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The Management of the Symptomatic Patient With a Metal-on-Metal Hip Prosthesis
Canadian Association of Radiologists Journal 67 (2016) 76e81 www.carjonline.org
Musculoskeletal Radiology / Radiologies musculo-squelettique
The Management of the Symptomatic Patient With a Metal-on-Metal Hip Prosthesis Kate Harrington, MB, BCh, BAO, MRCPI*, Emma Phelan, MB, BCh, NUI, MRCPI, William C. Torreggiani, MB, MRCPI, FRCR, FFRRCSI, Orla Doody, MB, MRCPI, FFRRCSI Radiology Department, The Adelaide and Meath Hospital Dublin, Incorporating the National Children’s Hospital, Dublin, Ireland
Abstract Metal-on-metal (MoM) hip implants have gained popularity due to their greater stability and reduction in implant failure compare to metal-on-polyethylene prostheses. However, as well as carrying general risks of hip implantation, risks specifically associated with MoM implants have been well documented in recent years. Conditions such as pseudotumours or aseptic lymphocyte-dominated vasculitisassociated lesions are specific to MoM hip implants. In this review we discuss the typical patient presentation, the investigations that should be performed, the typical findings on various imaging modalities, and the treatment options of symptomatic patients with MoM hip arthroplasties. Resume Les protheses de hanche a couple de frottement metal-metal gagnent en popularite en raison de leur stabilite accrue et d’un nombre reduit d’echecs comparativement aux protheses a couple de frottement metal-polyethylene. Toutefois, en plus des risques generalement associes aux arthroplasties, les protheses a couple de frottement metal-metal presentent des risques particuliers qui ont fait l’objet d’une vaste documentation au cours des dernieres annees. En effet, certaines affections, notamment les pseudotumeurs ou les lesions associees a des angeites aseptiques a predominance lymphocytaire, sont etroitement associees aux protheses de hanche a couple de frottement metal-metal. La presente etude aborde les signes et les sympt^omes des patients, les examens a realiser, les constatations propres aux diverses modalites d’imagerie et les options therapeutiques qui s’offrent aux patients symptomatiques ayant rec¸u une prothese a couple de frottement metalmetal dans le cadre d’une arthroplastie de la hanche. Ó 2016 Canadian Association of Radiologists. All rights reserved. Key Words: Aseptic lymphocytic vasculitis-associated lesion; Metal-on-metal hip arthroplasty; Pseudotumour
Metal-on-metal (MoM) hip implants enjoyed a resurgence in use in the late 1990s and early 2000s due to concerns over metal-on-polyethylene wear-induced osteolysis, loosening, and failure, particularly in younger patients. The concurrent advances in technology and implant systems such as hip resurfacing systems and large-diameter femoral head components promised bone conservation, greater stability, and a reduction in implant failure in MoM prostheses. Two main types of MoM implants exist, namely the traditional MoM total hip replacement, which consists of a metal ball and stem (femoral component) and metal cup (acetabular * Address for correspondence: Kate Harrington, MB, BCh, BAO, MRCPI, Radiology Department, The Adelaide and Meath Hospital Dublin, Incorporating the National Children’s Hospital, Dublin 24, Ireland. E-mail address: [email protected] (K. Harrington).
component), and the MoM resurfacing hip system, which consists of most of the native femoral head with a metal cap articulating with a thin metal acetabular cup. As well as carrying general risks of hip implantation, a risk specifically associated with MoM implants in the form of a reactive periprosthetic soft tissue lesion has been documented in the literature in recent years. These periprosthetic lesions are known by a variety of terms, most commonly described as masses, cystic tumours, aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) [1], pseudotumours [2], or adverse reactions to metal debris [3]. Although these terms are sometimes used interchangeably not all periprosthetic pseudotumours demonstrate an ALVAL type response. The term ALVAL was first used in 2005 and relates to the histological findings of the periprosthetic reactive masses of necrotic tissue and dense perivascular lymphocyte
0846-5371/$ - see front matter Ó 2016 Canadian Association of Radiologists. All rights reserved. http://dx.doi.org/10.1016/j.carj.2015.10.006
Symptomatic metal-on-metal hip prosthesis / Canadian Association of Radiologists Journal 67 (2016) 76e81
infiltrates. The pathogenesis of such reaction remains unclear but a popular hypothesis is that metal ions are shed from the prosthesis and elicit a type IV hypersensitivity reaction [4]. Necrosis and macrophage infiltration, however, is a shared histological feature on all sampled periprosthetic masses, in keeping with a metal-induced cytotoxic effect [5]. In this article pseudotumour will be used to describe the abnormal periprosthetic masses. In 2012 regulatory authorities in the United Kingdom, Canada, the United States, and Australia issued alerts and safety communications related to MoM implants and guidance on the management of such patients [6e9]. A discussion on the management of a symptomatic patient is presented with recommended investigations, optimization of imaging modalities, expected radiological findings, and further treatment options. Presentation The incidence of pseudotumour varies widely in recently reported studies from 25%-68% [10e13]. This is in contrast to a meta-analysis, which calculated the pooled incidence estimate of pseudotumours to be much lower at 0.6% [14]. However, this is likely due to the inclusion of early studies, with more recent studies quoting much higher incidences especially when using more sensitive imaging techniques such as metal artifact reduction sequences magnetic resonance imaging (MRI), imaging a high risk patient cohort and following patients over a longer time period. Notably a recent study by Bosker et al [15] demonstrated a significant increase in incidence of pseudotumours after prolonged follow-up. The meta-analysis also found that 3.9% required hip revisions. However, when the studied patient population is separated by gender it is apparent that females have a significantly greater incidence of pseudotumours and of requiring hip revision due to pseudotumours compared to men with incidences as high as 9.4% and 6.2%, respectively. Other risk factors identified for the development of pseudotumours include resurfacing systems with small femoral heads, total hip replacements with large diameter femoral heads, bilateral implants, type of implant used, and suboptimal alignment of the implant [16,17]. Symptoms are nonspecific and pain is the most common presentation. A palpable mass may be appreciated on examination. In severe cases there may be evidence of femoral neuropathy. The time to presentation may vary with patients presenting from a few months to a number of years after surgery [18]. Investigations Serum Samples Patients with MoM implants are at an increased risk of having increased serum levels of chromium and cobalt than their metal-on-polyethylene counterparts [19]. The significance of raised serum metal ion levels is still debatable and it
