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© 1997 The Journal of Bone and Joint Surgery, Inc. Long-Term Outcome after Open Reduction through an Anteromedial Approach for Congenital Dislocation of the Hip* , IOWA CITY, IOWAInvestigation performed at the Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, Iowa City
We reviewed the long-term outcome of open reduction of ninety-three congenitally dislocated hips (in seventy-six children) through an anteromedial approach. The average age of the patients was fourteen months (range, two to fifty months) at the time of the reduction and eleven years (range, four to twenty-three years) at the time of the most recent follow-up evaluation. At the most recent follow-up evaluation, sixty-six hips (71 per cent) had an excellent or good result, twenty-four (26 per cent) had a fair result, and three (3 per cent) had a poor result, according to the Severin classification system. An inverted neolimbus at the time of the operation and postoperative growth disturbance of the femoral head were associated with a poor roentgenographic result. According to the classification of Bucholz and Ogden, twenty-two hips (24 per cent) had type-II avascular necrosis, thirteen hips (14 per cent) had type-III, three (3 per cent) had type-IV, two (2 per cent) had non-classifiable lesions, and fifty-three (57 per cent) did not have avascular necrosis. A high hip dislocation and an operation after the age of twenty-four months were associated with a higher rate of growth disturbances of the femoral head. With the numbers available for study, we did not find any association between short-term preoperative traction, ligation of the medial circumflex vessel, or the type of neolimbus and the prevalence of growth disturbances. Two hips redislocated postoperatively, and seven had transient stiffness. We consider the anteromedial approach to be useful in the management of patients with congenital dislocation of the hip who are twenty-four months old or less. The advantages of this approach include direct access to the obstacles to reduction, avoidance of damage of the iliac apophysis and the abductor muscles, minimum blood loss, the need for only a single operative session for treatment of both hips, and a cosmetically acceptable scar. The prevalence of type-II growth disturbances of the femoral head was higher than had been expected, emphasizing the need for additional investigation.
The goals of management of children who have congenital dislocation of the hip are concentric reduction and maintenance of the reduction in order to provide the optimum environment for development of the femoral head and the acetabulum12,13,22,42,44,47. If the diagnosis is made within the first few weeks of life, the rate of success associated with use of a Pavlik harness or another abduction device is very high2,12,17,29,42. However, if diagnosis and treatment are delayed, normal development of the hip joint is jeopardized. With increasing age at detection, the obstacles to concentric reduction, both intra-articular and extra-articular, become increasingly difficult to overcome and the recovery of the acetabulum after the reduction is less predictable. The choice of operative procedure for the reduction of a congenitally dislocated hip is controversial. Some investigators have compared the advantages of an anteromedial approach with those of an anterolateral approach, but there is a lack of substantive data to support any specific operative approach13,34. Advocates of an anteromedial procedure have reported that this approach is less invasive and results in less stiffness of the joint, the major obstacles to reduction are easy to reach and to correct, damage to the iliac apophysis and the abductor muscles is avoided, dissection is minimum with negligible blood loss, both hips can be operated on safely in a single operative session, and the scar is cosmetically acceptable8,10,21,23,24,27,30,36,37,47. However, the various anteromedial approaches have also been criticized because of poor visualization of the acetabulum, the associated risk of damage to the medial circumflex vessels, and the inability to perform capsulorraphy or concurrent secondary procedures13,18,19,25,34. The purpose of the present study was to review the long-term results after open reduction through an anteromedial approach in order to outline a plan of treatment based on long-term empirical data. The long-term outcome of this procedure was evaluated by examination of the roentgenographic appearance and the rate of growth disturbances of the femoral head.
