- Email: [email protected]
Femoral neck modularity: A bridge too far
SE
M I N A R S I N
A
R T H R O P L A S T Y
24 (2013) 71–75
Available online at www.sciencedirect.com
www.elsevier.com/locate/semanthroplasty
Femoral neck modularity: A bridge too far Alexander E. Weber, MDn, and John D. Blaha, MD Department of Orthopaedic Surgery, University of Michigan, 2912 Taubman Center, SPC 5328, 1500 E. Medical Center Dr, Ann Arbor, MI
AR T IC LE INFO
AB STR A C T Modular femoral neck use in total hip arthroplasty (THA) affords the operating surgeon
Keywords:
increased intra-operative flexibility with regard to offset, version, and leg length. Propo-
modular femoral neck
nents also advocate a reduced dislocation rate, reduced impingement issues, and ease of
total hip arthroplasty
revision of acetabular component, head, or neck. However, the increased intra-operative
implant design
flexibility and potential postoperative advantages come at a significant price. Adverse
implant complications
events and complications associated with modular femoral neck usage are being reported
implant failure
with increasing frequency. Modular femoral neck fractures as a result of patient- and
corrosion
implant-related factors are prevalent. Corrosion at the neck–stem interface is associated with a number of sequelae, including osteolysis, synovitis, adverse local tissue reactions (ALTRs), and aseptic lymphocyte-laminated vascular-associated lesions (ALVAL). Systemic complications of metallosis are also pertinent following corrosion at the neck–stem junction. Failure to disassemble the neck from the stem due to corrosion and cold welding is a documented complication and obviates a potential benefit of modularity at the time of revision. Modular femoral necks have a twofold increase in overall revision rate in the Australian registry data as compared to fixed-neck stems. Lastly, modular femoral necks add significant cost to each THA. The purpose of this review article is to discuss the current state of femoral neck modularity and provide the readership with pause prior to the continued use of modular femoral neck THA. Given the current and emerging literature, the modular femoral neck is a bridge too far. & 2013 Elsevier Inc. All rights reserved.
1.
Introduction
The increased use of modularity in total hip arthroplasty (THA) occurred in the late 1980s and early 1990s due to a series of studies describing the variability in leg length, version, and offset of the lower extremity and hip [1,2]. The described intra-operative advantages of modularity are the ability to independently adjust the aforementioned variables of leg length, offset, and version [3–7]. The theoretical postoperative advantages owing to intra-operative flexibility include decreased dislocation rates and decreased mechanical impingement [3–7]. In addition, authors have advocated that in an era of minimally invasive THA, neck modularity
affords the surgeon the ability to “build” the implants in situ through smaller incisions [8]. Proponents of the modular neck also discuss the ease of revision in cases of acetabular component, liner or head revision in the face of a well-fixed stem. Lastly, authors have noted the potential for decreased component inventory given the increased intra-operative flexibility [3]. Interestingly, it was not long after the first description of modularity that concerns began to arise [4,9–13]. Early designs of the modular taper lent themselves to fretting and crevice corrosion. Modifications to implant materials initially quelled concerns regarding the degradation process. These design modifications led to a period of relative neutrality regarding usage of
Dr. Blaha is a paid consultant for and receives royalties from Wright Medical Technology, Inc. n Address reprint requests to Alexander E. Weber, MD, Department of Orthopaedic Surgery, University of Michigan, 2912 Taubman Center, SPC 5328, 1500 E. Medical Center Dr., Ann Arbor, MI 48109. E-mail address: [email protected] (A.E. Weber). 1045-4527/$ - see front matter & 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.sart.2013.07.001
72
SEM
I N A R S I N
A
R T H R O P L A S T Y
the modular neck in THA [14]. However, clinical failures began to mount in the literature: unintentional dissociation of neck from stem, failures to disassemble neck from stem during revision surgery, modular neck fractures, corrosion, and the sequelae thereof [8,15–26]. These results led to renewed interest in the mechanisms of these clinical failures, the results of which are outlined below.
2.
Modular femoral neck fracture
The adverse clinical outcome of modular neck fracture is relatively rare; however, the frequency of case reports has increased [15,16,18,21,22,27]. One large case series exists in which 5000 titanium (Ti) modular neck THAs were evaluated and an incidence of adverse outcomes of 1.4% was reported [19]. Since then a multitude of case reports and case series has entered the literature [20,21,23,26,27]. Several patient, surgeon, and implant factors have been hypothesized to contribute to adverse outcomes. Contributing patient factors may include male gender and patient weight greater than 100 kg [15,19,21,22]. Surgeon factors are related to the technique of implantation, taking care to impact the neck into the stem as accurately as possible and ensuring that all debris (bone chips) and liquid (blood and irrigant) are removed from the stem prior to impacting the neck [19,28]. Jauch et al. [28], in a controlled biomechanical experiment, demonstrated that debriscontaminated modular necks had increased micromotion compared to clean interfaces and that Ti components had significantly higher micromotion than cobalt–chromium (CoCr) components under comparable conditions. They postulated that increased micromotion leads to fretting and fatigue failures [28]. The implant-related factors appear to be numerous [15,19,22,24]. All other factors being equal, Ti neck implants have been postulated to fail due to fracture more frequently than CoCr necks, given the lower modulus of elasticity for titanium [29]. The use of “long varus” necks and implants with neck-shaft angles greater than 1351 may increase the bending moment causing mechanical stress on the neck–stem junction. This increase in mechanical stress has been implicated as a cause of micromotion, corrosion, and neck fracture [15,19,22,24,30]. Skendzel et al. [15] reported on two cases of “long varus” modular neck fractures and cited a 32.7% increase in the bending moment as compared to the standard “short varus” neck. Although a much less frequent occurrence, fracture of a metaphyseal–diaphyseal modular femoral system may also occur. In a retrospective review of this type of implant, Lakstein et al. [31] reported on three implants with six mid-stem fractures. After a microscopic evaluation of the components, the authors postulated that fretting fatigue had caused the fractures and that increased patient weight and a lack of proximal bone stock were associated risk factors for fracture [31]. The importance of adequate bone stock was further emphasized in the presence of modular junctions by Chu and colleagues [32] through the use of a finite element model of the modular interface in the presence and absence of stable osseous support. Their results suggest that in the absence of adequate bone stock, the peak stress across modular interface was increased 45% [32].
3.
24 (2013) 71–75
Modular femoral neck corrosion
Corrosion has been examined at both the femoral head–neck junction and the femoral neck–stem junction [3,4,10,12,19,33– 35]. Both CoCr and Ti implants form a biocompatible passivation layer that confers some degree of corrosion resistance in its intact state [28,36]. The process of corrosion typically begins with micromotion at the neck–stem interface due to the higher loads experienced at this junction as compared to the neck–head junction [19,24,28,35,37]. Micromotion leads to the mechanical removal of the passivation layer on the surface of the components and creates a local environment ripe for the propagation of corrosion [38]. Both CoCr and Ti implants are then susceptible to fretting and crevice corrosion. In the case of Ti implants, the loss of the passivation layer allows for not only crevice corrosion but also hydrogen embrittlement, a process that significantly weakens the material [9,38]. The end results for both CoCr and Ti implants are an increased propensity to fatigue failure and fracture as discussed previously. Furthermore, the corrosion process is not without its effects on the biologic environment as well. The end-products of the corrosion lead to an increase in metal debris that may act locally within the bone and soft tissues as well as systemically at the end organs [9]. There are currently conflicting reports on the degree of corrosion, given the material coupling. Research of the head– neck junction has demonstrated that corrosion and fretting have been documented in mixed metal systems (CoCr neck with Ti stem) and in the presence of similar material couplings [24,26,33,35,38–40]. Some groups have advocated the use of CoCr rather than Ti due to lower micromotion and increased fatigue strength [19,28], whereas other studies have found contradictory results [41]. Kop et al. [41] examined 57 modular necks and found that 62% of the CoCr components and 30% of the Ti components exhibited signs of corrosion. Ninety percent of the CoCr and 50% of the Ti components exhibited signs of fretting [41]. The severity of corrosion and fretting was greater at the neck–stem interface as compared to the head–neck interface [41]. Ultimately, there is no definitive answer as to which metal combination is safest or whether there are significant advantages to using two dissimilar metals at an interface. Both CoCr and Ti modular necks have a high propensity for fretting and crevice corrosion and the treating surgeon must be prepared to share these results with those treated with a modular THA. Furthermore, the treating surgeon must warn patients that corrosion positively correlates with duration of implant retention [33,34].
4.
Failure to disassemble
An additional complication of Ti–Ti modular neck–stem interfaces is the failure to disassemble the neck from the stem at the time of revision. Fraitzl et al. [26] performed a retrieval study of 22 Ti modular neck devices and found that seven (32%) necks would not disengage from the stems. Kop et al. [41] found that of the 57 retrieved modular devices, failure to disassemble was noted in 22% of the Ti devices.
S
E M I N A R S I N
AR
T H R O P L A S T Y
In both studies corrosion and cold welding of the neck–stem interface was documented as the etiology for failure to disassemble. These results completely obviate one of the proposed benefits of femoral neck modularity, that of ease of head or neck revision in the presence of a well-fixed stem. Cold welding of the neck to stem and failure to disassemble may lead to the increased morbidity of extensile approaches, extended trochanteric osteotomy, and in some cases, return visits to the operating room. The treating surgeon should be aware of this potential complication and anticipate alternative surgical procedures.
5.
Local effects of modular neck corrosion
Much attention has been paid to metal-on-metal (MOM) articulations and the head–neck interface as potential sources of systemic increases in metal debris and adverse local tissue reactions (ALTRs) [42–46]. The neck–stem interface is not as well studied in this regard; however, given the increased mechanical stress, micromotion, and corrosion at the neck–stem interface as compared to the head–neck interface, it is appropriate to extrapolate from the head–neck body of literature [28,41]. If anything, given the higher mechanical forces dissipated through the neck–stem junction and the increased micromotion at this interface, the local and systemic effects of corrosion at the neck– stem junction should be multiplied as compared to lessons learned from the head–neck junction. Locally, head–neck taper corrosion has been associated with synovitis and osteolysis [9,33,40]. In addition to intra-articular synovitis and osteolysis, extra-articular ALTRs have been described in the modular neck literature [41,47–50]. Garbuz et al. [47], in the Charnley Award paper of 2010, found that CoCr modular neck implant patients had higher serum cobalt and chromium ion levels as compared to levels in patients who underwent hip resurfacing. Furthermore, the authors were able to attribute the higher metal ion levels to corrosion occurring at the neck–stem interface [47]. In the Kop et al. [41] retrieval study of 57 modular neck THAs, the authors noted that eight of the 57 patients had metallosis (seven CoCr devices and one Ti device) with two confirmed cases of aseptic lymphocyte-laminated vascular-associated lesions (ALVALs), both in CoCr devices. To our knowledge there are presently three case reports (five total patients) in the orthopedic literature of ALTRs associated with modular femoral necks [48–50]. All five patients underwent modular THA with a CoCr neck and a Ti stem and developed pain associated with metal artifact reduction sequence magnetic resonance imaging evidence of ALTR consistent with metal debris hypersensitivity and inflammatory reaction [48–50].
6.
Systemic effects of modular neck corrosion
There is currently a paucity of data regarding the systemic sequelae of neck–stem corrosion and metal debris. Similar to the local sequelae, there is no reason to believe that the systemic results of corrosion at the head–neck junction should not be extrapolated to the neck–stem junction. The corrosion products from the head–neck taper have been found to accumulate in end-stage organs [51]. Oldenburg et al. [52] linked corrosion to
24 (2013) 71–75
73
excess serum and urine levels of cobalt and implicated the increased ion levels in the development of thyroiditis, auditory disturbance, and granulomatous lesions. In the MOM articulation, cobalt corrosion debris has also been linked with neurologic and cardiac adverse outcomes [52–55]. Again, given that the corrosion end-products are equivalent between articulation and neck–stem interface, it is prudent for the surgeon to be aware of all the potential complications of modular neck usage.
7.
Healthcare-associated concerns
With the current trends in healthcare spending and reduction in reimbursements, all healthcare decisions should be examined carefully for their cost and effectiveness. Strictly from a cost perspective, a group of surgeons at a high-volume large academic institute estimated that using a modular stem may increase the cost of THA by 25% compared to a standard stem THA [56]. The increased cost of modular neck THA at a lowvolume hospital is likely even higher. From an effectiveness perspective, it is crucial to closely examine where the potential intra-operative benefits of femoral neck modularity outweigh the documented risks. To our knowledge, there are no Level I or II studies in which a cohort of modular neck THA patients outperformed a cohort of conventional THA patients in terms of dislocation rate, prosthetic impingement, need for revision, or subjective clinical outcomes. In the primary and standard revision THA settings, there is strong opposition to the use of the modular femoral neck [57,58]. Modular femoral necks have been advocated in cases of hip dysplasia or increased femoral anteversion [7,59–61]. However, the treating surgeon must be prepared to discuss all of the previously mentioned complications and adverse outcomes. In addition, there are now registry data that suggest the overall revision rate for modular femoral neck THA is double that of fixed-neck THA (8.9% vs. 4.2%) [5,62].
8.
Our institutional experience
We have recently reported on our institution's experience with modular neck complications [63]. In our series of patients with modular Ti–Ti neck–stem interfaces, we experienced one case of neck taper fracture, two cases of failure to disassemble, and multiple cases of corrosion. Interestingly, five of the six cases presented with acute onset of pain and radiographic evidence of pneumarthrosis. After infection was ruled out, an aspiration of the pneumarthrosis and subsequent mass spectrometry of the sample demonstrated an abnormally high concentration of hydrogen gas. Based on the high concentration of intraarticular hydrogen gas, physical evidence of corrosion at the time of revision, and the process of hydrogen embrittlement described previously [38], we concluded that the clinical scenario of acute onset of pain, radiographic evidence of pneumarthrosis and absence of infection in a patient who has undergone modular neck THA may be an early indicator of underlying crevice corrosion. The treating surgeon should be aware of this clinical constellation and that it may be an indicator of the impending additional complications of difficulty removing neck
74
SEM
I N A R S I N
A
R T H R O P L A S T Y
from stem, fracture of the implant, and/or the local and systemic sequelae of metallosis.
