Iliopsoas snapping hip: improving the diagnostic value of magnetic resonance imaging with a novel parameter.

OBJECTIVE

To illustrate an advanced imaging parameter that describes the course of the iliopsoas tendon, and evaluate its correlations with iliopsoas internal hip snapping syndrome.

METHODS

This retrospective cohort study reviewed hip MRI images of all patients seen by a single surgeon between January 2015 and March 2016. The comparison group included all patients with clinical internal hip snapping, versus the control group that did not. MRI images were processed using minimum intensity projection. Measurements obtained of the pelvis and course of the iliopsoas tendon included: pelvic incidence, coronal angle, and sagittal opening angle (SOA). Comparison of measurements between the groups was performed with Mann-Whitney U analysis and receiver operator curve (ROC) plotting, with a significance cutoff of p = 0.05.

RESULTS

The control group (n = 85) and comparison group (n = 48) demonstrated no difference in age or gender. Pelvic incidence was similar [51.3 (± 10.7) degrees control versus 52.2 (± 7.7) degrees comparison (p = 0.36)], as was coronal angle [13.9 (± 4.6) degrees control versus 14.8 (±4.8) degrees comparison (p = 0.15)]. There was a significant difference in SOA [137.0 (± 5.9) degrees control versus 141.9 (± 6.5) degrees comparison (p < 0.01)]. ROC analysis revealed SOA threshold of 140 degrees for clinical IP hip snapping (p < 0.01), with odds ratio 5.2 (2.4-11.3) for SOA > 140 degrees.

CONCLUSIONS

Iliopsoas hip snapping is often part of a more complex disease process. While challenging to diagnose, advanced imaging parameters, like the sagittal opening angle, relate with clinical pathology. The SOA offers diagnostic value, with a threshold of greater than 140 degrees significantly correlating with clinical presentation.