Surgical Therapy for Congenital Dislocation of the Hip in Patients Who Are Twelve to Thirty-six Months Old

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1 Copyright 984 by The Journal of Bone and Joint Surgers. Incorporated Surgical Therapy for Congenital Dislocation of the Hip in Patients Who Are Twelve to Thirty-six Months Old BY MICHAEL E. BERKELEY, M.D.*, JESSE H. DICKSON, M.D.*, THOMAS E. CAIN, M.D.*, AND MICHAEL M. DONOVAN, M.D.*, HOUSTON, TEXAS ABSTRACT: Over a ten-year period, fifty-one congenitally dislocated hips in forty-one patients, whose ages ranged from twelve to thirty-six months, required open reduction. Supplemental procedures such as derotational osteotomy, pericapsular (Pemberton) osteotomy, and femoral shortening were performed as necessary. All of the patients have been followed for at least two years (average, 6. 1 years) No patient had a significant limp, Trendelenburg gait, or avascular necrosis. Using Severin s classification of radiographic evaluation, twenty-nine hips (57 per cent) were rated as excellent and eighteen hips (35 per cent), as good. In our experience, open reduction of the hip together with correction of acetabular and femoral deformities affords the patient in the one to three-year-old age range an excellent chance of obtaining an anatomically satisfactory hip. The treatment of congenital dislocation of the hip in the older patient who has begun to walk is difficult because of adaptive shortening of the extra-articular soft tissues, acetabular dysplasia, capsular constriction, increased fernoral anteversion, and fixed inversion of the limbs7 2. The most commonly used initial treatment of the congenitally dislocated hip that is not diagnosed until the patient is walking is non-operative. This involves skeletal traction until the femoral head is opposite the acetabulum, followed by a closed reduction under general anesthesia and spicacast immobilization The method is more difficult in the older child, as heavy traction is often necessary to pull the femoral head down to the appropriate level and complete concentric reduction is often not obtained due to interposed capsule, labrum, or fibrous tissue within the acetabulum 82. The hip may be left in a laterally subluxated position in the hope that the femoral head will migrate medially, eroding through the interposed soft tissue into the acetabulum. However, the incidence of persistent subluxation in such patients has been reported to be as high as 37 per cent 2 8. A dysplastic acetabulum that fails to remodel satisfactorily and is too shallow to contain the femoral head adequately will usually require a pelvic osteotomy22. Femoral anteversion in excess of 60 degrees may also require surgical correction2. Avascular necrosis of the femoral head, particularly in the patient who is more than one year old, has been reported to remain a serious and significant * Division of Orthopedic Surgery. Baylor College of Medicine Fannin. Houston, Texas problem despite attempts to improve methods of reduction Much of the literature has indicated that frequent poor results are inevitable in the treatment of the older child with a dislocated hip79. In 1969, the Hip Clinic of the Houston Shriners Hospital for Crippled Children developed a protocol for the surgical treatment of all patients more than one year old with congenital dislocation of the hip in whom closed reduction failed to result in a completely reduced and stable hip. The protocol was developed in the hope that an open reduction, combined with the correction of all associated defects of the acetabulum and femur, would provide the patient with a concentrically reduced, congruous hip without the need for subsequent surgical procedures. Materials and Methods The ages of the patients included in this study ranged from twelve to thirty-six months at the time of open reduction. Patients in this age group have significant bone and soft-tissue abnormalities resulting from the dislocated hip, but the hip still possesses a considerable capacity for growth and remodeling20. Operative therapy is generally not mdicated in patients who are less than one year old, since nonoperative methods are usually successful22. Patients who are older than three years pose unique and more serious problems because of the decreased remodeling ability of the hip, and data on such patients are not reported here. Only patients with idiopathic congenital dislocation of the hip were included in the study. Between 1969 and 1980, fifty-four reductions were performed in forty-four patients. Two hips in two patients were successfully treated with closed reduction and were not included. One patient with a unilateral dislocation was lost to follow-up. The remaining fifty-one hips in forty-one patients, all of them treated with open reduction, form the basis of this study. Follow-up ranged from two to twelve years (average, 6. 1 years). The patient population consisted of thirty-eight girls and three boys. Twenty-nine patients were between twelve and twenty-four months old at the time of reduction, the remaining twelve patients being between twenty-four and thirty-six months old. There were fourteen right unilateral dislocations, seventeen left unilateral dislocations, and ten bilateral dislocations. Five of the patients with a unilateral dislocation had a history of dysplasia in the contralateral hip which had been successfully treated by nonoperative means before they were one year old. During the ten-year period over which this study was 412 THE JOURNAL OF BONE AND JOINT SURGERY

2 SURGICAL THERAPY FOR CONGENITAL DISLOCATION OF THE HIP 413 conducted, only two hips in patients in this age range were successfully treated with closed reduction, both of which were excluded from the study. Closed reduction under general anesthesia was initially attempted in thirty-one of the fifty-one hips in this series. These thirty-one hips had all received from six to thirty-five days (average, fifteen days) of preoperative skin or skeletal traction. The criterion for adequate closed treatment was a complete reduction of the femoral head into the acetabulum that was stable through an arc of at least 15 degrees of adduction and abduction, 30 degrees of internal and external rotation, and 45 degrees of flexion and extension from the position of maximum stability. The presence of interposed tissue, either suspected from plain radiographs or proved by arthrography, was an indication for open reduction. Successful closed reduction according to our criteria was not achieved in any of these thirty-one hips and a subsequent open reduction was performed. One patient underwent an attempt at closed reduction without prior traction. This hip was clinically reducible, but an arthrogram at the time of closed reduction demonstrated the presence of a constricted limbus blocking cornplete reduction. No attempt at closed reduction was made in the remaining nineteen hips, for the following reasons: ( 1 ) a history of recent failed closed reduction (eight hips), (2) immobilization of the hip in a spica cast following surgery on the opposite hip (six hips), and (3) unspecified reasons (five hips). These nineteen hips received no traction prior to open reduction. Since radiographic analysis of the young child s hip is largely unsatisfactory due to the predominance of cartilage, a specific preoperative surgical plan for each hip could not be made. The surgical plan was based on the intraoperative assessment of femoral head coverage and femoral anteversion. The hip is approached anteriorly, curving the incision slightly more medially than in the standard iliofemoral approach in order to facilitate exposure of the inferomedial portion of the capsule. The capsule is exposed over an area of about 280 degrees from posterosuperior to posteroinferior, which always requires sectioning of the psoas tendon. The capsule is then opened one centimeter from the acetabular rim, and a perpendicular cut is made extending to the base of the neck in the anterosuperior part of the capsule. It is crucial to detach the inferomedial part of the capsule from the inferior acetabular rim as well as transect the transverse acetabular ligament. Failure to perform this portion of the procedure leaves a bridge of soft tissue over the inferior section of the acetabulum, which prevents reduction of the femoral head into the inferomedial quadrant. The ligamentum teres is also detached from the femoral head and from its attachment to the inferior acetabular inlet. The acetabulum is then inspected. In two hips a fibrocartilaginous membrane overlying the acetabulum had to be removed before the underlying true acetabulum was revealed. The glenoid labrum is usually found to be rolled over the rim of the acetabulum along its posterior and superior borders, and is incised in order to allow easy reduction of the femoral head into the acetabulum. If reduction of the hip places excessive pressure on the femoral head, a femoral shortening procedure is performed. The proximal end of the femur is exposed either by extending the incision distally and laterally or by making a separate lateral approach. The femur is then osteotomized at the level of the lesser trochanter and is shortened by resecting a two