Developmental hip dysplasia

Question 1

what is developmental dysplasia of the hip?

Answer 1

• A disorder of abnormal development resulting in dysplasia and possible subluxation or dislocation of the hip secondary to capsular laxity and mechanical factors

Question 2

What does DDH encompass?

Answer 2

• A spectrum of disease that includes
• DYSPLASIA
• SUBLUXATION
• DISLOCATION
• TERATOLOGIC HIP- identified in utero- has pseudoacrtabulum, assoc with arthrogryposis, myelomeningocele
• LATE ADOLESCENT

Question 3

What is the incidence?

Answer 3

• Hip dysplasia 25%
• scotland 4 per 1000 live births
• bilateral in 20%
• most common left hip in females

Question 4

What are the risk factors?

Answer 4

• First born
• female 6:1 males
• breech
• oligohydraminos
• FHx
• assoc with other packaging deformities
  
  • congential muscular torticolis 20%
  • Metatarsus adductus 10%
  • congenital knee dislocation

Question 5

What is the pathology meant to be caused by?

Answer 5

• INITAL instability thought to be due to maternal and fetal laxity
• Genetic laxity
• Intrauterine and postnatal malpositioning
• initial laxity-> dysplasia -> gradual dislocation

Question 6

Where is the normal acetabular deficiency ?

Answer 6

• Anterior or anterolateral
• In cerebral palsy= posteriosuperior

Question 7

What is the classification?

Answer 7

• Put into a spectrum of diseases
  
  • DISLOCATED
    
    • Ortani positive- reduce hip
  • DISLOCATABLE
    
    • Barlow positive
  • SUBLUXABLE
    
    • Barlow positive

Question 8

How do you diagnose it?

Answer 8

Physical exam <3 months

• ORTOLANI- hip is OUT AND TRY AND REDUCE IT- abduction manoeuvre
• BARLOW- hip is IN and try push back to dislocate it
• GALEAZZI- to identify any LLD due to unilate dislocated hip with hip and knees flexed
  
  • 90 degrees femur short on dislocated hip

Question 9

In a child older than 3 months what would your clinical findings be in a child with DDH?

Answer 9

• Limited HIP ABDUCTION
  
  • most sensitive test when contractures start
• LLD Unequal skin folds- only in unilateral
• >1 yr when walking
  
  • pelvic obliquity
  • lumbar lordosis
  • trendlenberg gait- abductor insufficiency
  • toe walking - compensate for shortening of affected side

Question 10

What age can you use radiographs? why?

Answer 10

• From 4-6 months
• as this is when the FEMORAL HEAD begins to OSSIFY
• Tear drop seen at 18 months
  
  • ​this is quadrilateral space & cotyloid fossa
  • if seen within 6 months of reduction of hip strongly good outcome

Question 11

What lines on X-ray help you identify hip dislocation in DDH?

Answer 11

• Hilgenreiner’s line= line thru r + l triradiate cartilage
  
  • Femoral head ossification should N be INFERIOR
• Perkins line= line perpendicular to hilgenreiner’s thru a point at a LATERAL margin of the ACETABULUM
  
  • Femoral head ossification should N be medial to this line
• SHENTON’S line- arc along inferior border of femoral neck and sup margin of obturator foramen
  
  • arc should be N continuous

Question 12

What lines on X-ray help you identify hip dysplasia in DDH?

Answer 12

• Acetabular Index- angle formed by a line drawn from point on the lateral triradiate cartilage to point on lateral margin of acetabulum and hilgenreiner’s line
  
  • should be < 25 degrees in pt>6/12
• CENTRE EDGE ANGLE of WILBERG
  
  • angle formed by a vertical line from the centre of the femoral head and a line from the centre of the femoral head to the lateral edge of the acetabulum
  • N is >20 degrees only reliable after 5 yrs

Question 13

When is USS recommended?

Answer 13

• At 4-6 weeks in baby with
• risk factors
• positive physical findings
• utilized follow Pavlik tx for equivocal exams

Question 14

What is the use of USS in DDH?

Answer 14

• it is DYNAMIC USS useful before femoral head ossifies at 4-6 months to identify the ALPHA ANGLE
  
  • Alpha angle created by lines along the bony acetabulum and ilium
  • normal >60degrees
  • BETA ANGLE - angle created by lines along labrum and ilium, normal <55 degrees
  • USED for assessing reduction of hip whilst in PAVLIK HARNESS- avoids unreduced hips eroding acetabulum
  • Not cost effective for routine screening

Question 15

What is the goal of tx?

Answer 15

• Based on Achieving and Maintaining early concentric REDUCTION in order to prevent FUTURE degenerative joint disease
• Tx is based on child’s age

Question 16

When is arthrogram useful in DDH?

Answer 16

• Used to confirm reduction after closed reduction under anesthesia
• Concentric reduction must be obtained with <5mm of contrast pooling medial to femoral head and the limbus must not be interposed
• Helps to identify blocks to reduction
  
  • Inverted Labrum
  • labrum reduces depth of acetabulum by 20-50% adn contributed to growth of acetabular rim
  • older child may be inverted and block cocentric reduction of the hip
  • Inverted limbus- rosethorn sign
  • a pathologic response of acetabulum to abnormal pressure caused by superior migration of the head
  • consists of fibrous tissue
  • Pulvinar
  • ligamentum teres
  • hip capsule constricted by iliopsoas tendon causing hour- glass deformity pf capsule

Question 17

When is Ct useful in DDH?

