Quantitative Evaluation Of Denervated Muscle Atrophy With Shear Wave Ultrasound Elastography In An Animal Model

Purpose This study was to explore the efficacy of shear wave ultrasound elastography(SWUE)for quantitative evaluation of denervated muscle atrophy in a rabbit model,and compare elastic modulus with the histopathological parameters.Materials and Methods Forty Japan's big white male rabbits were randomly divided into four groups:group A(n =10):without sciatic nerve axotomy at baseline,group B(n = 10):with sciatic nerve axotomy and follow-up with 2 weeks,group C(n = 10):with sciatic nerve axotomy and follow-up with 4 weeks,group D(n = 10):with sciatic nerve axotomy and follow-up with 8 weeks.Real-time SWUE was used to measure the elastic modulus of the operated side and the unoperated side triceps surae muscle of the hind legs of the rabbits.The wet weight ratio,the muscle fiber cross-sectional area value and the collagenous fiber area value of the lower limb of the operated side and the unoperated side triceps surae muscle were measured.Then,the elastic modulus of the triceps surae muscle was compared with histopathologic parameters at baseline and at various post-denervation times(2,4 and 8 wk)with 10 animals in each group.Results Our results revealed that the elastic modulus of denervated muscle was significantly lower at 2 wk but higher at 8 wk compared with that at the baseline(p<0.05),and no significant difference was found between the elastic modulus at 4 wk and that at the baseline(p>0.05).Compared to the unoperated side,the muscle elasciticity of the operated side was lower at 2 wk but higher at 8 wk(p<0.05),and no significant difference was found at 4 wk(P>0.05).The wet-weight ratio and the muscle fiber cross-sectional area of the denervated muscle decreased gradually during the 8 wk post-denervation together with a gradual increase of the collagen fiber area from 2 wk to 8 wk(p<0.05).There was no significant difference of the unoperated side muscle fiber cross-sectional area among that at the baseline,at 2 wk,and at 4 wk,but it was lower at 8 wk.There was no significant difference of the unoperated side collagenous fiber area value of triceps surae muscle among the four groups(p>0.05).Conclusions SWUE was useful for quantitative evaluation of muscle denervation.The elastic modulus of the denervate muscle was significantly decreased at 2 wk,then increased gradually during the followd-up time.The early decrease of the muscle elastic modulus might be an early sign of the denervated muscle.