Intradiscal Pressure Distributions in Degenerated Intervertebral Discs: A Biomechanical Investigation

Purpose: Disc degeneration (DD) can adversely affect its morphology and material properties, resulting in altered intradiscal pressure (IDP) profiles and, consequently, a cascade of spinal disorders. Previous studies have measured pressure values inside degenerated discs locally or along a specific path; however, no studies have quantified IDP distributions on the entire space in degenerated discs. The purpose of this study was to measure the IDP profiles across the entire cross-sectional area of degenerated discs. Methods: Six cadaveric spine segments were dissected and isolated from the torso. The inferior discs of these spine segments were completely cut in half in the transverse plane to insert a pressure mapping sensor between the two parts of the resected disc. Mechanical testing was then performed on all the segments while pressure distributions were simultaneously recorded for the entire duration of loading to fracture. Results: Pressure distribution patterns remained constant throughout the loading duration. The pressure distributions showed asymmetrical patterns across the cross-sectional area. The pressure values in the nucleus of a degenerated disc were considerably lower than those in the annulus region. Spinal loads estimated from pressure data agreed well with those measured by the load cell. Unlike a healthy disc that transfers most of the spinal load through the nucleus, a degenerated disc in our study showed the nucleus carrying only 40% of the load. Conclusion: The results of this study offer valuable insights into the impact of DD on the loading environment within the disc, causing an abnormal pressure distribution pattern.