911 - An Atypical Cause of Low Back Pain: Lumbar Facet Arthropathy Secondary to Unilateral Bertolotti’s Syndrome

The patient is a 61 year old female evaluated in clinic for focal low back pain. The pain was insidious in onset with progressive worsening over 10 years, with acute worsening following a motor vehicle accident 6 months prior to presentation. Patient had attempted multiple conservative modalities with no improvement. Physical exam was notable for lumbosacral paraspinal tenderness to palpation as well as pain with lumbar facet loading bilaterally.

X-Ray of the lumbar spine with flexion and extension demonstrated a unilaterally sacralized L5 on the left transverse process with pseudoarthrosis, consistent with type 2 Bertolotti’s syndrome. MRI of the lumbar spine demonstrated significant facet arthropathy worst at L4-L5. The patient underwent bilateral lumbar medial branch block at L3, L4, and L5 with an 80% improvement in her symptoms, confirming facet arthropathy as the cause of her low back pain.

Discussions: This case demonstrates an interesting presentation of facet arthropathy secondary to unilateral type 2 Bertolotti’s syndrome at the left L5-S1 transverse process. While transitional vertebrae are typically incidental findings, they can often be an underdiagnosed cause of low back pain. In the setting of unilateral Bertolotti’s syndrome, axial loading of the vertebra leads to uneven biomechanical stressors with the corresponding facets superior to the transitional vertebra suffering from degeneration at a higher rate than the contralateral facets. Furthermore, underdevelopment of the iliolumbar ligament on the ipsilateral side can further contribute to imbalances in axial loading.


Conclusions:

Bertolotti's syndrome is an uncommon and potentially underdiagnosed cause of low back pain in older individuals given the biomechanical changes that unilateral transitional vertebra have on axial loading. The magnitude of effect and long term management of this condition merits further research.