ORIGINAL ARTICLE
Is There a Predilection for Breech Infants to Demonstrate Spontaneous Stabilization of DDH Instability? Eric J. Sarkissian, BS, Wudbhav N. Sankar, MD, Keith Baldwin, MD, MSPT, MPH, and John M. Flynn, MD
Background: Breech position subjects the fetal hip to abnormal mechanical forces. However, unlike genetic or tissue factors linked to developmental dysplasia of the hip (DDH), the causative effect of the breech position ends when the infant is born. The purpose of this study was to evaluate the rate of spontaneous stabilization in mildly unstable hips of breech-presenting infants compared with similarly lax hips in infants with a genetic or tissue-related cause of DDH. Methods: We studied a consecutive series of infants presenting to our institution at 8 weeks of age or younger with DDH from January 2008 to January 2012. Infants with increased hip laxity on dynamic ultrasound examination but without frank instability on clinical provocation maneuvers and no history of prior treatment were evaluated. The endpoint was spontaneous stabilization of ultrasound-detected instability, or intervention due to persistent instability on follow-up dynamic ultrasound. A logistic regression model using backward likelihood ratio method was used to analyze predictors of spontaneous stabilization. Results: We identified 122 hips in 79 infants with instability on dynamic ultrasound evaluation but with stable clinical examinations. Spontaneous stabilization of sonographic instability occurred in 90 hips (74%) at a mean age of 9 weeks (range, 4 to 18 wk). Breech hips more frequently spontaneously stabilized compared with nonbreech hips (80% vs. 66%). Regression analysis determined that breech presentation was a strong independent predictor for spontaneous hip stabilization (odds ratio, 3.72; 95% confidence interval, 1.45-9.60; P = 0.006). Sex, family history, intrauterine positioning syndromes, side involved, bilateralism, and grade of sonographic hip instability were not independently predictive of spontaneous hip stabilization. Conclusions: DDH infants with a history of breech presentation are 3.72 times more likely to experience spontaneous resolution of mild hip instability compared with nonbreech infants. Awareness that breech presentation is a strong independent predictor of spontaneous laxity resolution can guide parental counseling and early care of DDH. Level of Evidence: Level II, prognostic retrospective study.
From the The Children’s Hospital of Philadelphia, Philadelphia, PA. The authors declare no conflict of interest. Reprints: John M. Flynn, MD, The Children’s Hospital of Philadelphia Wood Building, 2nd Floor, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104. E-mail: fl[email protected]. Copyright r 2014 by Lippincott Williams & Wilkins
J Pediatr Orthop
Volume 34, Number 5, July/August 2014
Key Words: developmental dysplasia of the hip, breech presentation, ultrasound (J Pediatr Orthop 2014;34:509–513)
T
he etiology of developmental dysplasia of the hip (DDH) is multifactorial with both hereditary and environmental contributions acting as internal and external influences, respectively. Breech presentation, female sex, positive family history, first-born children, and left hip affected are commonly associated with DDH.1,2 Additional factors include intrauterine positioning syndromes (torticollis, metatarsus adductus, femoral anteversion, genu recurvatum, oligohydramnios, and twin pregnancy),3–6 swaddling,7 and hip capsular laxity.8,9 Of all factors linked to DDH, breech presentation may be the most critical. The reported frequency of breech presentation in DDH is between 17% and 23%.10–12 Prolonged flexion of the hip joint with knee extension pulls the femoral head downward and stretches the hip joint capsule, predisposing to hip instability, acetabular dysplasia, or both.13,14 However, the abnormal mechanical forces placed on the fetal hip by breech presentation end at birth. In contrast, genetic factors or tissue-related etiological factors may affect the individual beyond infancy into childhood, adolescence, and adulthood.8,15,16 Therefore, we hypothesize that after birth, the hips of breech-presenting infants with mild instability are more likely to stabilize without treatment in comparison with similarly lax hips in infants with a genetic or tissuerelated cause of DDH. The purpose of this study was to determine factors predictive of spontaneous stabilization, particularly breech presentation.
