Study examines source of back and joint pain in bid to reverse-engineer treatments

Summary: Researchers are studying the process of musculoskeletal tissue degeneration that leads to chronic back and joint pain in hopes of translating their findings into new methods for repairing tissue damage and ultimately relieving pain.

Source: Johns Hopkins Medicine

It’s a familiar story: you feel a pinch in your back and the next thing you know, you can’t get out of bed. From back pain to aching joints, musculoskeletal pain, while common, can be life changing and debilitating. But does it have to be?

That’s the big question for Jill Middendorf, assistant professor of mechanical engineering at Johns Hopkins University, who studies the mechanical factors that cause our cartilage, ligaments and joints to break down.

“Our goal is to understand the process of degeneration of musculoskeletal tissues, including cartilage, ligaments and intervertebral discs, using advanced mechanical techniques,” says Middendorf. “If we understand why this process occurs, we hope to translate our findings into new methods to repair damaged tissue and prevent more pain,”

In a recent study published by the Journal of Biomechanical EngineeringMiddendorf and his collaborators sought to understand how the soft tissues of the spine change when intervertebral discs break down or degenerate over time.

Specifically, they looked at the facet capsular ligament, a soft tissue that holds both sides of the facet joint together and is thought to be a common cause of lower back pain. Previous studies suggest it may be related to mechanical changes that occur in this ligament as the spine degenerates, although it’s unclear exactly why, Middendorf says.

This shows a drawing of a man holding his back in pain
Previous studies suggest it may be related to mechanical changes that occur in this ligament as the spine degenerates, although it’s unclear exactly why, Middendorf says. Image is in public domain

To find out, the team extracted capsular ligaments from the facets of cadaver spines and conducted experiments to measure the mechanical properties of the ligament, such as stress and strain, under different loading conditions. By comparing MRI images of the spine and their experimental results, the team found that the tissues of the ligament became stiffer as the spine degenerated.

The researchers believe that this increased stiffness causes a change in the load in the surrounding tissues and may explain why some people experience pain in the facet joints.

“Here we show that there is a correlation between the mechanics of the ligament and degeneration of the spine, which brings us even closer to being able to determine if this ligament is causing pain or if it is ‘another part of the spine,’ says Middendorf.

Using information gathered from their tissue experiments, researchers at the Middendorf lab plan to continue to deepen our understanding of spinal degeneration and create artificial musculoskeletal tissue that can be implanted to replace damaged or diseased tissue.

However, when it comes to pain, the answers are not always easy to find.

“’One of the challenges associated with diagnosing and treating spinal pain is determining the source of the pain,’ says Middendorf.

“But we can better understand the causes and mechanisms of tissue damage, which means we may one day be able to reverse engineer to find a solution.”

About this chronic pain research news

Author: Press office
Source: Johns Hopkins Medicine
Contact: Press Office – Johns Hopkins Medicine
Picture: Image is in public domain

Original research: Access closed.
“The lumbar facet capsular ligament becomes more anisotropic and the fibers become stiffer with degeneration of the intervertebral disc and facet joint” by Jill M. Middendorf et al. Journal of Biomechanical Engineering


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The capsular ligament of the lumbar facet becomes more anisotropic and the fibers become stiffer with degeneration of the intervertebral discs and facet joints

Degeneration of the lumbar spine, and in particular how this degeneration can lead to pain, remains poorly understood. In particular, the mechanics of the facet capsular ligament may contribute to low back pain, but the mechanical changes that occur in this ligament with spinal degeneration are unknown.

Additionally, the highly nonlinear, heterogeneous, and anisotropic nature of the facet capsular ligament makes it more difficult to understand mechanical changes. Clinically, signs of facet joint and intervertebral disc (IVD) degeneration based on magnetic resonance imaging (MRI) are correlated.

Therefore, this study investigated how the nonlinear and heterogeneous mechanics of the facet capsular ligament change with lumbar spine degeneration as characterized using MRI.

Cadaveric human spines were imaged by MRI, and L2-L5 facet joints and DIVs were scored using Fujiwara and Pfirrmann scoring systems. Then, the facet capsular ligament was isolated and biaxially loaded.

Nonlinear mechanical properties of the ligament were obtained using nonlinear generalized anisotropic inverse mechanics (nGAIM) analysis. Then, a Holzapfel-Gasser-Ogden (HGO) model was fitted to the stress-strain data obtained from nGAIM.

The facet capsular ligament is stiffer and more anisotropic at higher Pfirrmann grades and higher Fujiwara scores than at lower grades and scores. Analysis of ligament heterogeneity showed that all tissues are highly heterogeneous, but no distinct spatial patterns of heterogeneity were found.

These results show that degeneration of the lumbar spine, including the facet capsular ligament, appears to occur as a global joint phenomenon and advance our understanding of lumbar spine degeneration.

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