Sports Medicine: Just the Facts

• In football, those most at risk play defensive posi-
  tions, i.e., defensive backs, linemen, and linebackers
  (Cantu and Mueller, 2000; Castro et al, 1997).


• The prevalence of the stinger or burner (i.e., neu-
  rapraxic injury to the nerve root or brachial plexus) is
  reported to be ≥50% in football players (Levitz,
  Reilly, and Torg, 1997).


• Helmets have decreased fatalities but may have
  increased the risk of nonfatal cervical spine injury due
  to the emergence of spear-tackling and by imparting a
  sense of invincibility to the athlete in his “armor.”

FUNCTIONAL ANATOMY

• There are seven cervical vertebrae and eight exiting
  nerve roots.


• The cranium articulates with C1 at the atlantooccipi-
  tal joint, where approximately 50% of all flexion and
  extension occur (the “yes” joint). The first and second
  cervical vertebrae form the atlantoaxial joint and are
  uniquely designed to allow for 50% of all cervical
  rotatory motion (the “no” joint).


• Lateral bending occurs coupled with rotation via
  motion from C3 to C7.
  •Intervertebral discs between C2 and C7 serve to dissi-
  pate and transmit compressive or axial loads.


• The discs are thicker anteriorly and this design con-
  tributes to the normal cervical lordosis.


• Normal sagittal diameter of the cervical spinal canal
  between C3 and C7 is ≥15 mm, and spinal stenosis is
  present below 13 mm. Functional spinal stenosis
  refers to the loss of protective cushioning from cere-
  brospinal fluid around the spinal cord as documented
  on MRI, CT, or myelography (Cantu, Bailes, and
  Wilberger, 1998).


• Each nerve root occupies between 25 and 33% of the
  neural foramen, which is bordered by the uncoverte-
  bral joints anteromedially, the intervertebral disc
  medially, the zygapophyseal or facet joints posterolat-
  erally, and superiorly/inferiorly by the pedicles of
  adjoining vertebrae. Degenerative arthritic changes of
  any of the structures that form or border the foramina
  may contribute to nerve root compression.


• From C2 to C7, the nerve roots exit above their corre-
  sponding numbered vertebral body, while C1 exits
  between the occiput and atlas, and C8 exits between
  the C7 and T1 vertebrae (Malanga, 1997).


• The cervical spine depends on both static (i.e., osseo-
  cartilaginous and ligamentous) and dynamic (i.e.,
  musculotendinous) stabilizing factors to absorb
  and/or dissipate forces.
  •Pain in the cervical spine is mediated by free nerve
  endings in the outer 1/3 of the annulus fibrosus of each

intervertebral disk, in the zygapophyseal (facet) joints,

in the ligaments (i.e., posterior longitudinal ligament,

ligamentum flavum, interspinous, and supraspinous

ligaments), and the supporting musculature.

SPORT-SPECIFIC BIOMECHANICS

• The cervical spine is normally able to absorb signifi-
  cant multidirectional external forces by virtue of sev-
  eral supportive mechanisms.


• The cervical lordosis aids in dissipating axial loads
  through the intervertebral disks, facet joints, inter-
  spinous ligaments, and paraspinal muscles. Tucking
  the chin during a tackle or before an impact can lead
  to reversal of the normal lordosis and impairs the
  mechanism for dissipating axial loads.


• Axial loading has been shown to be the mechanism of
  catastrophic cervical spine injury in all National
  Football League cases that were documented well
  enough to allow detailed analysis (Torg, Guille, and
  Jaffe, 2002).
  •Hyperflexion or hyperextension of the cervical spine
  in an athlete with a congenitally or developmentally
  narrowed canal may cause neurologic injury by a
  pincermechanism (Penning, 1962).


• External forces that cause a combination of lateral
  bending and extension may lead to neuroforaminal
  compression and the neurologic injury commonly
  called a stinger or burner.
  •A second proposed mechanism for the stinger or
  burner is flexion or extension combined with lateral
  bending and ipsilateral shoulder depression resulting
  in a traction injury to the cervical nerve roots.


• Acceleration/deceleration forces, such as those that
  occur in whiplash injuries, occur commonly in contact/
  collision sports, and commonly cause injury to the
  muscular or ligamentous supports (cervical strain/
  sprain) or the cervical facet joints.

CLINICAL FEATURES

DIFFERENTIAL DIAGNOSIS OF NECK PAIN

IN THE ATHLETE

• Cervical muscle strain or ligament sprain


• Herniated nucleus pulposus


• Burner/stinger (i.e., cervical nerve root, brachial
  plexus, or peripheral nerve neuropraxia)


• Cervical radiculopathy


• Brachial plexopathy


• Fracture or dislocation
  •Facet arthropathy

244 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE