THE POSTERIOR PARASPINAL APPROACH TO THE LUMBAR SPINE: ANATOMIC STUDY

Abstract

Purpose of the study: The posterior paraspinal approach to the lumbar spine was initially described and promoted by Wiltse for posterolateral arthrodesis of the lumbosacral junction in patients with spondylolisthesis. Despite technical improvements proposed by Wiltse, the muscular cleavage is still poorly localized in the sacrospinalis muscle. The purpose of this work was to provide a more accurate anatomic description of this spinal approach and to describe anatomic landmarks to facilitate execution of the procedure.

Material and methods: Fifty anatomic specimens were dissected (27 male and 23 female cadavers); 33 had been embalmed. The anatomy study used a bilateral approach to the spine. The exact anatomic localization of the muscle cleavage was noted. Measures were taken in relation to the mid line of the L4 spinatus process.

Results: In all specimens, the muscle cleavage lay between the multifidus and longissimus heads of the sacrospinalis muscle. A fibrous partition was noted in 88 of the 100 specimens. The mean distance from the mid line to the cleavage line was 4.04 cm (range 2.4–7.0 cm). The surface of the sacrospinalis muscle presented fine perforating arteries and veins in all specimens, directly in line with the cleavage plane. In 12 cases, a major posterior sensorial branch of the L3 nerve running to the skin was identified in the cranial portion of the approach.

Discussion: The muscle cleavage plane appears to be easy to localize for the paraspinal approach to the lumbosacral junction. Opening the aponeurosis of the latissimus dorsi near the mid line enables visualization of the perforating vessels in line with the anatomic cleavage plane of the sacrospinalis muscle. In our experience, this plane is situated on average 4 cm from the mid line. Hemostasis of these vessels is acceptable since the sacrospinalis muscle has a rich supply of anastomosed vessels. Care must be taken to avoid injury to the posterior sensorial branch of the L3 nerve which runs along the plane of the muscle cleavage.

Conclusion: In our opinion, this minimally hemorrhagic approach is perfectly adapted to non-instrumented fusion of the lumbosacral junction, particularly for spondylolisthesis in children and adults. Precise knowledge of the anatomy of this approach is a necessary prerequisite for successful execution.