1327 - Lumbosacral Transitional Vertebra as an Underrecognized Source of Low Back Pain: A Case Report

Lumbosacral Spondylosis, Other

Case Description:

A 64-year-old male presented with chronic low back pain radiating to the left leg, complicated by intermittent foot drop with ambulation. Symptoms persisted despite oral analgesics, multiple caudal epidural steroid injections, and years of physical therapy. Imaging revealed advanced multilevel degeneration, spondylolisthesis, and a sacralized L5 with bilateral transitional articulations. Diagnostic review clarified only four lumbar-type vertebrae, a grade 2 spondylolisthesis at L4–L5, and bilateral L5-S1 intertransverse articulations. There was no evidence of instability on imaging. 

Physical exam reproduced concordant pain over the transitional region. Critically, while epidural injections failed, fluoroscopically guided diagnostic/therapeutic injections of the transitional articulation produced immediate relief of nearly 100%, which persisted over six months on the right, alongside meaningful gains in ambulation, sleep, and decreased reliance on analgesics.

Discussions:

This case emphasizes the diagnostic and therapeutic significance of transitional anatomy in refractory low back pain. Although extensive degenerative disease was present as well, the patient’s lumbosacral transitional vertebrae (LSTV) proved to be the primary pain generator. LSTV may often be overlooked, though reported prevalence may range from 4-30% in the general population. LSTV may also alter lumbosacral biomechanics, so recognition of LSTV requires a high index of suspicion, particularly when conventional interventions fail. The Castellvi classification system is widely used to categorize these anomalies and proper identification is key to avoid wrong-level interventions. Along with classification, diagnostic injections can both localize symptoms and guide management.

Conclusions:

Lumbosacral transitional articulations are very common yet underrecognized in chronic low back pain. This case highlights the importance of anatomy-driven evaluation and demonstrates that targeted treatment of symptomatic transitional articulations can provide life-altering relief. Physiatrists and clinicians should remain vigilant for transitional joints as pain generators early in the diagnostic algorithm to optimize outcomes and avoid unnecessary procedures.