Femoral epiphysis is a secondary bone-forming center of the femur, separated from the main part of the bone by cartilage during the period of bone immaturity. In adolescents the femoral capital epiphysis may slip, causing pain and loss of range of motion.
Slipping of the upper femoral epiphysis is most often observed in children between 10 and 16 years of age and is more common in boys than girls. The average age of onset is about 2 years earlier in girls than in boys, coinciding with the earlier bone maturation of girls. Rarely does the disorder develop in girls after menarche (first menstrual period). In about one-fourth of the cases both hips are affected.
The prognosis in slipped epiphysis is related to both the promptness of diagnosis and the degree of slipping. If the displacement is treated early, when slipping is minimal or mild, the results are usually very good.
A chronic slip of moderate degree, if pinned in situ, will usually result in a good functional hip, albeit with some limitation of mobility.
Severe slips require much more extensive reconstruction, are more prone to complications, and have a poorer prognosis of future function.
Osteonecrosis is a serious complication of slipped epiphysis that usually results in considerable disability.
Another frequent complication is chondrolysis, or cartilage necrosis (cell death).
The development of osteoarthritis later in life can also be a complication of slipped epiphysis, and is directly related to the severity of the slip.
Slipping of the upper femoral epiphysis occurs predominantly in obese children with underdeveloped sexual characteristics and, less commonly, in tall, thin children. The underlying cause of the epiphyseal slipping is unknown. Perhaps it is a combination of rapid growth, obliquity of the epiphyseal plate, and minor traumas.
The periosteum, an important stabilizer of the epiphysis, becomes thinner in the adolescent and may yield to shear forces associated with increased body weight and a more vertical slope of the growth plate. Endocrine factors may also play a part, but no specific endocrine abnormality has been proved.
In many cases a history of trauma or strain can be elicited, but the traumatic episode is often trivial.
The onset may be one of three types:
The acute slip: Least common, this usually follows severe trauma such as a fall from a height and is not preceded by significant symptoms.
The acute slip superimposed on a chronic slip: This type is characterized by a sudden onset of pain and disability, preceded by days or weeks of knee discomfort and limp.
The chronic slip: This is gradual, with slowly increasing symptoms over a period of weeks or even months. In chronic slipping, there may be no history of trauma and the symptoms are often quite mild, amounting only to aching, fatigue, a feeling of stiffness after standing or walking, and a limp.
Since the pain is frequently referred to the knee, early diagnosis may be missed, while the symptoms are attributed to "growing pains" or muscle strain. The diagnosis should be suspected in any adolescent with a limp accompanied by hip or knee discomfort who shows slight restriction of internal rotation of the hip.
The degree of slipping and the duration of symptoms influence treatment. An acute slip with severe symptoms of less than two to three weeks' duration can usually be reduced by gradual traction. Very gentle manipulation under anesthetic has been successful in these early cases, but gradual reduction by traction is less likely to disturb the circulation of the femoral head.
When reduction of the acute slip has been obtained, the head is fixed in place by inserting two or three threaded pins up the femoral neck and across the epiphyseal plate. Thereafter, to limit weight bearing, crutches should be used for several months.
In patients with symptoms of more than three weeks duration without acute exacerbation, reduction by traction is not effective. The deformity is not easily corrected. If the displacement is mild or moderate (less than one half the width of the femoral neck) the epiphysis should be fixed in situ with threaded pins.
If the displacement is greater and hip motion is severely limited, more extensive surgery is necessary.
Osteonecrosis may follow any form of treatment, but it is most frequently seen after attempts to reduce a chronic slip or after surgical correction made in the proximal part of the femoral neck.
Other possible complications are:
- Pin breakage
- False aneurysm
- Perforation of the posterior cervical cortex, endangering the remaining femoral head blood supply
- Subtrochanteric fracture through the site of insertion
The more pins used, the more likely there will be complications. This has caused a recent trend towards the use of a single cannulated screw.
What is the cause of the slipping?
How severe is the slip?
Is surgery required?
What type of surgical procedure will be used?
Will pins or pegs be inserted?
What are the possible risks and complications of surgery?
How long is the period of recovery?
Will normal hip function be restored?