Slipped Capital Femoral Epiphysis

By admin On Dec 11, 2022

Ovid: Pediatrics

Editors: Tornetta, Paul; Einhorn, Thomas A.; Cramer, Kathryn E.; Scherl, Susan A.

Title: Pediatrics, 1st Edition

> Table of Contents > Section II: – Emergency Department > 11 – Slipped Capital Femoral Epiphysis

Slipped Capital Femoral Epiphysis

David W. Manning

Christopher M. Sullivan

Susan A. Scherl

Slipped capital femoral epiphysis (SCFE) is the most
common adolescent hip disorder and is defined as displacement between
the proximal femoral epiphysis and metaphysis. The displacement occurs
through the hypertrophic zone of the proximal femoral physis. Although
we often conceptualize the epiphysis “slipping” off the femoral neck,
it is the metaphysis that is displaced anterior and proximal with
respect to the epiphysis, resulting in a varus deformity of the hip
because the acetabulum provides a mechanical constraint to prevent
displacement of the epiphysis. Treatment is primarily focused on
preventing further displacement and minimizing the risk of sequelae
such as avascular necrosis of the epiphysis and hip arthrosis.

PATHOGENESIS

Etiology

The etiology of SCFE is unclear. Several hypotheses
(mechanical and endocrine) have been proposed but it is likely that the
true etiology is a combination of factors. Evidence supporting a
mechanical etiology includes the incidence of obesity, increased
physeal obliquity, and femoral retroversion seen in children with SCFE.
The result is increased shear stress across the physis. The role of the
endocrine system in the development of SCFE is linked to the male
predominance as well as the increased incidence in children with
hypothyroidism and those with hypogonadism receiving growth hormone
supplementation. Clinically, SCFE is a disease of obese adolescents who
have increased force transmission across an already widened and
possibly weakened physis associated with hormonal changes such as the
adolescent growth spurt.

Epidemiology

SCFE has a male predominance reported from 60% to 90%
and may occur any time from age 6 to the time of physeal closure. The
average age at diagnosis is 13.5 years for boys and slightly younger,
at 12 years, for girls. The majority of children are clinically obese.
There is a reported ethnic and geographic variation in prevalence. The
lowest reported incidence has been reported in Japan (0.2 per 100,000),
while one of the highest has been reported in the northeastern United
States (10 per 100,000). It has also been reported that SCFE occurs
more commonly in the summer in seasonal climates north of 40°N latitude.

Bilaterality has been reported in as many as 60% of
cases, nearly half of which may be present at the time of initial
presentation. Involvement is usually not symmetric and a high degree of
clinical suspicion should be maintained, not only at the initial
presentation, but throughout the follow-up period. Independent risk
factors for bilateral SCFE include African American heritage and
younger age at diagnosis.

Natural History

Failure of the proximal femoral physis and resultant
metaphyseal displacement may occur gradually over the course of several
months or as an acute event. The course may also be variable with acute
events superimposed on a gradual slippage. Progressive slipping through
the physis is halted by skeletal maturity or treatment. Despite
deformity, patients with uncomplicated SCFE have a normal acetabulum
and intact articular cartilage, and clinically perform very well for
many years. However, more severe displacement is associated with early
onset degenerative arthritis and may also result in injury to the
posterosuperior epiphyseal vessels causing avascular necrosis of the
femoral head (epiphysis).

Classification

The classification of SCFE is traditionally divided into four categories based on history, physical, and radiographic findings (Table 11-1). The stability classification separates patients based on their ability to ambulate (Table 11-2). The stability classification has proved more useful in predicting prognosis and establishing a treatment plan.

