Evaluation of Percutaneous Cryoneurotomy Compared to Surgical Open Neurotomy for the Management of Equinovarus Foot Deformity in Patients With Refractory Lower Limb Spasticity After Stroke

Stroke, arising from cerebral vascular hemorrhage or ischemia, represents a major health-care problem affecting more than 140,000 persons in France every year. One of the major concerns after stroke is impairment of the pyramidal tract and parapyramidal fibers, resulting in upper motor neuron syndrome and spasticity. Up to 20% to 40% of stroke survivors develop spasticity, which dramatically impacts health status, pain, functional capacity, and ultimately, quality of life. Spastic equinovarus foot (SEF) is the most common deformity due to lower limb spasticity and is defined as a combination of an abnormal plantar-flexion, inversion and adduction of the foot. Consequently, SEF severely impairs walking capability and mobility, impacting daily life activities and restricting social participation. In addition to therapeutical physical rehabilitation programs, two main treatments can be proposed. First, SEF can be initially treated with focal botulinum toxin injections that for reducing spasticity. However, botulinum toxin injections are effective for only a limited period of time, and iterative reinjections are required. Second, permanent treatment of spasticity can be achieved by surgical neurotomy. This procedure, variably combined with muscle and tendon lengthening in the event of associated retractions, can be considered as the long-term radical and effective gold standard, but at the price of surgical invasiveness and complications.

A recent alternative allowing for both permanent treatment and a minimally invasive approach has been introduced: "percutaneous cryoneurotomy". While this approach has provided promising results, as shown in multiple case reports, its efficacy has yet to be determined in a randomized control study.

CryoNeurotomy (CN) was first performed and developed in daily practice for the upper limb. Through a mentoring process, a feasibility study was performed on cadavers and transposed the technique to human procedures in a pilot study. The results from the first patients, with a 90-day follow-up period, are promising, with decreased spasticity and significantly increased walking capabilities. Major potential advantages of percutaneous CN compared to surgical neurotomy were identified, such as minimal skin incision, faster procedure, far less invasiveness of muscle tissue and adjacent neuro-vascular structures, particularly a decreased risk of post-operative sensory loss or neuropathic pain, no need for general anesthesia (local anesthesia) and possible performance on an outpatient basis. By enlarging Physical Medicine and Rehabilitation (PMR) therapeutical armamentarium, percutaneous CN could represent a new compromise between botulinum toxin iterative injections and radical surgery, in terms of invasiveness & complications/long-term benefit ratio on spasticity and function.

The CRYOSTROKE study was designed:

• to compare the efficacy and safety of percutaneous CN versus surgical neurotomy on spasticity, 90 days after intervention, in post-stroke patients presenting with spastic equinovarus foot and,
• to ensure that potential clinical effect/safety remain stable within time, with a 12-month follow-up.

Inclusion criteria

• Age ≥18 years old.
• Patient with spastic equinovarus foot as a result of stroke in chronic phase (>6 months).
• Patient with positive perineural motor block test with or without complete correction of spastic equinus and non-persistence of 40° equinus.
• Patient eligible for surgical neurotomy for varus equinus foot.
• Patient presenting no cognitive impairment or major depression (Mini Mental State Examination>20, Hospital Anxiety and Depression (HAD<11)).
• Absence of active psychosis or history of serious psychotic illness requiring hospitalization
• Patient understanding and accepting the constraints of the study.
• Patient covered by French national health insurance.
• Patient who has given their written consent to the study after having received clear information.

Exclusion criteria

• Patient with previous nerve procedures such as chemical neurolysis with alcohol, cryoneurotomy, or any surgery at the same anatomical site.
• Patient with any neurological pathology different from the one responsible for the spasticity.
• Patient with botulinum toxin in lower limb injection during the last 90 days before intervention.
• Patient with anti-spastic treatment (baclofene) up 3 days before block test.
• Patient with total deficit of valgus muscles.
• Patient with equinus foot > 40° (retractions/ankylosis).
• Surgical and anesthetic contra-indications (severe uncontrolled coagulation disorder, active infection).
• Cryoneurotomy contra-indications (cold intolerance, cryoglobulinemia, cryofibrinogenemia, Raynaud's phenomena, venous thromboemolism (< 3 months if superficial, < 6 months if deep), hypothyreosis, cold urticari, local disorders of blood supply, considerable anemia, cachexia, hypothermia, cancer disease, infection, coagulopathy…).).
• Subject requiring closer protection, i.e. minors, pregnant women, nursing mothers, subjects deprived of their freedom by a court or administrative decision, subjects admitted to a health or social welfare establishment, major subjects under legal protection (temporary or permanent guardianship and, subject to subordination), and finally patients in an emergency setting.
• Pregnant woman, nursing mother, woman of childbearing potential not using effective contraception (hormonal/barrier: oral, parenteral, percutaneous, implantable, intrauterine device, or surgical: tubal ligation, hysterectomy, total ovariectomy).