Management of pediatric patients with synovial fluid white blood-cell counts of 25,000 to 75,000 cells/mm³ after aspiration of the hip.
BACKGROUND
In this study, we sought to elucidate the presentation, clinical course, treatments pursued, final diagnosis, and risk factors for septic arthritis in a series of children with hip pain and intermediate synovial fluid values (white blood-cell [WBC] counts of 25,000 to 75,000 cells/mm(3) [25 to 75 × 10(9) cells/L]).


METHODS
We reviewed the records of pediatric patients who underwent hip aspiration between 2005 and 2012 at a tertiary-care pediatric hospital. Demographic data, laboratory values, final diagnosis, and treatment details were recorded for the subpopulation of patients with an aspirate WBC count of 25,000 to 75,000 cells/mm(3) (25 to 75 × 10(9) cells/L). Univariate and multivariable logistic regression analysis was used to assess risk factors for septic arthritis of the hip across final diagnostic groups and subgroups with WBC values of <50,000 and ≥50,000 cells/mm(3) (<50 and ≥50 × 10(9) cells/L).


RESULTS
Forty-six children (twenty-seven males and nineteen females) with a mean age of 7.6 years met the inclusion criteria. The final diagnoses were septic arthritis of the hip (n = 15; 33%), Lyme arthritis (n = 13; 28%), transient synovitis (n = 8; 17%), and other findings (n = 10; 22%). Subjects with a synovial fluid WBC count of ≥50,000 cells/mm(3) (≥50 × 10(9) cells/L) were more likely to be diagnosed with septic arthritis of the hip (odds ratio, 4.4; 95% confidence interval, 1.1 to 16.9; p = 0.03). While septic arthritis of the hip was the most common diagnosis (48%) in patients with WBC values of ≥50,000 cells/mm(3) (≥50 × 10(9) cells/L), it also represented 17% of cases with WBC values of <50,000 cells/mm(3) (<50 × 10(9) cells/L).


CONCLUSIONS
Septic arthritis of the hip is the most common ultimate diagnosis in children with synovial fluid WBC values of 25,000 to 75,000 cells/mm(3) (25 to 75 × 10(9) cells/L) following hip aspiration, and it should be high on the differential diagnosis, even in cases with synovial fluid WBC values of <50,000 cells/mm(3) (<50 × 10(9) cells/L).
Department of Orthopedic Surgery, Boston Children's Hospital, 300 Longwood Avenue, Hunnewell 217, Boston MA 02115. E-mail address for B.E. Heyworth: Benton.Heyworth@childrens.harvard.edu.
Benton E
BE
Heyworth
Department of Orthopedic Surgery, Boston Children's Hospital, 300 Longwood Avenue, Hunnewell 217, Boston MA 02115. E-mail address for B.E. Heyworth: Benton.Heyworth@childrens.harvard.edu.
Benjamin J
BJ
Shore
Department of Orthopedic Surgery, Boston Children's Hospital, 1 Autumn Street, Floor 2, Office 229, Boston, MA 02115.
Kyna S
KS
Donohue
Department of Orthopedic Surgery, Boston Children's Hospital, 1 Autumn Street, Floor 2, Office 229, Boston, MA 02115.
Patricia E
PE
Miller
Department of Orthopedic Surgery, Boston Children's Hospital, 300 Longwood Avenue, Hunnewell 217, Boston MA 02115. E-mail address for B.E. Heyworth: Benton.Heyworth@childrens.harvard.edu.
Mininder S
MS
Kocher
Department of Orthopedic Surgery, Boston Children's Hospital, 300 Longwood Avenue, Hunnewell 217, Boston MA 02115. E-mail address for B.E. Heyworth: Benton.Heyworth@childrens.harvard.edu.
Michael P
MP
Glotzbecker
D000293:Adolescent; D018771:Arthralgia / Q000209:etiology / Q000517:prevention & control; D001170:Arthritis, Infectious / Q000150:complications / Q000175:diagnosis / Q000473:pathology* / Q000628:therapy*; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006621:Hip Joint; D006801:Humans; D007223:Infant; D007958:Leukocyte Count; D016015:Logistic Models; D008297:Male; D011379:Prognosis; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000150:complications / Q000175:diagnosis / Q000473:pathology* / Q000628:therapy*; D013396:Suction; D013582:Synovial Fluid / Q000166:cytology*