High-resolution Ultrsonography In The Diagnosis Of The Cubital Tunnel

ObjectiveTo determine the reliability of Ultrasonography(US) in distinguishing the anatomy of the cubital tunnel by comparing with magnetic resonance neurography(MR). To study the sonographic appearance of ulnar entrapment neuropathy and evaluate the US for diagnosing cubital tunnel syndrome through the comparing with intra-operative findings and pre-operative electrophysiological findings.Materials and Methods1,Materials1)A person without clinical symptoms of cubital tunnel syndrome and electrophysiological disorders.2) 43 arms from 42 patients with primary diagnosis of cubital tunnel syndrome in Huashan Hospital handsurgery department from 2006 to 2008.3)Healthy counter-arm(without cubital tunnel syndrome and history of peripheral Neuritis) of above patients.4)The ulnar nerve of 30 arms from 15 healthy volunteers without cubital tunnel syndrome and history of peripheral Neuritis.2,MethodsMaterial 1) was accepted both MR and US.With MR neurography images as golden standard,the sonographic anatomy of the cubital tunnel and its surrounding structures were marked.Ultrasonographic examinations were performed in material 2) to observe the morphic changes of the ulnar nerve and measure its cross sectional area(CSA) and thickness,then calculated its tumefaction ratio.Ultrasonographic examinations were also performed in material 3).The same measurement was done at corresponding sites of arms of patients.Material 4) were scaned to get the normal images of the ulnar nerve and CSA and thickness at the level of entrance,inner,exit of the cubital tunnel.Tumefaction ratio was also done as comparison.Ultrasonograghic findings were compared with intra-operative findings and electrophysiological findings to verify the accuracy and sensitivity of the test.The mearuement were compared between material 2) and material 3),material 2) and material 4),material 3) and material 4).And make receiver operator characteristic curve(ROC) to get the cut off point and calculate sensitivity and specificity at this point.ResultsTaking MR neurograhy image as the golden standard,US could perfectly reveal the anatomy of the cubital tunnel,especially the medial epicondyle,the olecranon and the ulnar nerve.The course and appearance of normal ulnar nerves:in the groove of ulnar nerve multiple hypoechoic parallel but discontinuous linear areas separated by hyperechoic bands when scanned in a longitudinal plane.The image was like echogenic of tendon,on the countrary tendons appeared to have numerous fine parallel hyperechoic lines separated by fine hypoechoic lines.At the level of the medial epicondyle scanning transversely as multiple rounded hypoechoic areas in a homogeneous hyperechoic background(fascicular or honeycomb pattern).The nerve could be found through mediale septumintermusculare,in groove of ulnar nerve and then in the deep of flexor carpi ulnaris.The appearance of cubital tunnel syndrome:at compression site the ulnar nerve became narrow or flat and turned to thickened and enlarged,and the fascicular texture turned to vague at the proximal part of the compression,even more formed pseuneuroma.The compression site couldn't be found in some patients and the nerve was only revealed swollen in cubital tunnel.The inside of nerve could be hyperechonic in patients with long course of diseases.The different pathogeny could be detected:cyst,hyperostosis of medial epicondyle,allotopia anconeus,allotopia bone,tendon and scar.Sensitivity of US was 93%.The positive rate were respectively 75%,67%,25% in patients of occupying lesion,hyperplasia and tendon compression.If electrophysiological examination combined with US,the sensitivity would rise from 79%to 100%.In the healthy people team,the thickness of nerve was 0.24±0.04cm,0.24±0.04cm,0.24±0.03cm at the level of entrance,inner,exit of the cubital tunnel respectively,and CSA was 0.07±0.02cm~2,0.07±0.02 cm~2,0.06±0.02cm~2 respectively. In the patients team,the thickness of nerve was 0.35±0.07cm and CSA was 0.19±0.07cm~2 at the proximal part of the compression.Then the thickness tumefaction ratio was 196±53%and CSA tumefaction ratio was 239±63%.In healthy counter-arm team the thickness of nerve was 0.25±0.04cm and CSA was 0.09±0.03 cm~2 at corresponding site.The difference between healthy people team and patients team and it between healthy counter-arm team and patients team were significant in statistics.But the difference between healthy people and healthy counter-arm team was not significant.From ROC of patients team and healthy counter-arm team, patients team and healthy people team,the best cut off point of CSA were both 0.11cm~2.Sensitivity was 94%and specificity was 93%at this point.And from ROC of patients team and healthy people team,the best cut off point of CSA tumefaction ratio was 142%.Sensitivity was 95%and specificity was 93%at this point.Conclusions1.High-resolution US can display cubital tunnel anatomy.2.High-resolution US can display pathological changes of ulnar nerve and the pathogeny when it was compressed in elbow and measure the ulnar nerve.3.when electrophysiology is combined with high-resolution US,the sensitivity can increase.