A slipped capital femoral epiphysis (SCFE) is a condition in which the head of the femur separates from the adjacent growth plate or epiphysis at the upper end of the femur.

It is found to occur over time and invariably in children and adolescents, most often between the ages of 12 and 14 years in boys, and 10-14 years in girls. This is the time period before skeletal maturity is achieved. The direction of slippage is usually backward.

As a result the joint becomes painful, stiff, and often unstable. It is a slowly developing condition in most patients, and occurs more often in boys than in girls. On occasion it may be due to a traumatic separation of the epiphysis. One or both hips may be affected.

Children younger than about 10 years are more likely to develop SCFE on the opposite side to that first involved, and the prevalence in this group is about 40%. The second side is affected within 18 months of the first in a majority of these patients. The overall incidence of this condition is about 2 in 100,000.

Types

The type of SCFE determines the best treatment option. The Loder classification divides it into stable and unstable variants based on whether the patient can bear weight on the hip with SCFE  or not.

Stable SCFE is a condition in which the capital epiphysis has separated and is displaced but the affected individual is still able to put a load on the involved hip, either with or without crutches. This accounts for most cases of SCFE. The risk of avascular necrosis of the damaged hip is about 10%.

Unstable SCFE occurs when no weight can be put on the affected hip even with crutches, and therefore requires urgent treatment. This type is linked to a greater incidence of complications, with avascular necrosis occurring in almost half of affected hips.

Causes

The following risk factors and associations have been observed:

1. Male gender: Boys are usually affected rather than girls
2. Obesity: Obese children are more likely to have this condition
3. Rapid growth: SCFE is usually found to occur in those children who have started their growth spurt
4. Metabolic imbalances: Children with hormonal disorders secondary to other medical conditions are more likely to have SCFE

Clinical Features

Early diagnosis is a must to prevent serious or disabling complications of SCFE such as osteoarthritis of the hip. The symptoms of stable SCFE include:

1. limping gait after engaging in moderate to intense physical activity
2. pain in the groin, thigh, knee and hip which occurs from time to time over weeks or months, and becomes worse with activity
3. stiffness around the hip with muscle guarding and spastic muscles around the hip
4. restricted range of movement at the hip

The symptoms of unstable SCFE include:

1. pain in the hip, thigh, or groin of acute onset, occurring after an injury
2. great difficulty in walking or putting weight on the affected hip
3. external rotation of the leg on the affected side
4. the involved leg appears shorter than the normal limb
5. the hip is restricted in its range of motion.

Diagnosis and Treatment

A complete history, a physical examination and imaging tests such as an X-ray of the hip joint usually are sufficient to diagnose the condition.

Mild stable SCFE is usually treated with surgery to arrest the separation of the capital epiphysis. The correction is done through a small hip incision, and aims to re-position the slipped epiphysis where it ought to be, using screws and pins through the growth plate to keep it there until skeletal growth is complete. Often both hips are treated at the same time because the asymptomatic hip is likely to develop the same problem later.

Unstable SCFE is treated through an open incision at the hip through which the displaced femoral head is put back into place and the femur neck is manipulated into the right relationship with the capital epiphysis. This is then held in place using screws through the growth plate. This is a more extensive surgery and recovery may take longer. The modified Dunn procedure is the treatment of choice in acute unstable SCFE but its greater utility compared to older procedures is still under review with respect to chronic stable SCFE.

The outcome of early detection and treatment is usually good. However, complications may occur, as with any procedure. These include progressive osteoarthritis of the hip. Osteonecrosis and chondrolysis around the hip joint are other rare but possible complications and are more common after unstable SCFE.