Is a Computed Tomography (CT) scan of the hip necessary before a hip replacement surgery?

CT Scan Before Hip Replacement: Not Necessary for Routine Cases

A CT scan is not necessary before a routine hip replacement surgery and should be reserved for specific clinical scenarios where additional information is needed beyond standard radiographs. 1, 2

Standard Imaging Protocol for Hip Replacement

First-Line Imaging

• Standard radiographs should be the initial imaging modality for all patients undergoing hip replacement 2
• The radiographic evaluation should include:
  • AP (anteroposterior) pelvis view
  • Lateral hip view
  • Frog-leg lateral view (if tolerated) 2

When Additional Imaging Is Needed

Additional imaging beyond radiographs should be ordered only in specific clinical scenarios:

1. Suspected acetabular wall defects: CT is valuable when radiographs suggest medial, posterior, or superior acetabular wall deficiencies that may require bone grafting or special reconstruction procedures 3

2. Complex anatomy: In cases of extraarticular deformities or severe dysplasia that may complicate implant positioning 4

3. Preoperative planning for computer navigation or robotic assistance: CT may be used for 3D templating and surgical planning, though this is not a diagnostic indication 2, 4

4. Suspected ceramic acetabular liner fracture: CT may be more sensitive than radiographs in these specific cases 1

Evidence Against Routine CT Scanning

The American College of Radiology explicitly states there is "insufficient evidence to support the use of CT of the hip as the initial imaging procedure in the evaluation of the symptomatic hip" 1. This recommendation is based on comprehensive review of available evidence.

While CT scans can provide more accurate measurements for implant sizing and alignment than radiographs 4, the additional radiation exposure and cost are not justified for routine cases where standard radiographs provide sufficient information for successful outcomes.

Alternative Advanced Imaging When Needed

If advanced imaging beyond radiographs is required:

• MRI without contrast is the preferred next step for most musculoskeletal conditions affecting the hip, including:

  • Suspected labral tear
  • Tendinopathy
  • Bursitis
  • Bone marrow edema
  • Stress fracture
  • Osteonecrosis 2

• Contrast-enhanced MRI should be considered only for:

  • Suspected infection
  • Inflammatory arthritis requiring synovitis evaluation
  • Suspected tumor 2

Pitfalls to Avoid

• Ordering CT without a specific indication when radiographs are normal 2
• Assuming CT always provides better visualization of hardware (metal artifact can limit assessment) 2
• Ordering contrast-enhanced MRI unnecessarily, which increases cost, procedure time, and potential risks 2
• Failing to obtain appropriate clinical history to guide imaging protocol selection 2

Conclusion

While CT scanning can provide valuable information in specific scenarios, radiographs remain the gold standard first-line imaging for hip replacement planning. The decision to obtain additional imaging should be based on specific clinical indications rather than routine practice.