What laboratory tests should be ordered for a patient with a pathological fracture of the lumbar spine?

Laboratory Tests for Pathological Fracture of Lumbar Spine

For a patient with pathological fracture of the lumbar spine, a limited standard laboratory examination should include erythrocyte sedimentation rate, serum calcium, albumin, creatinine, and thyroid-stimulating hormone, along with additional tests such as vitamin D, protein electrophoresis, and testosterone in men when clinically indicated. 1

Initial Laboratory Evaluation

Basic Laboratory Panel

• Complete blood count (CBC)
• Comprehensive metabolic panel (CMP) including:
  • Serum calcium
  • Albumin (to calculate corrected calcium)
  • Creatinine (kidney function)
  • Liver function tests
• Erythrocyte sedimentation rate (ESR)
• Thyroid-stimulating hormone (TSH)

Additional First-Line Tests

• 25-hydroxyvitamin D level
• Parathyroid hormone (PTH)
• Serum protein electrophoresis (SPEP)
• Urine protein electrophoresis (UPEP)
• Serum free light chains (if multiple myeloma is suspected)

Second-Line Testing Based on Clinical Suspicion

For Suspected Malignancy

• Tumor markers relevant to common metastatic sources:
  • Prostate-specific antigen (PSA) in men
  • Carcinoembryonic antigen (CEA)
  • CA 15-3 (breast cancer)
  • CA 19-9 (pancreatic cancer)

For Suspected Metabolic Bone Disease

• Bone-specific alkaline phosphatase
• Osteocalcin
• N-terminal telopeptide (NTX) or C-terminal telopeptide (CTX)
• 24-hour urine calcium and phosphorus

For Suspected Endocrine Disorders

• Testosterone levels in men
• Estrogen levels in women (if premenopausal)
• 24-hour urinary free cortisol (if Cushing's syndrome suspected)

Clinical Context Considerations

The EULAR/EFORT guidelines emphasize that pathological fractures require thorough investigation to identify underlying causes that may increase subsequent fracture risk 1. This evaluation helps inform therapeutic decisions regarding prevention of future fractures in high-risk patients.

When evaluating a pathological fracture, it's important to distinguish between osteoporotic fractures and those caused by malignancy or other conditions. While X-rays are the first-line imaging study for suspected vertebral fractures 1, 2, laboratory testing is essential to determine the underlying etiology.

Special Considerations

For Patients on Bisphosphonates

If the patient has been on long-term bisphosphonate therapy, consider testing for:

• Bone turnover markers (suppressed in long-term bisphosphonate use)
• Calcium and vitamin D levels (to rule out hypocalcemia)

This is particularly important as long-term bisphosphonate use has been associated with atypical fractures 3.

For Suspected Multiple Myeloma

• Complete SPEP with immunofixation
• Serum free light chains
• Beta-2 microglobulin
• Consider bone marrow biopsy if laboratory tests suggest myeloma

Common Pitfalls to Avoid

1. Overlooking secondary causes: Don't assume osteoporosis is the only cause without investigating other potential etiologies.

2. Incomplete metabolic workup: Failure to check calcium, phosphorus, and vitamin D levels may miss hyperparathyroidism or osteomalacia.

3. Missing malignancy: Protein electrophoresis should be included in the initial evaluation to screen for multiple myeloma, which commonly presents with pathological vertebral fractures.

4. Ignoring medication history: Long-term corticosteroid use or certain anticonvulsants can contribute to bone fragility and should prompt specific laboratory evaluations.

5. Not correlating with imaging: Laboratory results should be interpreted in conjunction with imaging findings, as some pathological fractures (e.g., metastatic disease) may show characteristic patterns on MRI 4.

By following this comprehensive laboratory evaluation approach, clinicians can effectively determine the underlying cause of pathological fractures of the lumbar spine and develop appropriate treatment strategies to prevent future fractures and improve patient outcomes.