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Comparison Between Single-Screw and Triangulated, Double-Screw Fixation in Anterior Spine Surgery

1996; Volume: 21; Issue: 23 Linguagem: Inglês

10.1097/00007632-199612010-00005

0887-9869

M Ogon, Christian Haid, Martin Krismer, W. Sterzinger, R. Bauer,

Scoliosis diagnosis and treatment

The advantage to fixation strength of triangulated, double-screw fixation compared with that of single-screw instrumentation in anterior spine surgery was evaluated by in vitro testing.To compare the fixation strength of single-screw instrumentation with ventral derotation spondylodesis screws with the fixation strength of triangulated, double-screw instrumentation with Cotrel-Dubousset-Hopf screws. Resistance against pull-out load and against load perpendicular to the axis of the screws was evaluated. To avoid the bias caused by different screw design, the pull-out strength of single screws of both devices was compared first.To the authors' knowledge, no study comparing anterior single with triangulated screws has been published.A pull-out test was performed when one vertebra in each spine specimen was instrumented with a ventral derotation spondylodesis screw, one with an isolated Cotrel-Dubousset-Hopf screws, and one with two triangulated, Cotrel-Dubousset-Hopf screws linked by a Cotrel-Dubousset-Hopf block. Load perpendicular to the axis of the screw was applied on the bone-device interface after instrumentation of further specimens with ventral derotation spondylodesis and triangulated, Cotrel-Dubousset-Hopf devices.Use of isolated Cotrel-Dubousset-Hopf screws compared with ventral derotation spondylodesis screws showed no significant differences in pull-out strength. The use of triangulated, double-screw fixation with Cotrel-Dubousset-Hopf screws led to a significant 79% increase in resistance against pull-out and a 73% increase in resistance against load perpendicular to the screw axis compared with the resistance produced using ventral derotation spondylodesis single-screw instrumentation.In anterior surgery, fixation of the vertebra-device interface can be improved considerably by application of two triangulated screws.