Biomechanical Analysis of Lumbar Disc Degeneration Before and After Spinal Fusion

Maria Inês Vieira Godinho

Key information

Authors:

Maria Inês Vieira Godinho (Maria Inês Vieira Godinho)

Supervisors:

Paulo Rui Alves Fernandes (Paulo Rui Alves Fernandes); André Paulo Galvão de Castro (André Paulo Galvão de Castro)

Published in

January 22, 2021

Abstract

Advancing age and degeneration frequently lead to low back pain (LBP), which is the most prevalent musculoskeletal disorder worldwide. Changes in the ligamentous structures and intervertebral discs (IVD) are typically amongst the sources of instability. Spinal fusion techniques are therefore at the core of treatment options to remove the affected IVD and relieve LBP. The aim of this work was three-fold: (i) to understand how ligament degeneration links with LBP by determining the role of each ligament per movement, (ii) to evaluate the impact of IVD height reduction in degenerative changes, and (iii) to assess the more advantageous type of posterior fixation in interbody fusion to support clinical practice, particularly regarding adjacent disc degeneration (ADD). For that, two L3-L5 finite element models with different IVD heights were used. Different degrees of ligament and IVD degeneration were tested, and the Oblique Lumbar Interbody Fusion (OLIF) procedure was simulated with different fixation constructs. Facet capsular ligament and anterior longitudinal ligament were identified as the most influential ligaments for spinal stability, being this influence enhanced with degeneration and IVD height reduction. After spinal fusion, these ligaments became obsolete. The OLIF procedure contributed more to ADD than IVD degeneration of the pre-instrumented level, with bilateral fixation being the best option to achieve stability and lessen ADD risk. Between models with unilateral constructs, right unilateral fixation was the most suited to reduce IVD stress. Clinical practice will benefit from the outcomes of this study and from its future extension to a wider patient database.