Lumbosacral Spine Acute Bony Injuries

Background

Injuries to the lumbar spine have received only a small amount of attention compared with other athletic injuries. This can be explained by a number of reasons. Spinal fractures are relatively uncommon in sports participation compared with other types of injuries; most injuries to the lumbar spine are relatively minor and fit into the category of soft-tissue injuries. These soft-tissue injuries are usually self-limited and resolve without coming to the attention of healthcare professionals.

The mechanisms and severity of sports-related lumbar spinal injuries reflect a competitive and risk-taking culture.[1, 2, 3, 4, 5, 6] Lumbar spine bony injuries are often limited to specific sports, most frequently seen in sports such as automobile or motorcycle racing,[7, 8, 9] skydiving[10] (see the image below), power weight lifting,[11, 12] wrestling,[13] gymnastics,[14, 15, 16] football,[17, 18, 19, 20, 21, 22] hockey,[23] rowing,[24] horseback riding,[25, 26] and high-speed snow sports.[27, 28, 29, 30, 31] This article reviews the diagnosis and management of acute lumbar vertebral fractures.

Sagittal computed tomography scan reconstruction of a young female who had a skydiving accident. The parachute deployed, but the patient landed on concrete and sustained a lower-extremity fracture and a fracture of L1. She was neurologically intact but required an open reduction with a fusion and instrumental fixation of the fracture.

For excellent patient education resources, see eMedicineHealth's patient education articles Vertebral Compression Fracture and Low Back Pain.

Related Medscape Reference topics:

Lumbar Disk Problems in the Athlete

Lumbar Spine Fractures and Dislocations

Lumbar Spine Trauma Imaging

Lumbosacral Disc Injuries

Lumbosacral Discogenic Pain Syndrome

Related Medscape resources:

Resource Center Exercise and Sports Medicine

Resource Center Joint Disorders

Resource Center Spinal Disorders

CME/CE Back Pain in a 39-Year-Old Man from Guatemala

CME Early Surgery for Severe Sciatica Relieves Pain Faster Than Conservative Treatment

CME/CE Low Back Pain: Evaluating Presenting Symptoms in Elderly Patients

NextEpidemiologyFrequencyUnited States

The epidemiology of thoracic and lumbar spine injuries in athletes is very difficult to document. Most epidemiologic studies on lumbar spine injuries in athletes lack prospective data. The thoracolumbar junction and lumbar spine are common sites for fractures due to the high mobility of the lumbar spine compared with the more rigid thoracic spine. Injury to the cord or cauda equina occurs in approximately 10-38% of adult thoracolumbar fractures and in as many as 50-60% of fracture dislocations. The rate of bony injury without neurologic consequence is undoubtedly higher.

In the United States, Keene reported an overall rate of 7% for sport-related lumbar injuries in the athlete population.[30] Most of these injuries occurred during practice or preseason conditioning, and only 6% occurred during actual competition. Lumbar spine injuries were significantly more common in football[17, 18, 19, 20] and gymnastics.[14, 15, 16]

Statistics from the US Air Force Academy indicated that 9% of all athletic injuries affect the spinal column. In an analysis of injuries in a professional football team, Ryan et al reported a 6% rate of spinal injuries.[9] Snook reviewed all musculoskeletal injuries sustained by college wrestlers and female gymnasts and found a rate of thoracolumbar spine injuries of 2% for the wrestlers[13] and 13% for the female gymnasts.[32]

Related Medscape Reference topics:

Cauda Equina and Conus Medullaris Syndromes

Lumbosacral Facet Syndrome

Lumbosacral Radiculopathy

Lumbosacral Spondylolisthesis

Lumbosacral Spondylolysis

Related Medscape resources:

Resource Center Exercise and Sports Medicine

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International

Information on the incidence of sports-related spinal injuries in other countries is also limited and difficult to determine due to differences in data collection and reporting among countries. In England, Williams estimated that spinal injuries accounted for 15% of all injuries sustained in sports.[10] Furthermore, injuries to the thoracic and lumbar spine seemed to be more frequent in automobile racing, horseback riding, parachuting, mountain climbing, and weightlifting.

