Neurologic changes caused by cerebral palsy (CP) result in adaptation of muscle architecture and function (e.g. shortened muscles and contractures). Stretching through immobilization (orthotic treatment) is one of the common interventions to bring the spastic muscle to growth. Positive outcomes of stretching through immobilization are increased range of motion and improved function. On the other hand, immobilization leads to disuse muscle atrophy. Hence, we hypothesize that combining a stretching through immobilization and muscle activity while controlling for foot deformity could be a superior treatment approach, which should lead to improved muscle morphology as well as function. The aim of the study is to examine the influence of two orthotic treatments (a standard regime and one new approach) on spastic plantar flexor muscles in children and adolescents with CP. The standard regime (stretching through immobilisation) includes a dynamic AFO (ankle-foot orthosis) used during day and night. The new approach combines stretching through immobilisation and allows for plantarflexor activity due to an innovative construction of the orthotic device.

This prospective randomized controlled study will recruit 20 ambulant children and adolescents (aged 5 to 15 years) with cerebral palsy and equinus deformity (GMFCS = Gross Motor Function Classification System level I to III). Each child will be randomized and stratified according to age and GMFCS to one of two groups. The first group receives the standard treatment (stretching through immobilization) using custom-made ankle foot orthosis for 23 hours per day. The other group will be treated with the same orthosis at night (8 hours) and for 6 hours during the day but the remaining 10 hours will be treated with the foot shell only that corrects subtalar and Chopart joints but does not block the ankle joint movement, so that more activity of plantarflexors will be possible during the day. The intervention will last for 12 weeks. Each child will be examined at four occasions (8 weeks before intervention = control phase, at the beginning of the intervention and then 8 and 12 weeks later). The main outcome measure is the fascicle length measured using a 3D ultrasound (3DUS) imaging technique. Further parameters of interest span across the whole levels of ICF including clinical examinations, biomechanics of gait, muscle morphologic and mechanic properties and participations questionnaires.

Inclusion Criteria:

• Ambulatory children with spastic CP.
• Ability to accept and follow verbal instruction.
• Limited range of motion in ankle joint - maximal dorsiflexion with knee extended ≤ 5°
• Gross Motor Functional Classification System level I-III.
• Age 5-15 years.
• Willingness to participate.

Exclusion Criteria:

• Other than spastic form of CP (ataxic, athetoid or dystonic).
• Severe mental retardation.
• Normal range of motion in ankle joint
• Oral antispastic or muscle relaxing medication.
• History of orthopaedic surgery in the last 12 months.
• History of botulinum toxin type A application in the last six months.

It is yet not decided if individual data will be shared with other researchers.