to three-centimeter portion of the shaft. The osteotomy site is internally fixed with a four-hole smallfragment plate. A shortening of two to three centimeters was found to be necessary to allow easy reduction of the femoral head while maintaining normal soft-tissue tension across the hip. Femoral anteversion in excess of 60 degrees as determined at the time of open reduction is considered an mdication for derotational osteotomy. Since the open reductions were performed by relatively inexperienced resident house staff, the operations were often prolonged and time constraints frequently dictated that the derotational osteotomy be deferred and done as a separate procedure, usually six weeks later. We do not recommend this approach to the more experienced pediatric hip surgeon. Once satisfactory reduction of the hip has been achieved, the coverage of the femoral head by the acetabulum is assessed. If the anterolateral aspect of the head remains uncovered after the femur has been internally rotated to correct for anteversion, a pericapsular osteotomy is performed as described by Pemberton. Capsulorrhaphy is performed by advancing the superior part of the capsule medially and suturing it firmly to the anterior rim of the acetabulum with number- 1 non-absorbable sutures. After routine wound closure, the patient is placed in a one and one-half hip spica with the hip in 20 degrees of flexion, 30 degrees of abduction, and 30 degrees of internal rotation. The hip is immobilized for a total of twelve weeks. The patient is then allowed to walk in an abduction brace. The brace is worn continuously for six weeks, and then is gradually discontinued over an additional six-week period. All surgery was performed by resident house staff with the senior one of us (J. H. D.) in attendance. In addition to the open reduction, thirty-four (85 per cent) of the hips required a derotational osteotomy, twenty-eight (55 per cent) required a Pemberton osteotomy, and two (4 per cent) required a femoral shortening procedure. The patients were scheduled to return to the outpatient clinic at three-month intervals during the first two years after surgery and then at yearly intervals. The patients were evaluated clinically during each visit as to the range of motion of the affected hip, the quality of gait, and the presence of any pain. Radiographs of each hip were made to assess the quality of reduction, the acetabular index, and the presence or absence of avascular necrosis using the criteria of Salter et al. #{176}. Each patient s preoperative radiographs were evaluated to determine the affected hip s acetabular index and On the final evaluation, a clinical assessment of all VOL. 66-A, NO. 3. MARCH 1984

3 414 M. E. BERKELEY, J. H. DICKSON, T. E. CAIN, AND M. M. DONOVAN patients was done by the junior one of us (M. E. B.) using a variation of McKay s criteria, as follows: excellent - a painless, stable hip without a limp or positive Trendelenburg sign, with more than 15 degrees of internal rotation and otherwise normal motion; good - a painless. stable hip with a slight limp or decreased motion, and a negative Trendelenburg sign; fair - a positive Trendelenburg sign, minimum pain, and moderate stiffness; and poor - significant pain. A determination was also made as to the presence of any limb-length or thigh-circumference discrepancy. A subjective assessment of the cosmetic appearance of the surgical scars was also made. The final anteroposterior radiographs of each hip were graded using Severin s classification 7. as follows: Class I (excellent) - a congruous hip with no deformity and a normal center-edge angle (Fig. 1-B); Class II (good) - HG. I-A Preoperative radiograph of a seventeen-month-old girl who had an open reduction of the right hip following one week of traction and a failed attempt at closed reduction. Radiograph made twelve years postoperatively. demonstrating the virtually normal appearance of the right hip. THE JOURNAL OF BONE AND JOINT SURGERY

4 SURGICAL THERAPY FOR CONGENITAL DISLOCATION OF THE HIP 415 minimum deformity of the femoral head or acetabulum with a normal center-edge angle (Fig. 2-B): Class III (fair) - either a moderate dysplasia of the head or acetabulum or a center-edge angle of less than 20 degrees. or both (Figs. 3-B and 4-B): Class IV (poor) - subluxation ofthe femoral head; and Class V (failure) - dislocation of the hip. Results On the final clinical evaluation, forty-one (80 per cent) of the hips were rated as excellent and ten (20 per cent), as FIG. 2-A Preoperative radiograph of a fourteen-month-old girl who had an open reduction and Pemberton osteotomy of the right hip following three weeks of traction and a failed attempt at closed reduction. A radiograph made 7.5 \ears later demonstrates valgus angulation of the femoral neck with minimum deformity of the femoral head and adequate coverage. VOL. 66-A, NO. 3. MARCH 1984

