A new study questions long-held beliefs about one of the most common causes of back pain, lumbar disc herniation.
The findings could have major treatment implications by modifying the conventional understanding of how lumbar disc herniation occurs.
In the study, researchers found that most cases of lumbar disc herniation are not caused by ruptured discs as previously thought, but by avulsion (separation) of the connective tissue between the spinal bone and disc in a process known as end plate junction (EPJ) failure.
“Our study shows that the incidence of EPJ failure has been grossly underrated, probably because of the difficulty of documentation,” the researchers wrote.
A herniated disc, frequently called a “slipped” disc, occurs when the soft inside of a spinal disc protrudes outside of the tougher exterior due to aging, injury, or degenerative disc disease. In cases of injury, scientists believed the primary mechanism of disc herniation took place when the disc itself ruptured, allowing the soft center to leak out.
To test that theory, researchers publishing in the journal Spine studied 181 patients receiving surgery for herniated discs. In order to rule out any influence of aging and spinal disc degeneration, the study only included patients younger than the age of 60 and excluded those with disease impacting more than one disc.
Researchers conducted a thorough examination of patients using MRI and CT scans, x-rays, microscopic tests, and observations in surgery. They set out to determine the causes of disc herniation, whether it was due to a ruptured disc or to avulsion (separation) of the end plate junction. Contrary to conventional wisdom, the researchers discovered that EPJ failure was a much more common cause of disc herniation than ruptured discs (annulus fibrosis). In 65% of patients (65%), the EPJ had been torn off (avulsed) while a true ruptured discs was only found in 11% of patients.
At times, the EPJ failure was not apparent on x-rays but could be seen in surgery, and most were visible on CT scans. This difficulty in documenting EPJ failures is likely why it goes undetected. For most cases, there was not a single traumatic event prior to symptoms, suggesting that disc herniation could take several months to develop after fracture.
This research could create new opportunities and strategies for preventing the progression of lumbar disc herniation after EPJ avulsion. Earlier studies show that chiropractic care is an effective method for relieving lumbar disc herniation in many patients. In one recent study, chiropractic was more effective than epidural steroid injections for relieving back pain after lumbar disc herniation. Chiropractic has also been found to be beneficial for patients with cervical disc herniation and neck pain, according to another new study.
Rajasekaran S, et al. ISSLS Prize Winner: The anatomy of failure in lumbar disc herniation: an in vivo, multimodal, prospective study of 181 subjects. Spine 2013; 38(7): 1491-1500.