Lower Back Pain & The Herniated Disc

The familiar term 'slipped disc' is generally a misnomer to describe a herniated disc and fortunately for us, discs found between vertebrae of the spine are physically unable to 'slip out of place' as they are firmly attached to these structures.
Intervertebral discs can, however, wear, split or herniate (bulge outwards). 

The term herniation is a broadly used term to describe the displacement of focalised intervertebral disc material which is beyond the limits of the disc's space (13, 18). The classification of the herniated disc depends on either the annulus fibrosus (AF), the disc's outer and tougher covering. Or, the nucleus pulposus (the jelly like center of the disc) (22).

Disc herniations can be as a result of of a sudden injury to the structure such as a trauma, progressive degenerative changes or from repetitive stress from certain activities at work or during exercise (9, 22). 
Biomechanical studies, (studies that analyse movement during activity) have mainly found that injury to a disc rarely occurs via axial compression alone (or spinal compression which causes shortening along the spine curvature) (8, 21). Instead, spine shrinkage and the development of disc herniations are more commonly caused from the repetitive motions of forward spinal bending (flexion) and rotation (torsion) (8, 26). 

The intervertebral disc (IVD) is the largest avascular structure in the body and serves to allow movement between adjacent vertebral bodies, absorb shock and transmit loads through the vertebral column (7, 12).  The IVD are mainly composed of three parts: 

1. Annulus fibrosis
2. Cartilaginous vertebral endplate
3. Nucleus pulposus 

Annulus Fibrosus (AF)
The AF is the primary load-bearing component of the IVD and is composed of collagen fibers which are tightly arranged in 10-20 sheets of lamellae (2, 5). These are arranged and positioned in onion like rings around the central nucleus pulposus and the alternating alignment of fibers within the layers account for its strength and its ability to withstand the forces applied to the disc in all directions (2, 13). The directions of the layers of the annulus fibrosus alternate which adds to the strength of the annulus fibrosus. The posterolateral aspect of the annulus fibrosus has a greater content of vertically oriented fibers which weakens the disc tissue and explains why most tears or annular fissures occur at this particular region of a disc (19).  

The AF of the lumbar spine IVDs are at their thinnest posteriorly by only having half the thickness of the anterior and lateral aspects of the annulus as there are fewer, finer and more tightly packed collagen fibers (lamellae) (2, 13). This makes the area of the AF more susceptible to injury at the lumbar intervertebral disc, especially if torsional (rotational) forces are applied.

Vertebral Endplates (EPs)
EPs are cartilaginous structures that are stongly attached to the intervertebral disc (IVD) via the annulus fibrosus but weakly attached to the vertebral bodies (2, 12). The endplates are situated superiorly and inferiorly in every disc and cover the whole length of the nucleus pulposus, but do not cover the entire extent of the anulus fibosus (2).  

Nucleus Pulpsoes 
Is an oval shaped hydrated gelatinous material contained within a ring of collagen fibres and contains mostly type II collagen which is elastic in nature and usually found in tissues that are exposed to pressure (2, 13). 

Disc herniation can occur in any disc within the spine but the majority of disc herniations occur within the lumbar spine, particulalry L4-L5 or L5-S1 (17).Lumbar disc herniation is the most common spine disorder requiring surgical intervention and it has been estimated that approximately 5–15% of patients with lower back pain suffer from lumbar disc herniation (9). The second most common site is the cervical region (C5-C6 or C6-C7) (16). Disc herniations can occur at any age, but are mainly known to be experienced between the 4th and 5th decades of life (23).

There are various personal and occupational risk factors for sciatica and prolapse discs which include (5):

• Smoking
• Obesity
• Age
• Height
• Mental Stress
• Exposure to vibration from vehicles

There are two general forms of presentation for a herniated disc; either peripheral or central. 

Annular Disc Tear
This is when a tear or fisure occurs within one or more layers of the annulus fibrosus and most are asymptomatic. Symptomatic annular tears or fissures without disc herniation are treated with NSAIDs and physical therapy (19).Thus, even if a disc prolapse or annular tear is discovered via medical imaging (e.g. MRI), pain is NOT necessarily experienced. 

Pain from an annular tear might either be acute if the tear occurs suddenly or more chronic if there is a slower development of the annular fissure.If an annular fissure or tear is symptomatic, it may cause one of two findings: 

1. Localised pains that are secondary to an annular tear which might be worse during certain movements and can stress or irritate the focal annular tear. In such cases, there is no radicular nerve involvement, and orthopaedic testing might be unrevealing.

2. Radicular symptoms secondary to irritation of the passing nerve root. In some cases, an annular tear can irritate a traversing nerve and cause radiculopathy (due to be explained in another blog post). If the annular fissure or tear is deep enough, disc material can herniate and irritate or compress neighbouring nerves or the spinal cord which can cause radicular symptoms including pain, paresthesia, and/or weakness depending on the extent of the nerve irritation (21).

According  to Ma (2015),  the pathological classification of lumbar disc protrusion is controversial and the study describes four different types of lumbar disc protrusion. To keep matters simple, four problems of the intervertebral disc resulting from injury have been listed and briefly explained below:

Disc Protrusion
In a protruded disc, the disc bulges posteriorly without rupture or tearing of the annulus fibrosus (15). There is localised displacement of the disc material (more than 25% of the circumference of the disc) (Kushchayev et al., 2018). 

Prolapsed Disc 
The outermost fibers of the annulus fibrosus (AF) contain the nuceleus Pulposus (14).

