The goal of achieving a stable and durable anatomic reduction has been sought by orthopedic surgeons for many years. In 1908 and 1973, Ludloff 1 and Ferguson 2, respectively, reported on an operative technique in which the main obstacles against the concentric reduction of the femoral head into the acetabulum were targeted. They stated that if this operation was performed relatively early in the course of developmental dysplasia of the hip (DDH), stimulation of acetabular development and prevention of secondary dysplasias may be more evident.
Previous studies have reported failure in achieving a nondysplasic hip joint without the need of secondary procedures and sustaining a stable relationship between the acetabular and femoral head after medial open reduction 3–5. Okano et al. 6 obtained unacceptable results when the operation was performed on patients aged over 17 months. Nevertheless, recent studies on acetabular development and prediction of hip dysplasia in patients with DDH have shown that a swift remodeling of the acetabulum occurs within the first year of reduction and continues slowly until 7 or 8 years of age 7. Also Kitoh et al. 8 demonstrated the acetabular index angle (AI) at 4 years and center-edge angle (CEA) at 5 years to be the most important predictors of acetabular development and these can be the most reliable predictors of future acetabular dysplasia. Although they used a patient group with an average age of 9.3 months at the time of reduction, controversy still exists about the upper age limit for medial open reduction.
The purpose of the present study was to evaluate the short-term to mid-term results of medial open reduction in the treatment of DDH in a larger study. We also aimed to determine the safe upper age limit for medial open reduction by comparing two groups of patients in conjunction with certain criteria, such as weight-for-age percentile and the presence of ossific nucleus. In addition, potential prognostic factors for functional outcome and correction ratio of the acetabular index, which implies acetabular development, were analyzed and compared with radiological findings with regard to the ambulation pattern of the patient at the time of the operation.
Materials and methods
Institutional review board approval was obtained for this retrospective study. Using our comprehensive prospective database, we retrospectively carried out a radiographic and clinical evaluation of patients treated for DDH. From February 2003 to September 2005, the senior author (M.A.) performed 152 (116 patients) consecutive medial open reductions for DDH. Our indications to perform a medial open reduction were older age (>6 months) and intraoperative grade 2 or grade 3 arthrographic reductions.
Of these, two patients had undergone an additional unilateral proximal femoral derotation osteotomy at the time of the initial operation. Five patients had a history of traction, followed by closed reduction (all bilateral). A Pavlik harness was applied to 21 hips (n=16; five bilateral, 11 unilateral). Twenty-six patients (36 hips) were lost to follow-up or their charts and radiographs were not available for review. To obtain a homogenous case series for the treatment of DDH by medial approach and to determine its clear effect on DDH, whether the patient is ambulatory or not, the selected patients for this study must not have had any of the above interventions, for either the pelvis or proximal femur. Finally, 49 patients (69 hips) were excluded from the study, leaving a total of 83 hips of 67 patients (16 bilateral and 51 unilateral involvement) for evaluation. The average age of the patients at the time of surgery was 13.97±3.13 months (range, 7–23 months). There were 17 male and 50 female patients (Table 1).
The patients were assigned to two groups on the basis of whether the patient was able to walk or not at the time of the operation; group 1, before walking age (n=29); group 2, after walking age (n=38). Both groups were comparable in respect of all of the above-mentioned variables.
The operative procedure utilized a standard Ferguson medial approach. The decision to perform an adjunctive capsulotomy was based on intraoperative arthrographic assessment of the hip. In case of grade 2 or grade 3 arthrographic reductions, the dissection was carried out posterior to the adductor brevis, and after division of the iliopsoas tendon, capsulotomy was performed; ligamentum teres was excised and the inferior transverse acetabular ligament was sectioned. Bilateral involvements were operated on in the same session. After closure of the incision, a hip spica cast was applied to all patients at 90° flexion and 60° abduction and they were removed at the end of 3 months. A full-time abduction brace was then worn for a further 1.5 months. The patient underwent a period of physical therapy to regain motion of the hip and no further treatment was given.
