Investigating Back Pain: Shedding Light on Modic Changes 

The Burden of Chronic Low Back Pain

Chronic low back pain is the leading cause of years lived with disability in humans worldwide. It entails persistent discomfort in the lower region of the spine, often impairing mobility, reducing quality of life, and causing substantial suffering. While it is difficult to pinpoint the specific cause of this ailment, in humans it is commonly associated with degenerative changes in the spinal discs – small shock-absorbing cushions that separate vertebrae, the bones comprising the spine.  

Understanding the combination of factors that contribute to this condition has been a longstanding challenge, leading to a recent study by Martijn Beukers and colleagues. By closely investigating alterations within spinal structures, their research sheds light on potential triggers for chronic low back pain, with a particular focus on a phenomenon called “Modic changes.” 

Modic Changes

Modic changes, named after the Danish radiologist Michael Modic, are alterations within the vertebral bodies adjacent to the intervertebral discs and are intriguing because they can serve as potential indicators of underlying spinal conditions. In humans, these changes have been linked to chronic lower back pain and have sparked extensive research into understanding their precise role and contributing factors.  

Modic changes come in three types, each potentially signaling different bone conditions. However, studying them at the tissue level and gaining an in-depth understanding of the underlying mechanisms in humans is challenging due to limited samples. As a result, researchers investigating Modic changes are turning to dog spines as a valuable model. Dogs with intervertebral disc disease present similarities to humans in terms of spine-related issues, making them useful in exploring these changes. Comparing dog and human spines could provide insights into diagnosing and treating spine issues for both species, leading to improved health outcomes for humans and dogs alike. Moreover, the translatability of dog research to humans could substantially increase the body of evidence in this field, as well as our understanding. However, dog Modic changes have remained relatively unexplored terrain – until now.  

How the Research was Conducted

In this study, vets who routinely perform research teamed up with expert scientists from the human field to provide in-depth analysis of medical records and MRI scans from a large pool of 340 dogs with symptoms of back pain or neurological issues. The research focused on the lower back. This area bears similarity to the human lumbar spine, often afflicted by chronic low back pain. 

What were the Results?

The study found that 66% of the dogs exhibited Modic changes, pointing to a potential parallel between human and canine spinal health. However, a key difference between humans and dogs was observed where in dogs, Type 3 Modic changes were the most prevalent, unlike the dominant Type 2 changes observed in humans. A possible explanation for this lies in the fact that dogs are usually diagnosed later than humans as pain is not always appropriately recognized by the dog owner or vet practitioner. 

As the researchers delved deeper into the findings, they identified age as a significant influencer in the occurrence of Modic changes. Older dogs were more prone to experiencing these spinal alterations. Additionally, dogs struggling with disc herniation – a condition where spinal disc cushions become displaced — were more likely to encounter Modic changes. 

What comes next?

This investigation by Martijn Beukers and colleagues into Modic changes in dog spines provides a deeper understanding of the mechanisms behind dog back pain and underscores the relationship between age, structural dynamics, and potential underlying conditions. By unearthing these connections, the study sets the stage to determine the translatability of Modic changes in dog low back pain patients to human low back pain patients.  

Epidemiology of Modic changes in dogs: Prevalence, possible risk factors, and association with spinal phenotypes

Authors: Martijn Beukers, Guy C. M. Grinwis, Johannes C. M. Vernooij, Lisanne van der Hoek, Anna R. Tellegen, Björn P. Meij, Stefanie Veraa, Dino Samartzis, Marianna A. Tryfonidou, Frances C. Bach

First published: 21st July 2023

Abstract: 

Background
Chronic low back pain, a leading contributor to disease burden worldwide, is often caused by intervertebral disc (IVD) degeneration. Modic changes (MCs) are MRI signal intensity changes due to lesions in vertebral bone marrow adjacent to degenerated IVDs. Only a few studies described the histopathological changes associated with MC to date. MC type 1 is suggested to be associated with bone marrow infiltration of fibrovascular tissue, type 2 with fatty infiltration, and type 3 with bone sclerosis in humans.
 
Methods
This study investigated whether the dog can be a valuable animal model to research MCs, by examining the prevalence, imaging, and histological characteristics of lumbar MCs in dogs (340 dogs, 2496 spinal segments).
 
Results
Logistic regression analysis indicated that the presence of lumbosacral MCs was associated with age and disc herniation (annulus fibrosis protrusion and/or nucleus pulposus extrusion). According to MRI analysis, MCs were mostly detected at the lumbosacral junction in dogs. Most signal intensity changes represented MC type 3, while previous spinal surgery seemed to predispose for the development of MC type 1 and 2. Histological analysis (16 dogs, 39 spinal segments) indicated that IVDs with MCs showed more histopathological abnormalities in the endplate and vertebral bone marrow than IVDs without MCs. Mostly chondroid proliferation in the bone marrow was encountered, while the histologic anomalies described in humans associated with MCs, such as fibrovascular or fatty infiltration, were scarcely detected.
 
Conclusions
Dogs spontaneously develop MCs, but may exhibit other pathological processes or more chronic bone marrow pathologies than humans with MCs. Therefore, more research is needed to determine the translatability of the MCs encountered in dog low-back-pain patients.

Funding information: This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement no. 825925 and the Dutch Arthritis Society (LLP22 and LLP12). We are grateful to Khaled Aboushaala, MD (Department of Orthopedic Surgery, Rush Medical College, Rush University Medical Center, Chicago) who retrieved representative MRI of Modic changes in the human spine for Figure 2.

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