METHODS We studied infants presenting to our institution with DDH between January 2008 and January 2012 after obtaining approval from our institutional review board. We performed a retrospective chart review of 398 consecutive patients identified by ICD-9 codes for congenital dislocation of the hip, hip dysplasia, hip click, and hip laxity presenting at 8 weeks of age or younger with adequate documentation of clinical course. Inclusion criteria were infants with increased hip laxity on dynamic ultrasound examination and no history of prior treatment. Infants www.pedorthopaedics.com |
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with frank hip instability on clinical examination (positive Barlow or Ortolani maneuvers) were excluded, as they required immediate treatment with a Pavlik harness. Infants with a syndromal or neuromuscular disorder predisposing to DDH were excluded as well. All infants were examined by a fellowship-trained pediatric orthopaedic surgeon. All ultrasounds were performed by an experienced ultrasonographer to evaluate hip stability and acetabular morphology (normal: a–angle Z60 degrees) using the modified Graf method developed by Rosendahl et al.17 Infants were reevaluated at approximately 1 month after the initial visit with both an ultrasound and clinical examination to determine the progression or resolution of their ultrasonographic instability. The endpoint of the study was spontaneous stabilization of sonographic hip instability, or intervention due to persistent instability on follow-up dynamic ultrasound. After applying our inclusion and exclusion criteria, we identified 79 consecutive patients suitable for investigation. Bilaterally affected hips were treated separately for the purpose of this study. The presence or absence of known DDH risk factors were recorded from the medical records, particularly female sex, breech presentation, positive family history (in first-degree relative), left hip affected, and intrauterine positioning syndromes (torticollis, knee hyperextension, femoral anteversion, oligohydramnios, and twin pregnancy) (Table 1). We also TABLE 1. Demographics of Study Group and Proportion Demonstrating Spontaneous Stabilization n (%) Clinically Normal/ Sonographically Unstable Hips (n = 122) Sex Female Male Presentation Breech Nonbreech Family history Positive* Negative Intrauterine positioning syndromes Presentw Absent Side involved Left Right Bilateralism Bilateral Unilateral Grade of sonographic instability Minor Majorz
Spontaneously Stabilizing (n = 90)
98 (80) 24 (20)
72 (73) 18 (75)
66 (54) 56 (46)
53 (80) 37 (66)
10 (8) 112 (92)
8 (80) 82 (73)
18 (15) 104 (85)
15 (83) 75 (72)
69 (57) 53 (43)
47 (68) 43 (81)
84 (69) 38 (31)
59 (70) 31 (82)
63 (52) 59 (48)
51 (81) 39 (66)
*In first-degree relative. wIncludes torticollis, knee hyperextension, femoral anteversion, oligohydramnios, and twin pregnancy. zIncreased subluxation of femoral head from baseline present.
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utilized a qualitative classification system to characterize hip instability on dynamic ultrasound examination.17 Hips with minor instability demonstrated a gap between the femoral head and the acetabulum. In contrast, hips with major instability had increased subluxation or lateralization of the femoral head from baseline. Hips with both minor and major instability concentrically reduced into the acetabulum after removal of the stress. Affected hips were divided into 2 groups according to whether or not they spontaneously stabilized. We analyzed potential factors for their ability to independently predict spontaneous stabilization using a logistic regression model with backward likelihood ratio method. After identified confounders were entered into the model, criterion for elimination was P > 0.10. Results were provided in the form of a P-value, odds ratio, and 95% confidence interval. A 2-tailed P < 0.05 was considered significant. Statistical analysis was performed with the SPSS processor version 20.0 (SPSS, Chicago, IL).
RESULTS The study group consisted of 122 hips (79 infants) with clinically stable examination results but detectable instability on dynamic ultrasound evaluation. Of the 122 hips, 90 (74%) spontaneously stabilized at a mean age of 9 weeks (range, 4 to 18 wk). Of these 90 hips, however, 9 (10%) had persistent acetabular dysplasia on the followup ultrasound despite the resolution of their sonographic instability and were therefore treated with a Pavlik harness. Five of these hips were breech. Complete normalization, that is spontaneous stabilization with no sonographic evidence for acetabular dysplasia, occurred in 81 of the 122 hips (66%). The 32 hips (26%) that did not spontaneously stabilize were treated in a Pavlik harness for persistence of sonographic instability. Figure 1 illustrates the outcomes of all clinically normal but sonographically unstable hips. Fifty-four percent of the hips in this series were from infants who presented breech, and spontaneous stabilization occurred in 80% of these hips in comparison with 66% of nonbreech hips (Table 1). We also found differences in the rate of spontaneous stabilization based on the side involved (right, 81% vs. left, 68%), bilateralism (unilateral, 82% vs. bilateral, 70%), and grade of sonographic instability (minor, 81% vs. major, 66%). A logistic regression analysis was performed to identify independent predictors of spontaneous hip stabilization (Table 2). The analysis determined that breech presentation was a significant independent predictor for spontaneous stabilization (odds ratio, 3.72; 95% confidence interval, 1.45-9.60; P = 0.006). Although not statistically significant, there was a trend toward spontaneous stabilization in a hip affected on the right side, without contralateral involvement, or having sonographic instability without subluxation of the femoral head. Male sex, absence of intrauterine positioning syndromes, and negative family history were not predictors of spontaneous hip stabilization. r
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% of Hips (n=122)
60 50 40 30 20 10 0 Normalized
Stable but dysplastic
Persistently unstable
FIGURE 1. Sonographic outcome of untreated mildly unstable hips of DDH infants: 66% (81 hips) completely normalized (stable and no acetabular dysplasia); 7% (9 hips) stabilized but had persistent acetabular dysplasia requiring a Pavlik harness treatment; 26% (32 hips) demonstrated persistent instability necessitating treatment with a Pavlik harness.
