Salter osteotomy without open reduction in the Tönnis type II developmental hip dysplasia: A retrospective clinical study

Abstract

Purpose:

We aimed to evaluate the clinical and radiological outcomes of children older than 18 months who were treated with Salter osteotomy without open reduction for Tönnis type II hip dysplasia.

Methods:

Thirty-two type II hips of 24 patients were included in the study. The mean age was 43.22 (18–108) months. The mean follow-up period was 50 (24–142) months. Seven patients had left sided, nine had right sided, and eight had bilateral developmental dysplasia of the hip. All patients underwent closed reduction and Salter osteotomy. Preoperative and postoperative radiographs were assessed by measuring the center-edge (CE) angle of Wiberg, Smith’s c/b and h/b ratio, and acetabular index (AI). Patients were evaluated clinically according to McKay’s criteria and radiologically according to Severin criteria. The Kalamchi and MacEwen criteria were used in the evaluation of avascular necrosis.

Results:

The mean preoperative AI, CE angle, c/b, and h/b ratio were 36.7° (±4.1), 7.2° (±5.9), 0.9 (±0.08), and 0.05 (±0.04), respectively. The mean latest follow-up AI, CE angle, c/b, and h/b ratio were 18.2° (±1.7), 38.8° (±5.4), 0.6 (±0.03), and 0.19 (±0.04), respectively. The comparison of preoperative and postoperative radiological values revealed statistically significant improvement (p < 0.01). On the latest physical examinations of the patients, 25 (78.1%) hips were rated excellent, and 7 (21.9%) were rated good according to the McKay criteria. The Severin classification determined 25 (78.1%) hips were grade I and 7 (21.9%) hips were grade II. Type I avascular necrosis (AVN) was seen in four (12.5%) hips. Three of these four hips were more superolateral in preoperative radiographs (c/b > 1 and h/b < 0.05).

Conclusions:

Salter osteotomy without open reduction is a good surgery option for Tönnis type II hip dysplasia, in which closed reduction can be performed. However, the risk of AVN should be kept in mind in more superolateral type 2 hips.

Keywords

closed reduction developmental dysplasia of the hip salter osteotomy

Introduction

Early concentric reduction is important in the treatment of developmental dysplasia of the hip (DDH). Acetabular dysplasia often worsens with the delayed diagnosis and treatment of DDH.¹ Therefore, different treatment options are applied depending on the age of the patient. While early diagnosed patients can be successfully treated with a Pavlik harness, surgical treatment becomes inevitable for most patients with a late diagnosis.² A complete development of the acetabulum often cannot be achieved even if the hip is reduced, and the acetabular dysplasia and deformation of the femoral head are continuous, especially in children treated after 18 months. In this case, pelvic and/or femoral osteotomies may be needed in the treatment.³ However, acetabular dysplasia can heal spontaneously if concentric reduction of the hip is achieved in children between 1 and 3 years old.^4,5 Despite the concentric reduction, acetabular dysplasia remains in about 26% in of the hips.⁵ There is no consensus in the literature regarding the timing of performing the pelvic osteotomy in hips with residual dysplasia.^2,6,7 Salter innominate osteotomy is a popular treatment option for the treatment of walking-age children with DDH.⁸

Open reduction in the treatment of DDH is known to cause avascular necrosis (AVN), and this risk increases in cases where osteotomy is added.⁹ Staged surgical procedures, open reduction, and osteotomy in different sessions are performed to reduce the risk of AVN. However, it has been reported that these methods have increased costs by extending the treatment period and not reducing, as expected, the risk of AVN.^10,11 Open reduction for treatment of Tönnis type II dysplasia may increase the rates of avascular necrosis.¹² Another treatment option for hips with Tönnis type II is closed reduction and Salter innominate osteotomy without open reduction, which there is insufficient research in the literature.¹³ We think the femoral head is fully covered by the acetabulum using a Salter osteotomy without open reduction in the treatment of Tönnis type II hip dysplasia; moreover, it provides a suitable environment for the remodeling of the acetabulum and femoral head. Thus, if cover of the acetabulum without open reduction in such patients is sufficient, it can both reduce AVN risk and achieve excellent remodeling.

In this study, we evaluated the effectiveness of the Salter osteotomy without open reduction in the treatment of children with Tönnis Type II hip dysplasia older than 18 months.

Materials and methods

A total of 153 patient with DDH who underwent Salter innominate osteotomy between 2002 and 2016 in our university hospital were retrospectively assessed using their medical record. All patient’s parents were given detailed information about treatment and a written informed consent was obtained from each participant. Patients with pathological or teratological dislocations (n = 2), arthrogryposis multiplex congenita (n = 2), and neuromuscular diseases such as cerebral palsy and neural tube defects (n = 3); those who previously underwent surgical and traction treatments (n = 103); and those with a follow-up duration of <24 months (n = 19) were excluded. Thirty-two hips of 24 patients aged older than 18 months who underwent Salter innominate osteotomy without open reduction for Tönnis type II hip dysplasia but did not receive any previous treatment for DDH were included.

