Effect of overload on changes in mechanical and structural properties of disc biomechanics

Goal of the Study?

In this primary research study from the Biomechanics and Modeling in Mechanobiology Journal¹ the authors analyzed structural and mechanical properties in the Intervertebral Disc (IVD) of 10 lumbar spine regions collected post mortem from domestic pigs.  The goal was to analyze the effects of long-term cyclic loading in the hope of determining the actual mechanism of disc biomechanics and injury.

 

Why are they doing this study?

Spinal degeneration is one of the most frequently mentioned changes and over 80% of those are in degeneration with the IVD.  The problem of degeneration and subsequent changes in the mechanical and structural properties of the IVD is a fundamental issue in the pathomechanical formation of spinal injuries. Among the numerous factors contributing to these changes, the greatest impact comes from long-term cycle loading.  This study was aimed to analyze the overload change occurring in the IVD caused by long-term compression loads, especially the impact of degenerative changes on the posterior column of the spine.  

 

 

What was done?

Fourteen Functional Spine Units (FSU) of the ten lumbar regions were removed from post mortem domestic pigs and cleaned of soft tissue.  The junctions between the vertebral bodies and the IVD and within the zygapophysial joint were left intact.  Eight lumbar regions were subjected to a series of cyclic compression loading. The other two lumbar regions of each FSU constituted the control group.  The non-control lumbar regions of the 14 FSU’s were divided into 2 equal groups. The first seven consisted of the segments with an Intact Posterior Column (IPC).  The second group had the articular processes removed to obtain segments Without a Posterior Column (facets), but with an intact anterior column (disc), a junction between the vertebral bodies and the IVD.  The impact of cyclic compression loads on the structural changes of disc biomechanics was analyzed macroscopically both in the control group and the two test groups.   

 

What did they find?

The test results show a significant decrease in the disc height after prolonged compression cyclic loading.  They also found that the posterior column does not significantly influence the change in this value in the form of support on the articular processes, but it does affect how fast this change happens.  

 

Why do these findings matter?

Investigating and understanding the processes of degenerative changes in the IVD will facilitate the direction and help shed light on future clinical treatments of patients with early diagnosis of spinal pain conditions.  The obtained results of this research may also be useful when selecting boundary conditions and validating numerical models of the IVD. 

 

At Dynamic Disc Designs, we have worked to develop a model that can show the time dependent height loss of the intervertbral disc under load. Often symptoms of back pain relate to load and time. Teaching the nociceptive drivers to patients can be empowering when the source(s) are clearly understood. We like to call it “patient-centred education”.