SPECIAL POINTS IN THE INVESTIGATION OF HIP COMPLAINTS

Setting the pelvis square

This is an important preliminary step. Determine from the position of the anterior superior iliac spines whether or not the pelvis is lying square with the limbs (Fig. 17.1). If it is not, an attempt is made to set it square. If this is impossible it means that there is incorrectable adduction or abduction at one or other hip (or, rarely, a severe and rigid curvature of the spine): in that event the fact that the pelvis is tilted should be noted and borne in mind during the subsequent steps of the examination.

Fig. 17.1 First step in the clinical examination of the hip: determining the lie of the pelvis.

Measuring the length of the limbs

Methods of measuring the lower limbs are often confusing to the uninitiated, but it is important that they should be properly understood. Accuracy in measurement is of more than academic significance; it is of practical importance when corrective operations or adjustments to the shoes are contemplated. Limb length can be measured clinically within an error of one centimetre. If greater accuracy is needed, radiographic measurement (scanography) is recommended.

It is necessary to measure, first, the real or true length of each limb. Secondly, it is necessary to determine whether there is any ‘apparent’ or false discrepancy in the length of the limbs from fixed pelvic tilt (Fig. 17.2). Whereas it is always necessary to measure the true length, it is necessary to measure ‘apparent’ discrepancy only when there is an incorrectable tilt of the pelvis.

Fig. 17.2 ‘Apparent’ or false discrepancy in limb length is caused entirely by incorrectable lateral tilting of the pelvis, which effectively abducts one hip and adducts the other hip A. If the pelvis is square with the limbs there can be no ‘apparent’ discrepancy in limb length B.

Measurement of true length. Ideally it would be desirable to measure from the normal axis of hip movement – that is, the centre of the femoral head – but since there is no surface landmark at that point it is impracticable to do so clinically. The measurement is therefore taken from the nearest convenient landmark – namely, the anterior superior spine of the ilium. Distally, measurement is usually made to the medial malleolus.

It should be noted that the anterior superior spine is well lateral to the axis of hip movement. This is of no consequence if the angle between limb and pelvis is the same on each side. But it will render the measurements fallacious if the angle between limb and pelvis is not the same on each side. This will be understood best by reference to Fig. 17.3A. It will be seen that abduction of a limb brings the medial malleolus nearer to the corresponding anterior superior spine, whereas adduction of the limb carries the medial malleolus away from the anterior superior spine. Thus if measurements are made while the patient lies with one hip adducted and the other abducted (a common posture in cases of hip disease) inaccurate readings will be obtained: the length will be exaggerated on the adducted side and underestimated on the abducted side.

Fig. 17.3 A Since the anterior superior spine is lateral to the hip joint abduction approximates the foot to it and adduction carries the foot away from it. For this reason measurements of true length, taken from the anterior superior spine, are inaccurate if the angle of abduction or adduction is not equal on the two sides. B Correct way of measuring the true length when there is a fixed adduction deformity of one hip. The other hip must be adducted through an equal angle. (Position of tape measure shown by interrupted lines.)

The rule is, therefore, that to obtain an accurate comparison of their true length by surface measurement the two limbs must be placed in comparable positions relative to the pelvis. Thus if one limb is adducted and cannot be brought out to the neutral position, the other limb must be adducted through a corresponding angle by crossing it over the first limb before the measurements are taken (Fig. 17.3B). Similarly, if one hip is in fixed abduction the other must be abducted through the same angle before the measurements of true length are made.

Fixing the tape measure at the anterior superior spine. A flat metal end (as found on the ordinary tailor’s measure) is essential. The metal end is placed immediately distal to the anterior superior spine and is pushed up against it. The thumb is then pressed firmly backwards against the bone and the tape end together (Fig. 17.4). This gives rigid fixation of the tape measure against the bone and minimises any error in measurement.

Fig. 17.4 Fixing the tape measure at the anterior superior spine.

Taking the reading at the medial malleolus. The tip of the index finger is placed immediately distal to the medial malleolus and pushed up against it. The thumb nail is brought down against the tip of the index finger so that the tape measure is pinched between them (Fig. 17.5). The point of measurement is indicated by the thumb nail.

Fig. 17.5 Taking the measurement at the medial malleolus.

Determining the site of true shortening. If measurements reveal real shortening of a limb it is necessary to determine whether the shortening is above the trochanteric level (suggesting an affection in or near the hip), or below the trochanteric level (suggesting a disorder of the limb bones).

Shortening above the greater trochanter. Tests for shortening above the trochanteric level are: the measurement of Bryant’s triangle, Nelaton’s line, or Schoemaker’s line.

In modern practice these tests are seldom used, since the information they provide can be supplied from simpler clinical observations or more accurately from radiographic measurements. They all depend on comparing the relative distance between the tip of the greater trochanters and the iliac crests. This can be quickly achieved with the patient supine, by using both hands with the thumbs placed on the greater trochanters and the tips of the index fingers on the anterior superior iliac spines. Any discrepancy between the two sides should then become apparent.

Shortening distal to the trochanter. True shortening is sometimes caused by an abnormality below the trochanteric level, such as a congenital defect of development, impaired epiphysial growth, or a previous fracture with overlapping of the fragments. To investigate this possibility individual measurements should be made of the femur (tip of greater trochanter to line of knee joint) and of the tibia (line of knee joint to medial malleolus) on each side and by flexing the knees to 90 ° and observing whether the shortening lies above the knee or below it (Gallenzi test).

Measurement of ‘apparent’ discrepancy in limb length. ‘Apparent’ or false discrepancy in limb length is due entirely to incorrectable sideways tilting of the pelvis (Fig. 17.2A). The usual cause is a fixed adduction deformity at one hip, giving an appearance of shortening on that side, or a fixed abduction deformity, giving an appearance of lengthening. Exceptionally, fixed pelvic obliquity is caused by severe lumbar scoliosis.

To measure apparent discrepancy the limbs must be placed parallel to one another and in line with the trunk. Measurement is made from any fixed point in the midline of the trunk (for example, the xiphisternum) to each medial malleolus (Fig. 17.6).

Fig. 17.6 For correct measurement of ‘apparent’ discrepancy in limb length the limbs must be parallel and in line with the trunk. (Position of tape-measure shown by interrupted lines.) In this example the pelvis is raised on the left, a situation that is commonly due to fixed adduction at the hip.

If there is a discrepancy of true length it must be allowed for when ‘apparent’ discrepancy is determined. As already noted above, there is no need to measure for apparent discrepancy if the pelvis lies square with the limbs, as determined from the position of the two iliac crests.

Examination for fixed deformity

Contracture of the joint capsule or of muscles may cause fixed deformity at the hip, preventing its being placed in a neutral position. Fixed flexion, fixed adduction, and fixed lateral rotation are common in some forms of arthritis.

Fixed adduction deformity. This is detected by judging the relationship between pelvis and limbs. It will already have been noted at an earlier stage of the examination. If fixed adduction is present the transverse axis of the pelvis (as indicated by a line joining the two anterior superior spines) cannot be set at right angles to the affected limb, but lies at an acute angle with it.

Fixed abduction deformity. The angle between the transverse axis of the pelvis and the limb is greater than 90 °.

Fixed flexion deformity. This is determined by a manoeuvre known as Thomas’s test.

Principle of Thomas’s test. If there is a fixed flexion deformity at the hip the patient compensates for it, when lying on the back, by arching the spine and pelvis into exaggerated lordosis, as shown in Fig. 17.7A. This allows the affected limb to lie flat on the couch. To measure the angle of fixed flexion deformity it is necessary to correct the lumbo-pelvic lordosis. This is done by flexing the pelvis (and with it the lumbar spine) by means of the fully flexed sound limb (Fig. 17.7B).

Fig. 17.7 Thomas’s test for fixed flexion deformity. A Flexion deformity masked by arching of spine and pelvis. B Deformity revealed by flexing the sound hip and, by continuing the flexion force, correcting the arching of spine and pelvis.

Technique of the manoeuvre. One hand is placed behind the lumbar spine (between it and the couch) to assess the degree of lumbar lordosis. If there is no lordosis when the affected limb lies flat on the couch there can be no fixed flexion deformity and there is no need to proceed with the test. If there is excessive lordosis, as indicated by arching of the back (Fig. 17.7A), it is corrected in the following way: The sound hip is flexed to the limit of its range. The limb is then pushed further into flexion, thereby rotating the pelvis on a horizontal transverse axis until the arching of the spine is obliterated. During this manoeuvre the thigh of the disordered limb, if in fixed flexion, is automatically raised from the couch as the lumbar lordosis is reduced (Fig. 17.7B). The angle through which the thigh is raised from the couch is the angle of fixed flexion deformity.

Fixed rotation deformity. The most reliable index of the rotational position of the thigh is the patella, which normally points forwards when the hip is in the neutral position. If there is fixed lateral rotation or fixed medial rotation the limb cannot be rotated to the neutral position, with the patella directed forwards. The angle by which it falls short of the neutral when rotated as far as possible is the angle of fixed rotation deformity.

