What is the recommended approach for a patient requiring an MRI of the left hip and femur?

MRI of the Left Hip and Femur: Recommended Approach

Begin with plain radiographs (AP pelvis and lateral femoral head-neck views) before proceeding to MRI, as radiography should be obtained first in most cases and serves as an essential screening tool that guides subsequent imaging decisions. 1

Initial Imaging Strategy

Plain Radiographs First

• Obtain AP pelvis radiograph plus lateral femoral head-neck view (such as Dunn view, frog-leg/Lauenstein view, or cross-table lateral) as the initial imaging study 1
• Radiographs detect approximately 90% of proximal femoral fractures and provide critical information about common disorders including arthritis, bone tumors, dysplasia, and femoroacetabular impingement 1
• A pelvis view is superior to isolated hip views as it allows comparison to the contralateral side and detects concomitant pelvic fractures 1
• Radiographs guide selection of additional imaging techniques and provide essential comparison for MRI interpretation 1, 2

When to Proceed to MRI

Clinical Scenarios Requiring MRI After Radiographs

MRI without IV contrast should be performed when:

• Radiographs are negative, equivocal, or nondiagnostic but clinical suspicion remains high for fracture, soft tissue injury, or intra-articular pathology 1
• Suspected radiographically occult fracture with persistent hip pain after trauma 1, 3
• Evaluation of soft tissue abnormalities (tendinosis, bursitis, labral tears, muscle injuries) 1
• Assessment of osteonecrosis, tumors, or inflammatory conditions 1, 2
• Suspected impingement syndrome or labral pathology when surgical intervention is being considered 1

MRI Protocol Specifications

For suspected occult fractures:

• Limited MRI protocols using coronal T1-weighted and STIR sequences are 100% sensitive and can be completed in less than 5 minutes 4
• This approach demonstrates 99% sensitivity and 99% specificity with an area under the ROC curve of 1.0 4
• MRI detects fractures with near 100% accuracy when radiographs are indeterminate, allowing confident discharge if negative 1

For soft tissue and intra-articular evaluation:

• MRI is highly sensitive and specific for detecting osseous and soft tissue abnormalities and should generally be the first imaging technique after radiographs 1
• IV gadolinium contrast is rarely needed for standard MRI evaluation 1
• Direct MR arthrography (intra-articular gadolinium injection) may be considered for labral tear evaluation, though high-resolution 3T MRI may obviate this need 1

Critical Clinical Considerations

Diagnostic Limitations

• Imaging should never be used in isolation—always combine with patient symptoms and clinical signs when making treatment decisions 1
• Diagnostic imaging demonstrates only small to moderate post-test probability shifts for many hip conditions 1
• Incidental intra-articular findings are common in asymptomatic individuals and require appropriate clinical sensitivity 1

Common Pitfalls to Avoid

• Do not obtain MRI as first-line imaging without radiographs—this wastes healthcare resources and delays appropriate care 1
• Do not assume negative radiographs exclude fracture in patients with high clinical suspicion—up to 10% of proximal femoral fractures are radiographically occult 1
• Be aware that up to 30% of atypical femoral fractures are bilateral; consider imaging the contralateral femur when indicated 1
• MRI findings of labral tears and cartilage pathology are highly prevalent in asymptomatic young adults—correlation with symptoms is essential 5

Specific Clinical Contexts

For acute trauma with suspected fracture:

• If radiographs are negative but clinical suspicion persists, MRI demonstrates 99-100% sensitivity for occult proximal femoral and pelvic fractures 1, 4
• MRI also characterizes fracture morphology, detecting intertrochanteric extension in seemingly isolated greater trochanter fractures 1

For chronic hip pain:

• MRI evaluates iliopsoas bursitis, athletic pubalgia, trochanteric bursitis, abductor tendinosis/tears, calcific tendonitis, hamstring injuries, and referred pain sources 1
• For femoroacetabular impingement and labral pathology, both MRI and radiographs provide complementary information about joint structures and bone morphology 1

For suspected osteoarthritis:

• Physical examination and radiography may be superior to MRI with reasonable sensitivity and specificity 1

Technical Considerations

• 3T MRI scanners achieve 100% sensitivity for fracture detection 4
• Titanium implants produce fewer artifacts than stainless steel, allowing improved MRI evaluation if hardware is present 6
• Interpretation by certified radiologists achieves 99% sensitivity 4