Excerpt from Toe Walking

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Toe walking has multiple etiologies ranging from idiosyncratic habit to profound neuromuscular disease. The spectrum of management options extends from mere observation to operations that may involve the lengthening of multiple tendons in the same lower extremity. In dealing with this entity, the underlying pathophysiology for each case must be understood to ensure that the treatment is appropriate to the specific etiology.

History of the Procedure

Tenotomies are among the oldest procedures in orthopedics. It would be impossible to date the first lengthening of a heel cord. The multilevel percutaneous lengthening was described by Delpech in 1823 in France.

Problem

Toe walking may be a sign of a serious condition, such as profound neuromuscular disease.

Frequency

The most common cause of toe walking is cerebral palsy, which affects 1-7 per 1000 children, but toe walking occurs in fewer than 50% of these patients. Reports vary greatly regarding the incidence of the various types of cerebral palsy. (Also, see the eMedicine article Cerebral Palsy.) 

A second cause is paralytic muscle disease, most typically represented by Duchenne muscular dystrophy, which has an incidence of 1 per 3500 live male births. All children with Duchenne muscular dystrophy walk on their toes.

Finally, toe walking may be idiopathic. No studies report the incidence of this condition. The author saw 8 patients with idiopathic toe walking out of 1160 new patient visits in his pediatric orthopedic specialty practice, but this population is significantly filtered through the referral process.

Etiology

At the benign end of the spectrum is the condition called idiopathic toe walking. This entity has also been termed habitual toe walking and congenital short Achilles tendon. The diagnosis is made by excluding all neuromuscular pathologies. Idiopathic toe walking first appears in a toddler as walking begins. Many children start out on their toes. Some give up this apparent habit pattern; others do not. Those who persist merit attention.

A more common cause of toe walking is muscle spasticity. Spasticity of the muscles of the lower extremity may have multiple causes. The common denominator is a lesion within the pyramidal tract of the central nervous system. The most common cause of this is spastic cerebral palsy, in which the lesion is a deficit in the motor cortex, resulting from either a failure of development or, more rarely, from a birth injury. Less commonly in children, the insult to the motor cortex may occur after birth as a result of a cerebral vascular accident. Lower extremity spasticity may also result from damage to the fiber tracts from the motor cortex within the spinal cord. Spinal cord lesions may be congenital, traumatic, or otherwise acquired. It is important to determine the underlying etiology of muscle spasticity as precisely as possible and to understand how this alters the dynamics of gait before proceeding with treatment. (Also, see the eMedicine article Spasticity.)

The last of the 3 etiologies is paralytic muscle disease, a loss of muscle caused by loss of anterior horn cells or by a destructive process of the muscle. The classic example is Duchenne muscular dystrophy. This progressive loss of muscle tissue is associated with fibrosis. Because the plantar flexor muscles at the ankle are about 6 times more powerful than are the dorsiflexors, this fibrosis leads to a fixed contracture in plantarflexion (ie, equinus). Less common paralytic muscle diseases that may lead to toe walking include some of the other types of muscular dystrophies and some of the congenital myopathies. Again, as with spasticity, an understanding of the dynamics of gait is critical before proceeding with treatment.

Pathophysiology

Idiopathic toe walking results from a congenital shortness of the tendon or from a habit pattern of toe walking that leads to a fixed contracture of the Achilles tendon. Young patients who display idiopathic toe walking invariably have symmetrical involvement. The extent to which their ankles are plantarflexed in gait typically is more than any tendon contracture would require. Many patients can stand flat if prompted to do so, and with an occasional patient, the examiner can demonstrate a normal range of passive dorsiflexion. Regardless of the initial status of the heel cord, the contracture progresses with time. A long-standing equinus contracture can then lead to a valgus deformity of the hindfoot, another undesirable consequence.

Two mechanisms for toe walking may result from lower extremity muscle spasticity. The first is a spastic contracture of the heel cord. Muscles that are more spastic have been shown to grow less than do muscles that are less spastic. If the gastrocnemius and the soleus are excessively spastic, a fixed equinus results. This consequence is seen most typically in spastic hemiplegia, the form of cerebral palsy that involves 1 side of the body and in which the foot and ankle usually are more involved than is the proximal limb musculature.

