eMedicine Specialties > Physical Medicine and Rehabilitation > Lumbar Spine Disorders

Lumbar Compression Fracture

Author: Andrew L Sherman, MD, MS, Associate Professor of Clinical Rehabilitation Medicine, Vice Chairman, Chief of Spine and Musculoskeletal Services, Program Director, SCI Fellowship and PMR Residency Programs, Department of Rehabilitation Medicine, Leonard A Miller School of Medicine, University of Miami
Coauthor(s): Nizam Razack, MD, FACS, Assistant Professor of Neurological Surgery, Orthopedics, and Rehabilitation, University of Miami; Neurosurgeon, Spine and Brain Neurosurgery Center; Chairman, Department of Neurosurgery, Orlando Regional Medical Center
Contributor Information and Disclosures

Updated: Oct 28, 2009

Introduction

Background

The lumbar vertebrae are the 5 largest and strongest of all vertebrae in the spine. These vertebrae comprise the lower back. They begin at the start of the lumbar curve (ie, the thoracolumbar junction) and extend to the sacrum. The strongest stabilizing muscles of the spine attach to the lumbar vertebrae. Fractures of lumbar vertebrae, therefore, occur in the setting of either severe trauma or pathologic weakening of the bone. Osteoporosis is the underlying cause of many lumbar fractures, especially in postmenopausal women. Osteoporotic spinal fractures are unique in that they may occur without apparent trauma. However, a thorough diagnostic workup is always required to rule out spinal malignancy. (See image below and Image 1.)

Pathophysiology

The lumbar spine provides both stability and support, allowing humans to walk upright. Proper function of the lumbar spine requires that it have a normal posture (ie, a normal lumbar curve). Any injury that changes the shape of a lumbar vertebra will alter the lumbar posture, increasing or decreasing the lumbar curve. As the body attempts to compensate for the alteration in the lumbar spine in order to maintain an upright posture, this will tend to distort the curves of the thoracic and cervical spine.

Lumbar compression fractures can be a devastating injury, therefore, for 2 reasons. First, the fracture itself can cause significant pain, and this pain sometimes does not resolve. Second, the fracture can alter the mechanics of the posture. Most often, the result is an increase in thoracic kyphosis, sometimes to the point that the patient cannot stand upright. In trying to maintain their ability to walk, patients with kyphosis report secondary pain in their hips, sacroiliac joints, and spinal joints. These patients are also at risk for falls and accidents, increasing the risk of secondary fractures in the spine and elsewhere.

Fractures in the lumbar spine occur for a number of reasons. In younger patients, fractures are usually due to violent trauma. Car accidents frequently cause flexion and flexion distraction injuries. Jumps or falls from heights cause burst fractures. These fractures can also result in serious neurological injury. In older patients, lumbar compression fractures usually occur in the absence of trauma, or in the context of minor trauma, such as a fall. The most common underlying reason for these fractures in geriatric patients, especially women, is osteoporosis. Other disorders that can contribute to the occurrence of compression fractures include malignancy, infections, and renal disease.

Traumatic fractures

Different types of fractures can occur in the lumbar (or thoracic) spine. Classification of these fractures is based on the 3-column anatomic theory of Denis, which describes anterior, middle, and posterior spinal columns consisting of aspects of the spine and their corresponding ligaments and other soft-tissue elements. The Denis system, however, was created to classify traumatic fractures. A similar classification system does not exist for compression fractures. The main reason to use such a classification is to help determine whether a fracture is stable. Instability in the Denis system implies that damage has occurred to at least 2 of the columns of the lumbar spine.

• Wedge fractures are the most common type of lumbar fracture and are the typical compression fracture of malignancy or osteoporosis. They occur as a result of an axially directed central compressive force combined with an eccentric compressive force. In pure flexion-compression injuries, the middle column remains intact and acts as a hinge. Although wedge fractures are usually symmetric, 8-14% are asymmetric and are termed lateral wedge fractures.
• Fractures involving flexion and distraction forces are often due to lap belts in motor vehicle accidents. Commonly, the posterior columns are compromised in these injuries because the ligaments of the posterior elements are disrupted. This type of injury is quite common in young children. Most patients with flexion-distraction injuries remain neurologically intact.
• Burst fractures result from high-energy axial loads to the spine. Multiple classification systems exist for these fractures. The severity of the deformity, the severity of canal compromise, the extent of loss of vertebral body height, and the degree of neurologic deficit affect the determination of whether these injuries are unstable.

When any of the above injuries occurs with a severe rotational force, the degree of injury and of instability increases.

Nontraumatic fractures

In osteoporosis, osteoclastic activity exceeds osteoblastic activity, resulting in a generalized decrease in bone density. The osteoporosis weakens the bone to the point that even a minor fall on the tailbone, causing an axial load or flexion, results in one or more compression fractures (see Image 1). The fracture is usually wedge shaped. Without correction, a wedge fracture invariably increases the degree of kyphosis.

Malignancies that result in spinal fractures are most commonly metastases rather than primary bone cancers. Primary cancers that often spread to the spine via hematologic dissemination include cancers of the prostate, kidneys, breasts, and lungs. Melanoma is a less common but more aggressive cause of spinal metastasis. The most common primary cancer of the spine is multiple myeloma, but others, including a variety of sarcomas,² can also manifest as a spinal fracture. Nonmalignant lesions that can cause fractures include aneurysmal bone cyst and hemangioma.

Spinal infections usually start in the lumbar intervertebral disk. From the disk, the infection spreads to bone, resulting in osteomyelitis. Severe pain is the hallmark symptom. The exception is spinal tuberculosis or Pott disease. In this case, the disk spaces are typically spared and a compression fracture may be the initial manifestation that leads to its discovery.

