Introduction: Traditional thoracolumbar osteotomies for correction of sagittal imbalance include net shortening of the posterior column, require wide exposure of the of the spinal column anatomy posteriorly and are associated with significant morbidity. Anterior longitudinal ligament release (ALR) using the minimally invasive lateral retroperitoneal approach for lumbar interbody fusion (MIS LIF) with a resultant net lengthening of the anterior column has been performed as an alternative to increase lordosis. Our objective is to demonstrate the feasibility of ALR during the MIS LIF by describing its surgical anatomy in the lumbar spine.
Methods: Forty-eight lumbar levels were dissected on 12 fresh cadaveric specimens to study the anterior longitudinal ligament (ALL), its surrounding structures and determine the feasibility of the technique. In each specimen the lumbar disc spaces and ALL were accessed via the lateral transpsoas approach.
Results: In the cadaveric study, release of the anterior longitudinal ligament proves to be feasible from the lateral MIS LIF approach. The structures at most immediate risk during this procedure are the aorta, inferior vena cava (IVC), common iliac vessels, and sympathetic plexus. The aorta and IVC run along the left and right anterolateral border of the ALL, respectively, while the sympathetic plexuses run on the anterolateral aspects of the vertebral bodies, farther lateral than the great vessels. These are generally encountered during ALR and need to be dissected anteriorly off the ALL.
The ALL in the lumbar spine traverses the anterior aspect of all vertebral bodies and disc spaces, and is composed of three layers: superficial, intermediate, and deep. It is thinner and wider at the level of the disc but thicker and narrower at the vertebral bodies.
Conclusions: Our early experience suggests that ALR through the MIS LIF is a feasible technique. However, it is vital that we understand the intrinsic relationships of the ALL and surrounding anatomy.
Patient Care: To expand the armamentarium used in the treatment of adult spinal deformity
Learning Objectives: By the conclusion of this session, participants should be able to:
1. Understand the difference between traditional posterior shortening osteotomy techniques and anterior lengthening techniques.
2. Describe the anatomy of the anterior longitudinal ligament in the lumbar spine
3. Discuss the benefits of this technique in adult degenerative scoliosis