Perthes' disease (osteochondritis)

Like congenital dislocation of the hip (CDH) and slipped epiphyses (77.10), Perthes' disease causes only minor symptoms in childhood, but may cause severe osteoarthritis in later life. It is a very controversial disease: nobody knows how to treat it, or how to classify it.

A child with Perthes' disease is between 4 and 9 (occasionally between 2 and 18), and is three times more likely to be a boy. If he presents early. he does so with intermittent episodes of pain in the front of his thigh, knee or groin, and a limp; in the early stages he is normal between these episodes. Sometimes he has no limp, but only some minimal abnormality of his gait, such as a tendency to walk with his leg turned inwards. Usually (but not always) all the movements of his hip are mildly limited, by discomfort rather than by pain, especially abduction and internal rotation. He may also have some fixed flexion. If his movements are limited, he usually also has spasm, particularly in his adductor and psoas muscles. His thigh and buttock may be wasted. He may be vaguely tender around his hip, but he is otherwise perfectly well. If he presents late, after the disease has run its course, his only signs may be a slight loss of the normal range of abduction, extension, and medial rotation of his hip, or he may have no symptoms or signs. In Africa, most patients don't present until they have permanent deformity.

Perthes' disease is an avascular necrosis of all or part of the epiphysis of the head of the femur. Essentially, the disease passes through five stages during 2 to 4 years: (1) To begin with the child's X-rays are normal. (2) All or part of the head of his femur looks abnormally dense on the X-ray, which indicates reduced vascularity. The cartilage surrounding it does not die; instead, it continues to enlarge, and makes the joint space appear larger. (3) The epiphysis may fragment. (4) New blood vessels gradually grow in, and the epiphysis looks less dense. The epiphysis and metaphysis may soften, so that his metaphysis bends and causes a mild coxa vara (the head and the neck of his femur are angled more medially from the shaft). (5) Eventually, the head returns to its normal density, but it remains flatter, and the neck remains wider than normal.

Catterall classifies Perthes' into four groups, which are complex, disputed, and difficult for the inexpert. Hips in Group One and in Group Two (without risk factors) will do well without any treatment. Most Group Four hips do badly, even if they are treated. A child is more likely to to get osteoarthritis later in life, if the head of his femur flattens. The older he is, and the more misshapen the head, the worse his prognosis. But, even if it is seriously flattened, he will probably not get symptoms until he is middle aged. Unlike slipping of the heads of the femoral epiphyses, the involvement of both hips is unusual in Perthes' disease (15% of cases, mostly in younger children).

The hope of treatment is to prevent deformity, as long as the epiphysis and underlying metaphysis are soft, which is during the avascular phase and during revascularization. There are various possibilities, either alone or combined: (1) Prolonged traction (1[nd]2 years) produces little benefit, and is quite impractical. (2) Any attempt to avoid weight-bearing by restricting a child's activity is also impractical in the developing world. (3) Some contributors consider that weight- bearing calipers don't work and should be avoided. (4) Salter's Toronto splint is expensive and impractical. (5) Surgery has never been proved to be better than non-operative management. What are you to do? We give you two very different regimes. The second is the more practical one.

THE AIM OF MANAGEMENT IS TO PREVENT LATE OSTEOARTHRITIS Fig. 27-16 PERTHES' DISEASE. This shows the progression of an patient in Catterall's Group Four. A, in Perthes' disease there is always limitation of abduction. B, and C, on the abnormal side the head of the femur is smaller and denser, and the joint space looks increased. E, patchy fragmentation follows. G, the head becomes wide and flattened. Meanwhile, the opposite hip, (B, D, and F) has been growing normally. After Apley AG, ''System of Orthopaedics and Fractures', Fig. 26-12 18.20, with kind permission.

PERTHES' DISEASE TESTING FOR SPASM SPASM IN EXTENSION. Lay the child on his back, place your hands on his affected thigh, and roll it backwards and forwards, as in Fig 7-17. Compare both sides. If there is no spasm in extension, test it in flexion.

SPASM IN FLEXION. Flex his hip and knee to 90[de]. Rotate his leg inwards and outwards. Rotation is usually more limited than abduction or adduction.

ABDUCTION IN FLEXION is usually limited (A, 27-16).

X-RAYS. Take an AP and a lateral view. Abduct his hips, rotate his femurs inwards, and take an AP view to include both hips, so that you can compare them.

GROUPING (Catterall, modified) determines prognosis and treatment. Group him when he presents.

Group One. There is an increase in radiodensity in the head of his femur, but no loss of height and no sequestration. An AP view may show lytic areas in the epiphysis. The metaphysis is normal.

Group Two. In a lateral view the area of sequestration and fragmentation is less than two-thirds of the width of the epiphysis. Loss of height is mild. There is radiolucency in the metaphysis under the affected epiphysis.

Group Three. There is markedly increased density, indicating sequestration of most of the epiphysis, but with a margin of normal bone. There is obvious loss of height. Metaphyseal changes are usually generalized.

Group Four. The whole epiphysis is involved and collapses, so that it has almost no height. The epiphysis extrudes and becomes mushroom-shaped. Metaphyseal changes are marked.

Risk factors. (a) Lateral subluxation of the head leaving it partly uncovered. (b) A translucent area in the lateral third of the epiphysis. (c) Specks of calcium lateral to the epiphysis. (d) Severe radiolucency of the metaphysis. A fragmented upper femoral epiphysis which appears to be extruding from the acetabulum is a poor prognostic sign.

DIFFERENTIAL DIAGNOSIS. See Section 27.13 on the child with the painful hip.

FIRST REGIME. The younger he is, and the less of the head that is involved, the better his prognosis. This is also influenced by the stage of the disease and the presence of risk factors, so weigh them up carefully.

Group One cases usually resolve spontaneously without treatment. Let him walk, but not run, or do violent exercise. X-ray him monthly for 3 months, then 3-monthly for a year, then stop unless he progresses to a worse grade.

Group Two without risk factors. Treat him as Group One.

Group Two cases with risk factors and cases from Group Three. He is likely to progress unless he is treated. Treatment will improve his prognosis, but there is still a chance that he will get osteoarthritis later. Keep him in bed in extension traction (78.3) for about a month, until the spasm in his hip joint has gone. 2 kg will probably be enough. Traction is the best way of making sure that a small child stays in bed.

Then, either: (1) Refer him to an orthopaedic surgeon, who may do an operation to contain the head of his femur in the socket of his acetabulum. Or, (2) continue to apply traction in bed for 1[nd]4 years! A long period of rest in bed is unlikely to be practical, so try to give him as much rest as you can. Then start him walking, but not weight bearing. A weight-relieving caliper is best. This is longer than his leg, and prevents his foot from reaching the ground. Place the ring so that his weight is transmitted from his pelvis to the caliper. If both his hips are involved, the only way you can prevent him bearing weight is to keep him in bed, if necessary for months. Review him regularly: one stage can progress to another, although this is unusual.

Group Four. Deformity of the head is inevitable. Untreated, all patients progress to osteoarthritis. If treated as for Group Three 25% have a good outcome.

SECOND REGIME. Admit him for for a short (3[nd]4 weeks) period of bed rest on traction. Make sure that he he has got Perthes' disease and has not been misdiagnosed; avoid supposedy ''weight-relieving' calipers and long periods in bed. In a hard-pressed orthopaedic unit surgery for Perthes' disease has little if any place.