Introduction
This is a condition characterized by relative displacement between the capital femoral epiphysis (CFE) and the proximal femoral metaphysis. This was described by Ernst Muller, who called it Schenkelhalsverbiegungen im Jungesalter, meaning "bending of the femoral neck in adolescence." The proximal femoral neck and femoral shaft is typically translated anteriorly and externally rotated relative to the femoral head, which is stabilized in the acetabulum
Epidemiology
Cumulative risk: 1-2/1000 for males; 1/2000 - 3000 for females
Age: 10-13 years old for girls; 12-15 years old for boys.
Anatomy
Slipped capital femoral epiphysis (SCFE) results from increased stresses across a weakened physis, usually as a result of of both biomechanical and biochemical factors contributing to the development of the slip.
Factors affecting stability of the physis include the following:
- Perichondrium and perichondrial ring (fibrous tissue) - Progressively thin with age.
- Mammillary projections and Contour of the growth plate - contribute to its resistance to linear shear and torque forces and assume increasing importance as the perichondrial ring thins.
- Growth plate thickness - Mainly affected by biochemical and endocrine factors.
- Mechanical factors - Increased stress across the physis
- .Deep acetabulae, increased physeal slope and relative femoral retroversion, increase the stress across the physis
- Obesity- Increases the forces across the physis. It is also associated with femoral retroversion, which further increases the stress across the physis.
- Biochemical factors - SCFE most common in the peripubertal age group; possible contribution of hormones on the physes to the likelihood of developing a slip
- Growth hormone - Causes widening of the physes and consequent weakening. There is an increased risk of slippage in patients on groth hormone supplementation.
- Sex hormones - Increased physeal width and decreased physeal strength from testosterone, probably accounting for increased frequency in boys; narrowing of the physis and increased physis strength from estrogen, possibly explaining why slips seldom occur in postpubertal females.
- Thyroid hormone - slips can occur in patients with hypothyroidism and those receiving thyroid hormone replacements for hypothyroidism.
Pathogeneis
The exact etio-pathogenesis of this condition is not known, however there is a strong relationship between obesity and the development of a slipped capital femoral epiphysis. 50% of affected patients are at or above the 90th percentile for weight.
Other conditions that are associated with the development of a slip are:
1. Endocrinopathies: hypothyroidism, hypogonadism, growth hormone abnormalities, panhypopituitarism, hyperparathyroidism and acromegaly. SCFE is 6 times more common in patients with an endocrinopathy.
2. Renal failure
3. Radiation
Natural History
10-20% of patients develop a symptomatic contralateral slip during adolescence. Long term studies have reported bilateral involvement in approximately 60% of patients in adulthood. Sixty - 100% of patients with endocrinopathies will have bilateral slips.
Patient History and Physical Findings
AGE: 10-14 years in girls and 11-15 years in boys.
GENDER: Boys more frequently affected than girls.
SYMPTOMS:
Affected individuals are often obese and usually present with pain and or a limp. The pain is usually in the groin, though up to a third of patients may complain of thigh or knee pain. It is therefore imperative to assess the hip in an adolescent presenting with knee pain. Individuals with unstable slips are unable to weight bear on the affected lower extremity.
PHYSICAL EXAMINATION: may show
- Externally rotated attitude of the affected lower limb
- Restriction of flexion, abduction, and internal rotation of the affected hip in varus slips, and restriction of flexion, adduction, and internal rotation in valgus slips
- Obligatory external rotation on flexion
- Wasting of the thigh in chronic slips
- Impingement sign (Pain on flexion to 90 degrees and internal rotation of the hip) may be seen in chronic slips.
- Limb length discrepancy: True supratrochanteric shortening (Bryant triangle, Nélaton line) of the affected lower extremity in unilateral cases.
- Gait abnormalities: Antalgic gait pattern in acute or acute on chronic slips and Trendelenburg gait may be seen in patients with chronic slips
Imaging and Diagnostic Studies
The diagnosis is usually established on plain films. It is important to obtain both AP and lateral views. Up to 14% of SCFE's may not be evident on AP views. Lateral radiographs are the most sensitive for detecting mild degrees of slip. Frog leg lateral and cross table lateral views with the hip in 30 degrees or less of external rotation are both acceptable methods. However, in the setting of an unstable, acute SCFE a frog leg lateral radiograph is not recommended preoperatively due to pain and the risk of displacement of the SCFE. In patients with acute, unstable slips it is best to obtain a cross table lateral view.
Radiographic evidence of a slip includes:
- Widening and irregularity of the physis (preslip)
- Klein's line
- Metaphyseal blanch sign of Steel
- Loss of femoral head-neck offset.
Radiographic Classification of SCFE:
Quantified by the amount of femoral head displacement as a percentage of the femoral neck diameter:
- <33% - mild
- 33-50% - moderate
- >50% - severe
Southwick Angles: angles between the proximal femoral phsis and the femoral shaft ("head-shaft angles") and both the AP and lateral views. The differnce between the affected and unaffected sides are referred to as the Southwick angles.
- Difference of <30 degrees: mild
- Difference of 30-50 degrees: moderate
- Difference of >50 degrees: severe
CT: Rarely needed in initial workup. May be useful in determining whether or not physeal closure is present in patients who present late.
Ultrasound: At present there is little use for ultrasound in the routine workup of SCFE.
MRI: Useful in the early stages of the disease ("Preslip") and may demonstrate periphyseal edema with or without an effusion in the hip. MR imagaing is also useful in assessment of sequelae of slips including femoro-acetabular impingement and osteonecrosis.
Bone Scan: May be useful in detecting the development of osteonecrosis.
Risk Factor Workup: Routine screening for underlying endocrinopathies is not warranted. Height below the 10th percentile is a useful clinical screening characteristic for endocrinopathies.
Differential Diagnosis
Acute slips:
- Fracture
- Groin pull
- Infection
- Tumors
Chronic slips:
- Impingement syndromes
- Perthes disease
- Juvenile idiopathic arthritis
Treatment
Include:
Medical therapy
Nonoperative treatment: There is little role for nonopoerative management of SCFE. Spica casting is rarely used due to patient discomfort, associated complications, and relatively high rate of slip progression.
Operative treatment: Forceful manipulation of the hip is never indicated due to the high incidence of associated osteonecrosis.
Indications and contraindications: Prophylactic pinning of the contralateral hip is recommended in patients with endocrinopathies as 60-100% will develop bilateral slips.
Pearls and Pitfalls
Tips and problems to avoid
Postoperative Care
Include immediate postoperative care and rehabilitation
Outcome
Include functional and prosthetic survivorship data as applicable
Complications
Include overview of complications
Selected References
Insert selected references and landmark articles