Movements

The accurate determination of hip movements demands much care, because restriction of hip movement is easily masked by movement of the pelvis. It is therefore essential to place one hand upon the pelvis to detect any movement there, while the other guides and supports the limb.

Flexion. The range of hip flexion is best demonstrated by flexing the hip and knee together; not by lifting the leg with the knee straight. Movement of the pelvis is best detected by grasping the crest of the ilium (Fig. 17.8). Only in this way is it possible to distinguish between true hip movement and the false flexion imparted by rotation of the pelvis. The normal range of true hip flexion is about 130 °, but it varies according to the build of the patient.

Fig. 17.8 Testing hip flexion. The right hand supports the limb while the left hand grips the ilium to detect incipient rotation of the pelvis. Hip and knee are flexed together.

Abduction. The limb to be tested is supported by one hand while the other hand bridges the pelvis from anterior superior spine to anterior superior spine (Fig. 17.9). In this way true abduction at the hip can be differentiated from the false abduction that is imparted by tilting of the pelvis. The normal range of true abduction at the hip is 30 ° to 35 ° (more in children).

Fig. 17.9 Testing abduction of the hip. The right hand supports the limb while the left, bridging the two anterior superior spines, is ready to detect tilting of the pelvis. Adduction is tested in the same way.

Abduction in flexion. This is often the first movement to suffer restriction in arthritis of the hip. The patient flexes his hips and knees by drawing the heels towards the buttocks. He then allows the knees to fall away from one another towards the couch (see Fig. 17.11B). The normal range is about 70 ° (90 ° in young children).

Fig. 17.10 A Negative Trendelenburg test. The hip abductors are acting normally, tilting the pelvis upwards when the opposite leg is raised from the ground. B Positive Trendelenburg test. The hip abductors are unable to control the dropping of the pelvis when the opposite leg is raised. The pelvis tilts down instead of upwards.

Adduction. The limb to be examined is crossed over the other limb. Again care must be taken to differentiate between true adduction and the false movement imparted by tilting of the pelvis. The normal range of adduction is about 25–30 °.

Lateral rotation and medial rotation. Judge the range by an imaginary pointer thrust axially into the patella, not by the position of the foot. The normal range both of medial and of lateral rotation is about 40 °.

Extension. Contrary to what has often been written, the range of extension at the hip is nil. Extension of the hip joint beyond the neutral position is prevented by the strong anterior capsule and reinforcing Y-shaped ligament. Seeming backward movement of the thigh is in fact contributed entirely by rotation of the pelvis and extension of the spine, not by extension at the hip joint proper.

Examination for postural stability: the Trendelenburg test

The Trendelenburg manoeuvre is a test of the stability of the hip, and particularly of the ability of the hip abductors (gluteus medius and gluteus minimus) to stabilise the pelvis upon the femur when the subject is standing upon the one leg.

Principle of the test. Normally, when one leg is raised from the ground the pelvis tilts upwards on that side, through the action of the hip abductors of the standing limb (Fig. 17.10A). (This automatic mechanism allows the lifted leg to clear the ground in walking.) If the abductors are inefficient they are unable to sustain the pelvis against the body weight and it tilts downwards instead of rising up on the side of the lifted leg (Fig. 17.10B).

Fig. 17.11 Congenital dislocation of the right hip. A The right lower limb was slightly shorter than the left, as suggested here by the typical extra skin folds in the thigh. B shows the reduced range of abduction of the affected hip – another typical and important diagnostic feature.

Technique. Stand behind the patient. Instruct him first to stand upon the sound limb and to raise the other from the ground. Having thus got the idea of what he is required to do, he should now stand on the affected leg and lift the sound leg from the ground. By inspection, or by palpation with a hand upon the iliac crest, observe whether the pelvis rises or falls on the lifted side. Remember that the limb upon which the patient stands is the one under test. If the pelvis rises on the opposite side (normal) the test is negative (Fig. 17.10A). If it falls, the test is positive (Fig. 17.10B); in other words the abductor muscles are incapable of stabilising the pelvis upon the femur.

Causes of positive Trendelenburg test. There are three fundamental causes:

1 paralysis of the abductor muscles (example – poliomyelitis)

2 marked approximation of the insertion of the abductor muscles to their origin by upward displacement of the greater trochanter, so that the muscles are slack (examples – severe coxa vara; developmental dislocation of the hip)

3 absence of a stable fulcrum about which the abductor muscles can act (example – ununited fracture of the femoral neck).

Sometimes two of these factors may operate together: for instance, in a case of upward dislocation of the hip there may be an unstable fulcrum as well as approximation of the origin of the abductor muscles to their insertion.

DEVELOPMENTAL DYSPLASIA OF THE HIP

The term developmental dysplasia of the hip includes congenital dislocation of the hip, nearly always diagnosed either within a few days of birth or within the first two years of life; and dysplasia of the hip in adults, characterised by shallow configuration of the acetabulum, defective congruity between the femoral head and the socket, and a predisposition to osteoarthritis in middle or later life. Despite a trend towards re-naming congenital dislocation of the hip as developmental dysplasia of the hip, the title ‘congenital dislocation’ of the hip is so well established that it seems unnecessary to discard it. That title is therefore retained here for dislocation diagnosed in infancy.

CONGENITAL DISLOCATION OF THE HIP

This is a spontaneous dislocation of the hip occurring either before or during birth or shortly afterwards. In Western races it is one of the commonest of the congenital skeletal deformities affecting 1 in 1000 neonates: it is also of special importance because neglect or inefficient treatment incurs the penalty to the patient of lifelong crippling.

Cause. Much remains to be learnt, but it now seems to be clear that a number of factors are concerned in the causation – some genetic and some environmental. One such abnormality acting alone may not always be sufficient in itself to bring about dislocation, and it may well be that a combination of factors is often at work.

Pathology. The femoral head: In a case of persistent dislocation the bony nucleus appears late and its development is retarded. The femoral head is dislocated upwards and laterally from the acetabulum. The femoral neck: In most cases the neck is anteverted (directed forwards) beyond the normal angle for infants of 25 °. The acetabulum: The ossific centre for the roof of the acetabulum, like that for the femoral head, is late in developing. The bone slopes upwards at a steep angle instead of forming a nearly horizontal roof for the acetabulum. The cartilaginous part of the roof is often well formed at first, but if the dislocation is allowed to persist development does not proceed normally, and the socket assumes a shallow contour with steeply sloping roof. The fibro-cartilaginous labrum: The peripheral labrum which normally increases the depth of the developing acetabular socket is often folded into the cavity of the acetabulum to become a ‘limbus’ and may impede complete reduction of the dislocation The capsule: This is gradually elongated as the femoral head is displaced upwards.

Clinical features. Girls are affected six times as often as boys. In one-third of all cases both hips are affected. Unless it is specially looked for in infancy – as it always should be – abnormality may not be noticed until the child begins to walk. Walking is often delayed, and there is a limp or a waddling gait.

On examination at that time, the main features in unilateral cases are asymmetry (notably of the buttock folds), shortening of the affected limb (Fig. 17.11A), and restricted abduction in flexion. In bilateral cases the striking features are widening of the perineum and marked lumbar lordosis. The range of joint movements is full except for abduction in flexion, which is characteristically slightly restricted (Fig. 17.11B). In most cases the affected limb is abnormally mobile in its long axis (telescopic movement).

Imaging. Plain radiographs show three important features (Fig. 17.12):

Fig. 17.12 Congenital dislocation of the right hip in a child of 2. The three points to note are the retarded development of the capital epiphysis, the steeply sloping acetabular roof, and the lateral and upward displacement of the upper end of the femur.

These changes are not always shown conclusively before the age of 4 months.

Arthrography (radiography after injection of opaque fluid into the joint) is useful in showing the outline of the cartilaginous elements of the joint.

Ultrasound scanning allows the position of the femoral head and acetabular socket to be determined in the new-born, when radiographic examination tends to be inconclusive.

Diagnosis. In the new-born. Nearly always – though there are a few exceptions—dislocation or instability of the hip may be detected in the first few days of life by the diagnostic screening tests of Barlow or Ortolani (Fig. 17.13). In both tests the surgeon faces the child’s perineum and grasps the upper part of each thigh between fingers behind and thumb in front, the child’s knees being fully flexed and the hips flexed to a right angle (Fig. 17.14). While each thigh in turn is steadily abducted towards the couch the middle finger applies forward pressure behind the greater trochanter (Ortolani), and alternately the thumb, placed anteriorly, applies backward pressure while the thighs are adducted (Barlow). One of two abnormal states may be detected:

Fig. 17.13 Tests for instability or dislocation in the new-born infant. A Ortolani’s test. B Barlow’s provocative test.

Fig. 17.14 Examining the hips of a new-born infant for instability. While the hip is abducted through the full range forward pressure is applied by the middle finger behind the greater trochanter. For details, see text.

The manoeuvre must be combined with assessment of the range of abduction in flexion at each hip (Fig. 17.11B). If abduction is restricted it may indicate persistent or irreducible dislocation, and in such a case the absence of the characteristic jerk or jolt may mislead the observer into believing that all is well. In such a case, if unilateral, shortening may be observed when the knees are placed together, with the hips flexed.

