Bertolotti syndrome is a congenital spinal variation recognized as a cause of chronic lower back pain. The syndrome involves an abnormal articulation or fusion of the lowest lumbar vertebra (L5) with the sacrum or ilium, an anomaly present from birth. This anatomical difference, known as a lumbosacral transitional vertebra (LSTV), disrupts the normal biomechanics of the lower spine and pelvis. While the LSTV variant is common, Bertolotti syndrome is diagnosed only when this variation is the identifiable source of the patient’s pain. The condition is often overlooked, leading to prolonged periods where the cause of discomfort remains undiagnosed.
The Anatomical Basis
The foundation of Bertolotti syndrome is the presence of a lumbosacral transitional vertebra (LSTV) at the junction of the lumbar spine and the sacrum. This involves the transverse process of the fifth lumbar vertebra (L5) being unusually enlarged, forming an abnormal connection with the sacrum or the adjacent iliac bone. This abnormal joint is termed a “pseudoarticulation” or “false joint.”
The Castellvi classification system categorizes the variations of the LSTV:
- Type I involves an enlarged, dysplastic transverse process that does not fully articulate or fuse with the sacrum.
- Type II, often associated with the syndrome, describes a partial articulation or pseudoarticulation between the enlarged process and the sacrum.
- Type III denotes a complete bony fusion, known as sacralization, between the transverse process and the sacrum.
- Type IV is a mixed presentation, featuring a bony fusion on one side and a pseudoarticulation on the other.
This abnormal configuration alters how forces are transmitted through the lower spine, leading to biomechanical stress and subsequent pain.
Recognizing the Symptoms
The primary symptom of Bertolotti syndrome is persistent or recurring lower back pain, often beginning in young adulthood. The pain is frequently localized to the side of the abnormal articulation, where the L5 transverse process meets the sacrum or ilium. This discomfort results from inflammation or arthritis developing at the pseudoarticulation site due to mechanical friction.
Patients commonly report that pain intensifies with activities involving arching backward, prolonged standing, or extended sitting. The altered mechanics of the lumbosacral junction can also cause stiffness and a reduced range of motion in the lower back. Pain may radiate into the buttock or hip region, which sometimes leads to misdiagnosis, as symptoms can mimic other common spine conditions.
The biomechanical strain from the LSTV can also predispose the segments above the anomaly to accelerated degenerative changes. This may include an increased incidence of disc herniations or facet joint arthritis at the vertebra immediately superior to the transitional segment.
Diagnosis and Confirmation
Diagnosis relies on combining a detailed clinical history with specific medical imaging. The initial step is usually a plain radiograph of the lumbosacral spine to visualize the enlarged transverse process of the L5 vertebra and its abnormal connection. Specialized views, such as a Ferguson radiograph, may improve visualization of the transitional segment.
Advanced imaging, such as Computed Tomography (CT) scans or Magnetic Resonance Imaging (MRI), provides a clearer assessment of the bony anatomy and surrounding soft tissues. These scans are used to rule out other common causes of low back pain, including disc herniation or spinal stenosis.
The most specific method for confirming the LSTV as the source of pain involves a targeted diagnostic injection. A local anesthetic, sometimes mixed with a corticosteroid, is precisely injected into the pseudoarticulation. Significant, though temporary, relief following this injection provides strong evidence that the transitional vertebra is the source of the symptoms.
Treatment Pathways
The initial management strategy is conservative, focusing on reducing pain and inflammation without surgical intervention. This begins with nonsteroidal anti-inflammatory drugs (NSAIDs) to manage pain. Muscle relaxants may also be prescribed to alleviate associated muscle spasms.
Physical therapy is a foundational component of conservative care, aiming to strengthen core muscles and improve flexibility. Therapeutic exercises stabilize the spine and improve posture, reducing mechanical stress on the abnormal junction. Targeted interventional treatments, such as localized steroid injections into the pseudoarticulation, are used when oral medications and physical therapy are insufficient. These injections decrease inflammation directly at the painful site, providing longer relief.
When conservative treatments fail, surgical intervention may be considered. The most common procedure is a pseudoarthrectomy, which involves the selective removal of the enlarged transverse process to eliminate mechanical friction.
A spinal fusion is an alternative, typically reserved for cases where the L5-S1 segment is unstable or has significant disc degeneration. Fusion permanently stabilizes the joint, though it risks accelerating degeneration in adjacent segments. Surgery is generally reserved for patients who responded positively to a diagnostic injection but still experience persistent pain.