PreviousNextFunctional Anatomy

The lumbar spine consists of a mobile segment of 5 vertebrae, located between the relatively immobile segments of the thoracic and sacral segments at either end. The thoracic spine is stabilized by the attached rib cage and intercostal musculature, whereas the sacral segments are fused, providing a stable articulation with the ilium. The lumbar vertebrae are particularly large and heavy compared with the cervical and thoracic vertebrae. The bodies are wider, the pedicles are shorter and heavier, and the transverse processes project somewhat more laterally and ventrally when compared with other spinal segments. The laminae are shorter vertically than the bodies and are bridged by strong ligaments. Finally, the spinal processes are broader and stronger than those in the thoracic and cervical spine.[33]

The lumbar spine must transmit compressive, bending, and twisting forces that are generated between the upper and lower body. Consequently, as one moves more caudally into the lumbar spine, the muscle groups and ligaments become larger and stronger.

The intervertebral discs consist of 2 components, the annulus fibrosus and the nucleus pulposus. The annulus is a dense fibrous ring located at the periphery of the disc, which has strong attachments to the vertebrae and serves to confine the nucleus pulposus. The lumbar spine is surrounded by powerful musculature and ligaments, which dynamically stabilize the spine.

Related Medscape Reference topic:

Topographic and Functional Anatomy of the Spinal Cord

PreviousNextSport-Specific Biomechanics

The lumbar spine is a complex, 3-dimensional (3-D) structure that is capable of flexion, extension, lateral bending, and rotation. In the spine, the total range of motion is the result of a summation of the limited movements that occur between the individual vertebrae. Strong muscles and ligaments are crucial for supporting the bony structures and for initiating and controlling movement.

The most common movement of the lumbar spine is flexion. During flexion, anterior compression of the intervertebral disc and widening of the spinal canal occurs along with some sliding movement of the articular process in the zygapophyseal joint. This movement is limited by the posterior ligamentous complex and the dorsal muscles. Extension of the lumbar spine is more limited, producing posterior compression on the disc, narrowing of the spinal canal, and a sliding motion of the zygapophyseal joint. The anterior longitudinal ligament, ventral muscles, lamina, and spinous processes limit the extension of the lumbar spine.

Lateral bending involves lateral compression of the intervertebral disc, along with sliding separation of the zygapophyseal joint on the convex side. An overriding of the zygapophyseal joint occurs on the concave side. The intertransverse ligaments limit the lateral bending of the spine. Rotation of the lumbar spine involves compression of the annulus fibrosus fibers. It is limited by the geometry of the facet joints and the iliolumbar ligaments. The motion of the lumbar spine cannot be considered without evaluating the synchronous movements of the cervical and thoracic spine. The entire spinal column moves as one unit in all planes of motion. Each region of the spine has its own characteristic curvature. These curves allow an upright posture while maintaining the center of gravity over the pelvis and lower limbs. Although most rotation is accomplished at the cervical spine, flexion and lateral bending are primarily cervical and lumbar functions.

Spinous process fractures may occur as a result of direct trauma to the posterior spine or as a result of forcible flexion and rotation. These injuries are usually not associated with neurologic deficits. Violent muscular contraction or direct trauma can cause fractures of the transverse processes. For example, a football helmet blow to the back can cause fractures of either the spinous or transverse processes. Burst fractures (see the images below) are usually associated with axial loading and compression of the spine. Acute traumatic spondylolisthesis is usually associated with major trauma and extreme hyperextension of the spine.

Sagittal T1-weighted magnetic resonance imaging study of a professional driver who was in a rollover motor vehicle accident while racing his car. This figure shows a T-10 unstable burst fracture producing severe kyphotic deformity of the spine. The abnormal signal on the vertebral body and the extradural defect represents a subacute hematoma producing spinal cord compression. The patient had severe paraparesis and underwent an emergency operation. The procedure involved an anterolateral retroperitoneal approach with a corpectomy and vertebral reconstruction. Postoperative plain x-ray film of a professional driver who experienced a burst fracture in a rollover motor vehicle accident while racing his car. This image shows a vertebral reconstruction with the use of a titanium cage filled with bone and the arthrodesis with a Z plate. Sagittal computed tomography scan reconstruction of an athlete who had a burst fracture.

