- See:
Multisegmented Hook Instrumentation
- Discussion:
- reduction of retropulsed bone from the canal requires that posterior
longitudinal ligament be intact to provide tension;
- when distracted, ligament pulls bone out of the canal anteriorly
toward the body;
- this technique is generally not successful if surgery is delayed for weeks
(or even days) or w/ severely comminuted fractures;
- indirect method from posterior approach usually involves distraction
instrumentation and three- or four-point fixation to realign spine;
- rods are placed at least
3 levels above & 2 levels below level of injury;
- rods are contoured to provide anterior vector force across the fracture;
- in 75% of cases, adequate canal decompression can be acheived by
posterior instrumentation alone;
- in
neurologically intact pt, residual canal compression is ignored
since canal remodeling will remodel impinging fragments;
-
w/
incomplete neurologic injury & residual canal compromise
> 25% consider secondary anterior decompression;
- Implants:
-
Harrington Rods:
-
CD:
- Pearls:
- enhanced stabilization may be obtained by the addition of sublaminar
or spinous process wires;
- although sublaminar wires gives more rigid fixation, their passage in
a neurologically comprimised patient increases the risk of further
injury, particularly if spinal cord edema is present;
- consider restoring spinal column stability with posterior dual
Harrington distraction rods;
- rods are loaded by 4 point bending and prevent the spine from
flexing into more kyphosis;
- Pitfalls:
- attempt to restore saggital plane alignment;
- avoid overdistraction (esp w/ three column failure);
- most frequent mode of failure w/ dual
Harrington distraction rods has
been cut out or dislodgement of a Hook;
- common difficulty w/ posterior instrumentation is to obtain enough length for
4 point bending of the posterior rods;
- need to include
two levels above & below the injury site which is a
disadvantage in the lumbar spine;
- multiple pieces of bone retropulsed into the canal may not be completely
reduced by distraction instrumentation;
- intraoperative assessment of adequacy of reduction is difficult;
- Misc:
-
Denis type A burst fx can be reduced 80%
- all type A's may reduce by posterior instrumentation alone;
-
type B burst fx will reduce 50% by distraction alone;
- w/ > 60% canal comprimise in neurologically incomplete pts need to
undergo simultaneous anterior & posterior approaches;
Vertebral burst fractures: An experimental morphologic, and radiographic analysis.
BE Fredrickson and WT Edwards et al.
Spine. Vol 17. 1992. p 1012-1021.
Reduction of the intracanal fragment in experimental burst fractures.
BE Fredrickson et al.
Spine. Vol 13. 1988. p 267-271.
