Journal of Perinatology (2016), 1–5 © 2016 Nature America, Inc. All rights reserved 0743-8346/16 www.nature.com/jp
ORIGINAL ARTICLE
Sonographic screening for developmental dysplasia of the hip in preterm breech infants: do current guidelines address the specific needs of premature infants? J Lee1, RM Spinazzola1, N Kohn2, M Perrin1 and RL Milanaik1 OBJECTIVE: To assess the association between gestational age versus corrected age at the time of hip ultrasound with findings for developmental dysplasia of the hip (DDH) in preterm breech infants. STUDY DESIGN: A retrospective medical chart review was conducted to examine hip ultrasounds of 318 premature breech infants for findings associated with DDH. RESULTS: Positive findings for DDH occurred in 3/135 (2%) of infants o 32 weeks gestational age and 17/183 (9%) of infants 32 to o37 weeks gestational age (odds ratio: 0.22, 95% CI: 0.04 to 0.79, P o 0.015). No infants born o 32 weeks gestational age had abnormal findings for DDH upon follow-up ultrasound. Infants o 40 weeks corrected age at the time of hip ultrasound were more likely to have DDH findings compared with infants ⩾ 44 weeks corrected age (odds ratio: 7.83, 95% CI: 2.20 to 29.65, P o0.001). CONCLUSION: Current hip ultrasonography policies that include screening of premature breech infants may need to be revised. Journal of Perinatology advance online publication, 25 February 2016; doi:10.1038/jp.2016.7
INTRODUCTION Developmental dysplasia of the hip (DDH) is a condition in which an abnormal relationship occurs between the femoral head and acetabulum of the immature hip. Breech presentation can cause prolonged knee extension in utero resulting in sustained hamstring forces on the hip, and is associated with an increase in prevalence of 11 to 50% in DDH cases.1,2 DDH risk for newborns in breech presentation is 120 per 1000 for females and 26 per 1000 for males.3 Other factors consistently associated with DDH include primiparity, oligohydramnios and family history.2 If left untreated, complications of DDH may result in functional disabilities, leg length discrepancies and early onset osteoarthritis.4 All neonates as part of the newborn examination should be screened for DDH using Barlow and Ortolani maneuvers. However, it is recommended that infants at increased risk are selectively screened using hip ultrasound (US), which may identify dysplastic hips that are clinically normal or with equivocal clinical findings.5,6 Hip US screening for high-risk infants is recommended at 4 to 6 weeks after birth, and the 2000 AAP guidelines recommend hip US at 6 weeks of age for all female breech infants and optionally for breech males.7,8 Current screening practices for preterm infants are based on recommendations for term infants, even though preterm infants have been shown to have a lower frequency of DDH compared with term infants.2 The prevalence of breech presentation increases as the gestational age (GA) decreases below 37 weeks, with 1 to 3% of births at term, 7% of births at 32 weeks gestation and 22% of births prior to 28 weeks gestation.9 By 32 weeks gestation, the fetus has usually undergone a spontaneous physiological in utero version from breech to vertex presentation10 although a significant proportion of breech preterm infants screened for DDH includes those born before
32 weeks GA. Since the maturation of the hip is a dynamic process that continues into the postnatal period, optimal timing of hip US and identification of patients who need follow-up are important to reduce unnecessary treatment.11 When performed at too young an age, hip US screening has been shown to increase the risk for overtreatment.12 The merits of US screening for breech preterm infants born before 32 weeks GA are inconclusive. The results of a study by Quan et al.13 showed breech preterm infants o 37 weeks GA to have comparable incidence of DDH to breech term infants, although their study was limited in the number of very-preterm breech infants o 32 weeks GA. Infants born prior to in utero version may not undergo the sustained mechanical forces necessary to predispose to DDH. In addition to the lack of in utero mechanical stresses, the timing of hip US with respect to the corrected age of premature breech infants may influence hip US findings for DDH. If infants are not corrected for prematurity, hip US may be performed at a corrected age below the recommended age for screening at 4 to 6 weeks after birth (o 44 weeks corrected age). Owing to the discrepancy in DDH diagnosis that includes a spectrum of abnormalities from hip immaturity to hip dislocation, early hip US screening may have a higher risk for falsepositive DDH findings secondary to immaturity, necessitating rescreening. Knowing the risk of DDH for preterm breech infants o32 weeks GA and the magnitude of DDH risk based upon corrected age at the time of hip US may have important implications in potentially reducing the number of unnecessary and costly hip US screenings for the preterm breech infant population. The aim of the present study was to compare the incidence of abnormal findings on hip US for DDH in preterm infants o32 weeks GA with preterm infants 32 to o37 weeks GA born in the breech presentation. A secondary aim was to investigate
1 Cohen Children's Medical Center of New York, Lake Success, NY, USA and 2The Feinstein Institute for Medical Research, Manhasset, NY, USA. Correspondence: Dr RL Milanaik, Department of Pediatrics, Cohen Children’s Medical Center of New York, 1983 Marcus Avenue, Suite 130, Lake Success, NY 11042, USA. E-mail: [email protected] Received 17 July 2015; revised 8 January 2016; accepted 12 January 2016
Hip ultrasound screening of preterm breech infants J Lee et al
2 Table 1.
318 Preterm Breech Infants
Baseline characteristics according to GA group Infants o32 weeks GA (n = 135)
Infants 32–37 weeks GA (n = 183)
P
28.7 (2.3)
34.1 (1.3)
o0.0001
65 (48) 1158 (414)
99 (54) 2070 (440)
0.31 o0.0001
32 (5)
32 (5)
1.0
Mother’s parity 0 1 2+
65 33 28
96 43 38
0.73 0.79 0.89
Multiple gestation 1 2 3 4
74 44 11 6
71 102 10 0
0.006 o0.0001 0.37 0.006
Characteristic 135 (42%): infants
ORIGINAL ARTICLE
Sonographic screening for developmental dysplasia of the hip in preterm breech infants: do current guidelines address the specific needs of premature infants? J Lee1, RM Spinazzola1, N Kohn2, M Perrin1 and RL Milanaik1 OBJECTIVE: To assess the association between gestational age versus corrected age at the time of hip ultrasound with findings for developmental dysplasia of the hip (DDH) in preterm breech infants. STUDY DESIGN: A retrospective medical chart review was conducted to examine hip ultrasounds of 318 premature breech infants for findings associated with DDH. RESULTS: Positive findings for DDH occurred in 3/135 (2%) of infants o 32 weeks gestational age and 17/183 (9%) of infants 32 to o37 weeks gestational age (odds ratio: 0.22, 95% CI: 0.04 to 0.79, P o 0.015). No infants born o 32 weeks gestational age had abnormal findings for DDH upon follow-up ultrasound. Infants o 40 weeks corrected age at the time of hip ultrasound were more likely to have DDH findings compared with infants ⩾ 44 weeks corrected age (odds ratio: 7.83, 95% CI: 2.20 to 29.65, P o0.001). CONCLUSION: Current hip ultrasonography policies that include screening of premature breech infants may need to be revised. Journal of Perinatology advance online publication, 25 February 2016; doi:10.1038/jp.2016.7
INTRODUCTION Developmental dysplasia of the hip (DDH) is a condition in which an abnormal relationship occurs between the femoral head and acetabulum of the immature hip. Breech presentation can cause prolonged knee extension in utero resulting in sustained hamstring forces on the hip, and is associated with an increase in prevalence of 11 to 50% in DDH cases.1,2 DDH risk for newborns in breech presentation is 120 per 1000 for females and 26 per 1000 for males.3 Other factors consistently associated with DDH include primiparity, oligohydramnios and family history.2 If left untreated, complications of DDH may result in functional disabilities, leg length