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Total Hip Arthroplasty After Failed Operative Treatment for Osteonecrosis of the Femoral Head
Total Hip Arthroplasty After Failed Operative Treatment for Osteonecrosis of the Femoral Head Yaw Boachie-Adjei, MD, Jia-Wei Kevin Ko, MD, and Quanjun Cui, MD, MS Of the numerous total hip arthroplasties performed each year for end-stage osteoarthritis a significant number are done in patients who suffer from osteonecrosis of the femoral head. Many of those patients have had a previous surgical treatment in an attempt to preserve the joint and to delay the need for a total hip arthroplasty. These treatments include core decompression with or without bone grafting, proximal femoral osteotomies, and free vascularized bone grafting. Each of these procedures, however, changes the anatomy of the proximal femur and present unique challenges to the orthopedic surgeon attempting to perform a subsequent total hip arthroplasty. Here we discuss the specific pitfalls in performing a total hip arthroplasty after a joint-sparing/preserving procedure and specific strategies with which to deal with each of them. Semin Arthro 19:267-273 © 2008 Elsevier Inc. All rights reserved. KEYWORDS osteonecrosis, total hip arthroplasty, osteotomy, core depression, free fibula
O
steonecrosis (ON) of the femoral head is a pathologic process that results from the interruption of blood supply to the bone. ON of the femoral head is poorly understood, but this process is the final common pathway of myriad factors that compromise the already precarious circulation of the femoral head. Femoral head ischemia results in the death of marrow and osteocytes and can lead to the collapse of the necrotic segment during the remodeling process. The etiology of ON is multifactorial and includes both traumatic and atraumatic causes. Among these are femoral neck fractures, hip dislocations, chronic liver disease, alcohol abuse, and corticosteroid use. Early symptomatic ON may be treated effectively with procedures that preserve the femoral head. Among these procedures are core decompression, rotational osteotomies, free vascularized fibular grafting (FVFG), and femoral resurfacing. Total hip arthroplasty (THA) may also be performed and can provide the most predictable, but not necessarily the most optimal outcome. Although exact figures are not known, it is estimated that 5 to 18% of the more than 500,000 THAs performed annually are for treatment of osteoarthritis caused by ON of the femoral head.1 Because clin-
Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville, VA, USA. Address reprint requests to Quanjun Cui, MD, MS, Department of Orthopaedic Surgery, University of Virginia, P.O. Box 800159, Charlottesville, VA 22908. E-mail: [email protected]
1045-4527/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2008.10.004
ical symptoms of ON typically present in the second through fourth decade of life, many of the patients who seek treatment, including surgical procedures, are relatively young. The mean age of patients who undergo THA for ON is 35 to 38 years old. Prosthetic replacement is an unappealing option for many young and active patients. Literature search of numerous studies of THA found that the revision rate was as high as 20%.2 Since the rate of revision THA in this patient population is unacceptably high, the tenet of joint replacement is to avoid joint replacement surgery if possible. This has led to the development of less invasive joint preserving procedures. Core decompression, free vascularized fibular grafting, and rotational osteotomies preserve the femoral head in patients with ON and allow the surgeon to avoid the challenges and negative sequelae associated with performing a THA in a young patient. Precollapse ON of the femoral head that is amenable to other preservative treatments is thought to be a relative contraindication for THA. This is especially true in younger patients because THA does not have a proven success rate beyond 40 years.3 Despite their utility, these joint preserving procedures do have a common drawback. They all change the anatomy of the proximal femur by deforming the femoral neck and head. Therefore, these procedures can cause significant difficulty when attempting a conversion THA after they fail, as many of them inevitably will. A surgeon performing a conversion THA will need to account for these deformities. Additionally, many will have to deal with the unpredictability of not having 267
268
Figure 1 Right valgus and left varus ostetomies. (Reprinted with permission from Journal of Bone and Joint Surgery Br 76B:252-257, 1994).
been involved with the index procedure. These factors can increase the operative difficulty and perioperative complication rate and may decrease the long-term survival of a conversion THA.
Proximal Femoral Osteotomy The purpose of performing an osteotomy for the treatment of osteonecrosis of the femoral head is to redistribute the weight-bearing forces away from the necrotic region of the femoral head (Fig. 1). This may prevent or delay femoral head collapse. Osteotomies may also decrease rest pain by relieving intramedullary hypertension. Although an osteotomy is regarded as an effective temporizing procedure, it has variable reported success rates ranging from 17 to 94%.4 Regardless of the actual numbers, it is known that many patients will still require conversion to a THA in the future (Figs. 2 and 3). Because of the changes in the bone architecture and the use of hardware associated with an osteotomy, a conversion THA places additional technical demands on the surgeon. Many authors have reported difficulties including increased operative times and blood loss,4 increased rates of infection and aseptic loosening,5 and hardware breakage.6
Dealing with Proximal Femur Deformation Depending on the type of osteotomy performed, a number of alterations to the proximal femoral anatomy can be produced. Varus osteotomies can place the greater trochanter over the femoral canal, impeding entry of the femoral component during a THA. Both varus and valgus osteotomies alter the neck–shaft angle, which affects the sizing of the femoral component, the head–neck offset, and the collar– calcar contact if a collared implant is used. Rotational osteotomies can mask the typical landmarks used for insertion of the femoral component and alter the rotational alignment of the femoral shaft (Fig. 4). This can make it difficult to achieve the proper anteversion of the femoral component. Displacement osteotomies present similar issues to those mentioned above. All osteotomies can make it more difficult to determine the precise axis of the femoral shaft. Preparation
Y. Boachie-Adjei, J.-W.K. Ko, and Q. Cui of the proximal femur and obtaining stable fixation of the femoral component in these patients is therefore a challenge. These difficulties have been shown to affect the survivorship of the femoral component and correlate with the degree of deformation in the proximal femur.7 Several strategies have been utilized to optimize fixation of the femoral component in individuals with proximal femoral deformities resulting from a prior osteotomy. Iwase and coworkers,8 demonstrated better survivorship of the femoral component using cemented stems compared with cementless stems. Results were comparable to cemented stems used in primary THA previously presented in the literature. Cementless stems offer better biological fixation in primary THA but are designed to fit a femur with normal anatomy. This makes it more difficult to achieve initial fixation in patients with a prior osteotomy. Initial fixation is more readily achievable with cemented stems in a deformed proximal femur resulting in their superior long-term survival rate. However, the current trends are to use press-fit femoral components; if proximal press-fit is not feasible, diaphyseal fixation stem may be used. In this condition, greater trochanter osteotomy may be needed. Alignment and exposure of the femoral canal is often an issue in patients with previous osteotomies. Boos and coworkers,6 performed trochanteric osteotomy if needed with comparable results to primary cemented THA. Trochanteric osteotomy can provide better exposure to the femoral canal when a prior osteotomy has made this more difficult to achieve. Additionally, it can be used to tension the hip abductor muscles to provide greater global stability. More recently, Lim and coworkers,9 have shown good results using the S-ROM modular stem (Depuy/Johnson & Johnson, Warsaw, IN). A prior osteotomy can make it difficult to obtain concurrent proximal and distal fixation. Proximally fixed implants lack rotational stability and can lead to endosteal hypertrophy and cortical hypertrophy. Distally fixed implants are susceptible to stress shielding in the proximal portion of the implant. Modular stems allow optimization of the proximal and distal fixation through interchangeable components and achievement of good rotational stability. Although this technique is presented for THA after osteotomies, the study also showed modular stems to be useful in THA after core decompression and free vascularized fibular grafting. Drawbacks of this study include its relatively small cohort and its retrospective nature; however, modular stems may become a viable alternative to other types of stems.
Dealing with Osteotomy Hardware Some of the technical complications associated with a conversion THA from a prior osteotomy arise from the removal of hardware and the residual cortical defects that are left behind. Reported complications include screw and wire breakage as well as fractures resulting from holes left by cortical screws.5,6,10 Conflicting evidence exists regarding whether the osteotomy hardware should be removed before a conversion THA, with the goal of alleviating some of these complications.
Failed operative treatment
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Figure 2 (A) Radiograph of right hip joint taken 7 years after intertrochanteric valgus ostetomy showing findings of terminal osteoarthritis. (B) Radiograph obtained after conversion cementless total hip arthroplasty with autologous acetabular bone graft. (C) Radiograph taken 7 years after total hip arthroplasty shows apparent stem subsidence to valgus position. (D) Revision surgery with a cementless porous coated long stem. (Reprinted with permission from Clinical Orthopedics and Related Research 364:175-181, 1999).
Ferguson and coworkers,5 advocated removal of osteotomy hardware after the osteotomy had healed and at least 6 months before a conversion THA. Ferguson and coworkers5 argued that cortical holes left by screws decreased the quality of cement bone interdigitation. Any cement that penetrates the holes has the potential to act as stress risers, leading to fractures in the future. Removal of osteotomy hardware soon after bony healing has been demonstrated could result in greater ease of removal and allow time for the natural healing process to diminish the size of cortical defects. Additionally, it could potentially decrease infection rates since Ferguson and coworkers5 reported a number of positive cultures from the osteotomy site.
Shinar and Harris,7 challenged this recommendation and did not endorse the removal of osteotomy hardware before a conversion THA. They argued that the use of second-generation cementing techniques eliminated any need for prior hardware removal. The only difficulty that they encountered was canal narrowing from endosteal reaction affecting the cement mantle. They claimed that this would not have likely been addressed by early hardware removal and could easily be corrected by reaming the canal to a larger diameter. Removing the hardware at the time of the conversion THA also eliminates the need for an additional procedure. Infection was not an issue in their study cohort. Shinar and Harris7 also countered that, despite the large number of positive cultures
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differences in fracture rates compared with primary THA, cortical bone defects left from the prior osteotomy procedure creates a mechanism for these fractures to occur. Sobelle and coworkers11 recommended avoidance of forced external rotation and minimizing the displacement of the initial osteotomy as strategies to prevent fracture. The surgeon must take extra care when handling the bone given its pre-existing defects during a conversion procedure. While many fractures may not require fixation, more significant fractures have been treated with cerclage wires or screw fixation.
Core Decompression
Figure 3 Failed femoral osteotomy. (Reprinted with permission from Journal of Bone and Joint Surgery Br 76B:252-257, 1994).
in the Ferguson and coworkers5 study, there was only one documented infection.
Dealing with Perioperative Fractures In 1989, Soballe and coworkers11 reported an increased rate of perioperative fractures in conversion THA after an osteotomy. While subsequent studies have not reported significant
The therapeutic effect of core decompression with or without bone grafting on avascular necrosis of the femoral head is based on reducing the increased interosseous pressure resulting in immediate pain reduction. Decompressing the intramedullary compartment also improves blood flow to the femoral head preventing further progression of the necrotic region. Core decompression may also promote revascularization of the femoral head. The best results for core decompression have been shown when it is implemented during the earlier stages of osteonecrosis.1,12 Despite optimization of patient selection and surgical techniques, progressive deterioration is inevitable in some hips requiring conversion to THA. Core decompression is one of the least-invasive temporizing procedures for osteonecrosis of the hip. Although there is generally minimal anatomical deformation of the proximal femur during this procedure, decompression may compromise the structural integrity of the cancellous bone, especially in the proximal femur. Bone grafting will enhance the core
Figure 4 Radiograph after medial displacement femoral osteotomy and subsequest revision to cemented total hip arthroplasty using Muller prosthesis. Note proximal femoral deformity. (Reprinted with permission from Journal of Bone Joint Surgery Am 71A:692-697, 1989).
Failed operative treatment
Figure 5 Right hip after free vascularized fibular graft (note advanced osteoarthritic changes despite the union of previous FVFG). (Reprinted with permission from Journal of Arthroplasty 23:495-501, 2008).
tract healing and lead to a bony bar formation in the femoral neck, extending to the lateral cortex of the greater trochanter. This has the potential to lead to varus position of the femoral component and a greater number of perioperative fractures during a conversion THA, although no such data have been published. Given the paucity of data addressing conversion THA after core decompression, no specific recommendations regarding operative technique have ever been made. However, we suggest that careful preoperative planning be undertaken and that the surgeon takes extra care to remove bony bar and to avoid placing any additional stress on the cored region of the femur. A high speed burr or a lateralization reamer can be very useful in this situation.
271 process; and 4) protection of the healing construct by a period of no weight bearing (Fig. 5).13 For the treatment of lower-grade lesions, FVFG is a good alternative to THA. Its advantages include sparing the femoral head and maintaining bone stock while avoiding the infection risk associated with foreign body/implants. It also promotes femoral head survival when done before subchondral collapse. FVFG has been shown to reduce the rates of THA in patients with ON compared with similar patients treated nonoperatively. Despite its utility, free vascularized bone grafting does not always alter the likelihood of disease progression in osteonecrosis after subchondral collapse and the development of a radiographic crescent sign. Often times, patients do not present to their physician until this stage is present or imminent. FVFG is still often done to provide some relief and to temporize the progression of ON. However, progression to femoral head collapse is sometimes inevitable. Significant subsets of patients in whom FVFG has been performed will have return of their hip pain. While function and pain relief are gained and maintained from FVFG for an initial period of time, many patients will still have progression of ON. These individuals will require a conversion THA. Conversion rates from FVFG to THA within 5 years ranged from 11% in Ficat stage II to 29% in Ficat stage IV disease.2,14 These numbers highlight an important point concerning femoral head–preserving procedures in patients with symptomatic ON: they are temporizing measures. To ensure continued patient comfort and mobility, conversion to a THA is usually the next step in the treatment algorithm. There are a number of challenges inherent in this conversion. They in-
Free Vascularized Fibular Grafting Free vascularized fibular grafting is a technique that has been shown to delay the progression of femoral head destruction in patients with ON of the femoral head. FVFG involves removal of necrotic bone from the femoral head and filling the resultant defect with a corticocancellous bone strut along with its associated vascular pedicle. The rationale is based on four aspects of the operation and the postoperative care: 1) decompression of the femoral head, which may interrupt the cycle of ischemia and interosseus hypertension; 2) excision of the sequestrum that may inhibit revascularization of the femoral head; 3) filling of the defect that is created with osteoinductive cancellous graft and a viable cortical strut to support the subchondral surface and to enhance the revascularization
Figure 6 Eight-year follow-up of 36-year-old man with a previous free vascularized fibular graft and conversion to total hip arthroplasty. A tapered stem was used without burring of the FVFG. The femoral stem is in varus and there is a substantial amount of residual graft. (Reprinted with permission from Journal of Bone and Joint Surgery 88:110-115, 2006, suppl 3).
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Figure 7 Early failure of total hip arthroplasty. (A) Early postoperative radiograph with inadequate amount of cement mantle proximally. (B) Gross loosening associated with cement failure and osteolysis. (C) A prerevision radiograph of a hybrid total hip arthroplasty with cement failure probably secondary to cement failure and osteolysis. (Reprinted with permission from The Journal of Arthroplasty 18:411-419, 2003).
clude the technical aspect of the conversion procedure, problems with postoperative function, and implant failure leading to revision.
Postoperative Function Compared with patients undergoing initial THA for osteoarthritis and ON, short-term function has been shown to be worse in patients who have hip arthroplasty after FVFG.9 Patients with previous FVFG have been shown to have lower Harris hip scores as well as St. Michael’s hip scores after THA. Postoperative range of motion is also decreased in these patients. They may lose up to 10° of flexion– extension and internal– external rotation.9 Each of these situations prohibits patients from participating in postoperative rehabilitation, threatening the overall success of the procedure. Despite this potential issue, long-term outcomes did not appear to be adversely affected in this study.
aspect of the proximal femur. The goal of this is to incorporate the graft with the native surrounding bone. When preparing the femoral canal during a subsequent THA, this bone often blocks the placement of broaches, rasps, and the implant itself. This prevents adequate lateralization resulting in a greater likelihood that the stem will be placed in varus positioning (Fig. 6). This is known to be a cause of pain and implant loosening after THA. Residual lateral bone may also block the deposition of adequate bone cement resulting in an insufficient lateral cement column. This predisposes the hip to microfracture, fragmentation, and failure of stem fixation (Fig. 7). Furthermore, wear particles have a tract through which to propagate distally around the stem, which could result in severe osteolysis. These possible pitfalls underscore the importance of removing the fibular cortical bone during THA after FVFG.
Overall Revision Rate Revision rates are increased in THA after FVFG compared with arthroplasty as the initial procedure in patients with ON. Berend and coworkers2 found an 18% overall revision rate (5.6% at 5 years, 14.6% at 10 years) in 92 patients who underwent 112 THA for progressive ON after a previous FVFG. When reviewing the literature of 17 separate studies with 750 cumulative patients with ON in whom 1040 THAs were done, the overall revision rate was 13%. This represents a significant difference from primary THA and shows greater durability in hips that have not had FVFG. A factor that aided in the survival of hips after FVFG was the use of uncemented proximally porous-coated stems. Metaphyseal fixation was shown to be key in these hips.2
Technical Considerations An FVFG procedure inevitably changes the anatomy of the proximal femur. By placing a cortical strut into the femoral neck, normal landmarks and bone composition are altered. This adds a dimension of difficulty to a conversion THA. In FVFG the fibular cortical bone is placed along the lateral
Figure 8 Schematic of the high speed burr excising graft. (Reprinted with permission from The Journal of Arthroplasty 8:1-6, 1993).
Failed operative treatment This may be done with an osteotome or rongeur. The fibular strut often comes out en masse once loosened. Multiple authors have showed that the use of a high-speed burr can be an effective tool for removing residual graft (Fig. 8).2,15 By removing laterally placed bone, stem alignment is improved with decreased chance of fixation in a varus alignment. One drawback to burr use is that it may add to operative times and lead to increased intraoperative blood loss. However, there has not been any evidence that this has contributed to increased patient morbidity. Limb-length discrepancies after conversion to a THA can also be an issue. A residual cortical bone can block adequate seating of the femoral stem in the canal and make optimal sizing of the femoral component more difficult. At this point, the effect of a prior FVFG procedure on limb-length discrepancies during a conversion THA has not been adequately studied. However, a surgeon must be aware of this potential problem.
Conclusion Total hip arthroplasty after failed femoral head preserving procedures improves the pain and functional status of patients. Importantly, each procedure comes with its own challenges and pitfalls. The unique factors must be considered during preoperative patient counseling, surgical planning, and execution of the procedures.
References 1. Mont MA, Jones LC, Hungerford DS: Nontraumatic osteonecrosis of the femoral head: Ten years later. J Bone Joint Surg Am 88:1117-1132, 2006 2. Berend KR, Gunneson E, Urbaniak JR, et al: Hip arthroplasty after failed free vascularized fibular grafting for osteonecrosis in young patients. J Arthroplasty 18:411-419, 2003
273 3. Stulberg BN: Total hip arthroplasty: Osteonecrosis of the femoral head (ed 1). Chicago, IL, The American Academy of Orthopaedic Surgeons, 2005 4. Kawasaki M, Hasegawa Y, Sakano S, et al: Total hip arthroplasty after failed transtrochanteric rotational osteotomy for avascular necrosis of the femoral head. J Arthroplasty 20:574-579, 2005 5. Ferguson GM, Cabanela ME, Ilstrup DM: Total hip arthroplasty after failed intertrochanteric osteotomy. J Bone Joint Surg Br 76:252-257, 1994 6. Boos N, Krushell R, Ganz R, et al: Total hip arthroplasty after previous proximal femoral osteotomy. J Bone Joint Surg Br 79:247-253, 1997 7. Shinar AA, Harris WH: Cemented total hip arthroplasty following previous femoral osteotomy: An average 16-year follow-up study. J Arthroplasty 13:243-253, 1998 8. Iwase T, Hasegawa Y, Iwasada S, et al: Total hip arthroplasty after failed intertrochanteric valgus osteotomy for advanced osteoarthrosis. Clin Orthop Relat Res 364:175-181, 1999 9. Lim SJ, Moon YW, Eun SS, et al: Total hip arthroplasty using the S-ROM modular stem after joint-preserving procedures for osteonecrosis of the femoral head. J Arthroplasty 23:495-501, 2008 10. Benke GJ, Baker AS, Dounis E: Total hip replacement after upper femoral osteotomy: A clinical review. J Bone Joint Surg Br 64:570-571, 1982 11. Soballe K, Boll KL, Kofod S, et al: Total hip replacement after medialdisplacement osteotomy of the proximal part of the femur. J Bone Joint Surg Am 71:692-697, 1989 12. Fairbank AC, Bhatia D, Jinnah RH, et al: Long-term results of core decompression for ischaemic necrosis of the femoral head. J Bone Joint Surg Br 77:42-49, 1995 13. Urbaniak JR, Coogan PG, Gunneson EB, et al: Treatment of osteonecrosis of the femoral head with free vascularized fibular grafting: A long-term follow-up study of one hundred and three hips. J Bone Joint Surg Am 77:681-694, 1995 14. Berend KR, Gunneson EE, Urbaniak JR: Free vascularized fibular grafting for the treatment of postcollapse osteonecrosis of the femoral head. J Bone Joint Surg Am 85:987-993, 2003 15. Davis ET, McKee MD, Waddell JP, et al: Total hip arthroplasty following failure of free vascularized fibular graft. J Bone Joint Surg Am 88:110-115, 2006 (suppl 3)
O
steonecrosis (ON) of the femoral head is a pathologic process that results from the interruption of blood supply to the bone. ON of the femoral head is poorly understood, but this process is the final common pathway of myriad factors that compromise the already precarious circulation of the femoral head. Femoral head ischemia results in the death of marrow and osteocytes and can lead to the collapse of the necrotic segment during the remodeling process. The etiology of ON is multifactorial and includes both traumatic and atraumatic causes. Among these are femoral neck fractures, hip dislocations, chronic liver disease, alcohol abuse, and corticosteroid use. Early symptomatic ON may be treated effectively with procedures that preserve the femoral head. Among these procedures are core decompression, rotational osteotomies, free vascularized fibular grafting (FVFG), and femoral resurfacing. Total hip arthroplasty (THA) may also be performed and can provide the most predictable, but not necessarily the most optimal outcome. Although exact figures are not known, it is estimated that 5 to 18% of the more than 500,000 THAs performed annually are for treatment of osteoarthritis caused by ON of the femoral head.1 Because clin-
Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville, VA, USA. Address reprint requests to Quanjun Cui, MD, MS, Department of Orthopaedic Surgery, University of Virginia, P.O. Box 800159, Charlottesville, VA 22908. E-mail: [email protected]
1045-4527/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2008.10.004
ical symptoms of ON typically present in the second through fourth decade of life, many of the patients who seek treatment, including surgical procedures, are relatively young. The mean age of patients who undergo THA for ON is 35 to 38 years old. Prosthetic replacement is an unappealing option for many young and active patients. Literature search of numerous studies of THA found that the revision rate was as high as 20%.2 Since the rate of revision THA in this patient population is unacceptably high, the tenet of joint replacement is to avoid joint replacement surgery if possible. This has led to the development of less invasive joint preserving procedures. Core decompression, free vascularized fibular grafting, and rotational osteotomies preserve the femoral head in patients with ON and allow the surgeon to avoid the challenges and negative sequelae associated with performing a THA in a young patient. Precollapse ON of the femoral head that is amenable to other preservative treatments is thought to be a relative contraindication for THA. This is especially true in younger patients because THA does not have a proven success rate beyond 40 years.3 Despite their utility, these joint preserving procedures do have a common drawback. They all change the anatomy of the proximal femur by deforming the femoral neck and head. Therefore, these procedures can cause significant difficulty when attempting a conversion THA after they fail, as many of them inevitably will. A surgeon performing a conversion THA will need to account for these deformities. Additionally, many will have to deal with the unpredictability of not having 267
268
Figure 1 Right valgus and left varus ostetomies. (Reprinted with permission from Journal of Bone and Joint Surgery Br 76B:252-257, 1994).
been involved with the index procedure. These factors can increase the operative difficulty and perioperative complication rate and may decrease the long-term survival of a conversion THA.
Proximal Femoral Osteotomy The purpose of performing an osteotomy for the treatment of osteonecrosis of the femoral head is to redistribute the weight-bearing forces away from the necrotic region of the femoral head (Fig. 1). This may prevent or delay femoral head collapse. Osteotomies may also decrease rest pain by relieving intramedullary hypertension. Although an osteotomy is regarded as an effective temporizing procedure, it has variable reported success rates ranging from 17 to 94%.4 Regardless of the actual numbers, it is known that many patients will still require conversion to a THA in the future (Figs. 2 and 3). Because of the changes in the bone architecture and the use of hardware associated with an osteotomy, a conversion THA places additional technical demands on the surgeon. Many authors have reported difficulties including increased operative times and blood loss,4 increased rates of infection and aseptic loosening,5 and hardware breakage.6
Dealing with Proximal Femur Deformation Depending on the type of osteotomy performed, a number of alterations to the proximal femoral anatomy can be produced. Varus osteotomies can place the greater trochanter over the femoral canal, impeding entry of the femoral component during a THA. Both varus and valgus osteotomies alter the neck–shaft angle, which affects the sizing of the femoral component, the head–neck offset, and the collar– calcar contact if a collared implant is used. Rotational osteotomies can mask the typical landmarks used for insertion of the femoral component and alter the rotational alignment of the femoral shaft (Fig. 4). This can make it difficult to achieve the proper anteversion of the femoral component. Displacement osteotomies present similar issues to those mentioned above. All osteotomies can make it more difficult to determine the precise axis of the femoral shaft. Preparation
Y. Boachie-Adjei, J.-W.K. Ko, and Q. Cui of the proximal femur and obtaining stable fixation of the femoral component in these patients is therefore a challenge. These difficulties have been shown to affect the survivorship of the femoral component and correlate with the degree of deformation in the proximal femur.7 Several strategies have been utilized to optimize fixation of the femoral component in individuals with proximal femoral deformities resulting from a prior osteotomy. Iwase and coworkers,8 demonstrated better survivorship of the femoral component using cemented stems compared with cementless stems. Results were comparable to cemented stems used in primary THA previously presented in the literature. Cementless stems offer better biological fixation in primary THA but are designed to fit a femur with normal anatomy. This makes it more difficult to achieve initial fixation in patients with a prior osteotomy. Initial fixation is more readily achievable with cemented stems in a deformed proximal femur resulting in their superior long-term survival rate. However, the current trends are to use press-fit femoral components; if proximal press-fit is not feasible, diaphyseal fixation stem may be used. In this condition, greater trochanter osteotomy may be needed. Alignment and exposure of the femoral canal is often an issue in patients with previous osteotomies. Boos and coworkers,6 performed trochanteric osteotomy if needed with comparable results to primary cemented THA. Trochanteric osteotomy can provide better exposure to the femoral canal when a prior osteotomy has made this more difficult to achieve. Additionally, it can be used to tension the hip abductor muscles to provide greater global stability. More recently, Lim and coworkers,9 have shown good results using the S-ROM modular stem (Depuy/Johnson & Johnson, Warsaw, IN). A prior osteotomy can make it difficult to obtain concurrent proximal and distal fixation. Proximally fixed implants lack rotational stability and can lead to endosteal hypertrophy and cortical hypertrophy. Distally fixed implants are susceptible to stress shielding in the proximal portion of the implant. Modular stems allow optimization of the proximal and distal fixation through interchangeable components and achievement of good rotational stability. Although this technique is presented for THA after osteotomies, the study also showed modular stems to be useful in THA after core decompression and free vascularized fibular grafting. Drawbacks of this study include its relatively small cohort and its retrospective nature; however, modular stems may become a viable alternative to other types of stems.
Dealing with Osteotomy Hardware Some of the technical complications associated with a conversion THA from a prior osteotomy arise from the removal of hardware and the residual cortical defects that are left behind. Reported complications include screw and wire breakage as well as fractures resulting from holes left by cortical screws.5,6,10 Conflicting evidence exists regarding whether the osteotomy hardware should be removed before a conversion THA, with the goal of alleviating some of these complications.
Failed operative treatment
269
Figure 2 (A) Radiograph of right hip joint taken 7 years after intertrochanteric valgus ostetomy showing findings of terminal osteoarthritis. (B) Radiograph obtained after conversion cementless total hip arthroplasty with autologous acetabular bone graft. (C) Radiograph taken 7 years after total hip arthroplasty shows apparent stem subsidence to valgus position. (D) Revision surgery with a cementless porous coated long stem. (Reprinted with permission from Clinical Orthopedics and Related Research 364:175-181, 1999).
Ferguson and coworkers,5 advocated removal of osteotomy hardware after the osteotomy had healed and at least 6 months before a conversion THA. Ferguson and coworkers5 argued that cortical holes left by screws decreased the quality of cement bone interdigitation. Any cement that penetrates the holes has the potential to act as stress risers, leading to fractures in the future. Removal of osteotomy hardware soon after bony healing has been demonstrated could result in greater ease of removal and allow time for the natural healing process to diminish the size of cortical defects. Additionally, it could potentially decrease infection rates since Ferguson and coworkers5 reported a number of positive cultures from the osteotomy site.
Shinar and Harris,7 challenged this recommendation and did not endorse the removal of osteotomy hardware before a conversion THA. They argued that the use of second-generation cementing techniques eliminated any need for prior hardware removal. The only difficulty that they encountered was canal narrowing from endosteal reaction affecting the cement mantle. They claimed that this would not have likely been addressed by early hardware removal and could easily be corrected by reaming the canal to a larger diameter. Removing the hardware at the time of the conversion THA also eliminates the need for an additional procedure. Infection was not an issue in their study cohort. Shinar and Harris7 also countered that, despite the large number of positive cultures
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differences in fracture rates compared with primary THA, cortical bone defects left from the prior osteotomy procedure creates a mechanism for these fractures to occur. Sobelle and coworkers11 recommended avoidance of forced external rotation and minimizing the displacement of the initial osteotomy as strategies to prevent fracture. The surgeon must take extra care when handling the bone given its pre-existing defects during a conversion procedure. While many fractures may not require fixation, more significant fractures have been treated with cerclage wires or screw fixation.
Core Decompression
Figure 3 Failed femoral osteotomy. (Reprinted with permission from Journal of Bone and Joint Surgery Br 76B:252-257, 1994).
in the Ferguson and coworkers5 study, there was only one documented infection.
Dealing with Perioperative Fractures In 1989, Soballe and coworkers11 reported an increased rate of perioperative fractures in conversion THA after an osteotomy. While subsequent studies have not reported significant
The therapeutic effect of core decompression with or without bone grafting on avascular necrosis of the femoral head is based on reducing the increased interosseous pressure resulting in immediate pain reduction. Decompressing the intramedullary compartment also improves blood flow to the femoral head preventing further progression of the necrotic region. Core decompression may also promote revascularization of the femoral head. The best results for core decompression have been shown when it is implemented during the earlier stages of osteonecrosis.1,12 Despite optimization of patient selection and surgical techniques, progressive deterioration is inevitable in some hips requiring conversion to THA. Core decompression is one of the least-invasive temporizing procedures for osteonecrosis of the hip. Although there is generally minimal anatomical deformation of the proximal femur during this procedure, decompression may compromise the structural integrity of the cancellous bone, especially in the proximal femur. Bone grafting will enhance the core
Figure 4 Radiograph after medial displacement femoral osteotomy and subsequest revision to cemented total hip arthroplasty using Muller prosthesis. Note proximal femoral deformity. (Reprinted with permission from Journal of Bone Joint Surgery Am 71A:692-697, 1989).
Failed operative treatment
Figure 5 Right hip after free vascularized fibular graft (note advanced osteoarthritic changes despite the union of previous FVFG). (Reprinted with permission from Journal of Arthroplasty 23:495-501, 2008).
tract healing and lead to a bony bar formation in the femoral neck, extending to the lateral cortex of the greater trochanter. This has the potential to lead to varus position of the femoral component and a greater number of perioperative fractures during a conversion THA, although no such data have been published. Given the paucity of data addressing conversion THA after core decompression, no specific recommendations regarding operative technique have ever been made. However, we suggest that careful preoperative planning be undertaken and that the surgeon takes extra care to remove bony bar and to avoid placing any additional stress on the cored region of the femur. A high speed burr or a lateralization reamer can be very useful in this situation.
271 process; and 4) protection of the healing construct by a period of no weight bearing (Fig. 5).13 For the treatment of lower-grade lesions, FVFG is a good alternative to THA. Its advantages include sparing the femoral head and maintaining bone stock while avoiding the infection risk associated with foreign body/implants. It also promotes femoral head survival when done before subchondral collapse. FVFG has been shown to reduce the rates of THA in patients with ON compared with similar patients treated nonoperatively. Despite its utility, free vascularized bone grafting does not always alter the likelihood of disease progression in osteonecrosis after subchondral collapse and the development of a radiographic crescent sign. Often times, patients do not present to their physician until this stage is present or imminent. FVFG is still often done to provide some relief and to temporize the progression of ON. However, progression to femoral head collapse is sometimes inevitable. Significant subsets of patients in whom FVFG has been performed will have return of their hip pain. While function and pain relief are gained and maintained from FVFG for an initial period of time, many patients will still have progression of ON. These individuals will require a conversion THA. Conversion rates from FVFG to THA within 5 years ranged from 11% in Ficat stage II to 29% in Ficat stage IV disease.2,14 These numbers highlight an important point concerning femoral head–preserving procedures in patients with symptomatic ON: they are temporizing measures. To ensure continued patient comfort and mobility, conversion to a THA is usually the next step in the treatment algorithm. There are a number of challenges inherent in this conversion. They in-
Free Vascularized Fibular Grafting Free vascularized fibular grafting is a technique that has been shown to delay the progression of femoral head destruction in patients with ON of the femoral head. FVFG involves removal of necrotic bone from the femoral head and filling the resultant defect with a corticocancellous bone strut along with its associated vascular pedicle. The rationale is based on four aspects of the operation and the postoperative care: 1) decompression of the femoral head, which may interrupt the cycle of ischemia and interosseus hypertension; 2) excision of the sequestrum that may inhibit revascularization of the femoral head; 3) filling of the defect that is created with osteoinductive cancellous graft and a viable cortical strut to support the subchondral surface and to enhance the revascularization
Figure 6 Eight-year follow-up of 36-year-old man with a previous free vascularized fibular graft and conversion to total hip arthroplasty. A tapered stem was used without burring of the FVFG. The femoral stem is in varus and there is a substantial amount of residual graft. (Reprinted with permission from Journal of Bone and Joint Surgery 88:110-115, 2006, suppl 3).
Y. Boachie-Adjei, J.-W.K. Ko, and Q. Cui
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Figure 7 Early failure of total hip arthroplasty. (A) Early postoperative radiograph with inadequate amount of cement mantle proximally. (B) Gross loosening associated with cement failure and osteolysis. (C) A prerevision radiograph of a hybrid total hip arthroplasty with cement failure probably secondary to cement failure and osteolysis. (Reprinted with permission from The Journal of Arthroplasty 18:411-419, 2003).
clude the technical aspect of the conversion procedure, problems with postoperative function, and implant failure leading to revision.
Postoperative Function Compared with patients undergoing initial THA for osteoarthritis and ON, short-term function has been shown to be worse in patients who have hip arthroplasty after FVFG.9 Patients with previous FVFG have been shown to have lower Harris hip scores as well as St. Michael’s hip scores after THA. Postoperative range of motion is also decreased in these patients. They may lose up to 10° of flexion– extension and internal– external rotation.9 Each of these situations prohibits patients from participating in postoperative rehabilitation, threatening the overall success of the procedure. Despite this potential issue, long-term outcomes did not appear to be adversely affected in this study.
aspect of the proximal femur. The goal of this is to incorporate the graft with the native surrounding bone. When preparing the femoral canal during a subsequent THA, this bone often blocks the placement of broaches, rasps, and the implant itself. This prevents adequate lateralization resulting in a greater likelihood that the stem will be placed in varus positioning (Fig. 6). This is known to be a cause of pain and implant loosening after THA. Residual lateral bone may also block the deposition of adequate bone cement resulting in an insufficient lateral cement column. This predisposes the hip to microfracture, fragmentation, and failure of stem fixation (Fig. 7). Furthermore, wear particles have a tract through which to propagate distally around the stem, which could result in severe osteolysis. These possible pitfalls underscore the importance of removing the fibular cortical bone during THA after FVFG.
Overall Revision Rate Revision rates are increased in THA after FVFG compared with arthroplasty as the initial procedure in patients with ON. Berend and coworkers2 found an 18% overall revision rate (5.6% at 5 years, 14.6% at 10 years) in 92 patients who underwent 112 THA for progressive ON after a previous FVFG. When reviewing the literature of 17 separate studies with 750 cumulative patients with ON in whom 1040 THAs were done, the overall revision rate was 13%. This represents a significant difference from primary THA and shows greater durability in hips that have not had FVFG. A factor that aided in the survival of hips after FVFG was the use of uncemented proximally porous-coated stems. Metaphyseal fixation was shown to be key in these hips.2
Technical Considerations An FVFG procedure inevitably changes the anatomy of the proximal femur. By placing a cortical strut into the femoral neck, normal landmarks and bone composition are altered. This adds a dimension of difficulty to a conversion THA. In FVFG the fibular cortical bone is placed along the lateral
Figure 8 Schematic of the high speed burr excising graft. (Reprinted with permission from The Journal of Arthroplasty 8:1-6, 1993).
Failed operative treatment This may be done with an osteotome or rongeur. The fibular strut often comes out en masse once loosened. Multiple authors have showed that the use of a high-speed burr can be an effective tool for removing residual graft (Fig. 8).2,15 By removing laterally placed bone, stem alignment is improved with decreased chance of fixation in a varus alignment. One drawback to burr use is that it may add to operative times and lead to increased intraoperative blood loss. However, there has not been any evidence that this has contributed to increased patient morbidity. Limb-length discrepancies after conversion to a THA can also be an issue. A residual cortical bone can block adequate seating of the femoral stem in the canal and make optimal sizing of the femoral component more difficult. At this point, the effect of a prior FVFG procedure on limb-length discrepancies during a conversion THA has not been adequately studied. However, a surgeon must be aware of this potential problem.
Conclusion Total hip arthroplasty after failed femoral head preserving procedures improves the pain and functional status of patients. Importantly, each procedure comes with its own challenges and pitfalls. The unique factors must be considered during preoperative patient counseling, surgical planning, and execution of the procedures.
References 1. Mont MA, Jones LC, Hungerford DS: Nontraumatic osteonecrosis of the femoral head: Ten years later. J Bone Joint Surg Am 88:1117-1132, 2006 2. Berend KR, Gunneson E, Urbaniak JR, et al: Hip arthroplasty after failed free vascularized fibular grafting for osteonecrosis in young patients. J Arthroplasty 18:411-419, 2003
273 3. Stulberg BN: Total hip arthroplasty: Osteonecrosis of the femoral head (ed 1). Chicago, IL, The American Academy of Orthopaedic Surgeons, 2005 4. Kawasaki M, Hasegawa Y, Sakano S, et al: Total hip arthroplasty after failed transtrochanteric rotational osteotomy for avascular necrosis of the femoral head. J Arthroplasty 20:574-579, 2005 5. Ferguson GM, Cabanela ME, Ilstrup DM: Total hip arthroplasty after failed intertrochanteric osteotomy. J Bone Joint Surg Br 76:252-257, 1994 6. Boos N, Krushell R, Ganz R, et al: Total hip arthroplasty after previous proximal femoral osteotomy. J Bone Joint Surg Br 79:247-253, 1997 7. Shinar AA, Harris WH: Cemented total hip arthroplasty following previous femoral osteotomy: An average 16-year follow-up study. J Arthroplasty 13:243-253, 1998 8. Iwase T, Hasegawa Y, Iwasada S, et al: Total hip arthroplasty after failed intertrochanteric valgus osteotomy for advanced osteoarthrosis. Clin Orthop Relat Res 364:175-181, 1999 9. Lim SJ, Moon YW, Eun SS, et al: Total hip arthroplasty using the S-ROM modular stem after joint-preserving procedures for osteonecrosis of the femoral head. J Arthroplasty 23:495-501, 2008 10. Benke GJ, Baker AS, Dounis E: Total hip replacement after upper femoral osteotomy: A clinical review. J Bone Joint Surg Br 64:570-571, 1982 11. Soballe K, Boll KL, Kofod S, et al: Total hip replacement after medialdisplacement osteotomy of the proximal part of the femur. J Bone Joint Surg Am 71:692-697, 1989 12. Fairbank AC, Bhatia D, Jinnah RH, et al: Long-term results of core decompression for ischaemic necrosis of the femoral head. J Bone Joint Surg Br 77:42-49, 1995 13. Urbaniak JR, Coogan PG, Gunneson EB, et al: Treatment of osteonecrosis of the femoral head with free vascularized fibular grafting: A long-term follow-up study of one hundred and three hips. J Bone Joint Surg Am 77:681-694, 1995 14. Berend KR, Gunneson EE, Urbaniak JR: Free vascularized fibular grafting for the treatment of postcollapse osteonecrosis of the femoral head. J Bone Joint Surg Am 85:987-993, 2003 15. Davis ET, McKee MD, Waddell JP, et al: Total hip arthroplasty following failure of free vascularized fibular graft. J Bone Joint Surg Am 88:110-115, 2006 (suppl 3)