Neuromechanics of idiopathic scoliosis

Last updated
X-ray image of an Idiopathic scoliosis Wiki pre-op.jpg
X-ray image of an Idiopathic scoliosis

The neuromechanics of idiopathic scoliosis is about the changes in the bones, muscles and joints in cases of spinal deformity consisting of a lateral curvature scoliosis and a rotation of the vertebrae within the curve, that is not explained by either congenital vertebral abnormalities, or neuromuscular disorders such as muscular dystrophy. The idiopathic scoliosis accounts for 80–90% of scoliosis cases. Its pathogenesis is unknown. [1] However, changes in the vestibular system, [2] a lateral shift of the hand representation and abnormal variability of erector spinae motor map location in the motor cortex may be involved in this disease. [3] A short spinal cord and associated nerve tensions has been proposed as a cause and model for idiopathic scoliosis. [4] [5] Besides idiopathic scoliosis being more frequent in certain families, it is suspected to be transmitted via autosomal dominant inheritance. Estrogens could also play a crucial part in the progression of idiopathic scoliosis through their roles in bone formation, growth, maturation and turnover. Finally, collagen, intervertebral disc and muscle abnormalities have been suggested as the cause in idiopathic scoliosis, although these are perhaps results rather than causes. [6]

Contents

Demographic data

The patient's age at presentation of scoliosis, the remaining growth, the menarche status and the magnitude of the curve are used to foresee the idiopathic scoliosis curve progression. However, the relative importance of each factor and how they may interact is not clearly defined. [7] The earlier the scoliosis appears, the more likely it will progress. Though it is recommended that idiopathic scoliotic people should practice a sport for aerobic exercise and development of a positive body image, [8] practice of a sport at a competitive level is to be avoided.

Age

Idiopathic scoliosis can appear at different ages. Infantile idiopathic scoliosis that appear from the birth to 3 years old, account for 0.5% of idiopathic scoliosis. Juvenile idiopathic scoliosis that appear from the 4 to 10 years old, account for 10.5% of idiopathic scoliosis. Adolescent idiopathic scoliosis that appear after the age of 10 years, account for 89% of idiopathic scoliosis. [9] From these statistics, it seems that individuals are at highest risk of developing idiopathic scoliosis during adolescence.

Physical activity level

Because scoliotic people have higher joint laxity compared to non-scoliotic people, they are drawn toward gymnastics but the practice of gymnastics for less than 20 hours training per week does not cause scoliosis. Based on populations that had more than 20 hours training per week, idiopathic scoliosis has been observed among 10% of tennis players, 16% of young swimmers [10] and 24% in professional ballet companies. [11] The exposure of the body to high repetitive mechanical constraints may influence the occurrence of idiopathic scoliosis.

Physiology

Cobb angle measurement of a scoliosis; concave side on the left; convex side on the right Scoliosis cobb.svg
Cobb angle measurement of a scoliosis; concave side on the left; convex side on the right
Vertebra and curves of the vertebral column Illu vertebral column.svg
Vertebra and curves of the vertebral column

Cobb angle is a common measure to classify scoliosis. The greater the angle, the more serious is the disease but the smaller is the number of patients. One to three out of every hundred people have idiopathic scoliosis curves greater than 10° with an equal proportion of boys and girls. One to three out of every thousand people have idiopathic scoliosis curves greater than 30° with a ratio of eight girls for every one boy. [12]

Scoliosis is also classified according to the region(s) they affect. The vertebral column can be deformed at the thoracic level, at the lumbar level or at both. In the lumbar region, scoliosis induces perturbations to standing balance. The thoracic region is the location that most impacts movement strategies. [13] Scoliosis impedes on the movement of the ribs, places the respiratory muscles at a mechanical disadvantage and displaces the various organs of the thoracic cavity. [14]

Skeleton

In a scoliotic patient, the vertebral column experiences extension forces on the convex side and compression forces on the concave side. At the apical vertebra, average bone density for the concave cortical bone is higher than for the convex cortical bone, and cancellous bone density is higher for the concave side than for the convex side. [15] The concave side of a vertebra is less porous and has a thicker cortical bone than the convex side, which is consistent with Wolff's law about bone remodeling. [16]