77
is mostly used as a surrogate marker to detect wear in MoM prostheses as there have been proven associations with high levels or increasing levels of metal ions and implant failure [20]. There are, however, documented cases of failure due to pseudotumour without significantly raised serum metal ions. Many regulatory authorities now recommend monitoring of serum metal ion levels in all symptomatic patients with MoM with the Australian Government Therapeutic Goods also recommending monitoring of serum metal ion levels in asymptomatic patients [6e9]. Metal ion levels, however, should not be used in isolation when screening for MoM pseudotumours. Skin patch testing is useful in type IV hypersensitivity reactions. Although the underlying pathogenesis of pseudotumours remains unclear, a type IV hypersensitivity reaction is a popular hypothesis. Studies have shown a greater frequency of metal allergies in patients with MoM implants, including those with failed implants, however, skin patch testing for metal allergy is not recommended at present for the workup of symptomatic or failed MoM implants [21]. Radiography Radiography is the primary imaging modality for the follow-up of patients post THR. Findings such as periprosthetic loosening, medial calcar resorption, or femoral neck resorption can be seen in complicated cases (Figure 1). However, although these findings are not specific or sensitive for the presence of pseudotumours, in patients with a MoM prosthesis and radiographic abnormalities, pseudotumour should be considered. Furthermore, many patients with pseudotumours will have normal findings on plain radiograph [22]. MRI MRI is the most useful investigation in the assessment of the postoperative MoM prosthesis of the surrounding soft tissues. While traditionally the presence of metal prostheses would preclude accurate evaluation of the adjacent soft tissues due to the presence of metal-induced susceptibility artifact, recent advances in the imaging of metal prostheses with the use of metal artifact reduction sequences now allows evaluation and diagnosis of periprosthetic soft tissue abnormalities. Parameters employed include increasing the receiver bandwidth or increasing the field of view with the vast majority of susceptibility reduction achieved by increasing the receiver bandwidth alone [23]. Fast spin echo sequences allows reduction of dephasing time and thus the amount of susceptibility artifact seen. A short echo time also reduces the time available for dephasing and is generally recommended, although there are reports into the usefulness of long echo time T2-weighted sequences that pick up blooming artifact from soft tissue metallic deposits [24]. Inversion recovery techniques are preferred to fat suppression. Finally, switching direction of phase- and frequency-encoding between acquisitions allows for greater visualization of the soft tissues due to differing susceptibility artifact in each direction.
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K. Harrington et al. / Canadian Association of Radiologists Journal 67 (2016) 76e81
Figure 1. Initial (A) and subsequent (B) follow up radiograph demonstrated new lucency (circle) at the medial aspect of the femoral component of the right prosthesis.
Periprosthetic pseudotumours typically do not enhance following the administration of intravenous contrast and the use of contrast is mostly useful in its exclusion of other possible soft tissue collections [24]. While MRI is most likely to pick up a soft tissue abnormality associated with MoM athroplasties, both the imaging findings and locations of pseudotumours can vary widely making the diagnosis of MoM pseduotumours on imaging alone difficult. As well as this, the presence of periprosthetic masses on the imaging of asymptomatic functioning hips has been noted by Hart et al [10] who went on to show no difference in the prevalence of a periprosthetic mass in symptomatic patients versus asymptomatic matched controls. More recent studies have attempted to classify pseudotumours based on imaging findings and to correlate these findings with histology and outcome. First, any periprosthetic mass identified must be in communication with the hip joint before it can be considered as a MoM pseudotumour. A recent review paper classifies the masses according to MRI signal characteristics, with thin-walled cysts as Type I, thick-walled cysts as Type II, and predominantly solid masses as Type III. It was noted that cystic lesions were more likely to be located posteriorly and predominantly solid lesions anteriorly. In particular, a ‘‘characteristic’’ signal intensity was noted when the cystic wall or solid component of the periprosthetic mass demonstrated a lower signal intensity relative to muscle, which was presumed to represent metallic components (Figures 2-4) [2]. An alternative classification grades the severity of pseudotumour as mild, moderate, or severe depending on size and extension from
the periprosthetic tissues into the intramuscular compartments or evidence of bone involvement [25]. The more solid the lesion is the more likely it is to cause symptoms, have histological findings of pseudotumour, and have associated complications of local tissue or bony destruction [2,26]. Ultrasound Ultrasound is a cheap and readily available test that is less affected by the presence of an adjacent metal prosthesis. A recent study has shown the benefit of ultrasound as a screening tool for the detection of pseudotumours [27] and many regulatory authorities have recommended that the initial screening test may be an ultrasound or a metal artifact reduction sequences MRI [6e9]. Ultrasound findings usually consist of a periprosthetic fluid collection or soft tissue mass (Figure 5). One of the main limitations of ultrasound is that it is user dependent. As well as screening for the presence of a pseudotumour, ultrasound can be used to obtain tissue samples from the visualized periprosthetic masses. A prospective cohort study by Bosker et al [13] sampled a proportion of identified pseudotumours using 16-gauge needles. While the samples obtained confirmed the presence of lymphocytes and metal debris, the sample sizes were found to be insufficient to reliably calculate a pseudotumour score. Definitive histological diagnosis therefore was mostly obtained at the time of the revision surgery. Ultrasound-guided biopsy in the work-up of a patient with a painful MoM arthroplasty prior to definite surgical revision therefore is infrequently undertaken and not
Symptomatic metal-on-metal hip prosthesis / Canadian Association of Radiologists Journal 67 (2016) 76e81
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Figure 2. Coronal and axial T1 weighted (A, B) and STIR weighted (C, D) images demonstrate large joint effusions extending into the iliopsoas bursae bilaterally and extending into the trochanteric bursa. These collections communicate with the hip joints bilaterally (asterisk) and demonstrate multiple foci of internal debris (arrows). The periprosthetic collections have a marked low signal rim (dashed arrows) and an irregular capsule.