Disc Extrusion 
The annulus fibrosus (AF) is perforated and part of the nucleus pulposus (NP) moves into the epidural space (15). 

Sequestration
When a formation of discal fragments from the annulus fibrosus (AF) and nucleus pulposus (NP) is no longer connected to the disc (15).

This form of disc herniation and figure  does sound and look horrific compared to the other types listed above and one might think that surgical intervention would be the only recommendation for recovery. But, it has been known for patients to recover completely after nonsurgical conservative management.

The study by Orief (2012) revised six patient case studies who had experienced and been diagnosed with a symptomatic sequestrated disc levels L4-5 in three cases, L5-S1 in two cases, and C5-6 in one case.All six patients experienced associated acute radicular pain due to sequestrated intervertebral disc herniation and refused surgery as they were worried about complications. All six patients received conservative treatment that consisted of oral anti-inflammatory drugs, analgesics, muscle relaxants and physical therapy. Their radicular pains diminished and recovered within 3 to 6 weeks and resorption of the sequestrated intervertebral disc herniation was seen in their follow-up MRI scans after 4 to 9 months (18).

Carragee et al., (2003) categorized disc herniation into the following four groups and classified them as follows:
1) Type I, fragment-fissure herniation
2) Type II, fragment-defect herniation
3) Type III, fragment-contained herniation
4) Type IV, non-fragment-contained herniation.

Interestingly, this study found that the type II herniated disc category (the fragment-defect herniation group), with extruded fragment and defects on the posterior annulus, showed a 27% chance of recurrence and 21% chance of re-operation (3).
Type IV (non-fragment-contained group) showed 38% chance of remaining radiating pain and herniated disc recurrence (3).

The diagnostic accuracy of taking a case history and performing a physical examination is still insufficient. Diagnostic imaging in patients is often used to assess nerve root compression caused by disc aviation or spinal stenosis and cauda equina syndrome. Imaging is also used to identify the affected disc level before surgery or medical intervention (7, 8).

Magnetic resonance imaging (MRI), computed tomography (CT), x-ray and myelography are used as a form of diagnostic imaging.

XRay is the most commonly used form of imaging technique due to its lower cost and ready availability (7).

Magnetic resonance imaging (MRI) Scans are mostly used out of all forms of imaging for suspected lumbar spine pathologies. 

Computer Tomography (CT Scan) is less costly than the MRI, its testing time is shorter and the availability of CT scanners is larger in hospital settings but has the drawback of exposure to ionising radiation (7). Myelography involves the injection of contrast medium of the lumbar spine followed by x-ray CT or MRI imaging. 

Initial management includes rest as indicated, physical therapy, and appropriate use of pain medication. Studies report that in most instances, radicular symptoms resolve within six weeks. Clinically, I have experienced symptoms to take much longer as lifestyle and daily activity, occupation, long hours driving or travelling, diet along with various other factors all play a role for the rate of recovery. Due to the nature of injury and the need to manage new lifestyle habits and daily routine, rehabilitation can be incredibly frustrating for both practitioner and client and setbacks often happen. If symptoms persist, consideration can be given to ordering epidural steroid injections.

For manual therapy, caution regarding rotatory lumbar manipulation is advised, but manipulation has been demonstrated to improve symptoms of pain and body functional over sham treatment when rehabilitating patients with a lumbar herniated disc (17).
It has also been observed that skilled manual therapists who utilize mobilisation and manipulation above and below the affected spinal segment(s) and address the pelvis, or restrictions in the lower extremity, may decrease the amount of mechanical stress placed on the herniated disc(s).

Overall, manual therapy does play a role in pain management and potentially provide an optimal environment for the disc(s) to heal. This particularly being the case during the early and middle stages of rehabilitation.
As the patient progresses into the later stages of rehabilitation, however, the patient is encouraged to reduce their level of manual therapy and become more active via exercise programmes and increase their independence (18). 

Shin (2014) reported that only 10% of all lumbar disc herniation cases are candidates for surgery which has an encouraging success outcome of 80-90% (19).  The option for surgery is likely considered and recommended for if cauda equina syndrome is diagnosed (4). This is a rare condition which develops when a disc compresses the cauda equina and can cause unilateral or bilateral sciatica, motor weakness, and urinary incontinence or retention. Saddle anesthesia (loss of sensation in the area of the buttocks, posterior superior thighs, and perineum) is characteristic, and anal sphincter tone may be diminished (4). The surgery option also tends to be suggested if there is no pain relief at all after nonsurgical treatment amongst other factors such as the medical imaging reports and severity of pain (20).  

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21.) Tenny, S., Gillis, C. C. (2019) Annular Disc Tear,  University of Nebraska Medical Center, StatPearls Publishing LLC. 

22.) Vangelder, L. H., Hoogenboom, B. J., Vaughn, D. W. (2013) A Phased Rehabilitation Protocol For Athletes With Lumbar IVD Herniation, IJSPT, 8; 4: 482-516. 

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25.) Waturau, K., Deie, M., Fujita, N., Tanaka, N., Nakanishi, K., Sunagawa, T., Asaeda, M., Nakamura, H., Kono, Y., Ochi, M. (2016) Characterstics of Thoracic and Lumbar Movements During Gait In Lumbar Spinal Stenosis Patients Before and After Decompression Surgery, Clinical Biomechanics, Elseiver, 40:45-51.

26.) Wisleder, D., Smith, M. B., Mosher, T. J., Zatsiorsky, V. (2001)  Lumbar spine mechanical response to axial compression load in vivo. Spine, 15, 26;18: E403-9.