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TABLE 11-1 TRADITIONAL CLASSIFICATION OF SLIPPED CAPITAL FEMORAL EPIPHYSIS

Classification	Duration of Symptoms	History	Physical Findings	Radiographic Findings
Preslip	Variable, usually <3 wk	Limp, weakness, pain worse with exertion	Antalgic gait ↓ Internal rotation	Osteopenia of hemipelvis Wide/irregular physis
Acute	<3 wk	Unable to bear weight, severe pain	Unable to ambulate External rotation deformity LLD ↓ Motion secondary to pain	Loss of Klein’s line Positive blanch sign Slip angle on frogleg view
Chronic	>3 wk, up to months or years	Groin, thigh, knee pain; limp	Antalgic gait ↓Internal rotation ↓ Abduction LLD	Metaphyseal remodeling: Posterior/inferior sclerosis Superior/anterior resorption
			External rotation with flexion	Pistol grip deformity
Acute-on-chronic	Acute increase in baseline symptoms	Acute increase in baseline symptoms	↓ Motion secondary to pain Antalgic gait ↓ Internal rotation ↓ Abduction LLD External rotation with flexion	Combination of acute and chronic radiographic changes
LLD, limb length discrepancy.

DIAGNOSIS

Clinical Presentation

Patients with SCFE usually present with complaints of
groin or thigh pain and a limp. The duration of symptoms is corollary
to the different categories in the traditional classification of SCFE
(see Table 11-1). Infrequently the patient
will complain only of medial knee pain (the referral pattern for the
obturator nerve) and a high index of suspicion is needed to make the
diagnosis. All pediatric patients with knee or thigh pain should
undergo hip evaluation.

Physical Examination Findings

Orthopaedic physical findings are corollary to the different categories in the traditional classification (see Table 11-1) and severity of disease. The physical findings may include:

TABLE 11-2 STABILITY CLASSIFICATION OF SLIPPED CAPITAL FEMORAL EPIPHYSIS

Ambulation

Symptoms

Physical Findings

Treatment

Outcome

Stable

Able to ambulate with or without crutches

Moderate pain, worse with activity

Antalgic gait ↓ internal rotation ↓ abduction

In situ pinning

Good to excellent

Unstable

Unable to ambulate with or without crutches

Severe pain groin, thigh, knee

Unable to bear weight

Flexed and externally rotated posture

↓ROM secondary to pain

Gentle (spontaneous) reduction with general anesthetic and pinning

↓Risk of AVN, chondrolysis, early DJD

AVN, avascular necrosis; DJD, degenerative joint disease; ROM, range of motion.

Externally rotated and slightly flexed hip positioning with patient supine
Pain with manipulation of the hip (log roll, flexion, rotation)
Pain with straight leg raise
External rotation of the thigh with passive hip flexion (asymmetric)
Decreased hip flexion
Decreased hip internal rotation
Decreased hip abduction
Limb length discrepancy
Antalgic gait (shortened stance phase)
Abductor lurch

Typical Radiographic Features

The gold standard diagnostic test for SCFE is anteroposterior (AP) and frog-leg lateral pelvis radiographs. The frog-leg

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view best displays the magnitude of the slip and the anterior position
of the metaphysis relative to the epiphysis. The radiographic
appearance of the involved hip is corollary to the different categories
in the traditional classification (see Table 11-1) and severity of disease. The radiographic findings may include:

Figure 11-1 Anteroposterior pelvis radiograph showing widening of the right proximal femoral physis.

Osteopenia of the hemipelvis and proximal femur
Widening of the physis (Fig. 11-1)
Irregularity of the physis
Subtle displacement of the metaphyseal/epiphyseal relationship (Fig. 11-2)
Asymmetry of Klein’s line, most pronounced on AP projection (Fig. 11-3)
Metaphyseal blanch sign (overlap of metaphysis on epiphysis)
Wide displacement of the metaphyseal/epiphyseal relationship
Metaphyseal remodeling (Fig. 11-4)
Resorption of superior and anterior proximal metaphysis (see Fig. 11-4)
Sclerosis of posterior and inferior proximal metaphysis (see Fig. 11-4)
Varus deformity (see Fig. 11-4)

Figure 11-2 Frog-leg radiograph showing mild epiphysical displacement on the right side.

Figure 11-3 Anteroposterior radiograph of a mild slip of the right femoral epiphysis and correspondingasymmetry of Klein’s line.