In newborn infants radiography may be inconclusive because the high proportion of radiolucent cartilage in the femoral head and acetabulum makes interpretation difficult. It becomes diagnostic after the age of about 4 months. As the necessary skill in the technique is more widely acquired, ultrasound scanning has become increasingly important in diagnosis in early infancy.

In older children. Delay in beginning to walk or abnormality of gait in early childhood should always arouse suspicion. The most important clinical sign in children 1 or 2 years old is a restricted range of abduction when the hip is flexed (Fig. 17.11B). If for any reason suspicion arises that all is not well with the hips, radiographic examination must be insisted upon. In these older children radiography is always conclusive.

Course and prognosis. The earlier the dislocation is reduced the better the prognosis. Even under the best conditions only about half or two-thirds of the patients treated after the first year of life can be expected to remain permanently free from trouble. Gradual redislocation or subluxation is all too frequent, and pain from secondary degenerative changes often develops in middle adult life.

It is therefore important that, through careful examination of every newborn infant, congenital dislocation be detected within the first week of life, when simple treatment can nearly always assure normal development of the hip.

Treatment

This varies according to the age of the patient when advice is sought. Four groups will be discussed:

1 neonatal cases (instability or dislocation)

2 age 6 months–6 years

3 age 7–10 years

4 adolescents and adults.

Neonatal cases (within 6 months of birth). These are the cases in which instability or dislocation is found on neonatal screening, either by the Ortolani–Barlow test or by ultrasound examination. In most of these cases the hip becomes stable spontaneously within 3 weeks. Accordingly, there is much to be said for delaying a decision on definitive treatment until the time of reassessment three weeks after birth, when it will be found that a large proportion of the infants do not need treatment. In the interval between the first examination and the reassessment at 3 weeks the limbs are left free, though it seems sensible to advise the use of bulky double nappies to encourage abduction of the hips.

If at 3 weeks the hip is found to be stable, treatment is unnecessary, and the parents may be tentatively reassured. Nevertheless it is important that the child should be reviewed at the age of 5 or 6 months, when radiography gives conclusive findings, and again at 1 year of age.

If on the other hand the hip is still unstable at 3 weeks, splinting in the reduced position in moderate (not extreme) abduction for 3 months is recommended. Splintage may be by plaster of Paris or more frequently using the Pavlic harness (Fig. 17.15), which is more flexible than the previously used Denis-Browne or Van Rosen splints. The dynamic Pavlic splint has an adjustable harness that can maintain the hips in flexion while limiting adduction. Splintage should be continued for a minimum of 6 weeks or for as long as instability persists, though this carries an increasing risk of the development of avascular necrosis of the femoral head.

Fig. 17.15 Pavlik harness used for the management of the unstable hip in the neonatal baby. It holds both hips in flexion and abduction allowing all movements except extension and is worn full-time. It permits spontaneous reduction without forcible manipulation.

Age 6 months–6 years. This still forms a substantial group, but with more regular diagnosis in early infancy the proportion of patients treated as late as this should progressively decrease. There are three essential principles of treatment:

1 to secure concentric reduction

2 to provide conditions favourable to continued stability and normal development

3 to observe the hips regularly in order to detect any failure of normal development of the acetabulum and to apply appropriate treatment when necessary.

Reduction of dislocation. It is desirable whenever possible to obtain reduction by non-operative means, operation being used only when conservative methods fail. In practice, it is found that closed reduction is often possible in babies up to 18 months of age, but that thereafter the proportion that require operation progressively increases, so that operative reduction becomes almost routine after the age of 3 years.

Closed reduction. The standard practice is to apply weight traction to the limbs with the child either on a frame or in gallows (Bryant’s) suspension, and while traction is maintained, gradually to abduct the hips, a little more each day, until 80 ° of abduction is reached after 3–4 weeks. Cross traction by slings round the upper thighs may then be applied. In many cases reduction is obtained by this method alone. If, however, the hip is not reduced at 4 weeks an attempt is made to complete the reduction by gentle manipulation under anaesthesia. It is essential that reduction be complete, so that the femoral head fits the socket concentrically. If necessary, arthrography, CT scanning, or magnetic resonance imaging may be employed to establish whether reduction is complete or whether interposed soft tissue is blocking it.

If full reduction is secured, the limbs are immobilised for an initial period in plaster of Paris, usually in a position of moderate medial rotation and moderate abduction (Fig. 17.16): extreme positions must not be used. This has superseded the ‘frog’ position of right-angled flexion and abduction, formerly widely used, which has been found to prejudice the blood supply of the capital epiphysis of the femur, with risk of necrotic changes resembling those of Perthes’ disease.

Fig. 17.16 A method of holding the hips in moderate abduction and medial rotation. Extreme positions of abduction or rotation are nowadays avoided because of the risk of damaging the blood supply to the capital epiphysis of the femur.

Operative reduction. If reduction is not obtained by traction and abduction, with or without manipulation, or when a soft-tissue obstruction to reduction has been demonstrated by arthrography, operation should be undertaken without delay. At operation, it will usually be found that full engagement of the femoral head in the acetabulum is prevented by inturning of the acetabular labrum (limbus), or occasionally by a voluminous ligament of the femoral head or a tight psoas tendon. Any such obstruction is removed or released to allow the femoral head to be fully engaged. While the femoral head is exposed to view, note should be made of the angle of anteversion of the femoral neck. This will often be found to be increased beyond the normal angle of 25 °. At the completion of the operation the limbs are immobilised in plaster in the same way as after closed reduction.

Maintenance of stability. A major hazard to continued stability in a child whose hip dislocation has been concentrically reduced comes from excessive anteversion of the femoral neck, which is a common if not a constant feature in children beyond 18 months of age. Excessive anteversion has its main adverse effect when the child assumes the erect posture for walking: with the hip extended excessive anteversion brings the femoral head anteriorly, and radiographs may show it to lie eccentrically in the acetabulum. If uncorrected, this initial subluxation may progress eventually to redislocation.

The diagnosis of excessive anteversion is simple if operative reduction has been undertaken, for with the hip exposed the angle of anteversion can be measured under direct vision. When reduction has been by closed methods, however, diagnosis presents some difficulty – indeed to some extent it may be a matter of guesswork. Methods of radiographic measurement are available but they are not always easy to apply successfully in a small child and have been largely superseded. A more empirical method is often used: antero-posterior radiographs are taken with the hip first in the neutral position and then medially rotated. A more central position of the capital epiphysis in the acetabulum when the hip is medially rotated suggests that excessive anteversion is prejudicing stability. Definitive information on the angle of anteversion can best be gained from computerised tomography (CT scanning) or magnetic resonance imaging.

There are two methods of correcting excessive anteversion:

1 non-operative

2 operative (rotation osteotomy).

Non-operative management of anteversion. Long-continued harnessing of the hips in flexion and moderate abduction, a limited amount of walking being allowed, has been found to favour spontaneous correction of anteversion. Correction may, however, take a year or more.

Rotation osteotomy. Excessive anteversion is easily corrected by rotating the femur through an osteotomy at its upper end. The femur is divided a little below the trochanteric level to allow the shaft fragment to be rotated laterally in relation to the upper end of the femur. The fragments are then fixed with a plate and screws. After operation immobilisation in plaster is maintained until union occurs – usually a matter of about 6 weeks. Thereafter all splintage is discarded.

Counteracting defective development of the acetabulum. In a proportion of cases – greater when treatment has been started late than when it has been begun in the first year of life – the acetabulum fails to develop normally from the stimulus of the femoral head within it, and remains unduly shallow. The femoral head is not well contained within it, being partly uncovered by the acetabular roof. If this deficiency is not corrected the femoral head may become slowly displaced upwards, so that the joint is subluxated, the head no longer articulating congruously with the socket. The treatment of such acetabular deficiency is operative, and it should be carried out as soon as it is observed that this adverse situation has arisen. Mention will be made of four of the several operations that are available for improving the acetabulum:

1 osteotomy of the innominate bone (Salter’s pelvic osteotomy)

2 pericapsular osteotomy of the ilium (Pemberton’s pelvic osteotomy)

3 shelf acetabuloplasty (Wainwright’s shelf operation)

4 Chiari’s displacement osteotomy of the ilium.

Osteotomy of the innominate bone (Salter). The iliac bone is divided completely just above the acetabulum, the cut emerging at the greater sciatic notch. The whole of the lower half of the bone, bearing the intact acetabulum, is then sprung outwards and forwards, hinging at the symphysis pubis (Fig. 17.17A). The effect is that the femoral head is more fully covered by the roof of the acetabulum, and stability of the hip is correspondingly increased. This operation is most suitable for young children in whom the acetabular socket and femoral head are congruent.

Fig. 17.17 Four methods of improving a poorly developed acetabulum to provide better cover for the femoral head. A Salter’s osteotomy of the ilium. B Pemberton’s pericapsular osteotomy of the ilium. C Wainwright’s shelf acetabuloplasty. D Chiari’s pelvic displacement osteotomy. For details see text.