explicitly recommended in various published guidelines. A recent article describing to a multidisciplinary approach to managing patients with symptomatic MoM pseudotumours did not include histological confirmation as part of the specialized investigations prior to undertaking hip revision. Symptomatic hips were only aspirated when infection needed to be excluded [28]. Treatment of a Pseudotumour Symptomatic Patient Once a pseudotumour is suspected the decision to perform a hip revision may be taken in conjunction with patient symptoms, patient metal ion serum levels, and orthopaedic opinion. In some instances a second orthopaedic opinion is recommended prior to embarking on surgical revision [7]. Intraoperative findings range from a smooth-walled fluid collection, which is in continuity with the joint to thickened
synovium or pseudocapsule formation to necrotic soft tissue masses. Inflammation and destruction of local tissues may also be seen with associated complications such as tendon avulsion or bony osteonecrosis [23,29]. Female patients have an eightfold greater risk of requiring hip arthroplasty revision than men. However, the outcome of hip revision with conventional polyethylene or other ceramic materials is variable, with patients often reporting little change to their initial presenting symptoms possibly because of the severity of the pseudotumour at the time of hip revision [17,30]. The preoperative imaging findings of the pseudotumour can persist, thus making MR interpretation of revised hip arthroplasties difficult [23]. Asymptomatic Patient In a study by Hauptfleisch et al [2] they noted that pseudotumours were incidentally seen in a number of their recruited ‘‘asymptomatic controls.’’ However, they felt that
Figure 3. Axial and coronal T2-weighted fast spin echo (A, B), coronal T1-weighted images (C) demonstrate a large left iliopsoas bursa (arrows) communicating with the anterior hip joint with multiple foci of low signal and debris. A similar but smaller right iliopsoas bursa is also present with foci of low signal and internal debris (dashed arrow).
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K. Harrington et al. / Canadian Association of Radiologists Journal 67 (2016) 76e81
Figure 4. Coronal T2-weighted fast spin-echo (A) and coronal T1-weighted images (B) demonstrate bilateral joint effusions, larger on the left, which demonstrate multiple foci of internal debris. The effusions have a marked low signal rim and an irregular capsule.
this cohort did actually have some mild symptoms as well as suboptimal functional scores once further evaluated. However, in a different study by Hart et al [10] they demonstrated no difference in the prevalence of a periprosthetic mass in symptomatic patients versus asymptomatic matched controls. What was noted however was that the pseudotumour was larger in size in the symptomatic patient. Similarly, in a recent retrospective study by Sutphen et al [12] they found a high prevalence of pseduotumours in asymptomatic patients, although there was a higher incidence of pseudotumours in the symptomatic cohort. Interestingly they did not find a significant difference in serum metal ion level and pseudotumour formation, in contrast to earlier studies [13,31], and thus further questioning the reliability of serum metal ion levels as a suitable screening test. The uncertainty of the management of a patient with a MoM implant is most notable in the asymptomatic patient and this is echoed in the contrasting recommendations of patient management across many national health-governing bodies. Health Canada recommends that the asymptomatic patients should be followed annually with a functional assessment and examination for 5 years postoperatively and thereafter as per local protocol. There is no specific recommendation for testing of metal ion levels or soft tissue imaging of the asymptomatic patient [7]. Similarly, the U.S. Food and Drug Administration recommends clinical examination and functional assessment at routine follow-up. Additional testing in the form of metal ion levels and soft
tissue imaging is not currently recommended in the absence of symptoms or reduction in implant functionality [8]. The UK Medical and Healthcare products Regulatory Agency however do recommend screening of the asymptomatic patients with high-risk arthroplasties for high metal ion levels as well as clinical assessment. Screening in the form of soft tissue imaging using ultrasound or MRI is not recommended unless the patient becomes symptomatic or demonstrates rising metal ion levels. They also recommend annual patient follow-up for the life of the implant in the highest risk implants (DePuy implants and all large-diameter femoral head stemmed systems) [6]. The Australian Government Therapeutic Drugs Administration recommend annual follow up for the life of the implant in high risk implants as well as serial blood metal ion levels and imaging in the form of radiographs plus ultrasound or MRI. They also suggest considering hip revision in this cohort of patients if there is evidence rising metal ion levels or significant imaging pseudotumour [9]. Notably there are no specific recommendations among these bodies regarding the need for obtaining biopsies and histological diagnosis from the periprosthetic mass in either the symptomatic or asymptomatic patient. Conclusion Pseudotumours or ALVAL are an increasingly recognized and reported complication of a MoM hip arthroplasty. The
Figure 5. Ultrasound images demonstrating a thick walled, cystic lesion in close proximity to the right hip joint. Internal iso- and hyperechoic debris is demonstrated lying within the lesion. It is often difficult to determine if this lesion is in continuity with the hip joint on ultrasound and cross-sectional imaging is usually then undertaken to further characterise the abnormality.
