Deteriorating Mobility in a 9-Year-Old: Case Presentation

A 9-year-old boy with asthma, marked obesity, and bow legs (genu varum) presents to the emergency department (ED) complaining of left hip and knee pain. He refuses to bear weight on his left leg. His mother reports that the child fell down in the street 2 days ago. The pain is described as mild to moderate in intensity. The patient denies any numbness or tingling in the distal left lower extremity. No skin laceration or bruising is reported by the family. Upon further questioning, the mother admits to having witnessed evolving symptoms over the past 2 months. She describes a worsening limp, decreasing mobility, and increasing left hip and knee pain, without any identified inciting trauma.

The patient was brought to the ED 10 months before this presentation for a similar episode of left knee pain after a vague history of a fall. At that visit, a radiograph of the affected knee demonstrated changes consistent with moderate juvenile Blount disease (arrow). The patient was given a prescription for a nonsteroidal anti-inflammatory drug as needed for pain control and was discharged. The symptoms resolved after only 3 days, and the child was asymptomatic for the following 8 months. He has no previous history of surgery and no known drug allergies, and he is up to date on his immunizations. The patient's mother denies exposure of the child to secondhand smoke. The family history is noncontributory. What is Blount disease and what are the expected radiographic findings?

Answer: Blount disease (shown) is an uncommon growth disorder characterized by disordered ossification of the medial aspect of the proximal tibial physis, epiphysis, and metaphysis. This progressive deformity is manifested by varus angulation and internal rotation of the tibia in the proximal metaphyseal region immediately below the knee. The natural history of this disease leads to irreversible pathologic changes, especially at the medial portion of the proximal tibial epiphysis because of growth disturbances of the subjacent physis. The previous slide's radiograph demonstrates moderate-to-severe changes in the proximal left tibia. Note the depression of the plateau, beaking, and metaphyseal sclerosis. The tibial growth plate is widened and irregular, and the distal femoral growth plate shows changes as well. Mild irregularity and slight widening are seen.^[1]

Vital signs are as shown. The child is alert and in no acute distress. Neurovascular examination reveals normal pulse, capillary refill, sensation, and motor function. The right and left upper extremities are unremarkable. The right lower extremity is normal. The left hip has a decreased range of motion, with pain elicited on passive internal rotation while the patient is lying in the supine position. The left groin and left knee are tender to palpation. The left knee has a decreased range of motion with no swelling, laxity, or effusion. The left ankle and foot examinations are unremarkable. The patient refuses to bear weight on the left lower extremity and demonstrates an antalgic gait. There are no abrasions, ecchymosis, or lacerations.

What is the next step?
A. Blood work
B. X-ray
C. Computed tomography (CT) scan
D. Joint reduction

Answer: B. X-ray

The frog-leg radiograph of the patient’s hips demonstrates prominent widening of the physis on the left (arrow).

Which of the following may have a widening of the proximal femoral physis on radiograph?
A. Transient synovitis
B. Osgood-Schlatter disease
C. Slipped capital femoral epiphysis
D. Legg-Calvé-Perthes disease

Answer: Both C. Slipped capital femoral epiphysis and D. Legg-Calvé-Perthes disease

Osgood-Schlatter disease is one of the most common causes of knee pain in an adolescent, consisting of pain and edema of the tibial tubercle (shown). It is generally a benign, self-limited condition associated with traction apophysitis of the tibial tubercle due to repetitive strain on the secondary ossification center of the tibial tubercle.^[2] Transient synovitis is the most common cause of nontraumatic acute hip pain in children aged 3-10 years. The disease causes arthralgia and arthritis secondary to transient inflammation of the synovium of the hip. Radiographic imaging is often normal and the condition is self-limited.

Image courtesy of Wikipedia Commons.

Slipped capital femoral epiphysis (SCFE) is a unique type of instability of the proximal femoral growth plate for which the underlying defect may be multifactorial (eg, mechanical and constitutional factors). It is a rare pediatric and adolescent hip disorder, but accurate diagnosis combined with immediate treatment is critical. The patient may report hip pain, medial thigh pain, and/or knee pain; an acute or insidious onset of a limp; and decreased range of motion of the hip. On plain radiographs, the femoral head is displaced posteriorly and inferiorly (shown) in relation to the femoral neck and within the confines of the acetabulum.^[3]

Image courtesy of Wikipedia Commons.

The frontal radiograph of the child’s hips is shown. What bony abnormalities of the left hip are revealed?

Answer: The radiograph reveals loss of the normal spherical shape of the left capital femoral epiphysis in comparison with the normal right side. The contour is flattened most severely along the lateral aspect (blue arrow). The left femoral ossification center is sclerotic, small in size, and presents with slight subluxation laterally (purple arrow). Radiolucent fissures are present superiorly and a large irregular cystic lucency occupies the left proximal femoral metaphysis (orange arrow). What diagnosis is suggested by the findings indicated by the arrows?