Pericapsular osteotomy of ilium (Pemberton). This operation has a similar aim of providing increased cover for the femoral head by the roof of the acetabulum. A curved osteotomy is made part-way across the thickness of the pelvic wall from the outer aspect of the ilium a few millimetres proximal to the attachment of the capsule to the upper margin of the acetabulum. The osteotomy extends to the triradiate cartilage, which forms a flexible hinge about which the roof of the acetabulum is deflected downwards over the femoral head. The triangular osteotomy gap is held open by bone obtained locally from the ilium (Fig. 17.17B). This operation is most suitable for young children in whom the acetabular socket is relatively shallow compared to the shape of the femoral head.

Cortical turn-down acetabuloplasty (Wainwright). This so-called shelf operation also has the aim of increasing the surface area of the acetabular roof. A sizeable area of the outer table of the ilium is turned down as a flap into contact with the upper and outer aspect of the capsule of the hip joint (Fig. 17.17C). The flap, thus reflected, is held in place by strut grafts. This operation is suitable mainly for adolescents and young adults.

Chiari’s pelvic displacement osteotomy. The iliac bone is divided almost transversely immediately above the acetabulum, and the lower fragment (bearing the acetabulum) is displaced medially (Fig. 17.17D). The cut surface of the upper fragment thus forms an extension of the acetabular roof, with capsule and newly formed fibrous tissue intervening. The operation is suitable mainly for adolescents and young adults.

Age 7–10 years. In these older children with untreated dislocations, the first point to be decided is whether or not treatment should be undertaken at all. In some of these children with well-developed false acetabula symmetrically placed on both sides, functional disability is slight, and appearance and gait may be acceptable. Accordingly it may often be wise to advise against attempted reduction of the dislocation. In contrast, there are others with high-lying femoral heads and poorly developed false sockets who can benefit greatly from operative reduction up to the age of 10 years or sometimes even later. This applies particularly when the dislocation is unilateral. Treatment in such cases entails open reduction of the dislocation, to accomplish which the femur may have to be shortened in the subtrochanteric region. Any excessive anteversion of the femoral neck is corrected at the same time by rotation at the site of bone resection. Either at the same time, or preferably later, one of the operations mentioned above for deepening the acetabulum (the Wainwright shelf operation or the Chiari operation) may be carried out. An obvious advantage of reducing the dislocation in these older children is that conditions are made suitable for replacement arthroplasty should the need for it arise in later life, whereas this presents substantial difficulties if a high dislocation remains unreduced.

Age 11 years onwards. After the age of 10 years, and often in younger children, treatment of freshly diagnosed congenital dislocation of the hip is not advised unless secondary degenerative changes lead to severe pain. If increasing pain justifies operative treatment, the choice of method depends largely upon whether the dislocation affects one or both hips. If only one hip is affected total replacement arthroplasty may sometimes be practicable once adult life is reached; but if not, consideration should be given to the advisability of arthrodesis, which can offer a satisfactory solution. If both hips are affected (Fig. 17.18), if it is practicable, replacement arthroplasty is usually to be preferred.

Fig. 17.18 Bilateral untreated developmental hip dysplasia in an adult. The left hip is completely dislocated, with failure of normal acetabular development, and the right hip shows dysplastic changes.

DYSPLASIA OF THE HIP IN ADULTS

The gene that is responsible for many cases of congenital dislocation of the hip may also cause dysplasia, or failure of normal development of the joint, that may not become apparent in childhood.

Hip dysplasia in adults may become symptomatic at any time from early adult life up till middle age, or later. The common presenting symptom is pain, usually in one hip, but often occurring later, or in lesser degree, in the opposite hip as well. Examination shows good mobility of the hip, but often with complaint of pain at the extremes of the range, especially of flexion and abduction. On radiological examination the affected acetabulum is seen to be shallow, often with a steeply sloping roof (Fig. 17.19). The femoral head does not fit concentrically in the acetabulum: it may be shown to be displaced slightly upwards and outwards, so that Shenton’s line – the normally smooth arch formed by the medial/inferior border of the femoral neck prolonged into the inferior border of the pubic ramus – is broken.

Fig. 17.19 Congenital dysplasia of the hip in a woman aged 42. Note that the acetabulum is very shallow. The femoral head is ill-formed and higher than normal. The cartilage space is greatly narrowed, indicating degenerative arthritis.

Dysplasia of the hip is important not only because it may cause pain and instability in its own right, but because it predisposes to the later development of degenerative arthritis, usually in middle life, with slowly increasing pain and difficulty in walking.

Treatment. Operative treatment is often appropriate, but it should be deferred until the disability becomes severe enough to demand it. The choice of operation is usually between osteotomy of the upper end of the femur to displace the femoral head and neck into more varus (Fig. 17.20), and pelvic osteotomy above the acetabulum to increase the coverage of the femoral head and improve stability of the hip (Fig. 17.17D). In patients with established arthritic changes total replacement arthroplasty of the hip may have to be recommended, even in patients who are relatively young.

Fig. 17.20 Diagrams to show how adduction (varus) osteotomy of the femur improves the containment of the femoral head in the acetabulum. Left – Site of bone wedge to be removed. Right – Gap closed after removal of wedge, so that femoral neck is turned down into varus. The osteotomy has the effect that the upper part (head and neck) of the femur is abducted in the socket, while the femoral shaft remains in the neutral position.

TRANSIENT SYNOVITIS OF THE HIP (Traumatic synovitis; transient arthritis; observation hip; irritable hip)

The so-called transient arthritis or synovitis of childhood is a short-lived affection of the hip of uncertain pathology, characterised clinically by pain, limp, and limitation of hip movements.

Cause. This is unknown. Injury is possibly a factor but the evidence in support of it is slender.

Pathology. This is unknown. Possibly there is a mild inflammation of the synovial membrane, initiated by minor injury; or perhaps a viral infection.

Clinical features. The condition is virtually confined to children under 10, especially boys. The child complains of pain in the groin and thigh and he is noticed to limp, sparing the affected leg. On examination the only physical sign is limitation of hip movements. Radiographs do not show any alteration from the normal.

Diagnosis. Transient arthritis of the hip is important only because it resembles clinically the earliest stages of pyogenic arthritis, tuberculous arthritis or of Perthes’ disease, before the characteristic radiographic features of those conditions have become apparent. Transient arthritis should be diagnosed only after the hip has recovered – never while the symptoms and signs are present. While the symptoms and signs last, the case should be regarded as one of suspected infective arthritis or Perthes’ disease and the child investigated fully to exclude these diagnoses. Ultrasound scanning may be indicated to identify any joint effusion which would require aspiration. Full recovery within a few weeks excludes more serious disease and justifies a retrospective diagnosis of transient synovitis.

Course. Full recovery, with return of a normal range of hip movements, invariably occurs within three to 6 weeks.

Treatment. Rest in bed until the pain has settled and movements have been restored is the only treatment required.

PYOGENIC ARTHRITIS OF THE HIP (General description of pyogenic arthritis, p. 96)

Pyogenic arthritis of the hip is uncommon. It occurs mostly in children, in whom it is often secondary to osteomyelitis of the upper end of the femur. Its features resemble those of pyogenic arthritis elsewhere; but in infants there are particular characteristics that require special description.

Pathology. Organisms (usually staphylococci or streptococci) may reach the joint directly through the blood stream, or the infection may spread from an adjacent focus of osteomyelitis of the femur. Rarely, a penetrating wound is responsible. In new-born babies the infection may enter through the umbilicus. There is an acute inflammatory reaction in the joint tissues, with an effusion of turbid fluid or pus. In favourable cases healing with restoration to normal can occur, but often the joint is permanently destroyed or damaged, and in older children and adults bony ankylosis may occur.

In infants bony ankylosis does not occur because the femoral head and the acetabulum are composed almost entirely of cartilage rather than of bone, but there may be total destruction of the developing femoral head, with secondary dislocation of the hip (pathological dislocation) (Tom Smith’s disease¹). The femur may remain short, from destruction of the upper femoral growth cartilage. Additional shortening will occur if the dislocation is allowed to persist and the femur to slide upwards on the ilium; so the discrepancy in length may be substantial by the time adolescence is reached.

Clinical features. The clinical features differ so much in infants and in older patients that separate descriptions are required.

Pyogenic arthritis of infants. The onset is within the first year of life. Often there has been a known septic lesion somewhere on the body (for example, umbilical sepsis), but it may have caused little anxiety. Then the child becomes unwell and pyrexial.

On examination it is not always apparent at first that the hip is the seat of the trouble. But careful examination will show thickening in the hip area, and movements of the joint are restricted, and disturb the child. Sometimes an abscess points at the skin surface in the buttock or thigh.

Imaging. In the early stages there is no alteration in the plain radiographs, but ultrasound scanning may show the hip joint to be distended with fluid (Fig. 7.13, p. 99). If the infection progresses to the stage of destroying the capital epiphysis of the femur, the ossific nucleus fails to appear as it should before the age of one year. In such a case subsequent radiographs may show gradual dislocation of the hip. This ‘pathological’ dislocation is distinguished from congenital dislocation by the facts that the acetabular roof is of normal shape and that the capital epiphysis is permanently absent (Fig. 17.21). Radioisotope scanning reveals increased uptake in the region of the hip.

