Developmental Dysplasia of the Hip

Question 1

Definition of the spectrum of dysplasia in childhood

Answer 1

Any hip that has partial or complete loss of contact between femoral head and acetabulum
—could be dislocated or dislocatable
—could be subluxated or subluxable (partial dislocation)
—could be stable but a morphologically abnormal hip

Question 2

What are some mechanical causes of DDH?

Answer 2

Things related to intrauterine crowding:

1. Positioning— Breech
2. Oligohydramnios— mother has low uterine fluid
3. L>R — the left thigh normally rests against the mothers sacrum which pushes it (adducted) towards the midline, which is not favorable for hip development

Question 3

What is the ligamentous laxity cause of DDH?

Answer 3

At the end of pregnancy, mothers make relaxing hormones (relaxins) that allow their ligaments to get loose so the pelvis can expand for birth. Relaxins are transmitted transplacentally, so there can be transient laxity of the hips d/t this

Question 4

What is DDHs association with packaging disorders?

Answer 4

Packaging disorder birth defects are when things are pushed wrong d/t uterine crowding. Often seen are:

Foot Deformities
—Metatarsus adductus- the foot is hooked inwards
—Calcaneovalgus foot- hyper dorsiflexed and turned outward

Hyperextended knees

Torticollis wry neck- tilted to one side and twisted to the other

SOOOOO when you see these things you already KNNOOOWWWW there’s a crowding problem and you know you need to follow up with the hips

Question 5

Is there a genetic link to DDH?

Answer 5

Yes:::::::
—If mom has hip dysplasia each child has a 6% chance of also having dysplasia

—If mom AND a sibling has dysplasia the chance goes up to 33% for the child

Question 6

What are ethnic/racial differences in DDH?

Answer 6

More common in native Americans > whites > blacks

Question 7

Why is being a first born a risk for DDH?

Answer 7

The uterus is tighter. After the first baby there’s more room in the uterus

Question 8

What is the incidence of instability vs established dislocation vs dysplasia?

Answer 8

Instability = 1 per 100-250

Established dislocation = 1-2 per 1000

Dysplasia = 4 per 10,000

Question 9

What’s the fate of an unstable hip?

Answer 9

It can become normal on its own or it can settle into a partially subluxated position where it wont shape correctly, will stay dislocated, or can relocated but parts can be underdeveloped (dysplastic)

Question 10

Barlow test

Answer 10

one of the provocative tests of instability
—Take abducted hip and bring towards midline with knee and hip flexed; then gently push back to try to provoke a dislocation
—does not hurt baby but you will feel the clunk of dislocation
—This is for a hip that IS located and you want to see if its dislocatable

Question 11

The Ortolani Test

Answer 11

one of the provocative tests of instability
—looking at a DISLOCATED hip to see if its relocatable
—Take knee and hip that are in flexed positions and bring it away from midline while you are gently lifting up on the greater trochanter to coax it to pop back into the cup
—the clunk of reduction

Question 12

Galeazzi sign

Answer 12

Pushing up on the hips and knees in the flexed position
—If one hips is dislocated it will be sitting out the back and makes the knees not at the same level and one leg looks shorter
—there whether its able to be reduced or not

Question 13

Asymmetry of abduction

Answer 13

Flex knees and abduct legs out in frog leg position. If One of the sides will not come out as far its (+) asymmetric abduction
— Often times all you find in an older baby who’s signs of instability have disappeared and they have a fixed dislocation
—often seen in walking age kid

Question 14

What are the late physical exam findings?

Answer 14

—Leg length discrepancy
—Trendelenburg gait limp; “abductor lurch” tilted over to the affected side to make up for weakness of abductor muscles because they are at mechanical disadvantage
—Increased lumbar lordosis

Developmental milestones will be normal! Just because they walk on time doesnt mean they dont have dislocated hips- it doesnt hurt children

Question 15

What imaging do you get for DDH?

Answer 15

1. US
   —good for 0-4 months old
   —Visualize cartilaginous structures prior to ossification
   —assess morphology, relationships, stability
   —Useful for guiding treatment for ortho
   —BUT has high rate of false +/-
2. Radiographs
   —after 4 months you can start to see more on x rays
   — this is more standardized and accessible and useful for long term trending of the hip

Question 16

Why is DDH early diagnosis so important?

Answer 16

1. You are more likely to be able to treat it with closed means as opposed to sx
2. Re establishing the relationship means that the body can start shaping and remodeling it to normal
3. The longer its dislocated the more misshapen it can get

**if hip dysplasia is not caught in childhood it can lead to an abnormally shaped hip in adulthood which can end in Perthes arthritis or LLD

Question 17

Pavlik Harness

Answer 17

Mainstay treatment for the first 6 months of life
—overalls with stirrups attached to keep legs flexed about 90 degrees
—directs the ball into the center of the cup and stimulates it to get deeper
if you haven’t reduced in 3-4 weeks you need to discontinue

• *can be used up to 9 months of age
• *about 90% effective
• *Preferred for low rate of complications

Question 18

Closed reduction

Answer 18

DDH that has gone on for a while or that has failed a Pavlik harness
—Some hips can’t be reduced in the office because of their muscle tone, so if you put them to sleep you can often reduce it and put them in a spic cast in the same position
—Hopefully after 3-4 months in cast you can take it off and it will continue to grow normally

Question 19

Open Reduction

Answer 19

Surgical opening of the hip to clear any obstacles to reduction and help the body reshape

Question 20

Obstacles to hip reduction

Answer 20

—Psoas muscle constricting
—Capsule
—Ligament hypertrophy
—Pulvinar tissue
—Cartilage edge infolding

May have to do open reduction and clear these things

Question 21

What is Pavlik harness disease?

Answer 21

Complication of pavlik harness use:
—Femoral nerve kinked and caused femoral nerve palsy
—will generally improve well when taken out of flexion

If you haven’t been able to reduce the acetabulum in 3-4 weeks you need to discontinue

Question 22

What are complications of treatment

Answer 22

Pavlik harness disease

AVN

Redislocation— usually technical error

Residual Dysplasia— body doesnt have enough biological reserve to normalize the shape of the hip

Question 23

Do the epiphyseal arteries cross the growth plate?

Answer 23

No