Makindo Medical Notes.com

Babies whose legs are swaddled tightly with the hips and knees straight are at a notably higher risk for developing DDH after birth. Early detection and treatment are critical for improving paediatric quality of life. Delayed diagnosis and treatment at a later stage entail extensive surgery, which comes with greater difficulties and a worsened functional outcome

About

• 1 or 2 in every 1,000 babies have DDH that needs treating.

Aetiology

• The hip is a "ball-and-socket" joint.
• Hip joint has not formed normally
• Ball is loose in the socket and may be easy to dislocate.
• Developmental dysplasia (dislocation) of the hip (DDH)

Risks

• Girls, First-born children
• Breech delivery: ultrasound DDH screening of all female breech babies.
• Family history of DDH (parents or siblings)
• Oligohydramnios (low levels of amniotic fluid)

Classification

• Dislocated. Most severe. The Head of the femur is completely out of the socket.
• Dislocatable. The head of the femur within the acetabulum, can easily be pushed out of the socket during a physical examination.
• Subluxatable. Mild cases of DDH. The Head of the femur is simply loose in the socket. During a physical examination, the bone can be moved within the socket, but it will not dislocate.

Tests for hip instability or dislocation in the newborn infant: (A) Ortolani's test; (B) Barlow's provocative test

The following are clinical signs which can be used in diagnosing DDH under 3 months.

• Asymmetrical skin folds. Normal inguinal folds stop before the anal aperture. Abnormal skin folds extend posteriorly and laterally beyond the anal aperture. Other asymmetrical skin folds to note are gluteal and on the thighs. Excessive looseness of hip and knee flexion is a probable sign of DDH.
• Klisic line: Drawn from tip of the greater trochanter to the ASIS, then continued superiorly and medially towards the umbilicus. In a normally developed hip joint, this line will bisect the umbilicus, but in an abnormal developed hip, the line passes below the umbilicus.
• Ortolani and Barlow tests positive. If Ortolani and Barlow tests are positive, ultrasonography is recommended. Ultrasound is the modality of choice in children under the age of 6 months as it is during this time the femoral head is predominantly cartilaginous and therefore cannot be picked up on X-ray. Once there is a significant ossification has occurred (over 6 months of age) then an x-ray examination can be performed.

Clinical

• Screening hip exam at birth and 6-8 weeks
• Seen from birth to 1st year of life with legs of different length
• Uneven skin folds, Less Immobile or flexibility on one side
• Limping, toe walking, or a waddling, duck-like gait

Screening Ultrasound Criteria

• Hip feels unstable
• Family history of childhood hip problems
• Breech birth
• Twins or multiple birth
• Born prematurely before the 37th week of pregnancy

Investigations

• X-rays and other regular follow-up monitoring are needed after DDH treatment until the child's growth is complete. Because the head of the femur and acetabulum are predominantly composed of cartilage, standard radiographs have poor diagnostic value in neonates. Several classic lines on the X-ray of the immature pelvis guide the process of assessing DDH. Hilgenreiner's line is a line joining both of the triradiate cartilages. The Perkins line extends along the lateral border of the acetabulum and is at right angles to the Hilgenreiner's line in a normal hip. The Shenton’s line contains a curvature that starts at the lesser trochanter, extends upwards towards the neck of the femur, and connects to a line along the inner margin of the pubis. In a normal hip, Shenton's line is smooth. This line is non-continuous when the affected hip is subluxated or dislocated. The angle formed at the intersection of Hilgenreiner’s line and the line drawn along the surface of the acetabulum is called the acetabular index. As the baby grows, this angle changes as well. It measures how much the roof of the acetabulum is inclined. This is the most frequently employed parameter in assessing the morphological features of the acetabulum. In normal newborns, this angle is 27.50 degrees, 23.50 degrees at six months, and progresses to 20 degrees at second birthday. Generally, 30 degrees is considered as normal upper limit and a notable increase in this value is considered a sign of AD
• USS: Ultrasonography is the investigation of choice for DDH in the first six months of life. It is more beneficial to evaluate subtle sub-types of the disorder when the clinical examination is inconclusive. Moreover, this is the only imaging mode that provides real-time 3D images of the hip joints of newborns.

Complications

• Damaged hip joint with pain and osteoarthritis by early adulthood.
• Difference in leg length or a "duck-like" gait and decreased agility.

Management

• The earlier it is diagnosed the easier it is to treat. Learn to swaddle properly can be helpful to prevent it. If detected at birth then consider Pavlik harness for 1-2 months or brace. This keeps the femur in the socket and helps strengthen ligaments. Normal care can continue.
• Diagnosis 1-6 months: Use harness or brace as above for 6 weeks then intermittent for 6 weeks. Sometimes the hip can be reduced gently into proper position, and then a body cast (spica cast) placed to hold the bones in place. This procedure is done while the baby is under anaesthesia.
• Diagnosis: 6 months to 2 years. Treat with closed reduction and spica casting. Skin traction may be used before repositioning which prepares the soft tissues around the hip for the change in bone positioning. If a closed reduction procedure is not successful then open surgery is necessary. In this procedure, an incision is made at the baby's hip that allows the surgeon to clearly see the bones and soft tissues and then reduced and a spica cast is usually applied to maintain the hip in the socket.
• Even after proper treatment, a shallow hip socket may still persist, and surgery may be necessary in early childhood to restore the normal anatomy of the hip joint.

References

• DDH review