Sonoelastography in the Diagnosis of Carpal Tunnel Syndrome: A Systematic Review of Diagnostic Values Compared with the Normative Population

Background Sonoelastography (SEL) is widely used for assessing tissue stiffness and pathophysiology. It has also been used to diagnose carpal tunnel syndrome (CTS). However, the current criteria to diagnose CTS in SEL are diverse. The aim of this study was to systematically review the literature and assess the diagnostic value of SEL for CTS. Methods A literature review was performed using MEDLINE (PubMed), EMBASE, and the Cochrane Collaboration Library for primary research articles using the keywords sonoelastography and carpal tunnel syndrome. Data related to diagnostic and cutoff value were extracted. Bias assessment was performed. Results A total of 121 publications were reviewed. Nineteen primary case series met the inclusion criteria and were selected for full analysis. Different diagnostic approaches were identified, with units/expressions including kilopascals, conduct velocity, and strain ratio. The kilopascals and conduct velocity were measured using shear wave elastography, whereas strain ratio was calculated by relative compression quantification. A mean shear modulus cutoff value from 38.25 to 86 kPa and an acoustic radiation force impulse cutoff value of 3.0 to 3.23 m/s were used to diagnose CTS. Eight articles reported strain ratio between the median nerve and nearby tissues with diverse results due to different reference points. The other 3 additional diagnostic values were reported. Conclusions Sonoelastography is a useful noninvasive and promising modality to diagnose CTS. It may reflect both the condition of soft tissue scarring and quantitative values for CTS and median nerve stiffness. A diversity of examination values was found in different modalities. A high level of evidence was absent.