A biomechanic study of the surgical repair technique of pars defect in spondylolysis.

To find out which wiring technique of direct repair of the pars defect is the strongest in resisting anteroposterior translation displacement, fifteen fresh human cadaveric L4-L5 spines were biomechanically tested by a universal testing machine. Two millimeters wide pars defect was created on both sides of L4 vertebrae. Each of the five specimens was wired using Nicol's technique (A), modified Nicol's technique (B) and modified pedicular screw technique respectively (C). At each test, motion was observed to occur initially at the pars defect. The mean minimum tensile strength (increment of the pars defect) for technique A, B and C was 87.64, 82.04 and 110.08 Kg Force respectively. By statistical analysis, technique C was the strongest in resisting anteroposterior displacement of the spinal column. There was no statistically significant difference between technique A and B.