Answer: Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease (LCPD) is a childhood osteonecrosis of the hip. It begins with multiple episodes of ischemia to the femoral head. The bone undergoes collapse, resorption, reossification, and eventual healing. LCPD is more common in boys, with a 5:1 male-to-female ratio. It occurs more commonly in Caucasian children between the ages of 3 and 12 years, with peak incidence between 4 to 8 years of age.^[3] Family history of the disease is present in 6% of patients. The incidence ranges from 0.4 to 29.0 per 100,000 children.^[4-5]

Differential diagnoses for LCPD include toxic synovitis, slipped capital femoral epiphysis, acute rheumatic fever, tuberculosis, arthritis, and tumors. The etiology of LCPD is unknown, but it may be associated with exposure to passive smoking, low socioeconomic status, trauma, genetic factors, and dietary deficiencies.^[4,6-7]

Approximately 90% of LCPD cases are unilateral. The remaining 10% usually present with unilateral symptoms, but go on to later develop disease of the contralateral hip. Involvement of both hips at the same time is uncommon. This sequence of bilateral hip findings can help differentiate LCPD from other disorders, such as SCFE (shown).

Which of the following is not usually associated with Legg-Calvé-Perthes disease?
A. Hip pain
B. Knee pain
C. Trauma
D. Limp

Image courtesy of Wikipedia Commons.

Answer: C. Trauma

Children with LCPD most often present with a limp, hip pain, or knee pain.^[8] Families often deny associated traumatic events, but sometimes report inciting injuries.

What is the clinical course of Legg-Calvé-Perthes disease?
A. Joint dislocation
B. Femur fracture
C. Avascular necrosis of the femoral head
D. Transient synovitis

Answer: C. Avascular necrosis of the femoral head

An adult patient with residual coxa magna and plana deformity with superimposed joint changes (arrow) is shown. Multiple episodes of ischemia of the femoral head lead to infarction and necrosis. The magnitude of structural changes depends on the extent of osteonecrosis and the amount of mechanical pressure exerted on the joint. Dead bone is reabsorbed, and revascularization and restoration of the epiphysis occur over 2–4 years. The femoral head flattens and collapses; it is in danger of fracture and subluxation. It may be restored to a normal appearance similar to that of the unaffected hip, or it may become flattened (coxa plana) and widened (coxa magna), with the development of coxa vara.^[4,6,8,9]

Patients diagnosed with LCPD at younger ages have more favorable clinical courses. Patients diagnosed at older ages typically require more intervention and generally experience poorer outcomes.^[10]

How is the diagnosis of LCPD usually made?
A. Physical examination
B. Intraoperatively
C. Anteroposterior (AP) and frog-leg lateral plain radiographs
D. CT scan

Answer: C. Anteroposterior (AP) and frog-leg lateral plain films

This image shows stage II LCPD. Note the slight widening of the left hip joint representing a small joint effusion. Joint widening can also be secondary to hypertrophy of the cartilage. Plain radiographs have a sensitivity of 97% and a specificity of 78% in the detection of LCPD. Both hips should be imaged for comparison. Both AP and frog-leg views should be done. The AP view will show more advanced features of LCPD, such as enlargement, flattening, sclerosis, or fragmentation of the epiphysis. However, the lateral view is better for early changes such as crescentic subchondral lucency, which is easily missed on the AP view.^[9,11]

Early radiographic signs of LCPD include a small femoral epiphysis (96%), sclerosis of the femoral head with sequestration and collapse (82%), and widening of the joint space caused by thickening of the cartilage, failure of epiphyseal growth, the presence of joint fluid, or joint laxity (60%).^[5] This image shows widening of the left hip joint, representing a small joint effusion.

This image shows flattening and early fragmentation of the left femoral head (blue arrow) and femoral neck cysts (orange arrow). The femoral head is obviously smaller on the left than on the right. Late signs of LCPD on radiographs include delayed osseous maturation of a mild degree, radiolucent crescent lines representing subchondral fractures, femoral head fragmentation and femoral neck cysts, loose bodies, coxa plana (disintegration of capital femoral epiphysis), and coxa magna (remodeling of the femoral head, which becomes wider and flatter).^[5]

Coronal T2-weighted magnetic resonance imaging (MRI) indicates irregularity and flattening of cortical margins of the left femoral epiphysis. Mild joint effusion, subluxation, and hinge deformity of the left femoral head are shown. If the diagnosis is apparent on plain films, no further imaging is needed. However, if suspicion is still high and plain films are normal, MRI and bone scan can detect disease before plain film abnormalities are evident. Although CT scans may also detect early changes not visualized on plain films, their use is limited due to the higher doses of radiation.^[5,9]

Which of the following is a classification scheme used to grade LCPD?
A. Catterall criteria
B. Salter-Thompson classification
C. Herring classification
D. All of the above

Answer: D. All of the above

One LCPD classification system, the Catterall criteria, is shown.^[5] Many different classification schemes have been devised to grade the severity of disease based on radiographic findings. To date, there is no consensus as to which classification scheme is superior.

This axial nonenhanced CT scan through the hip shows a loss of structural integrity in the right femoral head. Initial management of LCPD is non-weight-bearing and referral to an orthopedic surgeon. Treatment options range from conservative, such as physiotherapy, Botox injections, wheelchair, crutches, traction, and splints to operative treatment. Often, no surgery is performed if the patient is young and has good range of motion. Operative treatment is more common when patients are older, have poor range of motion, or have subluxation of the femoral head.^[12]

The patient in this case was given crutches and instructed not to bear weight on the left lower extremity. Following discharge from the ED, he received a follow-up evaluation by a pediatric orthopedic surgeon and surgical management 4 months later. Coronal reconstruction shows flattening, sclerosis, and early fragmentation of the right femoral head.