Slipped upper femoral epiphysis

This is a shear failure through the hypertrophic tone of the upper femoral growth plate (physis). The capital epiphysis slips backwards and downwards. SUFF is uncommon. For example, a family doctor in Britain is likely to see only one case in a working lifetime (Table 28.2). Although the con­dition is classically described in a very overweight (Pickwic­kian) child, it can occur in a tall or muscular child. Conversely the physis can be weakened by injury or disease, e.g. renal failure, radiotherapy, hyperthyroidism. Thus no type of body build can be considered safe from SUFF (Fig. 28.7).

Classification

    The condition can be graded according to the degree of slippage as measured in the lateral X-ray. However, such classifications are prone to inconsistencies in measurement owing to differences in. positioning and interobservor error. Moreover, they do not relate easily to treatment. There are better classifications, e.g. those of Dunn or Loder (Table 28.3) which complement each other. The former relates presentation to treatment, while the latter usefully defines slips according to whether the child can walk unaided (stable) or requires crutches (unstable). A stable hip would therefore correspond to an early chronic (Fig. 28.8) and an acute on chronic (Fig. 28.9) or late chronic slip with the growth plate open (Fig. 28.10) would be likely to be unstable.

Clinical features

Boys and girls are more or less equally affected hut girls tend to get the condition earlier, e.g. ages 9—14 as opposed to 11—16. A girl who has reached menarche is virtually immune. Although the classically overweight picture is commonly seen, no body habitus is exempt.

As the severity and speed of slippage varies, so does the classical presentation. An early chronic (stable) slip may be the cause of mild intermittent pain which is ignored or missed, whereas an unstable acute on chronic or late chronic slip may result in catastrophic loss of function in the limb.

The diagnosis of early slips is usually delayed because this relatively rare condition is not suspected or the symptoms are

minor. Pain is classically felt in the groin and thigh but may he referred to the knee. Any child with knee pain should have the hips examined and if necessary X-rayed.

The backward and downward displacement of the epiphysis causes the lower limb to adduct, externally rotate and extend. The hip thereby shows apparent shortening with loss of abduction, internal rotation and flexion.

Investigations

The diagnosis is confirmed on the lateral radiograph hut the features are regularly seen on the anterior—posterior view. A computerised tomography (CT) scan can help in defining whether the growth plate is open (Fig. 28.11). Blood tests are usually un helpful un less there is a suggestion of metabolic or endocrine disorder, e.g. renal failure or hyperthyroidism.

 

Treatment

The child should be placed on protected weight bearing or even bed rest and traction prior to surgery.

The choices for treatment are fixation in situ or realignment, either by reduction of the slip or osteotomy (Table 28.4).

When the growth plate is open one should fix in situ if at all possible (Fig. 28.12) because realignment through the growth plate carries a significant risk of AVN. The treatment of unstable slips is thereby controversial. However, an extreme slip either acute on chronic or late chronic may be impossible to fix in situ and reduction before fixation may have to be considered, notwithstanding the risks involved (Fig. 28.13).

Postoperatively the child should he on protected weight hearing for 6 weeks and followed up until both growth plates are fused. The family should be warned of the risk of slippage on the contralateral side (20 per cent). Any evidence of this through symptoms or X-rays demands fixation of that side as well. Routine prophylactic pinning of the opposite side is normally reserved for those children at special risk, e.g. renal failure, hypothyroidism.

Complications

Avascular necrosis

This is serious and disabling. It may occur as the result of an acute on chronic slip or may he caused in the course of treating an unstable slip (Fig. 28.14).

Part or all of the head may be involved and the condition does not usually manifest itself radiologically until several months after treatment.

  Chondrolysis

This is a poorly understood condition possibly related to autoimmune causes, whereby the hip joint stiffens and narrows. Chondrolysis is not related to the severity of slippage and indeed can occur after prophylactic pinning of the contralateral. hip.

Treatment is to prevent contracture and keep the hip mobile while healing occurs.

Osteoarthritis

Although osteoarthritis is a common effect of SUFE, it is generally a forgiving complication. Hips generally function well in the long term and only a minority will require, for example, a hip replacement.