Fig. 17.21 Old pyogenic arthritis of left hip in an infant (Tom Smith’s disease). The epiphysis of the head of the femur has been destroyed and the hip is dislocated. Note the almost normal appearance of the acetabular roof, which helps to distinguish this from a congenital dislocation. The normal hip is shown for comparison.

Pyogenic arthritis in older children and adults. The onset is acute or subacute, with pain in the hip made worse by attempted weight-bearing, reluctance to walk, and severe limp. There is constitutional illness with pyrexia. On examination there may be some fullness about the hip region from swelling of the joint. All movements of the hip are markedly restricted, and painful if forced.

Imaging. There may be no change on plain radiographs in the early stages, but ultrasound will demonstrate the presence of an effusion (Fig. 7.13, p. 99). There may be evidence of osteomyelitis in the upper metaphysis of the femur. Later, if the infection persists, there is rarefaction of bone about the hip, and the cartilage space is narrowed, indicating destruction of articular cartilage. Finally, there may be bony ankylosis of the joint (Fig. 17.22).

Fig. 17.22 Bony ankylosis of the hip caused by pyogenic arthritis. The infection spread to the hip from a focus of osteomyelitis in the upper metaphysis of the femur. This is a common outcome of pyogenic arthritis in older children and adults.

Radioisotope bone scanning shows increased uptake in the region of the hip.

Investigations in both the infantile and childhood forms of suspected septic arthritis are similar. There is a polymorphonuclear leucocytosis and the erythrocyte sedimentation rate and C-reactive protein level are raised. Blood cultures are taken and if ultrasound shows a joint effusion, aspiration of the joint is urgent yielding pus or turbid fluid from which the causative organism and its antibiotic sensitivities may be identified.

Treatment. Treatment is by appropriate antibiotic therapy, initially intravenously with a broad-spectrum cephalosporin, which can be changed later depending upon the nature of the infecting organism. Arthrotomy to permit open drainage and saline irrigation of the joint is preferred to daily aspiration in preventing the formation of adhesions and residual infection. Rest for the joint and relief of muscle spasm are best ensured initially by weight traction through adhesive skin strapping applied to the leg. When the infection has been overcome active movements are encouraged.

Pathological dislocation complicating pyogenic arthritis of infants, with total destruction of the upper femoral epiphysis. Definitive treatment of this rare but crippling condition must await adolescence. In childhood the aim of treatment is to prevent progressive upward displacement of the femur and thereby to minimise shortening. Provided the infection has settled, operation should be undertaken to deepen the acetabulum, to place the upper end of the femur within it and, if necessary, to lever down a ‘shelf’ of ilium over it, on the lines of the Pemberton osteotomy illustrated in Figure 17.17B. In adolescence, when the bones are nearing full development, arthrodesis may be recommended if the hip is painful. If the hip has fused spontaneously (Fig. 17.22) the situation is best accepted, provided that fusion has occurred in a good functional position.

TUBERCULOUS ARTHRITIS OF THE HIP (General description of tuberculous arthritis, p. 98)

The hip is one of the joints most frequently affected by tuberculosis. In Western countries, however, its incidence has declined so sharply that it is now seldom seen, and it is mainly confined to poorer countries or to immigrants from such countries.

Clinical features. The patient is usually a child – often 2 to 5 years old – or a young adult, often with a history of contact with a person with active pulmonary tuberculosis. The symptoms are pain and limp. The general health is usually impaired. On examination a thickening is often palpable in the region of the hip. All movements of the hip are limited, often markedly, and attempts to force movement provoke pain and muscle spasm. The gluteal and thigh muscles are wasted. A ‘cold’ abscess is sometimes palpable in the upper thigh or buttock. A tuberculous lesion may be apparent elsewhere in the body.

Imaging. Radiographic features. At first the changes are slight, but later there are fuzziness of the joint margins and narrowing of the cartilage space, indicating erosion of the articular cartilage (Fig. 17.23).

Fig. 17.23 Tuberculous arthritis of right hip in a more advanced stage. The cartilage has been destroyed and the articular surfaces of the acetabulum and femoral head have lost their sharp definition. The joint is permanently destroyed. The normal hip is shown for comparison.

MRI scanning can show signs of oedema in bone and soft tissues and will demonstrate the effusion and cold abscess. Radioisotope bone scanning shows increased uptake in the region of the hip.

Diagnosis. This is mainly from transient synovitis, Perthes’ disease (osteochondritis), low-grade pyogenic arthritis, and rheumatoid arthritis. Important features supporting a diagnosis of tuberculosis are: the presence of a tuberculous lesion elsewhere; a positive Mantoux reaction in children; a ‘cold’ abscess; a high erythrocyte sedimentation rate; and the typical histological appearance on biopsy of the synovial membrane.

Course and prognosis. In a reasonable proportion of cases, especially in children, the infection is aborted by treatment and a sound joint is preserved, provided there has been no destruction of cartilage or bone when treatment is begun.

Treatment. Essentially, treatment is the same as that for other tuberculous joints. The mainstay of treatment is a prolonged course of antibacterial agents, as described on page 102.

Local treatment is initially by rest for the hip, either in traction or in plaster. The subsequent treatment depends upon the progress made. If radiographs show no destruction of cartilage or bone, and if there is no evidence of deterioration full activity is gradually resumed.

On the other hand, if at the end of 3 or 6 months’ treatment radiographs show marked destruction of cartilage or bone (Fig. 17.23), there is no possibility of preserving the joint intact. The choice then lies between total replacement arthroplasty and arthrodesis. Arthroplasty should only be undertaken when the disease is quiescent, and will require the reintroduction of antibacterial drugs to cover the period of operation. In children such operations should be deferred until adolescence.

RHEUMATOID ARTHRITIS OF THE HIP (General description of rheumatoid arthritis, p. 134)

The hip joints often escape in cases of rheumatoid arthritis; but when they are affected the consequent disability is severe. The main features of the disease are like those of rheumatoid arthritis in general, as described on page 134.

Clinical features. The changes may affect one or both hips, in common with several other joints. The main symptoms are pain and limitation of movement, aggravated by activity.

On examination swelling is not obvious because the joint is so deeply situated; for the same reason the temperature of the overlying skin is not increased as it is in rheumatoid affection of the more superficial joints. The range of all hip movements is impaired and movement is painful if forced. Fixed flexion deformity or adduction deformity may develop. The gluteal and thigh muscles are wasted.

Imaging. Radiographic features. In the earliest stages there are no radiographic changes. Later, there is diffuse bone rarefaction in the area of the joint. Later still, destruction of articular cartilage leads to narrowing of the cartilage space between femur and acetabulum, often with inward protrusion of the softened medial wall of the acetabulum (Fig. 17.24).

Fig. 17.24 A Long-established rheumatoid arthritis of the hip, with destruction of the cartilage space. The marginal osteophytes indicate that osteoarthritis is becoming superimposed upon the old rheumatoid disease. B The left hip of another patient, showing marked protrusion of the femoral head into the softened acetabulum (protrusio acetabuli).

Investigations. The erythrocyte sedimentation rate is increased during the active stage. The latex fixation test and the Rose–Waaler test may be positive.

Course. The disease becomes inactive after months or years, but the hip is seldom restored to normal. In long-established cases degenerative changes are superimposed upon the original inflammatory condition, giving rise to secondary osteoarthritis (Fig. 17.24A).

Treatment. Medical treatment is the same as that for rheumatoid arthritis in general (p. 137). Local treatment for the hip joints depends upon the activity and severity of the inflammatory reaction. When the reaction is moderate or mild, exercises under physiotherapy supervision and active use within the limits of pain are encouraged. Intra-articular injections of hydrocortisone have sometimes given relief, but they cannot safely be repeated.

Operative treatment is justified when pain is severe and walking is limited to a few yards. Replacement arthroplasty (see Fig. 17.27A, p. 363) is the method of choice and can be expected to give as good results as in patients with osteoarthritis, though involvement of other joints in the lower limb may continue to impair mobility.

Fig. 17.27 A Total replacement arthroplasty. The femoral head is of metal, the socket of plastic. B Resurfacing (double cup) arthroplasty. Matching metal shells are used to resurface the femoral head and acetabular socket with cemented or cementless fixation.

OSTEOARTHRITIS OF THE HIP (General description of osteoarthritis, p. 140)

Osteoarthritis of the hip is a common cause of severe disablement, especially in the elderly. It is not uncommon even in younger patients, when it is usually secondary to previous injury or disease. Indeed operations for the relief of osteoarthritis of the hip now make up a substantial part of the work of an orthopaedic department.

Cause. It is sometimes regarded as a wear-and-tear process; but in fact it reflects an inability of articular cartilage fully to repair itself. Any injury or disease that damages the joint surfaces initiates or accelerates the process of degeneration. Common examples of such predisposing causes are fracture of the acetabulum, Perthes’ osteochondritis, slipped upper femoral epiphysis, and ischaemic necrosis (osteonecrosis) of part of the femoral head from any cause. In another group degeneration of the joint is secondary to a developmental imperfection (dysplasia) or congenital subluxation. In many cases there is no evidence of an underlying cause, and for want of any other explanation such cases are regarded as primary or idiopathic.