We reviewed the charts of 116 patients who had been managed with open reduction through an anteromedial approach for congenital dislocation of the hip at the University of Iowa from 1970 to 1990. Patients who had a neuromuscular or teratological dislocation had been excluded previously. Forty patients who had had inadequate clinical or roentgenographic follow-up, or both, were excluded from the study, leaving seventy-six patients (ninety-three hips). All of the patients were managed under the supervision of the senior one of us (S. L. W.). The average age of the children at the time of the operation was fourteen months (range, two to fifty months). Forty-six hips were reduced when the patient was twelve months old or less; thirty-two, when the patient was thirteen to twenty-four months old; and fifteen, when the patient was more than twenty-four months old. There were sixty-two girls (82 per cent) and fourteen boys (18 per cent). Fifty-four patients (71 per cent) had a unilateral dislocation, seventeen (22 per cent) had a bilateral dislocation and open reduction of both hips, and five (7 per cent) had a bilateral dislocation and open reduction of only one hip. The bilateral reduction was performed during the same operative session in all but one patient, who had the reductions performed two months apart. Fifty-three patients (70 per cent) were firstborn children, and ten patients (13 per cent) had a positive family history for congenital dislocation of the hip. Thirty-one patients (41 per cent) had been delivered in the breech position. Thirty-two (34 per cent) of the ninety-three hips had been treated with at least one technique at another institution before the index open reduction. Thirteen hips had been treated with extra diapers; sixteen, with an abduction brace; nine, with a Pavlik harness; twenty-one, with closed reduction and application of a cast; and four, with open reduction through an anterolateral approach and application of a cast. Eighteen hips were treated with traction at our institution for an average of ten days (range, three to fourteen days) immediately before the index open reduction. Open reduction was performed if a stable and concentric reduction could not be achieved with closed means as demonstrated with arthrography. An anteromedial approach was used, for the reasons mentioned earlier8,10,21,23,24,27,30,36,37,47. Since 1970, the senior one of us has used this approach as his standard technique to treat congenital dislocation of the hip in children who are twenty-four months old or less. The operative technique has been previously described46,47. All patients had adductor and iliopsoas tenotomies. The ligamentum teres was noted to be hypertrophic or redundant in eighty-seven hips and was resected. In eighty-nine hips, the transverse acetabular ligament was found to be enlarged and it was divided. The redundant fat in the acetabulum (the pulvinar) was removed from seventy-six hips. Through direct visual observation, the femoral head was noted to be spherical in nineteen hips and deformed in forty-four; the shape was not recorded for the remaining thirty hips. The neolimbus was classified as normal, everted, or inverted with use of arthrography and direct inspection at the time of the operation. The average operative time, including that needed for application of the postoperative cast (a bilateral hip spica extending to just proximal to the ankles), for the patients who had a unilateral procedure was seventy-five minutes (range, forty-five to 107 minutes). The average blood loss was thirty-one milliliters (range, ten to fifty-two milliliters). No patient needed a blood transfusion. After the reduction, the position of greatest stability (an average of 100 degrees of flexion and 50 degrees of abduction) was selected for immobilization. Most of the patients were discharged on the third (range, second to sixth) postoperative day. The cast was removed to just proximal to the knee at six weeks and was removed completely at twelve weeks. At this time, the patient was fitted for a flexion-abduction brace. We believe that this orthosis stabilizes the hip in a position that directs the femoral head deeply into the acetabulum and allows for the continued remodeling of the hip capsule, soft tissues, and acetabulum. The orthosis was worn full-time, without weight-bearing, for two months and then only at night for an average of two years. The patient was considered to have worn the brace according to the protocol unless a note to the contrary was made in the clinical record. The records of only five patients indicated that non-compliance had been a concern. The clinical notes were reviewed for possible complications of treatment as well as for any mention of pain in the hip, limited range of motion, Trendelenburg sign, or limb-length discrepancy at the most recent follow-up examination. Pre-reduction roentgenograms were evaluated with regard to the grade of displacement41, the centering ratios of Smith et al.35, the lateral (c/b) and superior (h/b) acetabular indices15, the acetabular angle of Sharp33, and the Shenton line20. We reviewed the anteroposterior roentgenograms of the pelvis made at six-month intervals for as long as two years after the reduction, those made at the ages of