Slipped capital femoral epiphysis (SCFE) is a condition of the adolescent hip in which the ball (epiphysis) at the top of the femur slips off the neck of the bone through the growth plate. It is one of the most common hip disorders in adolescents and requires prompt surgical treatment — delay in diagnosis or treatment can result in avascular necrosis of the femoral head, a catastrophic and largely irreversible complication.
SCFE is both a pediatric emergency and a long-term hip health concern. In the acute setting, an unstable SCFE carries the same urgency as a displaced femoral neck fracture — the blood supply to the femoral head is at risk and surgery cannot wait. Over the long term, even well-treated SCFE predisposes to femoroacetabular impingement (FAI) from the residual deformity of the femoral neck, which then damages the hip labrum and cartilage and accelerates hip osteoarthritis — often in patients still in their 20s and 30s. Avascular necrosis (AVN) of the femoral head is the most feared acute complication, occurring in 25–50% of unstable SCFE cases. SCFE may also be confused with transient synovitis in its early stages, particularly when knee pain is the presenting complaint.
Causes
Mechanical and hormonal factors.
SCFE results from a combination of excessive mechanical shear forces across a growth plate that has been weakened by the hormonal changes of puberty. During the adolescent growth spurt, the proximal femoral physis undergoes a period of relative vulnerability — the growth plate is wider, less well-organized histologically, and oriented more vertically than in younger children, making it less resistant to shear stress. Increased body weight dramatically amplifies these shear forces at the growth plate with each step. Hormonal influences — including relative growth hormone excess and sex hormone insufficiency during certain phases of puberty — further impair physeal strength by altering the columnar organization of growth plate cartilage. The net result is progressive or sudden posterior and inferior displacement of the femoral epiphysis relative to the femoral neck through the physeal cartilage.
Risk factors.
SCFE most commonly affects adolescents between ages 10 and 16 — peak incidence is around age 12 in girls and 13–14 in boys, corresponding to the typical timing of the adolescent growth spurt in each sex. Obesity is by far the strongest single risk factor, present in the majority of affected patients. Endocrine disorders that independently weaken the growth plate — hypothyroidism, growth hormone deficiency, hypogonadism, and renal osteodystrophy — are important to recognize because they may cause SCFE outside the typical age range, and these patients almost always require bilateral prophylactic pinning given the markedly elevated bilateral risk. Approximately 20–40% of SCFE cases involve both hips, either simultaneously or sequentially, making bilateral imaging mandatory at diagnosis. Boys are affected more commonly than girls overall, and the condition is more prevalent in patients of African American and Pacific Islander descent.
Symptoms
Patients typically report hip, groin, thigh, or knee pain with a limp that may have developed suddenly (unstable SCFE) or gradually over weeks to months (stable SCFE). The knee pain referral pattern is one of the most clinically important features of SCFE — it is well established that a significant proportion of SCFE patients are initially evaluated and treated for knee pathology before the hip diagnosis is made, delaying treatment and worsening outcomes. Any adolescent with unexplained knee pain and a limp must have the ipsilateral hip examined and imaged. The affected leg characteristically appears shortened and externally rotated at rest, and with hip flexion the leg obligatorily externally rotates — a pathognomonic finding called the Drehmann sign. Range of motion is restricted, particularly internal rotation and abduction. In unstable SCFE, pain is severe enough that the child refuses all weight-bearing and requires urgent surgical evaluation.
Diagnosis
X-rays of both hips — AP pelvis and frog-leg lateral views — are the standard diagnostic imaging. The frog-leg lateral view is the most sensitive plain film projection for detecting SCFE, as the slip is predominantly posterior and may be missed on the AP view alone. Classic findings include the Steel sign (a line drawn along the superior femoral neck, the Klein line, failing to intersect the femoral epiphysis as it does on the normal side) and the "ice cream scoop falling off the cone" appearance of the slipped epiphysis. Both hips must always be imaged because of the high rate of bilateral involvement. An MRI is the most sensitive study for pre-slip (physeal widening and bone marrow edema without displacement), early or subtle slips that are equivocal on X-ray, and early detection of the most feared complication — avascular necrosis of the femoral head — which may develop silently in the weeks following surgical treatment and requires early identification for management. MRI also evaluates the contralateral hip for subclinical early physeal changes before frank slippage occurs.
Classification
SCFE is classified by two independent systems — stability and severity of displacement — both of which are essential for treatment planning.
- Stable SCFE: The patient can bear weight with a limp. The periosteum and surrounding soft tissue remain intact. AVN risk is low (less than 10%). In situ screw fixation is the standard treatment. Accounts for approximately 90% of cases.
- Unstable SCFE: The patient cannot bear weight due to severe pain. The periosteal and vascular envelope is disrupted, placing blood supply to the femoral head at high risk. AVN occurs in 25–50% of unstable cases. Requires urgent surgical stabilization — time is critical.
- Mild slip: Less than one-third epiphyseal displacement on the lateral view. Excellent prognosis with in situ fixation.
- Moderate slip: One-third to one-half displacement. Good prognosis with fixation; residual cam deformity may require later FAI treatment.
- Severe slip: Greater than one-half displacement. Higher risk of long-term deformity, FAI, and early arthritis. Surgical reduction is considered at specialized centers.
Treatments
SCFE is a surgical condition — once diagnosed, the patient should be made non-weight-bearing immediately and taken to the operating room urgently. The fundamental goals are to stabilize the slip and prevent further displacement, minimize the risk of AVN, and address the residual deformity that predisposes to long-term hip problems.
In situ pinning (stable SCFE): A single cannulated screw placed percutaneously across the growth plate, centered in the femoral epiphysis, is the standard and highly effective treatment for stable slips of any severity. The screw stabilizes the slip in its current position without attempting reduction — attempted forcible reduction of a stable slip dramatically increases AVN risk and is contraindicated. The procedure is typically performed within 24–48 hours of diagnosis. Weight-bearing is protected postoperatively until the growth plate closes, confirmed by serial X-rays. After surgery, physical therapy helps restore range of motion and strength.
Unstable SCFE — urgent surgical stabilization.
Unstable SCFE is a true orthopedic emergency requiring surgery within hours of diagnosis. The surgical approach is debated — some surgeons perform gentle closed reduction before screw fixation to attempt to restore blood flow by decompressing the femoral head, while others stabilize the slip in its displaced position to avoid the additional vascular injury that forceful manipulation can cause. The modified Dunn procedure — an open surgical approach that allows anatomic reduction of the slip under direct visualization while protecting the posterior periosteal blood supply — is performed at specialized pediatric orthopedic centers for severe unstable cases and has demonstrated encouraging results for reducing AVN rates compared to closed manipulation, though it requires significant surgical expertise.
Prophylactic pinning of the contralateral hip.
Given the 20–40% rate of bilateral SCFE and the significant morbidity of a second untreated slip, prophylactic screw fixation of the contralateral unaffected hip is strongly considered for younger patients (under 10 years), those with endocrine disorders, and those at particularly elevated risk based on physeal widening on MRI. The decision is individualized and involves balancing the low but real risk of a prophylactic procedure against the higher risk of a symptomatic contralateral slip requiring emergency treatment.
Long-term management of residual deformity.
Even after successful fixation, the malunited femoral neck deformity that persists following a moderate or severe SCFE creates a cam-type femoroacetabular impingement morphology that damages the labrum and cartilage with every hip flexion cycle. Patients with significant residual deformity require long-term monitoring for the development of FAI symptoms and early hip arthritis, and may be candidates for corrective osteotomy or hip arthroscopy in adolescence or young adulthood to address the deformity before cartilage damage becomes irreversible.
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