ECA clinical examples chapter2 (Back) Flashcards
Abnormal Curvatures of VertebralColumn
Abnormal curvatures in some people result from developmental anomalies and in others from pathological processes such as osteoporosis (Fig. B2.1). Osteoporosis is characterized by a net demineralization of bones and results from a disruption of the normal balance of calcium deposition and resorption. The bones become weakened and brittle and are subject to fracture. Vertebral body osteoporosis occurs in all vertebrae but is most common in thoracic vertebrae and is an especially common finding in postmenopausal women.
Spina Bifida
The most common congenital anomaly of the vertebral column is spina bifida occulta, in which the laminae (embryonic neural arches) of L5 and/or S1 fail to develop normally and fuse. This bony defect, present in up to 24% of people, is concealed by skin, but its location is often indicated by a tuft of hair. Most people with spina bifida occulta have no back problems. In severe types of the anomaly, such as spina bifida cystica, one or more vertebral arches may almost completely fail to develop (Fig. B2.2). Spina bifida cystica is associated with herniation of the meninges (meningocele) and/or the spinal cord (meningomyelocele). Usually, neurological symptoms are present in severe cases of meningomyelocele (e.g., paralysis of limbs and disturbances in bladder and bowel control).
Laminectomy
A laminectomy is the surgical excision of one or more spinous processes and their supporting laminae (1 in Fig. B2.3). The term is also commonly used to denote the removal of most of the vertebral arch by transecting the pedicles (2 in Fig. B2.3). Laminectomies provide access to the vertebral canal to relieve pressure on the spinal cord or nerve roots, commonly caused by a tumor, herniated IV disc, or bony hypertrophy (excess growth).
Fractures of Vertebrae
Fractures and fracture–dislocations of the vertebral column usually result from sudden forceful flexion, as in an automobile accident. Typically, the injury is a crush or compression fracture of the body of one or more vertebrae. If violent anterior movement of the vertebra occurs in addition to compression, a vertebra may be displaced anteriorly on the vertebra inferior to it. Usually, this movement dislocates and fractures the articular facets between the two vertebrae and ruptures the interspinous ligaments. Irreparable injuries to the spinal cord accompany most severe flexion injuries of the vertebral column.
Fracture and Dislocation of Atlas
Vertical forces (e.g., striking the bottom of a pool in a diving accident) compressing the lateral masses between the occipital condyles and the axis drive them apart, fracturing one or both of the anterior or posterior arches (Fig. B2.4A, B). If the force is sufficient, rupture of the transverse ligament that links the lateral masses will also occur (Fig. B2.4A). The resulting Jefferson or burst fracture in itself does not necessarily result in spinal cord injury because the dimensions of the bony ring actually increase. Spinal cord injury is more likely, however, if the transverse ligament has also been ruptured.
Dislocation of Vertebrae
he bodies of the cervical vertebrae can be dislocated in neck injuries with less force than is required to fracture them. Because of the large vertebral canal in the cervical region, slight dislocation can occur without damaging the spinal cord; however, severe dislocations may injure the spinal cord. If the dislocation does not result in “facet jumping” with locking of the displaced articular processes, the cervical vertebrae may self-reduce (“slip back into place”) so that a radiograph may not indicate that the cord has been injured. Magnetic resonance imaging (MRI) may reveal the resulting soft tissue damage.
Severe hyperextension of the neck (whiplash injury) may occur during rear-end motor vehicle collisions, especially when the head restraint is too low or too far back. In these types of hyperextension injuries, the anterior longitudinal ligament is severely stretched and may be torn.
Dislocation of vertebrae in the thoracic and lumbar regions is uncommon because of the interlocking of their articular processes; however, owing to the abrupt transition from the relatively inflexible thoracic region to the much more mobile lumbar region, T11 and T12 are the most commonly fractured noncervical vertebrae.
Fractures of the interarticular parts of the vertebral laminae of L5 (spondylolysis of L5 [Fig. B2.5A, B]) may result in forward displacement of the L5 vertebral body relative to the sacrum (spondylolisthesis [Fig. B2.5C]). Spondylolysis of L5, or susceptibility to it, probably results from a failure of the centrum of L5 to unite adequately with the neural arches during development. Spondylolisthesis at the L5–S1 articulation may result in pressure on the spinal nerves of the cauda equina as they pass into the superior part of the sacrum, causing back and lower limb pain (Fig. B2.5C). The intrusion of the L5 body into the pelvic inlet reduces the anteroposterior diameter of the pelvic inlet.
Lumbar Spinal Stenosis
Lumbar spinal stenosis describes a stenotic (narrow) vertebral foramen in one or more lumbar vertebrae (Fig. B2.6). Stenosis of a lumbar vertebral foramen alone may cause compression of one or more of the spinal nerve roots occupying the vertebral canal. Surgical treatment may consist of decompressive laminectomy. Lumbar spinal stenosis may be a hereditary anomaly that can make a person more vulnerable to age-related degenerative changes such as IV disc protrusion. When IV disc protrusion occurs in a patient with spinal stenosis, it further compromises the size of the vertebral canal, as does arthritic proliferation and ligamentous degeneration. It should also be noted that lumbar spinal nerves increase in size as the vertebral column descends, but the IV foramina decrease in size.
Vertebral Body Osteoporosis
Vertebral body osteoporosis is a common metabolic bone disease that is often detected during routine radiographic studies. Osteoporosis results from a net demineralization of the bones caused by a disruption of the normal balance of calcium deposition and resorption. As a result, the quality of bone is reduced and atrophy of skeletal tissue occurs. Although osteoporosis affects the entire skeleton, the most affected areas are the neck of the femur, the bodies of vertebrae, the metacarpals (bones of the hand), and the radius. These bones become weakened and brittle and are subject to fracture.
Radiographs taken during early to moderate osteoporosis demonstrate demineralization, which is evident as diminished radiodensity of the trabecular (spongy) bone of the vertebral bodies, causing the thinned cortical bone to appear relatively prominent (Fig. B2.7A, B). Osteoporosis especially affects the horizontal trabeculae of the trabecular bone of the vertebral body (see Fig. B2.9C). Consequently, vertical striping may become apparent, reflecting the loss of the horizontal supporting trabeculae and thickening of the vertical struts (Fig. B2.7A). Radiographs in later stages may reveal vertebral collapse (compression fractures) and increased thoracic kyphosis (Fig. B2.7C). Vertebral body osteoporosis occurs in all vertebrae but is most common in thoracic vertebrae and is an especially common finding in postmenopausal females.
Herniation of Nucleus Pulposus
Herniation or protrusion of the gelatinous nucleus pulposus into or through the anulus fibrosus is a well-recognized cause of low back and lower limb pain. If degeneration of the posterior longitudinal ligament and wearing of the anulus fibrosus has occurred, the nucleus pulposus may herniate into the vertebral canal and compress the spinal cord or nerve roots of spinal nerves in the cauda equina (Fig. B2.8). Herniations usually occur posterolaterally, where the anulus is relatively thin and does not receive support from the posterior or anterior longitudinal ligaments. A posterolateral herniation is more likely to be symptomatic because of the proximity of the spinal nerve roots.
Rupture of Transverse Ligament ofAtlas
When the transverse ligament of the atlas ruptures, the dens is set free, resulting in atlantoaxial subluxation or incomplete dislocation of the median atlantoaxial joint. When complete dislocation occurs, the dens may be driven into the upper cervical region of the spinal cord, causing quadriplegia (paralysis of all four limbs), or into the medulla of the brainstem, causing death.
Rupture of Alar Ligaments
The alar ligaments are weaker than the transverse ligament of the atlas. Consequently, combined flexion and rotation of the head may tear one or both alar ligaments. Rupture of an alar ligament results in an increase of approximately 30% in the range of movement to the opposite side.
Aging of Vertebrae and IntervertebralDiscs
During middle and older age, there is an overall decrease in bone density and strength, particularly centrally within the vertebral body, that results in the superior and inferior surfaces of the vertebrae becoming increasingly concave (Fig. B2.9). The nuclei pulposi dehydrate and lose elastin and proteoglycans while gaining collagen. As a result, the IV discs lose their turgor, becoming stiffer and more resistant to deformation. The lamellae of the anulus thicken and often develop fissures and cavities. Although the margins of adjacent vertebral bodies approach more closely as the superior and inferior surfaces of the body become concave, it has been shown that the IV discs increase in size with age (Fig. B2.9B, C). Not only do the IV discs become increasingly convex but also, between the ages of 20 and 70 years, their diameter increases (Bogduk, 2012). Aging of the IV discs, combined with the changing shape of the vertebrae, results in an increase in compressive forces at the periphery of the vertebral bodies where the discs attach. In response, osteophytes (bony spurs) commonly develop around the margins of the vertebral bodies (Fig. B2.9A, B, D).
