[Comparison of three techniques of the transarticular screw placement in the lower cervical spine]

To compare three techniques of the transarticular screw placement in the lower cervical spine.

The techniques of transarticular screw placements used by Takayasu (group A), Dalcanto (group B) and Klekamp (group C) were applied in twenty-four cervical specimens, among which 14 specimens were male and 10 specimens were female, ranging in age from 55 to 80 years, with an average of 68 years. The entry point of Takayasu technique was between the superior and median third of the vertical medial line of the lateral mass with 60 to 80 degrees caudal tilt and 0 degrees lateral tilt. Dalcanto technique started 2 mm caudal to the midpoint of lateral mass with 40 degrees caudal tilt and 20 degrees lateral tilt. Klekamp technique inserted the screws with the starting point being 1 mm medial and 1 mm inferior to the midpoint of the lateral mass with 40 degrees caudal tilt and 20 degrees lateral tilt. The splits of facets, the encroachment of the cervical nerve roots and vertebral arteries, and no-involving facets screws were observed and analyzed.

One hundred and ninety-two transarticular screws were implanted on both sides in twenty-four cervical cadavers, sixty-four for each group. There were twenty-five splits of inferior facets in group B, 2 splits in group C and none in group A. No superior facets were found to be broken in all cases. The difference of splits between group B and the other two groups was significant (Chi2AB = 31.07, P < .001; Chi2BC = 24.83, P < 0.01), while there was no statistical difference between group A and C (Chi2AC = 2.03, P > 0.05). Thirty-six screws encroached the vertebral arteries in group A, none in group B and C. There was significant statistical difference between group A and the other two groups (Chi2AB = 50.09, P < 0.01; Chi2AC = 50.09, P < 0.01). Forty anterior branches of lower cervical nerve roots were involved in group A, five in group B and three in group C. There were statistical differences between group A and the other two groups (Chi2AB = 41.98, P < 0.01; Chi2AC = 47-94, P < 0.01), and there was no statistical difference between group B and C. Sixteen posterior branches of lower cervical nerve roots were encroached in group A, 18 in group B and 14 in group C. There was statistical difference among the three groups (Chi2AB = 0.16, P > 0.05; Chi2AC = 0.17, 0.05; Chi2 = BC = 0.67, P >0.0 ). Although all screws went through facets in the study except for 5 in group A, there were no statistical differences between each groups Chi2AB k =3.33, P >0.05; X2A C =3.33, P> 0.05).

There are high risk of injury of anterior branch of cervical nerve root and vertebral artery if the screws are too long and the Takayasu's technique is used. However, the rate of facet split is high if the Dalcanto's technique is applied. Klekamp's technique is value to be applied.