9.
Conclusion
Although femoral neck modularity affords the surgeon additional intra-operative options as compared to the standard fixedneck implants, the treating surgeon must consider if the intraoperative convenience outweighs the increased risk of femoral neck fracture, failure to disassemble, corrosion, metallosis, and an overall twofold increase in revision rate. On the basis of the current and emerging literature as well as our clinical experience we believe the modular neck is a bridge too far.
10.
Disclosure
The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.
r e f e r e n c e s
[1] Noble PC, Box GG, Kamaric E, Fink MJ, Alexander JW, Tullos HS. The effect of aging on the shape of the proximal femur. Clin Orthop Relat Res. 1995:31–44. [2] Noble PC, Alexander JW, Lindahl LJ, Yew DT, Granberry WM, Tullos HW. The anatomic basis of femoral component design. Clin Orthop Relat Res. 1988:148–65. [3] Collier JP, Mayor MB, Williams IR, Surprenant VA, Surprenant HP, Currier BH. The tradeoffs associated with modular hip prostheses. Clin Orthop Relat Res. 1995:91–101. [4] Cook SD, Barrack RL, Baffes GC, Clemow AJ, Serekian P, Dong N, et al. Wear and corrosion of modular interfaces in total hip replacements. Clin Orthop Relat Res. 1994:80–8. [5] Archibeck MJ, Cummins T, Carothers J, Junick DW, White Jr RE. A comparison of two implant systems in restoration of hip geometry in arthroplasty. Clin Orthop Relat Res. 2011;469:443–6. [6] Matsushita A, Nakashima Y, Fujii M, Sato T, Iwamoto Y. Modular necks improve the range of hip motion in cases with excessively anteverted or retroverted femurs in THA. Clin Orthop Relat Res. 2010;468:3342–7. [7] Sakai T, Ohzono K, Nishii T, Miki H, Takao M, Sugano N. A modular femoral neck and head system works well in cementless total hip replacement for patients with developmental dysplasia of the hip. J Bone Joint Surg Br. 2010;92:770–6. [8] Dunbar MJ. The proximal modular neck in THA: a bridge too far: affirms. Orthopedics. 2010;33:640. [9] Jacobs JJ, Urban RM, Gilbert JL, Skipor AK, Black J, Jasty M, et al. Local and distant products from modularity. Clin Orthop Relat Res. 1995:94–105. [10] Collier JP, Surprenant VA, Jensen RE, Mayor MB. Corrosion at the interface of cobalt-alloy heads on titanium-alloy stems. Clin Orthop Relat Res. 1991:305–12. [11] Collier JP, Mayor MB, Jensen RE, Surprenant VA, Surprenant HP, McNamar JL, et al. Mechanisms of failure of modular prostheses. Clin Orthop Relat Res. 1992:129–39. [12] Collier JP, Surprenant VA, Jensen RE, Mayor MB, Surprenant HP. Corrosion between the components of modular femoral hip prostheses. J Bone Joint Surg Br. 1992;74:511–7.
24 (2013) 71–75
[13] Mathiesen EB, Lindgren JU, Blomgren GG, Reinholt FP. Corrosion of modular hip prostheses. J Bone Joint Surg Br. 1991;73: 569–75. [14] Blaha JD. The modular neck: keystone to functional restoration. Orthopedics. 2006;29:804–5. [15] Skendzel JG, Blaha JD, Urquhart AG. Total hip arthroplasty modular neck failure. J Arthroplasty. 2011;26:338 [e331–e334]. [16] Atwood SA, Patten EW, Bozic KJ, Pruitt LA, Ries MD. Corrosion-induced fracture of a double-modular hip prosthesis: a case report. J Bone Joint Surg Am. 2010;92:1522–5. [17] Cooper HJ, Della Valle CJ, Berger RA, Tetreault M, Paprosky WG, Sporer SM, et al. Corrosion at the head–neck taper as a cause for adverse local tissue reactions after total hip arthroplasty. J Bone Joint Surg Am. 2012;94:1655–61. [18] Ellman MB, Levine BR. Fracture of the modular femoral neck component in total hip arthroplasty. J Arthroplasty. 2013;28:196 [e191–e195]. [19] Grupp TM, Weik T, Bloemer W, Knaebel HP. Modular titanium alloy neck adapter failures in hip replacement—failure mode analysis and influence of implant material. BMC Musculoskelet Disord. 2010;11:3. [20] Sporer SM, DellaValle C, Jacobs J, Wimmer M. A case of disassociation of a modular femoral neck trunion after total hip arthroplasty. J Arthroplasty. 2006;21:918–21. [21] Wilson DA, Dunbar MJ, Amirault JD, Farhat Z. Early failure of a modular femoral neck total hip arthroplasty component: a case report. J Bone Joint Surg Am. 2010;92:1514–7. [22] Wright G, Sporer S, Urban R, Jacobs J. Fracture of a modular femoral neck after total hip arthroplasty: a case report. J Bone Joint Surg Am. 2010;92:1518–21. [23] Gill IP, Webb J, Sloan K, Beaver RJ. Corrosion at the neck– stem junction as a cause of metal ion release and pseudotumour formation. J Bone Joint Surg Br. 2012;94:895–900. [24] Kop AM, Swarts E. Corrosion of a hip stem with a modular neck taper junction: a retrieval study of 16 cases. J Arthroplasty. 2009;24:1019–23. [25] Kretzer JP, Jakubowitz E, Krachler M, Thomsen M, Heisel C. Metal release and corrosion effects of modular neck total hip arthroplasty. Int Orthop. 2009;33:1531–6. [26] Fraitzl CR, Moya LE, Castellani L, Wright TM, Buly RL. Corrosion at the stem–sleeve interface of a modular titanium alloy femoral component as a reason for impaired disengagement. J Arthroplasty. 2011;26:113–9 [119–e111]. [27] Dangles CJ, Altstetter CJ. Failure of the modular neck in a total hip arthroplasty. J Arthroplasty. 2010;25:1169 [e1165–e1167]. [28] Jauch SY, Huber G, Hoenig E, Baxmann M, Grupp TM, Morlock MM. Influence of material coupling and assembly condition on the magnitude of micromotion at the stem-neck interface of a modular hip endoprosthesis. J Biomech. 2011;44:1747–51. [29] Bobyn JD, Mortimer ES, Glassman AH, Engh CA, Miller JE, Brooks CE. Producing and avoiding stress shielding. Laboratory and clinical observations of noncemented total hip arthroplasty. Clin Orthop Relat Res. 1992:79–96. [30] Wright Medical Technology: A Safety Alert. The use of modular necks in total hip replacement. Arlington, TN: Wright Medical Technology, Inc., 2008. [31] Lakstein D, Eliaz N, Levi O, Backstein D, Kosashvili Y, Safir O, et al. Fracture of cementless femoral stems at the mid-stem junction in modular revision hip arthroplasty systems. J Bone Joint Surg Am. 2011;93:57–65. [32] Chu Y, Elias JJ, Duda GN, Frassica FJ, Chao EY. Stress and micromotion in the taper lock joint of a modular segmental bone replacement prosthesis. J Biomech. 2000;33:1175–9. [33] Goldberg JR, Gilbert JL, Jacobs JJ, Bauer TW, Paprosky W, Leurgans S. A multicenter retrieval study of the taper interfaces of modular hip prostheses. Clin Orthop Relat Res. 2002:149–61.
S
E M I N A R S I N
AR
T H R O P L A S T Y
[34] Salvati EA, Lieberman JR, Huk OL, Evans BG. Complications of femoral and acetabular modularity. Clin Orthop Relat Res. 1995:85–93. [35] Gilbert JL, Buckley CA, Jacobs JJ. In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling. J Biomed Mater Res. 1993;27:1533–44. [36] Swaminathan V, Gilbert JL. Fretting corrosion of CoCrMo and Ti6Al4V interfaces. Biomaterials. 2012;33:5487–503. [37] Brown SA, Hughes PJ, Merritt K. In vitro studies of fretting corrosion of orthopaedic materials. J Orthop Res. 1988;6:572–9. [38] Rodrigues DC, Urban RM, Jacobs JJ, Gilbert JL. In vivo severe corrosion and hydrogen embrittlement of retrieved modular body titanium alloy hip-implants. J Biomed Mater Res B Appl Biomater. 2009;88:206–19. [39] Goldberg JR, Gilbert JL. In vitro corrosion testing of modular hip tapers. J Biomed Mater Res B Appl Biomater. 2003;64:78–93. [40] Brown SA, Flemming CA, Kawalec JS, Placko HE, Vassaux C, Merritt K, et al. Fretting corrosion accelerates crevice corrosion of modular hip tapers. J Appl Biomater. 1995;6:19–26. [41] Kop AM, Keogh C, Swarts E. Proximal component modularity in THA—at what cost? An implant retrieval study. Clin Orthop Relat Res. 2012;470:1885–94. [42] Biant LC, Bruce WJ, van der Wall H, Walsh WR. Infection or allergy in the painful metal-on-metal total hip arthroplasty? J Arthroplasty. 2010;25:334 [e311–e336]. [43] Mikhael MM, Hanssen AD, Sierra RJ. Failure of metal-onmetal total hip arthroplasty mimicking hip infection. A report of two cases. J Bone Joint Surg Am. 2009;91:443–6. [44] Watters TS, Eward WC, Hallows RK, Dodd LG, Wellman SS, Bolognesi MP. Pseudotumor with superimposed periprosthetic infection following metal-on-metal total hip arthroplasty: a case report. J Bone Joint Surg Am. 2010;92:1666–9. [45] Kwon YM, Thomas P, Summer B, Pandit H, Taylor A, Beard D, et al. Lymphocyte proliferation responses in patients with pseudotumors following metal-on-metal hip resurfacing arthroplasty. J Orthop Res. 2010;28:444–50. [46] Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons CL, et al. Pseudotumours associated with metalon-metal hip resurfacings. J Bone Joint Surg Br. 2008;90: 847–51. [47] Garbuz DS, Tanzer M, Greidanus NV, Masri BA, Duncan CP. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res. 2010;468:318–25. [48] Hsu AR, Gross CE, Levine BR. Pseudotumor from modular neck corrosion after ceramic-on-polyethylene total hip arthroplasty. Am J Orthop (Belle Mead, NJ). 2012;41:422–6.
24 (2013) 71–75
75
[49] Patel AR, Patel RM, Thomas D, Bauer TW, Stulberg SD. Caveat emptor: adverse inflammatory soft-tissue reactions in total hip arthroplasty with modular femoral neck implants: a report of two cases. JBJS Case Connector. 2012;2:e80. [50] Werner SD, Bono JV, Nandi S, Ward DM, Talmo CT. Adverse tissue reactions in modular exchangeable neck implants: a report of two cases. J Arthroplasty. 2013;28:543 [e513–e545]. [51] Urban RM, Jacobs JJ, Tomlinson MJ, Gavrilovic J, Black K, Peoch M. Dissemination of wear particles to the liver, spleen, and abdominal lymph nodes of patients with hip or knee replacement. J Bone Joint Surg Am. 2000;82:457–76. [52] Oldenburg M, Wegner R, Baur X. Severe cobalt intoxication due to prosthesis wear in repeated total hip arthroplasty. J Arthroplasty. 2009;24(825):e815–20. [53] Tower S. Arthroprosthetic cobaltism: identification of the atrisk patient. Alaska Med. 2010;52:28–32. [54] Rizzetti MC, Liberini P, Zarattini G, Catalani S, Pazzaglia U, Apostoli P, et al. Loss of sight and sound. Could it be the hip? Lancet. 2009;373:1052. [55] Ikeda T, Takahashi K, Kabata T, Sakagoshi D, Tomita K, Yamada M. Polyneuropathy caused by cobalt–chromium metallosis after total hip replacement. Muscle Nerve. 2010;42:140–3. [56] Srinivasan A, Jung E, Levine BR. Modularity of the femoral component in total hip arthroplasty. J Am Acad Orthop Surg. 2012;20:214–22. [57] Lombardi Jr. AV, Mallory TH, Fada RA, Adams JB. Stem modularity: rarely necessary in primary total hip arthroplasty. Orthopedics. 2002;25:1385–7. [58] Barrack RL. Orthopaedic crossfire—stem modularity is unnecessary in revision total hip arthroplasty: in the affirmative. J Arthroplasty. 2003;18:98–100. [59] Sakai T, Sugano N, Ohzono K, Nishii T, Haraguchi K, Yoshikawa H. Femoral anteversion, femoral offset, and abductor lever arm after total hip arthroplasty using a modular femoral neck system. J Orthop Sci. 2002;7:62–7. [60] Traina F, De Fine M, Tassinari E, Sudanese A, Calderoni PP, Toni A. Modular neck prostheses in DDH patients: 11-year results. J Orthop Sci. 2011;16:14–20. [61] Lim SJ, Park YS, Moon YW, Jung SM, Ha HC, Seo JG. Modular cementless total hip arthroplasty for multiple epiphyseal dysplasia. J Arthroplasty. 2009;24:77–82. [62] Australian Orthopaedic Association. National Joint Replacement Registry. Annual Report. Adelaide: Australian Orthopaedic Association; 2011. [63] Weber AE, Skendzel JG, Waxman DL, Blaha JD. Symptomatic aseptic hydrogen pneumarthrosis as a sign of crevice corrosion following total hip arthroplasty with a modular neck: a case report. JBJS Case Connector. 2013;3:e76 1–6.
