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Failure of the Modular Neck in a Total Hip Arthroplasty
The Journal of Arthroplasty Vol. 25 No. 7 2010
Case Report
Failure of the Modular Neck in a Total Hip Arthroplasty Chris J. Dangles, MD,* and Carl J. Altstetter, ScDy
Abstract: Modular femoral necks in total hip arthroplasty are promoted as giving the surgeon more options during surgery and as being safe. We report a case of fatigue fracture in the modular neck of a femoral implant 3 1/2 years after implantation. The probable design errors leading to product failure are discussed. Keywords: femoral necks, fatigue fracture. © 2010 Elsevier Inc. All rights reserved.
Femoral implant failure in total hip arthroplasty (THA) is rare but has been described in various areas of the implant including the stem, neck, and the modular headneck junction [1-7]. This case report describes the failure of the modular neck in a THA. The modular neck failed where the Morris Taper inserted into the femoral stem. The modular femoral neck implant is a relatively recent design promoted as giving the surgeon more options in controlling leg lengths, offset, and implant stability [8,9].
Case Report A 66-year-old man was received in transfer from the hospital where his primary THA was done 3 1/2 years earlier. The patient arrived in that hospital's emergency department with a broken femoral implant (Fig. 1). The patient experienced a grinding sensation in his hip for about 30 minutes before the onset of extreme pain and inability to walk. He was totally asymptomatic before this occurrence. The patient was an active 280-lb man who is in good health. Revision of the failed THA took place 3 days later when preoperative preparations were complete, including obtaining the original operative report and a variety of revision implants. The primary total hip was a Wright Medical implant (Wright Medical Technology, Inc, Arlington, TN) with modular neck From the *Department of Surgery; Orthopaedic Surgery/Orthopaedics and Rehabilitation, Carle Clinic Association, Champaign, Illinois; and yDepartment of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois. Submitted February 4, 2009; accepted July 12, 2009. No benefits or funds were received in support of the study. Reprint requests: Chris J. Dangles, MD, Department of Surgery, Carle Clinic-Champaign on Mattis, 1802 S Mattis Avenue, Champaign, IL 61821. © 2010 Elsevier Inc. All rights reserved. 0883-5403/2507-0033$36.00/0 doi:10.1016/j.arth.2009.07.015
and metal on metal bearing. At revision surgery, the implant was found to be well osteointegrated and difficult to remove. An extended trochanteric osteotomy was required to remove the femoral component. It was decided preoperatively not to extract the broken modular neck from the femoral component because failure might occur again in the future. The acetabulum was revised because the position was considered suboptimal. The failed modular neck was the longest neck size available for this implant, and it was inserted in retroversion. Six months after revision, the patient is walking with a slight limp that disappears when he uses a cane. He is riding a motorcycle. His osteotomy is well healed (Fig. 2). He is not complaining of pain.
Discussion A metallurgical engineer was consulted to examine the failed implant. A close-up of the 2 halves of the fractured piece is shown in Fig. 4. Some damage on the upper half was incurred in the attempt to remove the femoral component from the femur. A detail of the surface of the lower piece in Fig. 3 is shown in Fig. 4. The failure occurred from an initiation site that was anterior and superior. Apparent on the surface are concentric curved lines centered at a point on the perimeter (arrow, Fig. 4). These are indicative of failure by fatigue, in which a crack is initiated at the surface at a point of high stress and propagates inward as the material is repeatedly loaded. At some point, the remaining uncracked material is fractured rapidly upon a further application of load. There was degradation of the polished surface where it was inserted into the femoral component. There was evidence of abrasion and corrosion, indicating that initiation and propagation of the fatigue crack could have been corrosion assisted, that is, corrosion fatigue. The corrosion process could have been initiated by body fluids, and the confined space between the tapered piece and the
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Fig. 3. Photograph of the two halves of the failed modular neck. (A) Encircled area showing circular artifacts created during extraction process.
