Surgical outcome of a patient with Bertolotti's syndrome in whom the established Castellvi classification system failed: illustrative case.

Background: Bertolotti's syndrome is a condition of the lower back and/or L5 distribution leg pain caused by a lumbosacral transitional vertebra (LSTV). Diagnosing the LSTV as the cause of the symptoms and condition is essential for accurate management of this syndrome. Castellvi's classification system is widely accepted for LSTV anatomy, but it measures only one aspect of transitional anatomy and was intended primarily to identify target-level disk herniations.

Observations: In this case, the Castellvi classification system failed to identify the patient (with 2 years of back and L5 pain) as having an LSTV, even though he displayed LSTV-like anatomy because both L5 transverse process heights measured less than 19 mm. He attained brief but significant relief from bilateral injections into the L5-S1 transverse/ala region and underwent a minimally invasive bilateral decompression of L5-S1 with almost complete relief of his symptoms maintained more than 6 months postoperatively.

Lessons: Given that the patient gained significant relief from treatment of transitional anatomy that failed to be identified using Castellvi's classification system, this case suggests that transverse process height may not be adequate or even the most clinically relevant indicator in identifying LSTV anatomy, which is a precursor to the diagnosis of Bertolotti's syndrome.