The intervertebral discs are thick and strong. The annulus fibrosus receives most of the forces that are transmitted from one vertebral body to another, and it is designed to resist tension and shearing forces. The nucleus pulposus is designed to resist compression forces; it receives primarily vertical forces from the vertebral bodies and redistributes them in a radial fashion to the horizontal plane. This structure allows the intervertebral discs to dissipate the axial loading.

Related Medscape Reference topics:

Disk Herniation Imaging

Herniated Nucleus Pulposus

Lumbar Compression Fracture

Lumbosacral Spine Sprain/Strain Injuries

Lumbosacral Spondylolisthesis

Lumbosacral Spondylolysis

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Resource Center Spinal Disorders

Specialty Site Neurology & Neurosurgery

Specialty Site Orthopaedics

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Cervical Spine Acute Bony Injuries in Sports Medicine

Background

Cervical spine fractures lead to substantial morbidity and mortality. Neck injury in athletes can quickly end or change the future of an athlete. Failure to properly recognize and provide early care in cervical spine fracture cases may lead to devastating complications.[1, 2, 3, 4]

A C3 spinous fracture is depicted in the image below.

Lateral view of a C3 spinous fracture.

For patient education resources, see the Back, Ribs, Neck, and Head Center, as well as Neck Strain, Vertebral Compression Fracture, and Whiplash.

NextEpidemiologyFrequencyUnited States

The incidence of all spinal injuries in the United States has been reported at approximately 10,000 cases per year. Nearly 200,000 people in the United States have a history of spinal injuries. These statistics do not differentiate between injuries with fracture and injuries without fracture.[5, 6, 7]

Sports-related activities represent 10-15% of these injuries, and spinal injuries represent 2-3% of all sports-related injuries. Certain sports (eg, American football, diving, gymnastics, skiing, wrestling, rugby, hang gliding, surfing, equestrian events) are more frequently associated with the risk of spinal trauma.[2, 3, 4, 6, 7, 8, 9, 10, 11, 12]

The most common spinal injuries cited in the literature are injuries secondary to contact sports such as football. Nearly 1.2 million high school athletes and 200,000 college and professional athletes participate in football. The National Football Head and Neck Injury Registry contains data on cervical spine injuries as a result of participation in football. A trend can be seen over time, as equipment and helmets improved. The incidence of cervical spine injuries increased until 1976. In that year, antispearing rules were established to prevent the athlete from using the helmet as driving force in tackles. Direct collision created higher axial loads than the neck could withstand, leading to high injury rates. This rule, along with better coaching of blocking and tackling techniques, has resulted in a significant decrease in the number of spinal injuries.[10]

Diving is often cited as another significant cause of cervical spine injuries. Injuries resulting from diving are often associated with devastating outcomes. Diving rules (eg, depth of starting areas) and proper technique have lowered the probability of injury during supervised athletic events. However, unsupervised swimming and diving into shallow water present significant risks. Public awareness of this problem has led to the development of special awareness programs, but the risk of injury remains high.

PreviousNextFunctional Anatomy

The human spine serves to provide structural support and bony protection of the spinal cord. The cervical spine consists of 7 bony vertebrae separated by flexible intervertebral discs. They are joined together by an intricate network of ligaments, which helps form the normal lordotic curve of the cervical neck.[13]

The spinal column can be divided into 2 separate columns based on function and injury patterns. The anterior column consists of the bodies of the vertebrae, intervertebral discs, and the anterior and posterior longitudinal ligaments. The function of the vertebral body is to support weight. The posterior column contains the spinal canal and consists of the pedicles, laminae, articulating facets, and transverse and spinous processes. These structures form the vertebral arch, which encloses the vertebral foramen and protects the neural tissues.

