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Fracture of Fully Coated Echelon Femoral Stems in Revision Total Hip Arthroplasty
The Journal of Arthroplasty Vol. 24 No. 2 2009
Case Report
Fracture of Fully Coated Echelon Femoral Stems in Revision Total Hip Arthroplasty Joshua Landa, MD,* Michael Benke, BS,† Alan Dayan, MD,* Gavin Pereira, MBBS, FRCS(Eng), FRCS(Orth),‡ and Paul E. Di Cesare, MD§
Abstract: Three cases of fractured uncemented, fully porous Echelon femoral stems (Smith & Nephew, Memphis, Tenn) are examined. Fracture of these components, an uncommon complication of revision hip surgery, is thought to result from cantilever bending after distal bony ingrowth. The stems in these cases fractured at 11, 22, and 28 months after revision surgery. Risk factors include increased body weight, excessive activity, an undersized stem, varus alignment, inadequate proximal femoral bone stock, and metallurgic defects. Extraction can be difficult and is often accomplished with the use of multiple trephines or via tamping through a distal cortical window. Key words: fractured stem, revision total hip arthroplasty, Echelon, porous-coated stem. © 2009 Published by Elsevier Inc.
Implant fracture is an uncommon reason for failure of revision total hip arthroplasty (THA). There are several large series of broken primary femoral stems [1-4], but reports of broken revision stems are less common. In addition, most stem fractures have been reported on cemented prostheses [5], most likely because proximal cement loosening of a distally well-fixed stem allows for cantilever bending forces on the stem. Fracture of a cobalt-chrome, noncemented, extensively porous-coated revision femoral stem has been reported rarely; we found only 7 cases in the literature. Of these 7 cases, 2 were Anatomic Medullary Locking revision femoral stems (DePuy, From the *NYU Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, New York; †NYU School of Medicine, New York, New York; ‡Adult Reconstructive Surgery, NYU Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, New York; and §Department of Orthopaedic Surgery, UC Davis Medical Center, Sacramento, California. Submitted March 30, 2007; accepted December 12, 2007. No benefits or funds were received in support of the study. Reprint requests: Paul E. Di Cesare, MD, FACS, UC Davis Medical Center, 4860 Y Street, Suite 3800, Sacramento, CA 95817. © 2009 Published by Elsevier Inc. 0883-5403/07/2402-0025$36.00/0 doi:10.1016/j.arth.2007.12.010
Warsaw, Ind), 2 were Solution stems (DePuy), and 3 were Echelon revision femoral stems (Smith & Nephew, Memphis, Tenn). Sotereanos et al described 2 broken Anatomic Medullary Locking stems, representing a complication rate of 1.6% among the 122 components in their sample [6]. Busch et al reported on 5 broken cobalt-chrome, noncemented, extensively porous-coated revision femoral stems, 3 of which were Echelon and 2 of which were Anatomic Medullary Locking; taken together, these 5 fractured stems represented 2.3% of the 219 stems in their study [7]. Overall, the intraoperative complication rate with the use of the Echelon stem (16/175 or 9.1% in one series) has been comparable with or lower than the rate reported with similar uncemented revision femoral stems [8]; and the prosthesis is thought to be a good choice for revision surgery [9]. Catastrophic femoral failure nevertheless poses a surgical challenge. The distal portion of the stem is typically where significant bony ingrowth has occurred and is consequently well fixed. The broken stem must be carefully removed without causing significant bony deficit, canal perforation, or periprosthetic fracture. Proximal bone loss must be
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322.e14 The Journal of Arthroplasty Vol. 24 No. 2 February 2009 addressed, and new implant/graft must be placed so as to avoid further structural failure. Following is a presentation of 3 patients with fracture of revision noncemented, extensively porous-coated, cobalt chrome alloy Echelon stems. The stems in these cases fractured at 11, 22, and 28 months after revision surgery.
Case Reports Case 1 The patient is a 51-year-old woman who had previously undergone primary arthroplasty for osteoarthritis of the hip in 1996. In 2001, the hip became infected; and a resection arthroplasty with placement of antibiotic cement spacers was performed. Removal of the infected primary femoral prosthesis required osteotomy of the greater trochanter and a longitudinal split in the femoral cortex. Four months later, the cement spacers were removed; and a 190-mm–long, 13-mm–diameter straight Echelon stem with a size 15-mm calcarreplacement component was inserted. During surgery, it was noted that the greater trochanter was not united and that there was segmental and cavitary proximal femoral bone loss. A constrained acetabular liner was used because of significant soft tissue deficiency. The greater trochanter was reapproximated to the soft tissue because of insufficient proximal bone stock for reattachment. At follow-up, the patient was asymptomatic, although radiographs revealed proximal femoral osteolysis and a chronic nonunion of the greater trochanter (Fig. 1A).
Fig. 1. Anteroposterior radiographs of patient 1. A, Before stem fracture, showing poor proximal femoral bony support and good distal fixation. B, After stem fracture.
