Magnetic resonance imaging and radiographic assessment of carpal depressions in children with juvenile idiopathic arthritis: normal variants or erosions?

OBJECTIVE

Magnetic resonance imaging (MRI) is playing an increasingly important role in the diagnosis and followup of juvenile idiopathic arthritis (JIA). Carpal depressions are commonly observed in healthy children and in patients with JIA. The aim of our study was to further characterize these depressions in patients with JIA.

METHODS

A total of 29 MRI wrist examinations were analyzed. Depressions were classified according to morphology as either tubular or focal. Features including the presence of a vessel related to the depression, evidence of synovitis, bone marrow edema, or loss of joint space on a radiograph taken on the same day were recorded for each depression.

RESULTS

A total of 173 depressions were identified in 145 carpal bones. Forty percent were capitate depressions. A third were focal depressions and two-thirds were tubular. About 10% of tubular depressions and 30% of focal depressions were associated with features suggesting true erosions, with the remainder likely to represent vascular channels and normal variants.

CONCLUSION

Radiologists and clinicians should undertake caution when assessing carpal depressions on MRI because the vast majority are likely to represent normal variants.