Is Sonographic Assessment of Intratendinous Blood Flow in Achilles Tendinopathy Patients Reliable? Consistency of Doppler Ultrasound Modes and Intra-and Inter-observer Reliability

Purpose: The purpose of this study was to investigate the consistency between different Doppler ultrasound (DU) modes as well as the intra-and inter-observer reliability of investigators with different experience level in assessing intratendinous blood flow (IBF) in Achilles tendinopathy patients. Material and Methods: 18 participants (36 Achilles tendons, AT) with Achilles tendinopathy (24 AT) were examined with power Doppler ultrasound (PDU), colour Doppler ultrasound (CDU) and Advanced Dynamic Flow (ADF) (Toshiba Xario SSA-660 A; 14MHz transducer) by 2 investigators (experienced, EI; inexperienced, II) in a test-retest design (M1/M2). A modified Ohberg score was used to quantify IBF. Data was analysed descriptively (absolute and relative). Consistency of the 3 modes was presented by Kendall's Coefficient of Concordance (Kendall's W). Intra-and inter-observer reliability were calculated by use of Kendall's tau b correlation coefficient. Results: IBF was detected in 79-92 % of symptomatic AT and in 33-50 % of contralateral asymptomatic AT. Comparing the 3 modes, Kendall's W ranged from 0.97-0.98. Analysis of intra-observer reliability resulted in Kendall's tau 0.90-0.92 for EI and 0.84-0.87 for II. Interobserver reliability resulted in Kendall's tau 0.64-0.69 in M1 and 0.68-0.70 in M2. Conclusion: The very good consistency between PDU, CDU and ADF indicates a comparable applicability for assessing IBF in ATs. Intra-observer reliability was high for both investigators, independent of experience. The moderate interobserver reliability reflects the challenge in sonographic detection of intratendinous blood flow (IBF) amount.