Great advances in the early diagnosis and conservative treatment of idiopathic developmental dysplasia of the hip have reduced the frequency of surgical corrections. Nevertheless, operative treatment is needed in some cases. Hip joints with developmental dislocation of the hip are characterized by simultaneous pathologic alterations of the acetabulum and proximal femur.7 After closed hip reduction procedures, dysplasias that need surgical correction often are located on both parts of the hip joint.
The following factors are important for judging the operative method for correction of developmental dysplasia of the hip: (1) frequency of redislocation in cases of former dislocation, (2) rate of avascular necrosis of the femoral head, (3) postoperative joint stiffness, (4) influence on later joint development, and (5) prevention of early osteoarthrosis.
Combining the acetabuloplasty with simultaneous intertrochanteric osteotomy (mostly derotational varus osteotomy) has been a matter of controversy in Europe for a long time because of the perceived risk of damaging the femoral head as a consequence of the complex surgical operation. Some authors report that this procedure should be harmless.1,6,16,17,19,23,24,33 Other authors caution against simultaneously correcting deformities of the proximal femur.4,18,29,32,34,35
On the basis of the assessments of the Commission for the Study of Hip Dysplasia of the German Society of Orthopaedics and Traumatology,34 it was recommended that surgical correction of the acetabulum should be done simultaneously with open reduction of the hip joint. However, additional derotational varus osteotomy should not be done because of the increased risk of avascular necrosis of the femoral head.35
This study investigates the long-term results of a modified Dega acetabuloplasty16 done simultaneously with intertrochanteric osteotomy of the femur (mostly derotational varus osteotomy). The results reported are based on a review of clinical records and reexamination of patients to acquire current clinical and radiographic data.
MATERIALS AND METHODS
Patients with developmental dysplasia of the hip who underwent a modified Dega acetabuloplasty in combination with an intertrochanteric osteotomy at the authors' institution between 1973 and 1984 were reviewed. This combined surgery was done on a total of 97 hips in 74 children. Fifty-one patients with 70 surgically treated hips were contacted. The mean patient age at the time of operation was 2.9 years (range, 8 months to 8 years); 10 patients were younger than 18 months old at the time of operation. Sixty-nine percent of the patients were girls. The operation was done on 22 left hips, 12 right hips, and in 18 patients, bilaterally. The mean patient age at the time of this postoperative investigation was 14.1 years (range, 10-23 years) with a mean followup time of 15.2 years (range, 10-19 years) after acetabuloplasty.
All patients had idiopathic developmental dysplasia of the hip. Patients who had a neuromuscular disease, a connective tissue disorder, or an infection of the hip were excluded from the study. Sixty-two of the 70 hips were treated previously nonoperatively. Fifty-nine joints had undergone an overhead traction; 41 were placed in a Lange or Lorenz cast and 7 in a Fettweis cast. Eight patients were treated with a Matzen abduction splint (Michael Busch Orthopädie-Technik, Halle, Germany). Before the combined surgical operation, 8 children underwent an open reduction and 5 an intertrochanteric osteotomy.
Preoperative arthrography of the hip joint was not done in all patients. Thus, retrospective radiographic classification of the hip dislocation grade was based on the criteria of the Commission for the Study of Hip Dysplasia.34 At the time of surgery, the dislocation grades were as follows: Grade I, 20 hips; Grade II, 34 hips; Grade III, 13 hips; and Grade IV, 3 hips.
Dega acetabuloplasty was combined with derotational varus osteotomy in 61 hips. The following combined surgeries were done: (1) open reduction with acetabuloplasty and derotational varus osteotomy in 17 dislocated hips with an extremely pathologic femoral neck angle; (2) open reduction with acetabuloplasty and intertrochanteric derotational shortening osteotomy in 9 dislocated hips with a less pathologic femoral neck angle; and (3) acetabuloplasty with derotational varus osteotomy in 44 subluxated hips.
Complications were observed in 11 patients: 2 patients underwent second operation because of lyophilized bone wedge resorption; 6 had repeat varus osteotomies; 1 had plate fixation as a consequence of diaphyseal femoral fracture after plaster cast removal; and 2 had superficial wound infections.
Clinical data were classified according to the criteria of Severin30 and radiographic data as recommended by the Commission for the Study of Hip Dysplasia.35 In all cases, 8 radiographic measurements (Fig 1) were made preoperatively, postoperatively, and at the time of this investigation. The measurements were classified in 4 age related grades of deviation from the normal range (classification of Tönnis35). Grades 1 and 2 (normal and slightly abnormal) were considered a good result.
