Transpedicular surgery for dorsolumbar junction disc prolapse: anatomic and biomechanical considerations of a minimally invasive approach.

The dorsal spine is the least affected region of the spine for intervertebral disc prolapse. The majority of cases of thoracic disc prolapse affect the lower dorsal spine, probably due to the increased mobility of that region. The dorsolumbar junction (DLJ) comprises D10 to L1 together with the intervening discs. Over a period of nine years, we have operated on thirty-two DLJ disc prolapses using a transpedicular approach in thirty patients. There were eight cases of D10/D11 disc prolapse, ten of D11/D12, and twelve of D12/L1 prolapse. Two patients had more than 1 level involvement. Back ache was the predominant symptom in patients with DLJ disc prolapse, seen in 92 % of cases. Presentation was in the form of conus/cauda equina syndrome with D11, D12 and L1 radiculopathy. All the patients were evaluated by MRI. Disc prolapse was eccentric in 10 and diffuse central in 22 levels. There was a distinct neurological improvement in all patients after surgery, pain relief being the most prominent feature. The dorsolumbar region differs from the dorsal spine in terms of mobility, anatomic and biomechanical features. It is a transition zone between the relatively fixed dorsal spine and the mobile lumbar region. These differences account for the higher incidence of disc prolapse in the region as compared to the dorsal spine cranial to D10. The transpedicular approach appears to be most suitable for discectomy for DLJ disc prolapse. The approach is minimally invasive considering the size of the incision, minimal bone removal and avoidance of vital structures. Postoperative pain is minimal and ambulation can be begun within 24 hours of surgery.