Frequency

United States

Most fractures of the lumbar spine that require operative treatment occur at the thoracolumbar junction. These injuries are primarily traumatic in origin. Most nontraumatic lumbar fractures are osteoporotic in origin. These are almost invariably wedge-type compression fractures. The National Osteoporosis Foundation (NOF) estimates that currently, 10 million individuals in the United States have osteoporosis, and 34 million more have low bone mass.³ In 2005, osteoporosis was responsible for more than 2 million fractures; approximately 547,000 of those were vertebral fractures. Approximately one third of osteoporotic vertebral injuries are lumbar, one third are thoracolumbar, and one third are thoracic in origin. Additionally, 75% of women older than 65 years who have scoliosis have at least 1 osteoporotic wedge fracture.

Mortality/Morbidity

• Mortality from a lumbar fracture is rare; however, morbidity can be significant.
• In elderly patients with acute osteoporotic fractures, pain and prolonged bed rest can lead to multiple secondary medical complications.
• In younger persons, neurologic damage from traumatic spine injuries can result in problems such as loss of lower extremity strength and sensation and loss of bowel and bladder control.

Sex

Osteoporosis occurs primarily in postmenopausal women. Type 1 osteoporosis occurs in women aged 51-65 years and is associated with wrist and vertebral fractures. Estrogen deficiency is the main etiologic factor. Type 2 osteoporosis (senile type) is observed in women and men older than 75 years, in a 2:1 ratio of women to men.

Age

In young and middle-aged adults, most lumbar fractures are traumatic in origin. High-velocity falls can cause burst fractures, and seat-belt injuries can cause wedge fractures. As stated above, women 51-65 years old develop type 1 osteoporosis. After age 75 years, men also begin to develop type 2 osteoporosis.

Clinical

History

Midline back pain is the hallmark symptom of lumbar compression fractures. The pain is axial, nonradiating, aching, or stabbing in quality and may be severe and disabling. The location of the pain corresponds to the fracture site, as seen on radiographs. In elderly patients with severe osteroporosis, however, there may be no pain at all as the fracture occurs spontaneously.

Young adults may present with severe back pain following an accident, such as a fall or a motor vehicle accident. Lower extremity weakness or numbness are important symptoms of neurologic injury from the fracture.

Vertebral fractures may also cause referred pain. Gibson et al presented a study of 350 patient encounters in 288 patients with 1 or more compression fracture without conus medullaris compromise or spinal nerve compression. They found that nonmidline pain was present in 240 of the 350 encounters. The pain was typically in the ribs, hip, groin, or buttocks. Treatment of the fracture with vertebroplasty (see Other Treatment) resulted in 83% of those patients gaining pain relief.⁴

Alternatively, many compression fractures are painless. Osteoporosis is a silently progressive disease. Osteoporotic compression fractures are often diagnosed when an elderly patient presents with symptoms such as progressive scoliosis or mechanical lower back pain and the physician obtains routine lumbar radiographs.

Finally, patients may present with a known (or unknown) malignancy. Routine spinal screening via magnetic resonance imaging (MRI; if focal or referred pain occurs), or via bone scan (as a survey if pain has not occurred) reveals the pathologic fracture. The most common malignancies leading to spinal involvement in the form of fractures are metastasis and multiple myeloma. Often, the compression fracture is the presenting manifestation that leads to the diagnosis of malignancy. However, patients may also have unexplained fevers, night sweats, past history of malignancy, or weight loss.

Finally, patients who have recently traveled outside of the United States, or who live in the inner city, may have symptoms of infection, such as general malaise, fever, or severely increasing pain. In these patients, osteomyelitis and Pott disease (tuberculosis spondylitis) must be ruled out.

Physical

A detailed neurologic examination is essential in all patients presenting with back pain, spine deformity, or traumatic spine injury. Most interventional procedures to alleviate pain in compression fractures are contraindicated in cases of neurologic compromise. Thus, a rectal examination is required to assess for rectal tone and sensation in trauma patients.

Upon inspection of the spine, the patient typically has a kyphotic posture that cannot be corrected. The kyphosis is caused by the wedge shape of the fractured vertebra; the fracture essentially turns the lateral conformation of the vertebra from a square to a triangle.

Hip flexor contractures due to iliopsoas shortening are typically present.

Palpation is important to correlate any reports of pain to the radiographic level of injury. Extreme pain elicited with superficial palpation is often observed in patients with spinal infections. Moderate pain is usually present at the level of the fracture.

Causes

The principal underlying cause of lumbar compression fractures is osteoporosis. In women, the leading risk factor for osteoporosis is menopause, or estrogen deficiency. Additional risk factors that may worsen the severity of osteoporosis include cigarette smoking, physical inactivity, use of prednisone and other medications, and poor nutrition. In males, all of the above nonhormonal risk factors apply; however, low testosterone levels also may be associated with compression fractures.

Renal failure and liver failure are both associated with osteopenia. Nutritional deficiencies can decrease bone remodeling and increase osteopenia. Finally, genetics also play a role in the development of compression fractures; osteoporosis can be observed in closely related family members.

Malignancy may manifest initially as a compression fracture. The most common malignancy in the spine is metastasis. Typical malignancies that metastasize to the spine are renal cell, prostate, breast, and lung, although other types can metastasize to the spine on rare occasions. The 2 most common primary spine malignancies are multiple myeloma and lymphoma.

Infection that results in osteomyelitis can also result in a compression fracture. Typically, the most common organisms in a chronic infection are staphylococci or streptococci. Tuberculosis can occur in the spine and is called Pott disease.

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