Wednesday, March 10, 2004
Joseph S. Torg, MD, Helene Pavlov, MD, and Albert Burstein, PhD, are the recipients of the 2004 Elizabeth Winston Lanier award for their manuscript, "The pathomechanics, pathophysiology and prevention of reversible and irreversible cervical spinal cord injury: Results of a 30-year clinical experience."
The paper outlines a series of field, clinical and basic research studies conducted over three decades that has provided answers to basic questions regarding the epidemiology, prevention, pathomechanics, pathophysiology and histochemical responses of reversible and irreversible cervical cord injuries.
The clinical relevance of this 30-year clinical and basic science experience is four-fold. "First, the identification of axial energy inputs resulting in failure and buckling of a segmented column, in keeping with established mechanical engineering principles of elastic instability, has clarified a previously unrecognized cervical spine injury mechanism," reported Dr. Torg, the principal investigator. "This understanding transcended academic interest and has been translated into effective injury prevention measures."
Second, he said, "the elucidation of the axial load mechanism resulting in cervical spine injuries led to the modification of football playing techniques that have profoundly decreased the number of such injuries nationwide."
Third, "the increased understanding of both the pathomechanics and pathophysiology of cervical spine and cord trauma resulting from athletic activities has provided criteria to guide the clinician in management decisions," he pointed out.
Lastly, "correlation of the clinical manifestations of spinal cord deformation secondary to trauma with changes in cytosolic ion concentrations in an in-vitro axonal injury model clearly suggests the potential for therapeutic agents to alter this phenomenon with implementation of measures for spinal cord resuscitation.," he said.
During the 1975 football season, 12 high school and college players in Pennsylvania and New Jersey sustained severe cervical spine injuries, eight of which resulted in permanent quadriplegia and one in death. Dr. Torg witnessed one of these injuries and was responsible for the care of two of those rendered quadriplegic. Analysis of the circumstances surrounding both the occurrence and management of this group of injuries revealed factors at variance with several accepted principles, he reported.
"Specifically, the existing literature regarding the mechanisms of cervical spine injuries were based on post-injury radiograph interpretations and emphasized the roles of hyperflexion and hyperextension, " Dr. Torg said. "However, review of motion pictures of several of the 1975 injuries clearly demonstrated that the injuries resulted from axial loading of the cervical spine due to a collision involving the top or crown of the helmet."
In addition, "two of the injured players who were managed with immediate closed reduction within four hours of the injury experienced significant and unexpected neurologic recovery," he said. "This approach was at odds with those who recommended attempts at gradual reduction of cervical dislocations over a more prolonged period of time."
To determine whether this injury pattern was a local artifact or represented a more widespread and perhaps national problem, the National Football Head and Neck Injury Registry was established in 1975. The registry has collected data on more than 1,300 cervical spine injuries since that time. For each injury, data were collected from the athlete, parents and school officials as well as from radiographs, medical reports and game films, when available.
Data on head and neck injuries occurring between 1971 and 1975 were collected retrospectively. Analysis of game films from this period allowed an accurate determination of the mechanism of injury in 85 percent of the cases. Axial loading of the cervical spine was determined to be the mechanism in every instance, according to Dr. Torg.
He credits the development of the axial-loading concept to consultations with Dr. Burstein, who explained and confirmed these observations as failure of the segmented column due to an axial-load mechanism.
Advent of "spearing"
These findings seemed to indicate that modern helmets, although responsible for a marked decrease in head injuries, had led to the development of playing techniques such as "spearing" that used the top or crown of the helmet as the initial point of contact and placed the cervical spine at risk.
"Based on this observation, we recommended that the National Collegiate Athletic Association and the National Federation of High School Athletic Associations implement rule changes banning spearing and the use of the top of the helmet as the initial point of contact in striking an opponent, " Dr. Torg said. Subsequently, the educational video "Prevent Paralysis: Don't Hit with Your Head" was produced and distributed to 36,000 secondary school principals, university athletic directors and athletic trainers.
Impact of rule changes
Their work had a profound, national impact on the reduction of the number of cervical spine injuries with associated quadriplegia resulting from tackle football.
"Between 1975 and 1996, as a result of these rule changes, a dramatic decrease in the total number of cervical spine injuries, and those resulting in quadriplegia, was documented both at the high school and college level," Dr. Torg said. "We propose that development and implementation of similar preventive measures based on clearly defined injury mechanisms would potentially decrease injury rates in diving, rugby, ice hockey, trampoline, wrestling and other high-risk sports."
An understanding of both the pathophysiology and micropathology of the cervical spine and the cord trauma enabled the authors to develop criteria and guidelines for return to activity following injury. Their manuscript emphasizes characteristic injury patterns involving the middle cervical segment (C3-C4) and the more favorable response to their prompt reduction. The marked instability and grave prognosis of the axial-load teardrop fracture are attributed to the associated sagittal vertebral body and posterior element fractures. Spear-tackler's spine is described and classified as an absolute contraindication to participation in collision sports.
Cervical cord neurapraxia, with or without transient quadriplegia, is neither associated with nor presages permanent neurological sequalae, the authors report. However, a predictable risk of recurrence, based on canal diameter data, is the most frequent complication. The laboratory application of microdeformation of an in-vitro axon model has resulted in a possible histochemical explanation of cord injury at the cellular level, supporting the concept of spinal cord resuscitation to reverse the secondary injury phenomenon that occurs in acute spinal cord trauma.
"We propose that these observations have potential implications regarding therapeutic measures to effect spinal cord resuscitation," Dr Torg said.
The authors believe that the major contributions of their work have been: 1) implementation of an effective, nationally recognized injury prevention program generated from within the orthopaedic community, and 2) the attempt to correlate the observed clinical pathomechanics with cellular pathophysiology in instances of cervical spine and cord trauma.
Dr. Torg is a professor of orthopaedic surgery at Temple University School of Medicine in Philadelphia.
Dr. Pavlov is a professor of radiology in orthopaedic surgery and Radiologist-in-Chief at the Hospital for Special Surgery in New York City.
Currently retired, Dr. Burstein previously served as professor and director of the biomechanics lab at the Hospital for Special Surgery in New York City.
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