DISCUSSION The natural history of untreated, DDH instability in newborns is variable and remains poorly understood. Clinically unstable hips in newborns may stabilize after birth, develop subluxation or complete dislocation, or remain located but retain features of femoral or acetabular dysplasia.7,18–20 For those hips with mild ultrasonographic instability, little data exists to predict which hips will normalize, remain dysplastic, or require treatment in the future. Although the risk of adverse effects with a device like the Pavlik harness is low, overtreatment can lead to occasional complications and unnecessary parental anxiety.21,22 In 1962, Barlow18 reported that >60% of unstable hips stabilize during the first weeks of life, and 88% stabilize during the first 2 months, without treatment. Dunn4 also estimated that 80% of unstable hips would resolve without treatment in the first year of life. In a randomized controlled trial, Gardiner and Dunn22 investigated the possibility of delaying the treatment of clinically dislocatable rather than dislocated hips in newborns to allow for spontaneous resolution. Within 2 weeks of neonatal diagnosis, 71% of untreated infants demonstrated spontaneous clinical and sonographic recovery. Furthermore, at 6- and 12-month follow-ups, clinical outcome did not differ between infants immediately treated and those left untreated. The authors concluded that careful sonographic surveillance for 2 weeks after birth substantially
Spontaneous Stabilization of DDH in Breech Infants
reduces the number of infants needing treatment without prejudice of final outcome. Additional evidence exists to support clinically normal but sonographically unstable infant hips spontaneously stabilizing or normalizing entirely during early infancy. Reikeras et al23 conducted a comparative study of 2- to 4-week-old infants. The first series of 27 infants (41 hips) were treated with an abduction harness for 16 weeks. The second series of 28 infants (44 hips) were left untreated. At the end of a 4-month follow-up period, all hips in both groups were found to be normal on ultrasonographic and radiographic evaluations. Holen et al24 reported 117 of 130 infants (90%) normalizing without treatment at 4 to 5 months of age. Similarly, Castelein et al25 identified 43 hips that subsequently demonstrated no residual clinical or ultrasound instability with normal pelvic radiographs at an average age of 8 months. In another study, Rosendahl et al17 found only 38 of 69 untreated hips (55%) to normalize spontaneously by routine radiography at 4 to 6 months of age. Of the remaining 31 hips, 17 were treated as they were found to be pathologically unstable or dislocatable on repeat clinical examinations. However, the other 14 hips did not necessarily fail to normalize. Rather, they were treated due to a pathologic contralateral hip, and the overall rate of spontaneous normalization may have been lowered consequently. In the present study, we retrospectively reviewed the outcome of affected hips in infants with clinically stable examinations but detectable sonographic instability. Our results demonstrated a 74% rate of spontaneous stabilization (with or without persistent dysplasia). Similar to previous reports, a relatively high rate of complete normalization of both sonographic instability and dysplasia occurred (66% of hips). We also attempted to identify independent predictors of spontaneous hip stabilization by using a logistic regression model. To the best of our knowledge, few studies have tried to elucidate the relationship between perinatal risk factors and hip stabilization or normalization. Gardiner and Dunn22 attempted to predict which untreated infants at birth would later require intervention, but their retrospective analysis based on sex, first-born child, breech presentation, mean gestational age, and family history in a first-degree relative failed to demonstrate significant predictive factors. Their findings did, however, suggest a trend toward bilaterally
TABLE 2. Logistic Regression Analysis 95% Confidence Intervals Breech presentation Right side involved Unilateral hip Minor sonographic instabilityw
Odds Ratio
Lower
Upper
P
3.725 2.402 2.869 2.255
1.446 0.936 0.990 0.929
9.597 6.166 8.313 5.474
0.006* 0.068 0.052 0.072
*Statistically significant. wGap between femoral head and acetabulum but no subluxation.
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affected hips requiring more frequent treatment, which our results showed as well. In our analysis, we confirmed our hypothesis that breech presentation is a significant independent predictor of spontaneous hip stabilization in clinically normal but sonographically unstable infant hips. The odds of spontaneous laxity resolution in a breech-presenting infant are 3.72 times the odds of spontaneous laxity resolution in an infant with a genetic or tissue-related cause of DDH. These findings indicate that DDH infants with the risk factor of breech presentation have a predisposition toward stabilizing their hip instability without treatment during early infancy, when the mechanical forces straining their hips in the intrauterine environment are no longer present. None of the other factors analyzed in our regression model independently predicted spontaneous stabilization. The clinical value of this study is in providing reassurance to the provider and family that immediate treatment with a harness may not be necessary for infants who have been in breech presentation, when clinical examination reveals stable hips but ultrasound detects instability. There are certain limitations of this study. First, we did not have long-term follow-up of infants in our study group. We followed infants until ultrasonographic instability spontaneously resolved or persisted to the point requiring intervention. For most patients in our cohort, spontaneous stabilization of the hips occurred at 2 to 4 months of age. Despite a high overall prevalence of spontaneous resolution of ultrasound instability (74%), acetabular dysplasia persisted in 10% of these hips necessitating treatment. Consequently, spontaneous ultrasonographic stabilization may not predict the future development of a hip without dysplasia. Importantly, 56% of sonographically stable but dysplastic hips (5 of 9) had been in breech presentation. Imrie et al26 also recently reported that 29% of breech infants with normal dynamic ultrasounds of the hip demonstrate subsequent dysplasia on radiographic follow-up at 4 to 6 months of age requiring treatment. Because of the implications associated with residual dysplasia, close longitudinal observation of infants after normal clinical and ultrasound examinations, particularly those with breech presentation, has been recommended.26 It is our practice to perform followup pelvic radiographs at approximately 6 months of age to monitor for residual acetabular dysplasia in infants with risk factors for DDH even after spontaneous hip stabilization or normalization. Second, we chose to include infants between birth and 4 weeks of age, in whom acetabular immaturity and not true DDH may have been the source of ultrasonographic instability.27 Yet, many of these infants still undergo a dynamic ultrasound evaluation during this age despite a normal hip examination because of high suspicion of instability or dysplasia, typically in the presence of DDH risk factors. Therefore, we believe that the group of infants from birth to 4 weeks of age is appropriate to include for the overall clinical importance of this study in guiding parental counseling and early care of DDH.
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Third, our study is subject to the inherent drawbacks of a retrospective design, and a larger sample size of clinically normal but sonographically unstable hips may have revealed additional independent predictors of spontaneous stabilization aside from breech presentation. Our results showed a trend toward spontaneous resolution of instability in hips affected on the right, without contralateral involvement, or having sonographic instability without femoral head subluxation. In conclusion, our findings confirm that a clinically stable hip demonstrating ultrasonographic instability in a breech infant is 3.72 times more likely to spontaneously stabilize than the equally lax hip in a nonbreech infant. Breech presentation is a strong independent predictor for spontaneous stabilization and expectant management of the instability may have a role in these patients. A conservative approach to management of sonographic instability in the otherwise normal breech-presenting infant may reduce unnecessary treatment and associated parental apprehension. However, the future development of a normal hip without dysplasia may not be predictable following spontaneous stabilization. As the risk of residual acetabular dysplasia and its complications after spontaneous stabilization remain significant, further radiographic follow-up may be required for this patient population. REFERENCES 1. de Hundt M, Vlemmix F, Bais JM, et al. Risk factors for developmental dysplasia of the hip: a meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2012;165:8–17. 2. Ortiz-Neira CL, Paolucci EO, Donnon T. A meta-analysis of common risk factors associated with the diagnosis of developmental dysplasia of the hip in newborns. Eur J Radiol. 2012;81:e344–e351. 3. Dunn PM. The anatomy and pathology of congenital dislocation of the hip. Clin Orthop Relat Res. 1976;119:23–27. 4. Dunn PM. Perinatal observations on the etiology of congenital dislocation of the hip. Clin Orthop Relat Res. 1976;119:11–22. 5. Weiner DS. Congenital dislocation of the hip associated with congenital muscular torticollis. Clin Orthop Relat Res. 1976;121: 163–165. 6. Kumar SJ, MacEwen GD. The incidence of hip dysplasia with metatarsus adductus. Clin Orthop Relat Res. 1982;164:234–235. 7. Coleman SS. Congenital dysplasia of the hip in the Navajo infant. Clin Orthop Relat Res. 1968;56:179–193. 8. Carter C, Wilkinson J. Persistent joint laxity and congenital dislocation of the hip. J Bone Joint Surg Br. 1964;46:40–45. 9. Dunn PM. Congenital dislocation of the hip (CDH): necropsy studies at birth. Proc R Soc Med. 1969;62:1035–1037. 10. Carter CO, Wilkinson JA. Genetic and environmental factors in the etiology of congenital dislocation of the hip. Clin Orthop Relat Res. 1964;33:119–128. 11. Salter RB. Etiology, pathogenesis and possible prevention of congenital dislocation of the hip. Can Med Assoc J. 1968;98:933–945. 12. Clausen I, Nielsen KT. Breech position, delivery route and congenital hip dislocation. Acta Obstet Gynecol Scand. 1988;67: 595–597. 13. Suzuki S, Yamamuro T. Correlation of fetal posture and congenital dislocation of the hip. Acta Orthop Scand. 1986;57:81–84. 14. Andersson JE, Oden A. The breech presentation and the vertex presentation following an external version represent risk factors for neonatal hip instability. Acta Paediatr. 2001;90:895–898. 15. Fernandez GJ, Albinana CJ. Obturator dislocation in developmental dislocation of the hip: a complication during treatment. J Pediatr Orthop B. 1996;5:129–131. r
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16. Lee CB, Mata-Fink A, Millis MB, et al. Demographic differences in adolescent-diagnosed and adult-diagnosed acetabular dysplasia compared with infantile developmental dysplasia of the hip. J Pediatr Orthop. 2013;33:107–111. 17. Rosendahl K, Markestad T, Lie RT. Ultrasound in the early diagnosis of congenital dislocation of the hip: the significance of hip stability versus acetabular morphology. Pediatr Radiol. 1992;22: 430–433. 18. Barlow T. Early diagnosis and treatment of congenital dislocation of the hip. J Bone Joint Surg Br. 1962;44:292–301. 19. Yamamuro T, Doi H. Diagnosis and treatment of congenital dislocation of the hip in newborns. J Jpn Orthop Assoc. 1965;39:492. 20. Pratt WB, Freiberger RH, Arnold WD. Untreated congenital hip dysplasia in the Navajo. Clin Orthop. 1982;162:69–77. 21. Weinstein SL, Mubarak SJ, Wenger DR. Developmental hip dysplasia and dislocation: part I. Instr Course Lect. 2004;53:523–530.
