High-frequency Ultrasound Study Of The Cubital Tunnel: Normal Measurement And Clinical Implication

Objective:To study the ultrasonic appearances and measure the dimensions of the internal structures of normal cubital tunnel with high-resolution ultrasonography in order to establish the normal reference ranges.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.With the elbow flexing ,observed the relationship between ulnar nerve and the medial epicondyle(When ulnar nerve move anterior to the top of medial epicondyle or across medial epicondyle,we called it the ulnar nerve dislocation).Following measurements were done: cross section areas of ulnar nerve, thickness of arcuate ligament, width and height of the cubital tunnel. Statistical analysis was carried out to address the correlation between the ultrasonic measurements and other variables like sex, age, body weight and height, and arm circumference.Results: 1.High-frequency ultrasound can clearly depicted the ulnar nerve and the arcuate ligament on both transverse and sagittal planes. (1)The ulnar nerve was shown to be hypoechoic round or oval dots on cross-sectional images, surrounded by a zone of slightly hyperechogenicity. On the other hand, the arcuate ligament was slightly hyperechoic structures. (2)Both appeared as linear structures at longitudinal planes with similar echo features as the transversal plane. 2.When the elow flexed,the ulnar nerve moved anteriorly,some of them move to the tip of the medial epicondyle or cross of it.In this study,the incidence rate of ulnar nerve dislocation was 8.7%(11/130).3.The 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±0.26mm,the width and the height of the cubital tunnel was 7.66±1.30mm and 17.69±2.81mm.4.The width and the height of the cubital tunnel had relationship with the body weight and height(r>0.70,P<0.05),but no relation with sex,age and arm circumferenc(eP>0.05). There was no obvious relationship between the other indexes with the sex, age, body weight and height, and arm circumference(P>0.05).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. Such information will be very helpful in the diagnosis and management of patients with cubital tunnel syndrome.