**4.8 Sound transmission test with extension/flexion**

The patient is placed supine and the pelvic limbs are aligned in extension and adduction; the tuning fork is placed on one knee and the stethoscope with its diaphragm is placed on the symphysis pubis; sound is captured; the knee and hip are flexed to 90° and the sound is perceived; it is considered positive if the bending sound increases, if it decreases or stays the same, it is considered negative (**Figure 5**) [34–37].

For the extension/flexion sound transmission test, the neonate is placed supine with the lower extremities in extension and adduction; the tuning fork is placed on the knee on one side and the stethoscope is placed on the symphysis pubis and the sound is perceived; the hip and knee are flexed to 90° and the sound is perceived: if

**Figure 3.** *Peter-Baden sign.*

#### **Figure 4.**

*a. Compared sound transmission. b. Sound transmission with extension/flexion.*

the sound is lower or equal, the hip is healthy, if the sound increase, the hip has DDH. The opposite side is subsequently evaluated [34–37].

Sound transmission test with bone radar ® (University of Guanajuato, Mexico) or electroacoustic probe (Patent pending, University of Guanajuato) [35, 36].

Starting from the properties of bone to transmit sound, we developed a device to apply sound transmission tests in an objective way. The device consists of a sound

*Diagnosis of Developmental Dysplasia of the Hip in Newborns and Infants DOI: http://dx.doi.org/10.5772/intechopen.104085*

#### **Figure 5.**

*The above figures are using device in flexion of the hip.*

generator, a receiver placed on a stethoscope and a screen where the sound waves appear transformed into digits [35–37].

For the comparative sound transmission test, the newborn is placed supine with the pelvic limbs in extension and adduction; the sound generator is placed on the knee on one side and the receiver on the symphysis pubis, the digits are recorded on screens; the sound generator is placed on the opposite knee and the digits are recorded on the screen. If there is a difference in the numbers on either side, it is considered positive. In cases of bilateral CDD, the record will be the same on both sides [34–37].

For the extension/flexion sound transmission test, the neonate is placed supine with the lower extremities in extension and adduction; the sound generator is placed on the knee on one side and the receiver is placed on the symphysis pubis and the digits are recorded on the screen; the hip and knee are flexed to 90° and the digits are recorded on the screen; If the digits on the screen are greater in flexion than in extension, it is considered positive. The opposite side is subsequently evaluated [34–37].

For sound transmission test with electroacoustic probe, the technique is the same that bone radar ®, only the digits in screen are decibels.

#### **4.9 Complementary clinical diagnosis**

When the child is walking, look for the Trendelenburg and Duchenne signs. Older children who are already wandering, with undiagnosed CDD, present claudication, duck gait (in bilateral cases), increased lumbar lordosis, toe gait, and a discrepancy in the length of the lower extremities.

### **5. Complications**

Recurrent dislocation, avascular necrosis of the femoral head, femoral fracture, and nerve palsy are the most common. The most fearsome complication is avascular necrosis of the femoral head, which is due to the reduction, producing cartilaginous

compression and occlusion of extraosseous and intra-articular epiphyseal vessels, causing partial or total necrosis of the femoral head.
