A 58-year-old man with a 5-year history of hip osteoarthritis presents with progressive pain and functional limitation. Plain radiographs show advanced degenerative changes with severe joint space narrowing. Before planning total hip arthroplasty, which investigation is most appropriate to assess the extent of cartilage loss and guide surgical decision-making?

## Preoperative Assessment of Advanced Hip Osteoarthritis ### Why MRI is Optimal **Key Point:** MRI is the investigation of choice for preoperative assessment of hip osteoarthritis because it provides: - Precise visualization of remaining articular cartilage thickness - Assessment of acetabular and femoral head bone quality - Detection of labral pathology or associated soft tissue abnormalities - Evaluation of subchondral cyst formation and bone marrow edema **High-Yield:** In advanced OA requiring surgical intervention, MRI helps determine: - Whether joint preservation is still feasible or replacement is necessary - Optimal surgical approach and implant selection - Presence of associated conditions (labral tears, femoroacetabular impingement) that may affect outcomes ### Clinical Scenario Analysis This patient has: - Established diagnosis on plain radiographs - Advanced degenerative changes requiring surgical planning - Need for detailed soft tissue and cartilage assessment MRI provides superior soft tissue contrast and allows quantitative measurement of remaining cartilage, essential for surgical decision-making. ### Investigation Comparison for Hip OA | Investigation | Utility in Hip OA | Preoperative Role | |---|---|---| | **MRI** | Cartilage detail, soft tissue, bone marrow | Gold standard for surgical planning | | **CT** | Bony anatomy, complex geometry | Better for acetabular anatomy; less cartilage detail | | **Serum Biomarkers** | Disease activity monitoring | Research use; not for surgical planning | | **DEXA** | Bone mineral density | Osteoporosis screening; unrelated to OA severity | **Clinical Pearl:** While CT is excellent for assessing bony anatomy and may be used in complex cases (e.g., acetabular dysplasia, severe deformity), MRI remains superior for cartilage assessment and soft tissue evaluation in routine preoperative OA assessment.