Symptomatic metal-on-metal hip prosthesis / Canadian Association of Radiologists Journal 67 (2016) 76e81
typical patient will be female, with a small femoral head component, and suboptimal implant alignment. Most patients will present with symptoms of pain. Initial investigations include serum metal ion levels and either ultrasound or MRI, and these initial investigations are also recommended in asymptomatic patients as part of their postoperative surveillance by many regulatory authorities. Plain radiographs may also be of benefit, but a negative radiograph does not exclude an underlying pseudotumour. The imaging appearances and position of the lesions on MRI vary making the diagnosis difficult; however. MRI optimization and increased radiologist awareness of the expected findings of pseudotumour assists in the diagnosis of these complex cases. References [1] Willert HG, Buchhorn GH, Fayyazi A, et al. Metal-on-metal bearings and hypersensitivity in patients with artificial hip joints. A clinical and histomorphological study. J Bone Joint Surg Am 2005;87:28e36. [2] Hauptfleisch J, Pandit H, Grammatopoulos G, et al. A MRI classification of periprosthetic soft tissue masses (pseudotumours) associated with metal-on-metal resurfacing hip arthroplasty. Skeletal Radiol 2012; 41:149e55. [3] Langton DJ, Jameson SS, Joyce TJ, et al. Early failure of metal-on-metal bearings in hip resurfacing and large-diameter total hip replacement: a consequence of excess wear. J Bone Joint Surg Br 2010;92:38e46. [4] Granchi D, Cenni E, Tigani D, et al. Sensitivity to implant materials in patients with total knee arthroplasties. Biomaterials 2008; 29:1494e500. [5] Kwon YM, Ostlere SJ, McLardy-Smith P, et al. ‘‘Asymptomatic’’ pseudotumors after metal-on-metal hip resurfacing arthroplasty: prevalence and metal ion study. J Arthroplasty 2011;26:511e8. [6] Medication and Healthcare Products Regulatory Agency. Metal-onMetal (MoM) Hip Replacements. 2012. Available at: http://www.mhra. gov.uk/home/groups/dts-bs/documents/medicaldevicealert/con155767. pdf. Accessed September 14, 2014. [7] Health Canada. Metal-on-Metal Hip Implants - Information for Orthopaedic Surgeons Regarding Patient Management Following Surgery - For Health Professionals. 2012. Available at: http://www. healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2012/15835a-eng. php. Accessed September 14, 2014. [8] U.S Food and Drug Administration. Concerns about Metal-on-Metal Hip Implants. 2015. Available at: http://www.fda.gov/MedicalDevices/ ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetal HipImplants/ucm241604.htm. Accessed April 22, 2015. [9] Australian Government Therapeutic Goods Administration. Metal-onMetal Hip Replacement Implants. 2014. Available at: http://www.tga. gov.au/hp/information-devices-mom-hip-implants.htm#.VBW-xZRdWSo. Accessed September 14, 2014. [10] Hart AJ, Satchithananda K, Liddle AD, et al. Pseudotumors in association with well-functioning metal-on-metal hip prostheses: a casecontrol study using three-dimensional computed tomography and magnetic resonance imaging. J Bone Joint Surg Am 2012;94:317e25. [11] Williams DH, Greidanus NV, Masri BA, et al. Prevalence of pseudotumor in asymptomatic patients after metal-on-metal hip arthroplasty. J Bone Joint Surg Am 2011;93:2164e71. [12] Sutphen SA, MacLaughlin LH, Madsen AA, et al. Prevalence of pseudotumor in patients after metal-on-metal hip arthroplasty evaluated with metal ion analysis and MARS-MRI. J Arthroplast 2016;31:260e3.
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[13] Bosker BH, Ettema HB, Boomsma MF, et al. High incidence of pseudotumour formation after large-diameter metal-on-metal total hip replacement: a prospective cohort study. J Bone Joint Surg Br 2012; 94:755e61. [14] Wiley KF, Ding K, Stoner JA, et al. Incidence of pseudotumor and acute lymphocytic vasculitis associated lesion (ALVAL) reactions in metal-on-metal hip articulations: a meta-analysis. J Arthroplasty 2013; 28:1238e45. [15] Bosker BH, Ettema HB, van Rossum M, et al. Pseudotumor formation and serum ions after large head metal-on-metal stemmed total hip replacement. Risk factors, time course and revisions in 706 hips. Arch Orthop Trauma Surg 2015;135:417e25. [16] Murray DW, Grammatopoulos G, Pandit H, et al. The ten-year survival of the Birmingham hip resurfacing: an independent series. J Bone Joint Surg Br 2012;94:1180e6. [17] Glyn-Jones S, Pandit H, Kwon YM, et al. Risk factors for inflammatory pseudotumour formation following hip resurfacing. J Bone Joint Surg Br 2009;91:1566e74. [18] Donell ST, Darrah C, Nolan JF, et al. Early failure of the Ultima metalon-metal total hip replacement in the presence of normal plain radiographs. J Bone Joint Surg Br 2010;92:1501e8. [19] Engh CA, MacDonald SJ, Sritulanondha S, et al. Metal ion levels after metal-on-metal total hip arthroplasty: a five-year, prospective randomized trial. J Bone Joint Surg Am 2014;96:448e55. [20] Hart AJ, Sabah SA, Sampson B, et al. Surveillance of patients with metal-on-metal hip resurfacing and total hip prostheses: a prospective cohort study to investigate the relationship between blood metal ion levels and implant failure. J Bone Joint Surg Am 2014;96:1091e9. [21] Thomas P, Braathen LR, Dorig M, et al. Increased metal allergy in patients with failed metal-on-metal hip arthroplasty and peri-implant Tlymphocytic inflammation. Allergy 2009;64:1157e65. [22] Toms AP, Marshall TJ, Cahir J, et al. MRI of early symptomatic metalon-metal total hip arthroplasty: a retrospective review of radiological findings in 20 hips. Clin Radiol 2008;63:49e58. [23] Toms AP, Smith-Bateman C, Malcolm PN, Cahir J, Graves M. Optimization of metal artefact reduction (MAR) sequences for MRI of total hip prostheses. Clin Radiol 2010;65:447e52. [24] Yanny S, Cahir JG, Barker T, et al. MRI of aseptic lymphocytic vasculitis-associated lesions in metal-on-metal hip replacements. AJR Am J Roentgenol 2012;198:1394e402. [25] Anderson H, Toms AP, Cahir JG, et al. Grading the severity of soft tissue changes associated with metal-on-metal hip replacements: reliability of an MR grading system. Skeletal Radiol 2011;40:303e7. [26] Nawabi DH, Gold S, Lyman S, et al. MRI predicts ALVAL and tissue damage in metal-on-metal hip arthroplasty. Clinical orthopaedics and related research 2014;472:471e81. [27] Muraoka K, Naito M, Nakamura Y, et al. Usefulness of ultrasonography for detection of pseudotumors after metal-on-metal total hip arthroplasty. J Arthroplasty 2015;30:879e84. [28] Berber R, Pappas Y, Khoo M, et al. A new approach to managing patients with problematic metal hip implants: the use of an Internetenhanced multidisciplinary team meeting: AAOS exhibit selection. J Bone Joint Surg Am 2015;97:e20. [29] Watters TS, Cardona DM, Menon KS, et al. Aseptic lymphocytedominated vasculitis-associated lesion: a clinicopathologic review of an underrecognized cause of prosthetic failure. Am J Clin Pathol 2010; 134:886e93. [30] Grammatopoulos G, Pandit H, Kwon YM, et al. Hip resurfacings revised for inflammatory pseudotumour have a poor outcome. J Bone Joint Surg Br 2009;91:1019e24. [31] Hart AJ, Sabah S, Henckel J, et al. The painful metal-on-metal hip resurfacing. J Bone Joint Surg Br 2009;91:738e44.
