What is the significance of a nearly completely lumbarized S1 vertebra with a vestigial S1-2 intervertebral disc and facets in a 33-year-old male's X-ray?

From the Guidelines

Near completely lumbarized S1 with vestigial S1-2 disc and facets in a 33-year-old male is a congenital variation that may be associated with back pain, altered biomechanics, or accelerated degeneration at adjacent levels, and treatment is typically conservative with physical therapy, core strengthening, and pain management if symptoms are present, as recommended by the American College of Radiology 1.

Key Points

• This condition occurs during development when the normal segmentation and fusion of vertebrae is altered, resulting in the first sacral vertebra (S1) developing characteristics more similar to a lumbar vertebra, a condition called lumbarization.
• The S1-2 disc space and facet joints are described as vestigial, meaning they are underdeveloped or rudimentary.
• While often asymptomatic and discovered incidentally on imaging, this condition can sometimes be associated with back pain, altered biomechanics, or accelerated degeneration at adjacent levels due to abnormal stress distribution.
• According to the ACR Appropriateness Criteria, imaging is not typically warranted for acute low back pain with or without radiculopathy, and no red flags, as it is considered a self-limiting condition that is responsive to medical management and physical therapy in most patients 1.
• However, if symptoms persist or worsen, further evaluation with MRI or CT may be necessary to assess for potential actionable pain generators that could be targeted for intervention or surgery, as recommended by the American College of Radiology 1.

Treatment

• Treatment is typically conservative with physical therapy, core strengthening, and pain management if symptoms are present.
• Surgery is rarely indicated unless there are severe neurological symptoms or instability.
• It is essential to document this finding in the patient's medical record, as it may influence future spine evaluations or treatments.

Imaging

• MRI of the lumbar spine is the initial imaging modality of choice for evaluating low back pain, as it has excellent soft-tissue contrast and accurately depicts lumbar pathology, including disc degeneration, as well as the thecal sac and neural structures 1.
• CT myelography of the lumbar spine can be useful in assessing the patency of the spinal canal/thecal sac and of the subarticular recesses and neural foramen, and can be used for surgical planning in patients with significant spinal stenosis or cauda equina syndrome 1.

From the Research

Near Completely Lumbarized S1 with Vestigial S1-2 Disc and Facets

• A near completely lumbarized S1 with vestigial S1-2 disc and facets refers to a rare anatomical variation where the first sacral segment (S1) is partially or completely separated from the rest of the sacrum, resulting in a lumbar-like vertebra 2.
• This condition can be classified into different types, including partial or complete lumbarization, with complete lumbarization being further subdivided into different categories based on the degree of separation and the presence of accessory facets 2.
• The presence of a vestigial S1-2 disc and facets suggests that the lumbarization is not complete, and there may be some residual connection between the S1 and S2 segments 2.

Radiological Features

• Radiological features of near completely lumbarized S1 with vestigial S1-2 disc and facets may include a well-developed S1-2 disc, accessory facets between the transverse elements of the free S1 segment and the ala of the remaining sacrum, and attenuated laminae 2.
• Imaging studies such as X-rays, CT, and MRI can be used to evaluate the degree of lumbarization and the presence of any associated degenerative changes, such as disc herniations or facet joint osteoarthritis 3, 4, 5.

Clinical Implications

• Near completely lumbarized S1 with vestigial S1-2 disc and facets can be associated with low back pain and degenerative changes, particularly if there is abnormal stress on the affected segments 6.
• Treatment options may include conservative management, such as physical therapy and pain management, or surgical intervention, such as discectomy or fusion, depending on the severity of symptoms and the presence of any associated degenerative changes 3.