Impact of a Sequential Isokinetic Fatigue Protocol Followed by Ankle Strengthening After Botulinum Toxin Injection Into Spastic Plantar Flexors on Foot Lift Strength and Walking

Spastic foot drop (speed- and force-dependent hypertonia) is one of the most common neuro-orthopaedic disorders following brain injury. It has a negative impact on walking and is closely linked to independence in activities of daily living.

This disorder combines a deficit in muscle strength in the plantar flexors and extensors with pathological hypertonia of the plantar flexors, causing an imbalance in ankle flexion and resulting in equinus deformity of the foot.

Botulinum toxin is the first-line pharmacological treatment for focal spasticity of neurological origin, and its effectiveness is directly linked to the quality and quantity of associated rehabilitation care. However, the associated rehabilitation protocols remain vague and are based on general recommendations combining: stretching of muscles and tendons, muscle strengthening of spastic muscles, their agonists and antagonists, and functional work. The standard rehabilitation protocol used in our centre will be detailed in the study protocol.

The isokinetic dynamometer is an open-chain muscle strengthening tool that has the advantage of introducing a concept of reproducible assessment and rehabilitation.

This reproducibility is difficult to guarantee with the rehabilitation techniques practised by a therapist, whose applied force and precision may vary from one session to another. We have therefore developed a sequential muscle strengthening protocol combining strengthening work - fatigue of the triceps surae followed by muscle strengthening work of the foot lifters.

The aim of this work is to determine the effects of this protocol compared to conventional rehabilitation aimed at promoting the post-injection effects of botulinum toxin.