Poststroke spasticity significantly impairs function, particularly through the development of pes equinovarus. Botulinum toxin A (BoNT) injections into the medial gastrocnemius (MG) are a first-line treatment. Treatment outcomes and long-term responses to interventions can vary significantly between individual patients. Additionally, there is increasing concern about potential adverse effects on muscle morphology. Further research is essential to optimize treatment strategies and improve long-term outcomes in this population. Three-dimensional freehand ultrasound (3DfUS) and instrumented spasticity assessment (ISA) are two recently developed techniques that enable the evaluation of changes in muscle, tendon, and neural properties following BoNT injections for post-stroke spastic equinovarus. These methods hold promise for providing new insights into treatment effects. Before implementing these techniques in large-scale studies, a pilot study is required for accurate sample size calculations for a prospective observational study. This study includes a protocol for a non-blinded, non-randomized open-label longitudinal pilot study. The study was approved by the European Medicines Agency ( EU CT Number 2024-513158-32) by the University Hospitals Leuven ethical committee (ID S68672). Standard deviations and effect sizes of outcome measures obtained longitudinally with 3DfUS and ISA before and after BoNT injection into MG will inform sample size calculations for future research.
Voluntary written informed consent of the participant or their legally authorized representative has been obtained prior to any screening procedures
2. At least 18 years of age at the time of signing the Informed Consent Form (ICF)
3. Use of highly effective methods of birth control; defined as those that, alone or in combination, result in low failure rate (i.e., less than 1% per year) when used consistently and correctly; such as implants, injectables, combined oral contraceptives, some IUDs, true sexual abstinence (i.e. refraining from heterosexual intercourse during the entire period of risk associated with the Trial treatment(s)) or commitment to a vasectomised partner.
4. Pes equinovarus due to spasticity
Musculoskeletal or other neurological problems affecting the lower limb
Presence of spinal cord pathology that could lead to spasticity, ataxia, dystonia
Cognitive problems that impede measurements
Severe co-morbidities
Single group
threedimensional freehand ultrasound and instrumented spasticity assessment
Diagnostic testTo conduct a pilot study as guidance for a future observational study to evaluate changes in muscle, tendon and neural properties after botulinum neurotoxin-A (BoNT) treatment of spastic equinovarus in first-ever stroke patients by using Three Dimensional freehand Ultrasound (3DfUS) and Instrumented Spasticity Assessment (ISA) with the aim of optimizing treatment algorithms and long-term response in this population.
sample size calculation
To estimate the number of subjects to calculate an appropriate sample size for assessing changes in muscle, tendon and neural properties after BoNT treatment of spastic equinovarus in first-ever stroke patients by using 3DfUS and ISA in a future observational study. To calculate standard deviation and effect sizes of outcome measures obtained with 3DfUS and ISA in these patients.
muscle changes
Secondary outcome parameters measured by 3DfUS include muscle belly length for medial gastrocnemius muscle
neural changes
Secondary outcome parameters measured by ISA for slow stretch measured by ISA : maximal velocity of performance (Vmax \[deg/s\])
functional changes
Medical baseline data including age, gender, body mass index, time since stroke, stroke etiology, National Institute Health Stroke Scale \[15\], affected side, oral medication and adverse events will be collected at each visit from the patients medical file as they are part of standard of care:
muscle changes
Secondary outcome parameters measured by 3DfUS include tendon length for medial gastrocnemius muscle
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