Study Design. In an experimental study using human cadaver specimens the bi
omechanical data of anterior atlantoaxial plating according to Harms were e
valuated.
Objectives. The purpose of this study was to evaluate this method biomechan
ically.
Summary and Background Data. The optimum fixation method to achieve fusion
at the atlantoaxial joint after odontoid resection is still a matter of dis
cussion. isolated posterior surgical procedures for treatment of irreducibl
e atlantoaxial kyphosis with spinal cord compression are associated with hi
gh rates of morbidity and mortality. Transoral atlantoaxial plate fixation
has been designed by Harms as a fixation technique after odontoid resection
. In a modification, this procedure has been combined with the posterior wi
re fusion according to Brooks.
Method. Eight human cadaver craniocervical specimens were tested in flexion
, extension, rotation, and bending with a nondestructive flexibility method
using a nonconstrained testing apparatus. Five different groups were exami
ned: 1) control group (intact); 2) unstable group (after dissection of the
atlantoaxial ligaments and odontoidectomy), 3) Harms group (transoral atlan
toaxial plate fixation) 4) Harms-Brooks group (transoral atlantoaxial plate
fixation and dorsal atlantoaxial wire fixation); and 5) Magerl group (tran
sarticular atlantoaxial screw fixation); In a second experimental series, f
ailure loads of the Harms-Brooks and the Magerl fixation methods were deter
mined.
Results. The angular displacement of the Harms-Brooks group and the Magerl
group was less than in any other group. Stiffness values at 0-3.0 Nm loads
in any direction were larger for the Harms-Brooks-and Magerl-fixated,specim
ens than for the Harms, control, or unstable specimens. No statistically si
gnificant difference was observed between Harms-Brooks and Magerl reconstru
ction stiffness. Ultimate failure load in the Harms-Brooks group was higher
than in the Magerl group.
Conclusions, Experimentally, isolated anterior atlantoaxial plating was les
s stable than the combined reconstruction procedures. Transoral plate fixat
ion according to Harms in combination with posterior wire fixation accordin
g to Brooks provided a failure load and stiffness equal to transarticular s
crew fixation according to Magerl.