The early management of congenital dislocation of the hip

The Early Management of Congenital Dislocation of the Hip

M. F. Macnicol

Introduction The unstable hip at birth continues to evade detection, although determined efforts with screening can reduce the incidence of late presentation to a gratifyingly low level.‘.’ Failure to monitor abnormal or suspicious hips at the neonatal stage leads to disappointing results since acetabular and femoral head deformities progressively worsen. thus preventing a precise and durable reduction. The detection of the displaced or unstable hip at birth depends upon a thorough examination of the infant by an experienced examiner. If the assessment is hurried or the baby is squalling the value of this vital check is lost; it is equally important that the examiner, who need not be a medical practitioner, is well-versed in the technique.

Examination

at Birth

The infant, preferably after a feed or during a sleep, is undressed in a warm room and placed on a firm mattress or a board covered with a folded blanket. The examiner may either stand or sit, and reviews the baby for any skeletal skew, such as plagiocephaly, a ‘bat ear’, thoracic moulding, torticollis or scoliosis, pelvic obliquity or limb length disparity. Deformities of the feet, such as calcaneovalgus or fixed inversion (‘club foot’) should alert the examiner to the possibility of a hip abnormality. Leg lengths should be assessed, looking for asymmetry produced by loss of the normal hip physiological flexion deformity. an adduction posture or a relative lack of movement of one or other limb. Disparity in the thigh skin folds is

Malcolm F. Macnieol MBChB, BSe(hons), MCh, FRCSEB, Orthopaedic Department, Princess Margaret Rose Orthopaedic Hospital. Fairmilehead. Edinburgh EHIO 7ED. UK.

only suspicious if the crease is deep and extends circumferential to the buttock or posterior thigh. Since the neonatal hip displaces posteriorly most readily, the thigh should be gently pistoned backwards and forwards, incorporating abduction or circumduction movement to reduce the dislocated hip (‘entry clunk ‘). It is helpful if the thumb is placed against the inner aspect of the femur and the knee is fully flexed, thus relaxing the iliotibial tracts, and thereby reducing the chance of producing a soft tissue click from the region of the greater trochanter or the knee. The ‘exit clunk’ of a dislocatable hip is more readily appreciated if the thigh is adducted and slightly internally rotated, and a better perception of the clunk is aflorded if the other hand is placed behind the pelvis (Fig. 1). If the femoral head is frankly dislocated, there will be no exit clunk but the hip may be felt to reduce with a similar clunk if the proximal thigh is pulled forwards gently. This manoeuvre is improved if a finger is placed over the greater trochanter, giving more control and feel, and also if the thigh is abducted during the procedure since this tightens the adductors and makes any clunk more noticeable. The entry clunk is often apparent during circumduction of the hips, and both legs can be examined together during this procedure. In high dislocations the presence of an unyielding posterosuperior obstruction, typically the limbus (an abnormal fold of capsule and its associated quadrant of labrum) may muffle or prevent the sense of an entry clunk. The appreciation that a hip may occasionally be irreducible, or may only be ‘reduced’ by entrapping an abnormal fold of soft tissue within the acetabulum is particularly important. Forced positioning of the leg must be avoided at all costs and in this context the hip that will not abduct readily beyond 60” should be treated with great caution. In every case the infant’s hips should be re-checked

246

CURRENT

Fig. l-An trochanter one hand

ORTHOPAEDICS-CHILDREN

entry clunk is produced by pulling the abducted femur forwards (A). An exit clunk occurs if the dislocateable hia can be subluxed and stabilising the pelvis wrth the other hand (6).

by pressure from the middle finger over the greater by pressure over the inner thigh, using the thumb of

on at least one occasion before discharge home. This proves difficult logistically if the mother is allowed a 48-hour discharge, more common now than formerly. If there is concern about the hips, which cannot be resolved satisfactorily on repeated examination, two approaches should be adopted. Firstly, the mother and baby may be kept in for a further assessment, or the infant is brought back for re-examination in the first week. This is not always possible to ensure, and in these cases splintage is sometimes advised as a precaution. Secondly, various adjunctive tests may be used in order to establish the diagnosis more certainly.

