Segment length and root orientation in normal and sacrally attached spinal cords: A morphometric study

This study compares human spinal cord segment length and spinal nerve root orientation in normal and sacrally attached cords. The proportion of the total length of the mature normal spinal cord made up by individual segments varies little between C1 and T1. Between T2 and T6 it increases gradually to a maximum and decreases steadily from T7 to the caudal termination of the cord. The C1 and C2 roots run superolaterally from the cord to their intervertebral foramina. C3 runs almost horizontally. From C4 to T2 roots run progressively more caudally. At T3 and lower levels each root runs caudally in contact with the lateral cord margin before turning laterally to its intervertebral foramen. The pattern of variation in segment length of a sacrally attached cord resembles that in normal cords between upper cervical and lower thoracic levels. In the sacrally attached cord, segment length remains relatively unchanged between mid‐thoracic and mid‐lumbar levels and decreases rapidly caudal to L3. © 1993 Wiley‐Liss, Inc.