Twenty-eight months after the revision, the patient presented to the emergency department after experiencing sudden left thigh pain while walking. Plain radiographs revealed a transverse fracture of the femoral stem at the junction of the proximal and the middle third (Fig. 1B). At revision surgery, the distal portion of the stem was observed to be well fixed. A series of trephine reamers were used to overdrill the femoral component. A proximal femoral allograft was prepared to reconstruct the segmental femoral bone loss. The femoral component used was a noncemented, bowed, 255-mm–long, 16-mm–diameter stem. The patient, who initially did well postoperatively, died 1 year later of unrelated cardiopulmonary complications. Case 2 The patient is a 55-year-old man who had previously undergone a noncemented THA in 1995 for complications of a femoral neck fracture. In 2001, he fell at work and sustained a periprosthetic fracture of his left proximal femur with gross loosening of the femoral prosthesis. He was managed with an open reduction and internal fixation of the femur fracture; and the femoral component was revised to a 15mm–diameter, 190-mm–long Echelon stem. The trochanteric fragment was reattached using a cable grip wire system, and the remaining internal fixation was accomplished using a cable plate and cerclage wires. The patient did well postoperatively, and the periprosthetic fracture healed. In 2003, the patient underwent subsequent revision of the acetabular component for recurrent instability. During the operation, internal fixation of the greater trochanter was attempted to manage a nonunion of the greater trochanter. Aside from a broken grip cable, the patient did well postoperatively and showed no signs of loosening of the femoral component. Evidence of stress shielding of the proximal femur and a greater trochanteric nonunion, however, were apparent on x-ray (Fig. 2A). Eleven months after the revision, the patient presented with thigh pain that occurred suddenly while walking. Radiographs demonstrated a stem fractured transversely at the junction of the proximal and middle thirds of the stem (Fig. 2B). At revision surgery, the patient was noted to have segmental and cavitary proximal femur bone loss and a nonunion of the greater trochanter, whereas the distal portion of the stem was well fixed. A longitudinal femoral osteotomy was performed, and multiple cannulated reamers were used to remove
Fracture of Revision Femoral Stems Landa et al
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Fig. 4. Series of broken trephines used to extract the wellfixed distal stem in patient 3.
Fig. 2. Anteroposterior radiographs of patient 2. A, Before stem fracture, showing poor proximal femoral bony support and good distal fixation. B, After stem fracture.
the distal portion of the stem. Reconstruction was achieved with a 16-mm–diameter, 190-mm–long uncemented stem using cerclage wire augmentation. The patient was hypotensive for several minutes in the operating room and died several hours postoperatively. An autopsy revealed a cerebrovascular accident with a large area of grossly ischemic brain. Case 3 The patient is a 47-year-old man who had a previous history of posttraumatic degenerative joint disease when he underwent a right THA in 1995 and a left THA in 1996. In May 2004, the patient was taken to the hospital after hearing a “pop” in his left hip while bending over and was found to have
catastrophic fracture through the neck of his left femoral prosthesis. At the time of surgery, he was noted to have no proximal femoral bone loss and a securely fixed metaphyseal proximal porous-coated uncemented stem. It was also noted that the stem fracture occurred adjacent to a cerclage cable, which can serve as a stress riser and predispose to a fractured stem. Revision of the femoral component was performed using a 14-mm–diameter, 190-mm– long Echelon stem (Fig. 3A). He presented 3 months later with a left hip dislocation and subsequently underwent successful closed reduction in the emergency department. Twenty-two months after revision, the patient presented with left hip pain experienced while walking. Radiographs revealed a transverse fracture of his femoral prosthesis at the junction of the proximal and middle thirds of the stem (Fig. 3B). During revision surgery, it was noted that the distal portion of the femoral stem was securely fixed and that only minor cavitary proximal bone loss was present. A series of 27 trephine reamers were used to overdrill and loosen the distal portion of the femoral component (Fig. 4). The femoral component was revised to a noncemented, 16-mm– diameter, 217-mm–long revision stem. At the most recent follow-up, in August 2006, the patient reported only mild pain in his left hip.
Discussion
Fig. 3. Anteroposterior radiographs of patient 3. A, Before stem fracture, showing no significant proximal bone loss. B, After stem fracture.
Each of the 3 patients in the series received an Echelon femoral stem, a cobalt-chrome, fully porous-coated, uncemented, distally slotted, and fluted component used in revision hip arthroplasty for failure of an uncemented THA (Fig. 5). The Echelon stem is available in 2 lengths—190 mm (straight stem) and 260 mm (bowed stem)—and a series of diameters from 11 to 22 mm. The extensive porous coating provides a large surface area for bony ingrowth and good initial diaphyseal fixation. Clinical studies of this device have reported satisfactory clinical outcomes [10-12].
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Fig. 5. Echelon cobalt-chrome, fully porous-coated, uncemented, distally slotted, and fluted femoral stem.
The femoral components in the present study fractured at a mean of 21 months (range, 11-28) after revision surgery. At the time of fracture, patient mean age was 51 years (range, 47-55), mean weight was 90.6 kg (range, 88.9-91.6), and mean body mass index was 30.6 (range, 28.9-32.3). Risk factors for prosthetic fracture can be subdivided into categories relating to the patient or to the implant. One apparent patient-related risk factor is weight. Charnley reported an inordinately high rate of stem fractures in patients who weighed more than 88 kg [13], which describes all 3 patients in our study. In addition, the 3 patients in this series were relatively young for the multiply revised cohort. Although increased activity may lead to more cycles of cantilever loading, it is unknown to what degree age may be a factor in fatigue failure of revision femoral stems. Perhaps the most important patient risk factor is inadequate proximal femoral bone stock, which applied to 2 patients in this series. Both of these patients were noted to have significant proximal osteolysis and greater trochanteric nonunions. Coupled with distal bony ingrowth, this would have created a cantilever force that was the most likely cause of fatigue and ultimate failure of the femoral component with cyclic bending stresses [14]. Because the bending moment on a homogenous solid cylinder is inversely proportional to the product of the Young modulus of elasticity and the
area moment of inertia (1/4πr2 for a solid cylinder), the use of metals with a high Young modulus (such as cobalt-chrome) is preferable; and stems with smaller radii are substantially more susceptible to fatigue fracture [15]. Some authors recommend a femoral component of size 13.5 or greater [7]. With the possible exception of patient 1 (size 13 femoral component), none of the prostheses was considered “at risk” due to small diameter. In addition, the use of a constrained liner in one patient may have increased the bending forces on the proximal femoral prosthesis. Constrained liners should be avoided in patients who may have difficulty with compliance because the stresses on the acetabular and femoral components are high when the recommended range of motion is exceeded. One method to add support to the proximal femur is the use of cancellous impaction allografting, which was not used in any of the patients in this series. By supplementing the poor bone stock in the proximal calcar area, cantilever bending forces may be decreased. There is controversy, however, over whether this technique should be limited to polished, double-tapered stems or whether its use should be generalized to other femoral prosthesis; and complications with this technique exist, in particular perioperative femur fracture due to higher hoop stresses [16]. Application of a beaded porous coating is known to weaken femoral prostheses. Ong et al demonstrated that the failure rate of roughened, precoated, cemented femoral components is higher and occurred earlier than that of femoral components that were neither textured nor precoated with methylmethacrylate [17]. Metallurgic defects, when present, may also contribute to fatigue fracture [2,3,18]. Gross appearance of the stem in all 3 patients revealed a typical transverse fracture pattern with no obvious defects in the metal (Fig. 6A, B). No information was released by the manufacturer regarding their analysis despite numerous attempts. These revision stems come in standard and high offset options that are intended to allow the surgeon to ensure appropriate joint tension to improve hip stability, increase hip range of motion, and increase strength of abduction [19,20]. These higher offset options would increase the tension at the neck-shaft interface but should not have a marked affect at the more distal aspects of the stem. In the cases presented, the neck offset for the size 13 and 14 stems was 37 mm; and that for the size 15 stem was 40 mm. Of note, all 3 fractures occurred near cerclage wires. Although the use of cerclage wires has not
Fracture of Revision Femoral Stems Landa et al
Fig. 6. Two views of the broken stem extracted from patient 3. The fracture occurred just proximal to the area of solid bony ingrowth.
been proven, to our knowledge, to be a risk factor for fracturing a prosthetic revision stem, it is possible that they serve as a fulcrum for the cantilever bending forces and may predispose to fractures in particular when they erode into the cortex. None of the prostheses was placed in varus, as varus positioning increases stresses on the lateral aspect of the femoral component by increasing the bending moment; this may be more relevant to cemented stems. During revision, trephine reamers were used to remove the fixed distal portion of the broken femoral stem in all 3 patients. The use of trephines for extraction of the distal portion of a cylindrical broken femoral stem has previously been described [21,22]. Trephine reaming is not without complications. The teeth on the trephines are quickly worn out during reaming of the well-fixed prosthesis; and so many trephines must be available, particularly if the prosthesis is long. These drill-powered reamers build up considerable heat, and continuous irrigation is necessary to limit devascularization of the endosteal blood supply. Longitudinal fracture of the distal end of a trephine reamer has recently been reported; upon fracture of the reamer, the distal end of the cylindrical blade expanded and proceeded to fracture the femoral cortex [23]. Reconstruction options after a broken longstem uncemented femoral stem with proximal bone loss include calcar-replacing or proximal femur–replacing prostheses [24]; use of bulk and/ or cancellous allograft; and long, distally fixed prostheses that bypass the deficient proximal femur [25]. Busch et al recommend the use of
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a strut allograft in patients with poor proximal femoral bone stock who required an extended trochanteric osteotomy [7]. A proximal femoral allograft was fashioned to replace the proximal femoral bone loss in patient number 1; a cortical strut graft was used in patient number 3 to support the defect in the lateral cortex. All 3 patients received 16-mm–diameter long stem for revision of the broken stems without complications related to the implant. Of the 3 patients in this study, one died immediately postoperatively and one died a year postoperatively, underscoring the importance of attention to medical comorbidities and potential complications that the surgeon must remain cognizant of. The exact morbidity and mortality of patients undergoing revision specifically for broken femoral stems cannot be known because of the infrequency of this complication. However, in revision THA in general, it has been shown that there is a marked increase in the rate of deep vein thrombosis or pulmonary embolism (1.08% vs 0.68%), decubitus ulcer (1.27% vs 0.28%), and postoperative infection (0.25% vs 0.05%); and the in-hospital mortality rate is significantly elevated (0.84% vs 0.33%) [26]. Three broken Echelon stems have previously been reported in the literature. Many of the characteristics that were associated with fractured stems in that series were present in our 3 patients, namely, poor proximal bone support, extended trochanteric osteotomy, and an elevated weight [7]. In addition, use of a smaller stem size (defined as less than 13.5 mm), another risk factor for a broken stem, was present in one of our patients. Use of cerclage wiring and young patient age may have been a factor as well, although larger studies would be needed to support these conclusions. Results of this study add to the literature on this relatively rare complication after revision arthroplasty and help alert the surgeon to the potential risk factors for its occurrence.
References 1. Wroblewski BM. Fractured stem in total hip replacement. A clinical review of 120 cases. Acta Orthop Scand 1982;53:279. 2. Chao EY, Coventry MB. Fracture of the femoral component after total hip replacement. An analysis of fifty-eight cases. J Bone Joint Surg Am 1981;63:1078. 3. Rostoker W, Chao EY, Galante JO. Defects in failed stems of hip prostheses. J Biomed Mater Res 1978; 12:635.
322.e18 The Journal of Arthroplasty Vol. 24 No. 2 February 2009 4. Stark A, Elssner-Beyer T, Wolf L. Operative aspects of prosthesis change in the hip joint after fracture of the prosthesis shaft. Unfallchirurg 1991;94:355. 5. Woolson ST, Milbauer JP, Bobyn JD, et al. Fatigue fracture of a forged cobalt-chromium-molybdenum femoral component inserted with cement. A report of ten cases. J Bone Joint Surg Am 1997;79:1842. 6. Sotereanos NG, Engh CA, Glassman AH, et al. Cementless femoral components should be made from cobalt chrome. Clin Orthop Relat Res 1995:146. 7. Busch CA, Charles MN, Haydon CM, et al. Fractures of distally-fixed femoral stems after revision arthroplasty. J Bone Joint Surg Br 2005;87:1333. 8. Egan KJ, Di Cesare PE. Intraoperative complications of revision hip arthroplasty using a fully porouscoated straight cobalt-chrome femoral stem. J Arthroplasty 1995;10(Suppl):S45. 9. Issack PS, Guerin J, Butler A, et al. Intraoperative complications of revision hip arthroplasty using a porous-coated, distally slotted, fluted femoral stem. Clin Orthop Relat Res 2004:173. 10. Paprosky WG, Greidanus NV, Antoniou J. Minimum 10-year-results of extensively porous-coated stems in revision hip arthroplasty. Clin Orthop Relat Res 1999:230. 11. Moreland JR, Marder R, Anspach Jr WE. The window technique for the removal of broken femoral stems in total hip replacement. Clin Orthop Relat Res 1986:245. 12. Engh CA, Glassman AH, Griffin WL, et al. Results of cementless revision for failed cemented total hip arthroplasty. Clin Orthop Relat Res 1988:91. 13. Charnley J. Fracture of femoral prostheses in total hip replacement. A clinical study. Clin Orthop Relat Res 1975:105. 14. Gruen TA, McNeice GM, Amstutz HC. “Modes of failure” of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop Relat Res 1979:17. 15. Keaveny TM, Bartel DL. Mechanical consequences of bone ingrowth in a hip prosthesis inserted without cement. J Bone Joint Surg Am 1995;77:911.
