Abstract
To evaluate and describe the plain radiographic changes observed with time in fusions using SiS-CaP. We describe, for the first time, 4 stages of bone substitute fusion mass (BSFM) radiographic appearance in relation to time post-op.
Retrospective, radiological evaluation.
Over 200 plain radiographs were evaluated. 70 consecutive fusions for degenerative spinal stenosis were included, in all cases performed by the same surgeon using the same operative technique. Follow-up was from 3 months to 2 years post-op.
Radiographs were evaluated for the presence or absence of SiS-CaP granules, bone formation and for evidence of pseudarthrosis.
Trends were seen within the BSFM with respect to time. At 6-12 weeks post-op a ‘homogenous granular stage’ indicates the presence of the unchanged SiS-CaP.
At 12 weeks, small pockets appear within the BSFM in the ‘vacuolation stage’, indicating bioresorption of the graft. Vacuoles become increasingly radio-opaque indicating bone proliferation during the ‘homogenous lamellar stage’. At variable time between 6 months and 2 years, the BSFM becomes encapsulated in the ‘cortication stage’ visible as a sclerotic rim around the BSFM.
We have seen a clear trend in the behaviour of the fusion mass in this case series. The radiological stages we have described above can be closely correlated with previously reported in-vitro and in-vivo studies looking at the micro-function of SiS-CaP. We hope that this description will help to judge the progress of graft incorporation and fusion. Further study of inter and intra-observer correlation will be required.
