THE EFFECT OF ANTERIOR TRANSLATION OF THE VERTEBRA ON THE CANAL SIZE IN THE LOWER CERVICAL-SPINE - A COMPUTER-ASSISTED ANATOMIC STUDY

Eighteen adult dry-bone spine specimens were used in conjunction with computer analysis to determine the average axial spinal conal area at the levels or C6, C7, and T1 after different degrees of anterior trans lation of the cephalad vertebra. Simulating a distractive flexion inju ry, the cephalad vertebra was anteriorly displaced on the caudal verte bra at 1-mm intervals. after each displacement, the remaining axial sp inal canal area of the caudal vertebra was calculated. The results sho wed that the average axial spinal canal areas for both male and female specimens were similar to 222 mm(2) for C6, 217 mm(2) for C7, and 210 mm(2) for T1, respectively. After a 6-mm anterior translation of the cephalad vertebra (assuming 50% of anterior translation of the vertebr al body), the average axial spinal canal area of the caudal vertebra f or both sexes significantly decreased to 59% at C6, 51% at C7, and 56% at T1, respectively. This study suggests that the size of the axial s pinal canal directly depends on the degree of anterior vertebral trans lation.