When is a lumbar x-ray (Lumbar Radiograph) recommended for a patient with psoriasis?

Lumbar X-ray for Psoriatic Arthritis

Lumbar x-rays are recommended for patients with psoriasis who present with symptoms of axial involvement, including inflammatory back pain, limited spinal mobility, or clinical suspicion of sacroiliitis or spondylitis. 1

Indications for Lumbar X-ray in Psoriasis Patients

Patients with psoriasis should undergo lumbar radiographic evaluation when they present with:

1. Inflammatory back pain characteristics:

   • Onset before age 45 years
   • Symptoms persisting for ≥3 months
   • Morning stiffness lasting >30 minutes
   • Pain that improves with exercise but not with rest
   • Insidious onset
   • Alternating buttock pain 1

2. Clinical findings suggestive of axial involvement:

   • Limited spinal mobility in sagittal and frontal planes
   • Reduced lateral flexion
   • Restricted cervical rotation 1, 2

3. Suspected axial disease based on physical examination:

   • Limitation of motion of lumbar spine
   • Clinical evidence of sacroiliitis 1

Diagnostic Criteria for Axial Involvement

According to the Annals of the Rheumatic Diseases guidelines, diagnosis of axial disease in psoriatic arthritis should be based on the presence of at least two of three criteria:

1. Inflammatory back pain (as described above)
2. Limited spinal mobility
3. Radiological criteria - including plain x-ray showing unilateral sacroiliitis grade 2 or more, syndesmophytes, or MRI changes in sacroiliac joints 1

Imaging Algorithm for Suspected Axial Involvement

1. First-line imaging: Plain radiographs (including lumbar spine)

   • Recommended as the initial imaging modality for evaluation of suspected axial spondyloarthropathy 1
   • Can detect structural changes including sacroiliitis, syndesmophytes, and spondylitis

2. Second-line imaging (if radiographs are negative or equivocal):

   • MRI of sacroiliac joints and/or spine (preferred)
   • CT scan if MRI is contraindicated 1

Important Clinical Considerations

• Axial involvement occurs in approximately 25-70% of patients with psoriatic arthritis 3
• Radiographic progression in axial PsA may be independent of clinical symptoms, with patients potentially having significant radiographic changes despite minimal symptoms 4
• Radiographic assessment should not be repeated more frequently than every 2 years unless clearly indicated in individual cases 1
• Patients with psoriasis whose history includes onset of back pain before age 40, night pain, or improvement with exercise should be referred to a rheumatologist 5

Pitfalls and Caveats

• Radiographic findings represent structural consequences of inflammation and often lag behind clinical symptoms by 7 or more years 1
• Plain radiographs have low sensitivity for detecting early disease changes
• Axial PsA may have less pain and less limitation in movement compared to ankylosing spondylitis, potentially leading to underdiagnosis 1
• Axial involvement in PsA may be asymmetric and can affect any level of the spine in a "skip" fashion, unlike the more predictable pattern in ankylosing spondylitis 1
• Patients may have clinical symptoms of pain but negative radiographs, necessitating advanced imaging 5

By following these guidelines, clinicians can appropriately utilize lumbar x-rays in the evaluation of patients with psoriasis who may have axial involvement, leading to earlier diagnosis and treatment of psoriatic arthritis with axial manifestations.