Seat Belt Fulcrum Injury and Cauda Equina Syndrome
By Jacob W. Gent
February 10, 2015
Seat belts are well known for saving lives and preventing serious injury during a motor vehicle collision. Originally introduced to automobiles decades ago, seat belts are designed as a safety device to prevent occupants from being thrown against the interior of or fully ejected from a motor vehicle. Initially, only lap belts were installed on motor vehicles. Over time, shoulder harnesses were introduced. Now, nearly all vehicles are equipped with lap belts and shoulder harnesses that have locking mechanisms which fully restrain the vehicle occupant upon impact.
Despite their effectiveness in preventing occupant ejection, serious injury and death following a motor vehicle collision, it became apparent some time ago that seat belts may actually cause injury, including Cauda Equina Syndrome (CES). This syndrome, though rare, can be a serious condition resulting in permanent and disabling conditions, and typically involves a large, space-occupying lesion affecting the bundle of nerve roots (cauda equina, or “horse tail”) at the lower end of the lumbar spine. The nerves which make up the cauda equina transmit and receive messages from the pelvic organs and lower extremities. CES occurs when the nerve roots of the lumbar spine are compressed, resulting in decreased sensation and movement and may impair bowel and bladder function.
The most common causes of CES include trauma-related lumbar disk herniation, spinal canal stenosis, a spinal lesion, inflammation, hemorrhage or fracture of the lumbar spine, as well as non-trauma related causes such as tumors or birth defect involving abnormal connection between blood vessels (arteriovenous malformation). In cases involving traumatic injury following a motor vehicle collision, CES can result from a seat belt fulcrum injury.
Collisions between motor vehicles, especially head-on impacts, result in a sudden and abrupt halt to the forward motion of the vehicle. The bodies of a vehicle’s occupants continue moving however, and are thrown forward at the same rate of speed the vehicle was traveling just prior to impact. Vehicle occupants who use the lap belt-shoulder, or 3-point harness, are not immune to injury. For example, the lap belt does not restrain the forward movement of the trunk above the belt or the pelvis and lower extremities below the belt. The result is a concentration of the inertial energy over the small cross section of the lap belt. The belt acts as a fulcrum as the trunk and lower body are thrown forward, causing injury to the soft tissues behind the belt; i.e. the pelvis, lower abdomen and lumbar spine. Although shoulder harnesses may reduce the forward motion of the upper body, they do not fully restrict movement of the trunk and head during impact.
Cauda Equina Syndrome is characterized by varying patterns of low back pain, sciatica, lower extremity sensorimotor loss, and bowel and bladder dysfunction. Full-blown CES includes urinary retention, saddle numbness of the perineum, bilateral lower extremity pain, numbness, and weakness. Physical exam findings consistent with CES include hyperactive reflexes in the lower extremities and positive Valsalva test. Nerve conduction velocity (NCV) and electromyography (EMG) testing of the lower extremities may demonstrate nerve root irritation, while CT and MRI imaging can reveal compressions of the spinal cord.
Cauda Equina Syndrome is a serious condition which can result in permanent paralysis, impaired bladder and/or bowel control, and/or loss of sexual sensation. Patients diagnosed with CES need urgent medical attention and surgery may be required immediately involving surgical decompression of the spinal canal. Prognosis for Cauda Equina Syndrome is dependent on a number of factors, including the degree of nerve damage, how quickly following injury the nerve root is decompressed, and the length of the delay in having the condition properly and fully evaluated. Even with surgery, patients my continue experiencing pain, bowel and bladder problems, and other lower extremity dysfunction, depending on the duration and severity of symptoms prior to surgery.
Anyone suffering from serious injuries who are dealing with long-term physical and emotional complications following trauma need access to quality health care to maximize their recovery. Unfortunately, insurance companies routinely deny benefits and take other actions to block access to appropriate medical treatment to those who need it most. It is important in these situations to consider obtaining legal counsel to assist the patient with handling insurance-related issues which allows the injured person to focus on their health care and recovery.
 Thompson NS, Date R, Charlwood AP, Adair IV, Clements WD. Int’l J of Clinical Practice. seat-belt syndrome revisited; October 2001; Vol. 55; No. 8; pp.573-5