Radial Extracorporeal Shock Wave Therapy as an Adjunct to Botulinum Toxin Type A for Post-Stroke Lower Limb Spasticity (SOLUTION)

The SOLUTION study is a pilot, randomized, sham-controlled clinical trial designed to investigate the potential benefit of radial extracorporeal shock wave therapy (rESWT) as an adjunctive treatment to botulinum toxin type A (BoNT-A) for the management of post-stroke lower-limb spasticity.

Post-stroke spasticity is a common complication that may contribute to restricted joint mobility, abnormal limb positioning, impaired gait, pain, and limitations in functional activities. Botulinum toxin type A is an established treatment for focal spasticity. However, its therapeutic effect is temporary, and the duration of clinical benefit may be limited. Radial extracorporeal shock wave therapy is a non-invasive physical intervention that has been investigated as an adjunctive treatment for spasticity. The SOLUTION study was designed to investigate whether adding rESWT to BoNT-A could enhance the reduction in muscle spasticity and prolong the therapeutic effect of BoNT-A.

The study was conducted at the Neurorehabilitation Unit of the Physical Medicine and Rehabilitation Service of Hospital del Mar-Centre Esperança, Barcelona, Spain. The study protocol was evaluated and approved by the Clinical Research Ethics Committee of Parc de Salut Mar under project number 2022/10664/I. The protocol version evaluated by the committee was version 3, dated December 2, 2022, and the committee approval was documented in the meeting held on January 24, 2023.

Participants referred to the spasticity clinic were assessed for eligibility and, if eligible and willing to participate, were randomly allocated in a 1:1 ratio to one of two parallel treatment groups. Both groups received ultrasound-guided intramuscular botulinum toxin type A treatment. The intervention group additionally received active radial extracorporeal shock wave therapy, whereas the control group received a sham rESWT procedure.

Randomization was performed using a computer-generated random sequence. Allocation concealment was maintained by withholding the randomization codes until the predefined study measurements had been completed. Physicians from the Neurorehabilitation Unit were responsible for participant recruitment. The randomization sequence was generated by a physician blinded to participant identification. BoNT-A was administered by a physician using ultrasound guidance, while rESWT was administered by an experienced physiotherapist.

The study used a blinded assessment approach. Investigators involved in recruitment and data analysis were blinded to treatment allocation. The physiotherapist administering rESWT did not participate in follow-up visits or outcome data collection and was responsible only for recording adverse effects related to the rESWT procedure. In the sham group, participants received an initial stimulation intended to reproduce the sensory experience of treatment, followed by a progressive reduction in intensity to zero. Treatment allocation was disclosed after completion of the statistical analysis.

The botulinum toxin preparation used in the study was abobotulinumtoxinA (Dysport®). BoNT-A was administered according to the European consensus recommendations for the use of botulinum toxin type A in adult spasticity, with ultrasound used to guide the intramuscular injections.

Radial extracorporeal shock wave therapy was initiated approximately 24 hours after BoNT-A injection. Treatment was applied to the spastic triceps surae muscle group. Each active treatment session consisted of 3,000 pulses, with 1,500 pulses applied to the gastrocnemius muscle and 1,500 pulses to the soleus muscle, at a frequency of 5 Hz and an intensity of 2.5 bar. Three rESWT sessions were administered, at a frequency of one session per week for three consecutive weeks.

The sham rESWT procedure followed the same treatment schedule. Participants received an initial stimulation designed to provide a perceptible treatment experience, followed by a reduction in intensity to zero. This procedure was used as the sham comparator for the active rESWT intervention.

Both treatment groups received a session of instruction in stretching exercises targeting the injected muscle group. Participants were provided with a diary to record adherence to the prescribed exercises during the initial follow-up period.

Clinical assessments were performed at baseline, immediately before administration of BoNT-A and rESWT, and at 5 weeks, 3 months, and 6 months after BoNT-A injection. Outcome data were collected by an investigator blinded to treatment allocation.

The primary efficacy assessment evaluated changes in lower-limb spasticity using the Modified Ashworth Scale. Additional clinical assessments were used to characterize changes in muscle spasticity, passive ankle mobility, gait performance, muscle contracture characteristics, patient-perceived clinical improvement, pain, and treatment-related adverse effects.

The study was designed as a superiority trial comparing BoNT-A combined with active rESWT with BoNT-A combined with sham rESWT. The main hypothesis was that adjunctive rESWT would improve the effect of BoNT-A on lower-limb spasticity and increase the duration of the therapeutic response.

The planned sample size was 20 participants, with 10 participants allocated to each treatment group. The sample size calculation was based on the detection of a between-group difference of at least 1 point on the Modified Ashworth Scale, assuming a common standard deviation of 0.7, a two-sided alpha level of 0.05, 90% statistical power, and an anticipated 20% loss to follow-up. Given the pilot nature of the study and the small sample size, the findings were intended to provide preliminary estimates of treatment effects and information regarding the feasibility and safety of the combined intervention.

Safety was assessed throughout the treatment period. Adverse effects associated with rESWT were recorded using a predefined checklist including pain, local discomfort, worsening of pain between sessions, petechiae, muscular ecchymosis, and focal oedema. The use of orthoses during walking was also recorded.

The study was conducted at Hospital del Mar-Centre Esperança in Barcelona, Spain, during the period from January 2023 to January 2025.

The study was designed to determine whether the addition of rESWT to BoNT-A could provide an additional and sustained reduction in lower-limb spasticity compared with BoNT-A combined with sham rESWT. The results are intended to provide preliminary evidence to inform the design of future randomized clinical trials evaluating adjunctive rESWT in the management of post-stroke lower-limb spasticity.