Outcomes of Open Reduction for Developmental Dysplasia of the Hip

1081 C OPYRIGHT Ó 2013

BY

T HE J OURNAL

OF

B ONE

AND J OINT

S URGERY, I NCORPORATED

Outcomes of Open Reduction for Developmental Dysplasia of the Hip: Does Bilateral Dysplasia Have a Poorer Outcome? Ting-Ming Wang, MD, PhD, Kuan-Wen Wu, MD, Shu-Fang Shih, MBA, MSc, PhD, Shier-Chieg Huang, MD, PhD, and Ken N. Kuo, MD Investigation performed at the National Taiwan University Hospital, Taipei, Taiwan

Background: The purpose of this study was to compare the outcomes of surgical treatment in children of walking age with unilateral and bilateral developmental dysplasia of the hip (DDH). Methods: We examined the records of fifty-six children of walking age with bilateral dysplasia and 156 children of walking age with unilateral dysplasia treated with open reduction and pelvic osteotomy with or without femoral osteotomy from 1990 to 2000. The minimum duration of follow-up was five years. The mean age at surgery was thirty-four months in the bilateral group and twenty-five months in the unilateral group. Preoperative radiographs were evaluated to determine the Tönnis grade of the dislocation and the acetabular index, and the latest radiographs were evaluated to determine the Severin classification. The Kalamchi and MacEwen classification was used to assess osteonecrosis, and the McKay classification was used to assess the clinical outcome at the time of the latest follow-up. For the statistical analyses, we selected the worse side in patients in the bilateral group as the index hip if the outcome was asymmetrical and the left hip if the outcome was symmetrical. The Fisher exact and Student t tests were used for comparisons of outcomes between the groups. Multiple logistic regression models were used to analyze factors associated with osteonecrosis and with the McKay classification. Results: Age at surgery and preoperative Tönnis grade differed significantly between the groups. Forty-five (80.3%) of the patients in the bilateral group and 135 (86.5%) of the patients in the unilateral group had a satisfactory Severin classification (Ia, Ib, or II); the difference between the groups was not significant. According to the McKay classification, twentysix (46%) of the patients in the bilateral group had an satisfactory outcome compared with 111 (71%) of the patients in the unilateral group (p = 0.006). Osteonecrosis was significantly greater in the bilateral group as well (p = 0.01). Patient age at surgery and Tönnis grade were risk factors for osteonecrosis. Older age and bilaterality were associated with a poorer McKay classification. The logistic regression analysis was repeated after removing the nineteen patients (34%) in the bilateral group who had an asymmetrical outcome, and this analysis confirmed that asymmetrical outcome was a risk factor for a poorer McKay classification. Conclusions: Our data confirmed that the clinical outcome of bilateral developmental dysplasia of the hip was worse primarily because of asymmetrical outcomes. Age and Tönnis grade played an important role in the risk of occurrence of osteonecrosis. The radiographic outcome according to the Severin classification did not differ significantly between the groups. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

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reatment of children with bilateral developmental dysplasia of the hip (DDH) remains a challenge. Some authors believe that patients with bilateral dysplasia

tend to have a poorer prognosis because of the frequent delay in diagnosis and greater treatment requirements1-3. Although one-stage treatment is feasible for late-diagnosed dysplasia, the

Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

J Bone Joint Surg Am. 2013;95:1081-6

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http://dx.doi.org/10.2106/JBJS.K.01324

1082 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 95-A N U M B E R 12 J U N E 19, 2 013 d

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treatment of older children is complex, with many unpredictable problems4,5. Ryan et al.5 reported that patients with bilateral dysplasia and an older age tended to have a poor radiographic outcome. Kershaw et al. studied a group of thirtytwo patients who underwent revision surgery after an unsuccessful initial open reduction for dysplasia and reported that 63% of these patients initially had bilateral involvement6. However, the outcome of treatment in patients with bilateral dysplasia has not been fully addressed. Most authors have evaluated patients with unilateral and bilateral dysplasia together, with the resulting cohort including only a small number of patients with bilateral involvement3-5,7,8. Other authors have reported on children who underwent mixed conservative and surgical treatment in addition to evaluating those with unilateral and bilateral involvement together in a single heterogeneous cohort1. To our knowledge, a study comparing the outcome of open reduction in a large series of patients with unilateral and bilateral dysplasia has not previously been reported. The purpose of the present study was to compare the long-term outcomes of surgical treatment of unilateral and bilateral dysplasia, in children who were diagnosed after walking age. We evaluated the latest clinical and radiographic outcomes, complications, and the severity of osteonecrosis following treatment. We also analyzed the risk factors for poor outcomes and investigated the impact of asymmetrical surgical outcomes in patients with bilateral dysplasia. Materials and Methods

