Protrusio acetabuli in juvenile rheumatoid arthritis.

Acetabular protrusion (PA) as measured by a line crossing method was studied in 73 patients with juvenile rheumatoid arthritis (JRA) and its frequency found to be 12% (9/73), presenting bilaterally in 5 cases and unilaterally in 4. All patients had some other forms of radiological damage and the presence of PA was predominantly observed in the JRA group with greater age at onset (8 vs 4.2 years; p < 0.001) and lower frequency of extraarticular manifestations (22% vs 72%; p < 0.01). There was no correlation with type of JRA onset, course of disease, sex, disease duration, seropositivity for rheumatoid factor, and prior steroid intake.