Musculoskeletal Radiology / Radiologies musculo-squelettique
The Management of the Symptomatic Patient With a Metal-on-Metal Hip Prosthesis Kate Harrington, MB, BCh, BAO, MRCPI*, Emma Phelan, MB, BCh, NUI, MRCPI, William C. Torreggiani, MB, MRCPI, FRCR, FFRRCSI, Orla Doody, MB, MRCPI, FFRRCSI Radiology Department, The Adelaide and Meath Hospital Dublin, Incorporating the National Children’s Hospital, Dublin, Ireland
Abstract Metal-on-metal (MoM) hip implants have gained popularity due to their greater stability and reduction in implant failure compare to metal-on-polyethylene prostheses. However, as well as carrying general risks of hip implantation, risks specifically associated with MoM implants have been well documented in recent years. Conditions such as pseudotumours or aseptic lymphocyte-dominated vasculitisassociated lesions are specific to MoM hip implants. In this review we discuss the typical patient presentation, the investigations that should be performed, the typical findings on various imaging modalities, and the treatment options of symptomatic patients with MoM hip arthroplasties. Resume Les protheses de hanche a couple de frottement metal-metal gagnent en popularite en raison de leur stabilite accrue et d’un nombre reduit d’echecs comparativement aux protheses a couple de frottement metal-polyethylene. Toutefois, en plus des risques generalement associes aux arthroplasties, les protheses a couple de frottement metal-metal presentent des risques particuliers qui ont fait l’objet d’une vaste documentation au cours des dernieres annees. En effet, certaines affections, notamment les pseudotumeurs ou les lesions associees a des angeites aseptiques a predominance lymphocytaire, sont etroitement associees aux protheses de hanche a couple de frottement metal-metal. La presente etude aborde les signes et les sympt^omes des patients, les examens a realiser, les constatations propres aux diverses modalites d’imagerie et les options therapeutiques qui s’offrent aux patients symptomatiques ayant rec¸u une prothese a couple de frottement metalmetal dans le cadre d’une arthroplastie de la hanche. Ó 2016 Canadian Association of Radiologists. All rights reserved. Key Words: Aseptic lymphocytic vasculitis-associated lesion; Metal-on-metal hip arthroplasty; Pseudotumour
Metal-on-metal (MoM) hip implants enjoyed a resurgence in use in the late 1990s and early 2000s due to concerns over metal-on-polyethylene wear-induced osteolysis, loosening, and failure, particularly in younger patients. The concurrent advances in technology and implant systems such as hip resurfacing systems and large-diameter femoral head components promised bone conservation, greater stability, and a reduction in implant failure in MoM prostheses. Two main types of MoM implants exist, namely the traditional MoM total hip replacement, which consists of a metal ball and stem (femoral component) and metal cup (acetabular * Address for correspondence: Kate Harrington, MB, BCh, BAO, MRCPI, Radiology Department, The Adelaide and Meath Hospital Dublin, Incorporating the National Children’s Hospital, Dublin 24, Ireland. E-mail address: [email protected] (K. Harrington).
component), and the MoM resurfacing hip system, which consists of most of the native femoral head with a metal cap articulating with a thin metal acetabular cup. As well as carrying general risks of hip implantation, a risk specifically associated with MoM implants in the form of a reactive periprosthetic soft tissue lesion has been documented in the literature in recent years. These periprosthetic lesions are known by a variety of terms, most commonly described as masses, cystic tumours, aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) [1], pseudotumours [2], or adverse reactions to metal debris [3]. Although these terms are sometimes used interchangeably not all periprosthetic pseudotumours demonstrate an ALVAL type response. The term ALVAL was first used in 2005 and relates to the histological findings of the periprosthetic reactive masses of necrotic tissue and dense perivascular lymphocyte
0846-5371/$ - see front matter Ó 2016 Canadian Association of Radiologists. All rights reserved. http://dx.doi.org/10.1016/j.carj.2015.10.006
Symptomatic metal-on-metal hip prosthesis / Canadian Association of Radiologists Journal 67 (2016) 76e81
infiltrates. The pathogenesis of such reaction remains unclear but a popular hypothesis is that metal ions are shed from the prosthesis and elicit a type IV hypersensitivity reaction [4]. Necrosis and macrophage infiltration, however, is a shared histological feature on all sampled periprosthetic masses, in keeping with a metal-induced cytotoxic effect [5]. In this article pseudotumour will be used to describe the abnormal periprosthetic masses. In 2012 regulatory authorities in the United Kingdom, Canada, the United States, and Australia issued alerts and safety communications related to MoM implants and guidance on the management of such patients [6e9]. A discussion on the management of a symptomatic patient is presented with recommended investigations, optimization of imaging modalities, expected radiological findings, and further treatment options. Presentation The incidence of pseudotumour varies widely in recently reported studies from 25%-68% [10e13]. This is in contrast to a meta-analysis, which calculated the pooled incidence estimate of pseudotumours to be much lower at 0.6% [14]. However, this is likely due to the inclusion of early studies, with more recent studies quoting much higher incidences especially when using more sensitive imaging techniques such as metal artifact reduction sequences magnetic resonance imaging (MRI), imaging a high risk patient cohort and following patients over a longer time period. Notably a recent study by Bosker et al [15] demonstrated a significant increase in incidence of pseudotumours after prolonged follow-up. The meta-analysis also found that 3.9% required hip revisions. However, when the studied patient population is separated by gender it is apparent that females have a significantly greater incidence of pseudotumours and of requiring hip revision due to pseudotumours compared to men with incidences as high as 9.4% and 6.2%, respectively. Other risk factors identified for the development of pseudotumours include resurfacing systems with small femoral heads, total hip replacements with large diameter femoral heads, bilateral implants, type of implant used, and suboptimal alignment of the implant [16,17]. Symptoms are nonspecific and pain is the most common presentation. A palpable mass may be appreciated on examination. In severe cases there may be evidence of femoral neuropathy. The time to presentation may vary with patients presenting from a few months to a number of years after surgery [18]. Investigations Serum Samples Patients with MoM implants are at an increased risk of having increased serum levels of chromium and cobalt than their metal-on-polyethylene counterparts [19]. The significance of raised serum metal ion levels is still debatable and it