16. Morgan HD, McCallister W, Cho MS, et al. Impaction allografting for femoral component revision: clinical update. Clin Orthop Relat Res 2004:160. 17. Ong A, Wong KL, Lai M, et al. Early failure of precoated femoral components in primary total hip arthroplasty. J Bone Joint Surg Am 2002;84-A:786. 18. Cook SD, Kester MA, Harding AF, et al. Metallurgical analysis of five failed cast cobalt-chromium-molybdenum alloy hip prostheses. J Rehabil Res Dev 1986; 23:27. 19. Dolhain P, Tsigaras H, Bourne RB, et al. The effectiveness of dual offset stems in restoring offset during total hip replacement. Acta Orthop Belg 2002;68:490. 20. Crowninshield RD, Maloney WJ, Wentz DH, et al. The role of proximal femoral support in stress development within hip prostheses. Clin Orthop Relat Res 2004;1:176. 21. Glassman AH, Engh CA. The removal of porouscoated femoral hip stems. Clin Orthop Relat Res 1992:164. 22. Babis GC, Tsarouchas J, Boscainos PJ, et al. Removal of the well-bonded distal part of a non-cylindrical broken femoral stem (Autophor 900S) with hollow trephine reamers—report of two cases. Acta Orthop Scand 2002;73:478. 23. Austin MS, Klein GR, Pollice PF. Previously unreported complication of trephine reamers in revision total hip arthroplasty. J Arthroplasty 2006;21:299. 24. McLaughlin JR, Harris WH. Revision of the femoral component of a total hip arthroplasty with the calcarreplacement femoral component. Results after a mean of 10.8 years postoperatively. J Bone Joint Surg Am 1996;78:331. 25. Maurer SG, Baitner AC, Di Cesare PE. Reconstruction of the failed femoral component and proximal femoral bone loss in revision hip surgery. J Am Acad Orthop Surg 2000;8:354. 26. Zhan C, Kaczmarek R, Loyo-Berrios N, et al. Incidence and short-term outcomes of primary and revision hip replacement in the United States. J Bone Joint Surg Am 2007;89:526.
Case Report
Fracture of Fully Coated Echelon Femoral Stems in Revision Total Hip Arthroplasty Joshua Landa, MD,* Michael Benke, BS,† Alan Dayan, MD,* Gavin Pereira, MBBS, FRCS(Eng), FRCS(Orth),‡ and Paul E. Di Cesare, MD§
Abstract: Three cases of fractured uncemented, fully porous Echelon femoral stems (Smith & Nephew, Memphis, Tenn) are examined. Fracture of these components, an uncommon complication of revision hip surgery, is thought to result from cantilever bending after distal bony ingrowth. The stems in these cases fractured at 11, 22, and 28 months after revision surgery. Risk factors include increased body weight, excessive activity, an undersized stem, varus alignment, inadequate proximal femoral bone stock, and metallurgic defects. Extraction can be difficult and is often accomplished with the use of multiple trephines or via tamping through a distal cortical window. Key words: fractured stem, revision total hip arthroplasty, Echelon, porous-coated stem. © 2009 Published by Elsevier Inc.
Implant fracture is an uncommon reason for failure of revision total hip arthroplasty (THA). There are several large series of broken primary femoral stems [1-4], but reports of broken revision stems are less common. In addition, most stem fractures have been reported on cemented prostheses [5], most likely because proximal cement loosening of a distally well-fixed stem allows for cantilever bending forces on the stem. Fracture of a cobalt-chrome, noncemented, extensively porous-coated revision femoral stem has been reported rarely; we found only 7 cases in the literature. Of these 7 cases, 2 were Anatomic Medullary Locking revision femoral stems (DePuy, From the *NYU Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, New York; †NYU School of Medicine, New York, New York; ‡Adult Reconstructive Surgery, NYU Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, New York; and §Department of Orthopaedic Surgery, UC Davis Medical Center, Sacramento, California. Submitted March 30, 2007; accepted December 12, 2007. No benefits or funds were received in support of the study. Reprint requests: Paul E. Di Cesare, MD, FACS, UC Davis Medical Center, 4860 Y Street, Suite 3800, Sacramento, CA 95817. © 2009 Published by Elsevier Inc. 0883-5403/07/2402-0025$36.00/0 doi:10.1016/j.arth.2007.12.010
Warsaw, Ind), 2 were Solution stems (DePuy), and 3 were Echelon revision femoral stems (Smith & Nephew, Memphis, Tenn). Sotereanos et al described 2 broken Anatomic Medullary Locking stems, representing a complication rate of 1.6% among the 122 components in their sample [6]. Busch et al reported on 5 broken cobalt-chrome, noncemented, extensively porous-coated revision femoral stems, 3 of which were Echelon and 2 of which were Anatomic Medullary Locking; taken together, these 5 fractured stems represented 2.3% of the 219 stems in their study [7]. Overall, the intraoperative complication rate with the use of the Echelon stem (16/175 or 9.1% in one series) has been comparable with or lower than the rate reported with similar uncemented revision femoral stems [8]; and the prosthesis is thought to be a good choice for revision surgery [9]. Catastrophic femoral failure nevertheless poses a surgical challenge. The distal portion of the stem is typically where significant bony ingrowth has occurred and is consequently well fixed. The broken stem must be carefully removed without causing significant bony deficit, canal perforation, or periprosthetic fracture. Proximal bone loss must be
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322.e14 The Journal of Arthroplasty Vol. 24 No. 2 February 2009 addressed, and new implant/graft must be placed so as to avoid further structural failure. Following is a presentation of 3 patients with fracture of revision noncemented, extensively porous-coated, cobalt chrome alloy Echelon stems. The stems in these cases fractured at 11, 22, and 28 months after revision surgery.
Case Reports Case 1 The patient is a 51-year-old woman who had previously undergone primary arthroplasty for osteoarthritis of the hip in 1996. In 2001, the hip became infected; and a resection arthroplasty with placement of antibiotic cement spacers was performed. Removal of the infected primary femoral prosthesis required osteotomy of the greater trochanter and a longitudinal split in the femoral cortex. Four months later, the cement spacers were removed; and a 190-mm–long, 13-mm–diameter straight Echelon stem with a size 15-mm calcarreplacement component was inserted. During surgery, it was noted that the greater trochanter was not united and that there was segmental and cavitary proximal femoral bone loss. A constrained acetabular liner was used because of significant soft tissue deficiency. The greater trochanter was reapproximated to the soft tissue because of insufficient proximal bone stock for reattachment. At follow-up, the patient was asymptomatic, although radiographs revealed proximal femoral osteolysis and a chronic nonunion of the greater trochanter (Fig. 1A).
Fig. 1. Anteroposterior radiographs of patient 1. A, Before stem fracture, showing poor proximal femoral bony support and good distal fixation. B, After stem fracture.
Twenty-eight months after the revision, the patient presented to the emergency department after experiencing sudden left thigh pain while walking. Plain radiographs revealed a transverse fracture of the femoral stem at the junction of the proximal and the middle third (Fig. 1B). At revision surgery, the distal portion of the stem was observed to be well fixed. A series of trephine reamers were used to overdrill the femoral component. A proximal femoral allograft was prepared to reconstruct the segmental femoral bone loss. The femoral component used was a noncemented, bowed, 255-mm–long, 16-mm–diameter stem. The patient, who initially did well postoperatively, died 1 year later of unrelated cardiopulmonary complications. Case 2 The patient is a 55-year-old man who had previously undergone a noncemented THA in 1995 for complications of a femoral neck fracture. In 2001, he fell at work and sustained a periprosthetic fracture of his left proximal femur with gross loosening of the femoral prosthesis. He was managed with an open reduction and internal fixation of the femur fracture; and the femoral component was revised to a 15mm–diameter, 190-mm–long Echelon stem. The trochanteric fragment was reattached using a cable grip wire system, and the remaining internal fixation was accomplished using a cable plate and cerclage wires. The patient did well postoperatively, and the periprosthetic fracture healed. In 2003, the patient underwent subsequent revision of the acetabular component for recurrent instability. During the operation, internal fixation of the greater trochanter was attempted to manage a nonunion of the greater trochanter. Aside from a broken grip cable, the patient did well postoperatively and showed no signs of loosening of the femoral component. Evidence of stress shielding of the proximal femur and a greater trochanteric nonunion, however, were apparent on x-ray (Fig. 2A). Eleven months after the revision, the patient presented with thigh pain that occurred suddenly while walking. Radiographs demonstrated a stem fractured transversely at the junction of the proximal and middle thirds of the stem (Fig. 2B). At revision surgery, the patient was noted to have segmental and cavitary proximal femur bone loss and a nonunion of the greater trochanter, whereas the distal portion of the stem was well fixed. A longitudinal femoral osteotomy was performed, and multiple cannulated reamers were used to remove
Fracture of Revision Femoral Stems Landa et al
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Fig. 4. Series of broken trephines used to extract the wellfixed distal stem in patient 3.
Fig. 2. Anteroposterior radiographs of patient 2. A, Before stem fracture, showing poor proximal femoral bony support and good distal fixation. B, After stem fracture.
the distal portion of the stem. Reconstruction was achieved with a 16-mm–diameter, 190-mm–long uncemented stem using cerclage wire augmentation. The patient was hypotensive for several minutes in the operating room and died several hours postoperatively. An autopsy revealed a cerebrovascular accident with a large area of grossly ischemic brain. Case 3 The patient is a 47-year-old man who had a previous history of posttraumatic degenerative joint disease when he underwent a right THA in 1995 and a left THA in 1996. In May 2004, the patient was taken to the hospital after hearing a “pop” in his left hip while bending over and was found to have
catastrophic fracture through the neck of his left femoral prosthesis. At the time of surgery, he was noted to have no proximal femoral bone loss and a securely fixed metaphyseal proximal porous-coated uncemented stem. It was also noted that the stem fracture occurred adjacent to a cerclage cable, which can serve as a stress riser and predispose to a fractured stem. Revision of the femoral component was performed using a 14-mm–diameter, 190-mm– long Echelon stem (Fig. 3A). He presented 3 months later with a left hip dislocation and subsequently underwent successful closed reduction in the emergency department. Twenty-two months after revision, the patient presented with left hip pain experienced while walking. Radiographs revealed a transverse fracture of his femoral prosthesis at the junction of the proximal and middle thirds of the stem (Fig. 3B). During revision surgery, it was noted that the distal portion of the femoral stem was securely fixed and that only minor cavitary proximal bone loss was present. A series of 27 trephine reamers were used to overdrill and loosen the distal portion of the femoral component (Fig. 4). The femoral component was revised to a noncemented, 16-mm– diameter, 217-mm–long revision stem. At the most recent follow-up, in August 2006, the patient reported only mild pain in his left hip.
Discussion
Fig. 3. Anteroposterior radiographs of patient 3. A, Before stem fracture, showing no significant proximal bone loss. B, After stem fracture.
Each of the 3 patients in the series received an Echelon femoral stem, a cobalt-chrome, fully porous-coated, uncemented, distally slotted, and fluted component used in revision hip arthroplasty for failure of an uncemented THA (Fig. 5). The Echelon stem is available in 2 lengths—190 mm (straight stem) and 260 mm (bowed stem)—and a series of diameters from 11 to 22 mm. The extensive porous coating provides a large surface area for bony ingrowth and good initial diaphyseal fixation. Clinical studies of this device have reported satisfactory clinical outcomes [10-12].
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Fig. 5. Echelon cobalt-chrome, fully porous-coated, uncemented, distally slotted, and fluted femoral stem.
The femoral components in the present study fractured at a mean of 21 months (range, 11-28) after revision surgery. At the time of fracture, patient mean age was 51 years (range, 47-55), mean weight was 90.6 kg (range, 88.9-91.6), and mean body mass index was 30.6 (range, 28.9-32.3). Risk factors for prosthetic fracture can be subdivided into categories relating to the patient or to the implant. One apparent patient-related risk factor is weight. Charnley reported an inordinately high rate of stem fractures in patients who weighed more than 88 kg [13], which describes all 3 patients in our study. In addition, the 3 patients in this series were relatively young for the multiply revised cohort. Although increased activity may lead to more cycles of cantilever loading, it is unknown to what degree age may be a factor in fatigue failure of revision femoral stems. Perhaps the most important patient risk factor is inadequate proximal femoral bone stock, which applied to 2 patients in this series. Both of these patients were noted to have significant proximal osteolysis and greater trochanteric nonunions. Coupled with distal bony ingrowth, this would have created a cantilever force that was the most likely cause of fatigue and ultimate failure of the femoral component with cyclic bending stresses [14]. Because the bending moment on a homogenous solid cylinder is inversely proportional to the product of the Young modulus of elasticity and the
area moment of inertia (1/4πr2 for a solid cylinder), the use of metals with a high Young modulus (such as cobalt-chrome) is preferable; and stems with smaller radii are substantially more susceptible to fatigue fracture [15]. Some authors recommend a femoral component of size 13.5 or greater [7]. With the possible exception of patient 1 (size 13 femoral component), none of the prostheses was considered “at risk” due to small diameter. In addition, the use of a constrained liner in one patient may have increased the bending forces on the proximal femoral prosthesis. Constrained liners should be avoided in patients who may have difficulty with compliance because the stresses on the acetabular and femoral components are high when the recommended range of motion is exceeded. One method to add support to the proximal femur is the use of cancellous impaction allografting, which was not used in any of the patients in this series. By supplementing the poor bone stock in the proximal calcar area, cantilever bending forces may be decreased. There is controversy, however, over whether this technique should be limited to polished, double-tapered stems or whether its use should be generalized to other femoral prosthesis; and complications with this technique exist, in particular perioperative femur fracture due to higher hoop stresses [16]. Application of a beaded porous coating is known to weaken femoral prostheses. Ong et al demonstrated that the failure rate of roughened, precoated, cemented femoral components is higher and occurred earlier than that of femoral components that were neither textured nor precoated with methylmethacrylate [17]. Metallurgic defects, when present, may also contribute to fatigue fracture [2,3,18]. Gross appearance of the stem in all 3 patients revealed a typical transverse fracture pattern with no obvious defects in the metal (Fig. 6A, B). No information was released by the manufacturer regarding their analysis despite numerous attempts. These revision stems come in standard and high offset options that are intended to allow the surgeon to ensure appropriate joint tension to improve hip stability, increase hip range of motion, and increase strength of abduction [19,20]. These higher offset options would increase the tension at the neck-shaft interface but should not have a marked affect at the more distal aspects of the stem. In the cases presented, the neck offset for the size 13 and 14 stems was 37 mm; and that for the size 15 stem was 40 mm. Of note, all 3 fractures occurred near cerclage wires. Although the use of cerclage wires has not
Fracture of Revision Femoral Stems Landa et al
Fig. 6. Two views of the broken stem extracted from patient 3. The fracture occurred just proximal to the area of solid bony ingrowth.
been proven, to our knowledge, to be a risk factor for fracturing a prosthetic revision stem, it is possible that they serve as a fulcrum for the cantilever bending forces and may predispose to fractures in particular when they erode into the cortex. None of the prostheses was placed in varus, as varus positioning increases stresses on the lateral aspect of the femoral component by increasing the bending moment; this may be more relevant to cemented stems. During revision, trephine reamers were used to remove the fixed distal portion of the broken femoral stem in all 3 patients. The use of trephines for extraction of the distal portion of a cylindrical broken femoral stem has previously been described [21,22]. Trephine reaming is not without complications. The teeth on the trephines are quickly worn out during reaming of the well-fixed prosthesis; and so many trephines must be available, particularly if the prosthesis is long. These drill-powered reamers build up considerable heat, and continuous irrigation is necessary to limit devascularization of the endosteal blood supply. Longitudinal fracture of the distal end of a trephine reamer has recently been reported; upon fracture of the reamer, the distal end of the cylindrical blade expanded and proceeded to fracture the femoral cortex [23]. Reconstruction options after a broken longstem uncemented femoral stem with proximal bone loss include calcar-replacing or proximal femur–replacing prostheses [24]; use of bulk and/ or cancellous allograft; and long, distally fixed prostheses that bypass the deficient proximal femur [25]. Busch et al recommend the use of
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a strut allograft in patients with poor proximal femoral bone stock who required an extended trochanteric osteotomy [7]. A proximal femoral allograft was fashioned to replace the proximal femoral bone loss in patient number 1; a cortical strut graft was used in patient number 3 to support the defect in the lateral cortex. All 3 patients received 16-mm–diameter long stem for revision of the broken stems without complications related to the implant. Of the 3 patients in this study, one died immediately postoperatively and one died a year postoperatively, underscoring the importance of attention to medical comorbidities and potential complications that the surgeon must remain cognizant of. The exact morbidity and mortality of patients undergoing revision specifically for broken femoral stems cannot be known because of the infrequency of this complication. However, in revision THA in general, it has been shown that there is a marked increase in the rate of deep vein thrombosis or pulmonary embolism (1.08% vs 0.68%), decubitus ulcer (1.27% vs 0.28%), and postoperative infection (0.25% vs 0.05%); and the in-hospital mortality rate is significantly elevated (0.84% vs 0.33%) [26]. Three broken Echelon stems have previously been reported in the literature. Many of the characteristics that were associated with fractured stems in that series were present in our 3 patients, namely, poor proximal bone support, extended trochanteric osteotomy, and an elevated weight [7]. In addition, use of a smaller stem size (defined as less than 13.5 mm), another risk factor for a broken stem, was present in one of our patients. Use of cerclage wiring and young patient age may have been a factor as well, although larger studies would be needed to support these conclusions. Results of this study add to the literature on this relatively rare complication after revision arthroplasty and help alert the surgeon to the potential risk factors for its occurrence.
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322.e18 The Journal of Arthroplasty Vol. 24 No. 2 February 2009 4. Stark A, Elssner-Beyer T, Wolf L. Operative aspects of prosthesis change in the hip joint after fracture of the prosthesis shaft. Unfallchirurg 1991;94:355. 5. Woolson ST, Milbauer JP, Bobyn JD, et al. Fatigue fracture of a forged cobalt-chromium-molybdenum femoral component inserted with cement. A report of ten cases. J Bone Joint Surg Am 1997;79:1842. 6. Sotereanos NG, Engh CA, Glassman AH, et al. Cementless femoral components should be made from cobalt chrome. Clin Orthop Relat Res 1995:146. 7. Busch CA, Charles MN, Haydon CM, et al. Fractures of distally-fixed femoral stems after revision arthroplasty. J Bone Joint Surg Br 2005;87:1333. 8. Egan KJ, Di Cesare PE. Intraoperative complications of revision hip arthroplasty using a fully porouscoated straight cobalt-chrome femoral stem. J Arthroplasty 1995;10(Suppl):S45. 9. Issack PS, Guerin J, Butler A, et al. Intraoperative complications of revision hip arthroplasty using a porous-coated, distally slotted, fluted femoral stem. Clin Orthop Relat Res 2004:173. 10. Paprosky WG, Greidanus NV, Antoniou J. Minimum 10-year-results of extensively porous-coated stems in revision hip arthroplasty. Clin Orthop Relat Res 1999:230. 11. Moreland JR, Marder R, Anspach Jr WE. The window technique for the removal of broken femoral stems in total hip replacement. Clin Orthop Relat Res 1986:245. 12. Engh CA, Glassman AH, Griffin WL, et al. Results of cementless revision for failed cemented total hip arthroplasty. Clin Orthop Relat Res 1988:91. 13. Charnley J. Fracture of femoral prostheses in total hip replacement. A clinical study. Clin Orthop Relat Res 1975:105. 14. Gruen TA, McNeice GM, Amstutz HC. “Modes of failure” of cemented stem-type femoral components: a radiographic analysis of loosening. Clin Orthop Relat Res 1979:17. 15. Keaveny TM, Bartel DL. Mechanical consequences of bone ingrowth in a hip prosthesis inserted without cement. J Bone Joint Surg Am 1995;77:911.
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