1

Radiography A properly centred antero-posterior radiograph of the neonatal pelvis will determine whether the suspicious hip is ‘standing off’, with a medial gap of greater than 5 mm (Fig. 2). A metre focal distance should be ensured when taking the film, and the legs should be held gently parallel to the spine with the patellae pointing forwards. As the ratio of the medial to the superior gap increases towards parity the hip is more and more obviously displaced, making splintage advisable. Scrutiny of the data presented in the literature which purports to refute the value of the neonatal radiograph shows most of it to be anecdotal and a careful statistical evaluation” confirmed the relative precision of this investigation. The major limitation in the use of radiographs is that only those babies that are considered to be clinically abnormal, and perhaps those with predisposing features (Table l), are assessed in this way and therefore some unstable hips may be missed. This is a serious limitation and it must be appreciated that the radiograph will only improve the accuracy of diagnosis in that cohort of babies with suspicious hips. While it has been proposed that radiographs are of greater value later in the first year of life, artefacts such as pelvic rotation and asymmetrical leg positioning may be confusing, as will the variable onset of capital femoral ossification. Logistically, it is also

Fig. Z-The medial gap (M) is normally less than 5 mm, using a 1 metre focal distance. As the femur of the unstable hip lies in a superolateral position compared to the normal, there is a progressive lessening of the S/M ratio with increasing laxity.

Table 1 Predisposing

factors

First born Female Breech presentation Abnormal pregnancy Associated deformity Skeletal skew Positive family history

impossible that radiography can be considered effective screening test for every infant.

an

Ultrasound This investigation is non-invasive and gives a dynamic portrayal of hip displacement in association with any soft tissue distortion. The technique has excited great interesP,” but its value in lowering the late diagnosis rate has yet to be established.” Furthermore. it is open

EARLY

to the same practical restrictions as radiography, namely that not all infants can readily be assessed. But it is of value as a complementary test and offers an excellent monitor of the hips under treatment, or those referred later in the first year of life. Vibration emission’ and magnetic resonance imaging” offer different methods of screening the hip during infancy. The former has yet to prove its worth but may help to discriminate between an innocent click and the genuine clunk of displacement. Magnetic resonance imaging gives details of the capsule, limbus and transverse acetabular ligament in the older child. If the capsule is demonstrated to be adherent to the ilium forming an early false acetabulum. open reduction will almost certainly be required.

Treatment at Birth A policy of prone lying is recommended for all infants. irrespective of the condition of their hips. This encourages abduction of the legs and will reduce the frequency of habit side-lying, which can promote the squint baby syndrome or skeletal skew seen later in the first year of life. Abduction of the hips is also ensured by encouraging the parents to sit the baby on their hips with the legs straddling the trunk. Double nappies in conjunction with prone lying are insufficient for the proven, unstable hip, but their use is

MANAGEMENT

OF CDH

247 -

encouraged in selected cases where other factors at birth are a cause for concern. For the dislocatable hip with an exit clunk, or the readily reducible hip, a Pavlik harness is recommended for 2 or 3 months respectively. The splint should be applied by an experienced clinician or physiotherapist. and re-checked every 24 weeks. When mother or baby tolerate the restriction of sptintage poorly. review may have to be individualised and occasionally a different form of splint is required. A pelvic radiograph at 1 month of age, with the harness in place, will confirm that the hips are reduced. Posterior subluxation must be guarded against by controlling abduction of the hips more fully using a terry towel nappy placed over a disposable diaper (Fig. 3). Stability can be assessed by palpating the position of the greater trochanters and a push-pull provocation of the hips. Excessive flexion (more than 120”) must be avoided, and it is important to leave enough slack in the tapes of the harness to allow movement of the hips within a stable arc (50-80” of abduction and 90..-130” of flexion). A loosely applied Malmo (von Rosen) splint is sometimes necessary for the dislocated hip at birth, or where there is concern about the efficacy of the harness. However, the Malmo splint is usually exchanged for the Pavlik harness at I month of age, and splintage is continued for a minimum of 3 months in the small proportion of unstable cases. If there is still concern about the hips at the end of the 3rd month. the harness should be kept in place for a further few months, gradually weaning the child from the splintage during the day. After 6 months of age the infant tolerates the harness poorly and this form of splintage ceases to be particularly efficient. Regular monitoring of these commercial splints is essential, and the mother must be conversant with the necessary restrictions in bathing and clothing. If ;I health visitor, district nurse or ‘mothers” club’ can offer help at home, then the difficulties in nursing. and in bonding to the baby, are lessened. Alternative splints such as the Craig (Aberdeen) splint and Frejka pillow are placed over the nappy (and often over the clothes) so that they are inevitably removed frequently. The more unstable hip may then be allowed to displace, hindering the development of the normal coaptive relationship between femoral head and acetabulum.

