Slipped capital femoral epiphysis
‍Image showing the epiphysis of the femoral head in relation to the metaphysis and growth plate

Definition

Slipped capital femoral epiphysis (SCFE) is a condition affecting teenagers whereby the growth plate of the femoral head (capital femoral epiphysis) slides backwards.

Model representing the slipping capital femoral epiphysis

Pathology

A slipped capital femoral epiphysis is the most frequent pathology of the hip encountered in teenagers between 12 and 16 years of age. It consists in the instability of the growth plate that is likely weakened by a rapid growth spur after puberty. This weakness facilitates the slip of the femoral head backwards to the femoral bone also in the absence of injury.

In growing children the growth plate is located on either extremity of the bone between the epiphysis and the metaphysis. It is found in long bones (femur, radius, ulna, metacarpal bones). It consists of a specific of proliferating cartilage cells (chondrocytes) that allow the lengthening of the bone above the metaphysis, which in the hip is the femoral head. When child development is complete the growth plate becomes fully ossified.

Illustration of a stable and unstable slipped femoral epiphysis

Classification

The Loder classification of slipped capital femoral epiphysis distinguishes between:

Stable – patient can bear weight with/without crutches (small risk of osteonecrosis)

Unstable – patient cannot weight bear or walk (high risk of osteonecrosis)

Disease stages

Four different stages of the slipped capital femoral epiphysis have been described:

    Pre-slip: formation of a large epiphyseal line without slippage

    Acute form: sudden spontaneous slippage

    Acute-on-chronic: acute slippage in case of existing chronic slip

    Chronic: progressive slippage (most frequent pathology).

 

Grading system relative to extent of slippage:

Grade I   0-33%

Grade II  34-50%

Grade III  > 50%

A slipped capital femoral epiphysis can be associated with a number of medical conditions including:

Endocrine (hormonal) disorders

Hypothyroidism (overproduction of thyroid stimulating hormone, TSH)

Obesity

Osteodystrophy of chronic renal failure

Growth hormone treatment

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

A fall can cause a slipped capital femoral epiphysis in a growing adolescent

Causes

The causes underlying a slipped capital femoral epiphysis are not known. It is believed that increasing forces onto the growing hip will cause the slipping of the less stable epiphysis above the firmer femoral metaphysis. The pathology does not require an injury to develop, however a traumatic event can trigger the onset of the disease. A slipped capital femoral epiphysis has a bilateral occurrence in 20-40% of cases. Obesity is recognised as a causative factor due to the increased pressure of the weight on the hip joint

Obesity is a risk factor of the disease due to the pressure of body weight on the femoral head

Risk factors

The main risk factors for a slipped capital femoral epiphysis are:

Adolescent age between 10 and 17 years

Male gender (three times more frequent)

Left hip more affected than right hip

Femoral retroversion (deformity of proximal femur due to contracture of the external rotators of hip, causing external leg rotation and an out-toeing gait)

Obesity

Traumatic events

Inflammatory conditions (arthritis)

Hormonal dysfunction (hypothyroidism, growth hormone deficiency

Cancer treatment (chemotherapy, radiotherapy)

Leg length discrepancy is a symptom of a slipped capital femoral epiphysis

Symptoms

The most common symptoms of a slipped capital femoral epiphysis are:

Mild to chronic acute pain to groin, thigh, knee

Increasing pain with walking, running, jumping

Abnormal gait, limp on affected side

Reduced hip motion and internal rotation

External rotation of the limb while walking

Altered limb alignment

Leg length discrepancy

Weakness of thigh muscles (atrophy)

Trendelenburg test is used to detect leg length discrepancy

Diagnosis

Physical examination begins with medical history including past injuries to exclude other pathologies of the hip. The examiner will investigate the child ability to bear weight possibly resulting in a severe slip. Testing the range of internal rotation of the hip is critical to confirm the diagnosis of slipped capital femoral epiphysis. Obligatory external rotation occurs when the hip is passively flexed to 90 degrees. Diagnostic measures include:

Testing for Trendelenburg gait

X-ray of the hips in antero-posterior and lateral view with patient in a “frog-leg” position that is used for the following methods:

The Wilson method determines the level of epiphysis displacement on X-ray images:

- Mild displacement (< 1/3 of the metaphysis width)

- Moderate displacement (between 1/3 and 1/2)

- Severe displacement (>1/2 of the width)

The Southwick method measures the epiphyseal shaft angle on “frog-leg” X-ray images. The angle is obtained by subtracting the angle of the unaffected hip from the affected hip resulting into:

- Mild slip with <30 degrees

- Moderate slip between 30 and 50 degrees

- Severe slip >50 degrees

MRI is used in early disease stages when X-ray does not show widening of epiphysis

Endocrinology blood testing is recommended in children younger than 10 years or older than 16 years of age

Treatment

Reduced weight bearing is recommended in conservative treatment

Nonoperative treatment

The goal of conservative treatment is to prevent the progression of a slipped hip and the ensuing complications while the hip is still stable. The patient is advised to avoid weight bearing by using crutches or a wheel chair. Additional conservative treatment includes:

Rest

Pain management with analgesics

Anti-inflammatory drugs (NSAIDs)

Pinning of the femoral head stabilises the epiphysis

Surgical Treatment

Surgical treatment for a slipped capital femoral epiphysis by a paediatric orthopaedic surgeon is recommend in both early and chronic stages of the disease. By stabilising the epiphysis, surgery prevents further slippage and facilitates the correct sealing of the epiphysis to ensure normal bone growth. The following techniques are employed: 

In case of stable slipped capital femoral epiphysis:

Percutaneous screw fixation (screws inserted through the skin) is mostly used

In case of unstable hip, more complex surgeries are performed to improve osteonecrosis:

Epiphyseal reduction and pinning to hold the epiphysis firmly (avoid too may screws for risk of late complications)

Proximal femoral osteotomy (partial removal of bone material) is usually performed when the epiphysis has closed. It can be achieved at the subcapital, femoral neck, inter- and sub-trochanteric femur. This allows to obtain realignment of the hip joint

Open reduction consists of a surgical dislocation followed by epiphyseal repositioning

 

Model and X-ray of an avascular necrosis of the femoral head

Complications

Most common complications following surgery for the treatment of slipping capital femoral epiphysis are:

Avascular necrosis of the femoral epiphysis due to damage of the vessels around the bone following a failed epiphysis reduction or osteotomy of the femoral neck

Contralateral onset of slipped capital femoral epiphysis

Chondrolysis (degeneration of articular cartilage)

Femur fracture post-fixation

Slip progression

Femoral deformity

Hip stiffness

Limb length discrepancy

Post-surgical infection

Chronic pain

Hip osteoarthritis

Initial physiotherapy to restore mobility and function of the hip

Rehabilitation

Physical therapy can commence after the acute phase to achieve muscle strengthening and restoring proprioception and balance. Increasing fitness is necessary prior to return to active sport. 

Following surgery for a slipped capital femoral epiphysis, it is norm to reduce weight bearing with the use of crutches for 6-8 weeks. Some specialists advise to avoid intensive sport until the epiphysis has completely sealed to prevent the progression of the disease. The patient is subjected to regular X-ray monitoring for 18-24 months to follow on slippage progression, onset of slipping to the contralateral capital femoral epiphysis and epiphysis closure. During this phase the child’s physical activity may be significantly restricted.

Double pinning helps preventing the condition on the contralateral side

Prevention

 A slipped capital femoral epiphysis is not easily preventable and has a high risk to develop on both hips. Early detection and treatment is essential to avoid a hip to become fully unstable and thus requiring invasive surgical treatments. Careful changes in life style following the diagnosis can be beneficial in preventing the complications arising from the pathology. Prophylactic pinning of the contralateral, unaffected capital femoral epiphysis is advocated but remains controversial.