The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 84, Issue 2

Scientific Article | February 01, 2002

Long-Term Results of Total Hip Arthroplasty with a Cemented Custom-Designed Swan-Neck Femoral Component for Congenital Dislocation or Severe Dysplasia : A Follow-up Note

Frank DiFazio, MD; Won Yong Shon, MD; Eduardo A. Salvati, MD; Philip D. WilsonJr., MD

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Investigation performed at The Hospital for Special Surgery, New York, NY

Frank Di Fazio, MD
1290 Summer Street, Stanford, CT 06905. E-mail address: difaz@worldnet.att.net

Won Yong Shon, MD
Guro Hospital, #80 Guro-Dong Guro-Ku, Seoul 152-050, Korea. E-mail address: wonyong@ns.kumc.eo.kr

Eduardo A. Salvati, MD
Philip D. Wilson Jr., MD
The Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021. E-mail address for E.A. Salvati: salvatie@hss.edu. E-mail address for P.D. Wilson: wilsonp@hss.edu

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Dr. and Mrs. Alberto Foglia. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

J Bone Joint Surg Am, 2002 Feb 01;84(2):204-207

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Abstract

Background: This follow-up study updates the results in a consecutive series of nineteen cemented total hip replacements with a swan-neck femoral component in patients with congenital dislocation or severe hip dysplasia. The series was previously reported on in 1993.

Methods: The patients were petite, with an average height of 152 cm and an average weight of 50 kg, and the femoral canals could not accommodate an off-the-shelf femoral component. Sixteen of the nineteen hips were available for follow-up at an average of 13.3 years (range, eleven to twenty years). Fourteen hips had up-to-date clinical and radiographic examinations.

Results: At the time of the latest follow-up, thirteen hips were rated as excellent; two, as good; and one, as a failure because of loosening of both components requiring revision eleven years after the index operation. Another hip required acetabular revision because of loosening fifteen years after the index operation. The rates of femoral and acetabular component revision were 6% and 12.5%, respectively. Radiographic analysis demonstrated that no femoral component was loose. One cup was definitely loose at 19.5 years, and three cups were possibly loose at an average of fourteen years. The radiographic rate of acetabular loosening was 33%. The total rate of cup failure (radiographic loosening and revision) was 43%.

Conclusions: The excellent clinical and radiographic results associated with the swan-neck femoral component, and the 94% rate of survival, at an average of 13.3 years (range, eleven to twenty years) indicate that the biomechanical objectives of this custom-designed prosthesis for patients with congenital dislocation or severe hip dysplasia were met. On the basis of this favorable long-term experience, we still use this prosthesis when the anatomic abnormality cannot be adequately addressed by use of a commercially available prosthetic component.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

In 1993, we reported the early results of arthroplasties performed with insertion of a custom-designed swan-neck femoral component with cement in a consecutive series of nineteen hips (fourteen patients) that had congenital dislocation or severe dysplasia and a femoral canal that would not accommodate an off-the-shelf prosthesis¹. The custom implants were specifically designed with a varus neck to preserve bone stock in the proximal part of the femur and to restore offset and limb length. The size of the stem was individualized, on the basis of plain radiographs, so as to allow approximately 2 mm for a cement mantle while maintaining adequate strength.

After an average duration of follow-up of six years (range, two to nine years), eighteen of the nineteen arthroplasties had an excellent result and one had a good result. There were no revisions. The present study updates the results for sixteen of the original group of nineteen hips after an average duration of follow-up of 13.3 years (range, eleven to twenty years).

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Fig. 1-A:: Fig. 1-A Radiograph demonstrating severe arthritis, a sequela of the treatment of congenital dislocation.

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Fig. 1-B:: Fig. 1-B Fifteen-year follow-up radiograph showing good incorporation and survival of the autogenous superolateral acetabular bone graft and intact position and fixation of both prosthetic components. The swan-neck femoral component restored limb length, offset, and the abductor lever arm.

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Eleven patients (sixteen arthroplasties) from the original series¹ were available for long-term follow-up. Five patients had a bilateral total hip replacement. The primary diagnoses were congenital dislocation in seven patients (ten hips), achondroplasia in one patient (two hips), spondyloepiphyseal dysplasia in two patients (three hips), and congenital coxa vara in one patient (one hip). According to the classification system of Crowe et al.², two hips were Type I, two were Type II, six were Type III, and six were Type IV. All of the operations were performed or supervised by the senior authors at The Hospital for Special Surgery between January 1981 and October 1987. The average duration of follow-up was 13.3 years (range, eleven to twenty years).

All of the patients were women. At the time of the operation, the average age was forty-six years (range, thirty-five to seventy-three years), the average height was 152 cm (range, 124 to 165 cm), and the average weight was 50 kg (range, 37 to 61 kg).

All reconstructions were performed through a transtrochanteric approach. Autogenous femoral head grafts were used to provide superolateral acetabular coverage in five hips. There were eleven all-polyethylene sockets and five preassembled metal-backed sockets. Eleven cups had an outer diameter of 36 mm; four, 40 mm; and one, 43 mm. All cups were cemented. The acetabulum was prepared with pulsatile lavage, anchoring holes, and digital pressurization of cement. All prosthetic heads were 22 mm in diameter and were cemented with use of a distal plug, pulsatile lavage, and retrograde injection of cement with a gun and pressurization. No intraoperative fractures occurred.

Up-to-date clinical information and results of a physical examination were available for ten patients (fourteen hips). The clinical result was scored with use of the hip rating system of The Hospital for Special Surgery, with which pain, walking, motion, and function are evaluated on a scale of 0 to 10 points, with 10 points being the best³. One patient (two hips) was unable to return for follow-up, and no recent radiographs were available. However, she was interviewed by telephone, and the hip was scored accordingly.

Up-to-date radiographs were available for fourteen hips. Standard anteroposterior and lateral radiographs made at the most recent follow-up examination were compared with the first postoperative radiographs of good quality and with the ones made at the time of the previous study¹. Fixation of the acetabular and the femoral component was assessed with the criteria of Harris and Penenberg⁴ and those of Harris and McGann⁵, respectively. Heterotopic ossification was evaluated according to the grades defined by Brooker et al.⁶. The location of any femoral osteolysis was classified according to the zones described by Gruen et al.⁷, and the size of the lesion was measured in millimeters.

Results

Introduction | Materials and Methods | Results | Discussion | References

Clinical Results

The mean preoperative hip score of the sixteen hips that were followed was 16 points (range, 15 to 22 points), according to the rating system of The Hospital for Special Surgery³. At the most recent follow-up examination, the mean score was 35 points (range, 31 to 38 points). Thirteen hips were rated as excellent, two hips were rated as good, and one was considered a failure. Two hips required revision surgery because of loosening eleven and fifteen years after the index operation; both components were loose in one hip (the failure), and only the cup was loose in the other.

Radiographic Results

The femoral and acetabular components of fourteen of the fifteen surviving replacements were evaluated radiographically. At a mean of 13.4 years, all five acetabular bone grafts had united without resorption (Figs. 1-A and 1-B). One acetabular component was definitely loose at 19.5 years, and three cups were possibly loose at an average of fourteen years; despite these radiographic findings, all of these patients had an excellent clinical rating at the most recent follow-up examination. The prevalence of acetabular component loosening was 33%. With the small numbers available, no association could be established between cup failure and the outer diameter of the acetabular component, the type of cup (all-polyethylene or metal-backed), or the presence or absence of supplemental acetabular bone graft.

Radiographic evaluation of the femoral components showed that all trochanteric osteotomy sites had healed without proximal migration. No femoral component was considered to be loose by radiographic criteria. A focal femoral osteolytic lesion was present in three hips; two lesions, measuring 5 20 mm and 5 3 mm, were located in Gruen zone 3, and one, measuring 25 5 mm, was in Gruen zone 5⁷. The clinical scores were excellent in these patients. There was grade-I heterotopic ossification in two hips.

The average preoperative length of the effective lever arm of the abductor mechanism for the affected hip was 32 mm (range, 24 to 48 mm). Postoperatively, this measurement had increased to an average of 47 mm (range, 42 to 52 mm), an average gain of 15 mm, or 47%. The difference between the preoperative and postoperative measurements was significant (p < 0.01).

Limb length was equalized to within 5 mm in all patients except one, who had had a preoperative discrepancy of 50 mm and had a residual discrepancy of 20 mm.

Complications

There were no fractures, perforations, nerve palsies, or infections. An early dislocation, which was reported in the original study, was treated successfully with closed reduction.

Revision Surgery

One hip required revision of both components because of aseptic loosening eleven years after the index operation. Another hip required revision of a loose cup fifteen years postoperatively; the stem was well fixed and was left intact. The prevalence of femoral and acetabular component revision was 6% and 12.5%, respectively, and the prevalence of cup failure (radiographic loosening and revision) was 43%.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

The anatomic abnormalities in congenital dislocation and severe dysplasia of the hip present complex reconstructive problems. The proximal part of the femur is hypoplastic, deformed, and markedly anteverted, and the femoral canal is narrow. The greater trochanter is located posteriorly, thus reducing the abductor lever arm. This group of patients has had higher complication rates and less successful clinical results than have patients treated with total hip replacement because of primary osteoarthritis^8,9.

We used a custom-designed swan-neck prosthesis when, during preoperative planning with templates, it was determined that an off-the-shelf prosthesis would not fit the medullary canal so as to allow for a minimum 1.5 mm of cement mantle thickness. We also used this prosthesis when standard prostheses could not provide the appropriate offset or restore the proper length of the lower limb or when it would not be possible to maintain sufficient proximal bone stock if a standard prosthesis were used. During the period of the original study, approximately one patient in three who had congenital hip dislocation or severe hip dysplasia met these criteria and received a custom-designed swan-neck prosthesis.

To our knowledge, the current series represents the longest follow-up of cemented, custom-designed femoral prostheses for the treatment of congenital dislocation or severe dysplasia of the hip. The excellent clinical and radiographic results, with a 94% rate of survival of the femoral prosthesis, at an average of thirteen years indicate that the biomechanical objectives of the custom-designed swan-neck femoral component had been met. The limb lengths and abductor lever arms were equalized or significantly improved in all patients.

In order to provide stability and to improve the abductor lever arm, all of the operations were performed through a transtrochanteric approach. All osteotomy sites healed without nonunion or proximal migration of the greater trochanter. Currently, we do not osteotomize the greater trochanter; rather, we restore stability by creating adequate tension of the soft tissues, which is determined by the height of the femoral neck cut and by the neck length of the modular swan-neck prosthesis.

The high rate of mechanical failure of the cemented acetabular components is disappointing. However, it reflects the limitations imposed by the hypoplastic acetabulum and is consistent with the experience of others^9-11. It has been shown that superior positioning, even without lateral displacement, increases the rate of loosening¹². In our series, all acetabular components were placed at the level of the true acetabulum. The true acetabulum is osteopenic and hypoplastic, allowing implantation of only a small-outer-diameter and thin plastic cup. Thus, only 22-mm prosthetic heads were implanted to maximize plastic thickness. The contact stresses in the polyethylene increase exponentially as the thickness decreases¹³. While the surgeon can increase the superolateral coverage of a dysplastic acetabulum with an autologous femoral head graft¹⁴, the real anatomic limitation is the deficient anteroposterior dimension.

Because of the anteversion of the femoral neck, the dysplastic acetabulum has a thicker posterior wall and a thin and deficient anterior wall. Accordingly, reaming should be first directed posteromedially to prevent violation of the already deficient anterior wall. The hypoplastic anterior wall may induce the surgeon to place the cup in excessive anteversion, a position that could favor anterior dislocation, particularly when the femoral component is also placed in anteversion because of the antetorsion of the proximal part of the femur.

Despite the high rate of acetabular loosening, most patients had a satisfactory clinical result, a finding that emphasizes the limited functional demands of these petite patients who had abnormal hips since birth. Furthermore, they are frequently affected by osteoarthritis of the lumbosacral spine and ipsilateral knee. In another series, we are following the results of arthroplasties with a cementless modular cup in patients with this disorder. Our intermediate-term impression is that the fixation of the metallic shell is excellent and long-lasting¹⁵. However, the increasing prevalence of wear, osteolysis, and dislodgment of the plastic liner is of concern¹⁶.

The present study reflects the experience of the 1980s. Since then, the number of commercially available implants has increased, providing a wide variety of stem designs, sizes, modularity, surface finishes, and metaphyseal and diaphyseal fit. However, we still use the custom-designed swan-neck cemented femoral component when the anatomic abnormality cannot be adequately addressed with a commercially available prosthetic component.

References

Introduction | Materials and Methods | Results | Discussion | References

Huo MH, Salvati EA, Lieberman JR, Burstein AD,Wilson PD Jr. Custom-designed femoral prostheses in total hip arthroplasty done with cement for severe dysplasia of the hip. J Bone Joint Surg Am,1993;75: 1497-504. 751497 1993 [PubMed]

Crowe JF, Mani VJ,Ranawat CS. Total hip replacement in congenital dislocation and dysplasia of the hip. J Bone Joint Surg Am,1979;61: 15-23. 6115 1979 [PubMed]

Salvati EA,Wilson PD Jr. Long-term results of femoral-head replacements.. J Bone Joint Surg Am,1973;55: 516-24. 55516 1973 [PubMed]

Harris WH,Penenberg BL. Further follow-up on socket fixation using a metal-backed acetabular component for total hip replacement. A minimum ten-year follow-up study. J Bone Joint Surg Am,1987;69: 1140-3. 691140 1987 [PubMed]

Harris WH,McGann WA. Loosening of the femoral component after use of the medullary-plug cementing technique. Follow-up note with a minimum five-year follow-up. J Bone Joint Surg Am,1986;68: 1064-6. 681064 1986 [PubMed]

Brooker AE, Bowerman JW, Robinson RA,Riley LH Jr. Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am,1973;55: 1629-32. 551629 1973 [PubMed]

Gruen TA, McNeice GM,Amstutz HC. "Modes of failure" of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop,1979;141: 17-27. 14117 1979 [PubMed]

Dearborn JT,Harris WH. Acetabular revision after failed total hip arthroplasty in patients with congenital hip dislocation and dysplasia. Results after a mean of 8.6 years. J Bone Joint Surg Am,2000;82: 1146-53. 821146 2000 [PubMed]

Garvin KL, Bowen MK, Salvati EA,Ranawat CS. Long-term results of total hip arthroplasty in congenital dislocation and dysplasia of the hip. A follow-up note. J Bone Joint Surg Am,1991;73: 1348-54.. 731348 1991 [PubMed]

MacKenzie JR, Kelley SS,Johnston RC. Total hip replacement for coxarthrosis secondary to congenital dysplasia and dislocation of the hip. Long-term results. J Bone Joint Surg Am,1996;78: 55-61. 7855 1996 [PubMed]

Numair J, Joshi AB, Murphy JC, Porter ML,Hardinge K. Total hip arthroplasty for congenital dysplasia or dislocation of the hip. Survivorship analysis and long-term results.. J Bone Joint Surg Am,1997;79: 1352-60. 791352 1997 [PubMed]

Pagnano MW, Hanssen AD, Lewallen DG,Shaughnessy WJ. The effect of superior placement of the acetabular component on the rate of loosening after total hip arthroplasty. J Bone Joint Surg Am,1996;78: 1004-14. 781004 1996 [PubMed]

Bartel DL, Bicknell VL,Wright TM. The effect of conformity, thickness, and material on stresses in ultra-high molecular weight components for total joint replacement. J Bone Joint Surg Am,1986;68: 1041-51. 681041 1986 [PubMed]

Rodriguez JA, Huk OL, Pellicci PM,Wilson PD Jr. Autogenous bone grafts from the femoral head for the treatment of acetabular deficiency in primary total hip arthroplasty with cement. Long-term results. J Bone Joint Surg Am,1995;77: 1227-33. 771227 1995 [PubMed]

Anderson MJ,Harris WH. Total hip arthroplasty with insertion of the acetabular component without cement in hips with total congenital dislocation of marked congenital dysplasia. J Bone Joint Surg Am,1999;81: 347-54. 81347 1999 [PubMed]

Gonzalez Della Valle A, Ruzo PS, Li S, Pellicci P, Sculco TP,Salvati EA. Dislodgment of polyethylene liners in first and second-generation Harris-Galante acetabular components. A report of eighteen cases. J Bone Joint Surg Am,2001;83: 553-9. 83553 2001 [PubMed]

Topics

neck ; dislocations ; femur ; prosthesis implantation ; hip replacement arthroplasty ; dysplasia

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Frank DiFazio, Won Yong Shon, Eduardo A. Salvati, Philip D. WilsonJr.; Long-Term Results of Total Hip Arthroplasty with a Cemented Custom-Designed Swan-Neck Femoral Component for Congenital Dislocation or Severe Dysplasia A Follow-up Note. The Journal of Bone & Joint Surgery. 2002 Feb;84(2):204-207.

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