Purpose: To review the association of isolated L4/5 disc disease with accessory articulations between the transverse processes of L5 and the sacral ala.

Methods and Materials: The association of chronic back pain and the presence of a lumbosacral transitional vertebra has been well described (Bertolotti`s Syndrome). Twenty six patients with isolated L4/5 disc disease were identified in a retrospective review of four hundred consecutive patients referred for MRI of the lumbar spine with back pain and suspected disc disease. In each case, coronal images were reviewed to determine the presence or absence of accessory articulations between the transverse process of L5 and the sacral ala.

Results: Twenty four of twenty six patients with isolated L4/5 disc disease had either uni or bilateral accessory articulations between the transverse process of L5 and the sacral ala (mean age 38 years). In the remaining 374 patients (mean age 54 years, P<.001), accessory articulations were identified in two patients both of whom had multilevel disc disease.

Conclusion: Isolated L4/5 disc disease is associated with the presence of accessory articulations between the transverse processes of L5 and the sacral ala in most cases. Patients with accessory articulation at this site present with isolated disc disease at an earlier age relative to those with normal lumbo-sacral anatomy (P<.001). Isolated L4/5 disc disease is the cause of symptoms in most patients with Bertolotti`s Syndrome.