Fracture, Lumbosacral Spine (Without Spinal Cord Injury)

A fracture of the lumbosacral spine involves a break in one or more bones of the lumbar and sacral regions of the spine (vertebrae L1 through L5 and S1 through S5) in the lower back (lumbosacral spine). The five lumbar vertebrae are located in the slightly curved portion of the back between the end of the thoracic vertebrae (T12) and beginning of the sacral vertebrae (S1). Increased mobility of the lumbar spine makes it a more common site for fractures than the more rigid thoracic spine. Because the lumbar spine must sustain compressive, bending, and twisting forces between the upper and lower body, its vertebrae are larger, wider, and heavier than other areas of the spine and are surrounded by strong muscles and ligaments that help protect them from severe injury. The five sacral vertebrae extend from the last vertebra of the lumbar spine to the end of the spinal column; these vertebrae are fused together to form the triangular “tailbone” at the base of the spine.



Fractures in the lumbosacral spine may be classified according to the mechanism of injury and the degree of instability. Categories of fractures include compression fracture, transverse process fracture, burst fracture, flexion-rotation injury, and pathologic fracture. The fracture may be classified further as stable or unstable. A stable fracture is one that is not likely to change as the weight-bearing load on the spine changes, which makes it less likely to result in nerve or spinal cord damage (e.g., neurologic deficit or paralysis). Unstable fractures are described by abnormal motion at the fracture site and may be associated with neurologic injury. Fracture of vertebrae in the lumbosacral area can result in either temporary or permanent disability. The majority of lumbosacral fractures occur without spinal cord injury: 10% to 38% of adults with fractures in the lumbosacral region are reported to have associated spinal cord injury.



Lumbosacral fractures can involve any lumbar vertebrae but often involve the lumbosacral junction (L5-S1), where the two sections of spine articulate. Nerve compression with neurologic deficit may or may not occur with these injuries. Instability is common, especially in oblique sacral fractures that can destroy stability on each side of the vertebral junction. Vertical sacral fractures usually occur in conjunction with a fracture in the pelvic ring. Transverse sacral fractures can be either (1) a partial break or bending of the bone (“green-stick” fracture) that may increase the concave curvature (kyphosis) of the lower spine but is usually stable or (2) an unstable proximal transverse fracture more subject to neurologic deficit.



Compression fractures most commonly occur after falls or jumps from a height, with the individual landing on his or her heels. Compression fractures can also occur as the result of a sports injury or motor vehicle accident and are sometimes overlooked because of other, more serious injuries. 



Fractures of the transverse process are most often the result of direct violence. 



Fractures resulting from forceful flexion and rotation are common in motor vehicle and mining accidents. Fractures caused by acute flexion of the spine are most often sustained in motor vehicle accidents by individuals wearing a lap seatbelt without a shoulder harness (seatbelt injuries). 



Pathologic fractures are seen in individuals with osteoporosis or other disease conditions that compromise bone strength.

Incidence and Prevalence: Approximately 150,000 people sustain fractures to the vertebral column each year; the majority are in the lumbar spine and occur without spinal cord injury. Among sports-related injuries, 9% to 15% are estimated to result in spinal injury, of which 3% to 7% involve the lumbar spine. The majority of lumbosacral fractures do not involve spinal cord injury; cord injury occurs in about 10% to 38% of adult spine fractures 

Causation and known risk factors

Individuals at the greatest risk of lumbosacral spine fractures are male athletes and young adult males in general because of their statistically higher likelihood of being involved in automobile accidents and violent activity. Individuals with osteoporosis and osteoarthritis are also at greater risk of pathologic fracture than the general population. Elderly individuals at risk of pathologic fracture, especially of the pelvis, are also at risk of concomitant sacral vertebral fracture.

Diagnosis

History: Individuals will often complain of localized pain in the low back, sometimes specifically over the injured vertebrae. Referred pain may be reported in the upper back or neck and with motion. The individual may report other signs and symptoms such as changes in sensation, including tingling, weakness, numbness, or an inability to move the lower extremities. Loss of bowel and bladder function may be reported. A detailed history will include the mechanism of injury, relative force sustained and type of force (compression, flexion, extension, rotation, shear, distraction, or a combination), prior spinal injury, and any neurologic changes noted at the time of injury. A general health history should include prior diagnosis and treatment for metabolic or endocrine conditions that could contribute to pathologic fracture.

