Percutaneous posterolateral discectomy. Anatomy and mechanism.

The evacuation and decompression of the herniated lumbar disc through a sheath inserted dorsolaterally represents a new concept in the treatment of radiculopathy associated with disc herniation. Only a small portion of the spinal nerve before its decent and positioning anterior to the transverse process is subject to insult by an instrument introduced into the intervertebral disc through a posterolateral approach. The chance of injury to the spinal nerve is further minimized when the instruments are introduced a distance of approximately 9-10 cm from the midline, parallel to the vertebral plates, and penetrating the annulus at 10 o'clock or 2 o'clock. The rapid decline of intradiscal pressure after dorsolateral fenestration of the annulus appears to be an important factor in the relief of sciatic pain following percutaneous posterolateral discectomy. The evacuation and decompression of an extruded intervertebral disc with a straight instrument may not be possible. Patients with sequestered disc require laminectomy.