five and ten years, and those made at the most recent follow-up examination. The acetabular index15; center-edge angle49; articulotrochanteric distance9; acetabular depth, width, and quotient40; angle of the acetabular roof38; and maximum width of the teardrop were recorded1. Not all measurements could be made for all hips because of interference by the gonadal shield, closure of the triradiate cartilage, or lack of a contralateral hip on the same roentgenogram. The roentgenograms also were evaluated with use of the anatomical classification system of Severin32. Degenerative changes were classified on a scale from absent (grade 0) to severe (grade III)3. Growth disturbances of the femoral head were evaluated with the classification system described by Bucholz and Ogden6. Briefly, type I indicates irregular ossification of the capital femoral ossific nucleus during the early stages after treatment but minimum or mild residual deformity; type II, localized changes in the lateral aspect of the physeal plate and metaphysis with premature fusion of the superolateral portion of the plate; type III, severe ischemic changes in the entire proximal femoral epiphysis, epiphyseal plate, and metaphysis (residual deformity in these patients consists of marked coxa vara, an extremely short femoral neck, and a severe overgrowth of the greater trochanter); and type IV, changes affecting the medial epiphyseal ossification center and metaphysis. Lesions that were non-classifiable with use of the system were designated type V. All of the roentgenographic measurements were made by one of us (J. A. M.), who was not the treating physician. To increase the accuracy and reliability of the Severin classifications and the diagnosis of growth disturbances of the femoral head, all of the roentgenograms were independently reviewed in chronological order by two of us (J. A. M. and S. L. W.), who were blinded to the most recent outcome.
Statistical Analyses
The average age of the patients at the time of the most recent follow-up evaluation was eleven years (range, four to twenty-three years). Eleven hips were followed for sixty months or less; forty-two, for sixty-one to 119 months; and forty, for 120 months or more. In general, we noted roentgenographic improvement in the acetabulum after the open reduction, reflected by a decrease in the average acetabular index from 39 degrees preoperatively to 28 degrees two years postoperatively and to 21 degrees at the time of the most recent follow-up evaluation (Tables I and II). The most marked decrease occurred during the first year after the operation. However, residual dysplasia persisted in twenty-four (26 per cent) of the ninety-three hips, and a secondary procedure (an acetabular or femoral osteotomy, or both) was recommended for these hips. The decision to recommend a secondary procedure was made on a highly individualized basis; however, in general, a procedure was indicated when dysplasia had persisted over time and expectations for satisfactory spontaneous acetabular remodeling had not been realized. Standard roentgenographic parameters, such as the acetabular index, Shenton line, femoral neck-shaft angle, and amount of femoral anteversion were taken into account. Only sixteen of the twenty-four hips had a secondary procedure. Seven hips had both an acetabular (a Salter, Pemberton, or shelf) osteotomy and a femoral varus-derotation osteotomy, seven had an acetabular osteotomy only, and two had a femoral osteotomy only. The average age of the patients at the time of these procedures was six years (range, two to seventeen years).
Roentgenograms from the most recent follow-up evaluation were reviewed for all ninety-three hips (Table II). The average width of the teardrop in the affected hips was 8.8 millimeters, compared with 7.3 millimeters in the unaffected, contralateral hips. The average center-edge angle was 20 degrees (range, -5 to 46 degrees) on the affected side and 26 degrees (range, 16 to 45 degrees) on the unaffected side. Thirty-five hips (38 per cent) were Severin32 class I, thirty-one (33 per cent) were Severin class II, twenty-four (26 per cent) were Severin class III, and three (3 per cent) were Severin class IV. There were no roentgenographic signs of degenerative joint disease. According to the classification of Bucholz and Ogden6, twenty-two (24 per cent) of the ninety-three hips had type-II avascular necrosis of the femoral head, thirteen (14 per cent) had type-III, three (3 per cent) had type-IV, and two (2 per cent) had non-classifiable lesions (type V). Superolateral physeal arrest (type II) was not apparent until the patients were an average of eight years old (range, six to eleven years old). At the most recent clinical evaluation, fourteen patients reported some pain in the hip and three had a limp. Eight patients had a measurable limb-length discrepancy (average, 1.5 centimeters; range, 0.5 to 2.0 centimeters). Twelve patients had an average decrease in the arc of internal and external rotation of 15 degrees (range, 10 to 30 degrees), compared with the unaffected hip. The arcs of flexion and extension and of abduction and adduction were normal. The Trendelenburg sign was positive in four patients, was negative in seventy-one, and was not noted in one.
