Treating Drop Foot
Definition of Drop Foot
Drop foot can be defined as a significant weakness of ankle and toe dorsiflexion.
The foot and ankle dorsiflexors include the tibialis anterior, extensor hallucis longus and extensor digitorum longus. These muscles help the body clear the foot during its swing phase and control plantar flexion of the foot on heel strike. This is referred to as a steppage gait, because the patient tends to walk with an exaggerated flexion of the hip and knee to prevent the toes from catching on the ground during the swing phase of the gait cycle.
This, in turn, will cause the foot to plantar flex, and potentially the foot will slap the ground. Two specific case studies have been chosen to highlight potential secondary consequences from a resultant primary trauma. It is important to note how the initial presentation is identical but the underlying factor is completely different.
Discussion of the case studies
Both of these athletes presented with exactly the same symptoms, i.e. they were unable to dorsiflex the ankle. When you have a situation like this, in which the main muscle involved in dorsiflexion (the tibialis anterior) is shown to be weak – or in more severe cases, unable to show a contraction within the muscle – then it is necessary to consider a problem with the nerve controlling the muscle. This nerve is called the deep peroneal nerve, which is a branch of the common peroneal nerve. Fibres from the dorsal branches of L4-S1 are found in the peroneal nerve, which is paired with the tibial nerve to constitute the sciatic nerve.
The sciatic nerve leaves the pelvic cavity at the greater sciatic foramen, just inferior to the piriformis muscle. The sciatic nerve splits to form the peroneal and tibial nerves near the distal thigh. The peroneal nerve crosses laterally over the fibular neck to the anterior compartment of the lower leg, dividing into superficial and deep branches. The superficial supplies the peronei and then branches to the ankle anterolaterally to supply sensation to the dorsum (or top) of the foot. The deep branch divides just after rounding the fibular neck.