Hip dysplasia in children

The hip is built like a ball in a cup: the round head of the thigh bone sits in a socket in the pelvis and is held there by the depth of that socket, by the ligaments and by the capsule. Dysplasia means the cup has turned out too shallow and the head sits in it loosely. The extreme form is the head slipping over the rim — a dislocation. This used to be called congenital dislocation of the hip, but the name proved inaccurate: in some children the joint is normal at birth and drifts out over the first months. That is why the term now used is developmental dysplasia, which stresses that the process unfolds over time. Hence the central point of this page as well: the sooner the hip is picked up, the gentler the treatment.

What happens inside the joint

Socket and head grow towards each other and shape each other: the round head pressed into the cartilage cup deepens it, and a deep cup holds the head in place. If the head sits crookedly or half outside, the socket grows flat, and every month that passes locks the mismatch in further. The baby, meanwhile, feels nothing: dysplasia in an infant does not hurt, does not stop them moving and does not affect their mood. That is precisely why it is looked for by examination rather than waited for.

If the hip never settles into place, the bill arrives later: limping and a waddling gait in a pre-school child, groin and lower back pain in a teenager, a difference in leg length, early arthritis of the hip and spine in a young adult. A hip treated in time almost always goes on to develop like any other.

Who it happens to more often

Dysplasia is not uncommon and more often affects one hip, usually the left. Certain circumstances raise the likelihood:

• girls, in whom it is found several times more often than in boys;
• breech position in the last weeks of pregnancy — the baby lying feet or bottom down — and this counts regardless of how the birth itself ended;
• dysplasia in a parent, a brother or a sister;
• being the first child;
• low amniotic fluid and anything that crowded the baby in the womb, including a large baby or a multiple pregnancy;
• tight wrapping with the legs straight and pressed together during the first months;
• torticollis and foot deformities noticed at birth, which often travel in the same company.

One important caveat: more than half of children with dysplasia have none of these circumstances. The absence of risk factors is not a reason to skip looking at the hips.

How and when the hips are checked

A newborn's hips are examined in the first days of life, and the examination is repeated at the routine checks of the first six months. The timings differ slightly from country to country; the principle is the same — not one examination but several, because some cases do not show up straight away.

The examination itself is simple. The doctor undresses the baby, opens the bent legs out and compares whether they open equally, looks at the thigh creases and the leg length, and performs two manoeuvres in which the head of the thigh bone either slips out of the socket or slides back into it. It does not hurt, although few babies enjoy lying undressed.

If the examination leaves doubts, or if there is a history of breech position or a family history, an ultrasound scan of the hips is arranged, usually at around six weeks of age. Doing it earlier makes little sense: some hips mature on their own, and too early an image leads to unnecessary treatment. Ultrasound shows cartilage and therefore works in the smallest babies; from roughly six months, once the bony centre appears in the head, an X-ray becomes more informative. With twins, both babies are scanned even if only one lay bottom down.

A separate word about clicks. A brief painless click when the legs are opened also occurs in healthy babies and usually comes from the ligaments. What counts is not the noise but the sensation of the head slipping that the doctor finds with their hands, and the picture as a whole.

What should alert parents later on

The checks of the first six months catch most cases but not all: a hip can drift out afterwards. Parents should take the child to a doctor within days, not at some convenient moment, if they notice:

• one leg opens out to the side noticeably less than the other when you change a nappy;
• the legs look different in length, and with the child on their back and knees bent the knees end up at different heights;
• the creases on the thighs and under the buttocks are strikingly uneven;
• the child crawls dragging one leg;
• the first steps come with a limp or a rolling, side-to-side gait;
• the child walks on tiptoe on one foot only.

Uneven creases on their own also occur in healthy children and mean nothing without the other signs — but checking the hip is easier than guessing.

