Low-frequency vibration emitted from unstable hip in human neonate.

Developmental dysplasia of the hip (DDH) continues to be an orthopedic enigma. Some authors still believe it is a purely birth phenomenon. Even with widespread birth screening, however, DDH continues to become evident later than three months of age, long after a satisfactory outcome can be guaranteed. In an effort to reduce the number of late manifestations, the authors have developed a noninvasive form of screening for DDH called vibration arthrometry. Five hundred neonates were examined in local maternity hospitals, according to the guidelines of Ortolani and Barlow. The new method involves the attachment of miniature accelerometers around the infant's pelvis. Using this method, it was possible to elicit vibration events from approximately one fourth (255 hips) of the hips tested; vibrations were recorded from normal hips (125), from "clicky" hips (128), and from unstable hips (two). Differences between "nil-felt" (clinically silent) and "click-felt" (palpable clicking on testing) were significant. Vibration testing can be seen as an aid in the manual palpation necessary to detect this crippling condition.