[Dynamic change in the ligmenta flava of the cervical spine in motion].

Cervical spine specimen from fresh cadaver of 10 young persons, 8 males and 2 females, aged from 23 to 32 years, were divided right through the midline after frozen under -30 degrees C. Changes in length and thickness of each ligmenta flava were measured in hyperflexion and hyper extension as well as in neutral position. Being stretched long and thin in flex and contracted short and thick in extension, the ligmenta flava stuck into the spinal canal in position of hyperextension, mostly at C5-6 (3.50 +/- 0.34 mm) and then C4-5 (3.25 +/- 0.50 mm), C6-7 (2.96 +/- 0.61 mm) in descending order. This experiment definitely demonstrated that segmental narrowing of spinal canal , due to sticking in of ligmenta flava at each intravertebral level, was fashioned in hyperextension.