Objective To research the relationship between amyotrophy,myofibrosis and time of denervation,explore a safe,non-traumatic and precise examination which can be theoretically helpful in selection of neural restoration deadline in clinic.Methods 48 biceps brachii of 48 patients′ injured arms were included and divided into 5 groups(10 patients of 0-3 months,14 patients of 3-6 months,8 patients of 6-12 months,8 patients of 1-2 years,8 patients of 2 years or more).The control group was 48 biceps brachii of patients′ uninjured arms.We took advantage of B-ultrasound in examing the injured arms,comparing to the uninjured arms,and evaluated the accuracy of B-ultrasound in examing amyotrophy,the pathological appearances as key criterion.Results As time of neural denervation prolonged,amyotrophy and myofibrosis became more and more serious,sectional areas of muscles became less and less,though fatty tissue was observed proliferating.B-ultrasound showed the ratio of sectional area of high-level echo in the injured arms decreased comparing to that of uninjured arms as the time prolonged,which coincided with pathological outcome.Conclusion B-ultrasound can observe state of amyotrophy after denervation well,which is crucial in neural restoration at the later period