M I N A R S I N
A
R T H R O P L A S T Y
24 (2013) 71–75
Available online at www.sciencedirect.com
www.elsevier.com/locate/semanthroplasty
Femoral neck modularity: A bridge too far Alexander E. Weber, MDn, and John D. Blaha, MD Department of Orthopaedic Surgery, University of Michigan, 2912 Taubman Center, SPC 5328, 1500 E. Medical Center Dr, Ann Arbor, MI
AR T IC LE INFO
AB STR A C T Modular femoral neck use in total hip arthroplasty (THA) affords the operating surgeon
Keywords:
increased intra-operative flexibility with regard to offset, version, and leg length. Propo-
modular femoral neck
nents also advocate a reduced dislocation rate, reduced impingement issues, and ease of
total hip arthroplasty
revision of acetabular component, head, or neck. However, the increased intra-operative
implant design
flexibility and potential postoperative advantages come at a significant price. Adverse
implant complications
events and complications associated with modular femoral neck usage are being reported
implant failure
with increasing frequency. Modular femoral neck fractures as a result of patient- and
corrosion
implant-related factors are prevalent. Corrosion at the neck–stem interface is associated with a number of sequelae, including osteolysis, synovitis, adverse local tissue reactions (ALTRs), and aseptic lymphocyte-laminated vascular-associated lesions (ALVAL). Systemic complications of metallosis are also pertinent following corrosion at the neck–stem junction. Failure to disassemble the neck from the stem due to corrosion and cold welding is a documented complication and obviates a potential benefit of modularity at the time of revision. Modular femoral necks have a twofold increase in overall revision rate in the Australian registry data as compared to fixed-neck stems. Lastly, modular femoral necks add significant cost to each THA. The purpose of this review article is to discuss the current state of femoral neck modularity and provide the readership with pause prior to the continued use of modular femoral neck THA. Given the current and emerging literature, the modular femoral neck is a bridge too far. & 2013 Elsevier Inc. All rights reserved.
1.
Introduction
The increased use of modularity in total hip arthroplasty (THA) occurred in the late 1980s and early 1990s due to a series of studies describing the variability in leg length, version, and offset of the lower extremity and hip [1,2]. The described intra-operative advantages of modularity are the ability to independently adjust the aforementioned variables of leg length, offset, and version [3–7]. The theoretical postoperative advantages owing to intra-operative flexibility include decreased dislocation rates and decreased mechanical impingement [3–7]. In addition, authors have advocated that in an era of minimally invasive THA, neck modularity
affords the surgeon the ability to “build” the implants in situ through smaller incisions [8]. Proponents of the modular neck also discuss the ease of revision in cases of acetabular component, liner or head revision in the face of a well-fixed stem. Lastly, authors have noted the potential for decreased component inventory given the increased intra-operative flexibility [3]. Interestingly, it was not long after the first description of modularity that concerns began to arise [4,9–13]. Early designs of the modular taper lent themselves to fretting and crevice corrosion. Modifications to implant materials initially quelled concerns regarding the degradation process. These design modifications led to a period of relative neutrality regarding usage of
Dr. Blaha is a paid consultant for and receives royalties from Wright Medical Technology, Inc. n Address reprint requests to Alexander E. Weber, MD, Department of Orthopaedic Surgery, University of Michigan, 2912 Taubman Center, SPC 5328, 1500 E. Medical Center Dr., Ann Arbor, MI 48109. E-mail address: [email protected] (A.E. Weber). 1045-4527/$ - see front matter & 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.sart.2013.07.001
72
SEM
I N A R S I N
A
R T H R O P L A S T Y
the modular neck in THA [14]. However, clinical failures began to mount in the literature: unintentional dissociation of neck from stem, failures to disassemble neck from stem during revision surgery, modular neck fractures, corrosion, and the sequelae thereof [8,15–26]. These results led to renewed interest in the mechanisms of these clinical failures, the results of which are outlined below.
2.
Modular femoral neck fracture
The adverse clinical outcome of modular neck fracture is relatively rare; however, the frequency of case reports has increased [15,16,18,21,22,27]. One large case series exists in which 5000 titanium (Ti) modular neck THAs were evaluated and an incidence of adverse outcomes of 1.4% was reported [19]. Since then a multitude of case reports and case series has entered the literature [20,21,23,26,27]. Several patient, surgeon, and implant factors have been hypothesized to contribute to adverse outcomes. Contributing patient factors may include male gender and patient weight greater than 100 kg [15,19,21,22]. Surgeon factors are related to the technique of implantation, taking care to impact the neck into the stem as accurately as possible and ensuring that all debris (bone chips) and liquid (blood and irrigant) are removed from the stem prior to impacting the neck [19,28]. Jauch et al. [28], in a controlled biomechanical experiment, demonstrated that debriscontaminated modular necks had increased micromotion compared to clean interfaces and that Ti components had significantly higher micromotion than cobalt–chromium (CoCr) components under comparable conditions. They postulated that increased micromotion leads to fretting and fatigue failures [28]. The implant-related factors appear to be numerous [15,19,22,24]. All other factors being equal, Ti neck implants have been postulated to fail due to fracture more frequently than CoCr necks, given the lower modulus of elasticity for titanium [29]. The use of “long varus” necks and implants with neck-shaft angles greater than 1351 may increase the bending moment causing mechanical stress on the neck–stem junction. This increase in mechanical stress has been implicated as a cause of micromotion, corrosion, and neck fracture [15,19,22,24,30]. Skendzel et al. [15] reported on two cases of “long varus” modular neck fractures and cited a 32.7% increase in the bending moment as compared to the standard “short varus” neck. Although a much less frequent occurrence, fracture of a metaphyseal–diaphyseal modular femoral system may also occur. In a retrospective review of this type of implant, Lakstein et al. [31] reported on three implants with six mid-stem fractures. After a microscopic evaluation of the components, the authors postulated that fretting fatigue had caused the fractures and that increased patient weight and a lack of proximal bone stock were associated risk factors for fracture [31]. The importance of adequate bone stock was further emphasized in the presence of modular junctions by Chu and colleagues [32] through the use of a finite element model of the modular interface in the presence and absence of stable osseous support. Their results suggest that in the absence of adequate bone stock, the peak stress across modular interface was increased 45% [32].
3.
