BACKGROUND: Bertolotti syndrome (BS) is characterized by chronic pain and functional impairment associated with lumbosacral transitional vertebrae (LSTVs). The study aimed to investigate the histologic characteristics of the pseudoarticulation between the enlarged transverse process and sacrum seen in Castellvi 2a LSTV and explore the involvement of nervous tissue in pain generation.
METHODS: Immunohistochemical analysis using S100 protein staining was performed to assess the presence of nerve tissue.
RESULTS: These changes included fibrillation, chondrocyte cloning, alterations in the proteoglycan matrix, and focal chondrocyte necrosis. Notably, no nerve tissue was observed in any of the specimens, as confirmed by negative S100 protein staining.
CONCLUSIONS: The study findings suggest that nerve tissue is not involved in the nociceptive mechanisms underlying pain in BS. The histologic similarities between the pseudoarticulation and osteoarthritic joints indicate that pseudoarticulation itself may be a significant source of pain in BS. These insights contribute to our understanding of the pathophysiology of BS and support treatment paradigms prioritizing pain control with medications such as NSAIDs before considering surgical intervention. Future studies with larger sample sizes and in vivo models are needed to further validate these findings and explore the changes in joint histology under biomechanical forces in LSTVs.

•Key anterior approaches differences in LSTV include vascular (aortic bifurcation/iliocaval confluence), muscular (psoas) and osseus anatomy (inter-crestal tangent/pubic symphysis), when compared to non-LSTV.•There are increased surgical deviations but not significantly greater complications for anterior approaches in LSTV.•Vascular awareness while accessing L45 will be in the presence of a more cephalad ABF and ICC with sacralized L5, and access to the deeper L56 level will be in the presence of a more caudal ABF and ICC in lumbarized S1.

Bertolotti syndrome is a commonly missed cause of intractable back pain that affects 4% to 8% of the general population. It involves the congenital malformation of a transitional lumbosacral vertebra, with total or partial and unilateral or bilateral transverse process (TP) fusion or articulation to the sacrum. The pain can be debilitating, and the tethering of the spine to the sacrum can encourage deformity formation in the coronal plane and lead to early degenerative changes, especially if present only unilaterally. We present the case of a 24-yr-old woman with no notable prior medical history who presented with years of lower axial back pain radiating to her thighs, which limited her activities of daily living and was resistant to conservative management. Her imaging showed an abnormally large left L5 TP, which was articulated to the sacrum, and signs of early coronal deformity. She had responded almost completely to repeated steroid injections into the TP-sacral joint, but that effect was very transient. Informed patient consent was obtained prior to her surgery. She underwent a minimally invasive tube disconnection of the abnormal joint with partial distal resection of the TP, and her symptoms completely resolved. This case highlights the importance of correlating clinical symptoms with aberrant anatomy, and the role of selective surgery in providing symptomatic relief. This case report was written in compliance with our institutional ethical review board approval, and patient consent was waived in light of the retrospective and deidentified nature of the data presented in accordance with the University of Texas Southwestern institutional review board.

Bertolotti syndrome describes lower back pain secondary to an anatomical lumbosacral transitional vertebrae. We present the case of a 37 year old female with chronic lower back pain with radiological evidence of an anatomical lumbosacral pseudojoint. The patient underwent minimally invasive resection of her pseudojoint with complete resolution of symptoms postoperatively. We, as the authors would like to highlight that in patients with pain secondary to an aberrant lumbosacral articulation, consideration should be given to treatment via a minimally invasive technique.