Reliability of 2D Ultrasound imaging associated with transient ShearWave Elastography method to analyze spastic gastrocnemius medialis muscle architecture and viscoelastic properties
Dr Laure MATHEVONa, Dr Fabrice MICHELb, Dr Sébastien AUBRYb, Dr Rodolphe TESTAa, Dr Thomas LAPOLEa, Mr Clément BOULARDa, Dr Bruno FERNANDEZa, Prof Bernard PARRATTEa, Prof Paul CALMELSa
a CHU Saint-Etienne, b CHU Besançon
The aim of the study was to assess the reliability of pennation angle (PA) and muscle thickness (MT) 2D measurements and of shear elastic modulus measurement, using ultrasound imaging (US). Those measurements were made on spastic gastrocnemius medialis muscle at rest and at maximal passive stretching, in post-stroke hemiplegic patients. The paretic side measurements were compared to non-paretic side.
Material and Methods:
Fourteen patients took part in 2 inter-session reliability experiments, realised at a 7 days interval by the same operator. The Aixplorer® Supersonic US scanner with the transient ShearWave Elastography (SWE) software was used. The stretching experiments were made manually and controlled by a goniometer.
The reliability of the 2D measurements was good. The coefficient of variation (CV) was 6.30% for MT measurement at rest, 6.40% and 8.26% for PA at rest and at maximal passive stretching respectively. The reliability of the shear elastic modulus measurement in the sagittal plane was good only at rest with a CV of 9.86%, versus 40.58% at stretching. None of the shear elastic modulus measurements in the axial plane were good. At rest, MT and PA were weaker on the paretic side (14.25±3.12mm and 17.32±5.10°) versus non-paretic side (16.30±3.19mm and 21.08±5.05°) (p<0.0001 and p=0.006). At rest, there was a small difference in the shear elastic modulus between the paretic side and the non-paretic side (5.40±1.67 kPa versus 6.20±2.18 kPa, p = 0.041).
This is the first description of muscle spastic structure using SWE with Supersonic Shear Imaging. 2D US associated with SWE shows promise in terms of muscular atrophy quantification and muscle histological quality assessment. These structural properties reflect some of the functional abilities regardless of motor control. It should enable further research on therapies which impact muscle tissue quality, such as botulinum neurotoxin injections.
Keywords : 2D ultrasound imaging, transient ShearWave Elastography, spastic muscle, structure, reliability.