Lower extremity spasticity may also involve the proximal joints in addition to the foot and ankle. Spastic diplegia is a form of cerebral palsy that involves both lower extremities and spares, to a relative extent, the upper extremities. Typically, there is a uniform involvement of hip, knee, and ankle in spastic diplegia. Spasticity of the hip flexors and the knee flexors causes an abnormality of gait in which the hip and knee are constantly flexed and the patient bears weight upon the toes and forefoot. This abnormality has been called a jumper's gait. The toe walking may be associated with spasticity of the ankle plantar flexors, but it is in part secondary to the flexion of the hip and knee. If hip and knee are flexed in stance and the ankle is held at a right angle (ie, plantigrade), the patient bears weight on the toes and forefoot, even though the ankle itself is not in equinus.

Understanding the dynamics of the gait abnormality is important in treating toe walking associated with muscle spasticity. Is the toe walking caused by spasticity of the ankle plantar flexors alone, or must the surgeon also deal with spasticity at the knee and hip?

Toe walking in paralytic muscle disease is caused by the replacement of muscle by fibrous tissue as the muscle deteriorates. All muscles are involved, but plantar flexors remain stronger than do dorsiflexors, favoring the development of equinus. Patients with paralytic muscle disease also walk on their toes to compensate for weakness of the knee extensors. In Duchenne muscular dystrophy, as a classic example, the weakness in the limb is greater proximally than distally. The quadriceps becomes weak, which threatens knee stability. The ankle plantar flexors remain relatively strong. By walking on the forefoot, the patient generates an extension moment at the knee that helps to stabilize the knee. To help understand this phenomenon, stand on the toes of 1 lower extremity. The knee is felt being pushed into extension. Once again, the dynamics of the patient's gait must be understood before treatment is instituted.

Clinical

The patient with idiopathic toe walking presents as a toddler as walking begins. The child otherwise appears completely normal and begins to walk at a normal age (anytime up to age 18 mo). The deep tendon reflexes are normal. No pathologic reflexes are present. Often, the patient can walk flatfooted if prompted. There may be a variable degree of tightness of the plantar flexors of the ankle that restricts passive dorsiflexion. Inspection and palpation of the thoracolumbar spine reveals normal findings. The child walks and runs on the toes, particularly when he or she is unaware of being observed. Balance and coordination are otherwise appropriate to the patient's age. Toe walking invariably is symmetrical in involvement. Asymmetry eliminates the diagnosis of idiopathic toe walking.

The presentation of toe walking in a patient with muscle spasticity depends on the underlying cause and time of onset of the spasticity. If the condition is congenital, as it will be in the case of cerebral palsy, developmental milestones, including the onset of walking, can be expected to be significantly delayed. Muscle spasticity is apparent at the time of the initial evaluation and has an anatomic distribution that reflects the extent of the lesion of the motor cortex. The deep-tendon reflexes are hyperactive. While muscle contractures can worsen with time, it is important with cerebral palsy to understand that the underlying neurological lesion is static and nonprogressive. A patient with cerebral palsy may have associated cognitive defects, but those are separate from the diagnosis of cerebral palsy, which is by definition a disorder of the motor system alone.

Patients with other causes of spasticity may present later in life with acquired toe walking. The history may adequately document an etiology, such as a stroke or spinal cord injury, that occurred abruptly. However, the onset may instead have been gradual, as might be seen with a spinal cord tumor or diastematomyelia (in which the presentation may be unilateral). A thorough examination to include the spine is required. The underlying cause may be far more significant to the patient's well-being than is the effect of the toe walking itself.

In addition to determining the underlying cause of the muscle spasticity, the examiner must fully evaluate the dynamics of gait (that is, how the spasticity is causing the toe walking). Muscle function must be evaluated at all joints in the lower extremity.

A patient with toe walking secondary to a paralytic muscle disease presents later, usually after the primary diagnosis has been well established. The clinical picture varies, depending on the primary diagnosis. Specific to the toe walking, the examiner must evaluate the strength of all of the muscles of the lower extremities to determine the degree to which the equinus may be compensating for weakness of knee extension. The patient's overall prognosis must be considered in the decision-making process, but if there is doubt with a paralytic muscle disease, the physician always should err on the side of optimism.

Physical examination

The most valuable diagnostic procedure is the physical examination. For a patient with suspected idiopathic toe walking, the examination should be directed to rule out all other possible causes. For a patient with muscle spasticity, determine the anatomic distribution of the spasticity. To what extent is the toe walking secondary to contracture of the Achilles tendon and to what extent is it secondary to spasticity of the hamstring muscles and the hip flexor muscles causing a jumper's gait? For a patient with paralytic muscle disease, preoperatively determine the contribution of the equinus to knee stability.

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