Dr. Jon Block explains how discogenic pain is identified, why a degenerating disc on MRI may not tell the whole story and how tissue-based approaches are being studied earlier in care.
Low back pain is a global crisis and the leading cause of disability worldwide. Pain can arise from several structures in the spine, including the intervertebral disc. When degeneration of the disc itself causes pain, it is known as lumbar discogenic pain. However, a major hurdle in research is that a degenerated disc on MRI does not always equal pain.
To bridge this gap, researchers combine imaging with clinical history and physical exams to identify the right patients for new trials. Currently, many patients are stuck in a “treatment gap,” having exhausted physical therapy, injections and medications, but not yet reached the point where surgery is considered. This has increased interest in minimally invasive approaches that target the degenerating disc itself.
In this Xtalks Clinical Edge feature, Dr. Jon Block, Chief Clinical Officer at VIVEX Biologics, discussed how lumbar discogenic pain can be distinguished from other sources of chronic low back pain, the clinical features researchers use to identify patients and why function, quality of life and real-world evidence can add context to pain scores. With more than 40 years in clinical research and medical affairs, Dr. Block shared his interest in minimally invasive tissue-based treatments as another option for patients before surgery.
— Dr. Jon Block, Chief Clinical Officer, VIVEX Biologics
Distinguishing Discogenic Pain from Other Sources of Low Back Pain
“With discogenic pain, the disc is intact. So it’s the degeneration of the disc itself that is causing the pain as opposed to a herniation of the disc,” said Dr. Block.
The intervertebral disc is the cushion-like structure between the vertebrae. In a disc herniation, part of the disc protrudes from its normal space and may compress nearby nerves, producing a different pain pattern.
Disc herniation with radiculopathy often produces pain that follows a defined nerve distribution down the leg. Discogenic pain tends to occur along the midline of the lower back and may include more diffuse pain in the buttocks or legs.
“The degeneration of the entire spine and motion segment starts at the disc,” he said.
As disc degeneration progresses, Dr. Block explained, other structures in the motion segment, including the facet joints and surrounding spaces, may become involved and introduce additional pain sources.
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A Treatment Gap Between Conservative Care and Surgery
The treatment pathway can include physical therapy, epidural steroid injections and medications before disc arthroplasty or spinal fusion enters the discussion.
“There’s the thought often that the disc is where treatments go to die,” noted Dr. Block.
A healthy intervertebral disc is largely avascular and aneural, meaning it has very little direct blood supply or innervation. He called this a naturally “hostile environment” and linked these properties to the disc’s role as a shock absorber. During degeneration, nerve fibers and blood vessels can grow into the disc and contribute to pain.
— Dr. Jon Block, Chief Clinical Officer, VIVEX Biologics
Finding the Right Patients for Discogenic Pain Trials
Dr. Block described a relatively narrow clinical trial population that may include patients with pain lasting at least six months, inadequate response after at least three months of conservative care and imaging evidence of disc degeneration.
MRI findings also inform patient selection. In the studies Dr. Block referenced, patients generally fall between grades 3 and 7 on the modified Pfirrmann grading scale, which assesses the severity of intervertebral disc degeneration.
He also highlighted pain provoked by forward flexion, or leaning forward, and difficulty sitting for extended periods as clinical features considered alongside imaging and pain location.
“People just can’t sit for more than about 30 minutes before they become very aggravated, very irritated and so forth. So it eliminates things like airplane travel and things like that.”
These features are considered alongside imaging and midline pain when identifying patients for discogenic pain trials.
— Dr. Jon Block, Chief Clinical Officer, VIVEX Biologics
Measuring Pain, Function and Real-World Outcomes
A pain reduction of at least 30% from baseline is considered a minimal improvement, while a 50% reduction represents a substantial improvement, according to Dr. Block. Patients who reach a sufficiently low pain score may also be considered to have reached an acceptable symptom state.
“If you have functional problems for long enough, your quality of life goes down.”
Persistent pain can interfere with back function, with prolonged functional limitations eventually affecting quality of life. Measuring these domains can show whether an intervention is improving patients’ ability to function in daily life alongside reducing pain.
“Clinical trial data, remember, is sort of like working inside of a test tube or a Petri dish. It’s not really the real world.”
Clinical trials use defined inclusion and exclusion criteria and closely follow participants. Patients encountered in routine care may have several conditions, treatments and clinical factors interacting at once.
Large healthcare and claims databases capture these patients in routine care. Their data largely reflect healthcare utilization, while clinical trials can directly collect symptoms and functional outcomes.
“But real world data oftentimes doesn’t show you actual patient symptoms. Those aren’t recorded. You can only look at these surrogate measurements.”
Frequent imaging may suggest clinicians are still searching for the source of a patient’s symptoms, while a decline in imaging use may indicate that this diagnostic search has eased.
Where Could Tissue-Based Approaches Fit?
“We’re at the very early stages, honestly,” said Dr. Block. Several approaches are being studied, including cell-based therapies in randomized controlled trials and tissue-based interventions intended to address changes within the degenerating disc.
He cited VIVEX Biologics’ ViaDisc NP as an example, a donor-derived nucleus pulposus tissue allograft intended to supplement the degenerating disc.
Cell-based approaches introduce cells into the disc to produce extracellular matrix. The tissue-based approach supplies that matrix directly.
“They’re trying to take nascent cells, introduce them into the disc, and have them create extracellular matrix. We’re simply replenishing it directly,” he said.
Dr. Block expects research across these approaches to expand over the coming years. Longer-term studies will help clarify how durable clinical responses are and where minimally invasive approaches may ultimately fit in the treatment pathway.
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