Association between Pre-Reduction Clinical Parameters and Outcome Variables The patients were divided into three groups according to their age at the time of the open reduction: twelve months old or less, thirteen to twenty-four months old, and more than twenty-four months old. With the number of patients available, we did not find a significant relationship between the age-group and the most recent Severin classification32. However, the prevalence of growth disturbances of the femoral head increased with age at the time of the reduction (p < 0.03). Of the forty-six hips that had been reduced when the patient was twelve months old or less, sixteen (35 per cent) had a growth disturbance; the disturbance was type II in eleven, type III in four, and non-classifiable in one. Thirteen (41 per cent) of the thirty-two hips that had been reduced when the patient was thirteen to twenty-four months old had a growth disturbance; seven disturbances were type II, five were type III, and one was type IV. Of the fifteen hips that had been reduced when the patient was more than twenty-four months old, eleven had a growth disturbance, which was type II in four, type III in four, type IV in two, and non-classifiable in one. There was no apparent association between the pattern of growth disturbance and the age at the open reduction.
Association between Pre-Reduction Roentgenographic Parameters and Outcome Variables
The amount of preoperative displacement of the hip was assessed with the system of Tönnis41. Five hips were grade II, twenty-five were grade III, and sixty were grade IV. The Tönnis grade was not recorded for three hips. The prevalence of growth disturbances of the femoral head increased with the amount of preoperative displacement of the hip (p = 0.04). Six (24 per cent) of the twenty-five hips that were Tönnis grade III had a growth disturbance, compared with thirty-two (53 per cent) of the sixty that were Tönnis grade IV (Table III).
Association between Pre-Reduction Treatment and Outcome Variables With the numbers available for study, we did not find a significant association between unsuccessful treatment before the index operation and the type of neolimbus observed at the time of the operation, the occurrence of a growth disturbance, or the Severin classification32 at the most recent follow-up examination.
Association between Ligation of the Medial Circumflex Vessels and Outcome Variables
Complications
A congenitally dislocated hip cannot always be reduced with closed methods. In these situations, several operative procedures have been proposed for reduction. We found, as did other authors, that with an anteromedial approach for open reduction there is direct access to the obstacles to reduction, the iliac apophysis and the abductor muscles are left undisturbed, there is minimum blood loss, both hips can be operated on safely in a single operative session, and the scar is cosmetically acceptable8,10,21,23,24,27,30,36,37,47. There is still considerable controversy concerning residual acetabular dysplasia and the prevalence of growth disturbances of the femoral head after an operation through an anteromedial approach. In the present study, the acetabular index improved quickly during the first year and then considerably more slowly afterward. At the most recent follow-up evaluation, sixty-six hips (71 per cent) had an excellent or good roentgenographic result. However, residual acetabular dysplasia was common, and a secondary procedure was considered necessary for twenty-four (26 per cent) of the ninety-three hips, which is comparable with the reported rates of 22 per cent (thirty-eight of 171 hips)23 to 54 per cent (twenty-five of forty-six hips)24 in other studies18,23,24,30. The reported prevalence of growth disturbances of the femoral head after an anteromedial approach has ranged from zero of thirty-four hips to ten of fifteen hips10,18,19,23,24,27,36,47,50. The actual prevalence is difficult to estimate from the current literature because of several factors, including various methods of initial treatment and operative approaches, the small number of patients in each series, the different definitions used to describe growth disturbances, inadequate durations of follow-up, and the multifactorial etiology of these disturbances. In the present study, the prevalence of severe ischemic necrosis (type III) was 14 per cent, which is similar to that in most reported series10,18,19,23,24,27,36,47,50. However, the prevalence of type-II necrosis (24 per cent) was higher than that expected on the basis of the literature and of our previous evaluation of this technique45,47. The reason for this finding is not entirely clear; most likely, several factors contribute to the over-all high prevalence of growth disturbances. In our series, the hips that had high dislocation (Tönnis41 grade IV) and those that were treated when the child was more than twenty-four months old had a higher rate of growth disturbances of the femoral head. Because of this adverse finding, an anteromedial approach is not recommended for children