Abstract
Introduction: Occipito-cervical fusion has evolved from the used of simple onlay bone grafts to the use of sophisticated modular implants. Initial stiffness prevents micromotion and allows a higher fusion rate.
Methods: A composite occipito-cervical model (OCM) was developed and validated using data obtained from cadaveric specimens. A jig was designed to pot the OCM, which allowed the application of independent moment forces to simulate flexion, extension, lateral flexion and rotation. The following implants were used 1 ) Grob plate with C1/C2 transarticular screw fixation.2) Grob Plate without C1/C2 transarticular screw fixation.3) Cervifix rod system 4) A Ransford loop system 5.) Olerud plate fixation. A three dimensional ultrasonic motion analysis system (Zebris Inc.) was used to record motion at three positions: 1)C0 2) C2 3) C4.A separate OCM was used for each instrumentation system.
Results: The Grob plate with C1/C2 transarticular fixation was found to confer the greatest initial stiffness. The Ransford loop construct was found to confer the least initial stiffness. Plate fixation offered greater stability then rod or loop constructs. We found the three dimensional motion analysis system to be ideal for displacement analysis in complex spinal instrumentation constructs.
The abstracts were prepared by Mr Ray Moran. Correspondence should be addressed to him at the Irish Orthopaedic Association, Secretariat, c/o Cappagh Orthopaedic Hospital, Finglas, Dublin
