Mehrzad Mehdizadeh - Associate professor of Tehran University of Medical Sciences Children›s Hospital Medical Center

Developmental dysplasia of the hip (DDH) is one of the most common causes of disabilityamong children. DDH encompasses a wide variety of pathologic conditions, ranging fromfine acetabular dysplasia to irreducible hip dislocation. The previous term congenitaldysplasia of the hip has been replaced by developmental dysplasia of the hip, becausemany of the clinical manifestations of DDH may not be detectable at birth, but arerecognized at a later age .The incidence of DDH ranges from 1.5 to 20 per 1,000 births. Multiple risk factorshave been described, including breech positioning in utero, being the first-born child,oligohydramnios, family history, female sex, and deformities (postural or structural) ofthe foot and torticollis. In addition, increased joint laxity in the setting of exposure tomaternal estrogens during the perinatal period may play a role in the development ofDDH, and the left hip is more frequently affected than the right .Ultrasonography (US) is the preferred modality for evaluating the hip in infants agedless than 6 months. US enables dynamic evaluation of the hip with stress maneuvering,as well as direct imaging of the cartilaginous portions of the hip that cannot be seenon plain radiographs . Hip US has become the most commonly used diagnostic tool forDDH during early infancy because the early and accurate diagnosis of DDH is the mostimportant factor contributing to appropriate treatment .The Graf method is perhaps the most widely used US screening technique. If thewell-established techniques for examination, interpretation, and measurement aremeticulously followed, it is easy to manage newborn hip problems via this method .To perform hip US, the hip joints must be evaluated in the standard coronal plane witha linear array probe .Before evaluation of the hip joint, it is essential to identify thechondroosseous junction. This is because the echo of the chondro-osseous junction is animportant landmark used to identify the femoral neck and other anatomical landmarks:the femoral head, iliac bone, lower limb of the ilium, acetabular bony roof, cartilaginousacetabular roof, acetabular labrum, joint capsule, and synovial fold. The coronal view can be obtained with the hip in either the physiologic neutral position(°20-°15 flexion) . The ultrasound transducer is then placed in the anatomic coronalplane. Next, the transducer is moved backwards and forwards from the basic positionto identify the round structure of the hip joint andere lower limb. If the superior edgeof the transducer is rotated posteriorly by °10 to °15 into an oblique coronal plane, theilium will appear to be straight . If a sonogram contains a straight iliac wing contour andan apparent acetabular labrum, this indicates that it has a standard plane . However,in dislocated hips, lateral and posterior displacement of the femoral head preventsvisualization of the femoral head and the center of the acetabulum in the standard plane.Therefore, if the displaced femoral head is followed, the ultrasound plane is no longer inthe standard plane.As a general rule, the alpha angle determines the type and in some instances, the betaangle is used to determine subtype:• type I: alpha angle > 60 degrees (normal)o type Ia: beta angle <55 degreeso type Ib: beta angle > 55 degrees• type IIo type IIa: alpha angle 59-50 degrees (less than 3 months)o type IIb: alpha angle 59-50 degrees (greater than 3 months)o type IIc• alpha angle 49-43 degrees• beta angle 77-70 degrees• type D ( about to decenter )o alpha angle 49-43 degreeso beta angle > 77 degrees• type III: alpha angle <43 degreeso type IIIa and IIIb distinguished on the grounds of structural alteration of thecartilaginous roof• type IVo alpha angle < 43 degreeso dislocated with labrum interposed between the femoral head and acetabulumo inverted labrumTreatment of DDHThe current gold-standard treatment for DDH in newborns to infants aged 6 monthsremains the Pavlik harness. The Pavlik harness provides the best results, with a successrate of %95-%85, and thus should be started as early as possible to achieve the bestoutcome. The purpose of the harness is to maintain the hip in a flexed and abductedposition in order to bring the femoral head as close to the acetabular ring as possibleBetween 6 months and 2 years of age, closed reduction and casting is attempted undergeneral anesthesia to maintain the femoral head in the proper position without damagingit. Arthrography is a useful tool to evaluate the success of the reduction. The cast isapplied to the reduced hip for a period of approximately 12 weeks. If closed reductioncannot be accomplished at this stage, open reduction may be necessary.Open reduction is usually required above the age of 2 years, mostly by femoral osteotomyto relieve pressure over the femoral head and to reshape the acetabulum. The patient isusually immobilized in a spica cast for 12-6 weeks.