Pathology. The articular cartilage is worn away, especially where weight is transmitted. The underlying bone becomes hard and eburnated with subarticular cyst formation. Hypertrophy of bone at the joint margins leads to the formation of osteophytes.

Clinical features. The patient is usually elderly; but when osteoarthritis is secondary to previous hip disease or to injury it often arises in middle life or even earlier. There is pain in the groin and front of the thigh; often also in the knee. The pain is made worse by walking and eased by rest. Later, there may be complaint of stiffness, which manifests itself in everyday life by inability to reach the foot to tie the shoe laces or cut the toe nails. The symptoms tend to increase progressively month by month and year by year until they eventually cause severe painful limp and incapacity for normal activities.

On examination all hip movements are impaired. Limitation of abduction, adduction, and rotation is marked, but a good range of flexion is often preserved. Forced movements are painful. Fixed deformity (flexion, adduction, or lateral rotation, or a combination of these) is common (see Fig. 17.26).

Radiographic features. The changes are characteristic. There is diminution of the cartilage space, with a tendency to sclerosis of the subchondral bone and cyst formation (Figs 17.25 and 17.26). Hypertrophic spurring of bone (osteophyte formation) is usually seen at the joint margins.

Fig. 17.25 Radiograph of idiopathic osteoarthritis of the hip. There is narrowing of the joint space, a subchondral cyst is seen in the medial femoral head, and large osteophytes are evident at the lateral margin of the acetabulum and on the lateral side of the femoral head.

Fig. 17.26 Advanced osteoarthritis of right hip. Note the adduction deformity – a common feature that causes apparent shortening of the limb from tilting of the pelvis. As in Figure 17.25, the characteristic features are narrowing of the joint space, subchondral bone sclerosis, and marginal osteophytes.

Treatment. The treatment required depends upon the severity of the disability. Mild osteoarthritis is best left untreated. In cases of moderate severity conservative treatment may suffice, but in severe cases operation is often advisable.

Conservative treatment. Clearly no form of conservative treatment can possibly influence the distorted anatomy of the joint. At best such treatment is only palliative; it may alleviate but cannot abolish the pain. Four methods will be mentioned:

Operative treatment. Operation may be required if pain is severe – especially if it hinders sleep and interferes seriously with the patient’s capacity for walking or work. Three types of operation must be considered:

Fig. 17.28 A Displacement osteotomy of the femur (McMurray). The femur is divided between the greater and the lesser trochanters, and the shaft fragment is displaced medially through a distance equal to about a quarter of its diameter. The fragments have been fixed with a nail-plate. B Excision arthroplasty (Girdlestone pseudarthrosis). Head and neck of femur removed; muscle interposed.

though the last two are now seldom used.

Arthroplasty. The method most commonly used in primary management is total replacement arthroplasty (Figs 17.27A and 17.29A). Excision arthroplasty (Fig. 17.28B) is now only used as a salvage operation after other methods of treatment have failed, particularly when replacement arthroplasty has failed on account of infection.

Fig. 17.29 A Total replacement arthroplasty of hip. The hemispherical socket, of polyethylene, is not seen, but its mouth is indicated by the wire marker. B AP radiograph of hip in patient 10 years after total hip replacement. There is a dark lucent line (arrowed) between the cemented cup and the bone of the acetabulum. The femoral shaft also shows endosteal bone resorption around the proximal and mid portion of the stem. This is indicative of loosening of both prostheses.

In total replacement arthroplasty both the femoral and acetabular articular surfaces are replaced by artificial materials. The introduction of this technique in the 1960s resulted from two important innovations: the development of new metal and polymer biomaterials which could provide low friction articulations while remaining inert in the body, and the use of an acrylic filling compound, or polymethylmethacrylate cement, to fix the implants to the bone. One of the earliest, and still most successful designs was that of Charnley, which replaced the femoral head with a much smaller stainless steel head on a stem fixed into the femoral shaft with acrylic cement. This articulated with a thick hemispherical socket or cup of high-density polyethylene, which was also fixed to the bone of the deepened acetabulum with acrylic cement (Fig. 17.29A). This, and similar prostheses, provided restoration of pain-free hip movement and function, which could be expected to continue for more than 10–15 years in over 90% of patients. Replacement arthroplasty is now accepted as one of the most successful operations in terms of restoring the quality of life in patients for most years. However, like all surgical procedures it has risks and complications. In the early years of its use the most feared of these was postoperative infection, either early or late. The rate of this complication has now been reduced to around 1% by the use of routine prophylactic antibiotics combined with sterile operating environments utilising clean air laminar flow ventilation. A more challenging long-term problem is the progressive aseptic loosening of the prosthetic components which may occur (Fig. 17.29B) in some patients and results in a cumulative failure rate of 1% each year. This is associated with bone destruction around the implants which was thought to result from a granulomatous tissue reaction to the wear particles liberated from the weight-bearing surfaces.

In the intervening years, there have been many attempts to improve on this basic design to provide longer implant survival, particularly when the technique is used in younger patients. These have included attempts at ‘cementless’ mechanical fixation of implants using prostheses with porous metal surfaces to encourage bone ingrowth, and the development of new biomaterials such as ceramics or better polyethylenes with improved wear characteristics.

Another concept that has been reintroduced is the resurfacing or ‘double cup’ arthroplasty (Figs 17.27B and 17.30). This uses matching shells to resurface the femoral head and reline the reamed acetabular socket. Earlier attempts with this technique in the 1970s, using conventional metal and polyethylene components, had resulted in early failure because of rapid wear of the thin acetabular component. This problem has now been overcome by the use of improved metal-on-metal shells. The operation is only indicated in younger more active patients under the age of 60 where preservation of bone stock is required for potential later revision. Short-term results are now as good as with conventional replacement arthroplasty, but the operation, which is more technically demanding, should only be used for selected patients by those skilled in its use until results from longer follow-up become available.

Fig. 17.30 Metal-on-metal ‘double cup’ hip resurfacing prosthesis.

Upper femoral osteotomy (McMurray displacement osteotomy). This operation was a standard method of treatment before total replacement arthroplasty was developed, but it is now little used. It may still be useful in patients under 55 with moderately early osteoarthritis where pain is a major problem but there is still an adequate range of functional movement, including 90 ° of flexion. The femur is divided between the greater trochanter and the lesser trochanter, and the lower (shaft) fragment is displaced medially through about a quarter of its diameter (Fig. 17.28A). Internal fixation of the fragments by nail-plate and screws is usually employed. Relief of pain is often satisfactory in over 70% of patients and preoperative joint movement is retained. The question of why an upper femoral osteotomy should relieve the pain of an osteoarthritic hip has not been answered satisfactorily. It is possible that in some way the remodelling of bone trabeculae necessitated by the displacement stimulates repair processes in the damaged articular cartilage; or it may alter the vascularity of the femoral head. Certainly in a favourable case the cartilage thickens appreciably in the first two or three years after operation, as shown radiologically. The other advantage of the operation is that it can still be converted to a hip replacement arthroplasty later, should the result prove disappointing in the long term.

Arthrodesis. The joint is fused in a position of 15–20 ° of flexion but without any abduction, adduction, or rotation. There is complete relief of pain, and good function is possible so long as the other hip, the knees and the spine are normal. It is only applicable in younger patients under 40 with distorted hip anatomy and is inappropriate for patients in countries where squatting is the normal habit.

In excision arthroplasty (Girdlestone pseudarthrosis) a false joint is created by excising the head and neck of the femur and the upper half of the wall of the acetabulum, and suturing a mass of soft tissue (such as the gluteus medius muscle) in the gap thus created, to act as a cushion between the bones (Fig. 17.28B). This is essentially a salvage operation, originally designed for chronic infections, and should only be used when alternatives have failed or are inappropriate.

It usually provides pain relief, but at the expense of substantial shortening and instability, necessitating the permanent use of a stick for walking and a considerable shoe raise.

PERTHES’¹ DISEASE (Legg–Perthes’ disease; coxa plana; pseudocoxalgia; osteochondritis of the femoral capital epiphysis)

Perthes’ disease is osteochondritis of the epiphysis of the femoral head. The general features of osteochondritis were described in Chapter 8(p. 130). Like most examples of osteochondritis, Perthes’ disease is an affection of childhood. The femoral head is temporarily softened and may become deformed. The main importance of the condition is that it may lead to the development of osteoarthritis of the hip in later life.

Cause. A temporary, and possibly repeated, local disturbance of blood supply is believed to be the major factor, but the precise cause of the vascular disturbance is unknown.

Pathology. The bony nucleus of the epiphysis of the femoral head undergoes necrosis either in whole or in part, presumably from ischaemia. This sets up a sequence of changes which occupies two to three years. The first stage is that of ingrowth of new blood vessels and removal of dead bone by osteoclasts. In the second stage, which is not distinct but overlaps the first stage so that both processes are going on together, new bone is laid down on the dead trabeculae, gradually reconstituting the bony nucleus. The third stage is that of remodelling: this may continue for several years. This sequence of necrosis and replacement of bone is patchy rather than uniform, so that the nucleus has an appearance of fragmentation as seen in the radiographs. During this period structural rigidity is lost, and deformation of the epiphysis may occur from pressure across the joint.

