What to look for in an X-ray (X-radiation) of the hip and lumbosacral spine?

X-ray Evaluation of Hip and Lumbosacral Spine

When evaluating X-rays of the hip and lumbosacral spine, prioritize identifying structural changes that predict disease progression and complications: specifically look for syndesmophytes, disc space narrowing (especially at L1/L2 and L2/L3), osteophytes, end plate sclerosis, joint space narrowing, subchondral sclerosis, cysts, and femoral head/acetabular deformity. 1, 2, 3

Hip X-ray Evaluation

Primary Structural Features to Assess

• Joint space narrowing - This is the most critical finding and reflects cartilage loss; measure the superior joint space systematically 2, 3
• Osteophytes - Assess presence and severity at the femoral head and acetabular margins 2, 3
• Subchondral sclerosis - Look for increased bone density beneath the articular cartilage 2, 3
• Subchondral cysts - Identify cystic changes in the femoral head or acetabulum 3
• Femoral head and acetabular deformity - Document any structural changes or collapse 3

Clinical Correlation Points

• Range of motion limitation - Correlate radiographic findings with restriction of hip abduction and internal rotation, as these are the most important clinical findings 4
• Gait abnormalities - Look for antalgic gait patterns (shortened support phase on affected side) or waddling gait in bilateral cases 4
• Limb length discrepancy - Assess for shortening of the affected lower limb 4

Technical Considerations

• Pelvic radiograph in neutral position is the appropriate initial study for adults with suspected hip pathology 4
• Inferoposterior and posterolateral hip joint segments may be difficult to appreciate on plain radiographs and may require CT if clinical suspicion remains high 3

Lumbosacral Spine X-ray Evaluation

Disc Degeneration Features (L1/2 through L4/5)

• Disc space narrowing - This is the most reliable feature with highest interrater agreement (ICC 0.93-0.95); pay particular attention to L1/L2 and L2/L3 levels as narrowing here is significantly associated with hip pain 2, 5, 6
• Osteophytes - Assess presence and severity at each vertebral level; these correlate with increased bone mineral density 2, 5
• End plate sclerosis - Document sclerotic changes at vertebral end plates; this feature also correlates with increased BMD at both spine and hip 2, 5

Critical Diagnostic Relationships

• Upper lumbar disc degeneration (L1/L2, L2/L3) and hip pain - Disc space narrowing grade ≥1 at L1/L2 is significantly associated with hip pain (men OR=2.0, women OR=1.7), with even stronger associations for chronic hip pain (men OR=2.5) 6
• Lower lumbar levels (L3/L4/L5/S1) - Disc space narrowing at these levels is NOT significantly associated with hip pain 6
• This distinction is crucial: when hip pain is present, carefully evaluate the upper lumbar spine as a potential pain source 6

Spondyloarthritis-Specific Features

• Syndesmophytes - In patients with suspected axial spondyloarthritis, identify syndesmophytes in the lumbar and cervical spine as they predict development of new syndesmophytes 1
• Sacroiliac joint changes - Assess for sclerosis, erosions, and ankylosis 1

Osteoporosis Assessment Considerations

When Syndesmophytes Are Absent

• Hip DXA and AP-spine DXA should be used for osteoporosis assessment 1

When Syndesmophytes Are Present

• Hip DXA supplemented by lateral spine DXA or QCT is recommended because AP spine measurements can be spuriously elevated by syndesmophytes and degenerative changes 1
• Degenerative disease causes falsely elevated BMD in >81% of cases with spurious measurements 1

Fracture Evaluation

• Conventional radiography is the initial method when spinal fracture is suspected 1
• If radiography is negative and clinical suspicion persists, CT should be performed 1

Hip-Spine Syndrome Considerations

• Evaluate both regions systematically as biomechanical stress can transfer across the pelvic ring from hip to spine or vice versa 7
• Flexion-based problems (femoroacetabular impingement) and extension-based problems (ischiofemoral impingement) can both cause referred symptoms 7
• Pelvic parameters including pelvic incidence, pelvic tilt, sacral slope, and lumbar lordosis should be considered when interpreting findings 7

Common Pitfalls to Avoid

• Do not overlook upper lumbar disc degeneration (L1/L2, L2/L3) when evaluating hip pain - this is a frequently missed association 6
• Do not rely on AP spine DXA alone in patients with advanced degenerative changes or syndesmophytes as measurements will be falsely elevated 1
• Do not assume lower lumbar pathology (L3-S1) is the source of hip pain - the association is with upper lumbar levels 6
• Assess for quadratus lumborum involvement by evaluating painful points in the gluteal region, as this muscle can be compromised and may require specific imaging if bony pathology is suspected 4, 8