Ultrasound of the Infant Hip with Developmental Dysplasia

Harry H. Holdorf

PhD, MPA, RDMS, RVT

Objectives

• Identify normal vs. abnormal sonographic anatomy• Identify risk factors associated with DDH• Define the classifications of developmental dysplasia of the hip• Understand the use of hip angle measurement tools

Developmental dysplasia of the hip (DDH)• Developmental dysplasia of the hip ranges from mild acetabular

dysplasia to irreducible dislocation of the femoral head• Ultrasound is an excellent method in the diagnosis of DDH

Congenital Hip Displacement

• Developmental dysplasia of the hip (DDH) was formerly referred to as congenital dislocation of hip. • DDH is now the preferred term to reflect that DDH is an

ongoing developmental process, which is variable in presentation and not always detectable at birth. • Developmental dysplasia of the hip refers to a spectrum

of severity ranging from mild acetabular dysplasia with a stable hip, to more severe forms of dysplasia with neonatal hip instability, to established hip dysplasia with or without later subluxation or dislocation.

Epidemiology

• Developmental dysplasia of the hip affects 1-3% of newborns and is responsible for 29% of primary hip replacements in people up to the age of 60 years.• The left hip is dislocated more often than the right and 20% of cases

are bilateral.• It is more common in cultures that use swaddling of babies, forcing

the hips into extension and adduction.

• It has been reported that ultrasound screening seems to prevent many, but not all, operations for developmental hip dysplasia.• Selective ultrasound examination for babies with specific risk factors is

recommended. An ultrasound examination of the hips should be performed if: • There is a first degree family history of hip problems in early life, unless

DDH has been definitely excluded in that relative.• A breech presentation:• at or after 36 completed weeks of pregnancy, irrespective of presentation at

delivery or mode of delivery, or• at delivery if this is earlier than 36 weeks.• In the case of a multiple birth, if any of the babies falls into either of these

categories, all babies in this pregnancy should have an ultrasound examination.

Risk Factors of DDH• Female sex• Family history (parental or sibling)• Breech Presentation• Multiple Gestations• Certain neuromuscular disorders i.e.: congenital torticollis• Oligohydramnios• Hip click (on clinical exam)• Club foot deformity• Asymmetric skin folds• High birth weight

History of diagnosing DDH

• In the 1980’s Dr. Graf developed a technique using ultrasound to replace radiography to diagnose DDH. • Dr. Hacke introduced dynamic imaging to hip sonography in 1984.

Method

Coronal View

Baby in lateral Decubitis or supine position

Flex knee 90 degrees

Transducer parallel and lateral to hip

Image should show femoral head centered in joint space.Ilium appears as straight line perpendicular to femoral head and parallel to transducer

Coronal View (Non-Stress

Coronal View (non-stress)

• Includes the following anatomy• Ilium• Acetabular Rim• Femoral Head• Ischium• Labrum• Greater Trochanter

Anatomy (non Stress)

Femoral Head

Ilium

Acetabular Rim

Greater Trochanter

Labrum

Method Continued

Transverse view Infant in oblique positionKnee flexed 90 degreesRotate transducer 90 degrees from coronalFemoral head should be centered on triradiate cartilageStress the hip in this view

• Steps to Stress the HIP

Flex hip 90 degrees

Push the knee gently Posteriorly

Transverse View NON-STRESS

Include:Femoral ShaftGreater TrochanterIschiumFemoral Head

Anatomy (Non-Stress Transverse)

Femoral Head

Ischium

Ultrasound of the new-born HIP

• Birth to 4 months of age• High frequency linear transducer • Multiple focal zones• Output power at 100%• Feed baby during exam

Technique Continued…• Decubitus position• Place a small rolled up towel behind the back. • Hip is flexed 90 degrees• Use both hands to stabilize the baby • Foot pedal

Angle Measurement

• Baseline Passes through plane of Ilium.• Alpha Angle• Most common• Angle between baseline and roofline• Measures acetabular Concavity

Angle Measurement continued…• Beta Angle• Angle between baseline

And inclination lineIndicates acetabular roof

CoverageAnything less than 55 degrees

is normal

Graf Classification

Graf Type 1

• Covers femoral head• Acetabular rim is angular• Labrum is in normal position• Hip angle measurement is greater than 60 degrees

Graf Type 1Non Stress

Graf Type IIa

• Patients less than 3months of age• Femoral head is not displaced• Acetabular rim is rounded• Labrum in normal position• Hip angle measurement is between 50-59 degrees • Repeat scan in 6-8 weeks

Graf Type IIa Non-Stress

Graf Type IIb

• Patients greater than 3 months of age• Femoral head is not displaced• Acetabular rim is rounded• Labrum is in normal position• Alpha angle is 50-59 degrees• Orthopedic referral is suggested

Graf Type IIb (non stress)

Graf Type IIc

• Femoral head less than 50% covered• Acetabular is rounded• Labrum is everted, more horizontally positioned• Alpha angle is 43-49 degrees• Treatment and follow up suggested

Graf Type IIc

Graf Type IV non-stress

• Femoral head is almost completely displaced • Acetabular rim is flattened• Labrum trapped between femoral head and ilium• Hip angle is less than 43 degrees• Requires urgent referral and treatment

Graf Type IV non-stress

Example 1: Normal Graf Type I

Example 2:

• Graf Type IV• Femoral Head is displaced• Acetabular rim is

Flattened

Labrum is Trapped

Conclusion• While newborn screening for DDH allows for early detection of this

hip condition, starting treatment immediately after birth may be successful. • Many babies respond to the Pavlik harness, and/or casting. Additional

surgeries may be necessary since the hip dislocation can reoccur as the child grows and develops.• If left untreated, differences in leg length or a duck-like gait, and a

decrease in agility may occur. • In children 2 years or older with DDH, deformity of the hip and

osteoarthritis may develop later in life. DDH can also lead to pain and osteoarthritis by early adulthood.

The technique of examining the infant hip joint with real-time ultrasound is widely accepted. Since the cartilaginous femoral head is clearly imaged by ultrasound, anatomical structures and their relationships can be accurately determined. Dislocated hips are easily detected and subluxations also can be visualized.The method of examination using real-time ultrasound is considered to be reliable, accurate, and a useful adjunct to radiography. The advantages are that it is non-invasive, portable, and involves no exposure to radiation.