Metal-on-metal articulations generate approximately to particles PSEUDOTUMORS FACTORS PATHOGENESIS

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1 PSEUDOTUMORS Vasu Pai ARMD Adverse reaction to metal debris. Langton identified that there is no clear consensus in the literature defining the boundaries of the terms metallosis, aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL), pseudotumors used the term adverse reactions to metal debris FACTORS The duration of follow-up did not prove to be a predictor. In some developed between 1.5 two years postoperatively, suggesting patient susceptibility is an important etiological factor. In revision surgery, 98 pseudotumors were found in 167 ASR MoM hips (59%). Some studies have suggested that edge-loading, resulting from adverse cup orientation, leads to more wear. In a recent study it was shown a rate of pseudotumor formation in hips with well-positioned metal-on-metal hip replacements to be similar to that in hips with replacements positioned outside the safe zone. Inclination angle did not prove to be a predictor in a recent study. PATHOGENESIS Metal-on-metal articulations generate approximately to particles

2 every year, which is 13,500 times the number of polyethylene particles produced from a typical metal-on-polyethylene bearing. a. Polywear pseudotumor Polyethylene debris is taken up by macrophage giant cells that release prostaglin E 2, which resorbs bone, causing the implant to loosen leading to a vicious cycle of wear loosening. Usually represent a nonspecific foreign-body reaction. b. Metallosis pseudotumor Willert et al. revealed an active cellular reaction with diffuse perivascular infiltrates of lymphocytes plasma cells, increased endothelial venules, fibrin exudation, accumulation of macrophages with drop-like inclusions, infiltrates of eosinophilic granulocytes necrosis. These histological findings were described as ALVAL [hypersensitivity reaction] Incidence: It was thought to be 1% symptomatic pseudotumor 5% asyptomatic pseudotumor with surface replacement [high in modular due to increase trunion corrosion as in ASR]. Recent report [JBJS 95-A,17:1560] indicates the prevalence of pseudotumors was high (28%). Most of the pseudotumors (72%) were asymptomatic. Recently Williams et al. found a 25% prevalence of pseudotumors detected by ultrasound in twenty asymptomatic hips after a resurfacing arthroplasty Modes of failure metal on metal [Orthop Clin N Am 46 (2015) ] 1. Biological mechanism: ALTRs [associated lesion tissue reactions] caused by the inflammatory response to metal debris. These local responses can result in tissue necrosis adverse soft tissue reactions. It is likely a type IV hypersensitivity response initiating T lymphocytes macrophages to create a cytotoxic inflammatory response [originally described as ALVAL] 2. Corrosion in Hip arthroplasty at Trunion: Newly described complication of modularity of Hip joint. It occurs at head neck junction. It gives rise to ALTR. Mechanically assisted crevice corrosion between two metallic surfaces can wear away the protective oxide layers on the metal surfaces. Once the

3 oxide layer is compromised, corrosion at the junction can occur through a complex chemical reaction. Taper corrosion is often treated with head ball exchange with placement of a ceramic head ball with a titanium sleeve. 3. Cup malalignment: A high abduction angle leads to diminished bearing lubrication leading to increased ion release soft tissue reactions. A relatively horizontal cup position may increase lubrication leading to improved wear characteristics. Unfortunately, may account for edge loading. CLINICAL FEATURES 1. Painful THR with or without click 2. Pain is usually in the groin or trochanteric region 3. Pressure effects on vital structures in the vicinity, including veins, nerves, ureters. 4. Suboptimal component positioning The recent focus on pseudotumors associated with metal-on-metal bearings indicates that pseudotumors are associated not only with a soft-tissue mass osseous changes of osteolysis erosions but also with damage to the periarticular soft tissue. The damage may lead to soft-tissue muscle necrosis, osseous denudation, pathological fractures, hip dislocations. The problem of hypersensitivity to metal in patients with metal-on-metal bearings has been suspected, investigated, debated for over thirty years. INVESTIGATIONS 1. Suspect: when there is groin hip pain. Urine Serum for Chromium Cobalt Whole-blood metal ion levels were slightly elevated (cobalt 7.5 ppb chromium 5.8 ppb; [normal reference values are < 0.8 ppb for Co Cr] 2. Radiographs to exclude aseptic implant loosening, femoral neck stress fracture or collapse of the femoral head, femoroacetabular impingement. Identify prosthesis: ASR more than Birmingham 3. Alignment: more with malaligned [due to edge loading] more with excessive cup inclination or anteversion.