Radiological assessment of the hips was made according to the Severin classification 9. While Severin groups I and II were defined as acceptable, III, IV, and V were defined as unacceptable. Once the radiological evaluation of the hip joint had acceptable intraobserver and interobserver reliability, preoperative and periodic postoperative radiographic analysis was carried out in an unblinded manner for all patients by one senior-level orthopedic resident (I.D.) 10. Supine anteroposterior radiographs of the hips were taken preoperatively to measure the AI of Hilgenreiner 11. At the last visit, standing anteroposterior and false-profile radiographs were taken to evaluate the AI of Hilgenreiner, CEA of Wiberg 12, the anterior center-edge angle (ACEA) of Lequesne 13, and the collodiaphyseal angle (CDA) of the femur. The preoperative and postoperative values were compared to assess deformity correction. The Kalamchi–MacEwen classification system was used to determine the rate of avascular necrosis (AVN) 14. The medical records and radiographs of the patients were also reviewed to assess the radiographic appearance of nucleus of the femoral head and the weight-for-age percentiles both for males and females.
Clinical hip function was graded according to the McKay criteria. All patients returned for a follow-up clinic visit and radiographic examination at a minimum of 5.6 years. Parent-reported overall satisfaction with the surgical procedure was also ascertained at the most recent follow-up visit.
The correction ratio of AI, ACEA, CEA, and CDA were compared using Student’s t-test. The preoperative and postoperative values of AI, the correlation between the correction ratio of AI and the follow-up period, and the correction ratio of AI, ACEA, CEA, and CDA were compared using Pearson’s correlation test. Significance was determined at a P value of less than 0.05.
The average follow-up period was 6.6 years (range, 5.6–8.8 years). At the time of the operation the mean age was 13.9 months (range, 7–23 months). Radiographic analysis demonstrated consistent acetabular correction and significant improvement in the AI (mean, 22.6°; P<0.001). Overall treatment results including radiological measurements are summarized in Table 2. The Pearson correlation test revealed no significant difference between the correction ratio of AI and the follow-up period for surgically treated patients (r=0.02; P>0.05). There were no statistically significant differences between the correction ratio of AI and the operative age (r=0.19; P>0.05), operative side (r=0.19; P>0.05 and r=−0.19; P>0.05, for right and left sides, respectively), presence or absence of ossific nucleus (r=0.07; P>0.05) and sex of the patients (r=0.08; P>0.05). The effects of the ambulation pattern of the patient at the time of the operation on radiological parameters are shown in Table 3.
Although, 44 (65.6%) patients obtained excellent or good results, the functional outcome in patients and parents was rated as very favorable because 51 parents who provided feedback reported that they were satisfied with the procedure. Of them, four parents could not be reached at the time of this review but were satisfied when last seen. According to the modified McKay criteria, 24 patients (35.8%) had excellent results, 20 (29.9%) good, 16 (23.9%) fair, and 7 (10.4%) poor. A separate evaluation was made to elicit the effect of the operative age on the modified McKay criteria. Excellent and good results were obtained for 17 (58.6%) group 1 patients and 27 (71.1%) group 2 (Fig. 1a–d) patients (Table 4).
A final evaluation of the hips using the Kalamchi–MacEwen classification showed 20 (24.1%) AVN changes. Further evaluation of AVN showed no correlation between the operative age and the rate of AVN (P>0.05). In addition, 11 Kalamchi changes (13.3%) in group 1 and nine (10.8%) in group 2 were noted (Fig. 2a–d). Although statistically not significant, with regard to the weight-for-age percentile, 14 of 20 Kalamchi changes were noted in patients at 50 percentile or more. There were no short-term complications other than reduction loss in eight patients, six of whom had a high weight-for-age percentile. All eight were treated by closed reduction and cast reapplication.
To date, the management of a child after walking age with developmental hip dysplasia remains controversial 15–20. Perhaps the most challenging clinical scenario occurs when the proximal part of the femur of a weight-bearing child compresses the posterosuperior part of the acetabulum leading to adhesion and contractures with shortening of the external rotators. Numerous studies are available analyzing the outcomes after open reduction of DDH by anterolateral or medial approaches 21–23. Sener et al. 24, Okano et al. 6,25, and Mardam-Bey et al. 26 reported high failure and complication rates of the medial open reduction when done after walking age. Apart from these studies, however, Chmielewski et al. 27 stated that a medial approach, which is simple and effective, goes directly to the area where main obstacles of an anatomic reduction exists.