Surgical technique

The patients underwent surgery while in the supine position, and a bikini-type incision was used. The straight head of the rectus femoris was elevated from the anterior inferior iliac spine, and then the reflected head of the rectus femoris was transected. After performing iliopsoas tenotomy, stability, and reduction of the hip were assessed via clinical and radiological examinations. Reduction was evaluated via arthrography to determine whether the hips were concentrically reduced on intraoperative fluoroscopy images. Open reduction was performed when concentric reduction was not successful, and such patients were excluded from this study. Salter osteotomy without open reduction was performed in other patients who achieved concentric reduction. Then, an appropriate sized, triangular graft that was harvested from the ipsilateral iliac crest was placed at the osteotomy line and then fixed using three Kirschner wires. All patients were fitted with a hip spica cast at 30° flexion, 30° abduction, and 10° internal rotation; the cast remained for 6 weeks after surgery. The patients were released to full joint use and movement after the cast was removed, and they started walking around 15 days after the cast removal. No device or orthosis was used postoperatively.

After 6 months, the Kirschner wires were removed when the patients under general anesthesia. Preoperative and postoperative latest radiographs (Figures 1 and 2) were assessed by measuring the CE angle of Wiberg, AI, and Smith’s c/b and h/b ratio.¹⁴ The Severin classification was used in the assessment of X-ray images at the last follow-up, as the femoral head was ossified in all patients. CE angle measurements were preoperatively performed by determining the most central part of the ossification center of the femoral head and the upper outer bone margin of the acetabulum as guide points. The patients were evaluated clinically and radiologically according to McKay’s criteria and Severin criteria, respectively.¹⁵ Kalamchi and MacEwen criteria were used in the evaluation of AVN.¹⁶

Figure 1.

Twenty-six-month-old girl. (a) Pelvic AP radiograph showing bilateral Tönnis type II hip dysplasia (more superolateral position). (b) Intraoperative fluoroscopic images of the same patient after Salter osteotomy. (c) Radiograph, 4 years postoperatively and there is no evidence of avascular necrosis.

Figure 2.

Twenty-month-old girl. (a) Pelvic AP radiograph showing left Tönnis type II hip dysplasia. Postoperative month 5 (b) and year 3 (c) radiographs of the same patient.

Statistical analysis

All data were evaluated using SPSS version 21.0 (IBM Corp., Armonk, New York, USA). The distribution of continuous variables was determined using the Kolmogorov–Smirnov test and Shapiro–Wilk normality test. The Wilcoxon signed-rank test was used to compare non-normally distributed outcome variables before and after surgery. Parametric, nonparametric and categorical data were expressed as mean ± standard deviation, median (interquartile range (IQR): 25–75 percentile) and percentage, respectively. The values of p < 0.05 were considered statistically significant.

Results

All patients were female, with a mean age of 43.22 ± 28.4 months. The mean follow-up period was 50 ± 27.8 months. The mean age during the latest follow-up examination was 8.5 ± 3.1 years. In total, 7, 9, and 8 patients presented with left sided, right sided, and bilateral DDH, respectively. Superficial and deep infections were not observed in all patients. The Kirschner wire in the iliac crest of 1 (3.7%) patient was broken and could not be removed. The graft was partially (50%) resorbed in 1 (3.7%) patient. The mean surgical time in patients with unilateral dysplasia was 47 ± 6.6 min, and the mean blood loss was 23 ± 8.1 cc. Meanwhile, in patients with bilateral dysplasia, the mean operative time and blood loss were 60 ± 7.1 min and 50 ± 14 cc, respectively. The mean postoperative hospital stay was 3 ± 1.0 days. None of the patients required blood transfusion after surgery.

The comparison of preoperative and postoperative radiological values revealed statistically significant improvements (p < 0.01; Table 1). Based on the latest physical examinations, 25 (78.1%) hips were in excellent condition and 7 (21.9%) were in good condition according to the McKay criteria. Twenty-five (78.1%) hips were grade I and 7 (21.9%) were grade II according to the Severin classification. Type 1 AVN was observed in four (12.5%) hips. Three of these four hips were more superolateral in preoperative radiographs (c/b > 1 and (h/b < 0.05). Recurrent subluxation or dislocation was not observed, and no additional surgery was required. A leg length discrepancy of <1 cm developed in four (16%) patients, and these patients were clinically asymptomatic.

Table 1.

Preoperative and latest follow-up AI, CE, and c/b and h/b ratio values of patients.

	Preoperative median (IQR)	Latest follow-up median (IQR)	p Value^a
Acetabular index	35.5° (34–38)	18.0° (17–19)	<0.01
Center-edge angle	8.0° (0–13)	39.0° (35–44)	<0.01
c/b ratio h/b ratio	0.79 (0.75–0.82) 0.04 (0.02–0.08)	0.63 (0.61–0.66) 1.16 (1.08–1.21)	<0.01 <0.01

IQR: interquartile range.

