Objective To study the ultrasonic appearances of the internal structures of normal cubital tunnel with high-resolution ultrasonography in order to establish the normal reference ranges of ultrasonic measurement of normal cubital tunnel． Methods High-frequency ultrasonography examinations were performed on 260 normal cubital tunnels of 130 cases，focusing on the ultrasonic appearance，shape，size and anatomic relationship of the ulnar nerve and the arcuate ligament when the elbow were extending or flexing． With the elbow flexing，the relationship between ulnar nerve and the medial epicondyle were observed，with the elbow extending，cross section areas of ulnar nerve，thickness of arcuate ligament，width and height of the cubital tunnel were measured． Cross section area of different elbow movement were measured too． Results 1． High-frequency ultrasound can clearly depicted the ulnar nerve and the arcuate ligament on both transverse and sagittal planes． 2． Incidence rate of ulnar nerve dislocation was 8． 7% ( 11 /130 ) ． 3． Cross section areas of ulnar nerve at the point of humeral epicondyle was 6． 68 ± 1． 57mm2 when the elbow was extension，and 5． 60 ± 1． 45mm2 when the elbow was flexion． The thickness of the arcuate ligament was 1． 14 ± 0． 26 mm，the width and the height of the cubital tunnel was 7． 66 ± 1． 30mm and 17． 69 ± 2． 81mm， respectively． Conclusions High-frequency ultrasonography depicts clearly the configuration，dimension and anatomical relationship of the ulnar nerve and arcuate ligament of the cubital tunnel，and can enable accurate measurement of these structures．

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