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Volumetric MRI is a promising outcome measure of muscle reinnervation

Research output: Contribution to journalArticlepeer-review

Matthew Wilcox, Liane Dos Santos Canas, Rikin Hargunani, Tom Tidswell, Hazel Brown, Marc Modat, James Benjamin Phillips, Sebastien Ourselin, Tom Quick

Original languageEnglish
Article number22433
JournalScientific Reports
Issue number1
Early online date17 Nov 2021
E-pub ahead of print17 Nov 2021
PublishedDec 2021

Bibliographical note

Funding Information: This work was funded by the Royal National Orthopaedic Hospital Charitable Trust to TQ, England Golf Trust to MW and a UCL Graduate Research Scholarship to MW. Author J.P was also supported by funding from the Engineering and Physical Sciences Research Council (ESPRC) EP/R004463/1. Publisher Copyright: © 2021, The Author(s).

King's Authors


The development of outcome measures that can track the recovery of reinnervated muscle would benefit the clinical investigation of new therapies which hope to enhance peripheral nerve repair. The primary objective of this study was to assess the validity of volumetric Magnetic Resonance Imaging (MRI) as an outcome measure of muscle reinnervation by testing its reproducibility, responsiveness and relationship with clinical indices of muscular function. Over a 3-year period 25 patients who underwent nerve transfer to reinnervate elbow flexor muscles were assessed using intramuscular electromyography (EMG) and MRI (median post-operative assessment time of 258 days, ranging from 86 days pre-operatively to 1698 days post- operatively). Muscle power (Medical Research Council (MRC) grade) and Stanmore Percentage of Normal Elbow Assessment (SPONEA) assessment was also recorded for all patients. Sub-analysis of peak volitional force (PVF), muscular fatigue and co-contraction was performed in those patients with MRC > 3. The responsiveness of each parameter was compared using Pearson or Spearman correlation. A Hierarchical Gaussian Process (HGP) was implemented to determine the ability of volumetric MRI measurements to predict the recovery of muscular function. Reinnervated muscle volume per unit Body Mass Index (BMI) demonstrated good responsiveness (R2 = 0.73, p < 0.001). Using the temporal and muscle volume per unit BMI data, a HGP model was able to predict MRC grade and SPONEA with a mean absolute error (MAE) of 0.73 and 1.7 respectively. Muscle volume per unit BMI demonstrated moderate to good positive correlations with patient reported impairments of reinnervated muscle; co- contraction (R2 = 0.63, p = 0.02) and muscle fatigue (R2 = 0.64, p = 0.04). In summary, volumetric MRI analysis of reinnervated muscle is highly reproducible, responsive to post-operative time and demonstrates correlation with clinical indices of muscle function. This encourages the view that volumetric MRI is a promising outcome measure for muscle reinnervation which will drive advancements in motor recovery therapy.

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