Ultrasound imaging of the abdominal muscles and bladder: implications for the clinical assessment of individuals with lumbopelvic pain

Abstract

Lumbopelvic pain (LPP) is associated with altered abdominal muscle function yet few tools exist that enable physiotherapists to identify these changes in a clinical setting. Ultrasound imaging (USI) has potential however its ability to detect altered abdominal muscle function and associated changes in bladder base (BB) position during tests common to a physiotherapy assessment of LPP, has yet to be established. The aims of this research were to determine the validity and reliability of USI technique in a clinical setting, investigate the relationship between changes in abdominal muscle thickness and electrical activity, and compare sonographic characteristics of the abdominal wall, and BB position, between persons with and without LPP. Validity results indicate that 5º-10º of angular, and 8mm of inward/outward transducer motion don’t produce measurement error, and that transducer motion can be kept within these thresholds during two commonly used clinical tests; the Active Straight Leg Raise (ASLR) test and Abdominal Drawing in Manoeuvre (ADIM). Regarding reliability, measurements of abdominal muscle thickness, inter-recti distance (IRD) and BB position (healthy and LPP cohorts) during the ASLR and ADIM were good to excellent (within day ICC; 0.84-0.99, between day; 0.80-0.99). Crosscorrelation functions examining the relationship between changes in abdominal muscle thickness and activity during an ASLR and ADIM were low (r=0.22-0.40), and associated time lags large (-0.44-1.15s), suggesting that changes in muscle thickness represent more than changes in electrical activity. On comparing sonographic features between cohorts a series of features were identified that differed between the groups. Specifically, the LPP cohort had a thinner rectus abdominis (p<0.001), thicker perimuscular connective tissue (p=0.007), a wider IRD (p=0.005) and demonstrated smaller increases in TrA thickness (p ~ 0.00-0.05), and greater BB descent (p=0.02-0.03) during the ASLR. To determine if these sonographic features assist in discriminating LPP a statistical classification technique was piloted. Preliminary results identified a set of 14 sonographic features that classified LPP participants with 84% accuracy. These findings support an argument regarding the clinical value of USI and serve as the basis for future investigations aimed at determining if USI enhances the assessment, and ultimately treatment, of individuals with LPP.

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Identifiers

ORCID for M. Stokes: orcid.org/0000-0002-4204-0890

ORCID for V.F. Humphrey: orcid.org/0000-0002-3580-5373

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