24 (2013) 71–75
Modular femoral neck corrosion
Corrosion has been examined at both the femoral head–neck junction and the femoral neck–stem junction [3,4,10,12,19,33– 35]. Both CoCr and Ti implants form a biocompatible passivation layer that confers some degree of corrosion resistance in its intact state [28,36]. The process of corrosion typically begins with micromotion at the neck–stem interface due to the higher loads experienced at this junction as compared to the neck–head junction [19,24,28,35,37]. Micromotion leads to the mechanical removal of the passivation layer on the surface of the components and creates a local environment ripe for the propagation of corrosion [38]. Both CoCr and Ti implants are then susceptible to fretting and crevice corrosion. In the case of Ti implants, the loss of the passivation layer allows for not only crevice corrosion but also hydrogen embrittlement, a process that significantly weakens the material [9,38]. The end results for both CoCr and Ti implants are an increased propensity to fatigue failure and fracture as discussed previously. Furthermore, the corrosion process is not without its effects on the biologic environment as well. The end-products of the corrosion lead to an increase in metal debris that may act locally within the bone and soft tissues as well as systemically at the end organs [9]. There are currently conflicting reports on the degree of corrosion, given the material coupling. Research of the head– neck junction has demonstrated that corrosion and fretting have been documented in mixed metal systems (CoCr neck with Ti stem) and in the presence of similar material couplings [24,26,33,35,38–40]. Some groups have advocated the use of CoCr rather than Ti due to lower micromotion and increased fatigue strength [19,28], whereas other studies have found contradictory results [41]. Kop et al. [41] examined 57 modular necks and found that 62% of the CoCr components and 30% of the Ti components exhibited signs of corrosion. Ninety percent of the CoCr and 50% of the Ti components exhibited signs of fretting [41]. The severity of corrosion and fretting was greater at the neck–stem interface as compared to the head–neck interface [41]. Ultimately, there is no definitive answer as to which metal combination is safest or whether there are significant advantages to using two dissimilar metals at an interface. Both CoCr and Ti modular necks have a high propensity for fretting and crevice corrosion and the treating surgeon must be prepared to share these results with those treated with a modular THA. Furthermore, the treating surgeon must warn patients that corrosion positively correlates with duration of implant retention [33,34].
4.
Failure to disassemble
An additional complication of Ti–Ti modular neck–stem interfaces is the failure to disassemble the neck from the stem at the time of revision. Fraitzl et al. [26] performed a retrieval study of 22 Ti modular neck devices and found that seven (32%) necks would not disengage from the stems. Kop et al. [41] found that of the 57 retrieved modular devices, failure to disassemble was noted in 22% of the Ti devices.
S
E M I N A R S I N
AR
T H R O P L A S T Y
In both studies corrosion and cold welding of the neck–stem interface was documented as the etiology for failure to disassemble. These results completely obviate one of the proposed benefits of femoral neck modularity, that of ease of head or neck revision in the presence of a well-fixed stem. Cold welding of the neck to stem and failure to disassemble may lead to the increased morbidity of extensile approaches, extended trochanteric osteotomy, and in some cases, return visits to the operating room. The treating surgeon should be aware of this potential complication and anticipate alternative surgical procedures.
5.
Local effects of modular neck corrosion
Much attention has been paid to metal-on-metal (MOM) articulations and the head–neck interface as potential sources of systemic increases in metal debris and adverse local tissue reactions (ALTRs) [42–46]. The neck–stem interface is not as well studied in this regard; however, given the increased mechanical stress, micromotion, and corrosion at the neck–stem interface as compared to the head–neck interface, it is appropriate to extrapolate from the head–neck body of literature [28,41]. If anything, given the higher mechanical forces dissipated through the neck–stem junction and the increased micromotion at this interface, the local and systemic effects of corrosion at the neck– stem junction should be multiplied as compared to lessons learned from the head–neck junction. Locally, head–neck taper corrosion has been associated with synovitis and osteolysis [9,33,40]. In addition to intra-articular synovitis and osteolysis, extra-articular ALTRs have been described in the modular neck literature [41,47–50]. Garbuz et al. [47], in the Charnley Award paper of 2010, found that CoCr modular neck implant patients had higher serum cobalt and chromium ion levels as compared to levels in patients who underwent hip resurfacing. Furthermore, the authors were able to attribute the higher metal ion levels to corrosion occurring at the neck–stem interface [47]. In the Kop et al. [41] retrieval study of 57 modular neck THAs, the authors noted that eight of the 57 patients had metallosis (seven CoCr devices and one Ti device) with two confirmed cases of aseptic lymphocyte-laminated vascular-associated lesions (ALVALs), both in CoCr devices. To our knowledge there are presently three case reports (five total patients) in the orthopedic literature of ALTRs associated with modular femoral necks [48–50]. All five patients underwent modular THA with a CoCr neck and a Ti stem and developed pain associated with metal artifact reduction sequence magnetic resonance imaging evidence of ALTR consistent with metal debris hypersensitivity and inflammatory reaction [48–50].
6.
Systemic effects of modular neck corrosion
There is currently a paucity of data regarding the systemic sequelae of neck–stem corrosion and metal debris. Similar to the local sequelae, there is no reason to believe that the systemic results of corrosion at the head–neck junction should not be extrapolated to the neck–stem junction. The corrosion products from the head–neck taper have been found to accumulate in end-stage organs [51]. Oldenburg et al. [52] linked corrosion to
24 (2013) 71–75
73
excess serum and urine levels of cobalt and implicated the increased ion levels in the development of thyroiditis, auditory disturbance, and granulomatous lesions. In the MOM articulation, cobalt corrosion debris has also been linked with neurologic and cardiac adverse outcomes [52–55]. Again, given that the corrosion end-products are equivalent between articulation and neck–stem interface, it is prudent for the surgeon to be aware of all the potential complications of modular neck usage.
7.
Healthcare-associated concerns
With the current trends in healthcare spending and reduction in reimbursements, all healthcare decisions should be examined carefully for their cost and effectiveness. Strictly from a cost perspective, a group of surgeons at a high-volume large academic institute estimated that using a modular stem may increase the cost of THA by 25% compared to a standard stem THA [56]. The increased cost of modular neck THA at a lowvolume hospital is likely even higher. From an effectiveness perspective, it is crucial to closely examine where the potential intra-operative benefits of femoral neck modularity outweigh the documented risks. To our knowledge, there are no Level I or II studies in which a cohort of modular neck THA patients outperformed a cohort of conventional THA patients in terms of dislocation rate, prosthetic impingement, need for revision, or subjective clinical outcomes. In the primary and standard revision THA settings, there is strong opposition to the use of the modular femoral neck [57,58]. Modular femoral necks have been advocated in cases of hip dysplasia or increased femoral anteversion [7,59–61]. However, the treating surgeon must be prepared to discuss all of the previously mentioned complications and adverse outcomes. In addition, there are now registry data that suggest the overall revision rate for modular femoral neck THA is double that of fixed-neck THA (8.9% vs. 4.2%) [5,62].
8.
Our institutional experience
We have recently reported on our institution's experience with modular neck complications [63]. In our series of patients with modular Ti–Ti neck–stem interfaces, we experienced one case of neck taper fracture, two cases of failure to disassemble, and multiple cases of corrosion. Interestingly, five of the six cases presented with acute onset of pain and radiographic evidence of pneumarthrosis. After infection was ruled out, an aspiration of the pneumarthrosis and subsequent mass spectrometry of the sample demonstrated an abnormally high concentration of hydrogen gas. Based on the high concentration of intraarticular hydrogen gas, physical evidence of corrosion at the time of revision, and the process of hydrogen embrittlement described previously [38], we concluded that the clinical scenario of acute onset of pain, radiographic evidence of pneumarthrosis and absence of infection in a patient who has undergone modular neck THA may be an early indicator of underlying crevice corrosion. The treating surgeon should be aware of this clinical constellation and that it may be an indicator of the impending additional complications of difficulty removing neck
74
SEM
I N A R S I N
A
R T H R O P L A S T Y
from stem, fracture of the implant, and/or the local and systemic sequelae of metallosis.
