Evaluation of the Agreement Between Ultrasound-Based and Bi-Planar X-Ray Radiography-Based Assessment of the Geometrical Features of the Ischial Tuberosity in the Context of the Prevention of Seating-Related Pressure Injury

Abstract

The proper management of the local mechanical environment within soft tissues is a key challenge central the prevention of Pressure Ulcers (PUs). Magnetic Resonance (MR) imaging is the preferred imaging modality to measure geometrical features associated with PUs. It is a very time-consuming method and it represents a major barrier to the clinical translation of risk assessment tools. There is a growing enthusiasm of the community for the use of B-mode ultrasound imaging as a practical, alternative technology suitable for bedside or outpatient clinic use. The objective was to evaluate the agreement between US-derived measurements and bi-planar X-ray radiography-derived measurements of geometrical features of the Ischial Tuberosity in a realistic loaded sitting position in healthy volunteers. The reproducibility of the US-based assessment of radii of curvature, evaluated in a subset of 4 subjects using the IS0 5725-2 framework was 1.7 mm and 1.3 mm in the in the frontal and sagittal plane respectively (95 % CI = 3.5 mm and = 2.6 mm respectively). Out of the 13 subjects included, the ischial tuberosity border was visible on the US image of 7 healthy subjects only. The mean of differences computed on the 7 subjects using Bland-Altman plots were +3.3 mm and -5.7 mm in the frontal and sagittal planes respectively. The corresponding 95% CI in the frontal and sagittal planes were respectively 1.8 mm and 3.7 mm. These differences however were not statistically significant (Wilcoxon signed-rank test). More effort is needed to establish and standardise optimal measurement procedures and test protocols for the assessment of geometrical features of the IT using US.