Orthopedic With Answer Spine Review | Dr Hutaif Spine S -...

DISCUSSION: Direct measurement and finite element modeling results show that
approximately 20% of the vertical load is borne by the posterior structures of the lumbar
spine in the upright position.

Scientific References

: Adams MA, Hutton WC: The effect of posture on the role of the apophyseal joints in resisting intervertebral compressive forces. J Bone Joint Surg Br 1980;62:358-362.
Goel VK, Kong W, Han JS, Weinstein JN, Gilbertson LG: A combined finite element and optimization investigation of lumbar spine mechanics with and without muscles. Spine 1993;18:1531-1541.

DISCUSSION: The paravertebral musculature, the intervertebral disks, and the normal lordotic curvature of the cervical spine can absorb much of the imparted energy of collision. However, when the neck is flexed approximately 30 degrees, the normal lordotic curvature is flattened and the forces applied to the vertex of the head are directed at a straight segmented column. In this situation, the cervical spine is less able to absorb the applied force. With mounting axial load, compressive deformation occurs within the intervertebral disks, causing angular deformation and buckling. The spine will fail in flexion, with resultant fracture, subluxation, or dislocation. A rotatory component added to axial compression can cause concomitant extension, rotation, and shear injury patterns. The National Football Head and Neck Injury Registry has made two recommendations to the NCAA Football Rules Committee to minimize the risk of such injuries: (1) No player should intentionally strike an opponent with the crown or top of the helmet; and (2) No player should deliberately use his helmet to butt or ram an opponent.
REFERENCES: Thomas BE, McCullen GM, Yuan HA: Cervical spine injuries in football players. J Am Acad Orthop Surg 1999;7:338-347.
Torg JS, Truex R Jr, Quedenfeld TC, Burstein A, Spealman A, Nichols C III: The National Football Head and Neck Injury Registry: Report and conclusions 1978. JAMA 1979;241:1477-1479.

DISCUSSION: The incidence of recurrent disk herniation after a successful diskectomy is approximately 5% to 10%. Indications for surgical diskectomy for a recurrence are the same as for a primary diskectomy.
REFERENCES: Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 685-698.
Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update Spine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 127-139.

DISCUSSION: In the normal adult, the distance between the basion and the tip of the dens is 4 mm to 5 mm. Any distance greater than 5 mm is considered abnormal. This is one way to detect occipitocervical dissociation other than using the Power’s ratio, which relies on an anterior dislocation.
REFERENCES: Wiesel SW, Rothman RH: Occipitoatlantal hypermobility. Spine 1979;4:187-191.
Wholey MH, Browner AJ, Baker HL Jr: The lateral roentgenogram of the neck: With comments on the atlanto odontoid-basion relationship. Radiol 1958;71:350-356.