A slightly modified version16 of the Dega acetabuloplasty6 has been used at the authors' institution since 1973. After an anterolateral approach and subperiosteal exposure of the lateral and medial surfaces of the ilium (to permit insertion of curved retractors into the sciatic notch from each side), the ilium was osteotomized in the direction of the triradiate cartilage, starting from a lateral position just above the anterior inferior iliac spine. In the authors' version of the procedure, the medioposterior cortical corner remains intact, representing the rotation center, at which point the acetabular roof is deflected into lateral and anterior (Fig 2).
To initially keep the acetabular roof in the correct position, either a lyophilized bone splinter, bone wedges obtained by derotational varus osteotomy, or combinations of both materials were interposed into the osteotomy gap. During the past few years, allogenic bone wedges have been used exclusively to provide greater initial stability. These bone wedges were obtained from patients who underwent hip replacement. The bones were screened and stored according to the bone banking criteria of the German Society of Orthopaedics and Traumatology.41 No resorption or infection has been observed as a result of using allograft bone. From a clinical and radiographic point of view, there was no difference between the use of lyophilized, autogenic, or allogenic bone wedges. Except for 2 resorptions of lyophilized bone wedges, all grafts were seen radiographically to be incorporated within 6 weeks.
If an open reduction was necessary, the hip capsule was incised parallel to the labrum or narrowly resected in patients with a high hip dislocation. The thickened capitis femoris ligament and excessive fat in the acetabular fossa were resected. To achieve a deep reduction of the femoral head into the acetabulum, the medial labrum and the transverse acetabular ligament were slotted. If necessary, capsulorrhaphy and tendon release of the rectus femoris and psoas muscles also were done.
Corrections of the proximal femur were accomplished at this time using the intertrochanteric principle. Fixation of the osteotomy was made with hip plates. Postoperatively, all children were put in a hip spica cast for 4 to 6 weeks, with the length of time being dependent on their age.
Preoperative Radiographic Examination
In 18 patients there was avascular necrosis of the femoral head, Grades II to IV of Tönnis,34 with 8 joints having metaphyseal involvement.
Clinical Outcome at the Time of Investigation
Results of the Severin classification30 are shown in Table 1. All but 2 hips were without pain. These 2 joints had avascular necrosis, Grade IV. According to Tönnis,35 there was an unrestricted range of motion in 88.6% of the hips. Six hips had Grade I restriction of joint motion, and in 2 hips there was a Grade II restriction. Seven of these joints had an open reduction, and in 6 there was a avascular necrosis before surgery. The Trendelenburg sign was negative in 80% of the hips, and 7 hips had a positive Grade I Trendelenburg sign. The 2 patients with a positive Grade III Trendelenburg sign had severe head-in-neck position, with a short femoral neck and high ranking greater trochanter. This was attributed to the Grade IV avascular necrosis. There was relative leg shortening of 1 to 2 cm in 12 patients.
An overview of measurements based on anteroposterior (AP) radiographic images of the pelvis is shown in Table 2. The antetorsion view according to Dunn9 was taken only preoperatively; thus, the projected femoral neck angle of Müller25 is reported postoperatively and at the time of investigation. The acetabular angle of Hilgenreiner20 was improved by operation on average by 18 °, remaining in the physiologic range at the time of this investigation. The acetabular angle of Idelberger and Frank21 and the angle of Sharp31 also were within age related normal ranges. The acetabular shelf over the femoral head (acetabular center-edge angle of Wiberg39 was improved on average from -11 ° preoperatively to 22.1 ° postoperatively. The postoperative measurements were within the normal physiologic range. Additional evidence of the improvement were the good values for hip score according to Busse et al.5
According to the classification of the Commission for the Study of Hip Dysplasia,35 80% of the measurements of the acetabulum and head-to-acetabulum relation were in deviation Grades I or II from the normal range, which are good results (Table 3, Fig 3). Only 4 (5.7%) cases of avascular necrosis of the femoral head were caused by the operation. Preoperative avascular necrosis was present in 24.3% of the joints in various grades (Fig 4); 9 joints were altered positively by the operative procedure; and 2 joints were altered negatively. In 6 patients, the operation had no influence on the avascular necrosis.
