The Journal of Bone and Joint Surgery, Vol 71, Issue 5 742-750, Copyright © 1989 by Journal of Bone and Joint Surgery, Inc
Factors influencing the penetration of wires into the neural canal during segmental wiring
MR Zindrick, GW Knight, WH Bunch, MC Miller, DM Butler, M Lorenz and R Behal
Rehabilitation, Research and Development Center, Hines Veterans Administration Hospital, Illinois.
We evaluated the influence of the penetration of wires into the neural
canal during segmental wiring in a three-part study. First we examined the
anatomy of the thoracic spine, specifically the laminar and interlaminar
dimensions, as well as the epidural space. In the second part, we evaluated
the depth of penetration of wires into the spinal canal at the time of
their passage during spinal segmental instrumentation, using direct
laboratory measurements for three configurations of the wire: first with a
straight wire, and then with two wires of varying curvature. The
measurements were repeated after removal of a portion of the lamina. In the
third and final part of the study, we assessed the relationship between the
observed penetration of the wires and the depth of penetration as
calculated using mathematical models for the three wire configurations.
When a wire with the largest possible diameter of curvature was passed
under the lamina, there was significantly less penetration using the
curved-wire configuration. This was seen in calculated models, as well as
in normal specimens of the thoracic spine that were obtained from cadavera.
Little epidural space was found to be available for passage of the wire. In
most instances, passage of the wire must result in contact with and
displacement of the dural sac and its contents. To minimize the depth of
penetration at any given spinal level, it is recommended that the wire be
curved to the maximum degree that will allow it to pass under the
lamina.(ABSTRACT TRUNCATED AT 250 WORDS)