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is mostly used as a surrogate marker to detect wear in MoM prostheses as there have been proven associations with high levels or increasing levels of metal ions and implant failure [20]. There are, however, documented cases of failure due to pseudotumour without significantly raised serum metal ions. Many regulatory authorities now recommend monitoring of serum metal ion levels in all symptomatic patients with MoM with the Australian Government Therapeutic Goods also recommending monitoring of serum metal ion levels in asymptomatic patients [6e9]. Metal ion levels, however, should not be used in isolation when screening for MoM pseudotumours. Skin patch testing is useful in type IV hypersensitivity reactions. Although the underlying pathogenesis of pseudotumours remains unclear, a type IV hypersensitivity reaction is a popular hypothesis. Studies have shown a greater frequency of metal allergies in patients with MoM implants, including those with failed implants, however, skin patch testing for metal allergy is not recommended at present for the workup of symptomatic or failed MoM implants [21]. Radiography Radiography is the primary imaging modality for the follow-up of patients post THR. Findings such as periprosthetic loosening, medial calcar resorption, or femoral neck resorption can be seen in complicated cases (Figure 1). However, although these findings are not specific or sensitive for the presence of pseudotumours, in patients with a MoM prosthesis and radiographic abnormalities, pseudotumour should be considered. Furthermore, many patients with pseudotumours will have normal findings on plain radiograph [22]. MRI MRI is the most useful investigation in the assessment of the postoperative MoM prosthesis of the surrounding soft tissues. While traditionally the presence of metal prostheses would preclude accurate evaluation of the adjacent soft tissues due to the presence of metal-induced susceptibility artifact, recent advances in the imaging of metal prostheses with the use of metal artifact reduction sequences now allows evaluation and diagnosis of periprosthetic soft tissue abnormalities. Parameters employed include increasing the receiver bandwidth or increasing the field of view with the vast majority of susceptibility reduction achieved by increasing the receiver bandwidth alone [23]. Fast spin echo sequences allows reduction of dephasing time and thus the amount of susceptibility artifact seen. A short echo time also reduces the time available for dephasing and is generally recommended, although there are reports into the usefulness of long echo time T2-weighted sequences that pick up blooming artifact from soft tissue metallic deposits [24]. Inversion recovery techniques are preferred to fat suppression. Finally, switching direction of phase- and frequency-encoding between acquisitions allows for greater visualization of the soft tissues due to differing susceptibility artifact in each direction.
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Figure 1. Initial (A) and subsequent (B) follow up radiograph demonstrated new lucency (circle) at the medial aspect of the femoral component of the right prosthesis.
Periprosthetic pseudotumours typically do not enhance following the administration of intravenous contrast and the use of contrast is mostly useful in its exclusion of other possible soft tissue collections [24]. While MRI is most likely to pick up a soft tissue abnormality associated with MoM athroplasties, both the imaging findings and locations of pseudotumours can vary widely making the diagnosis of MoM pseduotumours on imaging alone difficult. As well as this, the presence of periprosthetic masses on the imaging of asymptomatic functioning hips has been noted by Hart et al [10] who went on to show no difference in the prevalence of a periprosthetic mass in symptomatic patients versus asymptomatic matched controls. More recent studies have attempted to classify pseudotumours based on imaging findings and to correlate these findings with histology and outcome. First, any periprosthetic mass identified must be in communication with the hip joint before it can be considered as a MoM pseudotumour. A recent review paper classifies the masses according to MRI signal characteristics, with thin-walled cysts as Type I, thick-walled cysts as Type II, and predominantly solid masses as Type III. It was noted that cystic lesions were more likely to be located posteriorly and predominantly solid lesions anteriorly. In particular, a ‘‘characteristic’’ signal intensity was noted when the cystic wall or solid component of the periprosthetic mass demonstrated a lower signal intensity relative to muscle, which was presumed to represent metallic components (Figures 2-4) [2]. An alternative classification grades the severity of pseudotumour as mild, moderate, or severe depending on size and extension from
the periprosthetic tissues into the intramuscular compartments or evidence of bone involvement [25]. The more solid the lesion is the more likely it is to cause symptoms, have histological findings of pseudotumour, and have associated complications of local tissue or bony destruction [2,26]. Ultrasound Ultrasound is a cheap and readily available test that is less affected by the presence of an adjacent metal prosthesis. A recent study has shown the benefit of ultrasound as a screening tool for the detection of pseudotumours [27] and many regulatory authorities have recommended that the initial screening test may be an ultrasound or a metal artifact reduction sequences MRI [6e9]. Ultrasound findings usually consist of a periprosthetic fluid collection or soft tissue mass (Figure 5). One of the main limitations of ultrasound is that it is user dependent. As well as screening for the presence of a pseudotumour, ultrasound can be used to obtain tissue samples from the visualized periprosthetic masses. A prospective cohort study by Bosker et al [13] sampled a proportion of identified pseudotumours using 16-gauge needles. While the samples obtained confirmed the presence of lymphocytes and metal debris, the sample sizes were found to be insufficient to reliably calculate a pseudotumour score. Definitive histological diagnosis therefore was mostly obtained at the time of the revision surgery. Ultrasound-guided biopsy in the work-up of a patient with a painful MoM arthroplasty prior to definite surgical revision therefore is infrequently undertaken and not
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Figure 2. Coronal and axial T1 weighted (A, B) and STIR weighted (C, D) images demonstrate large joint effusions extending into the iliopsoas bursae bilaterally and extending into the trochanteric bursa. These collections communicate with the hip joints bilaterally (asterisk) and demonstrate multiple foci of internal debris (arrows). The periprosthetic collections have a marked low signal rim (dashed arrows) and an irregular capsule.