Muscle

Scoliotic adolescents, at the apex vertebra, have a higher muscle activity (as measured by surface electromyography) on the convex side than on the concave side in sitting or standing conditions. [17] Because in scoliotic people wearing a brace, the muscle activity of the erector spinae muscles decreased on the convex side when walking with the brace [18] and because after spinal arthrodesis surgery, idiopathic scoliotic people showed a significant decrease in paravertebral muscle activity on the convex side but not on the concave side, [19] the muscular asymmetry in idiopathic scoliosis is thought to be a biomechanical consequence of the scoliotic curvature rather than its cause.

Effects on movement

Planes
Human anatomy planes.jpg
The main anatomical planes of the human body, including median (red), parasagittal (yellow), frontal or coronal plane (blue) and transverse or axial plane (green).
Anatomical terminology

Since idiopathic scoliosis and its surgery affect the vertebrae and the joints along the spine, the range of motion is expected to be different between patients and non-scoliotic people. There is a hypothesis that states that the vertebral column behaves like a torsional spring: while walking, the angular momentum of the shoulders compensates the angular momentum of the pelvis (i.e. when the shoulders rotate clockwise, the pelvis rotates counterclockwise; when the pelvis rotates clockwise, the shoulders rotate counterclockwise). [20] As scoliosis perturbs the architecture of the shoulders, spine and pelvis, gait also differs between patients and non-scoliotic people.

Range of motion

Independently of the Cobb angle, the affected vertebra and the age, idiopathic scoliotic people have a larger rachis flexion range of motion and a narrower hips extension range of motion than non-scoliotic people. The range of motion for rachis extension, hips flexion, left and right lateral flexions are similar to non-scoliotic people.

After arthrodesis, all rachis ranges of motion decrease because of surgery but hips extension range of motion is comparable to the one of non-operated scoliotic people. [21]

Gait

In terms of gait, while walking at a constant speed of 4 km/h for a few minutes until a steady state is reached, relative to non-scoliotic people, idiopathic scoliotic people have a frontal (i.e. coronal) pelvis, hip, and shoulder, transversal hip and sagittal knee motion restriction. The step length is reduced and the stance phase duration is also reduced. [22]

Surgical treatment of thoracolumbar/lumbar adolescent idiopathic scoliosis, whether performed with anterior spinal fusion or posterior spinal fusion arthrodesis, results in overall positive changes that lead to partial normalization of some gait parameters. After surgery, a slight reduction of trunk rotation, a decrease in shoulder rotation, an increase in frontal motion of pelvic and hips (pelvic tilt and hip abduction) are observed and no changes occurred in lower extremities during gait (knee and ankle). [23]

Related Research Articles

Scoliosis Medical condition of the spine

Scoliosis is a medical condition in which a person's spine has a sideways curve. The curve is usually "S"- or "C"-shaped over three dimensions. In some, the degree of curve is stable, while in others, it increases over time. Mild scoliosis does not typically cause problems, but more severe cases can affect breathing and movement. Pain is usually present in adults, and can worsen with age.

Sacrum Triangular-shaped bone at the bottom of the spine

The sacrum, in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30.

Spinal nerve Nerve that carries signals between the spinal cord and the body

A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.

Lumbar vertebrae Five vertebrae between the pelvis and the rib cage

The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process and by the absence of facets on the sides of the body. They are designated L1 to L5, starting at the top. The lumbar vertebrae help support the weight of the body, and permit movement.

Kyphosis Medical condition

Kyphosis is an abnormally excessive convex curvature of the spine as it occurs in the thoracic and sacral regions. Abnormal inward concave lordotic curving of the cervical and lumbar regions of the spine is called lordosis. It can result from degenerative disc disease; developmental abnormalities, most commonly Scheuermann's disease; Copenhagen disease, osteoporosis with compression fractures of the vertebra; multiple myeloma; or trauma. A normal thoracic spine extends from the 1st thoracic to the 12th thoracic vertebra and should have a slight kyphotic angle, ranging from 20° to 45°. When the "roundness" of the upper spine increases past 45° it is called kyphosis or "hyperkyphosis". Scheuermann's kyphosis is the most classic form of hyperkyphosis and is the result of wedged vertebrae that develop during adolescence. The cause is not currently known and the condition appears to be multifactorial and is seen more frequently in males than females.

Laminectomy

A laminectomy is a surgical procedure that removes a portion of a vertebra called the lamina, which is the roof of the spinal canal. It is a major spine operation with residual scar tissue and may result in postlaminectomy syndrome. Depending on the problem, more conservative treatments may be viable.

Spondylosis Degeneration of the vertebral column.

Spondylosis is the degeneration of the vertebral column from any cause. In the more narrow sense it refers to spinal osteoarthritis, the age-related wear and tear of the spinal column, which is the most common cause of spondylosis. The degenerative process in osteoarthritis chiefly affects the vertebral bodies, the neural foramina and the facet joints. If severe, it may cause pressure on the spinal cord or nerve roots with subsequent sensory or motor disturbances, such as pain, paresthesia, imbalance, and muscle weakness in the limbs.

Lordosis Medical condition

Lordosis is historically defined as an abnormal inward curvature of the lumbar spine. However, the terms lordosis and lordotic are also used to refer to the normal inward curvature of the lumbar and cervical regions of the human spine. Similarly, kyphosis historically refers to abnormal convex curvature of the spine. The normal outward (convex) curvature in the thoracic and sacral regions is also termed kyphosis or kyphotic. The term comes from the Greek lordōsis, from lordos.

Thoracic vertebrae

In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being much larger than the upper. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, as well as facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1–T12, with the first one (T1) located closest to the skull and the others going down the spine toward the lumbar region.

Spondylolisthesis Medical condition

Spondylolisthesis is the displacement of one spinal vertebra compared to another. While some medical dictionaries define spondylolisthesis specifically as the forward or anterior displacement of a vertebra over the vertebra inferior to it, it is often defined in medical textbooks as displacement in any direction. Spondylolisthesis is graded based upon the degree of slippage of one vertebral body relative to the subsequent adjacent vertebral body. Spondylolisthesis is classified as one of the six major etiologies: degenerative, traumatic, dysplastic, isthmic, pathologic, or post-surgical. Spondylolisthesis most commonly occurs in the lumbar spine, primarily at the L5-S1 level with the L5 vertebral body anteriorly translating over the S1 vertebral body.

Back brace

A back brace is a device designed to limit the motion of the spine in cases of bone fracture or in post-operative spinal fusiona, as well as a preventative measure against some progressive conditions or to correct patient posture.

Quadratus lumborum muscle

The quadratus lumborum muscle, informally called the QL, is a paired muscle of the left and right posterior abdominal wall. It is the deepest abdominal muscle, and commonly referred to as a back muscle. Each is irregular and quadrilateral in shape.

Spinal fusion Immobilization or ankylosis of two or more vertebrae by fusion of the vertebral bodies

Spinal fusion, also called spondylodesis or spondylosyndesis, is a neurosurgical or orthopedic surgical technique that joins two or more vertebrae. This procedure can be performed at any level in the spine and prevents any movement between the fused vertebrae. There are many types of spinal fusion and each technique involves using bone grafting—either from the patient (autograft), donor (allograft), or artificial bone substitutes—to help the bones heal together. Additional hardware is often used to hold the bones in place while the graft fuses the two vertebrae together. The placement of hardware can be guided by fluoroscopy, navigation systems, or robotics.

Spondylolysis Medical condition

Spondylolysis is a defect or stress fracture in the pars interarticularis of the vertebral arch. The vast majority of cases occur in the lower lumbar vertebrae (L5), but spondylolysis may also occur in the cervical vertebrae.