Figure 11-4
Frog-leg radiograph of bilateral chronic slips, after pinning,
demonstrating varus deformity and metaphyseal remodeling and sclerosis.

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Figure 11-5 Frog-leg projection showing moderate slip of the right femoral epiphysis with corresponding increased Southwick angle.

The severity of SCFE is determined radiographically using two methods:

AP view displacement of the epiphysis on the metaphysis
- □ mild: less than one third
- □ moderate: one third to one half
- □ severe: greater than one half the width of the femoral neck
Frog-leg view Southwick angle (epiphyseal shaft angle) (Fig. 11-5)
- □ mild: less than 30 degrees
- □ moderate: 30 to 50 degrees
- □ severe: greater than 50 degrees.

Other Imaging Studies

A pin-hole lateral bone scan can show uptake in early
preslip SCFE and may aid in early diagnosis when radiographs are
normal. Ultrasound may detect hip joint effusion and metaphyseal
remodeling but is usually not needed for diagnosis. The presence of an
effusion is thought to correlate with an acute event. Magnetic
resonance imaging may be useful in the early detection of avascular
necrosis but is not useful in the diagnosis of SCFE.

TABLE 11-3 DIFFERENTIAL DIAGNOSIS OF SLIPPED CAPITAL FEMORAL EPIPHYSIS

Differential Diagnosis	Age (Yr)	Weight	Bilaterality (%)	Mild/Moderate/Severe (%)
Idiopathic	12.8 ± 1.6	94% ≥ 50th percentile	35	55/26/19
Endocrine	15.3 ± 5.3	No trend	61	60/25/15
Osteodystrophy	11.4 ± 4.4	No trend	90	53/7/43
Radiation	10.5 ± 3.3	No trend	28	81/11/8
Adapted from Reynolds R. Diagnosis and treatment of slipped capital femoral epiphysis. Curr Opin Pediatr 1999;11:1:80-87.

Differential Diagnosis (Table 11-3)

Idiopathic (most common)
Endocrinopathy
- □ Hypothyroidism (most common)
- □ Hypopituitarism
- □ Growth hormone deficiency
- □ Hypogonadism
- □ Craniopharyngiomas
Osteodystrophy
Radiation

Patients between the ages of 10 to 16 years and greater
than the fiftieth percentile for weight (negative age/weight test) can
routinely be considered to have idiopathic SCFE (Table 11-4).
Children who fall outside these boundaries (positive age/weight test)
and children less than the tenth percentile for height on a standard
Tanner growth chart are significantly more likely to have an underlying
endocrine disorder. Preliminary endocrine screening should include
thyroid-stimulating hormone and free thyroxine serum levels.

TREATMENT

The ideal management of SCFE should prevent progression
of disease, provide pain relief, have few complications, be easy for
the patient and family to tolerate, and be technically simple. The gold
standard of treatment is immediate bed rest and in situ
stabilization with single or multiple pins or screws. Postoperatively,
the patient is allowed flatfoot weightbearing with crutches. The
following section is divided into treatment options for stable and
unstable SCFE.

Stable SCFE

Hip Spica Cast

Casting for 3 months was thought to be effective at
preventing further progression and also treating or preventing
bilateral SCFE. However, progression of slip occurs in up to 10% of
cases and spica casting has also been shown to have an unacceptable
rate of chondrolysis. Articular cartilage nutrition occurs primarily
through diffusion from the synovial fluid and this mechanism is
severely hampered by

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immobilization. Treatment in a hip spica cast is not recommended and is of historical value only.

