• 
• 

Three Part Question

In [children presenting to the Emergency Department with hip pain and limping] is [ultrasonography better than clinical parameters] in [differentiating septic arthritis from other hip conditions]?

Clinical Scenario

A 5 year old boy presents to the Emergency Department with a 2 day history of limp and right hip pain he is afebrile. Is an ultrasound of the hip better at diagnosing septic arthritis than blood investigations (WBC, ESR, CRP)?

Search Strategy

Dialog Datastar interface using specifically:
(CINAHL interface on the World Wide Web 1982 to date
EMBASE database on the World Wide Web 1974 to date
MEDLINE database on the World Wide Web 1950 to date)
[(((ULTRASONOGRAPHY.W..DE.) OR (ultrasound ADJ scan) OR (ULTRASONOGRAPHY-DOPPLER.DE. OR ULTRASONOGRAPHY-DOPPLER-COLOR.DE.) OR (ultrasonography)) AND ((hip) OR (HIP-JOINT.DE.)) AND ((septic ADJ arthritis) OR (ARTHRITIS-INFECTIOUS#.DE.))) AND (LG=EN AND HUMAN=YES AND ( CHILD# OR ADOLESCENT.DE. OR
INFANT# ))]

Search Outcome

There were 42 papers identified using Dialog Datastar of which 4 were relevant. No single paper directly compared USS with blood investigations in the diagnosis of septic arthritis.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Miralles M et al 1989 Spain	500 consecutive children presenting with painful hip or limp	Prospective study	Presence or absence of effusion on USS	261/500 (52%) had negative USS.	Did not look at clinical parameters. So of 7 cases septic arthritis 4 had abnormal USS, so sens was 4/7 (57%).
				235/500 (47%) had positive USS.
				7/500 (1.4%) had septic arthritis.
				3/500 (0.6%) had abnormal USS and XR.
				1/500 (0.2%) had abnormal USS and normal XR.
Zawin J et al. 1993 USA	90 consecutive children presenting with limp	Prospective study	USS diagnosis and aspiration result	40/96 (42%) had negative USS of which 3 (7.5%) were diagnosed as ostelomyelitis and 0 septic arthiritis	Small numbers leading to high incidence of septic arthritis probably due to selection bias. Sensitivity for septic arthritis was 100%, but specificity was poor.
				56/96 (58%) had positive USS of which 15 (26.7%) were septic arthritis.
Fink AM et al. 1995 UK	50 consecutive patients aged 1 to 10 years presenting to the Emergency Department with acute hip pain.	Prospective study	Presence or absence of septic arthritis and hip effusion on USS.	36/50 (72%) had detectable effusions and were aspirated.	Small numbers, only 1 diagnosed septic joint, which had a detectable effusion on USS giving USS a sensitivity of 100% according to the study.
				35/36 (97%) of effusions showed no organisms on microscopy and remained sterile after 5 days.
				1/50 (2%) had septic arthritis with WBC 20.4x109/l and ESR 30 mm/h.
Gordon JE 2002 USA	All children with hip pain presenting during a 18 month period.	Prospective cohort study.	Presence or absence of hip effusion on USS and cause of effusion.	Of 132 patients, 80 had USS.	Population different to our ED population. Not all patients underwent USS, may be workup bias.
				Of 22 SA, 18/80 (22.5%) had positive USS.
				4/80 (5%) had septic arthritis but negative USS.

Comment(s)

There is a paucity of evidence that directly looks at this question. Some studies (Fink et al, Zawin et al) suggest that USS has an excellent sensitivity for detecting septic arthritis although other studies show a significant false negative rate (Miralles et al).

Editor Comment

RB

Clinical Bottom Line

Based on the current available clinical evidence few recommendations can be made regarding routine use of USS in limping children. Perhaps using clinical and biochemical markers to identify high risk patients will allow focused use of ultrasonography. The question also remains as the best management of children with abnormal bioclinical markers but a normal USS scan.

References

1. Miralles M, Gonzalez G, Pulpeiro JR et al. Sonography of the painful hip in children: 500 consecutive cases American Journal Roenterology 1989;152(3);579-82.
2. Zawin JK, Hoffer FA, Rand FF et al. Joint effusion in children with an irritable hip: US diagnosis and aspiration. Radiology 1993;187(2);459-63.
3. Fink AM, Berman L, Edwards D et al. The irritable hip: immediate ultrasound guided aspiration and prevention of hospital admission. Archives of Disease in Childhood 1995;72(2);110-3.
4. Gordon JE, Huang M, Dobbs M, Luhmann SJ et al. Causes of false-negative ultrasound scans in the diagnosis of septic arthritis of the hip in children. Journal of Pediatric Orthopedics 2002;22(3);312-6.