BACKGROUND: Previous studies of peripheral nerve mechanical properties in animals have utilized one-dimensional drawing methods. OBJECTIVE: To analyze the effects of brachial plexus injury anastomosis simulation on biomechanical properties of adult brachial plexus by observing tensile mechanical properties, stress relaxation, and creep deformation of the brachial plexus in normal human cadavers and brachial plexus from simulated brachial plexus injury anastomosis samples. DESIGN, TIME AND SETTING: The in vitro experiment was performed at the Mechanics Experimental Center, Jilin University, China from April to May 2007. MATERIALS: A total of six adult, male cadavers, who had died from acute trauma, and were aged 20-29 years, were supplied by the Research Room of Anatomy, Medical Department, Jilin University, China. AG-10TA Universal Material Testing Machine (Shimadzu, Japan) was used in this study. METHODS: A total of 36 samples of fresh brachial plexus were collected from the cadavers, comprising 12 C_5 nerve roots, 12 C_6 nerve roots at the left and right sides of the superior truck, and 12 C_7 nerve roots at the middle truck. The C_5 and C_6 nerve roots were processed into 50 samples and the C_7 nerve roots into 24 samples. A total of 36 C_5 and C_6 nerve root samples were randomly assigned to a non-surgery control group (n = 18) and brachial plexus injury anastomosis simulation group (n = 18). Brachial plexus injury simulation anastomosis samples underwent an incision in the middle, and then received anastomosis. Samples in both groups underwent a tension test at 5 mm/min on the AG-10TA universal material testing machine. A total of 24 samples from the C_6 superior trunk and C_7 middle trunk of the brachial plexus were subjected to stress relaxation and creep tests. Test duration was 7 200 seconds. A total of 100 data points were collected and analyzed using a normalization method. MAIN OUTCOME MEASURES: The following parameters were measured: tension maximum displacement, maximum load, maximum stress, maximum strain and stress-strain curve, stress relaxation at 7 200 seconds, creep deformation at 7 200 seconds, stress relaxation, and creep curve in the non-surgery control group and brachial plexus injury simulation anastomosis group. RESULTS: The tension maximum load of brachial plexus was (140.36 ± 30.50) N, maximum stress was (10.67 ± 2.52) MPa, maximum displacement was (7.78 ± 1.48) mm, and maximum strain was (31.64 ± 5.32)% in the non-surgery control group. The tension maximum load of brachial plexus was (93.23 ± 20.65) N, maximum stress was (7.09 ± 1.57) MPa, maximum displacement was (6.13 ± 0.86) mm,and maximum strain was (24.55 ± 3.45)% in the brachial plexus injury simulation anastomosis group. The above-mentioned indices were greater in the non-surgery control group than in the brachial plexus injury simulation anastomosis group (P < 0.01). Stress relaxation at 7 200 seconds was 2.07 MPa and 2.11 MPa, respectively, in the non-surgery control and brachial plexus injury simulation anastomosis groups. Creep deformation at 7 200 seconds was 4.68% and 3.52%, respectively, in the non-surgery control and brachial plexus injury simulation anastomosis groups. CONCLUSION: Decreased tension maximum load, maximum displacement, maximum stress, maximum strain, and creep deformation at 7 200 seconds affected the biomechanical properties of the brachial plexus following brachial plexus injury.