Within- and between-day intra- and inter-rater reliability of using shear-wave elastography and myotonometry to assess erector spinae muscle stiffness in asymptomatic individuals — The International Society for the Study of the Lumbar Spine
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Within- and between-day intra- and inter-rater reliability of using shear-wave elastography and myotonometry to assess erector spinae muscle stiffness in asymptomatic individuals (#1211)

George Chan 1 , Tim Chan 1 , Phoebe Cheung 1 , Janice Ho 1 , Phoebe Ng 1 , Dino Samartzis 2 , Arnold Wong 1
  1. Department of Rehabilitation Sciences , The Hong Kong Polytechnic University, Hong Kong SAR, China
  2. Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA

 

INTRODUCTION

Although separate studies have used shear wave elastography (SWE) and myotonometry to objectively quantify soft tissue stiffness, the within- and between-day intra- and inter-rater reliability of novice examiners in using these technologies to measure the paraspinal muscle stiffness remains unknown. Importantly, no studies have determined the sensitivity of SWE and myotonometry in detecting temporal changes in paraspinal muscle stiffness, which may limit their clinical applications. Therefore, the current study aimed to: (1) determine the within- and between-day intra- and inter-rater reliability of SWE and myotonometry in quantifying resting erector spinae (ES) stiffness; (2) measure changes in ES stiffness immediately after a back extensor fatigue regimen; and (3) estimate the correlation between ES stiffness estimated by the two methods.

 

METHODS

Left ES resting stiffness values of 30 prone lying volunteers (average age:21±0.69 years; 50% females) were measured twice by 2 newly trained examiners using a SWE device and a handheld myotonometer each. Volunteers then performed back extension in prone until experiencing subjective fatigue. Both examiners immediately repeated the muscle stiffness measurements. The volunteers returned 3-4 days later to undergo the same procedure. The within- and between-day intra- and inter-rater reliability of using both devices to measure ES stiffness were evaluated by intra-class correlation coefficients model 3 (ICC3,3). Temporal changes in ES stiffness as measured by SWE and myotonometry were assessed by separate paired t-tests. The correlation between the measured baseline ES stiffness by SWE and myotonometry was assessed by the Pearson product-moment coefficient (r)

 

RESULTS

Within-day intra- and inter-rater reliability estimates for SWE and myotonometry stiffness measurements were ICC3,3>0.87 and ICC3,3>0.97, respectively (p<0.05). Between-day intra- and inter-rater reliability estimates for ES stiffness measurements using SWE and myotonometry were from 0.50 to 0.68 and >0.92, respectively. Both devices showed significant increases in post-fatigue resting ES stiffness (p<0.05). Baseline ES stiffness values measured by SWE were significantly correlated to those by myotonometry (r = 0.28).

 

DISCUSSION

Novice examiners showed excellent within- and between-day intra- and inter-rater reliability in using myotonometry to measure stiffness. However, the between-day intra- and inter-rater reliability estimates of ES stiffness measured by SWE was fair to moderate. Given the high reliability, portability, and relatively low cost of handheld myotonometers, they can be handy tools for quantifying back muscle stiffness in clinical practice and research. Future studies should establish the within- and between-day intra- and inter-rater reliability of using the two technologies to measure ES stiffness in people with low back pain.

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