The current standard of practice for managing DDH is to perform and maintain an anatomic reduction for acetabular development. Most orthopedic surgeons prefer the anterolateral approach for the treatment of DDH after walking age. The anterolateral approach allows capsulorrhaphy, simultaneous pelvic osteotomy, and eversion of the limbus. A review of failed open reductions showed the anteromedial area to be the area of failure 21,22. Mankey et al. 28 has stated the importance of effective capsulorrhaphy in the first postoperative week and O’Hara et al. 29 has reported the adverse effects of limbectomy on acetabular development. Keeping these considerations in mind, a medial approach was chosen for the treatment of DDH at walking age as having advantages compared with an anterolateral approach with respect to minor bleeding risk, shorter operation time, and smaller exposure, with reduced damage to tissues.
According to the modified McKay criteria, our results (65.6% with excellent or good results) were similar to previous studies 3,16,17,19,20. The mean correction of the AI (22.6°) and CEA (17.4°) and Severin classification (65% at acceptable range) also corresponded to those in the literature 4,16–18,30,31. The most favorable result of this study was that although the radiological grade and femoral head involvement of the patients remained in the moderate-to-good zone, 55 of 67 parents provided positive feedback for the procedure at a mean follow-up of 6.6 years.
We also observed a relatively high risk for AVN and moderate subluxation in patients with a high weight-for-age percentile. This may be due to several factors that may increase the likelihood of cast complications or complexity of the disease. First and most importantly, many of these patients may have been followed up inexpertly in the early stages. Second, many of these patients with a high weight-for-age percentile may have had advanced or delayed bone age, both of which may have contributed to a higher risk of postoperative radiographic moderate results.
Our surgical indications for a medial approach for DDH have expanded over time. Careful preoperative assessment is necessary to determine whether a high-grade dislocated hip can be reduced with a less invasive surgical approach, such as the Ferguson technique. Surgical treatment is then tailored to reduce the hip. In a high-grade dislocation in a walking child or a child with proximal femur or acetabular deformities, a combination of techniques may be used, including anterior approach, proximal femoral varus, and derotation osteotomy or innominate osteotomy. Currently, when acetabular dysplasia is present in a child with a low acetabular growth potential, the accepted management should be focused on acetabular correction 7,32. However, it must be emphasized that normalizing the acetabular inclination by acetabular reorientation needs large surgical exposures with relatively high complication rates. This is of specific concern because of the potential growth potential of the acetabulum. For this reason, we remain reluctant to perform a medial approach unless the child does not have a high-grade dislocation. Thus, independent of whether the child is walking or not, anatomical acetabular reduction and maintenance of this anatomic reduction without any associated complications may result in continuous acetabular development. Eight of our patients on whom the medial approach was used early in our experience suffered loss of reduction in the initial postoperative period, and they required reapplication of the cast. These two instances heightened our awareness of this problem and prompted us to be more aggressive in releasing the medial capsule and to make a more effective cast application with the goal of optimizing the maintenance of anatomic reduction. Currently, we always perform inferior transverse acetabular ligament resection to ensure anatomic reduction. The safe zones of the hip joint are then evaluated, and if found not to be suitable so that additional femoral correction is required, our rationale is to perform a proximal femur varus-producing osteotomy and/or a derotation osteotomy. Two patients who had undergone proximal femur osteotomy at the time of medial approach were excluded from the study.
There are certain limitations of this study. This is a retrospective review that analyzes the results of the medial approach in children up to 23 months of age. It is likely that our clinical results, complication rates, and advanced reoperation rates for degenerative changes may be more favorable in the future as the follow-up period broadens. While all patients in this homogenous series received a medial approach, long-term results may help determine the exact consequences of this approach. Finally, identifying an appropriate control group for this patient cohort is difficult. Even historical cohorts followed in natural history studies are of limited value because of the substantial heterogenity of DDH in terms of the pathoanatomy, associated acetabular abnormalities, age of the patient, and clinical manifestations of a subluxated hip. The cohort we analyzed is unique in that it represents a consecutive series of patients, none of whom had received any previous intervention or sequential or postoperative additional surgeries.
We emphasize that surgical treatment of a dislocated hip in a walking-age child can be performed with a medial approach, which is safe and reliable. Our results suggest that appropriately applied medial open reduction is associated with good clinical results at short-term to mid-term follow-up regardless of the ambulation pattern of the patient. Continued clinical and radiographic evaluation is essential to assess the efficacy of this surgical strategy.
Conflicts of interest
There are no conflicts of interest.
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