Contribution of shear wave elastography in evaluation of the deltoid in reverse shoulder arthroplasty: reproducibility study and preliminary results

Aims: The current difficulty of reverse shoulder arthroplasty (RSA) is soft tissue management, and adequate deltoid tension and at present there is no consensus and available tools (X-ray, MRI, EMG) remain difficult to apply in clinical follow-up. The objective of this study was (1) to determine reliability and feasibility of deltoid elasticity assessment using ultrasound elastography and (2) to assess the change of deltoid stiffness after RSA by comparing shear wave speed (SWS) between healthy and RSA shoulders. Material and methods: Twenty-six healthy (native shoulder, painless and complete range of motion) subjects and twelve patients with RSA were included. Two independent investigators performed 3 measurements on each segment. Measurements were bilateral. Anterior segment was also evaluated at 45 degrees and 60 degrees of passive abduction. Reliability and feasibility have been assessed (ISO5725-standard). Results: Coefficient of measurements variation was less than 6.1% and 0.13 m/s. In the healthy group, SWS was not significantly different between anterior and middle segments; however, the SWS of the posterior segment was significantly lower than others (p<0.0001). In abduction position, compared to the rest position, SWS of the anterior segment decreased at 45 degrees abduction (p=0.0003) and increased at 60 degrees abduction (p<0.0001). Variability of measurement was higher in the RSA group. No significant difference was found between the SWS measurement of the operated and non-operated side. SWS measurements of the operated side of the anterior and middle segment were significantly higher compared to the healthy group. In abduction position, compared to rest position, no difference in SWS of the anterior segment was found at 45 degrees abduction (p=0.71) and nor at 60 degrees abduction (p=0.75). Conclusion: This study demonstrated feasibility and reliability of shoulder assessment with shear wave elastography. Reference values for asymptomatic patients can already be used in future studies on shoulder pathology and surgery.