Normal Variants In Orthopedics

The essentials

– Most minor orthopedic problems in children are self-correcting.

– Bowing of the legs is normal in toddlers.

– Flat feet are not normally a cause of foot pain.

– Pes cavus is not a disease but a physical sign and suggests pathology.

– Toe walking is a normal part of many children’s development.

IN-TOEING AND ITS CAUSES

Children often develop minor orthopedic abnormalities that are, in effect, variations of normal development. Parents bring their children to see their GP with such problems and, although most are self-correcting, they are often a source of great parental concern. When GPs can make a confident diagnosis, unnecessary referrals with their associated increase in anxiety can be avoided.

In practice, few pediatric orthopedic problems require surgical intervention, but it is necessary to be aware of the normal parameters in order to understand where a particular development has diverged from the norm (see box, right).

In-toeing is one of the commonest reasons for referral to pediatric orthopedic clinics. If a child is in-toeing, it means the lower limb must be twisted. There are three possible reasons for this twisting, and they occur at different sites and in different age groups.

Metatarsus adducts

Metatarsus adducts

Metatarsus adducts is a twist in the forefoot occurring in the first few months of life.

The medial border of the forefoot is curved inwards, and this is thought to be caused by over-activity in the abductor halluces muscle. The only management necessary is to advise against prone nursing and to watch and wait.

The vast majority of cases spontaneously resolve. In persistent cases, splinting may help. Surgery may be needed if the problem is still evident after the child reaches the age of five.

There can be an association with other problems such as developmental dysplasia of the hips, so always re-examine if presented with a case of metatarsus adducts.

Internal tibial torsion

A twist in the tibia is tibial torsion and tends to be seen in toddlers aged between one and three years. As with metatarsus adducts, most cases spontaneously resolve, so reassurance and observation are the only measures required at first.

Attempts at accelerating resolution with various unsightly splints have a dubious reputation and are probably not worthwhile. In only a tiny proportion of children is a derotational osteotomy required.

tibial torsion

Internal femoral torsion

A twist in the femoral neck is usually seen in children aged three to 10 years and is caused by an abnormal angle of femoral neck anteversion.

In an adult, the typical angle of anteversion of the femoral neck is 15 deg.

However, a baby is born with an angle of 40 deg. For this reason, there must be a gradual transition of the angle towards the adult position.

If the angle is slow to change and persists into childhood, the presentation is usually a child with an abnormal gait and symmetrical in-toeing.

A child with an increased angle of anteversion of the femoral neck will have a reduced or absent angle of external rotation to the hip.

The complete absence of external rotation is a bad prognostic sign, but as the natural history is one of spontaneous resolution, a wait-and-see approach should be adopted. Only a small minority require rotational osteotomy in their teens.

Other children self-compensate by developing an external rotation of the tibia so that the feet point forward normally. This results in the patella pointing inwards – the so-called squinting patella syndrome.

This is cosmetically unattractive, but as bilateral femoral and tibial osteotomies would be required to correct it, it is probably best left alone.

KEY POINTS

– In-toeing is one of the commonest reasons for referral to pediatric orthopedic clinics.

– If a child is in-toeing, it means the lower limb must be twisted.

– There are three possible reasons for this twisting and they occur at different sites and in different age groups.

– Surgical intervention is rarely required.

DEVELOPMENTAL MILESTONES

Nine months sit without support.

12 months walk with one hand support.

14 months walk alone.*

Climb stairs two years.

Run two years.

Stand on one leg four years.

Hop five years.

*It is normal to be walking alone by the age of 14 months but there is no need to be concerned up to the age of 18 months.

BOWLEGS AND KNOCK-KNEES

Knock-knees

Babies are born with bowing of the legs – the knee joint is in varus.

In the course of development the knee gradually straightens, and by the age of three to eight years, the child’s knee will have adopted a valgus angle. The adult angle is in the region of 7 deg of valgus.

The bowing of early childhood is symmetrical and improves steadily. Splints will make no difference to the progress of the condition.

Pathological bow legs

Pathological bowing may be asymmetrical, deteriorates with time and tends to be more severe than physiological bowing. Possible causes are Blount’s disease (disordered growth of the proximal tibial epiphyses), rickets, skeletal dysplasias, and trauma.

Bowing with short stature suggests skeletal dysplasia. Weight-bearing anterior-posterior X-rays can help exclude pathology.

Knock-knees

In knock-knees – or genu valgum – the legs are in valgus. Beyond the age of about three years, valgus knees are normal, but an increased or asymmetric angle may be pathological.

While most cases tend to resolve with growth, severe and asymmetric cases may not. A previous fracture affecting the growth plate may lead to genu valgum, and so will skeletal dysplasias and rickets. If treatment for genu valgum eventually proves essential, splinting is probably a waste of time for both doctor and patient.

Surgery can be performed in severe cases, and is usually aim at causing the partial arrest of the growth plate. The aim is to create compensatory asymmetrical growth to bring the limb into alignment again. However, this procedure is often unpopular with patients and their families, especially as it may take some time for the correction to occur.

A troublesome residual angle at the end of the pubertal growth spurt may require an osteotomy.

KEY POINTS

– Babies are born with bowing of the legs with the knee joint in varus.

– The knee will have adopted a valgus angle by the age of three to eight.

– Weight-bearing anterior-posterior X-rays can help exclude pathology.

– A previous fracture affecting the growth plate may lead to genu valgum.

– Treatment for genu valgum is rarely necessary, and the use of splints is ineffective.

PHYSIOLOGICAL AND PATHOLOGICAL FLAT FEET

flat feet

A child presenting with a foot problem is more likely to be there at the request of the parents than because the child is experiencing troublesome symptoms.

The normal situation is that when the sitting child is examined from behind, the heels are in slight valgus. When he or she stands, the heels go into varus, and when standing on tiptoe, the longitudinal arch of the foot becomes exaggerated.

Physiological flat feet

Flat feet are normal in young children. The arches develop gradually with growth and do not normally appear until about six years of age. Children who have generalized ligamentous laxity are more likely to experience a delay in the appearance of a normal arch. Some specialists would claim that flat feet can be physiological up to the age of 10 years.

Two simple tests can be reassuring for parents and the doctor. The tip-toe test consists of asking the child to stand on tip-toe; the long flexor tendons become tense and the arches appear. The jack test involves lifting the big toe off the ground; this produces the arch in a mobile foot.

There is no evidence that flat feet cause foot pain. Studies on Canadian military recruits suggested that there was no less foot pain in soldiers with normal arches than those with flat feet.

Various special footwear has been tried. Just about anything is likely to be seen to work because physiological flat feet are self-correcting.

The need for surgery is limited to a few troublesome cases and never arises before the age of 12. Insoles with arch support can increase the life of a pair of shoes.

Pathological flat feet

Flat feet may have a pathological cause. A tarsal coalition is where two or three of the tarsal bones have fused into one. There are various causes, many of which are idiopathic, but septic arthritis, osteoid osteoma, juvenile chronic arthritis and traumatic subtalar degenerative changes may be responsible. The condition usually presents at age 10 to 11 and is a common cause of painful flat feet.

The pain is worse after activity, and the foot is immobile. There is often a family history of the problem. Incidence has been estimated at 1 percent of the population, although many cases are asymptomatic. If the pain is significant, surgery may be needed to release the connecting bar of tissue.

Paralytic flat feet are associated with several neurological conditions including cerebral palsy and spina bifida.

Flat feet can also be associated with ligamentous laxity. Painful or peroneal spasmodic flat foot is another possibility. A tight Achilles tendon may be responsible, and may require lengthening.

KEY POINTS

– A child with a foot problem may present because of parental concern rather than because the child has symptoms.

– The tip-toe and jack tests are simple and can be reassuring.

– Although flat feet are mostly idiopathic, there are pathological cases.

– A tarsal coalition is a common cause of painful flat feet in children.

PES CAVUS

pes cavus

Pes cavus is a high arched foot, and is not a disease, but a physical sign. Unlike flat feet, pes cavus must be considered pathological until proven otherwise.

With pes cavus, the longitudinal arch of the foot is elevated and there is often associated clawing of the toes. The metatarsal heads are more prominent than normal and in persistent pes cavus there may be callosities.

The priority for the doctor is always to establish the underlying cause of the condition. The best treatment can then be planned, and the prognosis determined.

Two types of pes cavus

There are two types of pes cavus. With pure cavus feet, there is no varus or valgus deformity to the hind foot. In parvovirus foot, the deformity is associated with a varus hindfoot.

This may give a clue to the etiology. Idiopathic pes cavus is usually a pure pes cavus, but neurological pes cavus is usually parvovirus.

Causes of pes cavus

A thorough neurological examination should be carried out in all cases.

In particular, inspect the base of the spine for a hairy patch that may signify spina bifida occult.

Neuromuscular causes include Duchenne muscular dystrophy, peripheral nerve involvement such as peroneal muscular atrophy, and spinal cord problems such as spinal dysraphism and polio. Central causes include cerebral palsy and Friedreich’s ataxia. Pes cavus may also result from a poorly corrected clubfoot.

The age of the patient

The age of the patient may also help identify the cause. Childhood pes cavus is usually neuromuscular. Sometimes the child’s shoes have worn out in an unusual fashion. Callosities may appear over the metatarsal heads and if the pathology is neuropathic, there may be ulcers on the heads of the metatarsals. Adolescent pes cavus is usually idiopathic.

There is often a family history, and it is associated with claw toes, tender callosities and pain at the metatarsal heads.

KEY POINTS

– With pes cavus, the longitudinal arch of the foot is elevated.

– Clawing of the toes, prominent metatarsal heads, and callosities often appear with it.

– Duchenne muscular dystrophy must be excluded as a cause.

– The age of the patient may give a clue to the etiology of the condition.

– There is often a family history.

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Article by John J. Christian

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