The arch is formed by bilateral pedicles that are oriented posteriorly and join 2 laminae. The spinous process arises posteriorly from the vertebral arch. The cervical transverse processes and 4 articular processes also arise from the arch. The cervical transverse processes are unique to the vertebral column with an oval foramen transversarium. The vertebral arteries pass through these foramina. The posterior column also includes a group of ligaments including the supraspinous, infraspinous, interspinous, and nuchal ligaments.

The first 2 cervical vertebrae are atypical in form and function. The next 5 vertebrae are all similar in structure and function. The atlas, C1, is a ring-shaped bone that supports the skull. Two concave, superior articular facets articulate with the occipital condyles. The atlas does not have a body or spinous process. The atlas has an anterior and posterior arch, each with a tubercle and lateral mass. The axis, C2, is the strongest cervical vertebrae. The atlas rotates on 2 large articulating surfaces. The odontoid process (dens) projects superiorly from the C2 body and is the bony structure that the atlas rotates on. The odontoid process is held in place by the transverse ligament of the atlas.

PreviousNextSport-Specific Biomechanics

Contact sports, falls, and diving in sports may lead to vertebral stress and fractures. Sports that involving tackling can increase exposure to mechanisms causing fractures.

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Cervical Spine Sprain/Strain Injuries

Background

The most frequent cervical injuries in athletes are probably acute strains and sprains of the musculature of the neck, as well as soft-tissue contusions.

A strain refers to an injury to a muscle, occurring when a muscle-tendon unit is stretched or overloaded. Cervical muscles that are commonly strained include the sternocleidomastoid (SCM), the trapezius, the rhomboids, the erector spinae, the scalenes, and the levator scapulae.

A sprain refers to a ligamentous injury, and the diagnosis of cervical sprain implies that the ligamentous and capsular structures connecting the cervical facet joints and vertebrae have been damaged. Practically, a cervical sprain may be difficult to differentiate from a strain, and the 2 injuries often occur simultaneously. Pain referred to the muscle can arise from any source that is modulated by the dorsal rami.

Numerous epidemiologic studies have been completed in the hopes of identifying the injury risk patterns that are associated with specific sports. Many athletes are reluctant to report minor injuries, and because the overwhelming numbers of sports-related spinal injuries are self-limited and resolve before being reported, the accuracy of these studies has been challenged. The mainstay of prevention and treatment of cervical spine injuries is maintaining good strength and flexibility through conditioning.

For excellent patient education resources, visit eMedicineHealth's First Aid and Injuries Center. Also, see eMedicineHealth's patient education articles Neck Strain, Sprains and Strains, Muscle Strain, and Whiplash.

Related Medscape Reference topics include the following:

Atlantoaxial Injury and DysfunctionCervical Disc DiseaseCervical Spine Injuries in SportsNextEpidemiologyFrequencyUnited States

Cervical spine injuries occur in an estimated 10-15% of football players, most commonly in defensive ends, linemen, and linebackers.[1, 2] The reinjury rate in high school football players following all cervical spine injuries is reported at 17.2%. Football players with 2 previous injuries are reported as having an 87% risk of reinjury. Wrestlers with no history of injuries to the neck have a 20% chance of sustaining a neck injury in a given year[3] ; however, wrestlers who have had a previous neck injury have an approximate 50% chance of recurrence.

Sporting accidents are second only to motor vehicle accidents as the leading cause of emergency department visits involving neck injuries, and as more people participate in athletic activity, the incidence of cervical injuries can be expected to rise as well.[4, 5]

PreviousNextFunctional Anatomy

The spinal cord is protected by the cervical spine, which provides support for the head and allows for a significant amount of range of motion (ROM).[6, 7] Seven cervical vertebrae, stacked vertically, comprise the skeletal portion of the spine. Each vertebra (except C1 and C2) has a common body anteriorly and a ring of bone formed by the laminae and pedicles posteriorly. This protective ring of bone forms the spinal canal, which surrounds and protects the spinal cord. The tissues that surround the cord and the spinal fluid fill the remaining space. The C1 vertebra, or atlas, is ring-shaped, has large lateral masses, and attaches to the occipital condyles of the skull, providing support. See the images below.