9.
Conclusion
Although femoral neck modularity affords the surgeon additional intra-operative options as compared to the standard fixedneck implants, the treating surgeon must consider if the intraoperative convenience outweighs the increased risk of femoral neck fracture, failure to disassemble, corrosion, metallosis, and an overall twofold increase in revision rate. On the basis of the current and emerging literature as well as our clinical experience we believe the modular neck is a bridge too far.
10.
Disclosure
The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.
r e f e r e n c e s
[1] Noble PC, Box GG, Kamaric E, Fink MJ, Alexander JW, Tullos HS. The effect of aging on the shape of the proximal femur. Clin Orthop Relat Res. 1995:31–44. [2] Noble PC, Alexander JW, Lindahl LJ, Yew DT, Granberry WM, Tullos HW. The anatomic basis of femoral component design. Clin Orthop Relat Res. 1988:148–65. [3] Collier JP, Mayor MB, Williams IR, Surprenant VA, Surprenant HP, Currier BH. The tradeoffs associated with modular hip prostheses. Clin Orthop Relat Res. 1995:91–101. [4] Cook SD, Barrack RL, Baffes GC, Clemow AJ, Serekian P, Dong N, et al. Wear and corrosion of modular interfaces in total hip replacements. Clin Orthop Relat Res. 1994:80–8. [5] Archibeck MJ, Cummins T, Carothers J, Junick DW, White Jr RE. A comparison of two implant systems in restoration of hip geometry in arthroplasty. Clin Orthop Relat Res. 2011;469:443–6. [6] Matsushita A, Nakashima Y, Fujii M, Sato T, Iwamoto Y. Modular necks improve the range of hip motion in cases with excessively anteverted or retroverted femurs in THA. Clin Orthop Relat Res. 2010;468:3342–7. [7] Sakai T, Ohzono K, Nishii T, Miki H, Takao M, Sugano N. A modular femoral neck and head system works well in cementless total hip replacement for patients with developmental dysplasia of the hip. J Bone Joint Surg Br. 2010;92:770–6. [8] Dunbar MJ. The proximal modular neck in THA: a bridge too far: affirms. Orthopedics. 2010;33:640. [9] Jacobs JJ, Urban RM, Gilbert JL, Skipor AK, Black J, Jasty M, et al. Local and distant products from modularity. Clin Orthop Relat Res. 1995:94–105. [10] Collier JP, Surprenant VA, Jensen RE, Mayor MB. Corrosion at the interface of cobalt-alloy heads on titanium-alloy stems. Clin Orthop Relat Res. 1991:305–12. [11] Collier JP, Mayor MB, Jensen RE, Surprenant VA, Surprenant HP, McNamar JL, et al. Mechanisms of failure of modular prostheses. Clin Orthop Relat Res. 1992:129–39. [12] Collier JP, Surprenant VA, Jensen RE, Mayor MB, Surprenant HP. Corrosion between the components of modular femoral hip prostheses. J Bone Joint Surg Br. 1992;74:511–7.
24 (2013) 71–75
[13] Mathiesen EB, Lindgren JU, Blomgren GG, Reinholt FP. Corrosion of modular hip prostheses. J Bone Joint Surg Br. 1991;73: 569–75. [14] Blaha JD. The modular neck: keystone to functional restoration. Orthopedics. 2006;29:804–5. [15] Skendzel JG, Blaha JD, Urquhart AG. Total hip arthroplasty modular neck failure. J Arthroplasty. 2011;26:338 [e331–e334]. [16] Atwood SA, Patten EW, Bozic KJ, Pruitt LA, Ries MD. Corrosion-induced fracture of a double-modular hip prosthesis: a case report. J Bone Joint Surg Am. 2010;92:1522–5. [17] Cooper HJ, Della Valle CJ, Berger RA, Tetreault M, Paprosky WG, Sporer SM, et al. Corrosion at the head–neck taper as a cause for adverse local tissue reactions after total hip arthroplasty. J Bone Joint Surg Am. 2012;94:1655–61. [18] Ellman MB, Levine BR. Fracture of the modular femoral neck component in total hip arthroplasty. J Arthroplasty. 2013;28:196 [e191–e195]. [19] Grupp TM, Weik T, Bloemer W, Knaebel HP. Modular titanium alloy neck adapter failures in hip replacement—failure mode analysis and influence of implant material. BMC Musculoskelet Disord. 2010;11:3. [20] Sporer SM, DellaValle C, Jacobs J, Wimmer M. A case of disassociation of a modular femoral neck trunion after total hip arthroplasty. J Arthroplasty. 2006;21:918–21. [21] Wilson DA, Dunbar MJ, Amirault JD, Farhat Z. Early failure of a modular femoral neck total hip arthroplasty component: a case report. J Bone Joint Surg Am. 2010;92:1514–7. [22] Wright G, Sporer S, Urban R, Jacobs J. Fracture of a modular femoral neck after total hip arthroplasty: a case report. J Bone Joint Surg Am. 2010;92:1518–21. [23] Gill IP, Webb J, Sloan K, Beaver RJ. Corrosion at the neck– stem junction as a cause of metal ion release and pseudotumour formation. J Bone Joint Surg Br. 2012;94:895–900. [24] Kop AM, Swarts E. Corrosion of a hip stem with a modular neck taper junction: a retrieval study of 16 cases. J Arthroplasty. 2009;24:1019–23. [25] Kretzer JP, Jakubowitz E, Krachler M, Thomsen M, Heisel C. Metal release and corrosion effects of modular neck total hip arthroplasty. Int Orthop. 2009;33:1531–6. [26] Fraitzl CR, Moya LE, Castellani L, Wright TM, Buly RL. Corrosion at the stem–sleeve interface of a modular titanium alloy femoral component as a reason for impaired disengagement. J Arthroplasty. 2011;26:113–9 [119–e111]. [27] Dangles CJ, Altstetter CJ. Failure of the modular neck in a total hip arthroplasty. J Arthroplasty. 2010;25:1169 [e1165–e1167]. [28] Jauch SY, Huber G, Hoenig E, Baxmann M, Grupp TM, Morlock MM. Influence of material coupling and assembly condition on the magnitude of micromotion at the stem-neck interface of a modular hip endoprosthesis. J Biomech. 2011;44:1747–51. [29] Bobyn JD, Mortimer ES, Glassman AH, Engh CA, Miller JE, Brooks CE. Producing and avoiding stress shielding. Laboratory and clinical observations of noncemented total hip arthroplasty. Clin Orthop Relat Res. 1992:79–96. [30] Wright Medical Technology: A Safety Alert. The use of modular necks in total hip replacement. Arlington, TN: Wright Medical Technology, Inc., 2008. [31] Lakstein D, Eliaz N, Levi O, Backstein D, Kosashvili Y, Safir O, et al. Fracture of cementless femoral stems at the mid-stem junction in modular revision hip arthroplasty systems. J Bone Joint Surg Am. 2011;93:57–65. [32] Chu Y, Elias JJ, Duda GN, Frassica FJ, Chao EY. Stress and micromotion in the taper lock joint of a modular segmental bone replacement prosthesis. J Biomech. 2000;33:1175–9. [33] Goldberg JR, Gilbert JL, Jacobs JJ, Bauer TW, Paprosky W, Leurgans S. A multicenter retrieval study of the taper interfaces of modular hip prostheses. Clin Orthop Relat Res. 2002:149–61.
S
E M I N A R S I N
AR
T H R O P L A S T Y
[34] Salvati EA, Lieberman JR, Huk OL, Evans BG. Complications of femoral and acetabular modularity. Clin Orthop Relat Res. 1995:85–93. [35] Gilbert JL, Buckley CA, Jacobs JJ. In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling. J Biomed Mater Res. 1993;27:1533–44. [36] Swaminathan V, Gilbert JL. Fretting corrosion of CoCrMo and Ti6Al4V interfaces. Biomaterials. 2012;33:5487–503. [37] Brown SA, Hughes PJ, Merritt K. In vitro studies of fretting corrosion of orthopaedic materials. J Orthop Res. 1988;6:572–9. [38] Rodrigues DC, Urban RM, Jacobs JJ, Gilbert JL. In vivo severe corrosion and hydrogen embrittlement of retrieved modular body titanium alloy hip-implants. J Biomed Mater Res B Appl Biomater. 2009;88:206–19. [39] Goldberg JR, Gilbert JL. In vitro corrosion testing of modular hip tapers. J Biomed Mater Res B Appl Biomater. 2003;64:78–93. [40] Brown SA, Flemming CA, Kawalec JS, Placko HE, Vassaux C, Merritt K, et al. Fretting corrosion accelerates crevice corrosion of modular hip tapers. J Appl Biomater. 1995;6:19–26. [41] Kop AM, Keogh C, Swarts E. Proximal component modularity in THA—at what cost? An implant retrieval study. Clin Orthop Relat Res. 2012;470:1885–94. [42] Biant LC, Bruce WJ, van der Wall H, Walsh WR. Infection or allergy in the painful metal-on-metal total hip arthroplasty? J Arthroplasty. 2010;25:334 [e311–e336]. [43] Mikhael MM, Hanssen AD, Sierra RJ. Failure of metal-onmetal total hip arthroplasty mimicking hip infection. A report of two cases. J Bone Joint Surg Am. 2009;91:443–6. [44] Watters TS, Eward WC, Hallows RK, Dodd LG, Wellman SS, Bolognesi MP. Pseudotumor with superimposed periprosthetic infection following metal-on-metal total hip arthroplasty: a case report. J Bone Joint Surg Am. 2010;92:1666–9. [45] Kwon YM, Thomas P, Summer B, Pandit H, Taylor A, Beard D, et al. Lymphocyte proliferation responses in patients with pseudotumors following metal-on-metal hip resurfacing arthroplasty. J Orthop Res. 2010;28:444–50. [46] Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons CL, et al. Pseudotumours associated with metalon-metal hip resurfacings. J Bone Joint Surg Br. 2008;90: 847–51. [47] Garbuz DS, Tanzer M, Greidanus NV, Masri BA, Duncan CP. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res. 2010;468:318–25. [48] Hsu AR, Gross CE, Levine BR. Pseudotumor from modular neck corrosion after ceramic-on-polyethylene total hip arthroplasty. Am J Orthop (Belle Mead, NJ). 2012;41:422–6.
24 (2013) 71–75
75
[49] Patel AR, Patel RM, Thomas D, Bauer TW, Stulberg SD. Caveat emptor: adverse inflammatory soft-tissue reactions in total hip arthroplasty with modular femoral neck implants: a report of two cases. JBJS Case Connector. 2012;2:e80. [50] Werner SD, Bono JV, Nandi S, Ward DM, Talmo CT. Adverse tissue reactions in modular exchangeable neck implants: a report of two cases. J Arthroplasty. 2013;28:543 [e513–e545]. [51] Urban RM, Jacobs JJ, Tomlinson MJ, Gavrilovic J, Black K, Peoch M. Dissemination of wear particles to the liver, spleen, and abdominal lymph nodes of patients with hip or knee replacement. J Bone Joint Surg Am. 2000;82:457–76. [52] Oldenburg M, Wegner R, Baur X. Severe cobalt intoxication due to prosthesis wear in repeated total hip arthroplasty. J Arthroplasty. 2009;24(825):e815–20. [53] Tower S. Arthroprosthetic cobaltism: identification of the atrisk patient. Alaska Med. 2010;52:28–32. [54] Rizzetti MC, Liberini P, Zarattini G, Catalani S, Pazzaglia U, Apostoli P, et al. Loss of sight and sound. Could it be the hip? Lancet. 2009;373:1052. [55] Ikeda T, Takahashi K, Kabata T, Sakagoshi D, Tomita K, Yamada M. Polyneuropathy caused by cobalt–chromium metallosis after total hip replacement. Muscle Nerve. 2010;42:140–3. [56] Srinivasan A, Jung E, Levine BR. Modularity of the femoral component in total hip arthroplasty. J Am Acad Orthop Surg. 2012;20:214–22. [57] Lombardi Jr. AV, Mallory TH, Fada RA, Adams JB. Stem modularity: rarely necessary in primary total hip arthroplasty. Orthopedics. 2002;25:1385–7. [58] Barrack RL. Orthopaedic crossfire—stem modularity is unnecessary in revision total hip arthroplasty: in the affirmative. J Arthroplasty. 2003;18:98–100. [59] Sakai T, Sugano N, Ohzono K, Nishii T, Haraguchi K, Yoshikawa H. Femoral anteversion, femoral offset, and abductor lever arm after total hip arthroplasty using a modular femoral neck system. J Orthop Sci. 2002;7:62–7. [60] Traina F, De Fine M, Tassinari E, Sudanese A, Calderoni PP, Toni A. Modular neck prostheses in DDH patients: 11-year results. J Orthop Sci. 2011;16:14–20. [61] Lim SJ, Park YS, Moon YW, Jung SM, Ha HC, Seo JG. Modular cementless total hip arthroplasty for multiple epiphyseal dysplasia. J Arthroplasty. 2009;24:77–82. [62] Australian Orthopaedic Association. National Joint Replacement Registry. Annual Report. Adelaide: Australian Orthopaedic Association; 2011. [63] Weber AE, Skendzel JG, Waxman DL, Blaha JD. Symptomatic aseptic hydrogen pneumarthrosis as a sign of crevice corrosion following total hip arthroplasty with a modular neck: a case report. JBJS Case Connector. 2013;3:e76 1–6.