Imaging Modalities for Recurrent Hip Arthroplasty Dislocation

Introduction to Imaging Guidelines

The American College of Radiology recommends CT without IV contrast for evaluating recurrent dislocation of hip arthroplasty, as it provides superior assessment of joint congruence, component positioning, intraarticular fragments, and acetabular fractures that may contribute to instability 1, 2, 3

Standard hip/pelvis radiographs should be used to assess component position, orientation, and obvious mechanical causes of instability, although radiographs alone are insufficient for comprehensive evaluation 4
Radiographs are essential for initial screening but should be followed by CT without IV contrast when radiographs are negative or indeterminate but clinical suspicion for mechanical instability persists 1, 2, 3

CT without IV contrast is the preferred imaging modality for evaluating mechanical causes of recurrent dislocation, including joint congruence, component positioning, intraarticular fracture fragments, and acetabular wall fractures requiring surgical management 1, 2, 3
CT has 87.3% sensitivity for detecting intraarticular fracture fragments, and advanced CT modeling techniques can identify impingement mechanisms responsible for instability 1, 2, 3

MRI without IV contrast is indicated when soft tissue pathology is suspected as the cause of instability, such as abductor tendon tears or muscle injuries compromising hip stability 1, 2, 3
MRI is superior for evaluating soft tissue envelope integrity, ligamentous damage, and tendon or muscle injuries, but has insufficient evidence as initial imaging for non-metal-on-metal prostheses 1, 2, 3, 4

The American College of Radiology specifically recommends CT without IV contrast for post-reduction evaluation to detect complications that increase the risk of recurrent dislocation, with no evidence supporting the use of CT with IV contrast 1, 2, 3
Contrast adds cost and risk without diagnostic benefit for mechanical causes of instability, and CT without IV contrast should be obtained promptly to reduce morbidity and prevent secondary displacement 1, 2, 3

Delayed advanced imaging can lead to increased morbidity, and CT may miss small intraarticular fragments, highlighting the importance of prompt evaluation and consideration of MRI for soft tissue complications 1, 2, 3
For ceramic acetabular liner fractures, CT may be more sensitive than radiographs, and prominent anterior inferior iliac spine can limit hip range of motion and contribute to instability, identifiable on CT 4