FREEZE: PBL Questions
What neuro / musculoskeletal features of the lumbar spine predispose to painful
injury? (Jess)
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Biomechanics – Natural pivot point thus large mechanical loads – predominantly flexion, compression
(axial), rotational loading.
Pain sensitive structures – densely innervated soft tissues, connective tissue → ligaments,
fibrocartilage, nerve tissue - dura = capacity for local / somatic pain.
Proximity of primary anatomical ‘drivers’ of pain to nerve rootlets, roots, mixed nerves = capacity for
referred / radicular pain
Bogduk N, Spine 1983: Nerve supply to potential sources of pain:
 The lumbar intervertebral discs are innervated posteriorly by the sinuvertebral nerves,
 but laterally by branches of the ventral rami and grey rami communicantes.
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The posterior longitudinal ligament is innervated by the sinuvertebral nerves
and the anterior longitudinal ligament by branches of the grey rami.
Lateral and intermediate branches of the lumbar dorsal rami supply the iliocostalis lumborum and
longissimus thoracis, respectively.
Medial branches supply the multifidus, intertransversarii mediales, interspinales, interspinous
ligament, and the lumbar zygapophysial joints.
The distribution of the intrinsic nerves of the lumbar vertebral column systematically identifies those
structures that are potential sources of primary low-back pain.
Dural nerve supply:
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See PDF on WIKI
Lumbar facet pain: biomechanics, neuroanatomy and neurophysiology.
Cavanaugh JM, Ozaktay AC, Yamashita HT, King AI.
Source: Wayne State University, Bioengineering Center Detroit, MI 48202, USA.
Abstract
Idiopathic low back pain has confounded health care practitioners for decades. Although there has been much
advance in the understanding of the biomechanics of the lumbar spine over the past 25 years, the cellular and
neural mechanisms that lead to facet pain are not well understood. An extensive series of experiments was
undertaken to help elucidate these mechanisms and gain a better understanding of lumbar facet pain.
Biomechanic and neuroanatomic studies were performed in human cadaveric facet joints and neurophysiologic
studies were performed in New Zealand White rabbits. These studies provide the following evidence to help
explain the mechanisms of lumbar facet pain:
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The facet joint can carry a significant amount of the total compressive load on the spine when the
human spine is hyperextended.
(2) Extensive stretch of the human facet joint capsule occurs when the spine is in the physiologic range
of extreme extension.
(3) An extensive distribution of small nerve fibers and free and encapsulated nerve endings exists in
the lumbar facet joint capsule, including nerves containing substance P, a putative neuromodulator of
pain.
(4) Low and high threshold mechanoreceptors fire when the facet joint capsule is stretched or is
subject to localized compressive forces.
(5) Sensitization and excitation of nerves in facet joint and surrounding muscle occur when the joint is
inflamed or exposed to certain chemicals that are released during injury and inflammation.
(6) Marked reduction in nerve activity occurs in facet tissue injected with hydrocortisone and
lidocaine. Thus, the facet joint is a heavily innervated area that is subject to high stress and strain. The
resulting tissue damage or inflammation is likely to cause release of chemicals irritating to the nerve
endings in these joints, resulting in low back pain.
Good summary – interrelated causes.
Common Causes of Pain in the Lumbar Spine
There are many structures in the lumbar spine that can cause pain – any irritation to the nerve roots that exit
the spine, joint problems, the discs themselves, the bones and the muscles can all be a source of pain. Many
lumbar spine conditions are interrelated. For example, joint instability can lead to disc degeneration, which in
turn can put pressure on the nerve roots, etc.
The following outlines the more common causes of lower back pain.
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Muscular problems. The most common cause (doubtful statement) of lower back pain is muscle strain or
other muscle problems. Strain due to heavy lifting, bending, or other arduous or repetitive use can be quite
painful but usually heal within a few days to a few weeks.
Degenerative discs. Intervertebral discs are spongy pads that act as shock absorbers between each of the
lumbar spine’s vertebrae. As the disc degenerates, they can create pain in the disc space. This condition
can be referred to with many different terms – on this site it is consistently termed “degenerative disc
disease”.
Herniated disc. Herniated discs are most common in the lumbar spine. A herniated disc may happen
suddenly due to injury or heavy lifting or happen slowly as a part of general wear and tear on the spine.
Leg pain (sciatica) is the most common symptom of a herniated disc.
Sacroiliac joint dysfunction. The sacroiliac joint, which connects with the bottom of the lumbar spine and
the top of the tailbone, can cause lower back pain and/or sciatica pain if there is any type of dysfunction in
the joint that allows too much movement or restricts normal movement.
Spondylolisthesis. Spondylolisthesis occurs when one vertebra slips forward over the one below it. The
slip most commonly occurs in the lower lumbar vertebrae (e.g. L4 –L5 or L5 – S1). If the slipped vertebra
compresses the nerve root at that level, it can result in leg pain and possibly foot pain.
Osteoarthritis. Osteoarthritis in the lower back is sometimes called facet joint arthritis. Aging and wear
and tear can cause the normally smooth cartilage covering the facet joints in the back of the spine to
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become worn and frayed. Excess friction can produce bone spurs and joint swelling that cause tenderness,
pressure to the nerve, and limited range of motion.
Lumbar stenosis. The narrowing of the spinal canal or nerve root canals (gaps where the nerve endings
exit the spinal column) can cause the nerve endings to be squeezed, resulting in leg pain, tingling,
numbness and even difficulty walking. This narrowing is often the result of bone spurs and joint swelling
from osteoarthritis.
The sciatic nerve, which extends from the lower back down each leg to the foot, can become pinched or
irritated from any of the above conditions, often resulting in a burning pain and/or tingling sensation down
the back of the leg and possibly into the foot. The common term to describe this type of leg pain is sciatica.