TABLE 11-4 ATYPICAL RESULTS IN SCREENING FOR SLIPPED CAPITAL FEMORAL EPIPHYSIS

Cause	Age/Weight Test (AWT)	Height	Significance
Idiopathic	10-16 yr and ≥50th percentile (negative test)	≥10th percentile	Negative AWT: 93% negative predictive value No need for endocrine evaluation
Endocrine	≥16 yr or ≤10 yr and ≤ percentile (positive test)	≤10th percentile	Positive AWT: 52% positive predictive value Height: 90% sensitivity, 98% negative predictive value necessitate endocrine evaluation
Other	Variable	Variable	History of radiation or renal disease
Adapted from Loder RT, Greenfield MVH. Clinical characteristics of children with atypical and idiopathic slipped capital femoral epiphysis: description of the age-weight test and implications for further diagnostic investigation. J Pediatr Orthoped 2001;21:4:481-487.
Reynolds R. Diagnosis and treatment of slipped capital femoral epiphysis. Curr Opin Pediatr 1999;11:1:80-87.

In Situ Pinning

Open or percutaneous pinning of the slip without
reduction can be accomplished with a single cannulated screw or pin and
is considered the gold standard. The screw or pin should enter the
anterior aspect of the proximal femur, cross the physis at 90 degrees,
and enter the center of the epiphysis with the tip below subchondral
bone. A screw placed in this orientation accommodates the deformity,
and has maximal stability with minimal risk of complications (Fig. 11-6).
Postoperatively, partial weightbearing with crutches is advanced as
tolerated. In stable slips, an additional second screw creates only a
minimal increase in stability and theoretically can negatively impact
femoral epiphyseal circulation.

Figure 11-6 Operative anteroposterior (A) and frog-leg (B) radiographs showing single screw fixation.

Cervical Osteotomy

Open reduction and osteotomy of the femoral neck with
multiple pin fixation is associated with an unacceptable rate of
avascular necrosis (AVN) and is not recommended.

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Intertrochanteric Osteotomy

Anterolateral closing wedge osteotomy at the level of
the lesser trochanter and fixation with a compression hip screw can
stabilize SCFE and reduce deformity. The result is an improved range of
motion at the expense of a more involved procedure that may exacerbate
any leg length discrepancy. Osteotomy may be indicated in stable
chronic SCFE with a Southwick angle greater than 60 degrees or as a
later reconstructive option.

Subtrochanteric Osteotomy

The correction of deformity is inferior to that obtained
with an intertrochanteric osteotomy. The procedure is not routinely
performed.

Unstable SCFE

The management of unstable SCFE is difficult and the
outcome may be poor. Unstable SCFE may be associated with AVN despite
adequate treatment because unstable slips tend to be severe and
potentially involve injury to the posterosuperior epiphyseal vessels.
It has been argued, but not clearly proven, that early decompression of
the hip joint (aspiration or open capsulotomy), gentle reduction of
deformity, and internal fixation may decrease the incidence of AVN.
Frequently, when the patient is anesthetized, a spontaneous partial
reduction will occur. In patients with a severe slip angle there is
little epiphyseal-metaphyseal overlap and multiple screw fixation may
be impossible. Partial reduction often allows two-screw fixation and
improved rotational stability in these difficult cases.

At a minimum, the patient with an unstable SCFE should
be placed on bed rest until open or percutaneous pinning performed.
Flatfoot weightbearing may begin on the first postoperative day and
progress to weightbearing as tolerated once radiographic evidence of
early callus is seen.

COMPLICATIONS

AVN

AVN is a devastating complication involving necrosis and
collapse of the femoral head with resultant pain, stiffness, limp, and
degenerative changes. Radiographs confirm the diagnosis. Risk factors
include:

Unstable slip
Severe slip angle
Acute slip
Reduction attempt of chronic slip deformity
Screw placement in superolateral quadrant of the epiphysis
Femoral neck osteotomy

Chondrolysis

Chondrolysis is a breakdown of proximal femoral
articular cartilage of unknown etiology. Patients present with pain,
stiffness, limp, and contracture. Joint space may be narrowed on
radiographs and arthrogram. Risk factors include:

Severe slip
Prolonged symptoms without treatment
Cast immobilization
Unrecognized pin/screw penetration into joint

The complications of AVN and chondrolysis are frequently disabling. Reliable treatment options do not exist.