Bony framework of head and neck. Cervical vertebrae, the atlas and the axis. Cervical vertebrae. Atlantooccipital junction.

The transverse ligament lies anteriorly between the 2 lateral masses of C1 and just posteriorly to the odontoid process of the C2 vertebra, or axis (see the image below). Projecting upward from the body of C2, the odontoid process is contained between the anterior arch of C1 and the transverse ligament. Displacement of C1 and C2 may be associated with rupture of this ligament, which may result in a spinal cord injury.

Internal craniocervical ligaments.

The remaining cervical vertebrae (C3-C7) are similar in function and appearance. The ovoid vertebral bodies are wider than they are tall. The bilateral raised uncinate processes located posterolaterally correspond to similar beveled surfaces on the inferior aspect of the superior vertebral body. These joints of Luschka, also known as uncovertebral joints, are not present in the embryologic development of the cervical spine but arise as a result of the degenerative and adaptive changes of annular tissue to stresses and loads.

The cervical zygapophyseal joints are synovial in nature. Their articular surfaces are covered with hyaline cartilage, and their fibrous capsules are lined with synovium. The orientation of the cervical zygapophyseal joints allows them to play a weight-bearing role and to provide resistance to anterior translation. Because the C2-C3 facet sits between the upper and lower parts of the cervical spine that move differently, it is considered transitional anatomically and biomechanically.[7]

The lower cervical spine flexes and extends, and the atlantoaxial joint moves in rotation. During lateral bending, the spinous processes move to the convexity of the curve (spinous processes move to the right during left lateral bending) in the middle and lower cervical regions. Coupled lateral bending occurs in the opposite direction to the applied axial rotation above the C2-C3 level. Lateral bending from C2-C3 distally is always coupled with rotation in the same direction because of the approximate 45° inclination of the cervical zygapophyseal joints. The obliquity of the articular surfaces in the frontal plane determines the relative amount of side bending or rotation that occurs. The more vertical the joint surface, the more side bending is coupled; the more horizontal the joint surface, the more rotation is coupled.

Regressive changes occur in cervical zygapophyseal menisci with age. The meniscus retracts and narrows between childhood and the fourth decade of life. The meniscus helps increase the contact surface area when articular facets come together, thus helping to transmit some of the load.

The many articulations between the cervical vertebrae make the extensive ROM in the cervical spine possible. However, this large ROM comes at the cost of stability. Cervical spine stability is provided by a combination of the zygapophyseal joints and numerous ligaments and muscles. Extension, flexion, lateral bending, and rotation are permitted by the orientation of the zygapophyseal joints and ligaments. Positioning of the head makes combinations of these motions necessary. In a young person, cervical flexion and extension is about 100°. Bilateral rotation is about 80°, with approximately 50% of this range occurring between C1 and C2. The range of lateral bending is about 30-50°. Older individuals usually have reduced end ROMs because cervical mobility usually decreases with age.

Intervertebral discs are located in between each of the cervical vertebrae from C2-C7. These discs consist of a water-containing central portion, the nucleus pulposus, and a tough fibrous outer ring, the annulus fibrosis. The discs are subject to prolonged and repetitive loading from muscle forces acting across them and from the weight of the head. With their viscous central portion, the intervertebral discs are able to transmit these forces between the end plates of adjacent vertebral bodies. These biconvex discs conform to the concavity of the vertebral bodies, and they also contribute to normal cervical lordosis because they are thicker anteriorly. Only the outer one third to one half of the annulus fibrosis in adults receives a vascular supply. The rest of the annulus and the whole nucleus pulposus are avascular.

The annular fibers consist of 10-20 circumferential collagenous lamellae. The fibers within each lamella are oriented 35° from the horizontal, although the direction of inclination alternates with each lamella. As a result, rotation and translation are more likely to damage the annulus because resistance can be offered only by half of the lamellae whose fibers are oriented in the direction of motion.

