Infant Hip Ultrasound Developmental Dysplasia of the Hip 6/22/17 Jenelle Beadle

Hip Anatomy

Developmental Dysplasia of the Hip (DDH) Abnormal development of the acetabulum Acetabulum: “ball” of the ball-and-socket Normal DDH

Formation and development of the hip Joint formation is completed by 11wks gestation As growth occurs, the acetabulum requires contact and pressure from the femoral head to maintain and develop its shape into a deep socket

Factors affecting hip development An abducted position maximizes the force of the femoral head on the acetabulum, and is ideal for acetabular development There is an ideal position for this requirement of contact and pressure Abduction Directs force into joint Optimal for development

Factors affecting hip development An abducted position maximizes the force of the femoral head on the acetabulum, and is ideal for acetabular development Sustained adduction positioning may result in a shallow acetabulum Opposite is true for adduction Abduction Directs force into joint Optimal for development Adduction Directs force away from joint Bad for development

Factors affecting hip development An abducted position maximizes the force of the femoral head on the acetabulum, and is ideal for acetabular development Sustained adduction positioning may result in a shallow acetabulum If the femoral head is dislocated, pressure on the acetabulum is completely removed and it begins to grow shallow Dysplasia progresses if the femoral head does not reduce or “relocate” Typically a prenatal cause of dysplasia Even worse than an adducted position is dislocation

Factors affecting hip development An abducted position maximizes the force of the femoral head on the acetabulum, and is ideal for acetabular development Sustained adduction positioning may result in a shallow acetabulum If the femoral head is dislocated, pressure on the acetabulum is completely removed and it begins to grow shallow Dysplasia progresses if the femoral head does not reduce or “relocate” Typically a prenatal cause of dysplasia acetabulum requires contact and pressure from the femoral head to maintain and develop its shape Lack of contact and pressure causes dysplasia: dislocation adducted position

Hip Dysplasia Causes 4 periods of development with increased risk: 12wks – fetal legs rotate medially risk for dislocation

Hip Dysplasia Causes 4 periods of development with increased risk: 12wks – fetal legs rotate medially risk for dislocation 18wks – hip muscles develop neuromuscular problems may lead to dislocation

Hip Dysplasia Causes 4 periods of development with increased risk: Frank Breech 20% Incidence DDH 4 periods of development with increased risk: 12wks – fetal legs rotate medially risk for dislocation 18wks – hip muscles develop neuromuscular problems may lead to dislocation 36-40wks – mechanical factors oligohydramnios and breech presentation both force the fetus into an adducted position Abducted Adducted

Hip Dysplasia Causes 4 periods of development with increased risk: 12wks – fetal legs rotate medially risk for dislocation 18wks – hip muscles develop neuromuscular problems may lead to dislocation 36-40wks – mechanical factors oligohydramnios and breech presentation both force the fetus into an adducted position Postnatal - mechanical factors positioning that forces the infant into an adducted position (worse if legs are extended)

Developmental Dysplasia of the Hip (DDH) Abnormally formed acetabulum (shallow socket) DDH Normal Acetabulum However it happens, these kids end up with DDH.

Developmental Dysplasia of the Hip (DDH) Abnormally formed acetabulum (shallow socket) results in instability of the joint (ball doesn’t stay in it) A shallow socket results in instability

Degree of hip instability Subluxation Femoral head moves within the acetabulum Dislocation Femoral head has no contact with the acetabulum Assessed by performing dynamic maneuvers with live ultrasound observation Barlow test We take measurements to assess how deep/shallow the acetabulum is, But we have to dynamically exam the hip to assess it’s stability

Barlow Test Designed to stress and dislocate an unstable hip Adduct and push posteriorly monitor for subluxation or dislocation Performed blindly by pediatricians as a routine screening feel for a “clunk” that indicates dislocation Pressure required is mild

Ortolani Test Designed to identify dislocated hips by manual reduction Abduct while pulling slightly on the leg Performed by pediatricians in conjunction with the Barlow test feel for a “clunk” that indicates reduction Not useful in sonographic evaluation

Treatment Remember: A lack contact and pressure causes dysplasia of the acetabulum: dislocation adducted position Designed to encourage natural acetabular growth and development Improve contact and pressure of the femoral head on the acetabulum by: reduction abducted position Treat by improving …

Treatment Double diapering Pavlik harness Spica cast Surgery no longer recommended Pavlik harness 1-6 mos old Duration: 6+ wks Spica cast 6-24 mos old Duration: Surgery open reduction repair femoral neck angle osteotomy >2yrs spica cast used for recovery period

Infant Hip Ultrasound Indications Evaluation for developmental dysplasia of the hip (DDH) Assess progress during treatment Establish normalcy and stability post treatment

When should US evaluation for DDH be performed? Direct signs of DDH positive findings on Ortolani or Barlow (clunk) Secondary signs of DDH that persist >2 weeks Leg length discrepancy Asymmetrical thigh folds Equivocal dynamic testing Significantly increased risk for DDH breech presentation Mild risk factors alone are not considered significant enough to warrant an ultrasound screening female family history Whenever it’s ordered…

Things to consider: Scheduling Scanning Evaluation of infants <4 wks is not recommended normal ligament elasticity can create false positive results Evaluation of infants >6 mos (adjusted age) becomes limited ossification of femoral head reduces accuracy Scanning Sonographer may perform entire exam Radiologist required to participate in dynamic evaluation Warm blankets, warm gel, pacifiers warm, sterile gel is required for neonates Older than 4wks, but younger than 6mos

Acetabulum Triradiate Cartilage Formed by the three pelvic bones Ilium (40%) forms the upper “roof” – where US measurement is performed Ischium (40%) forms the posterior and inferior portion Pubis (20%) forms the anterior boundary Triradiate Cartilage Left Lateral View Formed where the three pelvic bones meet Allows for growth of the acetabulum and pelvis Closes off by 15yrs Ilium = roof (where measurement is made) Ischium = posterior Pubus = anterior

Right Lateral View

Infant hip ossification White = Cartilage Shaded = Ossified Bone Puberty Birth US of the hip is performed when the hip is largely cartilaginous

9 Months 2 Months Child Adult

Coronal Plane Flexed or neutral Degree of flexion will change visualized femoral anatomy Head, GT, metaphysis P

Coronal Plane Ilium Triradiate cartilage Labrum straight & parallel to the transducer sharp ilium-roof angle Triradiate cartilage Labrum P

Coronal Plane Right Left Right and left appear identical (label carefully) Right Left

Measurement: Alpha Angle Angle that the acetabular roof makes with the ilium reflects the depth of the acetabulum Normal: >60 degrees Rt

Measurement: Femoral Head Coverage Percentage of the femoral head within the acetabulum reflects how the femoral head is seated within the joint Normal: >50% Rt

Transverse Plane Flexed or neutral Barlow Degree of flexion will change visualized femoral anatomy Head, GT, metaphysis Barlow

Transverse Plane

Transverse Plane Right and left are mirrored Right Left

Transverse Plane Right Left Posterior Posterior Ischium Ischium Pubis Tri Cart Pubis Tri Cart

Barlow Test Designed to stress and dislocate an unstable hip Adduct and push posteriorly monitor for subluxation or dislocation 2-3 mm of movement is normal

Transverse Plane - Barlow Barlow forces the hip posterior Right Left Posterior Posterior