Introduction:

Despite improvements in surgical technıques and instrumentation materials;solid fusion of spine is the most important part of surgical treatment.Autogenous bone grafts is the most commonly used graft type for spinal arthrodesis. Because of the problems due to graft harvesting and need ample bone graft for long fusions;allografts, osteoinductive and osteoconductive bone graft substitutes are used commonly today as an alternative to autografts. The purpose of this investigation is to develop,characterize and validale an animal model for lumbar pasteralateral arthrodesis using different graft materials.

Material and method:

Forthy adult guinea pig underwent bilateral pasteralateral spinal fusion at L2-L4 level. Ten of guinea pigs were used as negative controls. All of them underwent decortication w ithout bone grafting. Iliac crests of this animals were used as allograft source for investigation.Fresh grafts were freezed at minus 20 degrees C. Other thirty animals were subdivided to three groups. Ten of them received autograft after decortication from iliac crests at the same time during operation, second group received fresh frozen allografts of control group after decortication and the last group received hydroxyapatite tricalcium phosphate composite after decortication. Animals were killed at eight weeks and spinal fusions were analyzed by radiography,manuel stress testing ,macroscopic evaluation and light microscopy.

Results:

Fusion was not achieved in any of the control animals. Overall nonunion rate was 80 percent in allograft group, 20 percent in autograft group and 50 percent in hydroxyapatite group. Motion with manual palpatian between L2-L4 vertebral segments was 100 percent in control group, 20 percent in autograft group, 80 percent in allograft group and 30 percent in hydroxyapatite group. Light microscopic analysis. Bhowed three different and reproducible phases of spinal fusion healing.

Conclusions:

ln this animal model surgical technique ,graft healing enviroment and outcome was similar to the human surgery . The best graft material appeared in this study was autograft and the worst was fresh frozen allograft. This model prouides an opportunity for investigation of pasteralateral arthrodesis biology and mechanisms of bone formatian during spinal fusion with different graft materials.

Keywords: Autogenous bone graft, allograft, hidroxyapatite, fusion, lumbar spine, guinea pig,animal model