The Experimental Study Of Using Glue-like E-Matrix In Rat Posterolateral Fusion

[Objective]To study the effect of glue-like E-matrix, as a new carrier for the rhBMP-2, in the rat lumbar spine posterolateral arthrodesis model and to test the safety of E-matrix in the rat soft tissue inflammation model.[Methods]Male Lewis rats aged 8 weeks to 16 weeks were divided into experimental groups and control groups. Each group underwent the lumbar spine posterolateral fusion at L4-L5 by the same surgeon and same procedures.ACS/E-Matrix/rhBMP-2 compounds were implanted at the transverse process of L4 and L5 in experimental groups and ACS/rhBMP-2 compounds in the control groups. According to the study design, different dosages of rhBMP-2 with/without E-Matrix were tested .The results of fusion were evaluated by postoperative anterior-posterior x-ray, manual palpation, micro-CT analysis and histology. To build a soft tissue inflammation model, ACS/rhBMP-2 or ACS /E-Matrix /rhBMP-2 were implanted on both sides of the spine, one side in the erector spinae and the other was put subcutaneously. The areas with implants were scanned by the MRI on 0,2nd,4th,7th day after surgery.To assess the safety of the E-Matrix by the comparision of the maximum area of the tissue inflammation on T2 images using MIPAV software.[Results]In control groups, all the rats with 10μg rhBMP-2 and 3μg rhBMP-2 were found fused(100%),four rats of ten in 1μg rhBMP-2 fused(40%),one rat of ten in 0.5μg rhBMP-2 fused(10%).In experimental groups, all the rats with (3,1 and 0.5)μg rhBMP-2/E-Matrix /ACS were found fused(100%),but no rats with 0.1μg rhBMP-2 or 0.05μg rhBMP-2 plus E-Matrix found fused(0%).The micro-CT results revealed that the volume of the new bone staff created in the 10μg rhBMP-2 group and 3μg rhBMP-2/E-Matrix were similar. The soft tissue inflammation would reach the peak on the 2nd day following surgery no matter the implant put in the muscle or subcutaneously. The inflammation caused by the rhBMP-2 was more serious than that caused by E-Matrix. It didn't increase the soft tissue inflammation if adding the E-Matrix to the rhBMP-2.In contrast, using E-Matrix /rhBMP-2 compounds may decrease the soft tissue inflammation.[Conclusions]E-Matrix is an effective and safe carrier for the rhBMP-2.As a new carrier, it will help enhance the fusion rate of rhBMP-2 significantly in rat model. By using E-Matrix, we can reduce the dosage of rhBMP-2 and achieve the same effect of higher dosage of rhBMP-2.But once the dosage of rhBMP-2 is too small, we can not get the expected fusion, even with the e-matrix as a carrier. The more important is that using the compounds will tend to decrease the soft tissue inflammation in certain degree, therefore it is relatively safe.