[The finite element analysis of polyetheretherketone/hydroxyapatite/carbon fiber cage]

To compare the bio-mechanical characteristics of cages of two types, i. e., polyetheretherketone/ hydroxyapatite/carbon fiber (PEEK/HA/CF) and titanium combined with internal pedicle screw fixation in lumbar model, and to provide experimental evidences for clinical application, we constructed a three-dimensional finite element model of an intact L2-L4 segment by using computer tomography scans of a healthy male. The three-dimensional finite element models of an intact L2-L4 segment and single cage plus bilateral vertebral pedicle screw fixation were established. The angular motion of fused segment and stress distribution in the bone graft and cage and L3 inferior endplate under different loads were recorded. The result showed that the peak Von Mises stresses of the bone graft of PEEK/HA/CF group were at least 2.2 time as that of titanium group. The peak Von Mises stresses of L3 inferior endplate of the titanium group were at least 2. 3 times as that of PEEK/HA/CF group. These stresses were concentrated at places where the cage interfaced with the endplate. The angular variation of the titanium group showed similarity to PEEK/HA/CF group. The PEEK/HA/CF cage could provide stability similar to that of titanium cage in the presence of posterior instrumentation. It could increase the load transfer through the bone graft and promote the bone fusion. It could also reduce the stresses in endplates adjacent to the cage and reduce the subsidence of the cage.