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Normal childhood variations in lower limb development

Orthopaedic surgeon Mr George Bennet

offers advice on reassuring parents

C hildren are fascinating

in that they are constantly

changing. Normality varies

with age. This change, and

inevitable comparisons with

other children, gives scope for

parental concern.

Everyone wants perfect children. Even those who have them want them checked out occasionally.

Problems arise when a child deviates from someone's idea of normal. They then expect treatment.

Walking

There is a wide variation in the age of walking but most start at about one year. Five per cent of otherwise normal children will not be walking at the age of 18 months. On starting to walk the arms are held abducted, they have a broad based gait and often walk on tiptoe.

By the age of three, an adult pattern is generally established and this matures up until the age of seven.

Flat feet

A seemingly disproportionate amount of parental attention is paid to a child's feet. It focuses on the longitudinal arch.

There is no definition as to what constitutes a flat foot. The most obvious deformities are a valgus heel and a sagging mid-foot. Where normality ends, however, is another matter. As a consequence, the prevalence is difficult to judge. Suffice to say that flat feet are usual in infants, common in children and within normal range in adults.

Children with such feet tend to have generalised ligamentous laxity. Check for this and demonstrate it to the parents. Have the child stand on tiptoe. The arch will generally appear.

That being the case, explain that they have flexible feet – a good thing – as opposed to flat. They should leave feeling pleased. Stiffness anywhere in the foot merits investigation.

There is no doubt that children with apparent flat feet are still grossly overtreated. Many parents are ensnared by shoe adverts that promise excellent development of the foot if a certain sort of shoe is worn.

It is sometimes hard to convince parents that no treatment is best. It is worth pointing out a few salient facts. Flat (or flexible) feet are normal in infants. As the child gets older the arch appears. Flexible flat feet do not cause trouble, either in childhood or later life.

There are no trials showing that prophylactic surgical or non-surgical treatment prevents long-term pain or disability. What research there is shows that heelcups and corrective shoes do not alter the natural history of the condition.

Very occasionally flat foot produces aching. In that case, insoles may provide symptomatic relief, although they will do nothing for the shape of the foot.

Shoes

Remember footwear is not vital. The growing foot does not need support. A study in India1 showed a higher prevalence of flat feet in shod as opposed to unshod children and in adults who started wearing shoes at a young age. Where shoes are not worn arches still develop. Mobility and flexibility are inversely related to the wearing of shoes2.

Parents often fit shoes in the first year of life. This is a clothing not medical issue. There are many opinions as to what constitutes a good shoe. These are not based on fact. There is little evidence that expensive good shoes are better for a child's foot than a cheap pair of trainers. Parents may feel guilty if they do not invest in expensive shoes even if they can ill-afford them. Save them some money!

Angular deformities

Angular deformities of the lower limb are part of normal development. The tibio-femoral angle was measured radiographically in almost 1,000 children by Salenius and Vankka3. To summarise their findings: bow legs are normal up to the age of two. At that age the legs are just about straight. Later children become knock-kneed, a stage that lasts until the age of seven when adult values are obtained. Beware if the deformity is asymmetric or falls outwith normal values or age groups.

The deformities can be monitored by measuring the distance between the knees, in the case of bow-legs, or between the ankles in knock-knees. This can be done either with a tape or, more simply, by seeing how many fingers can be inserted between the knees or ankles. Show the parents how to do this so they can monitor improvement. As an example: between the ages of two-and-a-half and three, more than 50 per cent of children have an intermalleolar distance between 2.5 and 5cm and 22 per cent have more than 5cm.

Such angular deformities need no treatment. Previously children used to be put into splints or, if rather better off, advised to take up horseriding. As the legs did straighten the beneficial effects were attributed to the treatment rather than the natural resolution and the doctor prescribing it enhanced his reputation – oh happy days!

Torsion

This means a twist in either the tibia or the femur. It is of little import but assumes greater significance than it deserves as it is so common and the effect it produces, intoeing, causes parental concern. The range of normal is wide.

Tibial torsion is commonest in toddlers. It is probably produced by the internally rotated position the lower limbs adopt in utero. Most untwist but some children may prevent this happening by sleeping or sitting with their feet tucked under them. Femoral torsion may be familial or may too be positional.

Clinical examination is the basis of management. It allows the localisation and quantification of the condition. Parents normally complain that the child intoes. Have the child walk. The angle the feet make with the line of progression is the foot progression angle, negative for in and positive for out. The mean is around +10 degrees.

Lie the child prone. Bend the knees to 90 degrees. Check the feet are normally shaped. Look at the angle the foot makes with the thigh – the thigh foot angle. This reflects the degree of tibial torsion. The mean again is +10 degrees. Next rotate the hips. This measures femoral torsion.

If lateral rotation

is less than 20

degrees then abnormal internal femoral torsion is said to be present.

Should anything be done? Tibial torsion gradually reduces up to the age of eight, after that there is little change. The vast majority resolve spontaneously. Treatment does not alter the natural history. Femoral torsion too tends to resolve by the same age. The only effective treatment is femoral derotation osteotomy and this is very rarely required.

Athletes tend to intoe more than non-athletes. Tell them. Make them feel good.

Growing pains

This is a vague condition of unknown aetiology that produces nocturnal leg pains. It affects 13 per cent of boys and 18 per cent of girls, usually in the four-eight age group. The pain is usually felt around the thighs, calves and knees. It is typically bilateral (serious complaints tend to be unilateral).

Once the whole family is asleep the pain comes on. The child starts screaming. After a few minutes' parental leg rubbing the child goes back to sleep. The parents may take longer. The natural concern is that there is a serious underlying problem.

Yet these children never limp, they are fine during the day and the pain never gets worse. Examination is normal.

Treatment has little to offer and spontaneous resolution is invariable.

George Bennet is consultant orthopaedic surgeon at the Royal Hospital for Sick Children, Glasgow

References

1.Sachithanandam V and Joseph B( 1995). The Influence of Footwear on the Prevelance of Flatfoot. J Bone Joint Surg 77A, 254-257

2.Sim Fook L and Hodgson AR (1958). A Comparison of Shoe and Non-Shoewearing Chinese Populations. J Bone Joint Surg 40A, 1058-1062

3.Salenius and Vankka (1975). The Development of the Tibio- Femoral Angle. J Bone Joint Surg 57A, 259-261

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