Q: What is DDH?
A: In DDH, the ball and socket of the hip joint do not fit snugly together, making the joint less stable and the ball may slide in and out of the socket. This is called a subluxatable hip if the ball can pop back in. If the ball loses contact with the socket and stays outside the joint, it is called a dislocated hip.
Q: How common is hip dysplasia?
A: DDH requiring treatment affects 1-3 babies per 1000 births. That's up to a 1 in 30 chance of your child having this condition.
Q: What are the risk factors?
A: The most common risk factors are:
- breech position (at any time during pregnancy or at birth) and
- family history of DDH or hip problems in early life.
Other risk factors include:
- multiple pregnancy (twins, triplets or more)
- oligohydramnios (low levels of amniotic fluid during pregnancy)
- torticollis (baby born with a crooked or wry neck) and
- foot abnormalities (including positional talipes, where the foot is turned down and in but is flexible, metatarsus adductus, where the front of the foot is hooked or turned in, and calcaneovalgus, where the foot is turned upwards and outwards)
Q: When should I suspect it?
A: In addition to the above risk factors, you should suspect it clinically if:
- When changing a nappy, one leg/thigh does not seem to move outwards or open as fully as the other or both legs seem restricted
- Deep unequal creases may be present in the buttocks or thighs
- One leg appears shorter than the other (bend both knees up and compare their heights - one will be lying lower than the other)
- When moving one or both hip joints e.g. when changing nappies, you may feel a click and/or a clunk
- There are additional clinical tests such as Ortolani's and Barlow's - these tests are best performed by an experienced paediatric orthopaedic surgeon
- In older children, one leg may be shorter than the other and your child walks with a limp, tiptoes on the shorter leg or bends the knee on the longer leg. If both hips are dislocated, your child may walk with a waddling limp.
Q: How is it diagnosed?
A: If any of the above applies to your child, then this may well have been picked up at the newborn and 6-8 week baby check. If not, then go and see your GP who will refer on for an ultrasound scan of the hip (if less than 4 months of age) or an X-ray (if more than 4 months of age). At the Royal London Hospital, we run a one-stop baby hip clinic every Wednesday afternoon where clinical assessment, imaging and treatment all happen at the same time.
Q: How is it treated?
A: When picked up at less than 4 months of age on an ultrasound scan, treatment is with a special soft hip harness (Pavlik harness) that holds the hip joint in the correct position for 4-6 weeks. Tis has a success rate of more than 90%. If picked up later or if the harness treatment fails, the hip joint has to be relocated gently (closed reduction) under general anaesthesia and held in position for 3 months in a special plaster cast called a hip spica (including a change of spica cast at 6 weeks under anaesthetic). My preference is not to have a bar between the legs in the spica cast. Occasionally, tight tendons in the groin may have to be released to maintain a hip joint relocation (tenotomies).
In older children, further treatments may need to be added at the time of surgery, such as opening the hip joint to relocate the ball accurately into the socket (open reduction), cutting the pelvic bone in order to restore the socket shape (pelvic osteotomy) and/or cutting and reshaping the femur bone to repoint the ball in the right direction (femoral osteotomy). My preference is to avoid leaving any metalwork behind is possible in order to prevent the need for further surgery for metalwork removal. My preferred pelvic osteotomy is the Dega which can be done without fixation with pins or wires. The success rates are very high and I have published on the technique and results previously here.
Q: If it needs an operation, what happens before, during and after?
A: Most children do not need any special preparation for surgery. Anaesthetic assessment is performed on the day of admission (including weight and general health check). If any blood tests are needed, then they are performed when your child goes to sleep in order to reduce distress. For closed reductions, your child is admitted as a day case and can go home the same day once you are comfortable looking after her in her new cast and she has recovered fully from the anaesthetic. For open reductions +/- osteotomies, she will spend 1-2 nights in the hospital but one of you can stay with her in the hospital.
Pain is well controlled by the anaesthetist who will give an injection into your child's back (spinal) to make the hip joint area numb. In addition, the lack of hip joint movement in the spica cast minimises the level of pain.
Q: What complications should I be most concerned about?
A: The three most common complications are:
- redislocation (where the ball pops out of the socket - this most commonly happens within the first 10 days, is diagnosed on X-ray and is treated by removing the spica cast and waiting till your child is older to attempt a further relocation)
- avascular necrosis (this is loss of the blood supply to the hip joint and is rare - if mild to moderate, it often improves spontaneously - if severe, which is very rare, your child may need further surgery)
- need for further surgery (this may either be needed because of loss of position and/or failure to achieve a full relocation at the initial operation, or because the hip joint fails to develop fully, necessitating further surgery when your child is older)
Q: What will the hip spica plaster cast be like?
A: Most commonly, your child will be in a spica similar to the one in the image above (but most likely white in colour!). The legs will usually be bent at the knee in what is known as the 'frog' position. I rarely use a bar between the legs. There is excellent information on spica casts on the STEPS Charity website but we will provide you with all the information you need, most commonly via our Specialist Physiotherapists and Occupational Therapists.