[The effect of the quantitative variation of autologous spongy bone graft applied for bone regeneration in an experimental model of tibia osteotomy].

This study aimed at studying the influence of the quantitative variation of the autologous spongy bone graft on its osteogenic properties by virtue of the fact that its attainment has inconveniences of significant morbidity at local donor level and the limited quantity of grafting able to be obtained. Recourse was made to an osteotomy model for this purpose with the removal of a small 4 mm segment at the mid-diaphysis of the left tibia of twenty one sheep, stabilised by an osteosynthesis plate on which different quantities of autografting spongy bone were applied so that the referred bone defect (1) would not to be completely filled (1.5 g), (2) would be filled without any compression (3 g) and (3) would be filled with an excessive quantity (5 g) (n=5/each group). (4) A control osteotomy (n=6) was also carried out where the bone defect remained empty. Comparison of the evolution of bone regeneration during the postoperative period of 12 weeks was carried out by means of conventional radiographic exams and optical densitometry analysis and by radiological bone densitometry (DEXA--Dual-Energy X-ray Absorptiometry), bone histomorphometry and histological analysis after the animals' euthanasia. Optical density was significantly affected (p<0.0001) by the treatment and by time and with significant differences between the various groups under study over the same time of post-operative period: during immediate postoperative and on the 2nd (p <0.01), 4th (p <0.001), 6th and 8th weeks (p <0.05), but not on the 10th and 12th (p >0.05) post-operative weeks. Bone mineral density (BMD), obtained by DEXA, was 0.4347 +/- 0.3821 g/cm2 in the control group and 0.7482 +/- 0.2327 g/cm2, 0.9517 +/- 0.2292 g/cm2 e 1.0409 +/- 0.0681 g/cm2 in the groups that had received 1.5 g, 3g and 5 g of bone graft, respectively. The BV was 39.2 +/- 24.4% with the control group and 62.0 +/- 14.4%, 76.0 +/- 15.2% and 84.0+/-4.2% in the groups that had received 1.5 g, 3g and 5 g of bone graft, respectively. The BMD and BV were significantly affected (p<0.05 and p <0.01, respectively) by the treatment, nevertheless, there were no significant differences (p >0.05) between the groups that had received the largest volumes of autografting spongy bone on the 12th week of the post-operative period.The conclusion was reached that there was no advantage in excessively filling an osteotomy gap with autografting spongy bone and attainment of only the volume strictly required to fill the osteotomy gap at issue was needed.