The process of subsidence after cervical stabilizations by cage alone, cage with plate and plate-cage. A biomechanical comparative study.
OBJECTIVE
Clinical observations show that subsidence of cervical interbody implants takes place in the early postoperative period. Additional plating or use of a plate-cage is thought to be helpful to avoid excessive subsidence. We performed a biomechanical comparative study to assess the process of subsidence after the use of three different cervical stabilization methods.


METHODS
Porcine cervical specimens after anterior discectomy were stabilized by a cage alone (n=6), cage with plate (n=6) and a plate-cage (n=6), and were exposed to 21 000 cycles of 20-200 N cyclic axial loads with frequency of 2.5 Hz. Size of subsidence was continually calculated by the software of the testing machine. One-way ANOVA test was applied for statistical evaluation.


RESULTS
The test revealed two phases in the course of subsidence: an initial phase and a final one. In the initial phase rapid increase of subsidence occurred. Velocity and size of subsidence in this phase differed significantly between the stabilizing systems. The fastest and biggest subsidence occurred in the case of the cage alone, less subsidence was noted for the cage with plate and the least for the plate-cage. The final phase of the subsidence was markedly slower and longer. Velocity and size in this phase were the biggest for the cage alone. The differences between the cage with plate and the plate-cage in that phase were not significant.


CONCLUSIONS
The study shows that subsidence occurs in two phases irrespective of the type of cervical stabilization and this finding confirms similar clinical observations. Additional plating can be helpful in controlling the course of subsidence.
Hakało
Jerzy
J
hakalo@poczta.onet.pl
Pezowicz
Celina
C
Wroński
Jerzy
J
Bedziński
Romuald
R
Kasprowicz
Magdalena
M
D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D001860:Bone Plates; D002574:Cervical Vertebrae / Q000502:physiology* / Q000601:surgery*; D005260:Female; D008422:Materials Testing; D009068:Movement / Q000502:physiology*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013552:Swine