The functions of a ligament are: (1) to provide stability to the joint, (2) to absorb energy during trauma, and (3) to act as a joint position transducer during physiologic motions. Ligaments, along with the paracervical muscles in the cervical spine, prevent motion between vertebrae that might injure the spinal cord or nerve roots. The cervical spine ligaments have numerous and complex interrelationships (see the images below).

External craniocervical ligaments. Internal craniocervical ligaments.

Running vertically along the anterior and posterior aspects of the vertebral bodies, the anterior and posterior longitudinal ligaments attach to the discs as well. The tightly attached posterior longitudinal ligament is thick in its central portion, which helps prevent a disc herniation from pressing directly on the cord posteriorly. The interspinous ligaments are also located posteriorly but are not as well developed in the cervical region.

The ligamentum flavum, a yellowish elastic membrane, overlies the space between the laminae of adjacent vertebrae and the neural arches. The posterior location of the ligamentum flavum helps to restrain hyperflexion. The ligamentum flavum becomes shortened and thicker in hyperextension and elongated and thinner in hyperflexion. During hyperextension, it may protrude into the cervical canal as much as 3.5 mm. Impingement on the spinal cord during extension is normally prevented by the elastic properties of the ligament; however, hypertrophy of the ligamentum flavum or loss of elasticity through degeneration may lead to canal narrowing or cord impingement.

The capsular ligaments, oriented approximately orthogonal to the articular facets, provide maximal mechanical efficiency in resisting distraction of the facets but relatively poor resistance to shear. The posterior longitudinal ligament limits flexion and distraction, the tectorial membrane limits flexion and extension, and the supraspinous and interspinous ligaments limit flexion and anterior horizontal displacement.

The main function of the alar ligaments is to restrain rotation. The alar ligaments originate from the posterolateral aspect of the dens of C2 and insert on the medial surfaces of the occipital condyles. When a single alar ligament is cut, axial rotation increases significantly to both sides; thus, both ligaments are required to be intact for restraining motion. Alar ligaments are stretched the most when the head is rotated and flexed together, and the ligaments are relaxed during extension. The anterior aspect of the transverse ligament acts as the pivot about which C1 (ie, the atlas) rotates.

Holding the odontoid process of C2 against the anterior ring of the atlas, the transverse ligament functions as a restraining band on the dens. Flexion and anterior displacement of the atlas is restrained by its orientation. The facet joint capsules are strong fibrous structures that contribute to posterior stability.

A muscle injury or reaction of some degree is associated with almost every cervical injury. The musculature of the neck is vulnerable to the same types of injuries that affect muscles elsewhere in the body. The role of the muscles is to stabilize the spine, carry loads, and produce motion. The action of the intervertebral muscle forces is to restore the intervertebral motions of an injured spine to its intact values.

The capital flexor muscles include the following:

Longus capitisRectus capitis anterior and lateralSuprahyoid and hyoid muscles

The capital extensor muscles include the following:

Splenius capitisSemispinalis capitisLongissimus capitisObliquus capitis inferior and superiorRectus capitis posterior major and minor

The cervical flexor muscles include the following:

Anterior scaleneMiddle scaleneSCM

The cervical extensor muscles include the following:

Semispinalis cervicisLongissimus cervicisSplenius cervicis

Because the bulk of the flexor muscle groups are at the C4-C5 level and the main mass of the extensor muscle groups overlies the C6-T1 levels as well as the atlantoaxial area, these muscle groups are likely sites of major stresses. The muscle groups that laterally flex and rotate the cervical spine include the following:

Rectus capitis lateralisObliquus capitis inferior and superiorIntertransversariiMultifidiIliocostalis cervicisLongus colliLevator scapulaeLongissimus capitisSplenius cervicisSplenius capitisSCMScalene muscles

The images below illustrate several views of muscles of the neck.