5 416 M. F. BERKELEY. J. H. DICKSON, T. E. CAIN, AND M. M. DONOVAN good by McKay s criteria. No patient had a significant limp. a positive Trendelenburg sign. or pain other than mild discomfort with strenuous activity. Twenty-nine (57 per cent) of the hips were rated as Severin Class 1: eighteen (35 per cent). as Class II: and four (8 per cent), as Class Ill. There were no Class-IV or Class- V hips. There was no significant difference in the final radiographic evaluation between the hips that had had a pelvic osteotomy and those that had not. However, two of the Class-I hips, which had inadequate acetabular development following open reduction. subsequently had a Salter innominate osteotomy to obtain adequate coverage. In the hips that had had a Pemberton osteotomy no premature closure of the triradiate cartilage was noted. z.,.. FIG. 3-A Preoperative radiograph of a twenty-month-old girl who had an open reduction and Pemberton osteotomy following three weeks of traction and a failed attempt at closed reduction. The temoral head was noted to be inappropriately large at the time of surgery. FIG. 3-B A radiograph made nine years later shoss an enlarged fetiioral head with poor acetahular coverage and persistent anteversion of the neck. THE JOURNAL OF BONE ANt) JOINT SURGERY

6 SURGICAL THERAPY FOR CONGENITAL DISLOCATION OF THE HIP 417 By the criteria of Salter et al. #{176}, there were no hips with avascular necrosis. The ossific nucleus ofeach femoral epiphysis continued to grow after surgery. One Class-Ill hip, however, did demonstrate flattening of the medial fernoral epiphysis, which may indicate partial avascular necrosis (Fig. 4-B)5. Preoperatively. thirteen hips were at Station - 1 and thirty-seven, at Station 0. Radiographs made before and after the period of traction usually did not demonstrate a significant improvement in the station of the hips. The only successful use of traction occurred in one hip which. after thirty-five days of skeletal traction, moved from Station 0 to Station + 1. The two hips that required femoral shortening (in the same eighteen-month-old patient) were both at Station -1. The preoperative acetabular indices ranged from 29 to Preoperative radiograph of a twenty-two-month-old girl who had open reduction following twelve days of traction and a failed attempt at closed reduction. FIG. 4-B A radiograph made five years postoperatively demonstrates acetabular irregularity and flattening of the medial femoral epiphysis. VOL. 66-A, NO. 3. MARCH 1984

7 418 M. E. BERKELEY, J. H. DICKSON, T. E. CAIN, AND M. M. DONOVAN 55 degrees (average, 40 degrees) in the twenty-eight hips that had had a Pemberton osteotomy and ranged from 22 to 50 degrees (average, 37.5 degrees) in the twenty-three hips that had not had a pelvic osteotomy. The acetabular indices on the last examination ranged from zero to 25 degrees (average, 13 degrees) for the pelvic osteotomy group and from 5 to 30 degrees (average, 16 degrees) in the group that did not have a pelvic osteotomy. There were no intraoperative or postoperative complications. There were no deaths. deep wound infections, or cases of redislocation of the hip. Seven femoral fractures occurred while the child was walking in an abduction brace. Five were in the supracondylar region and two were just distal to a plate on the femur. All fractures healed with nonoperative treatment. Eighteen (58 per cent) of the patients with a unilateral dislocation had clinically measurable overgrowth of the ipsilateral femur. in the patients who had not had a derotational osteotomy. the overgrowth was no more than one centimeter. However. the patients who did have a derotational osteotomy demonstrated overgrowth of as much as three centimeters. In twenty-five (81 per cent) of the unilaterally dislocated hips, the diameter of the femoral head was two to ten millimeters more than on the opposite side. The thigh circumference was routinely one to two centimeters less on the side that had been operated on in patients with a unilateral dislocation. In nine of the patients with bilateral dislocation, no significant difference in femoral length, fernoral head diameter, or thigh circumference was noted between the two extremities. The exception was a patient who had sustained two fractures of the left femur and had 1.5 centimeters of shortening. The cosmetic