4 4. Multi-slice computed tomography scanning is necessary to assess femoral neck anteversion. 5. MRI Types of Pseudotumors I Thinned wall cyst II Thick walled cyst Acta Orthop Downloaded from informahealthcare.com by on 11/10/14 Acta Orthop Downloaded from informahealthcare.com by on 11/10/14 For personal use only. For personal use only. 476 Acta Orthopaedica 2014; 85 (5): A A B B Acta Orthopaedica 2014; 85 (5): III Predominantly solid swelling extending to Iliopsoas area C Figure 1. Images from a 70-year-old man who had undergone total hip arthroplasty of the right hip 3.4 years earlier. He had a tingling sensation inathe trochanteric region the replaced right hip made clacking sounds. Whole-blood metal ion levels were slightly elevated (cobalt 7.5 ppb chromium 5.8 ppb; normal reference values are < 0.8 ppb for Co Cr). Axial view of a thin-walled cystic pseudotumor in the greater trochanteric region (arrows) with fluid-like low signal intensity in T1 (panel A) high in STIR (B). A thin-walled fluid-filled pseudotumor with metal staining was encountered at revision surgery (C). C Figure 2. Images from a 64-year-old woman who had undergone total hip arthroplasty of the right hip 4.7 years earlier. She had stiffness exercise-related pain in the replaced right hip. Whole-blood cobalt was D ppb chromium was 4.8 ppb (normal reference values are < ppb Co Cr). A thick-walled pseudotumor with solid total content was Figure 3. for Images from a 43-year-old woman who had undergone seen extending the hipreplaced joint region on the right hip arthroplasty of theposterolaterally left hip 2.5 years from earlier. Her hip made side.sounds, Variable signal intensity was seen A). Synovial clacking she also had intense painininaxial botht1 the(panel groin in the trochanteric region during exercise even at rest. Wholehypertrophy was best seen in coronal STIR view (B). A mixed-type cobalt was 8.8 chromium was 3.1 ppbcontents (normal was ref- seen at pseudotumor withppb thick walls partially solid 12blood erence valuessurgery are < 0.8 revision (C).ppb for Co Cr). A. Axial T1 view of a B controlled for by performing the same analyses with all bilateral patients excluded. IBM SPSS Statistics 20 was usedthick-walled partly cystic large pseudotumor mass extending from the iliopsoas region to the posterolateral region. The posterolateral part of for statistical analysis. the pseudotumor appeared mostly solid with variable signal intensity in T1 (panel B) STIR (C). A predominantly solid pseudotumor was encountered in revision surgery (D). Ethics such as metallosis, synovitis, capsular necrosis, osteolysis, or The institutional review board approved this study (April 27, any combination of these findings (Table 1). 2011; R11006) procedures followed were in accordance Based on imaging, a pseudotumor was detected in 79 hips with Helsinki Declaration of Informed consent was If (Table 2). performed Preoperative a sensitivity MRI was less MRI than 3provided months before revisionof 71% C from all participants. obtained (CI: it62 79) aasensitivity specificityofof88% 87% (CI:a 77 93) for of detecting surgery, provided specificity 78% Thus, for detecting (Table 3).value of pseudotumors. MRI hadpseudotumors a positive predictive Sensitivity substantially lowervalue in a of sub89% (CI: 80 94) was a negative predictive 68% (CI: Table 1. Demographics group of patients who hadwere been similar imaged in with 58 77). Sensitivity specificity the THR MRI more than 1 year before revision surgery Results group (72% 89%) the HR group (68% 79%). Of Total ASR resurfacing ASR XL THR (Table 3). Of the 28 pseudotumors previously Perioperatively, pseudotumors were found in 98 hips (59%). the 28 pseudotumors mentioned that that were were not not detected detectedby bymri, MRI,27 were Hips, n Hematologic testing microbiological assessment of joint aspirate is needed Of these, 87 were fluid-filled, 2 appeared solid, 9 were fluid-filled had 1 was 9 pseudotumors seen in pre11 beenmixed-type. imaged more than 1 year before Mean age (range), years 62 (19 85) 54 (19 67) 64 (38 85) ratioall 167 hips had 1.8 intracapsular 2.0ARMD lesions 1.7 revision. fluid-filled pseudotumors in offemale/male mixed type. operative MRI were3not found during revisionfound surgery. Mean time between primary revision (range), years Mean time between MRI revision (range), months 4.7 ( ) 5.4 ( ) 4.5 ( ) 8.1 ( ) 6.7 ( ) 8.8 ( ) THR: total hip replacement; MRI: magnetic resonance imaging. Table 2. Cross-tabulation of MRI revision findings revision were not seen at MRI performed less than 3 months before revision surgery. Furthermore, 8 fluid-filled pseudotumors were not detected at MRI performed between 3 6 months before revision. to

