Biomechanical testing of pars defect repairs.
METHODS
Human lumbar vertebral bodies were used to biomechanically test three different pars interarticularis defect repair techniques. A posteriorly directed force was applied to the inferior facets so that a bending moment was created across the pars.


OBJECTIVE
The stiffness and strength of each type of repair was measured and compared with the intact values.


BACKGROUND
The Buck screw provided both the stiffest and strongest repair overall and within each group of cadaveric specimens. This was followed by the Morscher hook screw. Both the screw and hook repair were statistically significantly stronger and stiffer than the wire repair. There was no statistical difference between the screw and hook repairs regarding strength or stiffness.


METHODS
Using the intact L1 vertebral body as a control for each cadaver, the three surgical techniques for pars repair could be evaluated.


RESULTS
The screw repair provided 64% of the intact stiffness and 58% of the intact strength. The hook repair provided an average of 52% of the intact stiffness and 40% of the intact strength. The wire provided only 3.5% of the intact stiffness and 12% of the intact strength.


CONCLUSIONS
The screw repair technique is the stiffest and strongest pars repair method. The wire technique restores the least stiffness and strength.
Kip
P C
PC
Sierra Regional Spine Center, Reno, Nevada.
Esses
S I
SI
Doherty
B I
BI
Alexander
J W
JW
Crawford
M J
MJ
D000368:Aged; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016103:Spinal Fractures / Q000503:physiopathology / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology*