Management of Transitional Vertebra at L5 with Pseudoarthrosis (Bertolotti's Syndrome)
For a patient with a transitional L5 vertebra and unilateral pseudoarthrosis causing symptoms, surgical decompression via L5 transverse processectomy is the definitive treatment after failed conservative management, with 87% achieving satisfactory outcomes. 1
Initial Diagnostic Confirmation
- Confirm the diagnosis with targeted diagnostic blocks to identify the pain generator—either the pseudoarthrosis itself or L4 nerve root compression from the enlarged transverse process 1
- Obtain CT imaging to clearly delineate the bony anatomy of the pseudoarthrosis between the L5 transverse process and sacral ala 2, 3
- Add coronal T1-weighted MRI sequences specifically to evaluate for S1 nerve root entrapment at the pseudoarthrosis level, as conventional sagittal and axial sequences frequently miss this pathology 3
The pseudoarthrosis in Bertolotti's syndrome creates two distinct pain mechanisms: direct pain from the abnormal articulation itself and nerve root compression (typically L4 or S1) from the hypertrophic transverse process 1, 3. Diagnostic blocks are essential because they determine the surgical approach—patients whose pain responds to pseudoarthrosis blocks versus L4 nerve root blocks have different outcomes with the same procedure 1.
Conservative Management Trial
- Implement 3-6 months of conservative therapy including activity modification, bracing, and structured physical therapy before considering surgery 4
- Reassess every 4-6 weeks for progressive neurological deficits including radiculopathy, sensory changes, or motor weakness 4
Surgical Intervention
When conservative management fails and symptoms persist:
- Perform L5 transverse processectomy using a paraspinal approach with bisectional cutting of the enlarged transverse process 1
- This addresses both the pseudoarthrosis and decompresses the L4 nerve root simultaneously 1
- Patients with pain relief from pseudoarthrosis blocks achieve 86% satisfactory results (excellent/good), while those with L4 nerve root compression achieve 95% satisfactory results 1
The surgical technique involves complete resection of the enlarged transverse process rather than fusion, which distinguishes this from typical lumbar pseudoarthrosis management 1. This is critical because the pseudoarthrosis here is congenital/developmental, not a failed fusion attempt 2.
Key Clinical Pitfalls
- Do not confuse this with post-surgical pseudoarthrosis—transitional vertebra pseudoarthrosis is a congenital variant causing Bertolotti's syndrome, not a failed fusion 2
- Standard sagittal and axial MRI sequences miss the pathology—you must specifically order coronal T1-weighted sequences to identify S1 nerve root entrapment 3
- Plain radiographs alone are insufficient—CT is necessary to fully characterize the bony anatomy of the pseudoarthrosis 2, 3
- Younger patients (mean age 53 years) with chronic unilateral buttock and leg pain should raise suspicion for this diagnosis 1, 2
Post-Treatment Monitoring
- Mean postoperative VAS scores decrease from 7.5 to 2.9, with most improvement occurring in the first 6 months 1
- Monitor for adjacent segment degeneration as transitional vertebrae accelerate disc degeneration at the level above 3
- Repeat imaging should not occur more frequently than every 2 years unless clinically indicated 4
The evidence strongly supports surgical decompression over fusion for symptomatic transitional vertebra pseudoarthrosis, as the goal is to eliminate the abnormal articulation and decompress neural structures rather than create a solid fusion 1.