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.

A breech presentation: 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 position Knee flexed 90 degrees Rotate transducer 90 degrees from coronal Femoral head should be centered on triradiate cartilage Stress 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 Shaft Greater Trochanter Ischium Femoral 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 line Indicates acetabular roof Coverage Anything 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 1 Non 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.