who are more than twenty-four months old, especially those who have a high dislocation. This is in agreement with a previous finding that, in such patients, increased soft-tissue and capsular adhesions posterior to the hip joint cannot be corrected adequately with an anteromedial approach8,10,47. Unsuccessful closed treatment before open reduction has been thought to increase the prevalence of femoral growth disturbances after the open reduction. These hips are believed to be more dysplastic and probably at a greater risk for vascular damage10,23,24,36. We were unable to find any significant difference in the prevalence of growth disturbances in patients who had had previous treatment compared with those who had not. Preliminary traction is thought to have a role in reducing the prevalence of growth disturbances5,16,31,43,51. However, with the numbers available for study, we found no association between the use of short-term preoperative traction and the prevalence of growth disturbances, which supports the findings of other authors4,10,27,28,45,47. In addition, our findings are in agreement with those of previous reports11,24,27,36,47 that suggested that direct operative trauma to the circumflex vessels does not appear to be the cause of ischemia of the femoral head. The etiology of type-II growth disturbances is unclear to us, and we are uncertain whether these changes are actually due to the operative procedure. Increased pressure against the posterior part of the acetabular rim and the limbus resulting from an eccentric reduction with the lower extremity positioned in forced abduction has been implicated in the pathogenesis of this type of physeal arrest7,19,26. However, in the present series, postoperative immobilization was accomplished with the hips in an average of 100 degrees of flexion and 50 degrees of abduction, which has been associated with a low prevalence of growth disturbances31. Additionally, we hypothesized that an inverted neolimbus would result in an increased prevalence of type-II growth disturbances, but we found no association between the type of neolimbus and the prevalence or type of growth disturbance. We believe that the high prevalence of type-II growth disturbances in this study relative to that in other series10,16,23 might be due to two factors: problems inherent in the classification systems because of the nature of the growth disturbance itself and, more importantly, the relatively late appearance of these lesions. Several authors39,40,48 have suggested that the actual prevalence of growth disturbances may vary less than the criteria with which they are defined. For example, Mau et al.24 reported only two instances of avascular necrosis, but sixteen of thirty-three patients were noted to have "transient roentgenographic changes in the femoral heads." Intertrochanteric derotation and adduction (varus) osteotomies, suggesting a valgus deformity of the femoral neck most likely secondary to a type-II lesion, were performed in fifteen patients and were advisable for others24. Bucholz and Ogden6 as well as Kalamchi and MacEwen16 reported that superolateral physeal arrest may not be evident in most patients until six to eleven years after the reduction. Therefore, rates of growth disturbances at less than ten years of follow-up must be regarded as preliminary findings and may not reflect the true prevalence of these lesions. Two studies19,36 with eleven and nineteen years of follow-up, which is comparable with the follow-up in our series, demonstrated a prevalence of type-II physeal arrest of twelve of twenty-two hips and of thirteen of fifteen hips, respectively. These findings reflect the longer follow-up and support the late appearance of these lesions. A high prevalence of type-II changes has also been reported after long-term follow-up of patients who had closed reduction22. Additionally, long-term follow-up14 after an anterolateral approach preceded by traction and with excision of the limbus and subsequent derotation osteotomy demonstrated that the epiphyseal angle became progressively more horizontal in thirty-two (22 per cent) of 147 hips as the hip developed. Although these changes were not classified as type-II growth disturbance, the roentgenograms accompanying the text clearly demonstrated this pattern. That study illustrates our concern regarding the lack of standardization in the classification of growth disturbances of the femoral head and the effect that this can have on the evaluation of outcomes. Because of the inconsistencies in the literature, we are reluctant to attribute high rates of growth disturbance entirely to an anteromedial approach. The role of other factors, such as the procedure for application of the cast, primary disturbance from the dislocation, or some other aspect of the original condition or treatment, is extremely difficult to determine.
NOTE: The authors thank Bradley Fideler, M.D., for his contributions to this investigation.
* No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
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