spine and this kinetic link has been quantified by adaunting array of technologies whose description is beyond the scope of this review.5
Athletic injuries to the spine usually result from one of two mechanisms: an acute traumatic event, or repetitive activity that causes fatigue injuries. The stress failures generated by repetitive microtrauma are far more common. Overuse injuries to the spine have been documented in many contact and noncontact sports including gymnastics, ballet, figure skating, hockey, football, weight-lifting, and rowing.1,2,6-9 Back problems may occur in 30% of female gymnasts, 50% of interior linemen, and 82% of elite female rowers.S,10-12

The basis for a given athlete's vulnerability to macro-or microtrauma is often not clear. Most injuries maybe explained by poor conditioning, inadequate warm up, poor technique, and abnormal anatomy or tissue weakness at the heritable ultrastructural level. Singly or in combination, these factors can lead to spine problems in the athlete.

Disk injuries
Many sports injuries impact on the intervertebral disk. The nucleus, annulus, and vertebral endplates absorb loads and effect stability while permitting flexibility . The nucleus plays a crucial role in shock absorption by transferring vertical forces into ones that are radially directed to the annulus. Because the adult disk is avascular, the metabolic needsofits cellular components are served only by passive diffusion through the endplates. Just as transport of nutrients and waste products in and out is aided by exercise, nutrition and cell matrix synthesis are hobbled by static loading and creep. Excessive loading can result in endplate microfractures that when healed can impede transport, which explains the endplate damage and back pain complaints in weight-Iifters, wrestlers, and certain track and field athletes.6,7.13 The lumbar flexion required for these activities increases the lumbosacral angle and exaggerates anterior shear forces.3
Athletes ( especially adolescents orteenagers) with asymptomatic disk protrusion usually do not present with classic symptoms of unilateral sciatica.13,14 There may only be complaints of buttock or hip pain or low back stiffness. Results of a physical examination are often nonspecific, and neurologic deficits are unusual. Findings may be limited to stiffness, scoliosis, or unilateral hamstring spasm.
Conservative treatment is recommended and is effective in more than 80% of cases. A brief period (2-3 days) ofbed rest coupled with non-steroidal antiInflammatory drugs, progressive mobilization, and possibly bracing are measures usually quite effective in returning the athlete to full activity Full contact sports should be avoided for six months after an episode of discogenic sciatica.

Epidural steroids may help in more refractory cases. Surgery is reserved for the rare patient with a progressive neurologic deficit or cauda equina syndrome, or for whom conservative treatment fails. Decompressive surgery should be minimally invasive with no disturbance of the associated ligaments and facetjoints. The natural history of disk disease in the younger athlete has not been well studied, but there appears to be a higher incidence of continued back complaints as adults.

Lumbar fractures
Sports-related lumbar fractures affect either the vertebral body or the posterior elements. The vast majority of vertebral body fractures in the athlete are compression injuries to the anterior portion of the body, which is relatively weak due to an absence of horizontal trabeculations. Rapid flexion, especially associated with axial compression, is usually causative. Sky diving is associated with a high incidence of spinal compression fractures,15 and these injuries also are common with the seated fall in alpine or telemark skiing.16
Skeletally immature athletes with open ring epiphyses are vulnerable to endplate fractures through which the nucleus prolapses into the vertebral body. With less compressive strength than the disk, the endplate fails first, producing a Schmorl's node.17 An anterosuperiorherniation and endplate fracture may result in the separation of a triangular segment of the body, producing the so-called limbus vertebra. Also, the growth plate may separate and slip posteriorly, producing back pain and sciatica. A prolapsed growth plate may be seen on plain radiographs as a bony ridge on the posterior body superiorly or inferiorly.18