Inclusion of patients very limited due to lack of time and human resources dedicated to research.

Lack of current consensus on the therapeutic management of low-grade osteo-ligament injuries in ankle trauma in children. Several types of immobilization are evaluated in the literature, with different conclusions. Some teams recommend a functional treatment similar to the adult (with or without strict immobilization), others remain on standard rigid immobilizations.

The goal of the study is to simplify and homogenize the therapeutic management of low-grade osteo-ligament injuries in ankle trauma in children.

Lack of current consensus on the therapeutic management of low-grade osteo-ligament injuries in ankle trauma in children. Several types of immobilization are evaluated in the literature, with different conclusions. Some teams recommend a functional treatment similar to the adult (with or without strict immobilization), others remain on standard rigid immobilizations.

The goal of the study is to simplify and homogenize the therapeutic management of low-grade osteo-ligament injuries in ankle trauma in children.

CHEVIPED is a controlled, randomized, comparative monocentric trial.

Randomization into 2 groups and stratified on presence to fracture Salter 1 and age

Experimental group : Patients with below-knee soft resin cast Control group : Patients with below-knee rigid resin cast.

The primary objective is to demonstrate at 2 months that with post traumatic low- grade osteo-ligamentous ankle injury the recovery of physical function are at least as effective with a below-knee soft resin cast compared to a below-knee rigid resin cast.

The secondary objectives are :

1. Clinical evaluation of treatment at 3 weeks in immediate post-immobilization.
2. Evaluation of the management satisfaction (effectiveness and understanding) and the treatment tolerance .
3. Evaluation of the time taken to resume painless support after immobilization.
4. Point of interest evaluation
5. Determine the diagnostic performance of the "combined clinical criteria" in comparison with the ultrasound/radiography couple.
6. Evaluation of the diagnostic performance of clinical inspection criteria (edema, bruise) in high-grade ligament damage.
7. Evaluation of the link between the "combined clinical criteria" and the results of the radiography.
8. Evaluation of the relationship between "combined clinical criteria" and ultrasound results.
9. Evaluation of the link between the results of radiography and ultrasound.

200 patients are expected to be included.

Inclusion period : 12 months. Duration of patient's participation: 2 months Total study duration: 14 months.

Inclusion Criteria:

• Walking child from 5 to 15 years old.
• From hour 0 to hour 48 of ankle trauma with torsion mechanism (inversion, eversion or rotation).
• Patient presenting for the first time to the emergency room for this traumatic episode.
• Possibility of carrying out an ultrasound during the passage to the emergency room.
• Child and parents' consent in the study participation

Exclusion Criteria:

• Pubescent patients requiring anticoagulation (menarche in girls and genital pilosity in boys).
• Direct shock on the foot without sprain mechanism.
• Fracture with deformation or open fracture.
• History of ankle trauma in the last 3 months.
• Neurological or neuromuscular pathology.
• Child with a delay in acquisitions and / or psychomotor development (difficulties in understanding and interacting to locate pain).
• Absence of a representative of parental authority.
• Constitutional bone disease or connective tissue.
• Acquired or congenital coagulopathy.
• Patient presenting beyond 48h of trauma.
• Polytraumatized.
• Dermabrasion, wound or sign of skin suffering next to the ankle requiring specific monitoring.
• Child or parents refusal in study participation

All collected data that underlie results in a publication

Data will be available after the publication of result and ending fifteen years following the last visit of the last patient

Data access requests will be reviewed by the internal committee of Brest University Hospital. Requestors will be required to sign and complete a data access agreement.