Transient Synovitis Case File

Transient Synovitis Case File

Eugene C. Toy, MD, Barry C. Simon, MD, Terrence H. Liu, MD, MHP, Katrin Y. Takenaka, MD, Adam J. Rosh, MD, MS

Case 33

A 6-year-old boy presents to the emergency department (ED) with his parents complaining of a limp for 3 days. The limp began following a fall from a playground structure, and has worsened to the point that the child is no longer willing to walk. The patient was treated two weeks ago for an acute otitis media with Augmentin, and he currently has a runny nose attributed to allergies. There have been no fevers, emesis, cough, abdominal pain, recent travel or insect bites.

His blood pressure is 95/68 mm Hg, pulse is 102 beats per minute, respirations are 20 breaths per minute, and temperature is 37.5°C (99.5°F). On physical examination, he is well appearing and his right hip is noted to be flexed with slight abduction and external rotation. The joint is warm to touch, and he resists passive range of motion testing. The right knee is normal, and there are no other findings on physical examination.

⯈ What is your next step?

⯈ What is the most likely diagnosis?

⯈ What is the best treatment for this problem?

ANSWER TO CASE 33:

Transient Synovitis

Summary: The patient is a 6-year-old boy with right hip pain who is refusing to ambulate. He appears well with normal vital signs; his examination reveals decreased passive range of motion of the right hip.

• Next step: Perform an ultrasound to evaluate for hip effusion, consider an arthrocentesis to evaluate synovial fluid.
• Most likely diagnosis: While it is essential to consider the serious etiologies of pediatric hip pain, this child most likely has transient synovitis (TS).
• Best treatment for this problem: After excluding septic arthritis, osteomyelitis and other non-benign etiologies, treat for transient synovitis with NSAIDs and bed rest for 7 to 10 days.

ANALYSIS

Objectives

1. Recognize the clinical presentation of transient synovitis, and appreciate the similarities of its presentation to septic arthritis and other serious pathologies of limp.
2. Learn about the diagnosis and treatment of suspected septic arthritis.
3. Be familiar with the other etiologies of limp in a child.

Considerations

Transient synovitis is the most common cause of acute hip pain in children aged 3 to 10 years old. The arthralgia is caused by a temporary inflammation of the synovium, the soft tissue that lines the non-cartilaginous surfaces of the hip joint. While the etiology is not clearly understood, the disease is suspected to be secondary to an infection as up to 50% of patients report a recent upper respiratory tract infection. Fever typically is absent but may occur. Most patients will complain of unilateral hip pain, and up to 5% will have bilateral pain. There is a male-to-female predominance of slightly more than 2:1.

While this case is a typical example of transient synovitis, the diagnosis not to miss is septic arthritis, an infection that can lead to rapid destruction of the articular joint cartilage. This disease can lead to long-term morbidity if not diagnosed early, and joints of the lower extremity are affected in more than 90% of the cases.

In general, children with septic arthritis will have a history of fever, malaise and/or anorexia within the week prior to presentation. Occasionally, the presentation is more subtle, and the symptoms may be attenuated by recent antibiotic use. Neonates and infants with septic arthritis may present with irritability, poor feeding, and pseudoparalysis of the affected limb

On physical examination, the position of comfort will be with the hip flexed, abducted, and externally rotated. Passive range of motion exercises will be resisted and painful. Appropriate initial laboratory studies include complete blood count (CBC), blood cultures, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Plain radiographs are key to rule out obvious alternative diagnoses, and bedside ED ultrasound may identify a hip effusion. The definitive diagnosis of septic arthritis is made by examination of synovial fluid obtained by arthrocentesis.

Approximately 3% of children who present to the emergency department for limp will have septic arthritis. Causative bacterial organisms vary with age group, but Staphylococcus aureus is the most common organism, followed by Group A Streptococcus (S pyogenes) and S pneumoniae. Kingella kingae has recently become a common pathogen in children younger than 3, and Neisseria gonorrhoeae should be considered in neonates and sexually active adolescents. Empiric antibiotic coverage should include an antistaphylococcal agent with gram-negative coverage added when age appropriate. Definitive treatment is by immediate surgical drainage and washout in addition to antibiotics.

