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Results of Selective Hip Arthroplasty Revision in Isolated Acetabular Failure
Journal of Surgical Research 164, 228–233 (2010) doi:10.1016/j.jss.2009.06.023
Results of Selective Hip Arthroplasty Revision in Isolated Acetabular Failure Chuan He, M.D., Ph.D.,*,† Jian-Min Feng, M.D.,*,1 Qing-Ming Yang, M.D.,*,† Yi Wang, M.D.,* and Zhi-Hong Liu, M.D.* *Department of Orthopedics, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; and †Shanghai Institute of Traumatology and Orthopaedics, Shanghai, China Submitted for publication January 17, 2009
Background. Controversy exists over whether to remove well-fixed components at the time of revision of a failed total hip arthroplasty (THA). The purpose of this study was to evaluate the results of selective acetabular revision after acetabular failure in which only the failed component was replaced. Materials and Methods. Thirty-six isolated acetabular component revisions were performed and prospectively followed for a mean of 4.7 y (range, 2–9.3 y). The components had been in place for a mean of 10.8 y. All femoral components and some metal-backed acetabular shells were well fixed at the time of revision and left in place. Surgery involved cementation of an acetabular liner into a well-fixed acetabular shell in 16 cases, and acetabular revision in 20 cases. Morselized cancellous allograft was used to fill acetabular defects in 27 hips, and proximal femoral defects in 17 hips. Bulk allografts were used to reconstruct the proximal femur in two hips. Results. The mean Harris hip score improved from 57.8 preoperatively to 89.1 at the final follow-up visit. The results were rated excellent in 24 patients, good in nine patients, and fair in three patients. The unrevised femoral components and acetabular shells remained well fixed, and final follow-up radiographs revealed no cases of osteolytic lesion progression around the femoral and acetabular components. Conclusions. Revision of only the failed acetabular component is recommended in cases of isolated acetabular failure, providing excellent results over the medium term, and allowing preservation of bone stock with lower surgical morbidity. Ó 2010 Elsevier Inc. All rights reserved. 1 To whom correspondence and reprint requests should be addressed at Department of Orthopedics, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Rui Jin Er Road, Shanghai 2000025, China. E-mail: [email protected].
0022-4804/$36.00 Ó 2010 Elsevier Inc. All rights reserved.
Key Words: acetabular revision; selective hip arthroplasty revision; stable acetabular shell; cement; acetabular liner; acetabular shell; femoral components.
INTRODUCTION
Revision hip arthroplasty due to wear-induced osteolysis is an increasingly common procedure [1–4]. Debrisinduced osteolysis is an ongoing problem in patients with revision total hip arthroplasty (THA). Polyethylene wear leads to bone loss in areas where the debrisladen joint fluid is pumped toward the interface. Near the acetabulum, these lesions can be large, with access gained through screw holes in the cup or around the periphery of the cup. Lesions can also occur at the proximal femur and around the upper femoral stem. Often, however, the cup or the stem itself is still well fixed through osseointegration. In these cases, the decision must be made whether to routinely replace these well-fixed devices during revision surgery. A common clinical scenario involves a well-fixed metal-backed acetabular shell with a failed polyethylene insert. The failure may be due to polyethylene wear, a defective locking mechanism, or a malpositioned component. Another common situation involves a wellfixed femoral component with a loosening acetabular component. Some reports recommend replacing the entire acetabular component when a liner fails without loosening of the acetabular shell or removing a wellfixed femoral component after revision of the acetabular component [3, 5–7]. Removal of a well-fixed femoral or acetabular component, however, may lead to substantial bone loss and possible fracture or nonunion, greatly complicating an otherwise simple revision.
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HE ET AL.: SELECTIVE HIP ARTHROPLASTY REVISION IN ISOLATED ACETABULAR FAILURE
An alternative is selective revision of the failed component, while leaving the well-fixed components in place [8, 9]. The present study was conducted to evaluate the clinical and radiologic results over the medium term (>2-y follow-up) of selective acetabular revision, while retaining a well-fixed femoral component or a stable acetabular shell. MATERIALS AND METHODS Patient Demographics Between May 1998 and May 2006, 196 hips (173 patients) underwent revision THA in our Orthopedic Department. The average time from primary THA to revision surgery was more than 5 y in 138 hips (117 patients), and revision of the acetabular component alone was performed in 37 hips (37 patients). One patient (one hip) was lost to follow-up after less than 2 y. The remaining 36 hips (36 patients) formed the basis of this study. Of the 36 procedures, 14 were performed in men and 22 in women. The mean patient age at revision surgery was 59.3 y (range, 45–71 y). The mean time from implantation to acetabular component failure was 10.8 y (range, 5.1–13.2 y). The indication for selection revision was painful aseptic loosening of the acetabular component in 17 hips with a well-fixed femoral stem, and dislocation or fracture of the polyethylene inner bearing in 19 hips with a well-fixed acetabular shell and femoral stem. The cases were determined for selection or total revision, based on the stability of components evaluated preoperatively and intraoperatively. If the lesions progressed far enough and the integrity of the bone became compromised, a more typical revision operation was planned even when the component seemed to be securely fixed.
Implant The primary articulation was metal on polyethylene in all 36 cases. There were 34 uncemented acetabular components, and two allpolyethylene acetabular components. On the femoral side, there were 31 uncemented stems and five cemented stems.
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Follow-up Evaluation Clinical results were graded using Harris hip scores (maximum score, 100 points) [10]. Hips with scores ranging from 90 to 100 points were graded as excellent, from 80 to 89 points as good, from 70 to 79 points as fair, and below 70 points as poor. Preoperative and final follow-up radiographs were evaluated for osteolysis, inclination of the acetabular component, stability of the acetabular and femoral components, and hip center correction. We measured the lateral opening angle of the acetabular component on anteroposterior radiographs. The angle formed between the line drawn between the lower end of the teardrop on both sides and the line drawn along the lateral face of the component was measured. To evaluate the hip center, vertical migration was determined with respect to the inferior aspect of the teardrop, and the Ko¨hler line was used to measure horizontal migration. Definite acetabular loosening was defined as a change in the opening angle of the component of more than 4 , or a change in horizontal or vertical position of the component of more than 3 mm. Radiolucent lines were measured using the zones described by DeLee and Charnley [11]. Only cases involving 50% or more of a zone were considered. For the cemented femoral components, fixation was described using the method of Harris and McGann [12]. Definite loosening was defined as a shift in the position of the cement mantle relative to the femur, cement, or stem fracture, or new radiolucent line at the prosthesis-cement interface. Probable loosening was defined as a continuous (100%) radiolucent line at the bone–cement interface without migration. Possible loosening was defined as the presence of a radiolucent line involving between 50% and 99% of the interface. For noncemented components, fixation was defined using the method of Engh et al. [13]. Definite loosening was indicated by subsidence of greater than 5 mm.
Statistical Analysis The Cox proportional-hazards regression model was used to identify univariate and multivariate factors contributing to the differential follow-up results. Preoperative and postoperative scores were compared using paired t-tests. Paired t-tests also were used to assess vertical distances between the center of rotation and the radiographic teardrop and horizontal distances between the center of rotation and the Ko¨hler line in the affected hips after the revision and the normal hips. Significance was determined by P value < 0.05. Statistical analysis was performed with the SPSS software package (version 11.1; SPSS, Chicago, IL).
Operative Procedure Of 19 hips with isolated polyethylene liner failure, three had the well-fixed acetabular shells revised because satisfactory replacement liners were not available, and another 16 hips were treated with cementation of a new polyethylene liner into the original acetabular shell. Acetabulum was reconstructed according to the integrity of the bony socket after the acetabular component was removed if entire acetabular revision was indicated. In brief, the surgical method were as follows: cementation of an acetabular liner into a well-fixed acetabular shell in 16 cases, exchange for a larger uncemented acetabular component in six cases, exchange for an all-polyethylene acetabular component in two cases, acetabular reconstruction with impaction bone grafts and an acetabular reinforcement ring in 11 cases, and acetabular reconstruction with a mesh, impaction bone grafts, and a customized all-polyethylene acetabular component in one case (Fig. 1). Localized pelvic osteolysis was identified in 14 cases, localized femoral osteolysis in 11 cases, and metallosis in association with pelvic and femoral osteolysis in three cases. Morselized cancellous allograft was used to fill acetabular defects in 27 hips, among which impaction bone graft was performed through the enlarged screw holes of the acetabular component in 10 cases of acetabular shell retention. Bone graft was performed at the proximal femur in 17 cases, and bulk allografts were used to reconstruct the proximal femur in two hips.
RESULTS
All 36 patients were prospectively followed for a mean of 4.7 y (range, 2–9.3 y). The mean duration of total implantation time of the unrevised component at the final follow-up was 15.5 y, with a range of 12.6–17.4 years. In none of those cases was a second revision operation necessary because of loosening of the acetabular or femoral component. The mean Harris hip score improved from 57.8 (range, 36–77) preoperatively to 89.1 at the final follow-up visit (range, 74–97) (t ¼ 24.481, P < 0.001). The results were rated excellent in 24 patients, good in nine patients, and fair in three patients; thus, 92% of all patients had excellent or good results. All three of the patients with results rated as fair were cases of entire acetabular component failure who underwent revision with impaction bone grafts and an acetabular reinforcement ring. These
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FIG. 1. (A) Preoperative anteroposterior radiograph of a loose cemented acetabular component in a 69-y-old woman showing bone loss and rigid fixation of the femoral component at the time of revision. (B) Postoperative radiograph showing revision of only the acetabular component with a mesh, impaction bone grafts, and a customized all-polyethylene acetabular component to match the original 32-mm femoral head; trochanteric osteotomy was required for exposure. (C) Five-year postoperative radiograph showing continued good fixation of the acetabular and femoral components. The patient had an excellent clinical result, with a Harris hip score of 92 points.
three patients had associated knee and spine problems, with two having ankylosing spondylitis, and one having degenerative spinal stenosis and knee osteoarthritis. The Cox proportional-hazards regression model revealed that the preoperative Harris hip score (P ¼ 0.003, risk ratio ¼ 5.0, 95% confidence interval ¼ 1.5%–17.5%) was the significant independent predictor of the differential follow-up results. Multivariate results indicated that the surgical method (P ¼ 0.301), the diseases for the primary total hip arthroplasty (P ¼ 0.565), patient gender (P ¼ 0.951), age (P ¼ 0.071), the duration of follow-up (P ¼ 0.133), and the position of the implants (P ¼ 0.169) did not have a statistically significant impact on the rating between ‘‘excellent’’ and ‘‘good.’’
average inclination of the polyethylene liner was 40.9 . The allograft used in hips was considered to have healed, with trabecular bridging seen (Fig. 2). Final follow-up radiographs revealed no measurable polyethylene wear in any of the cases. Before surgery, none of the cemented or noncemented femoral components had definite, probable, or possible loosening as defined by the criteria of Harris and McGann [12]. After surgery, of the remaining five nonrevised cemented femoral components, none subsided or definitely loosened. Of the 31 nonrevised noncemented femoral components, none subsided or showed notable radiolucent lines or osteolysis, and all were classified as stable with bone ingrowth. Complication
Radiographic Evaluation
Final follow-up radiographs revealed no cases of osteolytic lesion progression around the femoral and acetabular components. No acetabular component migrated with regard to hip center correction. The mean distance from the inferior aspect of the teardrop to the center of rotation was 33 mm preoperatively, which was reduced to 21.5 mm postoperatively (t ¼ 10.871, P < 0.001), compared with 20.4 mm on the normal side. The mean distance from the Ko¨hler line to the center of rotation was 36 mm preoperatively, which was corrected to 40 mm postoperatively (t ¼ 2.434, P ¼ 0.02), compared with 41.5 mm on the normal side. The average inclination of the existing shell was 43.6 , with a range of 32 to 57 , and the
One patient who underwent revision with impaction bone grafts and an acetabular reinforcement ring experienced a dislocation, and was successfully treated by closed reduction under general anesthesia and immobilization in a hip spica cast for 6 wk. Instability did not recur. DISCUSSION
We evaluated the results of selective acetabular revision, including liner cementation into a stable acetabular shell using a polyethylene liner and total acetabular revision, for late (>5 y) acetabular failure of THA in 36 hips. Clinical review at a mean of 4.7 y showed excellent or good results in 33 (92%) of the
HE ET AL.: SELECTIVE HIP ARTHROPLASTY REVISION IN ISOLATED ACETABULAR FAILURE
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FIG. 2. (A) Preoperative anteroposterior radiograph of a loose uncemented acetabular component in a 61-y-old man showing intrapelvic protrusion and bone loss. The uncemented femoral component was well fixed at the time of revision. (B) Postoperative anteroposterior radiograph showing acetabular revision using an acetabular reinforcement ring with a hook and impaction bone grafts. A trochanteric osteotomy was required for exposure. (C) Three-and-one-half-year postoperative radiograph demonstrating healing of the allograft and continued good fixation of the femoral component. The patient had a good clinical result, with a Harris hip score of 88 points.
36 cases. Final follow-up radiographs revealed no changes in cup position, osteolytic lesion progression around the femoral and acetabular components, or measurable polyethylene wear. Thus, selective acetabular revision may provide good clinical results in THAs with isolated acetabular failure. Higher-than-expected overall rates of acetabular revision have been attributed to wear and osteolysis and failure of liner mechanisms [1, 14, 15]. Often, liner failure occurs without loosening of the acetabular shell [14–16]. In most of these cases, especially those in which failure occurred more than 5 y after implantation, the locking mechanism of the metal shell has been damaged, and a simple liner change to one of a similar design may be impossible. Some authors have recommended revision of the entire acetabular component in cases of liner failure [3, 5]. However, revision of a well-fixed acetabular shell may be difficult and presents risks including acetabulum fracture, significant bone loss, prolonged rehabilitation, and aseptic loosening. The potential advantages of a simple liner cementation are reduced surgical morbidity, more rapid patient recovery, and the possibility of changing the bearing surface from metal-polyethylene to metalcross-linked polyethylene. Several clinical series with short-term follow-up of liner cementation have recently been reported with good results [15, 17–20]. The failure rate of this technique was reported to be low, from 2.6% (1/39) to 18.8% (6/32) in a mean follow-up of 2 to 5.1 y. In the present study, no unrevised acetabular shell showed evidence of loosening or mechanical failure. The technique was
also supported by biomechanical tests. The cemented polyethylene liner was found to have an initial fixation strength exceeding that of the conventional locking mechanism if 2- and 4-mm-thick cement mantles were built up around the liner [21–25]. The few failures were all attributed to the inadequate seating of an oversized liner within the metal shell [17, 19, 26]. In general, we tried to use a liner 4 mm smaller than the inner diameter of an existing shell, and took care to contain the liner within the metal shell (Fig. 3). Three cases with liner failure in our series had to have the well-fixed acetabular shell removed because the inner diameter was less than 48 mm, and a liner of 44 mm or less could not match the existing 28-mm head on the unrevised femoral component. Our study also demonstrated that leaving a well-fixed femoral component during acetabular revision is a viable option. Although several authors have reported good results with a technique in which a well-fixed cemented femoral component was removed and then reinserted into its cement mantle after the acetabular revision [6, 7], the high rate of mechanical failure after revision of the femoral component should be considered. Peters et al. reported that 49 femoral components that had been inserted without cement were revised using a curved, long-stem, proximally porous-coated component because of aseptic loosening; with revision surgery or progressive subsidence as the end point, the chance of survival of the component at 72 mo was only 37% [27]. Undoubtedly, revision of a well-fixed cemented femoral component involves even greater technical demands, operating time, and morbidity than revision
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FIG. 3. (A) Asymmetrical wear of the liner with a well-fixed acetabular shell and an uncemented femoral stem in a 59-y-old woman evaluated 11 y postoperatively. (B) Revision was performed using cementation and a polyethylene liner. (C) Three years postoperatively, the acetabular shell and the femoral component remained well fixed, and the Harris hip score was 96 points.
of a similar implant that is loose [28–30]. In our study, all unrevised femoral components remained well fixed, and final follow-up radiographs revealed no osteolytic lesion progression around the femoral components. Thus, although more effective femoral components may be available for revisions, we believe that a well-fixed femoral component should be retained at the time of revision of the acetabular component failure. Several important steps are recommended to achieve successful results in selective revision. The stability of the existing shell and femoral component should be evaluated after removing all debris and exposing the metal–bone interface of the components. After verifying shell or femoral component stability, all debris should be cleared from the component surface. All loose screws should be removed because they do not promote stability, and osteolytic lesions should be treated with a bone graft (Fig. 4). In the present study, morselized
cancellous allograft was used to fill acetabular defects in 27 hips and proximal femoral defects in 17 hips, and bulk allografts were used to reconstruct the proximal femur in two hips. This study has limitations. Besides the lack of a control group, our series consists of a selected patient group, which is difficult to compare with other published series of revision total hip arthroplasty. The indication for selection revision precluded those with severe bone stock deficiencies, and 19 of our patients (52.8%) were revised for wear of the polyethylene liner. This may be favorable to the follow-up results. But the results of our series, including more complicated cases, can be compared with that of isolated liner revision with mean 2- to 5.1-y follow-up [17, 18, 20]. We also have another series in which the well-fixed components had to be revised in certain circumstances, such as a well-fixed femoral stem that was removed when
FIG. 4. (A) All debris was cleared from the component surface, and the metal-bone interface of the unrevised femoral component was exposed. (B) The morselized cancellous and bulk allografts were used to reconstruct the proximal femur. (Color version of figure is available online.)
HE ET AL.: SELECTIVE HIP ARTHROPLASTY REVISION IN ISOLATED ACETABULAR FAILURE
a modular femoral head was worn, and an appropriatesized head was not available. Although most hips in this series are doing well, there was considerably more morbidity in the treatment with total revision (data not published). Upon gradually recognizing the advantages of the selective revision, we treated isolated hip component failure with this simple surgery more and more in recent years. It is admitted that the spread of the followup period of our patients included in this study is fairly large, and appears to concentrate in the lower range. This may bias the result favorably toward selection revision. These results must be the preliminary consideration. Since osteolysis may take several years to redevelop after a revision, additional long-term followup is required. In conclusion, this study has demonstrated that selective acetabular revision for isolated acetabular failure of THA is an alternative with excellent clinical success over the medium term, allowing the preservation of acetabular and femoral bone stock while reducing surgical morbidity. ACKNOWLEDGMENTS This work was financially supported by the Natural Science Foundation of Shanghai Jiao Tong University (Grant 2008XJ038).
REFERENCES 1. Maloney W, Rosenberg A. Implant Wear Symposium 2007 Clinical Work Group. What is the outcome of treatment for osteolysis? J Am Acad Orthop Surg 2008;16(Suppl 1):S26. 2. LaPorte DM, Mont MA, Pierre-Jacques H, et al. Technique for acetabular liner revision in a nonmodular metal-backed component. J Arthroplasty 1998;13:348. 3. Maloney WJ, Herzwurm P, Paprosky W, et al. Treatment of pelvic osteolysis associated with a stable acetabular component inserted without cement as part of a total hip replacement. J Bone Joint Surg Am 1997;79:1628. 4. Terefenko KM, Sychterz CJ, Orishimo K, et al. Polyethylene liner exchange for excessive wear and osteolysis. J Arthroplasty 2002;17:798. 5. Engelbrecht DJ, Weber FA, Sweet MB, et al. Long-term results of revision total hip arthroplasty. J Bone Joint Surg Br 1990;72:41. 6. Nelson CL. Cemented femoral revision: Technique and outcome. Am J Orthop 2002;31:187. 7. Mandziak DG, Howie DW, Neale SD, et al. Cement-withincement stem exchange using the collarless polished double-taper stem. J Arthroplasty 2007;22:1000. 8. Moskal JT, Shen FH, Brown TE. The fate of stable femoral components retained during isolated acetabular revision: A six-to-twelve-year follow-up study. J Bone Joint Surg Am 2002;84:250. 9. Peters CL, Kull L, Jacobs JJ, et al. The fate of well fixed cemented femoral components left in place at the time of revision of the acetabular component. J Bone Joint Surg Am 1997;79:701. 10. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: Treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am 1969;51:737.
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11. DeLee JG, Charnley J. Radiological demarcation of cemented sockets in total hip replacement. Clin Orthop 1976;121:20. 12. 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. 13. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop 1990;257:107. 14. Peters CL, Sullivan CL. Locking mechanism failure in the Harris-Galante porous acetabular component associated with recurrent hip dislocation. J Arthroplasty 2002;17:507. 15. Ranawat CS, DiGiovanni C, Pellicci P. Treatment of recurrent instability after hybrid total hip arthroplasty by cementing constrained, all-polyethylene liners into well-fixed metal-backed shells: Two-year results. Presented as a poster at the Annual Meeting of the American Academy of Orthopaedic Surgeons. Orlando, FL, Mar 15–19, 2000. 16. Cameron HU. Dissociation of a polyethylene liner from an acetabular cup. Orthop Rev 1993;22:1160. 17. Haft GF, Heiner AD, Callaham JJ, et al. Polyethylene liner cementation into fixed acetabular shells. J Arthroplasty 2002; 17(Suppl 1):167. 18. Springer BD, Hanssen AD, Lewallen DG. Cementation of an acetabular liner into a well-fixed acetabular shell during revision total hip arthroplasty. J Arthroplasty 2003; 18(Suppl 1):126. 19. Yoon TR, Seon JK, Song EK, et al. Cementation of a metal-inlay polyethylene liner into a stable metal shell in revision total hip arthroplasty. J Arthroplasty 2005;20:652. 20. Beaule´ PE, Ebramzadeh E, LeDuff M, et al. Cementing a liner into a stable cementless acetabular shell: The double-socket technique. J Bone Joint Surg Am 2004;86:929. 21. Delanois RE, Seyler TM, Essner A, et al. Cementation of a polyethylene liner into a metal shell. J Arthroplasty 2007; 22:732. 22. Mauerhan DR, Peindl RD, Coley ER, et al. Cementation of polyethylene liners into well-fixed metal shells at the time of revision total hip arthroplasty. J Arthroplasty 2008;23:873. 23. Meldrum RD, Hollis JM. The strength of a cement acetabular locking mechanism. J Arthroplasty 2001;16:748. 24. Bonner KF, Delanois RE, Harbach G, et al. Cementation of a polyethylene liner into a metal shell: Factors related to mechanical stability. J Bone Joint Surg Am 2002;84:1587. 25. Heiner AD, Haft GF, Dorr LD, et al. A biomechanical analysis of polyethylene liner cementation into a fixed metal acetabular shell. J Bone Joint Surg Am 2003;85:1100. 26. Desantis M, Dorr LD, Longjohn DB, et al. Can inserts be cemented into fixed shells at revision THR? Presented as a poster at the Annual Meeting of the American Academy of Orthopaedic Surgeons. Orlando, FL, Mar 15–19, 2000. 27. Peters CL, Rivero DP, Kull LR, et al. Revision total hip arthroplasty without cement: Subsidence of proximally porouscoated femoral components. J Bone Joint Surg Am 1995;77:1217. 28. Ahnfelt L, Herberts P, Malchau H, et al. Prognosis of total hip replacement. A Swedish multicenter study of 4664 revisions. Acta Orthop Scand 1990;238(Suppl):1. 29. Callaghan JJ, Salvati EA, Pellicci PM, et al. Results of revision for mechanical failure after cemented total hip replacement, 1979 to 1982. A two- to five-year follow-up. J Bone Joint Surg Am 1985;67:1074. 30. Pellicci PM, Wilson PD, Sledge CB, et al. Long-term results of revision total hip replacement. A follow-up report. J Bone Joint Surg Am 1985;67:513.
Results of Selective Hip Arthroplasty Revision in Isolated Acetabular Failure Chuan He, M.D., Ph.D.,*,† Jian-Min Feng, M.D.,*,1 Qing-Ming Yang, M.D.,*,† Yi Wang, M.D.,* and Zhi-Hong Liu, M.D.* *Department of Orthopedics, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; and †Shanghai Institute of Traumatology and Orthopaedics, Shanghai, China Submitted for publication January 17, 2009
Background. Controversy exists over whether to remove well-fixed components at the time of revision of a failed total hip arthroplasty (THA). The purpose of this study was to evaluate the results of selective acetabular revision after acetabular failure in which only the failed component was replaced. Materials and Methods. Thirty-six isolated acetabular component revisions were performed and prospectively followed for a mean of 4.7 y (range, 2–9.3 y). The components had been in place for a mean of 10.8 y. All femoral components and some metal-backed acetabular shells were well fixed at the time of revision and left in place. Surgery involved cementation of an acetabular liner into a well-fixed acetabular shell in 16 cases, and acetabular revision in 20 cases. Morselized cancellous allograft was used to fill acetabular defects in 27 hips, and proximal femoral defects in 17 hips. Bulk allografts were used to reconstruct the proximal femur in two hips. Results. The mean Harris hip score improved from 57.8 preoperatively to 89.1 at the final follow-up visit. The results were rated excellent in 24 patients, good in nine patients, and fair in three patients. The unrevised femoral components and acetabular shells remained well fixed, and final follow-up radiographs revealed no cases of osteolytic lesion progression around the femoral and acetabular components. Conclusions. Revision of only the failed acetabular component is recommended in cases of isolated acetabular failure, providing excellent results over the medium term, and allowing preservation of bone stock with lower surgical morbidity. Ó 2010 Elsevier Inc. All rights reserved. 1 To whom correspondence and reprint requests should be addressed at Department of Orthopedics, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, No. 197, Rui Jin Er Road, Shanghai 2000025, China. E-mail: [email protected].
0022-4804/$36.00 Ó 2010 Elsevier Inc. All rights reserved.
Key Words: acetabular revision; selective hip arthroplasty revision; stable acetabular shell; cement; acetabular liner; acetabular shell; femoral components.
INTRODUCTION
Revision hip arthroplasty due to wear-induced osteolysis is an increasingly common procedure [1–4]. Debrisinduced osteolysis is an ongoing problem in patients with revision total hip arthroplasty (THA). Polyethylene wear leads to bone loss in areas where the debrisladen joint fluid is pumped toward the interface. Near the acetabulum, these lesions can be large, with access gained through screw holes in the cup or around the periphery of the cup. Lesions can also occur at the proximal femur and around the upper femoral stem. Often, however, the cup or the stem itself is still well fixed through osseointegration. In these cases, the decision must be made whether to routinely replace these well-fixed devices during revision surgery. A common clinical scenario involves a well-fixed metal-backed acetabular shell with a failed polyethylene insert. The failure may be due to polyethylene wear, a defective locking mechanism, or a malpositioned component. Another common situation involves a wellfixed femoral component with a loosening acetabular component. Some reports recommend replacing the entire acetabular component when a liner fails without loosening of the acetabular shell or removing a wellfixed femoral component after revision of the acetabular component [3, 5–7]. Removal of a well-fixed femoral or acetabular component, however, may lead to substantial bone loss and possible fracture or nonunion, greatly complicating an otherwise simple revision.
228
HE ET AL.: SELECTIVE HIP ARTHROPLASTY REVISION IN ISOLATED ACETABULAR FAILURE
An alternative is selective revision of the failed component, while leaving the well-fixed components in place [8, 9]. The present study was conducted to evaluate the clinical and radiologic results over the medium term (>2-y follow-up) of selective acetabular revision, while retaining a well-fixed femoral component or a stable acetabular shell. MATERIALS AND METHODS Patient Demographics Between May 1998 and May 2006, 196 hips (173 patients) underwent revision THA in our Orthopedic Department. The average time from primary THA to revision surgery was more than 5 y in 138 hips (117 patients), and revision of the acetabular component alone was performed in 37 hips (37 patients). One patient (one hip) was lost to follow-up after less than 2 y. The remaining 36 hips (36 patients) formed the basis of this study. Of the 36 procedures, 14 were performed in men and 22 in women. The mean patient age at revision surgery was 59.3 y (range, 45–71 y). The mean time from implantation to acetabular component failure was 10.8 y (range, 5.1–13.2 y). The indication for selection revision was painful aseptic loosening of the acetabular component in 17 hips with a well-fixed femoral stem, and dislocation or fracture of the polyethylene inner bearing in 19 hips with a well-fixed acetabular shell and femoral stem. The cases were determined for selection or total revision, based on the stability of components evaluated preoperatively and intraoperatively. If the lesions progressed far enough and the integrity of the bone became compromised, a more typical revision operation was planned even when the component seemed to be securely fixed.
Implant The primary articulation was metal on polyethylene in all 36 cases. There were 34 uncemented acetabular components, and two allpolyethylene acetabular components. On the femoral side, there were 31 uncemented stems and five cemented stems.
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Follow-up Evaluation Clinical results were graded using Harris hip scores (maximum score, 100 points) [10]. Hips with scores ranging from 90 to 100 points were graded as excellent, from 80 to 89 points as good, from 70 to 79 points as fair, and below 70 points as poor. Preoperative and final follow-up radiographs were evaluated for osteolysis, inclination of the acetabular component, stability of the acetabular and femoral components, and hip center correction. We measured the lateral opening angle of the acetabular component on anteroposterior radiographs. The angle formed between the line drawn between the lower end of the teardrop on both sides and the line drawn along the lateral face of the component was measured. To evaluate the hip center, vertical migration was determined with respect to the inferior aspect of the teardrop, and the Ko¨hler line was used to measure horizontal migration. Definite acetabular loosening was defined as a change in the opening angle of the component of more than 4 , or a change in horizontal or vertical position of the component of more than 3 mm. Radiolucent lines were measured using the zones described by DeLee and Charnley [11]. Only cases involving 50% or more of a zone were considered. For the cemented femoral components, fixation was described using the method of Harris and McGann [12]. Definite loosening was defined as a shift in the position of the cement mantle relative to the femur, cement, or stem fracture, or new radiolucent line at the prosthesis-cement interface. Probable loosening was defined as a continuous (100%) radiolucent line at the bone–cement interface without migration. Possible loosening was defined as the presence of a radiolucent line involving between 50% and 99% of the interface. For noncemented components, fixation was defined using the method of Engh et al. [13]. Definite loosening was indicated by subsidence of greater than 5 mm.
Statistical Analysis The Cox proportional-hazards regression model was used to identify univariate and multivariate factors contributing to the differential follow-up results. Preoperative and postoperative scores were compared using paired t-tests. Paired t-tests also were used to assess vertical distances between the center of rotation and the radiographic teardrop and horizontal distances between the center of rotation and the Ko¨hler line in the affected hips after the revision and the normal hips. Significance was determined by P value < 0.05. Statistical analysis was performed with the SPSS software package (version 11.1; SPSS, Chicago, IL).
Operative Procedure Of 19 hips with isolated polyethylene liner failure, three had the well-fixed acetabular shells revised because satisfactory replacement liners were not available, and another 16 hips were treated with cementation of a new polyethylene liner into the original acetabular shell. Acetabulum was reconstructed according to the integrity of the bony socket after the acetabular component was removed if entire acetabular revision was indicated. In brief, the surgical method were as follows: cementation of an acetabular liner into a well-fixed acetabular shell in 16 cases, exchange for a larger uncemented acetabular component in six cases, exchange for an all-polyethylene acetabular component in two cases, acetabular reconstruction with impaction bone grafts and an acetabular reinforcement ring in 11 cases, and acetabular reconstruction with a mesh, impaction bone grafts, and a customized all-polyethylene acetabular component in one case (Fig. 1). Localized pelvic osteolysis was identified in 14 cases, localized femoral osteolysis in 11 cases, and metallosis in association with pelvic and femoral osteolysis in three cases. Morselized cancellous allograft was used to fill acetabular defects in 27 hips, among which impaction bone graft was performed through the enlarged screw holes of the acetabular component in 10 cases of acetabular shell retention. Bone graft was performed at the proximal femur in 17 cases, and bulk allografts were used to reconstruct the proximal femur in two hips.
RESULTS
All 36 patients were prospectively followed for a mean of 4.7 y (range, 2–9.3 y). The mean duration of total implantation time of the unrevised component at the final follow-up was 15.5 y, with a range of 12.6–17.4 years. In none of those cases was a second revision operation necessary because of loosening of the acetabular or femoral component. The mean Harris hip score improved from 57.8 (range, 36–77) preoperatively to 89.1 at the final follow-up visit (range, 74–97) (t ¼ 24.481, P < 0.001). The results were rated excellent in 24 patients, good in nine patients, and fair in three patients; thus, 92% of all patients had excellent or good results. All three of the patients with results rated as fair were cases of entire acetabular component failure who underwent revision with impaction bone grafts and an acetabular reinforcement ring. These
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FIG. 1. (A) Preoperative anteroposterior radiograph of a loose cemented acetabular component in a 69-y-old woman showing bone loss and rigid fixation of the femoral component at the time of revision. (B) Postoperative radiograph showing revision of only the acetabular component with a mesh, impaction bone grafts, and a customized all-polyethylene acetabular component to match the original 32-mm femoral head; trochanteric osteotomy was required for exposure. (C) Five-year postoperative radiograph showing continued good fixation of the acetabular and femoral components. The patient had an excellent clinical result, with a Harris hip score of 92 points.
three patients had associated knee and spine problems, with two having ankylosing spondylitis, and one having degenerative spinal stenosis and knee osteoarthritis. The Cox proportional-hazards regression model revealed that the preoperative Harris hip score (P ¼ 0.003, risk ratio ¼ 5.0, 95% confidence interval ¼ 1.5%–17.5%) was the significant independent predictor of the differential follow-up results. Multivariate results indicated that the surgical method (P ¼ 0.301), the diseases for the primary total hip arthroplasty (P ¼ 0.565), patient gender (P ¼ 0.951), age (P ¼ 0.071), the duration of follow-up (P ¼ 0.133), and the position of the implants (P ¼ 0.169) did not have a statistically significant impact on the rating between ‘‘excellent’’ and ‘‘good.’’
average inclination of the polyethylene liner was 40.9 . The allograft used in hips was considered to have healed, with trabecular bridging seen (Fig. 2). Final follow-up radiographs revealed no measurable polyethylene wear in any of the cases. Before surgery, none of the cemented or noncemented femoral components had definite, probable, or possible loosening as defined by the criteria of Harris and McGann [12]. After surgery, of the remaining five nonrevised cemented femoral components, none subsided or definitely loosened. Of the 31 nonrevised noncemented femoral components, none subsided or showed notable radiolucent lines or osteolysis, and all were classified as stable with bone ingrowth. Complication
Radiographic Evaluation
Final follow-up radiographs revealed no cases of osteolytic lesion progression around the femoral and acetabular components. No acetabular component migrated with regard to hip center correction. The mean distance from the inferior aspect of the teardrop to the center of rotation was 33 mm preoperatively, which was reduced to 21.5 mm postoperatively (t ¼ 10.871, P < 0.001), compared with 20.4 mm on the normal side. The mean distance from the Ko¨hler line to the center of rotation was 36 mm preoperatively, which was corrected to 40 mm postoperatively (t ¼ 2.434, P ¼ 0.02), compared with 41.5 mm on the normal side. The average inclination of the existing shell was 43.6 , with a range of 32 to 57 , and the
One patient who underwent revision with impaction bone grafts and an acetabular reinforcement ring experienced a dislocation, and was successfully treated by closed reduction under general anesthesia and immobilization in a hip spica cast for 6 wk. Instability did not recur. DISCUSSION
We evaluated the results of selective acetabular revision, including liner cementation into a stable acetabular shell using a polyethylene liner and total acetabular revision, for late (>5 y) acetabular failure of THA in 36 hips. Clinical review at a mean of 4.7 y showed excellent or good results in 33 (92%) of the
HE ET AL.: SELECTIVE HIP ARTHROPLASTY REVISION IN ISOLATED ACETABULAR FAILURE
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FIG. 2. (A) Preoperative anteroposterior radiograph of a loose uncemented acetabular component in a 61-y-old man showing intrapelvic protrusion and bone loss. The uncemented femoral component was well fixed at the time of revision. (B) Postoperative anteroposterior radiograph showing acetabular revision using an acetabular reinforcement ring with a hook and impaction bone grafts. A trochanteric osteotomy was required for exposure. (C) Three-and-one-half-year postoperative radiograph demonstrating healing of the allograft and continued good fixation of the femoral component. The patient had a good clinical result, with a Harris hip score of 88 points.
36 cases. Final follow-up radiographs revealed no changes in cup position, osteolytic lesion progression around the femoral and acetabular components, or measurable polyethylene wear. Thus, selective acetabular revision may provide good clinical results in THAs with isolated acetabular failure. Higher-than-expected overall rates of acetabular revision have been attributed to wear and osteolysis and failure of liner mechanisms [1, 14, 15]. Often, liner failure occurs without loosening of the acetabular shell [14–16]. In most of these cases, especially those in which failure occurred more than 5 y after implantation, the locking mechanism of the metal shell has been damaged, and a simple liner change to one of a similar design may be impossible. Some authors have recommended revision of the entire acetabular component in cases of liner failure [3, 5]. However, revision of a well-fixed acetabular shell may be difficult and presents risks including acetabulum fracture, significant bone loss, prolonged rehabilitation, and aseptic loosening. The potential advantages of a simple liner cementation are reduced surgical morbidity, more rapid patient recovery, and the possibility of changing the bearing surface from metal-polyethylene to metalcross-linked polyethylene. Several clinical series with short-term follow-up of liner cementation have recently been reported with good results [15, 17–20]. The failure rate of this technique was reported to be low, from 2.6% (1/39) to 18.8% (6/32) in a mean follow-up of 2 to 5.1 y. In the present study, no unrevised acetabular shell showed evidence of loosening or mechanical failure. The technique was
also supported by biomechanical tests. The cemented polyethylene liner was found to have an initial fixation strength exceeding that of the conventional locking mechanism if 2- and 4-mm-thick cement mantles were built up around the liner [21–25]. The few failures were all attributed to the inadequate seating of an oversized liner within the metal shell [17, 19, 26]. In general, we tried to use a liner 4 mm smaller than the inner diameter of an existing shell, and took care to contain the liner within the metal shell (Fig. 3). Three cases with liner failure in our series had to have the well-fixed acetabular shell removed because the inner diameter was less than 48 mm, and a liner of 44 mm or less could not match the existing 28-mm head on the unrevised femoral component. Our study also demonstrated that leaving a well-fixed femoral component during acetabular revision is a viable option. Although several authors have reported good results with a technique in which a well-fixed cemented femoral component was removed and then reinserted into its cement mantle after the acetabular revision [6, 7], the high rate of mechanical failure after revision of the femoral component should be considered. Peters et al. reported that 49 femoral components that had been inserted without cement were revised using a curved, long-stem, proximally porous-coated component because of aseptic loosening; with revision surgery or progressive subsidence as the end point, the chance of survival of the component at 72 mo was only 37% [27]. Undoubtedly, revision of a well-fixed cemented femoral component involves even greater technical demands, operating time, and morbidity than revision
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FIG. 3. (A) Asymmetrical wear of the liner with a well-fixed acetabular shell and an uncemented femoral stem in a 59-y-old woman evaluated 11 y postoperatively. (B) Revision was performed using cementation and a polyethylene liner. (C) Three years postoperatively, the acetabular shell and the femoral component remained well fixed, and the Harris hip score was 96 points.
of a similar implant that is loose [28–30]. In our study, all unrevised femoral components remained well fixed, and final follow-up radiographs revealed no osteolytic lesion progression around the femoral components. Thus, although more effective femoral components may be available for revisions, we believe that a well-fixed femoral component should be retained at the time of revision of the acetabular component failure. Several important steps are recommended to achieve successful results in selective revision. The stability of the existing shell and femoral component should be evaluated after removing all debris and exposing the metal–bone interface of the components. After verifying shell or femoral component stability, all debris should be cleared from the component surface. All loose screws should be removed because they do not promote stability, and osteolytic lesions should be treated with a bone graft (Fig. 4). In the present study, morselized
cancellous allograft was used to fill acetabular defects in 27 hips and proximal femoral defects in 17 hips, and bulk allografts were used to reconstruct the proximal femur in two hips. This study has limitations. Besides the lack of a control group, our series consists of a selected patient group, which is difficult to compare with other published series of revision total hip arthroplasty. The indication for selection revision precluded those with severe bone stock deficiencies, and 19 of our patients (52.8%) were revised for wear of the polyethylene liner. This may be favorable to the follow-up results. But the results of our series, including more complicated cases, can be compared with that of isolated liner revision with mean 2- to 5.1-y follow-up [17, 18, 20]. We also have another series in which the well-fixed components had to be revised in certain circumstances, such as a well-fixed femoral stem that was removed when
FIG. 4. (A) All debris was cleared from the component surface, and the metal-bone interface of the unrevised femoral component was exposed. (B) The morselized cancellous and bulk allografts were used to reconstruct the proximal femur. (Color version of figure is available online.)
HE ET AL.: SELECTIVE HIP ARTHROPLASTY REVISION IN ISOLATED ACETABULAR FAILURE
a modular femoral head was worn, and an appropriatesized head was not available. Although most hips in this series are doing well, there was considerably more morbidity in the treatment with total revision (data not published). Upon gradually recognizing the advantages of the selective revision, we treated isolated hip component failure with this simple surgery more and more in recent years. It is admitted that the spread of the followup period of our patients included in this study is fairly large, and appears to concentrate in the lower range. This may bias the result favorably toward selection revision. These results must be the preliminary consideration. Since osteolysis may take several years to redevelop after a revision, additional long-term followup is required. In conclusion, this study has demonstrated that selective acetabular revision for isolated acetabular failure of THA is an alternative with excellent clinical success over the medium term, allowing the preservation of acetabular and femoral bone stock while reducing surgical morbidity. ACKNOWLEDGMENTS This work was financially supported by the Natural Science Foundation of Shanghai Jiao Tong University (Grant 2008XJ038).
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