Physical exam: The extent of the physical exam immediately after injury depends on the presence of life-threatening conditions (decreased respiratory rate, bradycardia, shock) and the stability of the injured spine. Individuals may present with obvious swelling, bruising (ecchymosis), and deviations from normal spine curvatures (kyphosis or spinal deformity). If these symptoms are not obvious, the physician may look for contusions or abrasions over the skin of the spine. Tenderness of the spine may be evident upon touch (palpation). When the individual is stable and the spine is protected, a complete neurologic examination is performed to evaluate nerve damage resulting from spinal cord injury sustained during the fracture. This includes testing of the reflexes by percussion, muscle function with resisted range of motion, and sensitivity to touch. Nerve damage will be evident with either decreased or hyperactive reflexes, decreased muscle function, and diminished perception of touch. The examination includes an assessment of head injuries and fractures of the extremities, as well as abdominal or urologic trauma, all of which sometimes accompany lumbar spine fractures.

Tests: X-rays of the spine are ordered to establish the diagnosis of vertebral fracture. CT and/or MRI scans may be necessary to determine fragment position, extent of injury, and soft tissue involvement. Bone scan may be useful in ruling out fractures when x-ray and CT scan results are inconclusive. Neurologic studies may include electromyography (EMG) and nerve conduction studies to assess for possible radiculopathy. Routine lab studies will include CBC with hematocrit and hemoglobin to assess for internal bleeding or anemia, coagulation tests, blood type and crossmatch to reserve blood for transfusion if needed, electrolytes and blood chemistry panel, and urinalysis to screen for genitourinary tract injury. Urodynamic studies may be needed to evaluate functioning of the lower urinary tract.

Treatment

Criteria that help determine treatment include the degree of instability and presence of neurologic deficit. Nonoperative treatment is the standard approach for stable fractures that have no tendency toward neurologic deficit or late deformity. Treatment may include a custom brace or cast, bed rest, or limited activity. The goal is to prevent rotational movement and bending. Once a fracture of the lumbar or sacral spine is appropriately stabilized, rehabilitation may be initiated, including mobilization or manipulation of the joints above and below the fracture site, followed by range of motion, strengthening, and conditioning exercises as appropriate.



For unstable lumbar spine fractures, surgery is believed to offer the advantages of decompressing the spinal cord and shortening rehabilitation time compared to bed rest only.



Surgery is indicated to restore pelvic stability in patients with lumbosacral junction fractures that result in instability, neurologic deficit, or deformity, especially in patients with concomitant fracture of the pelvic ring. Surgical intervention may include reduction, stabilization, and fusion of spinal fractures. Surgery is also indicated to restore neural function in high transverse sacral fractures with kyphosis and neurologic deficit, including reduction of deformity, laminectomy, and decompression of nerve roots. Other nerve injuries (e.g., nerve root avulsion) often respond to conservative, nonsurgical treatment.



Surgical procedures include fusion, internal fixation with hardware insertion (instrumentation), and removal of fragments. Postoperative care may involve prolonged bed rest until evidence of healing is demonstrated on x-rays.



Sacral fractures can be treated operatively or nonoperatively, with treatment ranging from bed rest to postural reduction or immobilization using a cast or orthosis. For minimally displaced or angulated fractures with stable pelvic fracture and no neurologic deficit, treatment may consist of bed rest only and early mobilization. Weight bearing is increased as tolerated.

Prognosis

Stable, uncomplicated fractures of the vertebrae in the lumbosacral spine usually heal without difficulty within 6 to 12 weeks, with conservative, nonsurgical treatment. Individuals requiring surgery to stabilize fracture fragments can usually begin early rehabilitation in the absence of neurologic deficit or progressive underlying disease such as osteoporosis or cancer. The need for surgical stabilization does not necessarily mean a longer recovery.



Studies have shown that 88% of patients with unstable lumbosacral fractures and neurologic deficit are able to regain some neural function with surgical treatment, whereas only 20% regained function with nonsurgical treatment.

Rehabilitation

Rehabilitation guidelines for a fracture of the lumbar spine will be based on the fracture type and its management. The stability of the fracture must be ascertained prior to proceeding with rehabilitation.



If the spinal cord is intact, the rehabilitation will take place once the fracture is stable. The primary goal is to restore function and to control pain. Application of cold and heat may help to relieve pain and muscle discomfort. Supervised range of motion and strengthening exercises of the lower extremities and trunk should be initiated when indicated. Simultaneously, individuals should be instructed in trunk stabilization and postural exercises.



Once the fracture is healed, trunk conditioning exercises may be indicated. They may include trunk stabilization, stretching, and strengthening exercises. General aerobic exercises may be added to improve overall body strength and conditioning. Bone healing may occur within 6 to 12 weeks, but bone strength and the ability of the bone to sustain a heavy load may take up to several years to fully return. Once healing has occurred, the individual may resume full activities of daily living. It is important to instruct the individual not to overload the fracture site until the bone has regained its full strength. The resumption of heavy work and sports should be guided by the treating physician.

Complications

Complications of fractures include infection after surgery, nerve damage in displaced fractures, and faulty alignment of the healed vertebrae which can cause deformity.