5 rule out infection. 8.Positive bone scan studies can indicate infection/loosening. 9. In the past, skin patch testing was used. The value of patch testing is limited 10. Biopsy tissue analysis allows an appropriate diagnosis of these reactions. Biopsy ARMD Fig. 3 Low-power photomicrographic image of ARMD (adverse reactions to meta debris), demonstrating the dense, deep eosinophilic (pink) fibrinoid material lining the pseudocyst (upper lower area), with the thick dens (blue) lymphoid aggregates, composed of lymphocytes plasma cells, between the fibrinoid material. The white arrow indicates lymphocytic aggregates, the black arrow indicates fibrinoid necrosis tissue organization (hematoxylin eosin stain, original magnification, 25). The clinician cannot rely solely on a single variable to determine the need for intervention, multiple variables must be considered. TREATMENT Follow up Guidelines: Varies 1. Pseudotumors in patients with metal-on- polyethylene implants A cementless revision prosthesis combined with cancellous bone-grafting. Logical to use: ceramic or ceramic; or poly Vs metal 2. Metal-on-metal bearing hip replacement fails from a pseudotumor

6 There is growing support for an early revision to a non- metal-on-metal bearing hip arthroplasty 3. Trunnionosis: If trunnionosis is encountered at the time of revision surgery, the trunnion should be cleaned carefully. If severe corrosion is not present, stem retention is usually preferred because of the morbidity encountered with removal of well-fixed cementless stem. Revision consists of eliminating as much of the cobalt from the system as possible, thereby revising the head to a ceramic head with a titanium sleeve. As with MoM bearing revisions, there should be a drop in the cobalt chromium ion levels after revision REFERENCES 1. McKellop (2001) Bearing surfaces in total hip replacements:. Instr Course Lect 50: ] 2. ASR failure. J Bone Joint Surg Br 93(8): ]. 3. Waldstein (2014) Acetabular osteolysis around metal-on-metal Birmingham THA. Archives of Orthopaedic Trauma Surgery, Volume 134, Issue 7, pp Liddle (2013) Revision of metal-on-metal hip arthroplasty in a tertiary center: a prospective study of 39 hips with between 1 4 years of follow-up. Acta Orthop 84(3): Relli (2013) Radiographically undetectable periprosthetic osteolysis with ASR implants: the implication of blood metal ions. J Arthroplasty 28(8): Meyer H (2012) Corrosion at the cone/taper interface leads to failure of largediameter metal-on metal total hip arthroplasties. Clin Orthop Relat Res 470(11): Willert HG, Buchhorn GH, Fayyazi A, Flury R, Windler M, Koster G, Lohmann CH (2005) Metal-on-metal bearings hypersensitivity in patients with artificial hip joints. A clinical histomorphological study. J Bone Joint Surg Am 87(1): Pseudotumors. J Am Acad Orthop Surg 2011;19:

7 9. Fehring. Modes of Failure in Metal-on-Metal Total Hip Arthroplasty. Orthop Clin N Am 46 (2015) Individual motion patterns during gait sit-to-st contribute to edgeloading risk in metal-on-metal hip resurfacing. Proc Inst Mech Eng H Jul;227(7): J Biomech Jan 21;48(2): International Orthopaedics (SICOT) (2014) 38: [Germany] 13. Metal-on-metal bearing [Metasul]. International Orthopaedics (SICOT) (2014) 38: Lainiala. Acta Orthopaedica 2014; 85 (5): Bhari. J Bone Joint Surg Am. 2012;94: Bisschop. JBJS. 95-A 17: Modes of Failure in Metal-on-Metal THR. Orthop Clin N Am 46 (2015) 185 Table 1 Follow-Up Guidance for Large-Diameter Metal-on-Metal Hip Arthroplasty Patients Published by Worldwide Authorities. Distinguishes between HR largediameter THA Follow-up protocol Follow-up for symptomatic patients Follow-up for asymptomatic patients MHRA UK [16] EFORT Europe [17] FDA USA [18] TGA Australia [19] Health Canada [20] Yes Yes No Yes No All THA 36 mm + symptomatic HR annually for implant life Asymptomatic HR a as per local protocol All MoM hips = ions + imaging THA = ions b HR = see above All THA 36 mm HR with risk factors d annually for implant life All HR without risk factors annually for first 5 years (then as per local protocol) All MoM hips = x- ray + ions + imaging All MoM hips = x- ray + ions Further imaging if x-ray abnormal or Co between 2 7 μg/l Whole blood (Co only) All MoM hips c Asymptomatic = every 1 to 2 years Symptomatic = at least every 6 months All MoM hips = x-ray + ions + imaging Clinical review All MoM hips with symptoms, & asymptomatic THA 36 mm or HR 45 mm at least annually Other MoM hips with no symptoms as per practice for non-mom hips All MoM hips = x- ray + ions + imaging Asymptomatic THA 36 mm or HR 45 mm = x- ray + ions + imaging Other MoM hips with no symptoms (see above) Whole blood or serum (Co Cr) All MoM hips with symptoms no guidance given on regularity of follow-up All MoM hips without symptoms annually for first 5 years (then as per local protocol) c All MoM hips = x-ray + ions + imaging Clinical review Metal ion sampling Whole blood (Co /or Cr) Whole blood (Co /or Cr) Whole blood or serum (Co Cr) Metal ion N7 μg/l 2-7 μg/l None stated None stated N7 μg/l thresholds of concern Plain Not stated All patients Symptomatic patients only All patients Symptomatic radiographs patients only recommended for any patients Cross-sectional MARS MRI MARS MRI or MARS MRI or MARS MRI or ultrasound MARS MRI imaging or ultrasound ultrasound or CT ultrasound or CT or ultrasound recommended Consider need for revision surgery If imaging abnormal /or blood metal ion levels rising (1) If imaging abnormal /or blood metal ion levels raised or rising (2) If Co N20 μg/l Decide in response to overall clinical scenario test results, but consider early revision in patients with progressive lesions If persistent symptoms, imaging abnormalities /or where blood metal ions are rising If symptoms positive MRI (soft-tissue mass) If positive MRI (soft-tissue mass), increasing in size Cr = chromium; Co = cobalt; CT = computedtomography; EFORT = European Federation ofnational Associationsof Orthopaedics Traumatology; FDA = Food DrugAdministration; HR = hip resurfacing; MHRA = Medical Healthcare Products Regulatory Agency; MARS MRI = metal artefact reduction sequence magnetic resonance imaging; MoM = metal-on-metal; TGA = Therapeutic Goods Administration; THA = total hip arthroplasty; UK = United Kingdom; USA = United States of America. a Excludes Articular Surface Replacement hip resurfacing. b Imaging recommended if blood metal ion levels rising. c Advises closer follow-up for patients at increased risk of device wear such as females, those with bilateral implants, suboptimal component alignment, or hip resurfacings with small femoral head sizes (less than or equal to 44 mm). d Risk factors include small femoral head size (b50 mm), female gender, low coverage arc.