Problems in Treatment at Birth The principal problems in neonatal therefore be summarised as: 1. missing the diagnosis 2. failing to provide 3 months. Fig. S-The Pavlik harness should ensure the maintenance of safe ranges of abduction and flexion of the hips. A double nappy may be placed over the disposable nappy in order to augment abduction.

at birth effective

management

splintage

for

can

2-

The major complication at this age is ischaemic damage to the cartilagenous femoral head and growth plate. These lesions are entirely iatrogenic and can be

248

CURRENT

ORTHOPAEDICS-CHILDREN

avoided by careful positioning of the hip within (the frog physiological ranges. Forced abduction position) in rigid splints is a recipe for disaster. Likewise, the hip that is convincingly displaced, either radiographically or sonographically, should never be forced into a ‘reduced’ position. This manoeuvre is analogous to forceably extending the knee locked by a displaced bucket handle meniscal tear, with the subsequent application of a plaster cylinder. An appreciation that there may be a fixed obstruction, making the hip effectively irreducible, is an essential aspect in the careful management of the neonatal hip. Follow-up arrangements for all hips under treatment, and also those where any suspicion about stability and development has been raised. should be ensured not only at the 1st month but also as the 3rd. 6th, and 10th months of life. This will ensure that all abnormal hips are under regular review prior to walking. Thereafter, a further appointment for those babies that are developing normally should be provided at 18 months, with subsequent annual review in that small proportion of hips where there is continuing concern about acetabular development or proximal femoral growth.

Treatment During Infancy (3-12 months) Although the ideal age for treatment is during the 1st week of life, diagnosis and reduction of an unstable hip at a later stage in the 1st year of life is still to be preferred to the presentation after the child is walking. Palmen” has described how abnormal hips missed at birth are now being referred at an earlier age for orthopaedic treatment. The increasing vigilance and training of community medical personnel is resulting in many more cases being diagnosed secondarily at 4-8 months of age. rather than at 18 months or older.’ There is also some evidence to suggest that the later presentation of a dysplastic or dislocated hip may reflect, in some cases, not so much an inadequate neonatal examination, but the development of a measurable, clinical abnormality sometime after birth (development dysplasia). Hence, screening of the hips both at birth and later during the 1st year of life is mandatory, ideally at lo-12 weeks and again at 10 months of age. Progressively, the displaced hip in the older infant comes to present with a loss of movement and shortening of the affected limb, rather than a feeling of instability. A common confusion occurs in an intermediate group of infants in whom the total range of movement is equivalent in each hip, but where the arcs of motion differ in relation to the long axis of the body. This change in spatial orientation makes the hip on the side of the more adducted leg appear ‘dysplastic’ with apparent shortening of the leg and even an asymmetry of the thigh skin creases. A generalised ‘skeletal skew”” may become established until walking age. Differentiation of this transient. developmental condition from true displacement of

the hip is sometimes difficult and the two syndromes merge with each other producing different degrees of dysplasia. The infant should be examined both supine and prone (Fig. 4) for it is all important to establish not merely the apparent restriction of abduction but the total arcs of movement of both hips. If these are the same, but are only spatially different in relation to the axial skeleton, then the likelihood of significant pathology affecting the hip is much reduced. The mother may remark upon the fact that her child prefers to lie on one side rather than the other, and in these cases the uppermost hip is usually the one that appears dysplastic as it lies in an adducted position. The management of skeletal skew. with its apparent hip dysplasia and the associated abduction contracture of the contralateral hip, is firstly to ensure that the child is not being allowed to lie constantly on one side. It is rarely necessary to investigate further with an arthrogram, and even more unusual for abduction splintage to be necessary. Indeed. there is a risk of producing avascular damage to the adducted hip if splintage is applied firmly and hence it is important that this self-limiting condition is recognised as benign. A wait-and-see policy is justifiable in most cases, with radiographic review at ?-monthly intervals. When true instability of the hip is present. the dysplastic features include a diminution or absence of the proximal femoral ossification centre. a true lateralisation of the femoral head, and an increased inclination of the acetabular roof. Arthrographic features of instability at this age include medial pooling of the contrast medium, and deformation of the labrum which may show no ‘rosethorn’ superiorly. Further displacement of the femoral head will then cause it to lie above Hilgenreiner’s line and eventually the labrum ceases to envelop the femoral head, with the appearance of a limbus interposed around the posterosuperior quadrant of the acetabulum. Displacement of the hip tends to progress with age, although in a proportion of cases the soft tissues appear to restrict the migration of the head. which remains in a subluxed position. Later, this becomes an established, subluxated position, where deformation of the femoral head and acetabulum prevent a congruous reduction. even by open operation. Thus the precise changes in morphology of the soft tissues of the hip joint vary from case to case with some femoral heads resting within a completely separate false acetabulum. and others producing significant compression over the lateral aspect of the acetabulum.