explicitly recommended in various published guidelines. A recent article describing to a multidisciplinary approach to managing patients with symptomatic MoM pseudotumours did not include histological confirmation as part of the specialized investigations prior to undertaking hip revision. Symptomatic hips were only aspirated when infection needed to be excluded [28]. Treatment of a Pseudotumour Symptomatic Patient Once a pseudotumour is suspected the decision to perform a hip revision may be taken in conjunction with patient symptoms, patient metal ion serum levels, and orthopaedic opinion. In some instances a second orthopaedic opinion is recommended prior to embarking on surgical revision [7]. Intraoperative findings range from a smooth-walled fluid collection, which is in continuity with the joint to thickened
synovium or pseudocapsule formation to necrotic soft tissue masses. Inflammation and destruction of local tissues may also be seen with associated complications such as tendon avulsion or bony osteonecrosis [23,29]. Female patients have an eightfold greater risk of requiring hip arthroplasty revision than men. However, the outcome of hip revision with conventional polyethylene or other ceramic materials is variable, with patients often reporting little change to their initial presenting symptoms possibly because of the severity of the pseudotumour at the time of hip revision [17,30]. The preoperative imaging findings of the pseudotumour can persist, thus making MR interpretation of revised hip arthroplasties difficult [23]. Asymptomatic Patient In a study by Hauptfleisch et al [2] they noted that pseudotumours were incidentally seen in a number of their recruited ‘‘asymptomatic controls.’’ However, they felt that
Figure 3. Axial and coronal T2-weighted fast spin echo (A, B), coronal T1-weighted images (C) demonstrate a large left iliopsoas bursa (arrows) communicating with the anterior hip joint with multiple foci of low signal and debris. A similar but smaller right iliopsoas bursa is also present with foci of low signal and internal debris (dashed arrow).
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Figure 4. Coronal T2-weighted fast spin-echo (A) and coronal T1-weighted images (B) demonstrate bilateral joint effusions, larger on the left, which demonstrate multiple foci of internal debris. The effusions have a marked low signal rim and an irregular capsule.
this cohort did actually have some mild symptoms as well as suboptimal functional scores once further evaluated. However, in a different study by Hart et al [10] they demonstrated no difference in the prevalence of a periprosthetic mass in symptomatic patients versus asymptomatic matched controls. What was noted however was that the pseudotumour was larger in size in the symptomatic patient. Similarly, in a recent retrospective study by Sutphen et al [12] they found a high prevalence of pseduotumours in asymptomatic patients, although there was a higher incidence of pseudotumours in the symptomatic cohort. Interestingly they did not find a significant difference in serum metal ion level and pseudotumour formation, in contrast to earlier studies [13,31], and thus further questioning the reliability of serum metal ion levels as a suitable screening test. The uncertainty of the management of a patient with a MoM implant is most notable in the asymptomatic patient and this is echoed in the contrasting recommendations of patient management across many national health-governing bodies. Health Canada recommends that the asymptomatic patients should be followed annually with a functional assessment and examination for 5 years postoperatively and thereafter as per local protocol. There is no specific recommendation for testing of metal ion levels or soft tissue imaging of the asymptomatic patient [7]. Similarly, the U.S. Food and Drug Administration recommends clinical examination and functional assessment at routine follow-up. Additional testing in the form of metal ion levels and soft
tissue imaging is not currently recommended in the absence of symptoms or reduction in implant functionality [8]. The UK Medical and Healthcare products Regulatory Agency however do recommend screening of the asymptomatic patients with high-risk arthroplasties for high metal ion levels as well as clinical assessment. Screening in the form of soft tissue imaging using ultrasound or MRI is not recommended unless the patient becomes symptomatic or demonstrates rising metal ion levels. They also recommend annual patient follow-up for the life of the implant in the highest risk implants (DePuy implants and all large-diameter femoral head stemmed systems) [6]. The Australian Government Therapeutic Drugs Administration recommend annual follow up for the life of the implant in high risk implants as well as serial blood metal ion levels and imaging in the form of radiographs plus ultrasound or MRI. They also suggest considering hip revision in this cohort of patients if there is evidence rising metal ion levels or significant imaging pseudotumour [9]. Notably there are no specific recommendations among these bodies regarding the need for obtaining biopsies and histological diagnosis from the periprosthetic mass in either the symptomatic or asymptomatic patient. Conclusion Pseudotumours or ALVAL are an increasingly recognized and reported complication of a MoM hip arthroplasty. The
Figure 5. Ultrasound images demonstrating a thick walled, cystic lesion in close proximity to the right hip joint. Internal iso- and hyperechoic debris is demonstrated lying within the lesion. It is often difficult to determine if this lesion is in continuity with the hip joint on ultrasound and cross-sectional imaging is usually then undertaken to further characterise the abnormality.