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his study was approved by our institutional review board. We retrospectively reviewed the medical records of patients with dysplasia who were 9 treated with one-stage open reduction and Pemberton osteotomy , combined with femoral shortening osteotomy if necessary, by one senior surgeon (S.-C.H.) from 1990 to 2000 at our institution. All patients with irreducible frank dislocation that required open reduction were included. Patients with an associated neuromuscular disorder, syndromic presentation, or residual deformity due to a previous hip infection were excluded. We identified a total of ninety-two patients with bilateral dysplasia and 236 with unilateral dysplasia. Six patients with bilateral dysplasia and four with unilateral dysplasia who were eight years or older at the time of surgery were excluded. The medical records and serial follow-up radiographs of the remaining 318 patients were reviewed. Fifty-six (65%) of the eighty-six patients with bilateral dysplasia and 156 (67%) of the 232 patients with unilateral dysplasia had a minimum of five years of clinical and radiographic follow-up and were included in the study. The mean duration of follow-up was 109 months in the bilateral group and 128 months in the unilateral group. The bilateral group consisted of two boys and fifty-four girls, whereas the unilateral group consisted of fifteen boys and 141 girls. The mean age at surgery was thirty-four months (range, fourteen to ninety-four months) in the bilateral group and twenty-five months (range, sixteen to ninety-six months) in the unilateral group. All patients underwent one-stage open reduction, capsulorrhaphy, and Pemberton osteotomy. For patients who were older than thirty-six months, we routinely included femoral shortening osteotomy to facilitate femoral head reduction and to decrease osteonecrosis. We performed femoral derotation osteotomy in those children who had excessive femoral anteversion or in order to facilitate the femoral head reduction. In patients with bilateral involvement, the hips were treated sequentially, with a six to twelve-week interval between the procedures. No 10 bracing was applied after cast removal. If the Tönnis grade of the dislocation differed between the hips in a patient with bilateral involvement, we treated the

OUTCOMES OF OPEN REDUCTION DY S P L A S I A O F T H E HI P

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hip with the greater displacement first; if the Tönnis grades were equivalent, we treated the right hip first.

Operative Technique and Postoperative Care An anterior iliofemoral surgical approach was used, and an iliopsoas tenotomy was routinely performed over the pelvic rim. The ligamentum teres was removed and the transverse acetabular ligament was released. We removed any fibro-fatty tissue in the acetabular fossa but preserved the limbus. A Pembertontype iliac osteotomy was carried out in all cases. For the older children who also had a femoral shortening osteotomy, the femur was osteotomized at the level of the subtrochanteric region through a separate lateral incision. We usually shortened the femur by 1 to 2 cm to achieve a force-free reduction. If indicated, derotation of the femur was performed simultaneously and the amount of rotation was decided intraoperatively under direct visualization. Patients were immobilized postoperatively in a bilateral hip spica cast for six weeks. No preoperative traction was used. Radiographs were reviewed by two senior authors (K.N.K. and S.-C.H.), who determined the Tönnis grade and the Kalamchi and MacEwan classification. Two junior authors (K.-W.W. and T.-M.W.) determined the acetabular index and Severin classification. The radiographs made immediately before surgery were used to evaluate the degree of hip dislocation as indicated 10 by Tönnis grading system and to measure the acetabular index. The Severin 11 classification was used to evaluate the latest radiographic outcome (see Appendix). All follow-up radiographs were evaluated for the presence of osteo12 necrosis with use of the Kalamchi and MacEwen classification (see Appendix). The latest clinical outcome was categorized according to the McKay classifi13 cation . The intraobserver reliability of the Severin classification was assessed, and the interclass correlation coefficient was found to be 0.841 (95% confidence interval, 0.739 to 0.921). The interobserver reliability was also assessed, and the interclass correlation coefficient was found to be 0.728 (95% confidence interval, 0.514 to 0.832). Postoperative complications and subsequent surgery during the follow-up period were recorded for all patients. We considered the outcome to be asymmetrical when there was more than a one-grade difference in the Severin or McKay classification between the two hips or when the limb-length discrepancy was >1 cm14.

Statistical Methods Statistical analyses were performed with use of SPSS for Windows (SPSS, Chicago, Illinois) and Stata (version 9.0; StataCorp, College Station, Texas). Demographic variables were compared between the two groups with use of the Fisher exact test for categorical data (sex, laterality, Tönnis grade) and the Student t test for continuous data (age at surgery, duration of follow-up, preoperative acetabular index). For the comparison of the latest radiographic and clinical outcomes between the two groups, we thought it logical to evaluate cases of bilateral involvement on the basis of patients instead of hips. In such cases, we selected the worse side as the index hip for the comparison if the Severin or McKay classification was asymmetrical; if the Severin or McKay classification was similar on both sides, the left side was selected because of a general preponderance of left hip involvement in the patients with unilateral dysplasia. The Fisher exact test was used to compare the Severin classification, osteonecrosis occurrence, and McKay classification between the two groups. Factors associated with osteonecrosis and the latest McKay classification were analyzed with use of multiple logistic regression models. A p value of 0.05 (twosided) was considered significant for all tests.

Source of Funding The authors received no external funding for this study.

Results ifty-six patients with bilateral dysplasia were compared with 156 patients with unilateral dysplasia; as previously described, one hip was selected in each patient with bilateral

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TABLE I Demographic Characteristics of the Study Subjects Patient Characteristic

Unilateral (N = 156)

Bilateral (N = 56)

P Value

Age at surgery* (mo)

24.91 ± 16.45

34.20 ± 20.84

0.003

Female sex (no. [%])

141 (90.4)

54 (96.4)

0.060

Left side (no. [%])

107 (68.6)

33 (59.9)

0.280

128.87 ± 41.68

109.71 ± 49.89

0.006

41.08 ± 4.79

40.63 ± 6.90

0.690

Follow-up* (mo) Preop. acetabular index* (deg)

*The values are given as the mean and standard deviation.

TABLE II Comparison of Long-Term Outcomes in the Unilateral and Bilateral Groups Unilateral (N = 156)*

Bilateral (N = 56)*

Severin class Ia Ib II III IV V VI

76 (49) 6 (4) 53 (34) 13 (8) 8 (5) 0 0

17 (30) 2 (4) 26 (46) 7 (12) 2 (4) 0 2 (4)

Kalamchi class Osteonecrosis absent I II III IV

73 (47) 23 (15) 40 (26) 4 (3) 16 (10)

15 (27) 10 (18) 21 (37) 2 (4) 8 (14)

McKay class Excellent Good Fair Poor

58 (37) 53 (34) 26 (17) 19 (12)

11 (20) 15 (27) 20 (36) 10 (18)

P Value † 0.25

0.01

0.0061

*The values are given as the number of patients, with the percentage in parentheses. †Fisher exact test.

involvement. Analysis of the demographic variables indicated that age at surgery, duration of follow-up, and Tönnis grade of the dislocation differed significantly between the groups, with the children in the bilateral group having a higher Tönnis grade and an older age (Table I). No significant differences were found with respect to sex, laterality, or preoperative acetabular index (p > 0.05). The Tönnis grade was the same in both hips in thirty-seven of the patients with bilateral involvement and different in the remaining nineteen. A comparison of the Tönnis grades in the two groups is given in the Appendix. Thirty of the patients who were lost to follow-up had bilateral involvement and seventy-six had unilateral involvement. The demographic variables (sex, laterality, age at surgery, Tönnis grade, and preoperative acetabular index) of these 106

patients did not differ significantly from those of the study cohort (p > 0.05). At the time of the latest follow-up, 135 (86.5%) of the 156 patients in the unilateral group and forty-five (80.4%) of the fifty-six patients in the bilateral group had a satisfactory radiographic outcome (Severin class Ia, Ib, or II). The difference in the Severin classification between the two groups was not significant (Table II). However, a significantly higher severity of postoperative osteonecrosis was observed in the bilateral group (p = 0.01, Table II). Sixty (38%) of the 156 patients in the unilateral group and thirty-one (55%) of the fifty-six patients in the bilateral group had osteonecrosis classified as Kalamchi class II or higher. (Class I was considered to represent a minor sequela.)


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TABLE III Association of Variables with the Development of Osteonecrosis by Multiple Logistic Regression Analysis Variable

Odds Ratio

Std. Error

P Value 0.097

Sex (ref. = female)

3.94

3.25

Age

1.04

0.02

0.003

Tönnis grade

1.55

0.32

0.031

Bilateral

1.67

0.66

0.193

Duration of follow-up

1.01

0.00

0.033

TABLE IV Association of Variables with Poorer McKay Classification by Multiple Logistic Regression Analysis Variable

Odds Ratio

Std. Error

P Value 0.297

Sex (ref. = female)

1.87

1.12

Age

1.04

0.01

0.000

Tönnis grade

1.10

0.22

0.625

Bilateral

2.35

0.88

0.022


1.01

0.00

0.113

TABLE V Association of Variables with Poorer McKay Classification by Multiple Logistic Regression Analysis After Removing Nineteen Patients with Bilateral Dysplasia and an Asymmetrical Outcome Variable Sex (ref. = female)

Odds Ratio

Std. Error

P Value

1.62

0.96

0.417

Age

1.04

0.01

0.000

Tönnis grade

1.29

0.27

0.225

Bilateral

1.15

0.51

0.758


1.00

0.00

0.662

Analysis of the functional outcome at the latest clinical evaluation revealed that 111 (71%) of the 156 patients in the unilateral group but only 46% (twenty-six) of the fifty-six in the bilateral group had a satisfactory outcome (excellent or good) according to the McKay classification. The latest clinical outcomes were significantly worse in the bilateral group (p = 0.0061, Table II). Postoperative complications included three redislocations (1.9%) in the unilateral group and four (7.1%) in the bilateral group that occurred immediately following surgery and required reoperation to reduce the hip. Seven (4.5%) of the patients in the unilateral group underwent an additional reconstructive procedure (pelvic or femoral osteotomy) during the remainder of the follow-up period because of inadequate acetabular coverage. Five of the patients in the bilateral group had one additional reconstructive procedure to maintain hip stability, and two had two such procedures. Nineteen (34%) of the fifty-six patients with bilateral dysplasia in


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our series had an asymmetrical outcome. Eleven of these nineteen patients had an equal Tönnis grade in both hips, and eight had different grades. In fourteen patients, the Tönnis grade was worse in the hip that underwent surgery first, and in the remaining five patients the outcome was worse in the second hip. Multiple logistic regression analysis was used to assess risk factors for osteonecrosis and for a poorer McKay classification. Older age at surgery (p = 0.003), higher Tönnis grade (p = 0.031), and longer duration of follow-up (p = 0.033) were significantly associated with a higher severity of osteonecrosis (Table III). Bilaterality was not a significant risk factor for osteonecrosis after adjusting for all confounding variables. However, older age at surgery (p < 0.001) and bilateral involvement (p = 0.022) were significantly associated with a poor McKay classification at the time of the latest clinical follow-up, whereas sex, Tönnis grade, and duration of follow-up were not associated with the clinical outcome (Table IV). We also performed a secondary analysis by using age-matched samples of both groups, and the results were consistent with those obtained from the multiple logistic regression analysis. In order to investigate the adverse effects of bilateral dysplasia on the McKay clinical outcome, we repeated the logistic regression analysis after removing the nineteen patients in the bilateral group who had an asymmetrical outcome. The effect of bilaterality became insignificant (Table V). This sensitivity test confirmed our hypothesis that asymmetrical outcomes were problematic in patients with bilateral involvement. Discussion n children of walking age, bilateral dysplasia presents a complex problem. It is still questionable whether patients with bilateral dysplasia actually have poorer outcomes, because most reports include unilateral and bilateral cases together3-5,7,8. In 1982, Greene and Drennan1 reported on the only comparative study of patient groups with unilateral and bilateral involvement who were part of a large series; radiographic outcomes were evaluated but function was not. The present series included a large, well-defined group of patients with unilateral and bilateral dysplasia; the patients had a wide range of ages and Tönnis grades, and the treatment protocols and the classification systems used for evaluation were uniform. In agreement with Moussa and Al-Othman14 that the outcomes in cases of bilateral dysplasia should be evaluated in terms of patients rather than hips, we selected the worse side as the index hip when comparing bilaterally involved patients with an asymmetrical outcome and unilaterally involved patients. The Severin radiographic classification system represents the most commonly used criteria for radiographic outcomes following treatment of developmental dysplasia of the hip. Very few prior authors have assessed the effect of bilateral involvement on long-term radiographic outcomes. Ryan et al.5 reported that age at reduction, quality of the initial reduction, and perhaps bilateral involvement affected the radiographic outcome at skeletal maturity. Our analysis demonstrated no difference between unilateral and bilateral dysplasia with

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Fig. 1-A


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Femoral head deformity secondary to osteonecrosis may be an important factor in early development of osteoarthritis in spite of a satisfactory Severin classification. Some authors have proposed that femoral shortening facilitates reduction of the hip in older children without increasing the risk of osteonecrosis4,5,16. Subasi et al.7 reported that patients with bilateral dysplasia who were treated surgically before the age of 5.5 years had less osteonecrosis. Ryan et al.5 reported that the prevalence of osteonecrosis increased to 70% in patients who were older than seven years of age at the time of surgery. In our patients, bilateral dysplasia was associated with a significantly higher rate of osteonecrosis in the univariate analysis, but only age at surgery and Tönnis grade, not bilaterality, were indentified as risk factors in the multiple logistic regression model (Table III). We propose that older age and a higher dislocation grade, and not bilateral involvement itself, may be the true determinants of osteonecrosis occurrence. We believe that poorer functional outcomes and asymmetrical outcomes are even more complicated to manage. Our analysis revealed that older age and bilaterality were risk factors for a poorer clinical outcome. However, when asymmetrical cases were eliminated, the McKay clinical outcome was in fact similar between the two groups. Moussa and Al-Othman14 reported that four (27%) of fifteen patients with bilateral dysplasia had unequal outcomes in the two hips, whereas 34% of the patients in our series had such an asymmetrical outcome. Variability in anatomy, different Tönnis grades on the two sides, and sequential surgical procedures contribute to the

Fig. 1-B

(Fig. 1-A) Anteroposterior pelvic radiograph showing symmetrical Tönnis grade-IV dislocation in a thirty-four-month-old girl with bilateral developmental dysplasia of the hips. (Fig. 1-B) Radiograph made one year after similar surgical procedures, including one-stage open reduction and Pemberton osteotomy with femoral shortening osteotomy, were performed on both hips.

respect to the latest Severin classification. However, a satisfactory Severin classification at medium-term follow-up does not guarantee a favorable long-term outcome. Thomas et al.15 reported that 31% of involved hips treated with Salter osteotomy had undergone joint replacement at forty-five years even though 96% had been classified as Severin class Ia, Ib, or II at a mean of 5.5 years after the initial open reduction procedure. In addition, bilaterally involved hips had a significantly greater risk of subsequent hip replacement compared with hips with unilateral involvement.

Fig. 1-C

Anteroposterior radiograph made ten years and six months after the surgery demonstrating Kalamchi class-II osteonecrosis with valgus angulation of the right hip, which resulted in hip dysplasia and classification of the outcome as Severin class III. The outcome was considered asymmetrical because the Severin class in the left hip was Ib, which was more than one grade different from the outcome in the right hip.


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complexity and uncertainty in treating bilateral dysplasia. Several precautions must be taken to achieve symmetrical and satisfactory outcomes for both sides. These include cautious protection of the first hip during the surgery on the second hip and symmetrical surgical procedures on both hips. However, eleven (58%) of nineteen patients in the present series who had equal Tönnis grades and similar operative procedures bilaterally eventually developed asymmetrical outcomes (Figs. 1-A, 1-B, and 1-C). The rate of redislocation after open reduction has been reported to be 0% to 8%6,17,18. Bilateral involvement was reported as a separate risk factor for failures of hip reduction that were poorly explained by technical issues18,19. Sankar et al.19 proposed that an excessively large and dysmorphic femoral head and abnormal femoral version may be responsible for some inevitable failures. Our data showed a tendency for a higher redislocation rate in bilateral cases, although this did not reach significance because of the small number of failures. In conclusion, the current study demonstrated that children of walking age with bilateral and unilateral dysplasia treated with one-stage surgery had similar outcomes according to the Severin classification. Osteonecrosis rates were equal if age and Tönnis grade were adjusted for. McKay clinical outcomes were similar if bilaterally affected patients with asymmetrical outcomes were eliminated. Age at the time of surgery, Tönnis grade, and asymmetrical outcome were the most im-


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portant determinants of the outcome of treatment for bilateral dysplasia. Appendix Tables summarizing the Severin and Kalamchi classifications and comparing the Tönnis grades in the two groups are available with the online version of this article as a data supplement at jbjs.org. n

Ting-Ming Wang, MD, PhD Kuan-Wen Wu, MD Shier-Chieg Huang, MD, PhD Department of Orthopedic Surgery, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei 10002, Taiwan Shu-Fang Shih, MBA, MSc, PhD Department of Health Promotion and Health Education, College of Education, National Taiwan Normal University, 162 Heping East Road, Section 1, Taipei 106, Taiwan Ken N. Kuo, MD School of Medicine, Taipei Medical University, 250 Wuxing Street, Taipei 11031, Taiwan. E-mail address: [email protected]

References 1. Greene WB, Drennan JC. A comparative study of bilateral versus unilateral congenital dislocation of the hip. Clin Orthop Relat Res. 1982;162(162):78-86. 2. Viere RG, Birch JG, Herring JA, Roach JW, Johnston CE. Use of the Pavlik harness in congenital dislocation of the hip. An analysis of failures of treatment. J Bone Joint Surg Am. 1990;72(2):238-44. 3. Zionts LE, MacEwen GD. Treatment of congenital dislocation of the hip in children between the ages of one and three years. J Bone Joint Surg Am. 1986;68(6):829-46. 4. Galpin RD, Roach JW, Wenger DR, Herring JA, Birch JG. One-stage treatment of congenital dislocation of the hip in older children, including femoral shortening. J Bone Joint Surg Am. 1989;71(5):734-41. 5. Ryan MG, Johnson LO, Quanbeck DS, Minkowitz B. One-stage treatment of congenital dislocation of the hip in children three to ten years old. Functional and radiographic results. J Bone Joint Surg Am. 1998;80(3):336-44. 6. Kershaw CJ, Ware HE, Pattinson R, Fixsen JA. Revision of failed open reduction of congenital dislocation of the hip. J Bone Joint Surg Br. 1993;75(5):744-9. 7. Subasi M, Arslan H, Cebesoy O, Buyukbebeci O, Kapukaya A. Outcome in unilateral or bilateral DDH treated with one-stage combined procedure. Clin Orthop Relat Res. 2008;466(4):830-6. 8. Blockey NJ. Derotation osteotomy in the management of congenital dislocation of the hip. J Bone Joint Surg Br. 1984;66(4):485-90. 9. Pemberton PA. Pericapsular osteotomy of the ilium for treatment of congenital subluxation and dislocation of the hip. J Bone Joint Surg Am. 1965;47:65-86. 10. Tönnis D. Congenital hip dislocation. New York: Thieme-Stratton; 1982.

11. Severin E. Congenital dislocation of the hip; development of the joint after closed reduction. J Bone Joint Surg Am. 1950;32(3):507-18. 12. Kalamchi A, MacEwen GD. Avascular necrosis following treatment of congenital dislocation of the hip. J Bone Joint Surg Am. 1980;62(6):876-88. 13. McKay DW. A comparison of the innominate and the pericapsular osteotomy in the treatment of congenital dislocation of the hip. Clin Orthop Relat Res. 1974 Jan-Feb;(98):124-32. 14. Moussa M, Al-Othman A. Bilateral developmental dysplasia of the hip: asymmetric outcome in the older child. Clin Orthop Relat Res. 2001 Nov;(392):358-65. 15. Thomas SR, Wedge JH, Salter RB. Outcome at forty-five years after open reduction and innominate osteotomy for late-presenting developmental dislocation of the hip. J Bone Joint Surg Am. 2007;89(11):2341-50. 16. Schoenecker PL, Strecker WB. Congenital dislocation of the hip in children. Comparison of the effects of femoral shortening and of skeletal traction in treatment. J Bone Joint Surg Am. 1984;66(1):21-7. 17. McCluskey WP, Bassett GS, Mora-Garcia G, MacEwen GD. Treatment of failed open reduction for congenital dislocation of the hip. J Pediatr Orthop. 1989;9(6): 633-9. 18. Kamath SU, Bennet GC. Re-dislocation following open reduction for developmental dysplasia of the hip. Int Orthop. 2005;29(3):191-4. 19. Sankar WN, Young CR, Lin AG, Crow SA, Baldwin KD, Moseley CF. Risk factors for failure after open reduction for DDH: a matched cohort analysis. J Pediatr Orthop. 2011;31(3):232-9.