The Purpose of the Spinal Disc is the Equal Distribution of Loads
The primary role of the spinal disc is to equally distribute the load/pressure that is placed upon it during different movements and positions across the outer portion of the disc, the annulus. This responsibility is handled by the center of the disc, called the nucleus pulposus (the nucleus). During flexion, extension, lateral bending and extension the nucleus migrates in the direction of least resistance... that is away from the load upon it. Similar to sitting on an inflated balloon, the air inside moves similar to the discs nucleus and the force is distributed equally across the rest of the internal surface area of the balloon.
When different forces are placed onto the disc, the nucleus moves to the the area of least resistance thereby equalizing the load equally on the disc.
When Do Damaged Discs Require Surgery & When Is Conservative Care is Appropriate
The normal disc has an internal hydrostatic pressure similar to the air inside a balloon. This internal pressure is required to be able to produce enough load/force to be able to rehabilitate a damaged disc. If there was a hole in the balloon that allowed the air to leak out when you sit on it, the normal load bearing function of the disc is reduced. In comparison, when there is a compromised "container" of the disc, the disc tissue can leak out and create a herniation or sequestration and the integrity of the disc has been compromised.
Understanding whether conservative care will be effective at helping a painful disc or whether surgery is required is determined during a thorough mechanical history and assessment by a clinician that is properly certified in Mechanical Diagnosis and Therapy® (MDT®). In its simplest form, the disc is challenged with forces created by different repetitive movements and static positions, while recording any changes in the patient's mechanical, symptomatic and functional baselines.
Discs that have enough internal pressure because the disc material is still being contained enough within the "disc container" to be able to provide enough force to remodel the damaged disc and have positive effects on the baselines can be treated with conservative care, and may not need surgical intervention.
A disc that does not have enough internal pressure because the "disc container" has ruptured and not enough force is available to remodel the damage and any attempt at remodeling the damage is not effective and is irreversible damage.
The determination that a disc has been damaged beyond the capabilities of conservative care requires determining that the disc does not have enough hydrostatic pressure (internal pressure) to be able to apply enough force to remodel the disc with MDT® (Mechanical Diagnosis and Therapy®) repetitive movement exercises.
Normal Degenerative Changes Occur in the Disc During Aging
The spinal disc goes through different structural changes as aging occurs that make the disc more vulnerable to becoming a pain producing pathology. Changes to the disc start early and continue throughout a lifespan. The disc dries out (becomes dessicated) and becomes less elastic and more fibrous and necrosis (a form of cell injury which results in the premature death of cells) increases causing less distinction between the outer annulus and inner nucleus. As the nucleus becomes less and less effective at its primary function, distributing weight evenly throughout the rest of the disc, increased vertical loads result in distortion, disruption and fissuring (cracking) in the outer portion of the disc,'s annulus, ultimately causing discrete or severe lumps, bumps, flaps or free floating disc material which can cause pain and obstruction to movement.
Nerve Supply of the Spinal Disc
There is research that shows that only the outer 2/3rds of the outer annulus has a nerve supply, mostly on each side and in the back of the disc and also in the two large ligaments that are found in the front and back of the spine, the anterior and posterior longitudinal ligament. (Bogduk (1994b, 1997) (Yoshizawa et al. 1980; Ashton et al 1994). However there is also evidence that in painful and degenerated discs the innervation can be much more extensive and nerve supply was found extending into the inner annulus and outer portion of the nucleus (Coppes et al. 1997; Freemont et al 1997).
Determining Whether It's The Disc Causing the Pain, or Something Else
One of the key confounding factors in determining the cause of back pain is that 50% of people that have MRI's, x-rays or CAT scans that show a damaged, disrupted, bulged or herniated disc, don't have any symptoms. This means that disc surgery cannot be determined to be necessary based off of imaging findings alone, as there is no causal relationship (van Tulder et al. 1997c) (Boden et at. 1990; Jensen et al. 1994; Weinreb et al. 1989; Boos et al. 1995) (Buirski and Silberstein 1993). MRI's are not good at determining whether a disc is painful or not.
Get more information about the McKenzie Method® or about disc treatment for the lower back or disc treatment for the neck
Sign-up For A Free Workshop
MDT Pre-surgical screenings and Treatment Interventions Have Been Shown To Reduce Surgical Rates and Related Costs by 50%.
Rasmussen C, et al.
Rates of Lumbar Disc Surgery Before and After Implementation of Multidisciplinary Nonsurgical Spine Clinics. Spine 30; 21:2469-73. 2005, Van Helvoirt H, et al. Transforaminal Epidural Steroid Injections Followed by MDT to Prevent Surgery for Lumbar Disc Herniation. Pain Med.15(7):1100-8. 2014
The Lumbar Spine- Mechanical Diagnosis and Therapy Vol 1-2; Robin McKenzie & Stephen May