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typical patient will be female, with a small femoral head component, and suboptimal implant alignment. Most patients will present with symptoms of pain. Initial investigations include serum metal ion levels and either ultrasound or MRI, and these initial investigations are also recommended in asymptomatic patients as part of their postoperative surveillance by many regulatory authorities. Plain radiographs may also be of benefit, but a negative radiograph does not exclude an underlying pseudotumour. The imaging appearances and position of the lesions on MRI vary making the diagnosis difficult; however. MRI optimization and increased radiologist awareness of the expected findings of pseudotumour assists in the diagnosis of these complex cases. References [1] Willert HG, Buchhorn GH, Fayyazi A, et al. Metal-on-metal bearings and hypersensitivity in patients with artificial hip joints. A clinical and histomorphological study. J Bone Joint Surg Am 2005;87:28e36. [2] Hauptfleisch J, Pandit H, Grammatopoulos G, et al. A MRI classification of periprosthetic soft tissue masses (pseudotumours) associated with metal-on-metal resurfacing hip arthroplasty. Skeletal Radiol 2012; 41:149e55. [3] Langton DJ, Jameson SS, Joyce TJ, et al. Early failure of metal-on-metal bearings in hip resurfacing and large-diameter total hip replacement: a consequence of excess wear. J Bone Joint Surg Br 2010;92:38e46. [4] Granchi D, Cenni E, Tigani D, et al. Sensitivity to implant materials in patients with total knee arthroplasties. Biomaterials 2008; 29:1494e500. [5] Kwon YM, Ostlere SJ, McLardy-Smith P, et al. ‘‘Asymptomatic’’ pseudotumors after metal-on-metal hip resurfacing arthroplasty: prevalence and metal ion study. J Arthroplasty 2011;26:511e8. [6] Medication and Healthcare Products Regulatory Agency. Metal-onMetal (MoM) Hip Replacements. 2012. Available at: http://www.mhra. gov.uk/home/groups/dts-bs/documents/medicaldevicealert/con155767. pdf. Accessed September 14, 2014. [7] Health Canada. Metal-on-Metal Hip Implants - Information for Orthopaedic Surgeons Regarding Patient Management Following Surgery - For Health Professionals. 2012. Available at: http://www. healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2012/15835a-eng. php. Accessed September 14, 2014. [8] U.S Food and Drug Administration. Concerns about Metal-on-Metal Hip Implants. 2015. Available at: http://www.fda.gov/MedicalDevices/ ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetal HipImplants/ucm241604.htm. Accessed April 22, 2015. [9] Australian Government Therapeutic Goods Administration. Metal-onMetal Hip Replacement Implants. 2014. Available at: http://www.tga. gov.au/hp/information-devices-mom-hip-implants.htm#.VBW-xZRdWSo. Accessed September 14, 2014. [10] Hart AJ, Satchithananda K, Liddle AD, et al. Pseudotumors in association with well-functioning metal-on-metal hip prostheses: a casecontrol study using three-dimensional computed tomography and magnetic resonance imaging. J Bone Joint Surg Am 2012;94:317e25. [11] Williams DH, Greidanus NV, Masri BA, et al. Prevalence of pseudotumor in asymptomatic patients after metal-on-metal hip arthroplasty. J Bone Joint Surg Am 2011;93:2164e71. [12] Sutphen SA, MacLaughlin LH, Madsen AA, et al. Prevalence of pseudotumor in patients after metal-on-metal hip arthroplasty evaluated with metal ion analysis and MARS-MRI. J Arthroplast 2016;31:260e3.
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[13] Bosker BH, Ettema HB, Boomsma MF, et al. High incidence of pseudotumour formation after large-diameter metal-on-metal total hip replacement: a prospective cohort study. J Bone Joint Surg Br 2012; 94:755e61. [14] Wiley KF, Ding K, Stoner JA, et al. Incidence of pseudotumor and acute lymphocytic vasculitis associated lesion (ALVAL) reactions in metal-on-metal hip articulations: a meta-analysis. J Arthroplasty 2013; 28:1238e45. [15] Bosker BH, Ettema HB, van Rossum M, et al. Pseudotumor formation and serum ions after large head metal-on-metal stemmed total hip replacement. Risk factors, time course and revisions in 706 hips. Arch Orthop Trauma Surg 2015;135:417e25. [16] Murray DW, Grammatopoulos G, Pandit H, et al. The ten-year survival of the Birmingham hip resurfacing: an independent series. J Bone Joint Surg Br 2012;94:1180e6. [17] Glyn-Jones S, Pandit H, Kwon YM, et al. Risk factors for inflammatory pseudotumour formation following hip resurfacing. J Bone Joint Surg Br 2009;91:1566e74. [18] Donell ST, Darrah C, Nolan JF, et al. Early failure of the Ultima metalon-metal total hip replacement in the presence of normal plain radiographs. J Bone Joint Surg Br 2010;92:1501e8. [19] Engh CA, MacDonald SJ, Sritulanondha S, et al. Metal ion levels after metal-on-metal total hip arthroplasty: a five-year, prospective randomized trial. J Bone Joint Surg Am 2014;96:448e55. [20] Hart AJ, Sabah SA, Sampson B, et al. Surveillance of patients with metal-on-metal hip resurfacing and total hip prostheses: a prospective cohort study to investigate the relationship between blood metal ion levels and implant failure. J Bone Joint Surg Am 2014;96:1091e9. [21] Thomas P, Braathen LR, Dorig M, et al. Increased metal allergy in patients with failed metal-on-metal hip arthroplasty and peri-implant Tlymphocytic inflammation. Allergy 2009;64:1157e65. [22] Toms AP, Marshall TJ, Cahir J, et al. MRI of early symptomatic metalon-metal total hip arthroplasty: a retrospective review of radiological findings in 20 hips. Clin Radiol 2008;63:49e58. [23] Toms AP, Smith-Bateman C, Malcolm PN, Cahir J, Graves M. Optimization of metal artefact reduction (MAR) sequences for MRI of total hip prostheses. Clin Radiol 2010;65:447e52. [24] Yanny S, Cahir JG, Barker T, et al. MRI of aseptic lymphocytic vasculitis-associated lesions in metal-on-metal hip replacements. AJR Am J Roentgenol 2012;198:1394e402. [25] Anderson H, Toms AP, Cahir JG, et al. Grading the severity of soft tissue changes associated with metal-on-metal hip replacements: reliability of an MR grading system. Skeletal Radiol 2011;40:303e7. [26] Nawabi DH, Gold S, Lyman S, et al. MRI predicts ALVAL and tissue damage in metal-on-metal hip arthroplasty. Clinical orthopaedics and related research 2014;472:471e81. [27] Muraoka K, Naito M, Nakamura Y, et al. Usefulness of ultrasonography for detection of pseudotumors after metal-on-metal total hip arthroplasty. J Arthroplasty 2015;30:879e84. [28] Berber R, Pappas Y, Khoo M, et al. A new approach to managing patients with problematic metal hip implants: the use of an Internetenhanced multidisciplinary team meeting: AAOS exhibit selection. J Bone Joint Surg Am 2015;97:e20. [29] Watters TS, Cardona DM, Menon KS, et al. Aseptic lymphocytedominated vasculitis-associated lesion: a clinicopathologic review of an underrecognized cause of prosthetic failure. Am J Clin Pathol 2010; 134:886e93. [30] Grammatopoulos G, Pandit H, Kwon YM, et al. Hip resurfacings revised for inflammatory pseudotumour have a poor outcome. J Bone Joint Surg Br 2009;91:1019e24. [31] Hart AJ, Sabah S, Henckel J, et al. The painful metal-on-metal hip resurfacing. J Bone Joint Surg Br 2009;91:738e44.