Approach To:

Child With a Limp

DEFINITIONS

LIMP: A limp is an uneven, jerky or laborious gait, usually caused by pain, weakness, or deformity.

CLINICAL APPROACH

The differential diagnosis of the pediatric limp is broad, and the emergency physician must use a systemic approach to identify or exclude the conditions that require emergent treatment. The cause of limp can often be determined through careful history taking and physical examination. Laboratory tests, imaging and diagnostic testing can then be applied to confirm clinical suspicions.

Obtaining a History

History taking is challenging in a young child who may be unable to communicate verbally, or have difficulty localizing the site of the pain. Obtaining the following information will help to narrow the differential.

1. Age (age specific diagnoses)
2. Onset of pain (acute versus chronic)
3. Duration of pain (intermittent, constant, or worse at particular times of day)
4. Location of pain (bone, joint, soft tissue, neurologic or intra-abdominal)
5. Preceding events (history of trauma, recent viral illness or antibiotic use)
6. Constitutional symptoms (fever, malaise, weight loss)

There is overlap among age groups, but knowing which diseases are common in each age group is a good place to start when making a list of potential diagnoses (Table 33–1).

Limps that are acute in onset are more likely to be due to trauma or infection. Chronic limps are suggestive of systemic illness, Legg-Calve-Perthes disease (LCP) (avascular necrosis), or slipped capital femoral epiphysis (SCFE). Pain that is worse at night is more typical of a malignancy, and morning stiffness is commonly associated with juvenile rheumatoid arthritis. The location of the pain may be typical of a musculoskeletal etiology, but referred pain and alternative diagnoses such as appendicitis, and testicular or ovarian torsion should be entertained. A history of trauma can suggest fracture or contusion, while a recent illness or constitutional symptoms may direct the physician to consider osteomyelitis, septic arthritis, or transient synovitis.

Physical Examination

First, the gait should be observed if the child is ambulatory. The child should be fully undressed, vital signs reviewed, and the general appearance of “sick or not sick” considered. The extremities should be inspected for skin erythema, rash, tenderness, deformity, muscle atrophy and abnormal range of motion. The log roll test is particularly useful in evaluating hip rotation. To perform the log roll test, the leg is straightened, and the foot is manipulated medially (internal rotation of the hip) and laterally (external rotation of the hip). Pain with this maneuver suggests inflammation, infection, or trauma.

The presence or absence of a fever has not been found to be helpful in making a definitive diagnosis. In a series of 95 children with septic arthritis, most had a lowgrade fever, but one-third were afebrile at presentation. Absence of fever should not sway the clinician from the diagnosis.

Lastly, if there are any inconsistencies between the history and physical examination, the possibility of non-accidental trauma, or child abuse, must be explored.

Laboratory Studies

Laboratory studies are not routinely indicated in a child who has normal vital signs, appears well, and has a history consistent with an immediate preceding trauma. However, a complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and blood cultures are useful if entities such as osteomyelitis, neoplasm, septic arthritis, and transient synovitis remain on the differential.

Synovial fluid analysis, which includes cell count, Gram stain, culture and sensitivity testing, may be required to distinguish between septic arthritis and transient synovitis. A synovial fluid white blood cell count of >50,000 cells/μL with a predominance (>90%) of polymorphonuclear (PMN) leukocytes suggests septic arthritis. The Gram stain may rapidly identify the organism, and the culture and sensitivity results will allow the antibiotic regimen to be narrowed. Notably, synovial fluid has bacteriostatic effects, and organisms may not grow in the routine culture. The likelihood of identifying the organism can be improved by placing a synovial fluid sample in a blood culture medium. Finally, neonates and adolescents with a suspected septic arthritis should be tested for gonorrhea.

Imaging Studies

In contrast to laboratory studies, most children with a limp require radiographic evaluation. Plain films should be ordered with a minimum of two views and the joints above and below the area of concern should be included. If possible, weightbearing views should be obtained, and if the hip is involved, the contralateral hip should be filmed for comparison. Radiographs can identify fracture, late avascular necrosis, soft tissue swelling, and destructive bony lesions.

A bone scan uses IV technetium 99m-labeled methylene diphosphate to identify areas of increased cellular activity and blood flow. This test can be useful to detect early Legg-Calve-Perthes disease, osteomyelitis, stress fractures, and osteoid osteomas. Magnetic resonance imaging (MRI) can be helpful in detecting osteomyelitis, early avascular necrosis, and bone malignancies. Computed tomography (CT) is rarely indicated for musculoskeletal complaints; however the test may be necessary when intra-abdominal entities, such as appendicitis, or pelvic etiologies are in the differential.

Ultrasound (US) is perhaps the most useful imaging study after plain films in the evaluation of the pediatric limp. Recent studies have demonstrated that the use of bedside ED ultrasound can reliably detect a joint effusion (Figure 33–1). In one series of 96 children who underwent hip US for possible septic arthritis, none of the 40 patients who had normal US findings were later discharged with the diagnosis of septic arthritis. Early detection of a joint effusion and ultrasound guidance of arthrocentesis can decrease the time to definitive diagnosis and treatment

Figure 33–1. Ultrasound demonstrating a left hip effusion. The right hip is normal. The echogenic linear focus which courses along the left femoral neck is felt to represent periosteal new bone. An effusion is diagnosed when the distance between the anterior surface of the femoral neck and the posterior surface of the iliopsoas muscle is greater than 5 mm, or there is a greater than 2 mm difference from the contralateral hip. FH, femoral head; ASFN, anterior surface femoral head; PSIM, posterior surface iliopsoas muscle.

of septic arthritis. Additionally, the detection of bilateral hip effusions raises the clinical suspicion for rheumatologic conditions and transient synovitis. One study showed that up to 25% of patients with transient synovitis have bilateral effusions.

Alternate Etiologies of Pediatric Limp

Septic Arthritis is most common in children <3 years old. The male-to-female ratio is 2:1. The hip is the most common site (80%) with the most common organism being S aureus. Others: group A beta-hemolytic Streptococcus, S pneumoniae, Haemophilus influenzea type B, Kingella kingae (after URI), Salmonella (sickle cell patients), Pseudomonas aeruginosa, Neisseria meningitidis, N gonorrhoeae, gramnegative bacilli. Pain in the affected joint, fever, edema, swelling, inability to bear weight, anorexia, irritability, pseudoparalysis may be presenting symptoms. There are no published clinical decision rules but a recent study notes that infection is indicated by: (1) inability to bear weight, (2) fever, (3) ESR >40 mm/h, (4) WBC >12,000/mm³. Though the incidence is low, when present, IV antibiotics and surgical irrigation and debridement must be implemented immediately as disability due to destruction of joint tissue may ensue.

Osteomyelitis of the femur or pelvis can present as hip pain. The proximal femur is the most common site of bone infection in children, and may also involve the joint given the intracapular location (Figure 33–2). On examination, there may be focal erythema, swelling, and warmth near the location of the metaphysis. Similar to septic arthritis, the presentation may be attenuated by the recent antibiotic use. Plain films may not show bony changes until 10 to 20 days after symptoms began. MRI is the ideal study with a sensitivity of 92% to 100%. The most common organisms are the same as those that cause septic arthritis, and patients with osteomyelitis require empiric antibiotic therapy and emergent orthopedic consultation for bone aspiration.

Figure 33–2. An example of osteomyelitis of the left proximal femur, ischia, and iliac bones with associated left hip septic arthritis. There is also extensive myositis surrounding the left hip. There is possible pus under pressure or necrotic changes may be present in the left proximal femur.

Legg-Calve-Perthes disease (vascular necrosis of the femoral head) develops when an insufficient blood supply to the femoral head leads to necrosis. It is commonly found in boys aged 4 to 10 years, and its cause is unknown. The child usually presents with a limp and may complain of hip or knee pain. On physical examination, the child will have decreased range of motion at the affected hip. X-rays may show fragmentation and then healing of the femoral head (Figure 33–3), and a bone scan will show decreased blood perfusion to the femoral head. Ten to twenty percent of patients will have bilateral disease, and the aim of treatment is to keep the femoral head within the acetabulum to allow healing to occur. A brace, cast, or splint may be required to immobilize the hip’s position. Patients should be referred to an orthopedist for possible surgical management.

Slipped Capital Femoral Epiphysis (SCFE) remains one of the most common disorders affecting the hip in adolescence. SCFE is characterized by the posterior displacement of the capital femoral epiphysis from the femoral neck through the growth plate. It is most common in obese boys aged 11 to 15 years. Children who grow rapidly and who have hormonal imbalances such as hypothyroidism and acromegaly are also at risk. In addition to a limp, patients will complain of hip and/ or knee pain. On examination, patients will have impaired internal rotation and passive hip flexion may be associated with compensatory external rotation. Plain films of the hip or pelvis will often show displacement of the femoral head, commonly described as “fallen ice cream from the cone”. Approximately 30% to 60%

Figure 33–3. Avascular Necrosis of the Femoral Head

of patients with unilateral SCFE will eventually have SCFE of the contralateral hip. Once the diagnosis is suspected, weight-bearing should be avoided and most patients will require surgery to reattach the femoral head to the femur.

Toddler’s fracture is a nondisplaced fracture of the distal tibial shaft that occurs most commonly in a child younger than 2 years who is learning to walk. Frequently, there is no definite history of a traumatic event, and the child is brought to the office due to reluctance to bear weight on the leg. On physical examination, maximal tenderness can usually be elicited over the fracture site. On plain film, the typical findings are a nondisplaced hairline spiral fracture of the tibia and no fibular fracture. It is not uncommon for initial radiographs to be normal and the diagnosis of this fracture made several days after the injury when follow-up radiographs show a lucent line or periosteal reaction.

Osgood-Schlatter syndrome is caused by a reaction of the bone and cartilage of the tibial tubercle to repetitive stress (eg, jumping) and is believed to represent tiny stress fractures in the apophysis. The condition is also associated with rapid growth spurts. Physical examination reveals tenderness and swelling over the tibial tubercle. Running, jumping, and kneeling worsen the symptoms. The condition is managed with ice, anti-inflammatory medication, and a decrease in activity. Daily stretching of the quadriceps and hamstrings is also beneficial. Patients with severe pain may require immobilization using crutches or a knee immobilizer. Individual regulation of activity is usually effective; pain may recur until the tubercle matures (ie, ossifies completely).

COMPREHENSION QUESTIONS

33.1 A 2-year-old girl presents with refusal bear weight on the left leg and a fever to 38.7°C (101.6°F) for 2 days. She has significant guarding when you attempt to range her left hip. In consideration of the differential diagnosis, which of the following diagnostic tests would be most useful?

A. Radiograph of both hips

B. Complete blood count

C. Blood culture

D. Ultrasound examination of the hip

33.2 The mother of an 8-year-old boy is told that her son’s limping and knee pain is caused by Legg-Calve-Perthes disease. Which of the following best explains the condition of the femoral head?

A. Dislocation

B. Subluxation

C. Avascular necrosis

D. Dysplasia

33.3 A 5-year-old girl is brought into the emergency center due to significant hip pain. There is no history of trauma or fall. She has had a recent respiratory infection. Which of the following is the most likely diagnosis?

A. Subacute osteomyelitis

B. Transient synovitis

C. Developmental dysplasia of the hip

D. Malignant degeneration of the hip

E. Slipped capital femoral epiphysis

33.4 A 13-year-old overweight adolescent boy presents to his pediatrician’s office with chronic left hip pain for 2 months. He has a Trendelenburg gait and has decreased range of motion of the left hip. Which of the following is the most likely diagnosis for this patient?

A. Slipped capital femoral epiphysis

B. Transient synovitis

C. Osgood-Schlatter

D. Legg-Calve-Perthes disease

33.5 A12-month-old male infant presents with his concerned mother after rolling off the bed in the night. X-ray reveals a femoral shaft fracture, and you note that this child has had three other visits to the emergency department for injury. What is your next step in management of this patient?

A. Urgent orthopedic consultation

B. Order a skeletal survey

C. Report your concerns to the appropriate child protection services

D. All of the above

ANSWERS

33.1 D. Osteomyelitis, septic arthritis, and transient synovitis should be considered in the differential of this child. Osteomyelitis and a septic arthritis are orthopedic emergencies, which require prompt intervention. Transient synovitis is often hard to distinguish clinically from the prior two entities. To make a definite diagnosis, an ultrasound should be performed to evaluate for an effusion and guide arthrocentesis. The synovial fluid of a septic joint will have a marked neutrophilia.

33.2 C. Legg-Calve-Perthes disease is commonly found in boys aged 4 to 8 years. It results in avascular necrosis of the femoral head.

33.3 B. Transient synovitis is the most common cause of hip pain in children aged 3 to 10 years. Though a benign process, it is often hard to distinguish from a septic joint or osteomyelitis. The child can be safely treated with bed rest and anti-inflammatories.

33.4 A. SCFE is commonly found among overweight pubertal children. A Trendelenburg gait is described as the pelvis tilting downward on the unaffected side when a patient steps on the affected side. There is also an accompanying subtle shift of the torso. Legg-Calve-Perthes is in the differential but more common among children aged 4 to 8. Transient synovitis presents more acutely. Osgood-Schlatter usually presents in athletic kids who have reproducible tibial tubercle tenderness.

33.5 D. Child abuse should be suspected as this is likely to be a non-ambulatory child. The mechanism sounds suspicious, was not witnessed, and there may have been delay in seeking medical care. Treating the injury, alerting the appropriate authorities of your concerns, and obtaining a skeletal survey is essential for the safety of the child. A typical skeletal survey includes skull, chest, pelvis, and entire limb x-rays.

CLINICAL PEARLS

⯈ Always order an ultrasound and perform arthrocentesis in a child with fever who refuses to move a joint. Transient synovitis should be a diagnosis of exclusion.

⯈ Consider Legg-Calve-Perthes disease in boys aged 4 to 8 who present with a limp as it requires a high index of suspicion.

⯈ SCFE treatment is operative and 30% to 60% will eventually have bilateral disease. To prevent delay in diagnosis of the second slip, all patients should be followed closely by an orthopedist until the child has finished growing.

⯈ Perform a thorough history (with and without the parent) and physical on children who present with fractures to evaluate for possible child abuse.

References

Clark MC: Approach to the child with a limp. Available at: www.uptodate.com. Accessed: June 8, 2010. 

Frank G, Mahoney HM, Eppes SC. Musculoskeletal infections in children. Pediatr Clin North Am. 2005;52:1083. 

Kiang KM, Ogunmodede F, Juni BA, et al. Outbreak of osteomyelitis/septic arthritis caused by kigella kingae among child care center attendees. Pediatrics. 2005;116:e206. 

Kienstra AJ; Macias CG: Slipped capital femoral epiphysis. Available at: www.uptodate.com. Accessed: May 9, 2012. 

Kocher MS. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am. 2004;86A:1629. 

Krogstad P: Bacterial arthritis: Clinical features and diagnosis in infants and children. Available at: www.uptodate.com. 

Nelson JD. Skeletal infections in children. Adv Pediatr Infect Dis. 1991;6:59. 

Nigrovic PA: Overview of hip pain in childhood. Available at: www.uptodate.com. Accessed: April 16, 2012. 

Shetty AK, Gedalia A. Septic arthritis in children. Rheum Dis Clin North Am. 1998;24:287. 

Sonnen GM, Henry NK. Pediatric bone and joint infections: Diagnosis and antimicrobial management. Pediatr Clin North Am. 1996;43:933-947. 

Viera RL, Levy JA. Bedside ultrasonography to identify hip effusions in pediatric patients. Ann Emerg Med. 2010;55:284.

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