What is the recommended initial diagnostic step for evaluating left hip pain?

X-ray for Left Hip: Recommended Initial Diagnostic Approach

Radiography should be obtained first in the evaluation of left hip pain, including an anteroposterior (AP) view of the pelvis and a cross-table lateral view of the affected hip. 1, 2

Standard Radiographic Protocol

The initial imaging should include:

• AP view of the pelvis with approximately 15 degrees of internal hip rotation 1, 2
• Cross-table lateral view of the symptomatic left hip (preferred over frog-leg lateral due to lower risk of fracture displacement in trauma cases) 1, 2
• The pelvis view allows comparison with the contralateral asymptomatic side, which is crucial for accurate diagnosis 2, 3

Clinical Context Determines Urgency

For Acute Traumatic Hip Pain:

• Radiography is the initial imaging modality of choice and can be performed portably in the trauma bay 1
• This rapid diagnosis reduces morbidity associated with acute hip fracture and/or dislocation by enabling prompt treatment 1
• Delays in diagnosis are associated with increased costs, complication rates, hospital length-of-stay, and mortality 1, 3

For Chronic Hip Pain:

• Radiographs should be obtained first in most, if not all, cases and provide specific information for common disorders such as arthritis or less common disorders such as primary bone tumors 1
• For osteoarthritis specifically, physical examination and radiography may be better than MRI and have reasonable sensitivity and specificity 1
• Specialized views (false profile or Dunn view) can provide more detailed evaluation for specific conditions like dysplasia or femoroacetabular impingement 1

Why Radiography First

Radiography serves as an excellent screening tool that guides selection of additional imaging techniques when needed 1. The American College of Radiology emphasizes that radiographs are fast to obtain and provide essential baseline information regardless of whether they are normal or abnormal 1.

Important Limitations to Recognize

• Approximately 10% of proximal femoral fractures are not identified on initial radiographs 2, 3
• Radiography provides high specificity (0.76-0.90) but variable sensitivity (0.44-0.78) for detecting cartilage damage, osteophytes, and bone attrition 4
• Imaging should never be used in isolation but must be combined with the patient's symptoms and clinical signs 1

Next Steps When Radiographs Are Negative or Equivocal

If Fracture Still Suspected (Acute Trauma):

• MRI without IV contrast is the recommended next imaging study, with near 100% sensitivity for proximal femoral fracture detection 2, 3
• CT without IV contrast is an alternative when rapid diagnosis is needed and MRI is unavailable, though patients with negative/equivocal CT may still need MRI 1

If Chronic Pain with Negative Radiographs:

• MRI without IV contrast should generally be the first imaging technique used after radiographs for detecting osseous and soft tissue abnormalities 1
• MRI is highly sensitive and specific for detecting abnormalities involving surrounding soft tissues including labral tears, tendinosis, bursitis, and muscle injuries 1
• Ultrasound can be used for specific superficial structures (abductor tendons, iliopsoas) or to guide injections 1

Common Pitfalls to Avoid

• Never rely solely on hip radiographs without including pelvis views, as this may miss associated pelvic fractures that can alter treatment decisions 2, 3
• Never make a diagnosis based on imaging alone—diagnosis requires integration of symptoms, clinical signs, and imaging findings 1
• Failing to obtain orthogonal views (both AP and lateral) can lead to missed fractures 2, 3
• Ultrasound should not be used as initial imaging for hip fracture detection due to poor specificity (only 65%) and inability to comprehensively evaluate bones 3