Does gestational age affect ultrasonographic findings of the hip in preterm newborns? a sonographic study of the early neonatal period Altuğ Duramaz a , Burcu B. Duramaz b and Mustafa G. Bilgili a There are only a few studies in the literature investigating the effects of gestational age on developmental dysplasia of the hip. The aim of this study was to investigate the effects of gestational age on hip ultrasound findings in the early neonatal period in preterm newborns born between 30th and 36th weeks of gestational age. Between January 2008 and December 2013, a total of 788 hips of 394 premature newborns with a gestational age of up to 36th weeks who underwent hip ultrasonography in the first week of their life were retrospectively examined. The distribution of roof angles and hip types in terms of sexes was compared between groups. Birth weight, birth height, α, and β angles were analyzed in terms of the gestational age. The mean gestational age was 33.07 weeks (SD 2.09; between 30th and 36th). Six hundred and seven hips were classified as type I, 154 as type IIa, 21 as type IIc, and 6 as type III. In the 30th week, type IIc hips in females and type III hips in males were statistically significantly higher (P = 0.001). In the 34th week, type IIc hips in males were statistically significantly higher than the females (P = 0.013). In the 35th week, type IIa hips in females hips were statistically significantly higher than the males (P = 0.008). Among all preterm infants, type IIc hips were more common in the 30th, 31st, 32nd, and 34th weeks, whereas type III hips were statistically significantly more common in the 30th week (P = 0.0001). The 30th, 31st, 32nd, and 34th weeks of age are gestational ages that should be considered in terms of dysplastic and subluxed hips in premature newborns. J Pediatr Orthop B 00:000–000 Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved. Journal of Pediatric Orthopaedics B 2018, 00:000–000 Keywords: developmental dysplasia of the hip, gestational age, hip ultrasound, preterm newborns a Department of Orthopedics and Traumatology, Bakırköy Dr Sadi Konuk Education and Research Hospital and b Department of Pediatric Infectious Diseases, Bezmiâlem Vakıf University, Istanbul, Turkey Correspondence to Altuğ Duramaz, MD, Department of Orthopedics and Traumatology, Bakırköy Dr Sadi Konuk Education and Research Hospital, Tevfik Sağlam St Number 11, Istanbul 34147, Turkey Tel: +90 532 547 2308; fax: +90 212 414 6494; e-mail: altug.duramaz@yahoo.com Introduction Developmental dysplasia of the hip (DDH) is defined as the volume, shape, orientation, and organizational anomaly of the femoral head or the acetabulum, or both [1]. Acetabular dysplasia is characterized by an immature, shallow acetabulum that may result in subluxation of the femoral head. In a subluxated hip, the femoral head is displaced, but it has partial continuity with the acetabulum. In a dislocated hip, there is no contact between the acet- abulum and the femoral head. Hip ultrasound developed by Graf is commonly in use for the radiological evaluation of DDH [2]. Hip typing is performed with the evaluation of the acetabular bone roof (α angle) and the cartilage roof (β angle) by ultrasound. In this respect, type I hips are defined as normal, type II hips are defined as immature or dysplastic in their subgroups, and type III and type IV hips are described as subluxated and dislocated, respectively. Although newborn hip ultrasound (NHU) makes the hip- type description and further treatments more complicated in preterm babies, it plays an important role in early diagnosis of newborns with the clinical findings of DDH [3]. Graf emphasized the importance of gestational age in the ultrasound-based classification of hip dysplasia in preterm newborns. Graf catogorized the DDH according to chronological age, but he used adjusted age for patho- logical hip diagnosis and treatment planning [4]. As DDH is not well defined in preterm newborns, the effects of gestational age on DDH are controversial. There are some studies suggesting that prematurity is a risk factor for DDH [5,6]. However, DDH is reported to be less com- mon in preterm newborns in some studies [7,8]. However, prematurity was examined as an independent risk factor for DDH comprehensively in none of the studies. There are only a few studies in the literature investigating the effects of gestational age on DDH [9,10]. In this study, we investigated the effects of gestational age on hip ultrasound findings in the early neonatal period in preterm newborns born between 30th and 36th weeks of gestational age who did not have any risk factors for DDH. It was hypothesized that DDH tendency will increase as gestational age is reduced in preterms. Patients and methods All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee Original article 1 1060-152X Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/BPB.0000000000000541 Copyright r 2018 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.