EFFECTIVENESS OF SKELETAL STEM CELLS IN EXPERIMENTAL SPINAL FUSION

Abstract

Posterolateral spinal fusion is considered one of the most challenging condition for bone graft substitutes since using autogenous bone graft pseudarthrosis have been reported in 30% of cases.

MATERIALS AND METHODS.We develop a model of posterolateral spinal fusion in the rabbit based on skeletal stem cells (SSCs) loaded into a coral-hydroxyapatite material (Pro-Osteon 500RTM). 15 rabbits received cell-material constructs, 15 rabbits were sham-operated (decortication of transverse apophyses), 15 rabbits received material alone. The animals were housed for 6 months and radiographically monitored. At sacrifice, the explanted spine was analyzed by conventional and high resolution (Faxitron) radiography, and the outcome judged, blind of histology results, by two orthopedic surgeons.

RESULTS: radiographic evaluation showed a fusion rate rate of 90% in animals treated with cell constructs or biomaterial alone, and no fusion in the sham controls. Histology revealed abundant new bone formation directly on the scaffold in the cell construct and biomaterial alone groups, but no evidence of bone formation in the midregion of the interapophyseal space, where poorly vascular, dense fibrous tissue was observed.

CONCLUSIONS: The study shows that:

1. 1) the cell-biomaterial constructs which per se were highly efficient in previous animal studies, used in different absolute quantities but identical ratios were not efficient in the direct preclinical model.

2. 2) Radiography alone is misleading.

3. 3) Once efficient cell and material preparations are obtained, additional consideration must be given to specific circumstances of the pre-clinical and clinical application such as mobility of the graft and its component and vascularization of the graft bed.