In the early phases of the cycle of changes growth of the bony element of the epiphysis is temporarily arrested, but the cartilage surrounding the bony nucleus, which forms a considerable proportion of the femoral head, continues to grow and so is disproportionately thick (Fig. 17.31), though sometimes revascularisation and healing will restore a relatively normal femoral head Fig. 17.32). Nevertheless it may sometimes follow the bone in suffering deformation, so that the femoral head as a whole may become much flattened (Fig. 17.33). At the same time there is often some enlargement of the femoral head. As the acetabulum grows, it tends to follow the contours of the femoral head, so that it may end up abnormally large and shallow (Fig. 17.34).

Fig. 17.31 Perthes’ disease of the left hip. Note the shrunken appearance of the bony nucleus of the femoral epiphysis, the corresponding increase in depth of the cartilage space, the patchy changes of density, and the suggestion of fragmentation.

Fig. 17.33 In this patient, despite prolonged relief from weight-bearing, the femoral head is markedly flattened and the femoral neck is short. The deformity of the femoral head predisposes to osteoarthritis in later life.

Fig. 17.34 Old untreated Perthes’ disease. The femoral head is markedly flattened and the femoral neck is short. There is already some narrowing of the cartilage space, suggesting early osteoarthritis.

In consequence of interrupted growth at the epiphysial plate the femoral neck – and the limb as a whole – may be shorter than on the normal side, though the discrepancy is not great.

Clinical features. The disease occurs mainly in children of 5 to 10 years. It usually affects only one hip. The child complains of pain in the groin or thigh, and is noticed to limp. There is no disturbance of general health. On examination the only striking sign is moderate limitation of all hip movements, with pain and spasm if movement is forced.

Imaging. Radiographic features. The earliest radiographic changes are usually, though not always, present by the time advice is sought. There is a slight decrease in the depth of the ossific nucleus of the femoral head, whereas the clear cartilage space is often increased in depth: in other words the bony nucleus seems to have shrunk within its surrounding bed of cartilage (Fig. 17.31). The nucleus becomes denser than that of the normal side, though the density is patchy rather than uniform, so that there is an appearance of fragmentation. In severe cases the nucleus becomes progressively more flattened. Eventually the texture of the bone returns to normal (Fig. 17.32), but if flattening has occurred the femoral head is permanently deformed (Figs 17.33 and 17.34). Radioisotope scanning shows failure of uptake of the isotope in the region corresponding to the bony nucleus of the femoral head, but the changes are better demonstrated even at a very early stage by MRI scanning.

Fig. 17.32 Same patient as in Figure 17.31 two years after the onset of symptoms. The shape of the head is virtually normal, and the femoral neck is of normal length. There is little risk of osteoarthritis.

Diagnosis. Perthes’ disease is distinguished from tuberculous arthritis, which it may resemble clinically, mainly by the radiographs. A normal erythrocyte sedimentation rate and blood count, and good general health, are other distinguishing features.

Prognosis. The disease has no direct adverse effect upon the general health. The main risk is to the future function of the affected hip joint, because if the femoral head suffers permanent deformation there is a risk of secondary osteoarthritis in later life, often in the fifth or sixth decade (Fig. 17.34).

The outcome depends largely upon whether the whole of the epiphysis is affected or whether part of it escapes, as it often does. In the latter case the prognosis is favourable (Fig. 17.32), whereas if the whole epiphysis is affected marked flattening of the femoral head may occur despite the most careful treatment (Fig. 17.33). The state of the cartilaginous part of the head, as determined from arthrography or from comparison of MRI scanning of both hips, is also important in prognosis. If head height is well preserved, the outlook is favourable, whereas if there has been early collapse of cartilage permanent deformation of the head is to be expected. In general, the outlook is more favourable in younger children than in older children.

Treatment. It has to be admitted that the treatment of Perthes’ disease is often disappointing: no universally satisfactory method has yet been evolved. Indeed it has sometimes been questioned whether treatment has any effect on the final state of the hip.

The former method of preventing weight-bearing pressure upon the softened femoral head by prolonged recumbency (often for 2 years or more) has long been abandoned because the results were not commensurate with the severe disruption of home life that this treatment entailed. Other methods of trying to prevent pressure upon the head while still allowing the child to be up and about, such as slings or ischial-bearing calipers, have also fallen into disfavour because they are seldom effective and because they may embarrass the child psychologically.

The present trend is to grade the cases according to the likely outcome, so far as the shape of the femoral head is concerned, as judged from the radiographic features in the early stages and to regulate the treatment accordingly. In the ‘favourable’ category are placed those with only half the head affected (as seen in the lateral radiographs) and with no sign of lateral extrusion of part of the femoral head from under the roof of the acetabulum. In the ‘unfavourable’ grade are placed those with the whole head affected or with some lateral extrusion of the head beyond the roof of the acetabulum. In general, patients with a favourable prognosis do not require treatment other than by rest for a few weeks to allow the pain to subside – though it is essential that they attend periodically for radiological review. In contrast, those with an unfavourable prognosis, with the femoral head in danger of becoming badly deformed, are advised to have surgical treatment to prevent this.

Present thought is that treatment, when needed, should be by ‘containment’ of the femoral head within the acetabulum. This means that the femoral head must be centred within the acetabulum so that the two are co-axial, and thus the whole circumference of the femoral head is embraced by the socket. The socket then acts as a mould, to keep the head hemispherical while it is in the softened state.

In practice, ensuring maximal containment of the femoral head demands that the femoral head and neck (or the whole limb) must be abducted in relation to the acetabulum, to make them co-axial. This has sometimes been achieved by splinting the limbs in 20 ° or 30 ° of abduction, but the child is thus greatly handicapped in walking. Most surgeons therefore prefer to realign the femoral head and neck by dividing the femur below the greater trochanter and deflecting the neck downwards to coincide with the central axis of the acetabulum (see Fig. 17.20). Alternatively, the acetabulum itself may be redirected after osteotomy of the innominate bone (see Fig. 17.17D, p. 351).

OSTEONECROSIS (Non-traumatic avascular necrosis) OF THE FEMORAL HEAD

Necrosis of the bone of the femoral head may be a complication of trauma, particularly fracture of the femoral neck, but may also occur without a history of injury. This non-traumatic or idiopathic osteonecrosis is thought to be the result of an ischaemic episode affecting the bone and marrow tissue, and may cause progressive collapse of the femoral head in young adults.

Cause. The aetiology of this uncommon condition is still unclear, though several factors have been proposed as the mechanism of ischaemia, including intra-osseous hypertension, fat embolism, and intravascular coagulation. There is often a history of steroid therapy or alcohol addiction, and the condition may also develop in patients receiving immuno-suppression therapy following organ transplantation. It may also be associated with inherited haemoglobinopathies, such as sickle cell disease; and it may occur as a complication of Gaucher’s disease (p. 72).

Pathology. The bone necrosis does not involve the entire femoral head, but commonly occupies a wedge-shaped segment beneath the superior weight-bearing surface. This may result in a subchondral fracture with subsequent collapse of the articular surface and a progression to secondary osteoarthritis. Surrounding the segment of bone necrosis there is a dense margin showing histological changes of an inflammatory response, with vascular granulation tissue suggesting a repair mechanism.

Clinical features. The patient, usually young or middle-aged, will present with increasing pain, which is frequently bilateral, in the hip or thigh during standing or walking. There is often a history of steroid therapy, excessive alcohol intake, or one of the other medical risk factors. Initially the range of hip movement is maintained, though painful at its extremes. Later, when bony collapse has occurred, there may be marked restriction of hip movement, with secondary contractures and limb shortening.

Investigation. In the early stage of the disease plain radiography may be normal (Fig. 17.35A), though magnetic resonance imaging (MRI) may show a low-intensity focus in the affected femoral head (Fig. 17.35B). Bone scintigraphy using a technetium-labelled isotope may reveal an area of increased or decreased uptake in the femoral head at the site of developing necrosis, but is less sensitive than an MRI scan.

Fig. 17.35 A Radiograph of pelvis showing flattening of the femoral head with sclerosis in the right hip indicative of avascular necrosis. Compare with normal appearance on the left. B Coronal T1 weighted MR scan of the pelvis showing a dense segment in the superior part of the right femoral head. This abnormal appearance is indicative of avascular necrosis, which the MR scan will detect long before there are changes seen on plain radiographs.

A full haematological and biochemical screen should be undertaken to identify any associated disease.

Radiographic features. One of the earliest radiographic signs of developing osteonecrosis may be narrowing of the joint space, with flattening of the weight-bearing surface of the head and an underlying area of sclerosis in the bone. Progression to subchondral fracture results in a crescent sign of lucency beneath the superior articular surface with a dense segment in the underlying femoral head (Fig. 17.36). In the advanced stages of the disease there may be secondary arthritic changes, with progressive collapse of the femoral head.

Fig. 17.36 Radiograph of hip showing late avascular necrosis of the femoral head with evidence of collapse of the articular surface and an underlying crescent of sclerotic bone.