Lateral view of the muscles of the neck. Anterior view of the muscles of the neck. Infrahyoid and suprahyoid muscles. Scalene and prevertebral muscles.

Related Medscape Reference topics include the following:

Cervical Spine Injuries in SportsCervical Sprain and StrainDisk Herniation ImagingPreviousNextSport-Specific Biomechanics

When contact is made with the head or body, deceleration injuries occur, and sudden flexion and extension of the neck can result. This type of injury is likely to occur in contact or collision sports such as football, soccer, rugby, or lacrosse.

The posterior neck muscles may be strained when resisting flexion forces, and/or the anterior neck muscles may be strained when resisting hyperextension. Microtears or strains in these muscles are caused by the sudden muscular contractions that try to decelerate the applied force. Forced twisting, which is common in wrestling, can also cause a cervical strain. The twisting injury usually happens in the wrestler who is pinned on the mat, and a flexion-extension injury is more likely to happen during the takedown. Deceleration and rotational forces can also cause microtears or stretching of the small intertransverse and interspinous ligaments as well as the joint capsules.

In cervical sprains, the immediate soft-tissue trauma occurs in the structures in and around the facet joints. This trauma occurs with varying severity, including multiple tears in ligamentous tissue with focal hematomas and hemorrhages. A fibrous tissue contraction is the net final effect of the repair of these strained capsular and ligamentous tissues so that restriction of motion and stiffening of the neck may eventually result. The short capsular ligaments of the Luschka interbody joints lack the normal laxity of the capsular structures surrounding the facet joints. Because of their anatomic position, the articulating surfaces of these vertebral body joints are particularly susceptible to injury from axial compression when the head is in a laterally tilted or neutral position.

The cervical spine can absorb much of the imparted energy of collisions by dissipation through the normal lordotic curve of the cervical spine, the paravertebral musculature, and the intervertebral discs. However, when the neck is flexed about 30°, the forces applied to the top of the head are directed to a straight-segmented column because the normal lordotic curve is flattened. The cervical spine is then less able to dissipate the exerted forces in this situation, leading to fracture(s) and possible spinal cord injury. This proposed mechanism is supported by biomechanical studies that replicate it. In individuals with straight cervical spines, less energy is needed to fail under an axial load than in those with a normal lordotic curve; this finding underlines the importance of the cervical musculature in maintaining proper lordosis.

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Lumbosacral Spine Sprain/Strain Injuries

Background

Low back pain (LBP) is a well-known health concern in the United States. Although the incidence of low back injuries is much less in athletes than in a corresponding population of industrial workers, such injuries are still seen in many athletes. The most common causes of LBP in athletes are musculoligamentous sprains and strains, which occur mainly at the lumbosacral region. This is true of both high-performance, world-class athletes and of "weekend athletes." With over 30 million Americans now involved in organized sports, these back injuries present health concerns on the national level.

(See also the Medscape Reference articles Mechanical Low Back Pain [in the Physical Medicine and Rehabilitation section], Lumbar Disk Problems in the Athlete [in the Sports Medicine section], and Low Back Pain and Sciatica [in the Neurology section], as well as Pain Measurement in Patients With Low Back Pain, Guidelines Issued for Management of Low Back Pain, and Epidemiology of Adolescent Spinal Pain: A Systematic Overview of the Research Literature on Medscape.)

For excellent patient education resources, see eMedicineHealth's patient education articles Low Back Pain and Sprains and Strains.

NextEpidemiologyFrequencyUnited States

Studies document that 7-13% of all sports injuries in intercollegiate athletes are low back injuries. The most common back injuries are muscle strains (60%), followed by disc injuries (7%). Athletes are more likely to sustain injuries in practice (80%) than during competition (6%).[1] American football (17%) and gymnastics (11%) are reported to have the highest rates of low back injury.[1]

International

Exact numbers regarding the international frequency of low back injuries are not known, however, a recent French study reported over 50% of French individuals aged 30-64 years had experienced at least 1 day of LBP over the previous 12 months, and 17% had suffered LBP for more than 30 days in the same 12-month period.[2] The authors noted that the prevalence of LBP varied between men and women, that there was an increased incidence with increasing age for LBP that lasted more than 30 days, and that these data were similar to those of other countries.

