Finite element analysis of lordosis restoration with anterior longitudinal ligament release and lateral hyperlordotic cage placement
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Restoring sagittal alignment is an important factor in the treatment of spinal deformities. Recent investigations have determined that releasing the anterior longitudinal ligament (ALL) and placing hyperlordotic cages can increase lordosis, while minimizing need for 3 column osteotomies. The influences of parameters such as cage height and angle have not been determined. Finite element analysis was employed to assess the extent of lordosis achievable after placement of different sized lordotic cages.
A 3-dimensional model of a L3–4 segment was used. Disc distraction was simulated by inserting interbody cages mid-body in the disc space. Analyses were performed in the following conditions: (1) intact, (2) ALL release, (3) ALL release + facetectomy, and (4) ALL release + posterior column osteotomy. Changes in segmental lordosis, disc height, foraminal height, and foraminal area were measured.
After ALL resection and insertion of hyperlordotic cages, lordosis was increased in all cases. The lordosis achieved by the shorter cages was less due to posterior disc height maintained by the facet joints. A facetectomy increased segmental lordosis, but led to contact between the spinous processes. For some configurations, a posterior column osteotomy was required if the end goal was to match cage angle to intradiscal angle.
Increased segmental lumbar lordosis is achievable with hyperlordotic cages after ALL resection. Increased cage height tended to increase the amount of lordosis achieved, although in some cases additional posterior bone resection was required to maximize lordosis. Further studies are needed to evaluate the impact on regional lumbar lordosis.
KeywordsDeformity correction Finite element analysis Anterior longitudinal ligament release Sagittal alignment Spine
Conflict of interest
Dr. Uribe is a consultant for NuVasive, Inc., from which he has also received clinical/research support for the study. Dr. Akbarnia owns stock in NuVasive, Inc., and is a consultant for the company. Dr. Mundis is a consultant and receives royalties for NuVasive, Inc. Dr. Turner and Mr. Harris are employees of NuVasive, Inc., and own stock in the company.
- 13.Uribe JS, Smith DA, Dakwar E et al (2012) Lordosis restoration after anterior longitudinal ligament release and placement of lateral hyperlordotic interbody cages during the minimally invasive lateral transpsoas approach: a radiographic study in cadavers. J Neurosurg Spine 17:476–485CrossRefPubMedGoogle Scholar