Acoustic Radiation Force Impulse Imaging Of Peripheral Enthesopathy In Patients With Ankylosing Spondylitis

Objective To evaluate the value of Acoustic Radiation Force Impulse(ARFI)Imaging in evaluating peripheral enthesopathy in patients with ankylosing spondylitis(AS)and to explore the elastic characteristic of peripheral entheses.Methods Thirty-five consecutive AS patients and 35 asymptomatic healthy subjects were enrolled.All patients fulfilled the modified New York criteria for AS diagnosis.Patients’ demographic and clinical data,functional parameters,radiographic findings,and therapeutic method were recorded down.Firstly,B-mode ultrasound and Color Doppler ultrasound were carried out at fIve entheseal sites(quadriceps tendon enthesis,proximal insertion of the patellar tendon,distal insertion of the patellar tendon,the Achilles tendon enthesis,and plantar aponeurosis enthesis)bilaterally,and the presence or absence of increased tendon thickness,bursitis,intratendinous calcifications,cortical reactive changes(cortical irregularity,insertional bone erosions,enthesophytes),and regional blood flow were assessed.Then,Virtual Touch Tissue Quantification(VTQ)was used to assess a quantitative tissue stiffness by measuring Shear Wave Velocity(SWV)at four entheseal sites(quadriceps tendon enthesis,proximal insertion of the patellar tendon,distal insertion of the patellar tendon,and the Achilles tendon enthesis)bilaterally.For each part,a total of five successful measurements were made,the median of all 5 measurements per part was calculated and used for further analysis.The probe was held perpendicular to the tendon while performing the examination to avoid anisotropy and the probe was moved gently with no downward pressure.All examinations were performed in longitudinal and transverse planes.Results1.The incidence and mean total score of enthesopathy in AS patients were higher than that in controls(p = 0.000,0.003,respectively).The incidence of enthesopathy of every entheseal sites in AS patients was higher than that in controls(p = 0.019,0.000,0.000,0.001,0.015,respectively).The incidence of enthesopathy was notidentical in different entheseal sites(The incidence of enthesopathy in distal insertion of the patellar tendon was highest,followed by quadriceps tendon enthesis,proximal insertion of the patellar tendon the Achilles tendon enthesis,and plantar aponeurosis enthesis)and there was significant difference of abnormal ultrasonic manifestations in different entheseal sites(The incidence of increased tendon thickness was highest,followed by bursitis,cortical reactive changes,intratendinous calcifications,and regional blood flow).2.Mean shear wave velocities of the eight entheseal sites in patients with AS were lower than those in controls significantly in longitudinal planes,but there were significant difference in the left quadriceps tendon enthesis and bilateral proximal insertion of the patellar tendon(p = 0.040,0.018,0.015,respectively).Mean shear wave velocities of the eight entheseal sites had no significant difference in transverse planes in patients compared with controls(p > 0.05)..3.Mean shear wave velocities were significantly higher in longitudinal planes compared with transverse planes both in the patients and controls(p = 0.000).4.Mean shear wave velocities of the eight entheseal sites had no significant difference between three disease duration groups in patients(p > 0.05).Conclusion1.The incidence of enthesopathy in AS patients were higher than that in controls.The incidence of enthesopathy were not identical in different entheseal sites and there were different abnormal ultrasonic manifestations in different entheseal sites.2.ARFI may be useful for the evaluation of enthesopathy in patients with AS and can be used as a supplementary means to conventional US;in addition;it may be useful for the evaluation of other inflammatory rheumatic conditions and tendon injury.However,in the future researches aiming to evaluate peripheral entheses using Acoustic Radiation Force Impulse Imaging,longitudinal section is recommended as a standard scan.