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22. Gardiner HM, Dunn PM. Controlled trial of immediate splinting versus ultrasonographic surveillance in congenitally dislocatable hips. Lancet. 1990;336:1553–1556. 23. Reikeras O, Kristiansen LP, Gunderson R. Ultrasonography of the infant hip: the significance of provokable instability with normal morphology. Orthopedics. 2002;25:833–835. 24. Holen KJ, Terjesen T, Tegnander A, et al. Ultrasound screening for hip dysplasia in newborns. J Pediatr Orthop. 1994;14:667–673. 25. Castelein RM, Sauter AJ, de Vlieger M, et al. Natural history of ultrasound hip abnormalities in clinically normal newborns. J Pediatr Orthop. 1992;12:423–427. 26. Imrie M, Scott V, Stearns P, et al. Is ultrasound screening for DDH in babies born breech sufficient? J Child Orthop. 2010;4:3–8. 27. Sucato DJ, Johnston CE II, Birch JG, et al. Outcome of ultrasonographic hip abnormalities in clinically stable hips. J Pediatr Orthop. 1999;19:754–759.
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Is There a Predilection for Breech Infants to Demonstrate Spontaneous Stabilization of DDH Instability? Eric J. Sarkissian, BS, Wudbhav N. Sankar, MD, Keith Baldwin, MD, MSPT, MPH, and John M. Flynn, MD
Background: Breech position subjects the fetal hip to abnormal mechanical forces. However, unlike genetic or tissue factors linked to developmental dysplasia of the hip (DDH), the causative effect of the breech position ends when the infant is born. The purpose of this study was to evaluate the rate of spontaneous stabilization in mildly unstable hips of breech-presenting infants compared with similarly lax hips in infants with a genetic or tissue-related cause of DDH. Methods: We studied a consecutive series of infants presenting to our institution at 8 weeks of age or younger with DDH from January 2008 to January 2012. Infants with increased hip laxity on dynamic ultrasound examination but without frank instability on clinical provocation maneuvers and no history of prior treatment were evaluated. The endpoint was spontaneous stabilization of ultrasound-detected instability, or intervention due to persistent instability on follow-up dynamic ultrasound. A logistic regression model using backward likelihood ratio method was used to analyze predictors of spontaneous stabilization. Results: We identified 122 hips in 79 infants with instability on dynamic ultrasound evaluation but with stable clinical examinations. Spontaneous stabilization of sonographic instability occurred in 90 hips (74%) at a mean age of 9 weeks (range, 4 to 18 wk). Breech hips more frequently spontaneously stabilized compared with nonbreech hips (80% vs. 66%). Regression analysis determined that breech presentation was a strong independent predictor for spontaneous hip stabilization (odds ratio, 3.72; 95% confidence interval, 1.45-9.60; P = 0.006). Sex, family history, intrauterine positioning syndromes, side involved, bilateralism, and grade of sonographic hip instability were not independently predictive of spontaneous hip stabilization. Conclusions: DDH infants with a history of breech presentation are 3.72 times more likely to experience spontaneous resolution of mild hip instability compared with nonbreech infants. Awareness that breech presentation is a strong independent predictor of spontaneous laxity resolution can guide parental counseling and early care of DDH. Level of Evidence: Level II, prognostic retrospective study.
From the The Children’s Hospital of Philadelphia, Philadelphia, PA. The authors declare no conflict of interest. Reprints: John M. Flynn, MD, The Children’s Hospital of Philadelphia Wood Building, 2nd Floor, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104. E-mail: fl[email protected]. Copyright r 2014 by Lippincott Williams & Wilkins
J Pediatr Orthop
Volume 34, Number 5, July/August 2014
Key Words: developmental dysplasia of the hip, breech presentation, ultrasound (J Pediatr Orthop 2014;34:509–513)
T
he etiology of developmental dysplasia of the hip (DDH) is multifactorial with both hereditary and environmental contributions acting as internal and external influences, respectively. Breech presentation, female sex, positive family history, first-born children, and left hip affected are commonly associated with DDH.1,2 Additional factors include intrauterine positioning syndromes (torticollis, metatarsus adductus, femoral anteversion, genu recurvatum, oligohydramnios, and twin pregnancy),3–6 swaddling,7 and hip capsular laxity.8,9 Of all factors linked to DDH, breech presentation may be the most critical. The reported frequency of breech presentation in DDH is between 17% and 23%.10–12 Prolonged flexion of the hip joint with knee extension pulls the femoral head downward and stretches the hip joint capsule, predisposing to hip instability, acetabular dysplasia, or both.13,14 However, the abnormal mechanical forces placed on the fetal hip by breech presentation end at birth. In contrast, genetic factors or tissue-related etiological factors may affect the individual beyond infancy into childhood, adolescence, and adulthood.8,15,16 Therefore, we hypothesize that after birth, the hips of breech-presenting infants with mild instability are more likely to stabilize without treatment in comparison with similarly lax hips in infants with a genetic or tissuerelated cause of DDH. The purpose of this study was to determine factors predictive of spontaneous stabilization, particularly breech presentation.
METHODS We studied infants presenting to our institution with DDH between January 2008 and January 2012 after obtaining approval from our institutional review board. We performed a retrospective chart review of 398 consecutive patients identified by ICD-9 codes for congenital dislocation of the hip, hip dysplasia, hip click, and hip laxity presenting at 8 weeks of age or younger with adequate documentation of clinical course. Inclusion criteria were infants with increased hip laxity on dynamic ultrasound examination and no history of prior treatment. Infants www.pedorthopaedics.com |
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with frank hip instability on clinical examination (positive Barlow or Ortolani maneuvers) were excluded, as they required immediate treatment with a Pavlik harness. Infants with a syndromal or neuromuscular disorder predisposing to DDH were excluded as well. All infants were examined by a fellowship-trained pediatric orthopaedic surgeon. All ultrasounds were performed by an experienced ultrasonographer to evaluate hip stability and acetabular morphology (normal: a–angle Z60 degrees) using the modified Graf method developed by Rosendahl et al.17 Infants were reevaluated at approximately 1 month after the initial visit with both an ultrasound and clinical examination to determine the progression or resolution of their ultrasonographic instability. The endpoint of the study was spontaneous stabilization of sonographic hip instability, or intervention due to persistent instability on follow-up dynamic ultrasound. After applying our inclusion and exclusion criteria, we identified 79 consecutive patients suitable for investigation. Bilaterally affected hips were treated separately for the purpose of this study. The presence or absence of known DDH risk factors were recorded from the medical records, particularly female sex, breech presentation, positive family history (in first-degree relative), left hip affected, and intrauterine positioning syndromes (torticollis, knee hyperextension, femoral anteversion, oligohydramnios, and twin pregnancy) (Table 1). We also TABLE 1. Demographics of Study Group and Proportion Demonstrating Spontaneous Stabilization n (%) Clinically Normal/ Sonographically Unstable Hips (n = 122) Sex Female Male Presentation Breech Nonbreech Family history Positive* Negative Intrauterine positioning syndromes Presentw Absent Side involved Left Right Bilateralism Bilateral Unilateral Grade of sonographic instability Minor Majorz
Spontaneously Stabilizing (n = 90)
98 (80) 24 (20)
72 (73) 18 (75)
66 (54) 56 (46)
53 (80) 37 (66)
10 (8) 112 (92)
8 (80) 82 (73)
18 (15) 104 (85)
15 (83) 75 (72)
69 (57) 53 (43)
47 (68) 43 (81)
84 (69) 38 (31)
59 (70) 31 (82)
63 (52) 59 (48)
51 (81) 39 (66)
*In first-degree relative. wIncludes torticollis, knee hyperextension, femoral anteversion, oligohydramnios, and twin pregnancy. zIncreased subluxation of femoral head from baseline present.
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utilized a qualitative classification system to characterize hip instability on dynamic ultrasound examination.17 Hips with minor instability demonstrated a gap between the femoral head and the acetabulum. In contrast, hips with major instability had increased subluxation or lateralization of the femoral head from baseline. Hips with both minor and major instability concentrically reduced into the acetabulum after removal of the stress. Affected hips were divided into 2 groups according to whether or not they spontaneously stabilized. We analyzed potential factors for their ability to independently predict spontaneous stabilization using a logistic regression model with backward likelihood ratio method. After identified confounders were entered into the model, criterion for elimination was P > 0.10. Results were provided in the form of a P-value, odds ratio, and 95% confidence interval. A 2-tailed P < 0.05 was considered significant. Statistical analysis was performed with the SPSS processor version 20.0 (SPSS, Chicago, IL).
RESULTS The study group consisted of 122 hips (79 infants) with clinically stable examination results but detectable instability on dynamic ultrasound evaluation. Of the 122 hips, 90 (74%) spontaneously stabilized at a mean age of 9 weeks (range, 4 to 18 wk). Of these 90 hips, however, 9 (10%) had persistent acetabular dysplasia on the followup ultrasound despite the resolution of their sonographic instability and were therefore treated with a Pavlik harness. Five of these hips were breech. Complete normalization, that is spontaneous stabilization with no sonographic evidence for acetabular dysplasia, occurred in 81 of the 122 hips (66%). The 32 hips (26%) that did not spontaneously stabilize were treated in a Pavlik harness for persistence of sonographic instability. Figure 1 illustrates the outcomes of all clinically normal but sonographically unstable hips. Fifty-four percent of the hips in this series were from infants who presented breech, and spontaneous stabilization occurred in 80% of these hips in comparison with 66% of nonbreech hips (Table 1). We also found differences in the rate of spontaneous stabilization based on the side involved (right, 81% vs. left, 68%), bilateralism (unilateral, 82% vs. bilateral, 70%), and grade of sonographic instability (minor, 81% vs. major, 66%). A logistic regression analysis was performed to identify independent predictors of spontaneous hip stabilization (Table 2). The analysis determined that breech presentation was a significant independent predictor for spontaneous stabilization (odds ratio, 3.72; 95% confidence interval, 1.45-9.60; P = 0.006). Although not statistically significant, there was a trend toward spontaneous stabilization in a hip affected on the right side, without contralateral involvement, or having sonographic instability without subluxation of the femoral head. Male sex, absence of intrauterine positioning syndromes, and negative family history were not predictors of spontaneous hip stabilization. r
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% of Hips (n=122)
60 50 40 30 20 10 0 Normalized
Stable but dysplastic
Persistently unstable
FIGURE 1. Sonographic outcome of untreated mildly unstable hips of DDH infants: 66% (81 hips) completely normalized (stable and no acetabular dysplasia); 7% (9 hips) stabilized but had persistent acetabular dysplasia requiring a Pavlik harness treatment; 26% (32 hips) demonstrated persistent instability necessitating treatment with a Pavlik harness.
DISCUSSION The natural history of untreated, DDH instability in newborns is variable and remains poorly understood. Clinically unstable hips in newborns may stabilize after birth, develop subluxation or complete dislocation, or remain located but retain features of femoral or acetabular dysplasia.7,18–20 For those hips with mild ultrasonographic instability, little data exists to predict which hips will normalize, remain dysplastic, or require treatment in the future. Although the risk of adverse effects with a device like the Pavlik harness is low, overtreatment can lead to occasional complications and unnecessary parental anxiety.21,22 In 1962, Barlow18 reported that >60% of unstable hips stabilize during the first weeks of life, and 88% stabilize during the first 2 months, without treatment. Dunn4 also estimated that 80% of unstable hips would resolve without treatment in the first year of life. In a randomized controlled trial, Gardiner and Dunn22 investigated the possibility of delaying the treatment of clinically dislocatable rather than dislocated hips in newborns to allow for spontaneous resolution. Within 2 weeks of neonatal diagnosis, 71% of untreated infants demonstrated spontaneous clinical and sonographic recovery. Furthermore, at 6- and 12-month follow-ups, clinical outcome did not differ between infants immediately treated and those left untreated. The authors concluded that careful sonographic surveillance for 2 weeks after birth substantially
Spontaneous Stabilization of DDH in Breech Infants
reduces the number of infants needing treatment without prejudice of final outcome. Additional evidence exists to support clinically normal but sonographically unstable infant hips spontaneously stabilizing or normalizing entirely during early infancy. Reikeras et al23 conducted a comparative study of 2- to 4-week-old infants. The first series of 27 infants (41 hips) were treated with an abduction harness for 16 weeks. The second series of 28 infants (44 hips) were left untreated. At the end of a 4-month follow-up period, all hips in both groups were found to be normal on ultrasonographic and radiographic evaluations. Holen et al24 reported 117 of 130 infants (90%) normalizing without treatment at 4 to 5 months of age. Similarly, Castelein et al25 identified 43 hips that subsequently demonstrated no residual clinical or ultrasound instability with normal pelvic radiographs at an average age of 8 months. In another study, Rosendahl et al17 found only 38 of 69 untreated hips (55%) to normalize spontaneously by routine radiography at 4 to 6 months of age. Of the remaining 31 hips, 17 were treated as they were found to be pathologically unstable or dislocatable on repeat clinical examinations. However, the other 14 hips did not necessarily fail to normalize. Rather, they were treated due to a pathologic contralateral hip, and the overall rate of spontaneous normalization may have been lowered consequently. In the present study, we retrospectively reviewed the outcome of affected hips in infants with clinically stable examinations but detectable sonographic instability. Our results demonstrated a 74% rate of spontaneous stabilization (with or without persistent dysplasia). Similar to previous reports, a relatively high rate of complete normalization of both sonographic instability and dysplasia occurred (66% of hips). We also attempted to identify independent predictors of spontaneous hip stabilization by using a logistic regression model. To the best of our knowledge, few studies have tried to elucidate the relationship between perinatal risk factors and hip stabilization or normalization. Gardiner and Dunn22 attempted to predict which untreated infants at birth would later require intervention, but their retrospective analysis based on sex, first-born child, breech presentation, mean gestational age, and family history in a first-degree relative failed to demonstrate significant predictive factors. Their findings did, however, suggest a trend toward bilaterally
TABLE 2. Logistic Regression Analysis 95% Confidence Intervals Breech presentation Right side involved Unilateral hip Minor sonographic instabilityw
Odds Ratio
Lower
Upper
P
3.725 2.402 2.869 2.255
1.446 0.936 0.990 0.929
9.597 6.166 8.313 5.474
0.006* 0.068 0.052 0.072
*Statistically significant. wGap between femoral head and acetabulum but no subluxation.
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affected hips requiring more frequent treatment, which our results showed as well. In our analysis, we confirmed our hypothesis that breech presentation is a significant independent predictor of spontaneous hip stabilization in clinically normal but sonographically unstable infant hips. The odds of spontaneous laxity resolution in a breech-presenting infant are 3.72 times the odds of spontaneous laxity resolution in an infant with a genetic or tissue-related cause of DDH. These findings indicate that DDH infants with the risk factor of breech presentation have a predisposition toward stabilizing their hip instability without treatment during early infancy, when the mechanical forces straining their hips in the intrauterine environment are no longer present. None of the other factors analyzed in our regression model independently predicted spontaneous stabilization. The clinical value of this study is in providing reassurance to the provider and family that immediate treatment with a harness may not be necessary for infants who have been in breech presentation, when clinical examination reveals stable hips but ultrasound detects instability. There are certain limitations of this study. First, we did not have long-term follow-up of infants in our study group. We followed infants until ultrasonographic instability spontaneously resolved or persisted to the point requiring intervention. For most patients in our cohort, spontaneous stabilization of the hips occurred at 2 to 4 months of age. Despite a high overall prevalence of spontaneous resolution of ultrasound instability (74%), acetabular dysplasia persisted in 10% of these hips necessitating treatment. Consequently, spontaneous ultrasonographic stabilization may not predict the future development of a hip without dysplasia. Importantly, 56% of sonographically stable but dysplastic hips (5 of 9) had been in breech presentation. Imrie et al26 also recently reported that 29% of breech infants with normal dynamic ultrasounds of the hip demonstrate subsequent dysplasia on radiographic follow-up at 4 to 6 months of age requiring treatment. Because of the implications associated with residual dysplasia, close longitudinal observation of infants after normal clinical and ultrasound examinations, particularly those with breech presentation, has been recommended.26 It is our practice to perform followup pelvic radiographs at approximately 6 months of age to monitor for residual acetabular dysplasia in infants with risk factors for DDH even after spontaneous hip stabilization or normalization. Second, we chose to include infants between birth and 4 weeks of age, in whom acetabular immaturity and not true DDH may have been the source of ultrasonographic instability.27 Yet, many of these infants still undergo a dynamic ultrasound evaluation during this age despite a normal hip examination because of high suspicion of instability or dysplasia, typically in the presence of DDH risk factors. Therefore, we believe that the group of infants from birth to 4 weeks of age is appropriate to include for the overall clinical importance of this study in guiding parental counseling and early care of DDH.
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Third, our study is subject to the inherent drawbacks of a retrospective design, and a larger sample size of clinically normal but sonographically unstable hips may have revealed additional independent predictors of spontaneous stabilization aside from breech presentation. Our results showed a trend toward spontaneous resolution of instability in hips affected on the right, without contralateral involvement, or having sonographic instability without femoral head subluxation. In conclusion, our findings confirm that a clinically stable hip demonstrating ultrasonographic instability in a breech infant is 3.72 times more likely to spontaneously stabilize than the equally lax hip in a nonbreech infant. Breech presentation is a strong independent predictor for spontaneous stabilization and expectant management of the instability may have a role in these patients. A conservative approach to management of sonographic instability in the otherwise normal breech-presenting infant may reduce unnecessary treatment and associated parental apprehension. However, the future development of a normal hip without dysplasia may not be predictable following spontaneous stabilization. As the risk of residual acetabular dysplasia and its complications after spontaneous stabilization remain significant, further radiographic follow-up may be required for this patient population. REFERENCES 1. de Hundt M, Vlemmix F, Bais JM, et al. Risk factors for developmental dysplasia of the hip: a meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2012;165:8–17. 2. Ortiz-Neira CL, Paolucci EO, Donnon T. A meta-analysis of common risk factors associated with the diagnosis of developmental dysplasia of the hip in newborns. Eur J Radiol. 2012;81:e344–e351. 3. Dunn PM. The anatomy and pathology of congenital dislocation of the hip. Clin Orthop Relat Res. 1976;119:23–27. 4. Dunn PM. Perinatal observations on the etiology of congenital dislocation of the hip. Clin Orthop Relat Res. 1976;119:11–22. 5. Weiner DS. Congenital dislocation of the hip associated with congenital muscular torticollis. Clin Orthop Relat Res. 1976;121: 163–165. 6. Kumar SJ, MacEwen GD. The incidence of hip dysplasia with metatarsus adductus. Clin Orthop Relat Res. 1982;164:234–235. 7. Coleman SS. Congenital dysplasia of the hip in the Navajo infant. Clin Orthop Relat Res. 1968;56:179–193. 8. Carter C, Wilkinson J. Persistent joint laxity and congenital dislocation of the hip. J Bone Joint Surg Br. 1964;46:40–45. 9. Dunn PM. Congenital dislocation of the hip (CDH): necropsy studies at birth. Proc R Soc Med. 1969;62:1035–1037. 10. Carter CO, Wilkinson JA. Genetic and environmental factors in the etiology of congenital dislocation of the hip. Clin Orthop Relat Res. 1964;33:119–128. 11. Salter RB. Etiology, pathogenesis and possible prevention of congenital dislocation of the hip. Can Med Assoc J. 1968;98:933–945. 12. Clausen I, Nielsen KT. Breech position, delivery route and congenital hip dislocation. Acta Obstet Gynecol Scand. 1988;67: 595–597. 13. Suzuki S, Yamamuro T. Correlation of fetal posture and congenital dislocation of the hip. Acta Orthop Scand. 1986;57:81–84. 14. Andersson JE, Oden A. The breech presentation and the vertex presentation following an external version represent risk factors for neonatal hip instability. Acta Paediatr. 2001;90:895–898. 15. Fernandez GJ, Albinana CJ. Obturator dislocation in developmental dislocation of the hip: a complication during treatment. J Pediatr Orthop B. 1996;5:129–131. r
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16. Lee CB, Mata-Fink A, Millis MB, et al. Demographic differences in adolescent-diagnosed and adult-diagnosed acetabular dysplasia compared with infantile developmental dysplasia of the hip. J Pediatr Orthop. 2013;33:107–111. 17. Rosendahl K, Markestad T, Lie RT. Ultrasound in the early diagnosis of congenital dislocation of the hip: the significance of hip stability versus acetabular morphology. Pediatr Radiol. 1992;22: 430–433. 18. Barlow T. Early diagnosis and treatment of congenital dislocation of the hip. J Bone Joint Surg Br. 1962;44:292–301. 19. Yamamuro T, Doi H. Diagnosis and treatment of congenital dislocation of the hip in newborns. J Jpn Orthop Assoc. 1965;39:492. 20. Pratt WB, Freiberger RH, Arnold WD. Untreated congenital hip dysplasia in the Navajo. Clin Orthop. 1982;162:69–77. 21. Weinstein SL, Mubarak SJ, Wenger DR. Developmental hip dysplasia and dislocation: part I. Instr Course Lect. 2004;53:523–530.
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