Peroneal spring

A peroneal spring is a splint (orthosis) that ensures that the foot does not hang down. People who, due to a nerve or muscle disorder, can no longer lift the foot properly benefit from such a splint. The peroneal spring is also called an ankle-foot orthosis.

What does a peroneal spring do?

A peroneal spring supports the foot while walking. It is a splint made of lightweight plastic. This runs at the back of the lower leg and under the sole of the foot. The peroneal spring is fastened to the lower leg and the foot with velcro fastener. Because the splint goes into the shoe, it is important that there is enough space in the shoe. Usually, removing the insole is sufficient.

The splint ensures that the foot remains at a 90-degree angle relative to the lower leg. But the peroneal spring is also a bit flexible. As a result, it supports the foot on the one hand when lifting. On the other hand, the foot is able to move a little downwards, which makes walking and cycling easier.

Who is a peroneal spring suitable for?

The peroneal spring is intended for people in whom the dorsiflexors do not work (properly). The dorsiflexors are the muscles in the lower leg and foot that ensure that the foot and toes can be pulled up towards the lower leg. The most important dorsiflexor is the tibialis anterior muscle.

Without action of these dorsiflexors, the foot and the toes hang down. This is annoying when walking. If the foot cannot be lifted, the whole leg has to be lifted higher to avoid tripping. This is called a steppage gait. With every step, the foot then "slaps" on the ground, because the muscle strength to put it down gently is lacking. This is called a foot drop.

If it is not possible to lift the whole leg high enough, the toes drag over the ground. The risk of falling is greater as a result. When a foot constantly hangs down, an equinus (toe-walking) deformity can develop in the long term.

Causes of failure of the dorsiflexors

There are different causes whereby the dorsiflexors no longer work properly:

• Nerve problem. The muscles that have to lift the foot are controlled by nerves. When there is a problem with the nerve, the muscles do not receive the signal to lift the foot properly. Examples of this are an entrapment of a nerve, such as in a hernia, an injury to the peroneal nerve in the lower leg, a nerve disease such as MS, or brain injury.
• Muscle disease. There are different muscle diseases that cause muscle weakness or muscle failure. As a result, the dorsiflexors are not strong enough to lift the foot.
• Injury to muscles or tendons. Due to a muscle or tendon tear of the tibialis anterior muscle, the foot misses its most important dorsiflexor. The other muscles are not strong enough to lift the foot.

Not the solution to the problem

A peroneal spring provides support and protection for the foot. But wearing a splint does not, of course, solve the underlying problem. Therefore, it is important also to tackle the cause. For example, in the case of a trapped nerve, it has to be freed by a surgeon. If there is a muscle or tendon tear, then the physiotherapist is the person to help restore the strength and function of the dorsiflexors.