There is also something that calls not for an orthopaedic appointment but for urgent care. If a child has suddenly stopped putting weight on a leg, holds it in a fixed position and screams when it is moved, especially if a fever has come with it, that is not dysplasia. That is how joint infection and bone infection behave, and they destroy a hip within days. In that situation urgent care is needed the same day, not observation.

The Pavlik harness and other soft devices

A baby whose dysplasia is found in the first months is usually fitted with a Pavlik harness, a system of fabric straps that holds the legs bent and apart. Nothing is straightened and nothing is pulled: the point is for the head of the thigh bone to sit in the right position and, by its own pressure, to deepen the socket. The baby moves their legs freely and the joint is shaped by that movement.

What parents need to know:

• it is worn continuously, usually for weeks or months, and nobody but the doctor should take it off — removing it on your own initiative undoes the treatment;
• the nappy is changed as usual with the harness on, and goes underneath the straps;
• clothing should be loose and goes over the device; bodysuits and trousers a size up work well;
• the harness is not washed, but a soiled patch can be cleaned with an old toothbrush and soapy water and dried without taking it off;
• the baby should sleep on their back;
• a soft cotton pad goes under the straps wherever they rub, and the skin in the armpits, groin and behind the knees is checked every day.

Ring the doctor without waiting for the next appointment if: the skin under the straps is red or weeping, the baby has stopped moving a leg or pulling it up towards the tummy, the device has slipped and is clearly not sitting as it was fitted, or the baby has become unsettled for no other reason.

The doctor checks the position of the hip at each visit and adjusts the straps as the child grows. Towards the end of treatment it is usually allowed off for short periods, and then for good. After that the child needs to move freely; they will start walking in their own time and should not be hurried.

When surgery is needed

Surgery is discussed if the dysplasia was found late — after around six months of age — or if the harness has not worked. The basic operation is called a reduction: the head of the thigh bone is put back into the socket under general anaesthetic. There are two routes. A closed reduction is done without incisions: the joint is placed and held with a plaster cast. In an open reduction a cut is made in the groin, because shortened soft tissues are in the way, and the surgeon removes the obstruction under direct vision.

After the reduction a cast covering the pelvis and the legs is applied. It is worn for months, with cast changes under anaesthetic and check imaging. In older children, or where the deformity is marked, an operation on the bone is added — an osteotomy: the thigh bone or the pelvic bone is cut and rotated so that head and socket line up.

It is worth talking the surgery through unhurriedly: what exactly is planned, how long the cast stays on, how to wash the child, how to transport them in a car, when the checks are due. Follow-up runs for years, because the hip keeps growing and the doctor needs to see that it is growing correctly.

Swaddling, slings and anything that holds the legs together

In the first months a baby's hips are soft and easily moulded. If the legs are held straight and pressed together for long stretches during that time, the socket may form less well, and in a child whose hip is already unstable it makes matters worse. So:

• if you swaddle, leave the legs free: the fabric drapes loosely at the bottom and the baby can bend and draw up the knees;
• in a carrier or sling the hips should be spread and the knees higher than the bottom; narrow carriers in which the legs dangle together are worse for an infant;
• a car seat and a bouncer are safe, but a whole day in them is not: the baby needs time lying down and moving the legs freely;
• do not buy devices promising to «straighten the legs» without a doctor prescribing them.

Online consultation

An infant's hip is assessed by hand and by ultrasound, so the diagnosis is not made remotely. But an online appointment settles the questions on which parents usually lose time. The doctor will go through whether the child needs a scan and when it is best done, and will explain the report: the angle figures and the type letters frighten people more than they should. Online you can show how the child opens their legs and how they crawl, discuss uneven creases, ask about carriers and swaddling, and go through daily life in a harness — how to dress, how to wash, what to do about reddened skin. And settle the main thing: whether the routine appointment can be waited for or the child should be seen today. If the picture calls for an examination, you will be referred to an orthopaedic specialist in person, and that is the right outcome of the consultation.

This material is for information only and does not replace medical advice.