Injury and Disease of ZygapophysialJoints
When the zygapophysial joints are injured or develop osteophytes during aging (osteoarthritis), the related spinal nerves are often affected. This causes pain along the distribution pattern of the dermatomes and spasm in the muscles derived from the associated myotomes (a myotome consists of all the muscles or parts of muscles receiving innervation from one spinal nerve). Denervation of lumbar zygapophysial joints is a procedure that may be used for treatment of back pain caused by disease of these joints. The nerves are sectioned near the joints or are destroyed by radiofrequency percutaneous rhizolysis (root dissolution) (Fig. B2.10). The denervation process is directed at the articular branches of two adjacent posterior rami of the spinal nerves because each joint receives innervation from both the nerve exiting that level and the superjacent nerve.
Back Pain
Back pain in general, and lower back pain in particular, is an immense health problem. In terms of health factors causing lost workdays, backache is second only to headache.
Five categories of structures receive innervation in the back and can be sources of pain:
*Fibroskeletal structures: periosteum, ligaments, and anuli fibrosi of IV discs
*Meninges: coverings of the spinal cord
*Synovial joints: capsules of the zygapophysial joints
*Muscles: intrinsic muscles of the back
*Nervous tissue: spinal nerves or nerve roots exiting the IV foramina
Of these, the first two are innervated by (recurrent) meningeal branches of the spinal nerves and the next two are innervated by posterior rami (articular and muscular branches). Pain from nervous tissue—that is, caused by compression or irritation of spinal nerves or nerve roots—is typically referred pain, perceived as coming from the cutaneous or subcutaneous area (dermatome) supplied by that nerve, but it may be accompanied by localized pain.
Localized lower back pain (LBP) (pain perceived as coming from the back) is generally muscular, joint, or fibroskeletal pain. Muscular pain is usually related to reflexive cramping (spasms) producing ischemia, often secondarily as a result of guarding (contraction of muscles in anticipation of pain). Zygapophysial joint pain is generally associated with aging (osteoarthritis) or disease (rheumatoid arthritis) of the joints. Pain from vertebral fractures and dislocations is no different than that from other bones and joints: The sharp pain following a fracture is mostly periosteal in origin, whereas pain from dislocations is ligamentous. The acute localized pain associated with an IV disc herniation emanates from the disrupted posterolateral anulus fibrosis and impingement on the posterior longitudinal ligament. Pain in all of these latter instances is conveyed initially by the meningeal branches of the spinal nerves.
Ischemia of Spinal Cord
The segmental reinforcements of blood supply from the segmental medullary arteries are important in supplying blood to the anterior and posterior spinal arteries. Fractures, dislocations, and fracture–dislocations may interfere with the blood supply to the spinal cord from the spinal and medullary arteries. Deficiency of blood supply (ischemia) of the spinal cord affects its function and can lead to muscle weakness and paralysis.
The spinal cord may also sustain circulatory impairment if the segmental medullary arteries, particularly the great anterior segmental medullary artery (of Adamkiewicz), are narrowed by obstructive arterial disease. Sometimes, the aorta is purposely occluded (“cross-clamped”) during surgery. Patients undergoing such surgeries, and those with ruptured aneurysms of the aorta or occlusion of the great anterior segmental medullary artery, may lose all sensation and voluntary movement inferior to the level of impaired blood supply to the spinal cord (paraplegia). This is secondary to death of neurons in the part of the spinal cord supplied by the anterior spinal artery.
When systemic blood pressure drops severely for 3 to 6 minutes, blood flow from the segmental medullary arteries to the anterior spinal artery supplying the midthoracic region of the spinal cord may be reduced or stopped. These patients may also lose sensation and voluntary movement in the areas supplied by the affected level of the spinal cord.
