Osteochondritis

This loosely defined term embraces three pathological processes involving epiphyses of larger bones or even the whole of a small bone, e.g. in the carpus or tarsus.

The processes are avascular necrosis affecting epiphyses normally under compression, chronic strain injuries to traction epiphyses and osteochondritis dissecans, which is a stress fracture through articular cartilage with or without involve­ment of subchondral bone. The individual conditions are usually referred to anonymously (Table 28.1).

Avascular necrosis (AVN)

The causes of osteochondritis presenting as AVN are obscure and theories include interruption of arterial supply through trauma, coagulopathy, venous hypertension or disorders of epiphyseal cartilage.

  Legg—Calve—Perthes (LCP) disease

This is a mysterious and poorly understood condition. The capital femoral epiphysis undergoes an early stage of infarction, progressing to collapse and fragmentation, followed by healing (Figs 28.1 28.2, 28.3, and 28.4). The whole process takes several years (Fig. 28.2) and involves part or all of the epiphysis.

Various classifications of the radiological changes have been used, e.g. Catterall, Salter—Thompson, Herring. Unfortunately, they are prone to interobservor error and it is difficult from a single set of X-rays to be sure of the stage or extent of the disease. Moreover, radiological classifications do not reliably relate to the age of the child or the clinical features. For example, a child, especially if young, with whole head involvement may have good movements and very little disability. The condition is relatively benign in the majority of children and does not lead to severe disability or arthritis in adult life. All of these uncertainties make it difficult to select those children who might benefit from treatment in both the short and long term.

Clinical features. The condition can occur between the ages of 3 and 12. It is more common in boys and more frequent in children of low birth weight or those who had a constitutional delay in growth. There is a family history in 12 per cent of cases and the condition may be bilateral in 20 per cent. Synchronous involvement is rare and when seen the diagnosis of multiple epiphyseal dysplasia should be considered.

The usual presentation is pain and a limp. These can be mild and intermittent so the onset may be difficult to define. The pain is usually in the hip region but, like slipped upper femoral epiphysis (SUFE), can be referred to thigh or knee. Therefore children with knee pain should always have their hips examined and X-rayed if there is any suspicion of disease therein.

In LCP disease, flexion is usually maintained but the hips lose abduction and internal rotation. The thigh is usually thinner than the normal side and the Trendelenburg test frequently positive. In spite of these clinical features the children usually remain active and regularly have to be restrained.

The diagnosis is confirmed by radiographs. Magnetic resonance imaging (MRI) or bone scans may be helpful in the very early stages.

Treatment. The goal is to achieve a congruous joint. The majority of cases will not regain their previous normal shape (spherical congruity) but heal as an oval head (aspherical congruity). However, providing the head matches the socket, the hip is likely to do well in the long term. Where there is a mismatch (aspherical incongruity) the hip does badly.

It is generally agreed that hips should be exercised and kept as mobile as possible, thereby aiming to prevent adduction or flexion deformity and encourage remodelling to a congruous joint. If adduction deformity develops, a period in abduction splintage should be considered.

The role of open surgery, e.g. femoral or innominate osteotomy, is controversial, especially in the younger child. It is difficult to prove that surgery will be beneficial in the long term. In the short term, operations designed to achieve containment of the femoral head may cause damage to the growth plate, usually make a limp worse and may cause incongruity and stiffness. Therefore, if a surgeon cannot feel sure of achieving a congruous joint (an arthrogram may help in the assessment) a better alternative to osteotomy is a shelf-type procedure to augment the acetabulum and thereby give better cover to the femoral head.

In summary, LCP disease is generally benign with a good long-term prognosis. The hip should be kept mobile to avoid deformity and encourage congruous healing. Children who are younger and with partial head involvement do better and the role of operations remains controversial. We still do not know how to select accurately those children who will benefit from surgery in the long term.

Freiberg’s disease

This affects the distal epiphysis of the second metatarsal and is generally very troublesome. If simple treatment, such as insoles, fails it may be necessary to consider osteotomy or even excision of the metatarsal head.

Kohler's disease

This benign condition affects the tarsal navicular. This normally does not ossify until the fourth year of life and thereby confusion may occur. Kohler’s disease presents with pain which is usually not bad enough to warrant more than symptomatic treatment. Radiographs show a flattened navicular (Fig. 28.5) and a comparison view of the other foot is indicated to ensure that one is not dealing with a normal ossification pattern. The children can be advised on activity within the limits of their symptoms and the navicular usually remodels to normality.

Keinbock disease

This affects the carpal lunate and causes troublesome pain and stiffness. It usually affects older teenagers and young adults. The lunate flattens and fragments thereby disturbing the proximal row of the carpus. It is a difficult condition to treat with no reliable surgical option. Various procedures include replacement of the lunate, shortening of the ulna, proximal row carpectomy or even arthrodesis of the wrist.

Panner’s disease

The capitellum becomes flattened and the elbow stiffens. There is no satisfactory operation for the condition but fortunately good elbow function is usually maintained.

Traction or strain injuries

These can occur wherever powerful muscles are attached to bone. In children ligaments and tendons are generally stronger than bone and acute or chronic traction injuries manifest by signs of avulsion. Examples of acute traction injuries include rectus femoris at the anterior—inferior iliac spine and hamstrings at the ischial tuberosity.

The classical chronic traction injuries are recognised eponymously. They are:

Osgood—Schlatter’s disease (tibial tubercle; Fig. 28.6);

Sinding Larsen disease (distal pole of patella);

Sever’s disease (posterior epiphysis of os calcis).

The treatment of all these injuries is rest. Unfortunately many of the affected children are keen athletes and the lesions are the effects of excessive demands on an immature   skeleton. It is often unrealistic to impose a total ban on sport; a more practical approach is to advise activity within the limits of the symptoms with the likelihood that the conditions will settle as the skeleton matures.

Osteochondritis dissecans

In this condition, a piece of articular cartilage, with or without the underlying subchondral bone, becomes unstable and may detach into the joint, thereby forming a loose body. The mechanism is acute or chronic trauma.

Common sites include the medial femoral condyle, talus and capitellum. Loose bodies cause pain and locking whereas an unstable fragment may cause discomfort when the joint is stressed.

The lesions may be present on plain X-rays but can also be well demonstrated by MRI.

In general an expectant approach is adopted, unless a troublesome loose body needs removal.