Reduction of the Femoral Head Reduction of the femoral head must never be forced, and it is advisable to precede any manipulation with a period of 223 weeks of skin traction. This becomes very important if treatment is considered between the ages of 3 9 months. when ossification of the femoral

EARLY

Fig. 4-Prone-lying is extended.

discloses a left hip abductor

contracture

MANAGEMENT

(A) vvhich prevents the thigh from being adducted

OF CDH

249

(B) when the hip

Fig. 5-A left hip arthrogram reveals abnormal pooling of contrast medial to the femoral head, an interposed soft tissue filling defect (the limbus) superiorly, an hour-glass constriction of the cal lsule and mild deformity of the femoral head (A). The appearances 10 years after open reduction (B)

Table Z-Scheme

for splintage of the unstable hip

Treatment

Overhead skin traction :open Reduction of hip closed Full hip spica+ (change monthl)) Pantaloon spica Abduction brace--full time night time Average splintage time Likelihood of later pelvic osteotomy * Mandatory if closed reduction + Hips flexed at least 60” and

.4ge of child 6--l? months

I?--24 months

7 weeks 7: I I 2 months

4 weeks* I:3 1 3 months

I month 2 months I month 5 months 20 %,

I 2 months 3 months 1 month 8 months 50 “/o

contemplated

abducted 60”.

head is minimal and avascular necrosis is readily produced by compressive forces. As secondary obstructions become more likely with progressive displacement of the femoral head. the incidence of open

reduction will rise in proportion to the age of the child. Arthrography is a useful method of identifying any obstruction, and is preferred to a trial of closed reduction which may damage the femoral head and can lead to a high incidence of late subluxation. An eccentric reduction cannot be accepted and if the arthrogram indicates the interposition of the limbus (Fig. 5) or a significant degree of medial pooling owing to infero-medial soft tissues, immediate open reduction is advisable. The limbus need not be removed if it can still be hooked out of the socket and brought over the circumference of the femoral head. However, in the older child the limbus ceases to be so malleable although it can still be delivered over the femoral head in certain cases if radial cuts are made in that structure. Before walking age. a medial approach to the hip is often possible. However, this approach is ineffectual when a rigid deformed limbus is present and may additionally endanger the vascularity of the femoral

2%

CURRENT

ORTHOPAEDICS-CHILDREN

Fig. 6-An unstable and dysplastic right hip (A) was treated by innominate later, although slight coxa magna is evident (C, D, E).

head. A scheme for splintage of the hip is illustrated, with the legs initially flexed 90” and abducted approximately 60” (Table 2). Progressively, the hips can be extended to a position of approximately 4.5” of flexion, with abduction of approximately 60”. The effects of femoral anteversion are annulled by this position of flexion and abduction. and hence internal rotation of the thighs is unnecessary. A later pelvic osteotomy is unlikely when the child is treated before walking age but after that age the secondary deformation of the femoral head and acetabulum, together with the lessening response of the triradiate cartilage to effective reduction, make a later in-

osteotomy

(B) producing

satisfactory

appearances

nominate osteotomy more likely (Fig. 6). Fixed shortening of the affected limb will also make traction valueless preoperatively so that femoral shortening become more likely if some degree of restitution is to be achieved in the older child.

References I. Hadlow

V. Neonatal screening for congenital the hip. A prospective 21 year survey. J Bone 1989: 718: 740-3 2. Macnicol M F. Results of a 15 year screening for neonatal hip instability. J Bone Joint Surg 1057 60

disiocation of Joint Surg programme 1990; 72B:

EARLY 3. Bertol P, Macnicol M F, Mitchell G P. Radiographic features of neonatal congenital dislocation of the hip. J Bone Joint Surg 1982; 64B: 176-179 4. Graf R. Fundamentals of sonographic diagnosis of infant hip dysplasia. J Pediatr Orthop 1984; 735-740 5. Tannis D, Starch K. Ulbrich H. Results of newborn screening for congenital dislocation of the hip with and without sonography and correlation of risk factors. J Pediatr Orthop 1989: 10: 145-8 6. Clarke N M P, Clegg J, Al-Chalabi A N. Ultrasound screening of hips at risk for CDH. Failure to reduce the incidence of late cases. J Bone Joint Surg 1989: 71B: 9--12

14

MANAGEMENT

OF CDH

251

7. Cowie G H, Mollan R A B, Kernohan W G, Bogues B A. Vibration emission in detecting congenital dislocation of the hip. Orthop Rev 1984; 13(l): 30-35 8. Bos C F A, Bloem J L. Treatment of dislocation of the hip, detected in early childhood, based on magnetic resonance imaging. J Bone Joint Surg 1989; 71A: 1523-1529 9. Palm& K. Prevention of congenital dislocation of the hip: The Swedish experience of neonatal treatment of hip joint instability. Acta Orthop Stand 1984: Suppl 208 10. Macnicol M F. Congenital dislocation of Jhe hip. In: Bennet G C (ed). Paediatric hip disorders. Oxford: Blackwell Scientific Publications, 1987. pp. 64113

COR

6