BACKGROUND:Interlocking intramedullary nailing exhibits unique superiority in treatment of multi-segment radial fracture,bone nonunion,and osteoporotic fracture. However,distal interlocking screw placement would injury the deep branch of radial nerves. OBJECTIVE:To analyze the anatomical characteristics of the deep branch of radial nerves during radial interlocking intramedullary nailing. DESIGN,TIME AND SETTING:An observational measurement was performed at the laboratory of Department of Orthopedics,Second Affiliated Hospital of Soochow University between November and December 2002. MATERIALS:A total of 44 pieces of fresh adult cadaver forearm specimens were provided by Department of Anatomy,Soochow University,China. A vernier caliper was purchased from Henan Yuanyang Zhenhua Instrument Factory,China. METHODS:The deep branches of radial nerve of 44 fresh forearm specimens were exposed. The lateral epicondyle of humerus was joined to the Lister tubercle of radius. The line passed through 6 horizontal planes,which were as follows in sequence:0,1.0,1.5,and 2.0 cm lower than the articular surface of radial head respectively,the horizontal planes of the deep branch of radial nerve entering the supinator and winding across the radius. The crossed points were named points A,B,C,D,E,and F accordingly. MAIN OUTCOME MEASURES:The distance between the deep branch of radial nerve and fixed points B,C,and D was measured separately when the forearm was kept in pronation,neutral and supination positions. RESULTS:The distance between the deep branch of radial nerve and fixed points B,C,D became nearer and nearer in the sequence of B,C,and D. With the forearm in pronation,neutral and supination positions in sequence,each fixed point became farther and farther from the deep branch of radial nerve. CONCLUSION:When interlocking intremedullary nailing is used to fix radius,it is relatively safe to keep the forearm in neutral and flexion positions,and drilling and insertion of distal interlocking screw at 1.5 cm lower the articular surface of radial head from the posterolateral to anteromedial approach should be selected.