To determine whether a routine ultrasonography (US) is necessary for diagnosis of developmental dysplasia of hip (DDH), presenting with congenital muscular torticollis (CMT).

Cases of 133 patients (81 males, 52 females) diagnosed as CMT were reviewed, retrospectively. We reviewed the medical charts and diagnostic examination. We also assessed the coincidence of CMT and DDH, and investigated the clinical features of CMT related to DDH.

Twenty (15.0%) patients out of 133 CMT patients were diagnosed as having DDH by US. Of whom, 8 patients were radiographically positive and 4 patients were both clinically and radiographically positive. Nine patients were treated with a harness and 1 of them needed closed reduction and casting. Out of 9 patients treated with a harness, only 4 were clinically positive. The difference and ratio of the sternocleidomastoid (SCM) muscle thickness between the normal and abnormal side was significantly greater in DDH patients (p=0.014). Further, receiver operating characteristic analysis showed when the SCM ratio is greater than 2.08 and the SCM difference is greater than 6.1 mm, the efficiency of US for the diagnosis of the DDH was found to be the best (p<0.05).

To evaluate DDH, physical examination showed low sensitivity and radiologic study has limitation for the child before 4 to 6 months of age. Therefore, we recommend that hip is screened by US for the diagnosis of DDH associated with CMT when physical examination is positive or CMT patients with large SCM difference and high SCM ratio.