Checkmark: a sign for the detection of iliopsoas pathology on MRI of the hip.

BACKGROUND

The iliopsoas compartment can be involved in many different disease processes with a wide variety of symptoms that may simulate avascular necrosis (AVN) of the femoral head. The psoas muscle merges with the iliacus to form a checkmark ( radical) shape in the coronal MRI plane, with normal muscle intensities, on both sides of the spine.

PURPOSE

To evaluate whether abnormality of this checkmark shape (obliteration or abnormal intensity), the checkmark sign, can be used as a simple indicator of iliopsoas pathologies on MR examinations performed for suspected AVN of the hip.

MATERIAL AND METHODS

A total of 75 hip MRI examinations performed during 2007 for suspected AVN (male:female ratio, 44:31; average age, 41 years) were retrospectively assessed. The iliopsoas compartment was assessed on the coronal T1 and T2 fat saturated sequences for the presence of the checkmark sign by a consensus of two readers.

RESULTS

Twenty-six patients had signs of AVN and 49 patients had either other hip findings or normal hips. A normal checkmark shape was observed in all but two examinations. Obliteration of the checkmark shape, a positive checkmark sign, in those two was due to psoas compartment pathology (infection and hematoma of the iliopsoas compartment).

CONCLUSION

A positive checkmark sign (abnormal shape or intensity) can serve as a clue for unsuspected iliopsoas pathology when evaluating MRI of the hip in patients with suspected AVN.