Answer 17

• Ct study of choice to evaulate reduction after closed reduction and spica casting
• MRI doesn’t play a significant role in primary diagnosis

Question 18

What is tx birth to 6 months ?

Answer 18

• HIP MUST BE REDUCIBLE
• Pavlik harness- abduction splinting
• check at 3 weeks USS to confirm femoral head reduction
• Requires normal muscle function CI in pt with spina bifidia
• Outcomes
  
  • success rate of 90%
  • abandon brace if not successful at 3-4 weeks

Question 19

What happens if no reduction on uss at 3 weeks in a child 0-6 months?

Answer 19

• Discontinue Pavlik harness to prevent pavlik disease
  
  • Erosion of pelvis superior to acetabulum -> difficulty with closed reduction
  • Consider closed reduction under GA with on table arthrogram as femoral head is not ossified. then spica cast post op MRI to confirm concentric reduction

Question 20

What is tx 6-18 months with a reducible hip ?

Answer 20

• Closed reduction under GA + arthrogram and spica casting
  
  • arthrogram allows to see femoral head/any obstuctions to reduction
  • Possible adductor tenotomy
  • Spica cast
  • Post op MRI to confirm concentric reduction

Question 21

What happens if this closed reduction fails or 6-18month old unreducable hip? Why does closed reduction fail?

Answer 21

• Then open reduction and spica cast
• Due to
  
  • INVERTED limbus
  • Pulvinar
  • HYPERTROPHIED Ligamentum teres
  • ILIOPSOAS CONTRACTURE
  • Capsular constriction

Question 22

What is tx >2 years with residual hip dysplasia ?

Answer 22

• Open reduction and Femoral oseotomy
  
  • Osteotomy to correct femoral anteversion and coxa valga
  • Also prevent AVN
  • aim is to congruently reduce the femoral head with GROM
  • May add in pelvic osteotomy often > 4yrs and if severe dysplasia accompanied by significant radiographic changes on acetabular side ie. Acetabular index >25 degrees

Question 23

What approach is used to open reduce the hip?

Answer 23

• Anterior- smith peterson
• As less risk of injury to medial femoral circumflex vessel

Question 24

Could a medial approach be used?

Answer 24

• Yes
• Advantages can be used in child <12 months
  
  • directly addresses block to reduction.
  • less blood loss but disadvantages- unable to preform capsulorrhapy and high associated risk of AVN

Question 25

What is the position of the childs hips in the pavlik harness?

Answer 25

* Within safe zone * **Flexion 90-100 degrees**- control anterior straps * **Abduction 50 degrees-** control posterior straps

Question 26

What can positions outwith the safe zone cause?

Answer 26

* Abduction \>60 * Causes * **AVN ** * ​impingment of posteriorsuperior retinacular branch of middle femoral circumflex artery * **transient femoral n palsy** * **​due to hyperflexion**

Question 27

How long is the harness worn for?

Answer 27

* **23 hours a day for at least 6 weeks** * uss at **3 wee**ks to _confirm reduced_ * wean out of harness over 6-8 weeks after hip has stabilised * confirm hip position with uss every 4-6 weeks

Question 28

What position in the hip placed in the spica cast? How long do they remain in it? How frequently are they changed?

Answer 28

* **flexion 100 degrees** * **abduction 45 degrees** **​** * Remain in spica for **3 months** * Changed every every **6 weeks**

Question 29

What pelvic osteotomy would you use in a young child?

Answer 29

* Salter Open triradiate cartilage * _single osteotomy cut above acetabulum_ **thru ILIUM to sciatic notch acetabulum** * hinges **thru pubic symphysis** * can provide 20-25 degrees lateral and 10-15 anterior coverage may lengthen up to 1cm

Question 30

What pelvic osteotomy would you use in an older child?

Answer 30

* **Triple STEELE** * Salter osteotomy plus inferior and superior rami cut * acetabular reorientation proceedure * triradiate cartilage must be open * Reorientation proceedure

Question 31

What pelvic osteotomy would you use in a child \> 8 years with a closed triradiate cartilage?

Answer 31

* Ganz or A Shelf salvage proeceedure * Ganz- multiple ostetomies in the pelvis, ilium and ischium nr the acetbulum- improves 3d correction but technically the most challenging . * SHELF- when you add bone to the lateral WB surface of the acetabulum by extra-articular buttress of bone over sublimed femoral head. it depends on the fibrocartilage metaplasia for successful results

Question 32

What the general complications of DDH tx?

Answer 32

* **Osteonecrosis** * All forms of tx * excessive/ forceful abduction * previous failed closed tx * repeat surgery * seen on xray- failure of growth of ossificaiton nucleus 1yr after reduction * broadening of femoral neck * increased density & fragmentation of ossified head * **Recurrence** * Approx 10% with appropriate tx * radiological follow up until skeletal maturity * * **Delayed diagnosis**

Question 33

What if a child presents late with bilateral dislocations if aged 6 or older?

Answer 33

* Pt typically functions better if hips NOT reduced

Question 34

What if a child presents late with unilateral dislocation if aged 8 or older? What can be done about their LLD?

Answer 34

* **Better outcomes without surgical tx** if patient aged 8 or more * **Epiphysiodesis**