DDH (Developmental Dysplasia of the Hip)

Question 1

What is developmental dysplasia of the hip (DDH)?

Answer 1

Disorder of abnormal development resulting in dysplasia and possible subluxation or dislocation of the hip secondary to capsular laxity and mechanical factors
Is a spectrum of disease:
Dysplasia- a shallow or underdeveloped acetabulum
Subluxation
Dislocation
Teratologic hip- dislocated in utero and irreducible on neonatal exam presents with a pseudoacetabulum
Late (adolescent) dysplasia- mechanically stable and reduced but dysplastic

Question 2

What are the risk factors for DDH?

Answer 2

1) first born
2) female (6:1 over males)
3) breech
4) family history
5) oligohydramnios

Female left hip is MC location

Question 3

Where is the acetabular deficiency typically in DDH?

Answer 3

Anterior or anterolateral

Is cerebral palsy it is posterosuperior

Question 4

What are the 3 physical diagnostic tests of DDH?

Answer 4

Barlow- a dislocatable hip will dislocate with adduction and posterior force
Ortolani- a reducible hip will reduce with abduction and traction
Galeazzi- knees bent, dislocated leg appears shorter

Barlow and Ortolani a rarely positive after 3 months of age because of soft-tissue contractures about the hip

Question 5

What is the most sensitive sign of DDH in a child >3 months?

Answer 5

Limitation of hip abduction

Children who are of walking age may have Trendelenburg gait

Question 6

What are some radiographic lines a/w a hip dislocation in DDH?

Answer 6

1) Hilgenreiner’s line- horizontal line through right and left triradiate cartilage; femoral head ossification should be inferior to this line
2) Perkin’s line- line perpendicular line to Hilgenreiner’s through a point at lateral margin of acetabulum; femoral head ossification should be medial to this line
3) Shenton’s line- arc along inferior border of femoral neck and superior margin of obturator foramen
arc line should be continuous

Question 7

Development of what after a hip reduction of DDH after reduction is thought to be good prognostic sign for hip function?

Answer 7

Acetabular teardrop

Question 8

What are radiographic signs in dysplasia of DDH?

Answer 8

1) Acetabular index- line drawn from point on the lateral triradiate cartilage to point on lateral margin of acetabulum and Hilgenreiners line; should be less than 25° in patients older than 6 months
2) Center Edge Angle (CEA)- angle formed by a vertical line from the center of the femoral head and a line from the center of the femoral head to the lateral edge of the acetabulum; less than 20° is considered abnormal
(reliable only in patients over the age of 5 years)

Question 9

What imaging modality is used to follow reduction with use of a Pavlik harness for DDH?

Answer 9

Ultrasound

US not used for screening exam unless at 4-6 wks have positive exam or risk factors

Question 10

What is the study of choice to view reduction following closed reduction and spica casting of DDH?

Answer 10

CT

Question 11

What age groups are various treatment modalities initiated for the treatment of DDH?

Answer 11

1) 18 months- open reduction and spica casting (or if closed reduction fails)
4) > 2yrs- open reduction and pelvic osteotomy (more common in kids >4yo)

Question 12

What is the goal position in Pavlik harness application in DDH?

Answer 12

90-100° hip flexion, 50° abduction
worn for 23 hours/day for at least 6 weeks or until hip is stable; wean out of harness over 6-8 weeks after hip has stabilized until normal anatomy develops
Follow initially every week with US; if not reduced by 3 weeks then closed v open reduction and spica cast

Question 13

What are some technical points of hip spica casting for DDH?

Answer 13

1) 100° hip flexion
2) 45° hip abduction (may require adductor tenotomy)
3) use arthrogram to confirm reduction intra-op
4) CT post-op to confirm reduction
5) casted for 3 months; change at 6 wks

Question 14

What are the pelvic osteotomies for DDH?

Answer 14

All used to increase anterior or anterolateral coverage of femoral head
Salter- Single cut above acetabulum through the ilium to sciatic notch (Tr open, younger kids)
Triple (Steele)- Salter with additional cuts through rami (Tr open, older kids)
Pemberton- starts below AIIS and ends at Tr (Tr open, moderate to severe DDH, most versatile)
PAO (Ganz)- multiple osteotomies in the pubis, ilium, and ischium near the acetabulum (Tr closed; posterior column intact)

Question 15

What are the salvage pelvic osteotomies for DDH?

Answer 15

Shelf- Add bone to lateral acetabulum (relies on fibrocartialge metaplasia)
Chiari- cut above acetabulum to sciatic notch and shift ileum lateral beyond edge of acetabulum (relies on fibrocartilge metaplasia)

Question 16

What are complications seen in the treatment of DDH?

Answer 16

Osteonecrosis- increased rates with forceful abduction, failed closed tx, repeat surgery
Transient femoral nerve palsy- seen with excessive flexion with Pavlik bracing

Question 17

The acetabular teardrop is composed of what structures?

Answer 17

Quadrilateral surface and cotyloid fossa

Question 18

When does the ossific nucleus of the proximal femur become visible on radiographs?

Answer 18

At 6 months of age

Question 19

What are impediments to reduction of the DDH?

Answer 19

1) constriction of the joint capsule of hip: most important type of obstruction in older children;
2) contraction of the psoas tendon over acetabular inlet;
3) hypertrophy of the transverse acetabular ligament;
4) pulvinar
5) ligamentum teres;
6) inverted neolimbus
7) Labrum

Question 20

Using the posterior lower extremity straps of a Pavlik harness to produce abduction is a/w?

Answer 20

AVN; posterio straps are used to prevent adduction; anterior straps are used for hip flexion