Kyphoscoliosis Medical condition

Kyphoscoliosis describes an abnormal curvature of the spine in both a coronal and sagittal plane. It is a combination of kyphosis and scoliosis. This musculoskeletal disorder often leads to other issues in patients, such as under-ventilation of lungs, pulmonary hypertension, difficulty in performing day-to-day activities, psychological issues emanating from anxiety about acceptance among peers, especially in young patients. It can also be seen in syringomyelia, Friedreich's ataxia, spina bifida, kyphoscoliotic Ehlers–Danlos syndrome (kEDS), and Duchenne muscular dystrophy due to asymmetric weakening of the paraspinal muscles.

Laminotomy

A laminotomy is an orthopaedic neurosurgical procedure that removes part of the lamina of a vertebral arch in order to relieve pressure in the vertebral canal. A laminotomy is less invasive than conventional vertebral column surgery techniques, such as laminectomy because it leaves more ligaments and muscles attached to the vertebral column intact and it requires removing less bone from the vertebra. As a result, laminotomies typically have a faster recovery time and result in fewer postoperative complications. Nevertheless, possible risks can occur during or after the procedure like infection, hematomas, and dural tears. Laminotomies are commonly performed as treatment for lumbar spinal stenosis and herniated disks. MRI and CT scans are often used pre- and post surgery to determine if the procedure was successful.

Sean E. McCance, M.D., is an American orthopedic surgeon and Co-Director of Spine Surgery in the Leni and Peter W. May Department of Orthopaedics at the Mount Sinai Medical Center in New York City. Additionally, he is Associate Clinical Professor of Orthopaedics at the Mount Sinai School of Medicine and Attending Spine Physician at Lenox Hill Hospital.

Vertebral column Bony structure found in vertebrates

The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord found in all chordates has been replaced by a segmented series of bone: vertebrae separated by intervertebral discs. Individual vertebrae are named according to their region and position, and can be used as anatomical landmarks in order to guide procedures such as lumbar punctures. The vertebral column houses the spinal canal, a cavity that encloses and protects the spinal cord.

Vertebra Bone in the vertebral column

The spinal column, characteristic of each vertebrate species, is a moderately flexible series of vertebrae, each constituting a characteristic irregular bone whose complex structure is composed primarily of bone, and secondarily of hyaline cartilage. They show variation in the proportion contributed by these two tissue types; such variations correlate on one hand with the cerebral/caudal rank, and on the other with phylogenetic differences among the vertebrate taxa.

The management of scoliosis is complex and is determined primarily by the type of scoliosis encountered: syndromic, congenital, neuromuscular, or idiopathic. Treatment options for idiopathic scoliosis are determined in part by the severity of the curvature and skeletal maturity, which together help predict the likelihood of progression. Non-surgical treatment should be pro-active with intervention performed early as "Best results were obtained in 10-25 degrees scoliosis which is a good indication to start therapy before more structural changes within the spine establish." Treatment options have historically been categorized under the following types:

  1. Observation
  2. Bracing
  3. Specialized physical therapy
  4. Surgery

References

  1. ↑ Estrogen receptor polymorphism, estrogen content and idiopathic scoliosis in human: A possible genetic linkage; T. Esposito, R. Uccello, R. Caliendo, G.F. Di Martino, U.A. Gironi Carnevale, S. Cuomo, D. Ronca, B. Varriale, 2009.
  2. ↑ Automatic MRI segmentation and morphoanatomy analysis of the vestibular system in adolescent idiopathic scoliosis; Lin Shi, Defeng Wang, Winnie C.W. Chu, Geoffrey R. Burwell, Tien-Tsin Wong, Pheng Ann Heng, Jack C.Y. Cheng, 2011.
  3. ↑ Cortical representation of hand and paraspinal muscles in patients with adolescent idiopathic scoliosis compared to healthy control; A. Szelényi, F. Geiger, M. Rauschmann, U. Ziemann, 2008.
  4. ↑ Roth, M. (May 1968). "Idiopathic scoliosis caused by a short spinal cord". Acta Radiologica: Diagnosis. 7 (3): 257–271. doi:10.1177/028418516800700308. ISSN   0567-8056. PMID   4883824. S2CID   28117855.
  5. ↑ Roth, M. (1981). "Idiopathic scoliosis from the point of view of the neuroradiologist". Neuroradiology. 21 (3): 133–138. doi:10.1007/bf00339521. ISSN   0028-3940. PMID   7231673. S2CID   25944250.
  6. ↑ Leboeuf, Dominique; Letellier, Kareen; Alos, Nathalie; Edery, Patrick; Moldovan, Florina (2009). "Do estrogens impact adolescent idiopathic scoliosis?". Trends in Endocrinology & Metabolism. 20 (4): 147–152. doi:10.1016/j.tem.2008.12.004. PMID   19349194. S2CID   23424172.
  7. ↑ The natural history of adolescent idiopathic scoliosis; Hee-Kit Wong, Ken-Jin Tan, 2010.
  8. ↑ Scientific exercises approach to scoliosis (SEAS): efficacy, efficiency and innovation; Michele Romano, Alessandra Negrini, Silvana Parzini, and Stefano Negrini, 2008.
  9. ↑ Pathogenesis of Idiopathic Scoliosis Revisited; William E. Stehbens, 2003.
  10. ↑ Scoliosis in swimmers; Becker, TJ, 1986.
  11. ↑ Why do idiopathic scoliosis patients participate more in gymnastics?; C. Meyer, E. Cammarata, T. Haumont, D. Deviterne, G. C. Gauchard, B. Leheup, P. Lascombes, Ph. P. Perrin, 2006.
  12. ↑ Scoliosis: Review of diagnosis and treatment; Joseph A Janicki, Benjamin Alman, 2007.
  13. ↑ Influence of different types of progressive idiopathic scoliosis on static and dynamic postural control; Gauchard G, Lascombes P, Kuhnast M, Perrin P, 2001.
  14. ↑ Scoliosis and the respiratory system; Anastassios C. Koumbourlis, 2006.
  15. ↑ Adam, C. & Askin, G. (2009). Lateral bone density variations in the scoliotic spine. Bone, (45). 799-807.
  16. ↑ A Comparison of the Microarchitectural Bone Adaptations of the Concave and Convex Thoracic Spinal Facets in Idiopathic Scoliosis; Kevin G. Shea, Tyler Ford, BS, Roy D. Bloebaum, Jacques D’Astous, and Howard King, 2004.
  17. ↑ A preliminary study on electromyographic analysis of the paraspinal musculature in idiopathic scoliosis; John Cheung, Jan P. K. Halbertsma, Albert G. Veldhuizen, Wim J. Sluiter, Natasha M. Maurits, Jan C. Cool, Jim R. van Horn, 2005.
  18. ↑ Investigation of gait of patients with idiopathic scoliosis and the influence of the Milwaukee brace on gait (author’s transl); Orthop Ihre Grenzgeb, Guth V, Abbink F, Gotze HG, Heinrichs W, 1978.
  19. ↑ Gait analysis in idiopathic scoliosis before and after surgery: a comparison of the pre and postoperative muscle activation pattern; Hopf C, Scheidecker M, Steffan K, Bodem F, Eysel P, 1998.
  20. ↑ An hypothesis for the role of the spine in human locomotion: A challenge to current thinking; S. Gracovetsky, 1985.
  21. ↑ Le mouvement de la colonne scoliotique à l’âge adulte, Range of motion of the scoliotic spine in adults; B. Biot, E. Clément, M. Lejeune, 2003.
  22. ↑ Gait in adolescent idiopathic scoliosis: kinematics and electromyographic analysis; P. Mahaudens, X. Banse, M. Mousny, C. Detrembleur, 2009.
  23. ↑ Gait in thoracolumbar/lumbar adolescent idiopathic scoliosis: effect of surgery on gait mechanisms; Philippe Mahaudens, C. Detrembleur, M. Mousny, X. Banse, 2010.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.