden by

corrective or compensatory curves existing above or below.