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Three Part Question

In [a child with an irritable hip] is [x-ray better than ultrasonography] at [detecting a hip effusion]?

Clinical Scenario

A 3 year old child presents to the Emergency Department with recent onset of left-sided limp and no history of trauma. He is apyrexial, systemically well with a normal white cell count and ESR. You diagnose irritable hip and wonder whether x-ray or ultrasonography is better at detecting a joint effusion.

Search Strategy

Medline 1966-10/99 using the OVID interface.
[({exp Hip joint OR exp hip OR hip$.mp} AND {exp pain OR pain$.mp OR irritable$.mp OR limp$.mp OR exp synovitis OR synovitis.mp}) AND {exp pediatric OR pediatric$.mp OR paediatric.mp OR child$] AND {exp ultrasonography OR ultrasound$.mp} LIMIT to human AND english.

Search Outcome

52 papers found of which 46 irrelevant or of insufficient quality for inclusion. The six remaining papers are shown in the table.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Adam R et al, 1986, UK	87 children with irritable hip	Diagnostic	Detection of effusions	28 of 47 children with an effusion on ultrasound had x-ray abnormalities	No universal gold standard
Rosenborg M and Mortensson W, 1986, Sweden	58 examinations of 47 children, 40 of whom had acute unilateral transient synovitis of the hip	Diagnostic	Detection of effusions	43% of 23 children with an effusion on ultrasound had iliopsoas fatty layer sign on plain x-ray, while 52% had and abnormal capsular fat pad sign.	No universal gold standard
Zieger MM et al, 1987, Germany	123 consecutive patients with suspected joint effusions	Diagnostic	Detection of effusions	USS 100% sensitive	No universal gold standard
Miralles M et al, 1989, Spain	500 children with a painful hip or a limp	Diagnostic	Detection of effusions	58 of 235 patients with effusions on ultrasound had abnormal x-rays. 4 patients with normal ultrasounds had abnormal x-rays.	No universal gold standard
			Change in clinical care	USS detection of effusion changed clinical care in only 6 cases
Bickerstaff DR et al, 1990, UK	111 children with acute hip pain	Diagnostic	Change in clinical care	X-ray changed clinical care in only 2 cases (children with Perthes' disease)	No universal gold standard
			Detection of effusions	Effusion detected in 71% by USS but only in 15% by x-ray.
Terjesen T and Osthus P, 1991, Norway	59 children with acute synovitis of the hip.	Diagnostic	Detection of effusions	Effusions detected in all patients by USS, but in none by x-ray.	No universal gold standard

Comment(s)

In all the studies found, USS was its own gold standard for the detection of hip effusions. Therefore no comment about the sensitivity or specificity of USS itself can be made. X-ray is, however, clearly less sensitive than USS at detecting hip effusions. The role of x-ray in detecting Perthes' disease should not be forgotten.

Clinical Bottom Line

Ultrasound is more sensitive than plain x-ray at detecting hip effusions in children. It should be the first imaging investigation of the irritable hip.

Level of Evidence

Level 2 - Studies considered were neither 1 or 3.

References

1. Adam R, Hendry GM, Wild SR et al. Arthrosonography of the irritable hip in childhood: a review of 1 year's experience. Br J Radiol 1986;59(699):205-8.
2. Rosenborg M and Mortensson W. The validity of radiographic assessment of childhood transient synovitis of the hip. Acta Radiologica: Diagnosis 1986;27(1):85-9.
3. Zieger MM, Dorr U, Schulz RD. Ultrasonography of hip joint effusions. Skeletal Radiology 1987;16(8):607-11.
4. Miralles M, Gonzalez G, Pulpeiro JR et al. Sonography of the painful hip in children: 500 consecutive cases. Am J Roentgenology 1989;152(3):579-82.
5. Bickerstaff DR, Neal LM, Booth AJ et al. Ultrasound examination of the irritable hip. JBJS (Br) 1990;72(4):549-53.
6. Terjesen T and Osthus P. Ultrasound in the diagnosis and follow-up of transient synovitis of the hip. J Pediatr Orthop 1991;11(5):608-13.