Spinal orthoses

2. Spinal Orthoses

G. Morrish,

M. W. Whittle

Collars

Introduction A spinal following

orthosis can perform functions :

one or more

These include :

of the

(a) Soft collars (foam). (b) Hard collars. (c) Flexible plastazote collars, which are heated in an oven at 140°C and moulded directly to the patient. (d) Doll’s collars, made of thermoplastic heated to 180°C and mounted on to a plaster positive, taken from a plaster cast of the patient.

(a) Rest a joint or a fracture in a chosen position. (b) Totally or partially relieve stress from a joint or bone. (c) Transmit forces. (d) Stabilise a joint or joints in a chosen position. (e) Correct, prevent or support a fixed or only partially correctable deformity. (f) Control joint range of motion during activity. (g) Reduce heat loss. (h) Act as a placebo. (from a functional biomechanical classification of orthoses made by G. K. Rose in 1980). l

Braces

(4

Four poster brace, with padded mandibular supports fixed to anterior and posterior thoracic plates by metal uprights (Fig. 1). brace which extends further (b) Cervico-thoracic down the trunk. (cl The Somi brace, which is prefabricated, with one metal strut from the chin piece to the front of the plastic chest piece. Metal strips pass from the

It is essential to choose an orthosis which is suitable for its purpose, and there have been many studies on the mechanical effects of different orthoses, such as the degree of immobilisation achieved. However, if an orthosis is not accepted by the patient it will not be worn, no matter how well it works. Therefore, a spinal orthosis should be as comfortable as possible, both in sitting and standing, with smooth edges, so that it does not dig into the patient, and it should have no sharp accessories to snag or tear clothing. Where possible, fastenings should be chosen so that the orthosis is within the patient’s capacity to doff and don with ease.

Cervical Spine Cervical spine orthoses restrict the motion of the cervical spine and help support the head. They can be split into 2 groups; collars and braces. G. Morrish BSc, MCSP, M. W. Whittle MB, BS, PhD, Oxford Orthopaedic Engineering Centre, University of Oxford, Nuffield Orthopaedic Centre, UK.

Fig. I-A

UK Ltd

brace. 0268&0890/89/00034122/$10.00

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four poster

122

CURRENT

did not have very immobility obtained flexion and extension

Fig. 2--P, Somi brace

occipital

pad to attachments

on the shoulders

(Fig.

2). (d) Halo with plastic body vest. The halo is attached to the skull by four pins. It offers the surgeon the abihty to fix the position of the head.

Various studies have been undertaken to compare the effectiveness of different collars and braces in controlling the motion of the cervical spine, to enable the surgeon to prescribe the most effective device for a particular condition. Orthoses are used for rest and support in cervical spondylosis, rheumatoid arthritis, trauma, infection. neoplasm, osteoporosis, neurological conditions which cause muscle weakness, and ‘drop attacks’ caused by compression of the vertebral arteries.’ They ‘ire also used after the release of the sternomastoid muscle in torticollis. The degree of immobility obtained is an important consideration governing the choice. Flexion and extension at each cervical intervertebral joint and combined cervical motion for rotation and lateral bending, were measured in 5 normal subjects wearing various collars and braces.? A group of 7 patients with cervical fractures or local fusions were also tested wearing a halo with body vest. None of the conventional braces or collars were good at limiting flexion and extension at the atlanto-occipital joint. The soft collar allowed 80”; of extension and 7696 of flexion between Cl C7; the Somi 589,; and 74,; the four poster brace 18Y0 and 10’;; and the cervicothoracic brace IO”; and 89,. The halo, however, only allowed 3”, of flexion and extension at the atlantoaxial joint and 1”, at C2PZ3. Lateral bending and rotation were not well controlled by any of the devices except the halo, which only allowed 19, of rotation and 4”; of lateral bending. From this, the authors of the study concluded that skeletal fixation is necessary to control very unstable lesions in the cervical spine. A recent study found that the length of the halo vest

ORTHOPAEDICS

much effect on the degree except for a slight decrease below C5 in a longer brace.3