Treatment. Treatment is usually surgical and is determined by the stage and extent of the disease. If diagnosed early, prior to femoral head collapse, an attempt can be made to encourage revascularisation by drilling the affected segment through a trans-trochanteric approach, with the possible addition of bone grafting to provide both an osteogenic stimulus and mechanical support. In more advanced disease, where some bony collapse has occurred, an osteotomy of the femoral neck may allow better containment of the femoral head and restoration of an intact articular weight-bearing surface. Once secondary osteoarthritis is established, removal of the femoral head and total replacement arthroplasty of the hip is the only surgical option.

SLIPPED UPPER FEMORAL EPIPHYSIS (Adolescent coxa vara; epiphysial coxa vara)

This is an affection of late childhood in which the upper femoral epiphysis is displaced from its normal position upon the femoral neck. The displacement occurs at the growth plate (epiphysial line), and it is common for it to occur on both sides (though seldom simultaneously).

Cause. This is unknown. The condition is often associated with overweight from endocrine dysfunction or from other causes, but in other cases the patient is of normal build.

Pathology. The junction between the capital epiphysis and the neck of the femur loosens. With the downward pressure of weight-bearing and the upward pull of muscles on the femur the epiphysis is displaced from its normal position. Displacement is always backwards and downwards, so that the epiphysis comes to lie at the back of the femoral neck (Fig. 17.37).

Fig. 17.37 Upper end of child’s femur seen from the side. A Normal position of epiphysis. B Slipped epiphysis. The displacement is always backwards and downwards.

The displacement usually occurs gradually, but occasionally a sudden displacement is caused by injury, such as a fall. Left undisturbed, the epiphysis fuses to the femoral neck in the abnormal position. The consequent deformity of the articular surface then predisposes to the later development of secondary osteoarthritis.

Clinical features. The patient is between 10 and 20 years of age. In about half the cases there is evidence of an endocrine disturbance leading to marked overweight. In a little less than half the cases both hips are affected, though seldom simultaneously. Typically, there is a gradual onset of pain in the hip, with limp. Sometimes the pain is felt mainly in the knee, which may confuse the diagnosis. Rarely, these symptoms develop acutely after an injury, such as a fall.

On examination the physical signs are characteristic, for there is selective limitation of certain hip movements, the other movements being full or even increased. The movements that are restricted are flexion, abduction, and medial rotation. Lateral rotation and adduction are often increased, and the limb tends to lie in lateral rotation. Forcing movement in the restricted range exacerbates the pain.

Radiographic examination. Even a slight displacement of the epiphysis is recognisable, provided good lateral radiographs are obtained. It must be stressed that a slight displacement is easily overlooked if antero-posterior films alone are examined (Fig. 17.38). Lateral radiographs are essential. In the lateral film the epiphysis is seen to be tilted over towards the back of the femoral neck (Fig. 17.39),¹ the posterior ‘horn’ being lower than the anterior, whereas in the normal hip they are level.

Fig. 17.38 AP radiograph of the pelvis in a child with an early slipped femoral epiphysis of the left hip. The epiphysis has slipped medially and backwards. This subtle abnormality is identified by drawing a line along the superior margin of the femoral neck. On the normal right side a small portion of the epiphysis is seen to extend above the line. On the abnormal left side, when the line is drawn there is no part of the epiphysis lying above it.

Fig. 17.39 A Lateral radiograph of the left hip in the same child confirms that the epiphysis has slipped backwards on the femoral neck. B Another patient. Slipped epiphysis of severe degree.

Diagnosis. Slipped upper femoral epiphysis should be suspected in every patient of 10–20 years of age who complains of pain in the hip or knee. The characteristic clinical features, together with the radiographic evidence of epiphysial displacement, are conclusive. The condition is nevertheless often missed, partly because pain may be predominantly in the knee, the hip therefore being not examined; or because lateral radiographs are not obtained (Fig. 17.38).

Complications. These include avascular necrosis of the epiphysis of the femoral head, cartilage necrosis, and late osteoarthritis.

Avascular necrosis (osteonecrosis) and consequent collapse of the epiphysis may occur if its blood supply is damaged. This complication is usually a consequence of attempted reduction of the slip by manipulation or of operation, but it may occur spontaneously, especially after a sudden acute slip.

Cartilage necrosis is a rare and unexplained thinning of the articular cartilage, with marked restriction of joint movement. It is commonest after operative treatment and may possibly represent an auto-immune reaction.

If severe displacement is allowed to remain uncorrected osteoarthritis is likely to develop in later life (Fig. 17.40).

Fig. 17.40 Osteoarthritis developing twenty years after uncorrected slipped epiphysis.

It is necessary to emphasise that a careful watch must always be kept for slipping of the opposite femoral epiphysis, which may occur in up to 50% of patients and may justify prophylactic fixation in those thought to be at greater risk.

Treatment. The treatment depends upon the degree of displacement. This may be graded as slight or severe.

Slight displacement. When displacement is slight (less than 40 ° as measured on the lateral radiograph) (Fig. 17.39A) the position may be accepted and all that is necessary is to prevent further displacement. This is achieved by driving threaded wires or slender screws¹ along the neck of the femur into the epiphysis (Fig. 17.41). It should be remembered that even though the position that has been accepted may be imperfect, improvement can occur spontaneously in the succeeding years, through a process of remodelling.

Fig. 17.41 Slipped epiphysis with only slight displacement. Threaded wires have been inserted to prevent further slipping.

Severe displacement. When displacement is severe (Fig. 17.39B) the position cannot easily be accepted because of the virtual certainty that painful osteoarthritis will develop in adult life. The position should therefore be improved. Three methods are available: manipulation, operative replacement of the epiphysis at the site of slipping, and compensatory osteotomy at a lower level.

Manipulation, with or without preliminary weight traction, is seldom successful; it is worth trying only in the rare cases of recent sudden displacement, especially if caused by injury. Manipulation – predominantly by medial rotation – should be carried out very gently lest the blood supply to the epiphysis be further damaged. After successful manipulative reduction further slipping should be prevented by inserting threaded wires or screws, as described above.

Operative replacement of the epiphysis, with fixation by wires or a screw, has sometimes been practised when symptoms have been present for less than 3 months, provided the growth plate is still open. At its best it can restore the hip virtually to normal. Nevertheless the operation has the serious hazard that it may destroy the blood supply to the femoral head, leading to avascular necrosis (osteonecrosis) of the femoral head and precipitating the onset of disabling osteoarthritis. In the opinion of many surgeons this major hazard negates any indication for the operation.

Compensatory osteotomy is an alternative method that is preferred by most surgeons. The osteotomy is done just below the trochanteric level (Fig. 17.42). An anteriorly based wedge of bone is removed so that the shaft of the femur is angled into flexion relative to the upper fragment. The operation thus compensates for the backward tilting of the epiphysis; correction should be sufficient to bring the epiphysis once more into the weight-transmitting segment of the acetabulum. The operation entails no risk of damage to the blood supply of the femoral head, so there is no risk of disastrous avascular necrosis (osteonecrosis); but it leaves the articular surface of the upper end of the femur deformed, and therefore does not altogether remove the risk of secondary osteoarthritis in later years.

Fig. 17.42 Subtrochanteric osteotomy for slipped femoral epiphysis of severe degree. By removal of an appropriate wedge of bone (shown outlined in the left-hand diagram), the epiphysis is restored to its proper relationship with the acetabulum. The operation has the advantage that the blood supply of the epiphysis is not endangered.

EXTRA-ARTICULAR DISORDERS IN THE REGION OF THE HIP

COXA VARA

The general term coxa vara includes any condition in which the neck–shaft angle of the femur is less than the normal of about 125 ° (Fig. 17.43). The angle is sometimes reduced to 90 ° or less. The deformity is caused mechanically by the stress of body weight acting upon a femur that is defective or abnormally soft.

Fig. 17.43 A Normal neck–shaft angle. B Coxa vara: the neck–shaft angle is reduced.

Causes. The most important causes of coxa vara are:

1 Congenital. Part of the femoral neck remains as unossified cartilage, which gradually bends during childhood (congenital coxa vara; infantile coxa vara). This type is uncommon.

2 Slipped upper femoral epiphysis (epiphysial coxa vara). This was described on page 371.

3 Fracture. Coxa vara is common after fractures in the trochanteric region with mal-union, and in ununited fractures of the neck of the femur.

4 Softening of bone, in general affections such as rickets, osteomalacia, or Paget’s disease.

Effects. Coxa vara leads to true shortening of the limb. Approximation of the greater trochanter to the ilium slackens the abductor muscles of the hip and thus impairs their efficiency, leading in severe cases to a Trendelenburg ‘dip’, with consequent limp (p. 341).

Treatment. The treatment is mainly that of the underlying condition. Often a mild deformity is best accepted. In appropriate cases the neck–shaft angle can be corrected by osteotomy just below the greater trochanter.

EXTRINSIC DISORDERS SIMULATING DISEASE OF THE HIP

As has already been mentioned, it frequently happens that a patient complains of symptoms in the region of the hip or thigh when in fact they arise at a distance. The conditions that may confuse the diagnosis in this way fall into three main groups: