Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Hip Transient Synovitis

Basics
Description
  • Transient synovitis is characterized by the acute onset of monarticular hip pain, limp, and restricted hip motion.
  • It must be distinguished from septic arthritis.
  • Gradual but complete resolution over several days to weeks is the norm.
  • Synonyms: Toxic synovitis; Irritable hip
Epidemiology
  • Transient synovitis is the most common cause of hip pain in children.
  • It is a diagnosis of exclusion.
  • Transient synovitis of the hip can occur from 9 months of age to adolescence; most cases occur in children 3-8 years old.
  • The risk of a child having at least 1 episode of transient synovitis of the hip is 1-3%.
    • This risk is 3 times greater in patients with a stocky or obese physique.
  • Right and left involvement is essentially equal; concurrent bilateral involvement has not been reported.
  • Male:Female ratio is 2:1.
Incidence
  • Transient synovitis accounts for 0.5% of annual pediatric orthopaedic admissions.
  • The incidence is much lower among African Americans.
Risk Factors
  • Male gender
  • Upper respiratory infection or other active infection
Genetics
This condition is not genetic.
 
Etiology
  • The true cause is unknown; it appears to be an immune-mediated inflammation, not an infection.
  • It has been proposed that transient synovitis of the hip may be associated with active infection elsewhere, trauma, or allergic hypersensitivity.
  • Nonspecific upper respiratory infection, pharyngitis, and otitis media have been associated with the occurrence of transient synovitis in as many as 70% of cases.
  • An association is noted with minor trauma in up to 30%, and with allergic predisposition in up to 25%.
Associated Conditions
Legg-Calve-Perthes disease (~1.5%)
 
Diagnosis
Signs and Symptoms
  • An acute onset of unilateral hip pain occurs in an otherwise healthy child.
  • Pain usually is confined to the ipsilateral groin and hip area, but it may present as anterior thigh and knee pain.
  • Limp and antalgic gait are common, with some patients refusing to bear weight on the involved extremity.
  • The hip is held in a flexed and externally rotated position and has restricted ROM.
  • The patient may have a low-grade fever.
  • Laboratory values are nonspecific and are often within normal limits.
Physical Exam
  • The patient usually indicates unilateral hip pain confined to the ipsilateral groin, anterior thigh, or knee.
  • ROM often is decreased and painful.
  • The patient does not have as much pain as a patient with a septic hip.
    • If the hip ROM is tested slowly, it is usually at least 50% of normal.
  • While walking, patients often display a limp or an antalgic gait; some children refuse to walk.
  • Ipsilateral muscle atrophy is seen rarely, but when present, it implies a longstanding duration of symptoms, and a diagnosis other than transient synovitis should be considered.
Tests
Lab
  • Results are usually nonspecific and within normal limits, but they may help to rule out other diagnoses.
    • The peripheral white blood cell count is normal to slightly elevated.
    • The ESR averages 20 mm/hour but may be slightly higher.
    • Urinalysis, blood culture, rheumatoid factor, and Lyme titers and tuberculin skin test results are usually within normal limits.
    • Analysis of joint fluid for complement levels or other tests has been nonspecific.
Imaging
  • Radiography:
    • Plain films of the hip should include AP and lateral views.
  • In transient synovitis, these films are normal but may help rule out other diagnoses, such as Legg-Calve-Perthes disease and SCFE.
  • Ultrasound may be useful to determine if an effusion exists, and to guide aspiration, if infection cannot be ruled out clinically.
  • MRI is needed only in cases of persistent pain, when infection has been excluded.
  • A bone scan often is not helpful because this condition is not a bony process.
Pathological Findings
  • Biopsy specimens have shown synovial hypertrophy secondary to nonspecific, nonpyogenic inflammatory reaction.
  • Hip joint aspirates have shown a culture-negative synovial effusion, usually 1-5 mL.
Differential Diagnosis
  • Transient synovitis of the hip is a diagnosis of exclusion.
  • Conditions to rule out include:
    • Pyogenic arthritis
    • Osteomyelitis in the adjacent femoral neck or pelvis
    • Tuberculous arthritis
    • Psoas abscess
    • Other muscle infection about the hip
    • Juvenile rheumatoid arthritis
    • Acute rheumatic fever
    • Legg-Calve-Perthes disease
    • Tumor
    • SCFE
    • Dislocation
    • SI joint infection
Treatment
General Measures
  • Transient synovitis usually has a limited duration of symptoms, averaging <7 days.
    • Most studies report complete resolution of all signs and symptoms with no immediate residual clinical or radiographic abnormalities.
    • Long-term studies have shown mild radiographic changes in the involved hip.
  • Traction and routine joint aspiration are not always needed.
    • If traction is used, it is to promote rest and comfort.
    • The hip should be in ~30° of flexion to avoid increasing intra-articular pressure.
  • The important point in management of this condition is to establish the diagnosis: Pyogenic arthritis must be excluded, on clinical grounds or with laboratory tests.
  • Treatment is directed at rapidly resolving the underlying inflammatory synovitis with its symptoms.
Activity
  • Bed rest until initial acute pain resolves
  • Weightbearing after pain resolves and full ROM returns, followed by a period of refraining from strenuous activities
Special Therapy
Physical Therapy
  • Usually not necessary
  • Parents can moderate child’s activity adequately.
Medication
First Line
  • Anti-inflammatory drugs:
    • Some experts believe these medications should be withheld to avoid masking an infection, but others believe they may have diagnostic value in speeding the natural resolution of inflammatory symptoms.
Follow-up
Prognosis
The prognosis is good because transient synovitis is self-limiting, without any clinically significant sequelae.
 
Complications
  • 1 study has reported that Legg-Calve-Perthes disease or AVN of the femoral head may develop several months after an episode of transient synovitis of the hip.
    • This finding probably represents a delay in establishing the correct diagnosis.
Patient Monitoring
  • A physician should be available for re-evaluation at all times until the possibility of infection is excluded.
  • The child should be re-examined in ~1-2 weeks to determine return of motion before resuming full weightbearing and normal activity.
  • Parents should bring the child back if symptoms recur or increase.
Miscellaneous
Codes
ICD9-CM
727.0 Synovitis
 
Patient Teaching
  • Transient hip synovitis is a self-limiting process without major consequences.
  • Some authorities have suggested an increased incidence of later Legg-Calve-Perthes disease in such patients, but this finding has not been proven conclusively.
FAQ
Q: Do all patients with transient synovitis require aspiration of the hip?
A: No. Although the essence of management is to rule out infection, in many cases this goal can be accomplished clinically by noting that transient synovitis involves a more mild degree of guarding, more mild elevation of infection and inflammatory markers. Most often, patients with transient synovitis will be able to bear some weight on the involved side.
 
Q: If aspiration is needed to rule out infection, where and how should it be done?
A: Aspiration requires sedation. It should be done with imaging (ultrasound or fluoroscopy) to be certain that the aspirate is from the hip joint. A radiologist or orthopaedic surgeon may perform this procedure. Anterior, medial, or lateral approaches are used. Fluid should be sent for cell count with differential and culture.

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