123 of in

Hard and soft collars are very commonly used in cervical spondylosis to rest the joints of the cervical spine and to relieve muscle spasm. They are probably more effective in the acute phase when the apophyseal joints are most irritable.’ Many patients find great relief by using a hard collar by day and a soft collar by night. Orthoses are also frequently used in rheumatoid arthritis affecting the cervical spine, to limit pain and to support the neck. However, the therapeutic value of collars is doubtful, since in one study of 106 patients, those who progressed to severe neurological problems, did so while wearing a firm collar. The collar probably serves to limit sudden flexion, which might result in neurological damage and even death, where there has been erosion of the odontoid peg and ligamentous destruction, which could lead to anterior subluxation.s The wearing of a cervical collar is unacceptable to many rheumatoid patients, some of whom are more comfortable in a brace with an occipital pad and chin support. Where a cervical orthosis is being used in conditions causing muscle weakness. the incorporation of a forehead band is useful to help support the head

Bracing of the Trunk Examples

of trunk orthoses

(a) Orthoplast

are :

jacket which is immersed in boiling water, then shaped to the patient. (b) Moulded leather jacket for long term use. (c) Jones brace, which has two posterior vertical bars, joined at the top by a metal hoop and at the bottom by a wider horizontal sacral piece. The metal is covered by leather or vinyl. (d) The Taylor brace, which is very simtlar except that the top is open and ends in shoulder straps, and is now frequently made of fabric. (e) Goldthwait brace, which is very little used now, although occasionally the brace superstructure is superimposed onto a fabric corset. brace. which is used (f) The Jewett hyperextension as a stabiliser. (Is) C’orsets and belts; these may be long or short or constructed especially for the lumbo-sacral area. They are sometimes elastic. They are usually ready made unless there are special fitting difficulties. and Cotrel braces for the (h) Boston, Milwaukee. correction of scoliosis or kyphosis. The Boston (TLSO) is a prefabricated plastic jacket with inner pads. The Milwaukee (CTLSO) is a custom made orthosis with a head support unit. It used to be made with a chin piece. but due to dentition

124

SPINAL

ORTHOSES

problems it is now usually made with a throat piece.5 The Cotrel (CTLSO) is also individually made, and is particularly useful for higher curves. The main biomechanical functions of trunk orthoses are : (a) Immobilisation. (b) Correction of deformity. (c) Support for trunk muscular

weakness.

Immobilisation Orthoplast jackets are frequently used after a period of immobilisation in a plaster of Paris jacket, either put on for various activities or worn all the time. They can also be used for young patients with spondylolysis or spondylolisthesis. In general, plaster of Paris jackets are worn where a greater degree of immobility or compliance is desirable. In a study comparing the plaster of Paris jacket with different types of braces and a corset, it was found that they all controlled forward flexion fairly efficiently at L3-4, but they all had poor control of forward flexion at the L4-5 and L5-Sl interfaces.‘j The Taylor brace and modifications of it were among the most efficient at the lower levels.

Spinal orthoses for disc related problems The use of orthotic devices for disc problems has its advocates and opponents. The rationale for their use is based on immobilisation and abdominal support.’ Their mechanical effectiveness might result from the restriction of either intersegmental motion or gross motion. The latter is probably of greater importance in low back pain, because the higher segments need to be supported.s The loading is increased on flexion, extension, and lateral flexion. Although the spine can be regarded as an elastic rod, load is also taken by ligaments and other soft tissue structures, and by the facet joints.’ Loading of the spine is thus complex, with tensional, compressive, torsional and shear forces, the load being taken by different structures in different positions. The effects of a long fabric support, a short fabric support, an elasticated support, a plastic jacket and a leather covered steel brace have been compared; * the use of any of these increased the intra-abdominal pressure. In another study, however, it was found that the effect was variable.9 In two subjects wearing a Camp corset, the pressure was raised in one, and lowered in the other. It has been shown that there is an increase in intraabdominal pressure (IAP) on lifting, both when wearing an inflatable corset and without it;‘O this is due to what is probably a conditioned reflex. Not everybody agrees that the compressive load on the spine is necessarily lowered by a rise in 1AP.l’. I2 The picture is confused because most of the studies on the effect of IAP on spinal loading have been made with active contraction of the abdominal muscles. This is

not the same as raising the IAP by means of an orthosis in relaxed standing. Active contraction of the abdominal muscles will result in an increased flexion moment, which may be less than the extension moment due to the rise in IAP, and will also require an increased extension moment by contraction of the paraspinal muscles. There may therefore be an increase in spinal loading when abdominal muscles are contracted.’ ? Intradiscal pressures, which are an indication of compressive loading in the spine, have been measured by a subminiature pressure transducer built into the tip of a needle.9 Differences were seen as a result of wearing orthoses. for a variety of tasks. With a subject wearing a Camp corset, there was a lowering of pressure when supporting a weight and in resisted extension, but increased pressure in resisted flexion. Orthoses lower the activity of the abdominal muscles, but do not seem to have much effect on the long back muscles. ’ 3* l4 On the cessation of orthosis wearing there is probably a lowering of abdominal muscle activity due to disuse, which might decrease their protective function. Orthoses for low back pain also have a strong placebo effect, which might be advantageous initially, but not with prolonged use, if the patient becomes dependent on the device. If the patient is in much pain, the firm pressure of a lumbar pad often gives relief. Orthoses have heat retention properties which can also be helpful, especially in the elderly.

Treatment of a dej&mitJ Spinal deformity

can be of two kinds :

(a) Lateral and rotational deformity, associated with scoliosis. (b) Flexion deformity, which may be the adolescent kyphotic deformity associated with Scheuermann’s disease, the progressive flexion of the spine in ankylosing spondylitis, or the kyphosis caused by collapse of the osteoporotic spine.

Lateral and rotational deformity Patients with severe scoliosis tend to be treated operatively, but the less severe are often treated by a combination of bracing and exercise. Spinal shape can only be influenced where adequate growth potential exists; therefore the forces need only be great enough to influence the biological situation.‘.i5 The forces which are applied are mainly transverse and derotational, but small axial forces are also generated (Fig. 3). If the Milwaukee brace is being worn there is also an attempt to employ distraction, but these axial forces are of less importance in milder curves. In Oxford, curves whose apex is lower than T667 are usually treated by the Boston brace, and higher thoracic curves by the Cotrel brace. The location of the structural curve may be lumbar.

-. __

tFA \

a

Fig. 3- ~Tie generatlon

FAZAxial

Force

FT=Transverse Force N.P.,Null Point

of axial forces

from a transverse

force.

thoraco-lumbar or thoracic and is frequently accompanied by a functional curve which is compensatory in nature and less rigid. There may however be a double structural curve. In a structural curve there is deformation of the vertebrae and tight ligamentous structures, and it cannot be corrected by muscular forces alone. The location of the apex of the curve determines the positioning of the applied forces.

The Boston hracr (Fig. 4) This is a prefabricated polypropylene shell with a soft foam polyethylene plastic lining. It is made in 24 sizes. The braces are built with 15” of lumbar flexion, and put on the patient. whose knees are slightly flexed,

CURRENT

-__

0RTHOPAFL)ICS

~____

125

from behind. The flexion of the lumbar spine is probably important to bring the transverse processes of the curved lumbar vertebrae to a position where they can be reached by the correctional pads.ih The brace modules are symmetrical, which itself gives partial correction, and it is important that the brace is long enough above and below the iliac rolls, which should rest just posterior to the iliac crests. It should be fitted over a seamless vest. Before the brace is fitted, radiographs are taken and the null point, which is the point at which the curve changes direction, is located (Fig. 3). The centre line is taken with a plumb bob. If the spine is in balance the plumb bob should line up between the spinous process of C7 and the mid-line of the sacrum. If the spine is not in balance, a trochanter pad may be necessary. The pads provide force couples, and there must be relief areas to allow for corrective deformation of the structures (Fig. 5). Posture correction within the brace is taught, and a scheme of accompanying stretching and mobilising exercises. A follow-up is necessary after 2 weeks, when the posterior opening and front apron are reinforced, the straps can also be marked to ensure that they are always tight enough. If the brace is to do its work it must exert pressure. Evidence of this pressure should be seen on the skin, which, however, should be in a good condition. It should not be possible to pull the vest i)ver the pressure areas. Advantages of the Boston brace are good cosmesis, and an extensive range of sporting activities (including swimming) which can be performed in the brace.

This is, like the Boston, a posterior opening It has four basic elements (Fig. 6) :

orthosis.

(a) Pelvic girdle. (b) Head support unit. (c) One anterior and two posterior uprights extending from the pelvic girdle to the head support. (d) Various corrective pads and accessories. A cast is made for the pelvic girdle, again with the knees flexed to gain a flattening of the lumbar lordosis. A.

Ant. rotation

Post. rotation From ‘The Boston

Fig. &Boston

brace

Fig.

5--Derotatlon

pad

pad

Brace System’

of the lumbar

manual

spine by the Boston

brace

126

SPINAL

ORTHOSES

The Cotrel brace

This is built from a plaster cast which is applied in traction and pelvic flexion, from which a positive is made. Plastic is heated to 180” in an oven and then moulded over the positive. There is a posterior metal spine with hinges to which are attached metal strips, covered in leather, which form attachments. The advantage of a Cotrel brace is that adjustments to the metal fastenings can be made to accommodate growth. The biomechanics of the inner correctional pads are exactly as in the Boston brace and can be adapted for the individual curve (Fig. 7). Although bracing for scoliosis is a popular treatment method, patient compliance is poor and the effect of treatment on natural history is still unclear. Flexion deformity

Fig. B-Milwaukee

brace.

From the cast, a positive is made and felt relief pads are nailed into position. Round this, a moulded leather or plastic girdle is placed and uprights attached. It is important that the pelvic girdle fits well, to provide reaction points for distraction forces and the corrective pads. It must also be low enough at the back to control lumbar lordosis and exert an intra-abdominal pressure.5 The neck support consists of a ring chin plate or throat mould, and an occipital plate. The throat mould is just above the level of the upper margin of the hyoid cartilage. The occipital plate should be high enough so that upper cervical extension will press the skull on to the occipital plate and produce distraction.’ The anterior superior border follows the line of the ribs but is flared outwards laterally so that it does not impinge on the lower ribs. The anterior superior iliac spines should be in their channels and free from any pressure. The uprights are bent to follow the contours of the body. The pad with the best mechanical advantage is the L-shaped thoracic pad which is at the level and below the apex of the curve (as in the Boston brace) unless there is a double structural curve, in which it will be shifted one segment up to avoid making the lumbar curve worse.s There is also a shoulder ring which is on the side of the high shoulder. According to its point of attachment it can retract, protract, or depress the high shoulder. The lumbar pad is attached to a strap and is placed just below the convex side of the lumbar curve.

If a flexion deformity occurs in the spine due to a reduction in the height of the vertebral bodies or discs, additional demands will be placed on the extensor muscles, which will eventually not respond adequately. Such a situation occurs in ankylosing spondylitis and osteoporosis. Gradual reduction of the flexion deformity can be obtained in ankylosing spondylitis with a Jewett brace in what appears to be a rigid spine. This may require careful positioning of the orthosis, based on Dempster’s calculation of the centre of mass (1961). The Jewett functions as a stabiliser, using 3 point fixation.] It is not a support (Fig. 8). The Jewett is sometimes used for poor posture in adolescents as a reminder and stabiliser, but not in

Fig. 7-Cotrel

brace.

After

0

B

’

A

Unsatisfactory as a support

Satisfactory as a stabiliser Fig.

8--Three

point

fixation

t ffi!

G. K. Rose

in a Jewett

brace.

active correction of deformity as in Scheuermann’s disease. Jones and Taylor orthoses, which are commonly used on osteoporotic spines, also serve as reminders by creating pressure on the axillary straps.’ The Jones brace has a high degree of patient acceptability (Fig. 9). Scheuermann’s kyphosis is frequently treated by bracing and exercises. In the younger patient a modification of the Boston brace may suffice, but some orthopaedic surgeons prefer a Milwaukee brace with a posterior kyphus pad. There must be at least 1 year of bone growth left for successful bracing, and there is no need to continue until skeletal maturity if correction is obtained. ’ The control of lumbar lordosis is very important both by bracing and exercise. The exercises aim to encourage thoracic extension without lumbar extension. Unlike the situation with scoliosis, bracing for Scheuermann’s disease is unquestionably successful. Spinul support.s,for trunk muscular ti>eakness Trunk

Fig.

muscular

9-~ A Jones

weakness

brace

can

be thought

of as a

CURRENT

ORTHOPAEDICS

127

mobile deformity, and braced in the same way. Examples are in progressive diseases such as Duchenne muscular dystrophy or spinal muscular atrophy. The trunk may also be braced in cerebral palsy where the trunk is affected, and in high paraplegias in children. Spinal bracing is frequently necessary in the non-ambulant patient to prevent severe scoliosis and the resultant drop in pulmonary function. A lumbar lordosis is promoted by bracing. This tends to lock the facet joints and to allow soft tissue contracture in the extended position. The type of orthosis most commonly used is the moulded leather jacket, or more recently an adaptation of metal and polqthene. A moulded leather jacket is also used in later maintenance of an untreated adolescent scoliosis and to prevent further deformity.

References I. Rose G K 1986 Orthotics: Principles and practice. William Heinemann Medical Books, London 2. Johnson R M. Hart D L, Simmons E F. Ramshy G R, Southwick W 0 1977 Cervical orthoses: a study comparing their effectiveness in restricting cervical motion in normal subjects Journal of Bone and Joint Surgery S9A: 332-339 3. Wang G J. Moskal J T, Albert T, Pritts C, Schuch C M, Stamp W G 1988 The effect of halo vest length on stabihty of the cervical spine. A study in normal subjects. Journal of Bone and Joint Surgery 70A: 357-361 3. Moncur C. Williams C J 1988 Cervical spme management m patients with rheumatoid arthritis: a review of the literature. Physical Therapy 68: 509-514 > Blount W P. Bidwell T R 1975 Milwaukee brace prmciples and fabrication. In: American Academy oforthopaedic Surgeons Atlas oforthotics: Biomechanical Principles and Application. The CV Mosby Company, Saint Louis Norton P L, Brown T 1957 The immobilising efficiency of back braces. Journal of Bone and Joint Surgery 39A: 1 I l-140 White A A, Panjabi M M 1978 Clinical biomechanics of the spine. J B Lippincott Company. Philadelphia, Toronto Deane G, Grew N D 1978 Some physical effects of lumbar spinal support orthoses. In: Harris J D, Copeland K (Eds) Orthopaedic Engineering. The Biological Engineering Society. London, pp 39-46 9. Nachemson A. Schultz A, Andersson G 1983 Mechanical effectiveness of lumbar spine orthoses. Scandinavian Journal of Rehabilitation Medicine (Suppl) 9: 139-149 Morris J M, Lucas D B, Breslar B 1961 Role of the trunk in stability of the spine. Journal of Bone and Joint Surgery 43A : 3?7_~351 II Nachemson A. Andersson G B J, Schultz A B 1986 Valsava maneuver biomechanics: effects on lumbar trunk load of elevated intra-abdominal pressure. Spine I I : 476-479 12. McGill S M 1988 A model to estimate loads in lumbar tissues. Proceedings of Canadian Society for Biomechanics. Ottawa. August Ii. Waters B L. Morris J M 1970 The effect of spinal supports on the electrical activity of the muscles of the trunk. Journal of Bone and Joint Surgery 52A : 51-60 14 Lantz S A, Schutz A B 1986 Lumbar spine orthosis wearing II. Effect on trunk muslce myoelectric activity. Spine I I : 838-842 I’ Blount W P 1973 Principles of treatment of scoliosis and round h,lck with the Milwaukee Brace. Israel Journal of Medical Science 9 : 745-749 16 Manual for ‘The Boston Brace System’ Workshop (revised 1077). Children’s Hospital Medical Center. Boston, Mass 17 Young A, Johnson D, O’Gorman E, Macmillan T, Chase A P I984 A new spinal brace for use in Duchenne muscular dystrophy. Developmental Medicine and Child Neurology 26: X(18 Xl7