Abstract
Controversy exists as to whether the biomechanical properties of a 360 lumbar fusion are influenced by the order in which the anterior and posterior components of the procedure are performed.
The fusion technique used Magerl screws to effect the posterior fusion and a Syncage implant (Stratec) to effect the anterior component of the fusion.
Isolated motion segments from calf spines were tested in each of two groups of five. In the first group the posterior fusion was performed first and in the second group the anterior fusion was performed first. Loads were applied as a dead weight of 2Nm in each range of movement of the spine (flexion/extension, lateral flexion and rotation). The range of movement was measured using the Qualisys motion analysis software linked to a set of five cameras, using external marker clusters attached to the vertebral bodies. Each motion segment was tested prior to instrumentation, post anterior or posterior instrumentation and with both anterior and posterior instrumentation.
Ranges of movement following 360 instrumentation were increased in all planes tested when posterior fixation was performed first; flexion/extension 26% v 55% (p=0.020), lateral flexion 18% v 34% (p=0.382), and rotation 18% v 73% (p=0.034).
It was concluded that posterior fixation should not be performed prior to anterior fixation as this results in a significant loss of stability in both flexion/extension and rotation
Abstracts prepared by Dr P E Watkins, Hodgkin Building, Guys Campus, King’s College London.