Values of the femoral head and neck were less frequently in the normal range. In most cases, derotational varus osteotomy initially resulted in a low femoral neck angle that later was followed by recurrent valgus deformity. The development of this problem was not related to age. The influence of femoral head shape and position is seen by comparing measurements of the entire group (Table 3) with those of 24 joints that had coxa valga Grades 3 and 4 at the time of this investigation. There was a combination of acetabuloplasty and derotational varus osteotomy in all patients; an additional open reduction was done in 2 patients. The total of deviation Grades 1 and 2 in these joints was hip score of Busse et al,5 54.1%; femoral head-epiphysis angle of Jäger and Refior,22 54.1%; and femoral epiphysis index of Eyre-Brook,12 62.5%.
In this study, the combined operative method produced mostly good long-term results. Other authors have reported good results with the Salter innominate osteotomy2,8,10,11,18,23,27,28,38,40 or the Pemberton acetabuloplasty.3,13,14,18,26,32 Results of the Dega acetabuloplasty have been reported by Dega,6 Franke et al,16 and Synder and Zwierzchowski.33 Comparison of these results to those reported is not reasonable because of differences in the patient populations and other variable criteria. Most of these studies have used either only absolute radiographic hip parameters, such as the acetabular center-edge angle of Wiberg,39 or a combination of measured and described radiographic criteria, such as the Severin classification.30 An advantage of the classification of the Commission for the Study of Hip Dysplasia is the age-related rating system of each parameter in 4 grades of deviation from the normal range.35 Felske-Adler et al15 examined the differences in the evaluation of the results obtained in 117 hip joints treated by Salter innominate osteotomy by application of the Severin classification and the classification of the Commission for the Study of Hip Dysplasia. They found marked differences in all groups between these classifications. The classification system of the Commission for the Study of Hip Dysplasia showed a greater sensitivity for small deviations from the norm.
Brüning et al4 used investigational criteria almost identical to that of this study. They reported long-term results of a modified Albee-Lance acetabuloplasty done on 90 hips, mainly in combination with derotational varus osteotomy. Although the reported measurements are close to the results presented here, those authors reported a rate of avascular necrosis of 17.8% as a consequence of the surgery.
In the current study, redislocation was not seen in any patient. The radiographic measurements of the acetabulum and acetabulum-to-head relation were normal or slightly abnormal in >80% of the joints. The modified Dega acetabuloplasty allows acetabular correction with satisfactory radiographic results in slight and severe cases of developmental dysplasia in patients ranging from 0.8 to 7 years of age. In children older than 7 or 8 years of age, the acetabulum is too developed, and a persistent incongruency can result. For these older patients, triple pelvic osteotomy of Tönnis36,37 with rotation of the entire acetabulum is preferred.
Results of this clinical examination were very good and good in 80% of the hips. Positive Trendelenburg signs were found in 20% of the hips, of which 10% were Grades II or III. This was the group identified as having severe deformities and residual complications after avascular necrosis of the femoral head.
The rate of avascular necrosis caused by the operation was 5.7%. This was considerably lower than that in the examination of the Commission for the Study of Hip Dysplasia, which also assessed cases with combined operative procedure.34 The reported rate is comparable to the 1-stage procedure results of Grill and Frischhut,17 who did an innominate iliac osteotomy combined with a femoral shortening osteotomy in 42 congenitally dislocated hips.
In the current series, the duration of preoperative dislocation and subluxation and the type and duration of the closed reduction procedure had more influence on the rate of avascular necrosis of the femoral head than did the operative procedure. A higher rate of avascular necrosis was seen preoperatively in patients who underwent overhead traction with hip abduction of as much as 90 ° and treatment with Lorenz and Lange casting.
Reservations about simultaneous intertrochanteric osteotomies are not necessary because there is less risk of avascular necrosis of the femoral head caused by the operation than risk of later developmental deformities of the proximal femur. In addition to avascular necrosis, excessive recurrent valgus angulation to a head-in-neck position or subcapital coxa valga was the primary factor contributing to poor results in this study.
The results of this study are in agreement with those of Windhager et al40 in that better femoral head centricity in the acetabulum is an initial temporary consequence of derotational varus osteotomy and does not compensate for the risk of later proximal femoral deformities. Thus, derotation and shortening should be done subtrochanterically (Fig 5). Intertrochanteric varus osteotomies should be done only in exceptional cases, such as extremely high dislocated hips in older children.
To address the assertions about later development of osteoarthrosis, a longer followup is needed than was possible in this study. Nevertheless, in reviewing the critical remarks about derotational varus osteotomy, the described method provides predictable results for operative treatment of developmental dysplasia of the hip.
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