Definition
Slipped capital femoral epiphysis (SCFE) is a condition affecting teenagers whereby the growth plate of the femoral head (capital femoral epiphysis) slides backwards.
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.
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 incase 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
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
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)
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)
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 epiphysisEndocrinology blood testing is recommended in children younger than 10 years or older than 16 years of age.
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)
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.
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
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.
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.