discrepancies and early onset osteoarthritis.4 All neonates as part of the newborn examination should be screened for DDH using Barlow and Ortolani maneuvers. However, it is recommended that infants at increased risk are selectively screened using hip ultrasound (US), which may identify dysplastic hips that are clinically normal or with equivocal clinical findings.5,6 Hip US screening for high-risk infants is recommended at 4 to 6 weeks after birth, and the 2000 AAP guidelines recommend hip US at 6 weeks of age for all female breech infants and optionally for breech males.7,8 Current screening practices for preterm infants are based on recommendations for term infants, even though preterm infants have been shown to have a lower frequency of DDH compared with term infants.2 The prevalence of breech presentation increases as the gestational age (GA) decreases below 37 weeks, with 1 to 3% of births at term, 7% of births at 32 weeks gestation and 22% of births prior to 28 weeks gestation.9 By 32 weeks gestation, the fetus has usually undergone a spontaneous physiological in utero version from breech to vertex presentation10 although a significant proportion of breech preterm infants screened for DDH includes those born before
32 weeks GA. Since the maturation of the hip is a dynamic process that continues into the postnatal period, optimal timing of hip US and identification of patients who need follow-up are important to reduce unnecessary treatment.11 When performed at too young an age, hip US screening has been shown to increase the risk for overtreatment.12 The merits of US screening for breech preterm infants born before 32 weeks GA are inconclusive. The results of a study by Quan et al.13 showed breech preterm infants o 37 weeks GA to have comparable incidence of DDH to breech term infants, although their study was limited in the number of very-preterm breech infants o 32 weeks GA. Infants born prior to in utero version may not undergo the sustained mechanical forces necessary to predispose to DDH. In addition to the lack of in utero mechanical stresses, the timing of hip US with respect to the corrected age of premature breech infants may influence hip US findings for DDH. If infants are not corrected for prematurity, hip US may be performed at a corrected age below the recommended age for screening at 4 to 6 weeks after birth (o 44 weeks corrected age). Owing to the discrepancy in DDH diagnosis that includes a spectrum of abnormalities from hip immaturity to hip dislocation, early hip US screening may have a higher risk for falsepositive DDH findings secondary to immaturity, necessitating rescreening. Knowing the risk of DDH for preterm breech infants o32 weeks GA and the magnitude of DDH risk based upon corrected age at the time of hip US may have important implications in potentially reducing the number of unnecessary and costly hip US screenings for the preterm breech infant population. The aim of the present study was to compare the incidence of abnormal findings on hip US for DDH in preterm infants o32 weeks GA with preterm infants 32 to o37 weeks GA born in the breech presentation. A secondary aim was to investigate
1 Cohen Children's Medical Center of New York, Lake Success, NY, USA and 2The Feinstein Institute for Medical Research, Manhasset, NY, USA. Correspondence: Dr RL Milanaik, Department of Pediatrics, Cohen Children’s Medical Center of New York, 1983 Marcus Avenue, Suite 130, Lake Success, NY 11042, USA. E-mail: [email protected] Received 17 July 2015; revised 8 January 2016; accepted 12 January 2016
Hip ultrasound screening of preterm breech infants J Lee et al
2 Table 1.
318 Preterm Breech Infants
Baseline characteristics according to GA group Infants o32 weeks GA (n = 135)
Infants 32–37 weeks GA (n = 183)
P
28.7 (2.3)
34.1 (1.3)
o0.0001
65 (48) 1158 (414)
99 (54) 2070 (440)
0.31 o0.0001
32 (5)
32 (5)
1.0
Mother’s parity 0 1 2+
65 33 28
96 43 38
0.73 0.79 0.89
Multiple gestation 1 2 3 4
74 44 11 6
71 102 10 0
0.006 o0.0001 0.37 0.006
Characteristic 135 (42%): infants
