Para-muscular and trans-muscular approaches to the lumbar inter-vertebral foramen: an anatomical comparison.

Foraminal and extra-foraminal disc herniations comprise up to 11.7% of all lumbar disc herniations. Facetectomy, which had been the classic approach, is now recognized as cause of pain and instability after surgery. Otherwise, posterior lateral approaches through a trans-muscular or a para-muscular technique offer no significant damage to key structures for spinal stability. The surgical anatomy of these approaches has already been described, but they were not compared. In order to quantify the angle of vision towards the intervertebral foramen offered by each technique, 12 fresh cadavers were dissected and studied regarding these approaches. The angle presented by trans-muscular approach was wider in all studied lumbar levels. Surgery through the trans-muscular approach is performed with a better working angle, requiring a smaller resection of surrounding tissues. Therefore, minor surgical trauma can be expected. Our measurements support previously published data that point the trans-muscular approach as the best surgical option.