infant hip

developmental dysplasia of the hip (DDH)

• a congenital anomaly that may be described as a shallow hip socket

• the ball of the hip (the femoral head) is prohibited from resting appropriately in the natural socket (the acetabulum) which is provided for it on the pelvis

what is thought to be the cause DDH?

abnormal fetal ligament development within the hip that is intensified by the excessive levels of circulating maternal estrogen

risk factors for DDH include:

• fetal malposition, such as breech

• oligohydramnios

DDH is more common in what population?

females

what side does DDH most often affect?

left side

DDH has been linked with what other diseases?

• spina bifida

• arthrogryposis

what are the 2 clinical tests that can be performed to evaluate an infant for DDH?

• Barlow test

• Ortolani test

Barlow test

• used to evaluate hip for dislocation

• the hip is flexed and adducted, and the knee is pushed posteriorly and superiorly

Ortolani test

• evaluates for the reduction or relocation of a dislocated hip

• performed by abducting and lifting the thigh, essentially relocating the hip back into the acetabulum

• an audible “click” may be heard and a palpable “clunk” felt as the head of the femur passes over the acetabulum

subluxation

partial dislocation of the hip

sonographic appearance of the femoral head:

hypoechoic rounded structure that contains echogenic stripes throughout

sonographic appearance of the ilium:

can be noted appearing to extend from the femoral head as an echogenic linearly structure producing an acoustic shadow

what transducer is used to scan the infant hip?

a high-frequency linear transducer

The sonographic diagnosis of DDH can be definitive when:

the femoral head rests clearly outside the acetabulum, denoting dislocation

sonographic appearance of a normal hip:

the femoral head rests centrally within the acetabulum

sonographic appearance of a subluxed hip:

the femoral head rest more laterally

Graf technique

• obtained in the coronal view

• used to measure the relationship of the femoral head and acetabulum by evaluating alpha and beta angles created by the relationships of these structures

• the smaller the alpha angle and the larger the beta angle, the more likely the infant is suffering from DDH

• The α angle is equal to or greater than 60 degrees in infants with seated hips and less than 50° in patients with dysplasia. The β angle increases proportionally with the degree of hip dysplasia and displacement.

Another test can be used to evaluate the amount of coverage of the femoral head by the acetabulum by obtaining:

• a coronal image and drawing parallel lines along the ilium and the maximum depth and height of the femoral head

• coverage of the femoral head by the acetabulum of greater than 55% is said to be normal, whereas 50% or less is said to be shallow, and less than 45% is considered very shallow

what is a nonsurgical treatment for DDH?

casting or by means of a Pavlik harness

clinical findings of DDH:

• history of breech birth

• family history of DDH

• asymmetrical skin folds on the legs

• leg length discrepancy

• limited limb abduction

• positive Barlow or Ortolani test

sonographic findings of DDH:

• femoral head located completely outside the acetabulum → complete dislocation

• partially coverage of the femoral head by the acetabulum → subluxation

• evidence of a shallow acetabulum → < 50% coverage of femoral head

• small alpha angle → Graf technique

• large beta angle → Graf technique

hip joint effusion

• the buildup of fluid within the hip secondary to inflammation and is most likely the result of transient synovitis

• typically occurs in children between 5 and 10 years of age

transient synovitis/toxic synovitis/irritable hip

the most common cause of a painful hip and joint effusion in children

what causes transient synovitis?

• unknown

• viral causes, trauma, and an allergic reaction have been suspected

clinical findings of hip joint effusion:

• leg and knee pain

• reluctance to walk

• irritability

• low-grade fever

• mild leukocytosis

sonographic findings of hip joint effusion:

• anechoic or hypoechoic fluid that elevates the anterior capsule of the joint

• width of the abnormal hip joint capsule typically exceeds 5 mm