Restraining Children - Best Practice

When a vehicle is involved in a crash it comes to an abrupt halt. The people inside continue to move in the direction of travel until something stops them. If a person is not restrained they will have their own crash into the vehicle structure or an object outside the vehicle, if they are ejected. This may result in serious injury or death. Restraint systems are designed to help keep people away from the vehicle structure and to distribute the forces of a crash over the strongest parts of the body, with minimum damage to the soft tissues.

Adults are restrained by a three point seat belt. These are designed to work for adults and this makes them unsuitable for use by children. Children cannot achieve the correct placement and fit of the adult belt over their shoulders and pelvis. A dedicated child restraint system must be used to accommodate the needs of a child at different stages of their development. Children are not small adults. They are proportioned differently and their key organs are in different places. Their tissues have different strengths and weaknesses and their needs change as they grow.

Infants

 At birth, the infant head is around a quarter of their total length and about a third of their body weight. The skull bones are separated by membrane-filled spaces, which take many months to close; some spaces are closed within 2 or 3 months of birth but the largest of the spaces is not closed until 18 to 24 months after birth. This means that the infant's skull is very flexible, so relatively low levels of crash loading can result in significant deformation of the skull and brain. In fact the smaller the child, the lower the energy needed for injury. The ligaments in the infant spinal column are relatively loose and the overall structure is fairly elastic allowing it to stretch up to 5 cm. However the spinal cord can rupture when stretched more than 0.6 cm, so spinal cord injury can occur without vertebral damage.

The infant rib cage is also very flexible. Impact to the chest can result in large compression of the chest wall onto the heart and lungs, so belt loading to the chest is not appropriate for infants. The rib cage is not well developed and cannot protect some of the abdominal organs. The infant pelvis is unstable and cannot withstand the forces from a restraint system. To provide the best care for an infant we must try and achieve the following: motion of the head relative to the torso must be avoided; restraint forces must be distributed as widely as possible over the strongest parts of the body, which in the case of infants is the back. A rear facing child restraint system is therefore the only solution that we recommend for protecting infants. Infant carriers (group 0+ seats) accommodate babies up to 13kg. If a baby EITHER exceeds this weight limit OR grows too tall for the height of the harness, only then should they be moved to the next stage of child restraint. If the baby is less than 13kg it can and should remain rear facing. This will be possible by moving up to a "two way" seat. These seats are designed so they begin rear facing and can then be turned round to be forward facing (Group 1) as the child gets older. The benefit of these is that there is no need to turn the child round until they reach the mass limit of 13kg, so they could rear face until they are 18 months.

Childhood

 After the fluid filled spaces in the skull have closed, the thickness and composition of the skull is still different to an adult's. The bone making process is not complete until the age of 6 or 7 and throughout childhood the stiffness of the child's skull remains less than that of an adult. A restraint system must limit forward head movement in a front impact and provide protection from intrusion in a side impact. The muscles and ligaments in the spine strengthen and the bones grow and reach a mature shape and size, but the risk of neck injury in car accidents remains. The risk of spinal cord damage due to loading from the head has reduced, so if a child is unusually heavy for their age (greater than 13kg) they can face forwards from the age of 1 year. The chest and rib cage become larger. The ribs remain flexible, but calcified bone gradually replaces soft bone and their strength increases. As the rib cage develops downwards it provides some protection of the liver, spleen and kidneys. The pelvis grows larger, but development of the parts of the bones needed to act as an anchor point for belt restraint systems is not complete until around the age of 10 years.

Therefore to provide the best care for childhood a restraint should distribute the crash forces over as wide an area as possible and there should be proper placement and good fit of the harness or belts. The restraint system should also provide protection from contact with the vehicle interior in both front and side impact.

We believe the best type of child restraint system for early childhood is the child safety seat. A five point harness secures the child and spreads the crash forces over a wide area. This seat will last them until they are about 5 years old. However, we recommend they should stay in this type of seat for as long as possible and only move to the next seat when EITHER their weight exceeds 18kg OR they grow too tall for the height of the adjustable harness or the head protection. Booster seats are best used only when a child has outgrown a safety seat. These seats raise the seating position of the child so that the adult seat belt lies properly across the chest and pelvis. The booster seat has a back and side wings to help protect the child's head in side and rear impact. It is necessary to check the instructions on these seats, very carefully, before purchasing. There are seats available where the back stays in place and the head wings adjust to accommodate children up to and including the age of 11 years. These are the only booster solutions that we recommend for best practice.