CT of the lumbar spine

Types of CT reconstructions and evaluation modes

Multidetector computed tomography (MDCT) allows image reconstruction in any anatomical plane. Various modes are used for a comprehensive analysis of the lumbar spine:

• Axial slice (in soft tissue window): a transverse cross-section that enables detailed examination of the spinal canal lumen and surrounding soft tissues.
• Sagittal slice (in bone window): a longitudinal projection optimal for assessing the trabecular bone structure of vertebral bodies, spinous processes, and measuring intervertebral disc space height.
• Three-dimensional (3D) reformation: generates a complete external 3D model of the lumbar spine and pelvis used for spatial analysis of complex deformities.
• 3D reformation with a virtual slice: a specialized mode allowing a 3D model to be visually "sectioned" for a clear examination of the internal bone structure and spinal canal.

Diagnosis of trauma and osteoporosis

The thoracolumbar junction (at the T10–L2 level) is one of the most mobile segments of the spine, making it vulnerable to injury even with relatively minor physical impact. In contrast, the thoracic spine is fixed by the ribs and sternum into a rigid bony ring. If a displaced sternal fracture is detected, the physician must rule out a thoracic spine fracture. Enormous force is required to fracture such structures, which always mandates ruling out concomitant vascular injury.

Diagnostic features in trauma:

1. CT is highly sensitive to bone injuries and posterior elements of the spine (including facet joints), but does not rule out ligamentous tears.
2. If CT scans show intact bones, but the patient has persistent movement-induced pain or neurological symptoms, an urgent MRI (MRI) is indicated. The primary goal is to promptly detect an epidural hematoma requiring emergency surgical drainage to save the spinal cord from compression.
3. In osteoporotic patients, even minimal axial loading without significant trauma history can cause a compression fracture. Such compression sometimes leads to avascular vertebral necrosis and its delayed destruction — Kummell disease (Kummell disease).

Plasma cell dyscrasias and oncology

Computed tomography is actively used to detect bone marrow tumors arising from clonal proliferation of B-lineage plasma cells. For their screening, low-dose CT, PET-CT (PET-CT), and whole-body MRI (WB-MRI) demonstrate significantly higher sensitivity than conventional plain radiography.

• Multiple myeloma (MM): the most common primary malignant bone tumor in adults. Radiologically characterized by classic "punched-out" (punched-out) lytic bone destruction lesions against the background of generalized osteopenia and multilevel vertebral collapses.
• Solitary plasmacytoma: appears as an expansive lytic bone lesion with a soft tissue component.
• Monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma: also belong to this group and require imaging monitoring.
• Systemic mastocytosis: a disease manifesting in the 5th to 8th decades of life. In 90% of cases, the bone marrow is involved, clinically presenting with thoracic and lumbar pain as well as arthralgia. The condition may be associated with myelodysplastic syndromes and leukemias.

Comparison of imaging modalities and postoperative follow-up

Although CT remains the primary imaging modality for bones, various modalities are used for comprehensive spine evaluation depending on the clinical task:

• Plain radiography: has lost its status as a definitive diagnostic method (especially in trauma, where up to 55% of cervical injuries are missed), but retains value for standing views.
• MRI (MRI): the gold standard for detecting spinal cord pathologies and postoperative fibrosis.
• Spinal angiography (DSA / DSA): due to its exceptionally high spatial resolution, it is the reference standard for evaluating spinal arteries.
• SPECT/CT (SPECT/CT): a combination of functional and anatomical imaging. Unquestionably outperforms MRI and standard CT in assessing spinal fusion (arthrodesis) hardware loosening, searching for postoperative infections, and identifying areas of active degenerative changes.

Class and exam questions

What else to study on this topic

• Cervical spine imaging features («swimmer's» view and occult craniocervical junction injuries).
• WHO mastocytosis classification: from indolent to aggressive and mast cell leukemia.
• Principles of emergency imaging for spinal cord compression caused by epidural hematoma.
• The role of the STIR sequence in MRI diagnostics of spinal pathologies.

Other topics in the "Spine" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.