appearance of the scars on the lateral aspect of the thigh secondary to derotational osteotomy were rated as fair or poor in 85 per cent of the patients. The appearance of the scars from the anterior approach to the hip were rated as good or excellent in 84 per cent of the patients. Discussion In the 1960 s. the treatment of congenital dislocation of the hip improved markedly. Prior to this period the incidence of avascular necrosis involving the femoral head was as high as 70 per cent following reduction4. The various buttress and shelfprocedures that were then in use frequently failed to correct the unstable hip 4. Avascular necrosis has come to be understood as a largely iatrogenic entity and emphasis has been placed on release of soft-tissue tension by such means as traction or femoral shortening #{176}. As a result. the incidence of avascular necrosis has been reported to be as low as 5 per cent after closed treatment and zero per cent after open reduction #{176}. The recognition that the acetabular defect lies anteriorly has resulted in the development of pelvic osteotomies that address this abnormality 4 5. However, since these improvements in technique there have been few reports of comprehensive approaches to the treatment of congenital dislocation of the hip that is not diagnosed until the patient is past walking age. We question whether a non-operative approach to the congenitally dislocated hip in patients who are more than one year old can be regarded as truly conservative. From a review of the literature, it is apparent that closed reduction must be preceded by a long period of preoperative traction in order to minimize the risk of avascular necrosis2. Also, most patients who have a closed reduction eventually undergo at least one additional surgical procedure which requires further immobilization, risks, and expense to the patient22. Only three of our patients required an additional operative procedure following the initial surgical treatment. Subluxation is not an uncommon problem following closed reduction Even after an apparently successful closed reduction, an arthrogram or computerized axial-tomography often shows the femoral head to be laterally subluxated due to the presence of interposed tissue 52. The treating physician must then wait expectantly for the femoral head to migrate medially by eroding through the interposed tissue No hip in our series was either dislocated or subluxated at follow-up. Inadequate acetabular development has been reported to be a common problem following open or closed reduction of the congenitally dislocated hip. Lindstrom et al. reported that the remodeling potential of the acetabulum is diminished in hips treated with closed reduction in children who are more than one year old. Gibson and Benson, in a longterm follow-up study of dislocated hips that were treated with open reduction in children between the ages of one and three years, reported that more than half of the hips demonstrated inadequate acetabular development. Staheli et al. reported similar findings in hips that were treated with closed reduction. We performed a pelvic osteotomy at the time of the initial open reduction in hips that we judged to be at risk for later inadequate acetabular development. This decision was based on an intraoperative rather than radiographic evaluation of coverage of the femoral head. We have observed that the preoperative acetabular index bears little relation to actual acetabular coverage of the femoral head. The hips that we judged to be adequately covered at the time of open reduction had an average preoperative acetabular index of37.5 degrees. while those that we judged to have inadequate coverage had an average preoperative acetabular index of 40 degrees. We believe that the acetabular index in the younger patient is only an indirect indicator of the acetabular coverage of the femoral head, since only the ossified portions of the acetabulum are visualized. Also, the anatomical acetabular defect in congenital dislocation is anterolateral, whereas the radiographic acetabular index is an indicator of superior acetabular development. We have observed that the femoral head in the dislocated hip is often enlarged at the time of open reduction. Only at surgery can the adequacy of an acetabulum be accurately judged relative to the size of the corresponding femoral head. On final follow-up, twenty-six (93 per cent) of the hips that had had a Pemberton osteotomy had adequate coverage. THE JOURNAL OF BONE AND JOINT SURGERY

8 SURGICAL THERAPY FOR CONGENITAL DISLOCATION OF THE HIP 419 However, all but three of the hips that had been treated by open reduction without pelvic osteotomy were subsequently noted to have adequate acetabular development as well. We therefore believe that our method of intraoperative assessment is reasonably accurate in selecting hips that are at risk for inadequate acetabular development, and that the Pemberton osteotomy is effective in their treatment. None of the hips that had had a Pemberton osteotomy had growth arrest ofthe triradiate cartilage. On final followup, the radiographic and clinical evaluation of the hips that had been treated with a Pemberton osteotomy was virtually identical to that of the hips that had been treated without a pelvic osteotomy. This is in support of other reports that stated that the Pemberton osteotomy. when properly performed, achieves correction of the acetabular deficiency without subsequent abnormal development 0 4. Avascular necrosis of the femoral head is the most serious complication in the treatment of congenital dislocation of the hip and inevitably results in deformity and later degenerative arthritis3. Several authors have reported that traction should be used to pull a dislocated hip to Station + 2 (the femoral head distal to its normal position) prior to closed reduction, in order to minimize the risk of avascular necrosis25. However, there have been no reports that this position can routinely be achieved in the patient with a dislocated hip who is more than one year old. We have observed that neither skin nor skeletal traction is usually able to significantly improve the initial position of a dislocated hip in these patients. No avascular necrosis of the femoral head was identified in our series. This is in agreement with reports of a generally lower incidence of avascular necrosis after open reduction 9. This is probably because surgical softtissue releases are more effective than traction in reducing pressure on the femoral head. The only possible vascular compromise in our series was a flattening of the medial femoral epiphysis in a twenty-two-month-old child who underwent twelve days of preoperative traction (Fig. 4-B). However, this femoral head was noted to be previously deformed at the time of open reduction, possibly secondary to weight-bearing on the dislocated hip prior to diagnosis. With appropriate soft-tissue releases, it was necessary to employ femoral shortening in only two hips. This is in contrast to our experience with children who are more than three years old, in whom femoral shortening is frequently required. Closed reduction of the dislocated hips reported here was rarely successful because of the presence of interposed tissue within the hip and contracture of the periarticular soft tissues. Consequently, we no longer attempt closed reduction in the patient with a dislocated hip who is past walking age. On final follow-up, overgrowth of the femoral head was observed in most patients. The enlargement of the femoral head was concentric and did not appear to interfere with the congruity of the joint, although two hips were rated as Severin Class III because the acetabulum did not adequately cover the enlarged head. One of these two hips was found to have an enlarged head at the time of open reduction (Fig. 3-B). Overgrowth of the ipsilateral femoral shaft of as much as three centimeters was present in most patients who had had a derotational osteotomy. This is probably the result of increased blood flow to the epiphyses such as may be observed following femoral shaft fractures in children. Since overgrowth of an extremity effectively decreases ipsilateral acetabular coverage of the femoral head, we now perform prophylactic femoral shortening of one centimeter at the time of derotational osteotomy. Long-term evaluation of the results of treatment of congenital dislocation of the hip cannot truly be made until the hip has performed throughout a lifetime. Clinical results in children, no matter how encouraging, do not correlate with a good ultimate result, since children can tolerate significant deformity without having pain or a limp6 5. Nevertheless, it is reasonable to predict the future of a hip according to its radiographic appearance after a suitably long follow-up period. The Severin classification is a stringent system for making such an evaluation. An excellent rating is given only to a hip with normal architecture that can be expected to last a lifetime without degenerative changes. A good result is assigned to a hip with minor deformities whose future is less certain but still optimistic. Any further deformity cannot be expected to result in a painless, stable hip in the long run. By Severin s criteria, 92 per cent of the hips in this series were rated as good or excellent. The remaining hips either were adequately contained with incongruous joint surfaces or were poorly covered and in need of an additional procedure to obtain coverage. In our experience, open reduction of the congenitally dislocated hip with correction of acetabular and femoral deformities produces satisfactory results in the child who is past walking age. We believe that this aggressive approach is justified, since the results are at least as good as those of any previously reported series. References 1. ASHLEY. R. K.: LARSEN. L. J.: and JAMES, P. M.: Reduction of Dislocation of the Hip in Older Children. J. Bone and Joint Surg.. 54-A: , April BUCHANAN. J. R.; GREER, R. B.. III; and COTLER. J. M.: Management Strategy for Prevention of Avascular Necrosis during Treatment of Congenital Dislocation of the Hip. J. Bone and Joint Surg.. 63-A: , Jan COOPERMAN. D. R.: WALLENSTEN. RICHARD; and STULBERG, S. D.: Post-Reduction Avascular Necrosis in Congenital Dislocation of the Hip. Long-Term Follow-up Study of Twenty-five Patients. J. Bone and Joint Surg.. 62-A: March ESTEVE, RAFAEL: Congenital Dislocation of the Hip. A Review and Assessment of Results of Treatment with Special Reference to Frame Reduction as Compared with Manipulative Reduction. J. Bone and Joint Surg., 42-B(2): GAGE. J. R.. and WINTER. R. B.: Avascular Necrosis of the Capital Femoral Epiphysis as a Complication of Closed Reduction of Congenital Dislocation of the Hip. A Critical Review of Twenty Years Experience at Gillette Children s Hospital. J. Bone and Joint Surg.. 54-A: , March VOL. 66-A, NO. 3. MARCH 1984

9 420 M. E. BERKELEY, J. H. DICKSON, T. E. CAIN, AND M. M. DONOVAN 6. GIBSON. P. H., and BENSON. M. K. D.: Congenital Dislocation of the Hip. Review at Maturity of 147 Hips Treated by Excision of the Limbus and Derotation Osteotomy. J. Bone and Joint Surg.. 64-B(2): , HARROLD, A. J.: Problems in Congenital Dislocation of the Hip. British Med. J.. 1: LINDSTROM. J. R. ; PONSETI. I. V.: and WENGER. D. R.: Acetabular Development after Reduction in Congenital Dislocation of the Hip. J. Bone andjointsurg.,61-a: 112-1l8.Jan LLOYD-ROBERTS, G. C.. and SWANN, MALCOLM: Pitfalls in the Management of Congenital Dislocation of the Hip. J. Bone and Joint Surg., 48-B(4): , MCKAY. D. W. : A Comparison of the Innominate and the Pericapsular Osteotomy in the Treatment of Congenital Dislocation of the Hip. Clin. Orthop.. 98: I I. MITCHELL. G. P.: The Subluxating Hip following Treatment for Congenital Dislocation. In Congenital Dislocation of the Hip. pp Edited by M. 0. Tachdjian. New York. Churchill Livingstone MOREL, GEORGES: The Treatment of Congenital Dislocation and Subluxation of the Hip in the Older Child. Acta Orthop. Scandinavica, 46: , OGDEN, J. A.: Normal and Abnormal Circulation. In Congenital Dislocation of the Hip, pp Edited by M. 0. Tachdjian. New York, Churchill Livingstone, PEMBERTON, P. A. : Pericapsular Osteotomy of the Ilium for Treatment of Congenital Subluxation of the Hip. J. Bone and Joint Surg., 47-A: Jan SALTER. R. B.: Innominate Osteotomy in the Treatment of Congenital Dislocation and Subluxation of the Hip. J. Bone and Joint Surg., 43-B(3): , SALTER, R. B.; KOSTuIK, J.: and DALLAS, S.: Avascular Necrosis of the Femoral Head as a Complication of Treatment for Congenital Dislocation of the Hip in Young Children: A Clinical and Experimental Investigation. Canadian J. Surg.. 12: 44-61, SEVERIN, ERIK: Contribution to the Knowledge of Congenital Dislocation of the Hip Joint. Late Results of Closed Reduction and Arthrographic Studies of Recent Cases. Acta Chir. Scandinavica. Supplementum SEVERIN, ERIK: Congenital Dislocation of the Hip. Development of the Joint after Closed Reduction. J. Bone and Joint Surg.. 32-A: July SIMONS, G. W.: A Comparative Evaluation of the Current Methods for Open Reduction of the Congenitally Displaced Hip. Orthop. Clin. North America, 11: SOMERVILLE, E. W.: Results of Treatment of 100 Congenitally Dislocated Hips. J. Bone and Joint Surg.. 49-B(2): SOMERVILLE. E. W., and SCOTT, J. C.: The Direct Approach to Congenital Dislocation of the Hip. J. Bone and Joint Surg.. 39-B(4): , STAHELI, L. T.: DION, MARY: and TUELI.. J. I.: The Effect of the Inverted Limbus on Closed Management of Congenital Hip Dislocation. Clin. Orthop.. 137: , WEINER, D. S.; HOYT. W. A., JR. : and ODELL. H. W.: Congenital Dislocation of the Hip. The Relationship of Premanipulation Traction and Age to Avascular Necrosis of the Femoral Head. J. Bone and Joint Surg., 59-A: , April THE JOURNAL OF BONE AND JOINT SURGERY