Fig. 1. Radiograph of the patient's prosthesis at presentation. (A) Anteroposterior view.
femoral component would have been anaerobic, leading to breakdown of passivity of the metal and its subsequent deterioration.
Implant failure is a known occurrence. The benefits of modularity must be shown to outweigh the risks of this failure pattern. Long-term follow-up will reveal if modular neck designs have the same durability in vivo as they do in laboratory testing [10,11]. The Federal Drug Administration Manufacturer and User Facility Device Experience (FDA MAUDE) database from the year January 1, 2000, to May 19, 2009, contains 98 adverse event reports concerning the Profemur modular femoral neck prosthesis. Thirty-seven of these complaints clearly describe breakage of the modular femoral neck [12]. With regard to the failed prosthesis in question, based upon the metallurgist's analysis, there is a question as to whether or not the product design was imperfect based on the following: 1. The neck was an offset neck thereby increasing the bending load on the neck. 2. The portion of the neck that was inserted in the femoral stem was in a narrow, confined space that is capable of promoting corrosion resulting in failure.
Fig. 2. Radiograph of the revision prosthesis. (A) Anteroposterior view.
Fig. 4. Detail of fracture surface of tapered piece. (A) Arrow indicates apparent point of origin of failure, partly obscured by subsequent damage.
Failure of the Modular Neck in a THA Dangles and Altstetter
The benefits of modularity allow for intraoperative adjustments to promote optimal positioning of the prosthesis. This should improve stability, decrease the dislocation rate, and assist in equalization of leg length. However, a well-fitting prosthesis that fails within a few years is neither what the patient reasonably expects or what is acceptable performance. Although the surgeon is not responsible for the design of a prosthesis, it is urged that surgeons consider potential design flaws when they are published in the literature.
References 1. Heck DA, Partridge CM, Reuben JD, et al. Prosthetic component failures in hip arthroplasty surgery. J Arthroplasty 1995;10:575. 2. Rand JA, Chao EY. Femoral implant neck fracture following total hip arthroplasty. Clin Orthop Relat Res 1987;221:255. 3. Lam LO, Stoffel K, Swarts E. Catastrophic failure of 4 colbalt-alloy Omnifit hip arthroplasty femoral components. Acta Orthop 2008;79:18. 4. Della Valle AG, Becksac B, Anderson J, et al. Late fatigue fracture of a modern cemented cobalt chrome stem for total hip arthroplasty: a report of 10 cases. J Arthroplasty 2006; 21:1080 [author reply 1080].
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5. Gilbert JL, Buckley CA, Jacobs JJ, et al. Intergranular corrosion-fatigue failure of colbalt-alloy femoral stems. J Bone Joint Surg Am 1994;76-A:110. 6. Woolson ST, Stanford JP, Milbauer JP, et al. Fatigue fracture of a forged cobalt-chromium-molybdenum femoral component inserted with cement. J Bone Joint Surg Am 1997; 79-A:1842. 7. Botti TP, Gent J, Martell JM, et al. Trunion fracture of a fully porous-coated femoral stem- a case report. J Arthroplasty 2005;20:943. 8. Murphy SB. Managing length and stability: The role of the modular neck. Presented at the 24th Annual Current Concepts in Joint Replacement Winter Meeting. December, 2007; Orlando, FL. 2007. 9. Technical Monograph published by Wright Medical Technology, Inc. ProFemur Total Hip System, Modular Neck. 2003. 10. Traina F, Baleani M, Eng M, et al. Modular neck primary prosthesis: experimental and clinical outcomes. Scientific Exhibit at the 71st AAOS Meeting. March, 2004; San Francisco, CA. 2004. 11. Viceconti M, Ruggeri O, Toni A, et al. Design-related fretting wear in modular neck hip prosthesis. J Biomed Mater Res 1996;30:181. 12. Medical devices, MAUDE database, http://www.fda.gov/ search/databases.html; http://www.accessdata.fda.gov/ scripts/cdrh/cfdocs/cfMAUDE/search.cfm.
Case Report
Failure of the Modular Neck in a Total Hip Arthroplasty Chris J. Dangles, MD,* and Carl J. Altstetter, ScDy
Abstract: Modular femoral necks in total hip arthroplasty are promoted as giving the surgeon more options during surgery and as being safe. We report a case of fatigue fracture in the modular neck of a femoral implant 3 1/2 years after implantation. The probable design errors leading to product failure are discussed. Keywords: femoral necks, fatigue fracture. © 2010 Elsevier Inc. All rights reserved.
Femoral implant failure in total hip arthroplasty (THA) is rare but has been described in various areas of the implant including the stem, neck, and the modular headneck junction [1-7]. This case report describes the failure of the modular neck in a THA. The modular neck failed where the Morris Taper inserted into the femoral stem. The modular femoral neck implant is a relatively recent design promoted as giving the surgeon more options in controlling leg lengths, offset, and implant stability [8,9].
Case Report A 66-year-old man was received in transfer from the hospital where his primary THA was done 3 1/2 years earlier. The patient arrived in that hospital's emergency department with a broken femoral implant (Fig. 1). The patient experienced a grinding sensation in his hip for about 30 minutes before the onset of extreme pain and inability to walk. He was totally asymptomatic before this occurrence. The patient was an active 280-lb man who is in good health. Revision of the failed THA took place 3 days later when preoperative preparations were complete, including obtaining the original operative report and a variety of revision implants. The primary total hip was a Wright Medical implant (Wright Medical Technology, Inc, Arlington, TN) with modular neck From the *Department of Surgery; Orthopaedic Surgery/Orthopaedics and Rehabilitation, Carle Clinic Association, Champaign, Illinois; and yDepartment of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois. Submitted February 4, 2009; accepted July 12, 2009. No benefits or funds were received in support of the study. Reprint requests: Chris J. Dangles, MD, Department of Surgery, Carle Clinic-Champaign on Mattis, 1802 S Mattis Avenue, Champaign, IL 61821. © 2010 Elsevier Inc. All rights reserved. 0883-5403/2507-0033$36.00/0 doi:10.1016/j.arth.2009.07.015
and metal on metal bearing. At revision surgery, the implant was found to be well osteointegrated and difficult to remove. An extended trochanteric osteotomy was required to remove the femoral component. It was decided preoperatively not to extract the broken modular neck from the femoral component because failure might occur again in the future. The acetabulum was revised because the position was considered suboptimal. The failed modular neck was the longest neck size available for this implant, and it was inserted in retroversion. Six months after revision, the patient is walking with a slight limp that disappears when he uses a cane. He is riding a motorcycle. His osteotomy is well healed (Fig. 2). He is not complaining of pain.
Discussion A metallurgical engineer was consulted to examine the failed implant. A close-up of the 2 halves of the fractured piece is shown in Fig. 4. Some damage on the upper half was incurred in the attempt to remove the femoral component from the femur. A detail of the surface of the lower piece in Fig. 3 is shown in Fig. 4. The failure occurred from an initiation site that was anterior and superior. Apparent on the surface are concentric curved lines centered at a point on the perimeter (arrow, Fig. 4). These are indicative of failure by fatigue, in which a crack is initiated at the surface at a point of high stress and propagates inward as the material is repeatedly loaded. At some point, the remaining uncracked material is fractured rapidly upon a further application of load. There was degradation of the polished surface where it was inserted into the femoral component. There was evidence of abrasion and corrosion, indicating that initiation and propagation of the fatigue crack could have been corrosion assisted, that is, corrosion fatigue. The corrosion process could have been initiated by body fluids, and the confined space between the tapered piece and the
1169.e5
1169.e6 The Journal of Arthroplasty Vol. 25 No. 7 October 2010
Fig. 3. Photograph of the two halves of the failed modular neck. (A) Encircled area showing circular artifacts created during extraction process.
Fig. 1. Radiograph of the patient's prosthesis at presentation. (A) Anteroposterior view.
femoral component would have been anaerobic, leading to breakdown of passivity of the metal and its subsequent deterioration.
Implant failure is a known occurrence. The benefits of modularity must be shown to outweigh the risks of this failure pattern. Long-term follow-up will reveal if modular neck designs have the same durability in vivo as they do in laboratory testing [10,11]. The Federal Drug Administration Manufacturer and User Facility Device Experience (FDA MAUDE) database from the year January 1, 2000, to May 19, 2009, contains 98 adverse event reports concerning the Profemur modular femoral neck prosthesis. Thirty-seven of these complaints clearly describe breakage of the modular femoral neck [12]. With regard to the failed prosthesis in question, based upon the metallurgist's analysis, there is a question as to whether or not the product design was imperfect based on the following: 1. The neck was an offset neck thereby increasing the bending load on the neck. 2. The portion of the neck that was inserted in the femoral stem was in a narrow, confined space that is capable of promoting corrosion resulting in failure.
Fig. 2. Radiograph of the revision prosthesis. (A) Anteroposterior view.
Fig. 4. Detail of fracture surface of tapered piece. (A) Arrow indicates apparent point of origin of failure, partly obscured by subsequent damage.
Failure of the Modular Neck in a THA Dangles and Altstetter
The benefits of modularity allow for intraoperative adjustments to promote optimal positioning of the prosthesis. This should improve stability, decrease the dislocation rate, and assist in equalization of leg length. However, a well-fitting prosthesis that fails within a few years is neither what the patient reasonably expects or what is acceptable performance. Although the surgeon is not responsible for the design of a prosthesis, it is urged that surgeons consider potential design flaws when they are published in the literature.
References 1. Heck DA, Partridge CM, Reuben JD, et al. Prosthetic component failures in hip arthroplasty surgery. J Arthroplasty 1995;10:575. 2. Rand JA, Chao EY. Femoral implant neck fracture following total hip arthroplasty. Clin Orthop Relat Res 1987;221:255. 3. Lam LO, Stoffel K, Swarts E. Catastrophic failure of 4 colbalt-alloy Omnifit hip arthroplasty femoral components. Acta Orthop 2008;79:18. 4. Della Valle AG, Becksac B, Anderson J, et al. Late fatigue fracture of a modern cemented cobalt chrome stem for total hip arthroplasty: a report of 10 cases. J Arthroplasty 2006; 21:1080 [author reply 1080].
1169.e7
5. Gilbert JL, Buckley CA, Jacobs JJ, et al. Intergranular corrosion-fatigue failure of colbalt-alloy femoral stems. J Bone Joint Surg Am 1994;76-A:110. 6. Woolson ST, Stanford JP, Milbauer JP, et al. Fatigue fracture of a forged cobalt-chromium-molybdenum femoral component inserted with cement. J Bone Joint Surg Am 1997; 79-A:1842. 7. Botti TP, Gent J, Martell JM, et al. Trunion fracture of a fully porous-coated femoral stem- a case report. J Arthroplasty 2005;20:943. 8. Murphy SB. Managing length and stability: The role of the modular neck. Presented at the 24th Annual Current Concepts in Joint Replacement Winter Meeting. December, 2007; Orlando, FL. 2007. 9. Technical Monograph published by Wright Medical Technology, Inc. ProFemur Total Hip System, Modular Neck. 2003. 10. Traina F, Baleani M, Eng M, et al. Modular neck primary prosthesis: experimental and clinical outcomes. Scientific Exhibit at the 71st AAOS Meeting. March, 2004; San Francisco, CA. 2004. 11. Viceconti M, Ruggeri O, Toni A, et al. Design-related fretting wear in modular neck hip prosthesis. J Biomed Mater Res 1996;30:181. 12. Medical devices, MAUDE database, http://www.fda.gov/ search/databases.html; http://www.accessdata.fda.gov/ scripts/cdrh/cfdocs/cfMAUDE/search.cfm.