The relationship between developmental dysplasia of the hip and congenital muscular torticollis.

Multiple studies report a correlation between congenital muscular torticollis (CMT) and developmental dysplasia of the hip (DDH) at a rate between 2% and 29%. Most of these studies were completed before the routine use of hip ultrasound. This study assesses the incidence of DDH in a referral population with CMT and the incidence of CMT in a referral population with DDH. We retrospectively reviewed 186 patients referred with a primary diagnosis of DDH and 109 patients referred with a primary diagnosis of CMT between 1995 and 2004. All patients were screened for DDH with ultrasound if they were younger than 4 months and plain radiographs in older children. Among the patients with a primary diagnosis of DDH, 5.9% were subsequently diagnosed with CMT. However, infants who were less than 1 month old when diagnosed with DDH had a 9% risk of subsequent development of CMT. Among the patients primarily diagnosed with CMT, 3.7% were subsequently diagnosed with DDH. Among the patients with DDH, there was a 7.9% coexistence of CMT, regardless of which was diagnosed first, and among the patients with CMT, there was a 12.5% coexistence of DDH. Boys with DDH were 4.97 times more likely than girls to have both DDH and CMT regardless of which diagnosis preceded the other. Our results confirm that patients with CMT should be screened for DDH, and infants, especially boys, treated for DDH should be followed for the development of CMT.