^aWilcoxon signed rank test.

Discussion

Pathological hip changes in the new-born period are usually reversible, but more permanent and resistant changes occur in patients with a late DDH diagnosis.¹³ In the literature, treatment methods involving open reduction alone or together with pelvic and/or femoral osteotomies in children older than 18 months are recommended for the treatment of DDH.^17

–20 It is unclear which surgery options may reduce the risk of complications and may result in good clinical and radiological outcomes.²¹ Our study showed that the Salter innominate osteotomy without open reduction in the treatment of Tönnis type II hip dysplasia may be a reasonable choice for solving this problem. In our study, 78.1% of the patients achieved excellent and 21.9% achieved good results, according to the McKay criteria. Postoperative radiological values (AI, CE angle, and c/b and h/b ratio) significantly improved compared with preoperative values.

AVN is the most feared complication in DDH treatment. The rate of AVN occurrence after DDH treatment varies between 6% and 48% in the literature.^22

–25 The diagnosis of AVN may be difficult, particularly during periods of minor radiological changes. Therefore, long-term follow-up is needed.²⁶ Ischemic changes of the femoral head usually can be observed on radiographs within the first year after surgery. The classification of AVN becomes possible in the second year after surgery.²⁴ The risk of AVN is known to increase in patients undergoing open reduction.⁹ Moreover, the application of open reduction and Salter osteotomy in the same session could further increase this risk (5.7–37%).^27,28 Also, as the capsule is opened when open reduction with pelvic osteotomy is performed together, the control of the acetabular fragment can be difficult during the covering of the femoral head. Staged surgeries may be preferable to avoid these problems, but repeated surgeries can create additional problems.²⁶ To avoid complications of open reduction, it was reported that pelvic osteotomy without open reduction can be performed by careful intraoperative examination and evaluation in some cases.^13,15 In our study, type I AVN was detected in four (12.5%) hips with at least a 2-year follow-up. We found the risk of AVN to be high, but all cases were type I AVN and clinically asymptomatic. The AVN may have been caused by a relative increased pressure primarily due to the new position of the acetabulum.^9,29,30 A similar situation may occur in the closed reduction of the more superolateral hips. As a matter of fact, three of the four hips that developed AVN were located in the superolateral position. When considering the advantages of pelvic osteotomy without open reduction, we can say that it has achieved successful results in suitable patients, although the risk of type I AVN is high.

Salter³¹ reported that bilateral pelvic osteotomy might cause pelvic instability and loss of fixation and, thus, it is contraindicated. He also suggested that there should be at least 2-week intervals between two osteotomies. But, it has been shown in later studies that bilateral pelvic osteotomies could be performed in a safe manner.^11,32 We did not encounter any complications such as pelvic instability and loss of correction in patients who received simultaneous bilateral Salter osteotomy without open reduction. Smith’s c/b ratio showing the lateralization of the femoral head and h/b ratio showing the superior displacement. These ratios are easily applicable methods which change minimally with age, and they can be used safely in follow-up of patients with DDH in all age groups.⁸ CE angle increases with age, so assessing this is recommended in the follow-up of children older than 4 years.¹⁴ The latest radiological evaluation of our patients was performed using AI, CE angle, and c/b and h/b ratio. Compared with the preoperative values, statistically significant improvements were found (p < 0.01), and excellent and good results were obtained according to Severin criteria.

Akman et al.¹³ reported they could not find statistically significant differences between the radiological results and AVN rates in patients undergoing closed versus open reduction and Salter osteotomy. In their study, AVN was not reported in any of the patients who received closed reduction and Salter osteotomy.¹³ But, type I AVN developed in four (12.5%) hips in our study. This may be due to the fact that Akman et al.¹³ had performed open reduction and Salter osteotomy for the superolateral type II hips.

Our study has some limitations, such as a small sample of patients, lack of a control group, and a short follow-up period. However, this study showed that the Salter osteotomy without open reduction produced good clinical and radiological results and is a good choice for the future. Further research with a larger sample and longer follow-up period is needed to confirm the reliability and validity of our findings.

Conclusion

The main goal in the treatment of DDH is to achieve a concentric hip reduction and continues this reduction until the hip development is complete. The fewer surgeries made for this purpose, the less complication will become. This present study shows that Salter pelvic osteotomy without open reduction in type II hip dysplasia, which appeared to be concentric reduction with arthrography; it is easy to apply, safe, and the results are good; furthermore, the complications are low. Because there is no open reduction, the duration of operation is shorter than usual, blood loss is less. However, the risk of AVN should be kept in mind in more superolateral type 2 hips. Concentric reduction of the hip joint must be confirmed by intraoperative arthrography and open reduction should be performed in cases where concentric reduction is not achieved.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Murat Gurger

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