In an African study, the mean LBP point prevalence among adults was 32%, with an average 1-year prevalence of 50% and an average life-time prevalence of 62%.[3]

PreviousNextFunctional Anatomy

Sprains are ligamentous injuries that are caused by a sudden violent contraction, sudden torsion, severe direct blows, or a forceful straightening from a crouched position. All major ligaments (ie, anterior longitudinal, posterior longitudinal, yellow, intertransversal, capsular, interspinosus, supraspinosus) can sustain sprains; however, the posterior ligaments are more prone to injury. The posterior longitudinal ligament, for example, is the biggest of this group of ligaments and is less developed than its anterior counterpart.

Strains are defined as tears, either partial or complete, of the muscle-tendon unit. Muscle strains and tears most frequently result from a violent muscular contraction during an excessively forceful muscular stretch. Any posterior spinal muscle and its associated tendon can be involved, although the most susceptible muscles are those that span several joints.

Combined with injured tendons and ligaments, all embedded structures may be temporarily or permanently damaged. Of major interest are proprioceptors that play a crucial role in the motor control of the spine. An inhibited motor control weakens spinal stability and may lead to chronic back problems or reinjury.

PreviousNextSport-Specific Biomechanics

The lumbar spine bears tremendous loads: the large, superimposed body weight interacts with additional forces that are generated by lifting as well as other activities that involve powerful forces.[4, 5, 6, 7, 8] The lumbar spine and the hips are responsible for the mobility of the trunk. The L4-5 and L5-S1 areas bear the highest loads and tend to undergo the most motion. Consequently, these areas are found to sustain the most spinal strain or sprain injuries. In addition, load-bearing strain and sprain injuries most frequently occur during the strongest coupling patterns (ie, lateral bending with flexion-extension, axial rotation with lateral bending).

The bony architecture and the ligamentous elements constitute the structural components of the spine.[9] The muscles and tendons constitute the dynamic elements. With all elements intact, the biomechanical function of the spine is normal. The intrinsic translatory and rotatory stability of the spine is provided by the ligaments. The contribution of a given ligament depends not only upon its particular strength, but also upon its location. Moreover, a ligament may contribute relatively more to either the translatory or rotatory stability, depending upon the loading circumstances. Assuming that all ligaments are made of the same material, the strength of a ligament is proportional to its cross-sectional area. A ligament with a larger cross-sectional area provides greater stability and less displacement when the functional spinal unit (FSU) is subject to physiologic loads.

Another factor that contributes to spinal stability is the distance of a ligament from the center of rotation.[10] A ligament that is located close to the center of rotation provides much less stability against bending than a ligament that is further away from the rotation center. The interspinous ligaments in the adult lumbar spine are frequently absent, ruptured, or degenerated and do not contribute to stability of the spine. However, supraspinous ligaments do play a role in stabilizing the spine. Muscles provide stability to the spine during all dynamic movements and actions. Injured trunk muscles can decrease spinal stability if the intact muscles are not able to compensate for the dysfunction of the injured unit.

Spinal instability can occur as a result of trauma, disease, surgery, or some combination of the 3 causes. Clinical instability is defined as a loss of the ability of the spine to maintain relationships between vertebrae under physiologic loads in such a way that (1) there is neither initial nor subsequent damage to the spinal cord or nerve roots, and (2) there is no development of incapacitating deformity or severe pain. Instability leads to abnormal kinetics (stiffness) and/or kinematics (coupling patterns).

When the tissues surrounding the spine are damaged, structures embedded within those tissues may also become temporarily or permanently harmed. Proprioceptors, including muscle spindles, Golgi tendon organs, and joint receptors, are of great importance for postural control. Damaged proprioceptors weaken the stability of the spine and may lead to reinjuries or chronic problems. Although some studies document changes in the normal quality and quantity of motion, there has been no compelling correlation of either with pain behavior.

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