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Silent soft tissue pathology is common with a modern metal-on-metal hip arthroplasty

Silent soft tissue pathology is common with a modern metal-on-metal hip arthroplasty Acta Orthopaedica 2011; 82 (3): 301–307 301 Silent soft tissue pathology is common with a modern metal-on- metal hip arthroplasty Early detection with routine metal artifact-reduction MRI scanning 1 2 2 2 1 2 Henry Wynn-Jones , Rory Macnair , James Wimhurst , Nish Chirodian , Brian Derbyshire , Andoni Toms , and John Cahir 1 2 The Centre for Hip Surgery, Wrightington Hospital, Lancashire; Department of Trauma and Orthopaedics, Norfolk and Norwich University Hospital NHS Foundation Hospital, Norwich, Norfolk, UK Correspondence: hwj@doctors.net.uk Submitted 10-06-06. Accepted 10-12-16 Background and purpose Adverse reactions to metal debris et al. 1996). Improved manufacturing and engineering tech- have been reported to be a cause of pain in metal-on-metal hip niques enabled the development of a new generation of MoM arthroplasty. We assessed the incidence of both symptomatic and hip replacements. In the 1990s, the Birmingham Hip Resur- asymptomatic adverse reactions in a consecutive series of patients facing (BHR) was developed, and good early to medium-term with a modern large-head metal-on-metal hip arthroplasty. results have been published (Daniel et al. 2004, Treacy et al. Methods We studied the early clinical results and results of 2005, Heilpern et al. 2008). Similar implants, both resurfac- routine metal artifact-reduction MRI screening in a series of ings and large MoM bearings, coupled with standard femoral 79 large-head metal-on-metal hip arthroplasties (ASR; DePuy, stems were subsequently developed and marketed by other Leeds, UK) in 68 patients. 75 hips were MRI scanned at mean 31 manufacturers. (12–52) months after surgery. The development of magnetic resonance imaging (MRI) Results 27 of 75 hips had MRI-detected metal debris-related metal artifact reduction (MAR) sequences has enabled good abnormalities, of which 5 were mild, 18 moderate, and 4 severe. visualization of the periprosthetic tissues (Toms et al. 2008), 8 of these hips have been revised, 6 of which were revised for an and been reported to be a clinically useful part of the assess- adverse reaction to metal debris, diagnosed preoperatively with ment of painful MoM hip replacements (Hart et al. 2009). A MRI and conr fi med histologically. The mean Oxford hip score number of authors have described the appearance of collec- (OHS) for the whole cohort was 21. It was mean 23 for patients tions of fluid and inflammatory masses around painful MoM with no MRI-based evidence of adverse reactions and 19 for those hip arthroplasties (Boardman et al. 2006, Pandit et al. 2008, with adverse reactions detected by MRI. 6 of 12 patients with a Toms et al. 2008). These have been grouped under a variety best possible OHS of 12 had MRI-based evidence of an adverse of headings such as “aseptic lymphocyte-dominated vasculi- reaction. tis-associated lesions” (Willert et al. 2005), “pseudotumors” Interpretation We have found a high early revision rate with (Pandit et al. 2008), or “adverse reactions to metal debris a modern, large-head metal-on-metal hip arthroplasty. MRI- (ARMD)” (Langton et al. 2010). Although these lesions have detected adverse rections to metal debris was common and often been previously described in patients investigated for pain, clinically “silent”. We recommend that patients with this implant there have been no studies on the overall incidence of these should be closely followed up and undergo routine metal artifact- lesions in an unselected series of patients, including those with reduction MRI screening. no, or few, symptoms. It is not known whether these lesions  may occur in the absence of symptoms. At our institution, we have a policy of offering routine MAR MRI imaging to patients who have undergone MoM total hip Metal-on-metal (MoM) total hip replacements have been replacement or resurfacing. We determined the early clinical used since the 1960s. Failure in early designs was attributed outcome, revision rate, and incidence of ARMD using MAR to mechanical loosening caused by poor bearing tolerances MRI screening in a consecutive series of patients with an ASR producing high friction (Amstutz and Grigoris 1996, Kothari THR or resurfacing (ASR; DePuy, Leeds, UK). Open Access - This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the source is credited. DOI 10.3109/17453674.2011.579518 302 Acta Orthopaedica 2011; 82 (3): 301–307 angle was measured manually (on the earliest postoperative, Patients and methods anteroposterior, supine pelvis radiograph of sufficient qual - The ASR system was used at our institution between Feb- ity) with reference to the inter-teardrop line using tools on ruary 2005 and March 2008. This study is a report of the the PACS workstation. Acetabular component orientation was results of our standard follow-up and imaging protocol. 79 also measured using Wrightington cup orientation software. hip arthroplasties using ASR components were performed This enables measurement of inclination and version, and cor- in 68 patients by 5 surgeons. 17 ASR resurfacing procedures rects for angular artifact due to the central X-ray beam offset were performed in 14 patients. 62 THRs were performed in from the hip (Derbyshire and Porter 2003, Derbyshire 2008). 54 patients using an ASR acetabular component, a matched 2 of the authors (HWJ and BD) tested the inter-observer and cobalt-chrome ASR XL head, and a Corail titanium hydroxy- intra-observer reliability of this software using standard sta- apatite-coated uncemented stem (DePuy, Leeds, UK). 14 head tistical techniques (Bland and Altman 1983, Ranstam et al. sizes were available, ranging from 39 mm to 63 mm in diam- 2000). Using these measurements, we designated acetabu- eter in 2-mm increments. For the purposes of comparative lar components as being within or outside Lewinnek’s “safe analysis, we designated femoral head component sizes in the zone” (anteversion 5–25 degrees, and inclination 30–50 range 39–49 mm as “small”, and 51–63 mm as “large”. degrees) (Lewinnek et al. 1978). The mean age of the 79 cases (56 males) at the time of Serial radiographs were compared to assess for peripros- surgery was 55 (30–76) years. The mean time from the pri- thetic osteolysis, lucent lines, bone loss, prosthesis migration, mary procedure to last follow-up or revision was 32 (14–51) and soft tissue swelling. We noted osteolysis and radiolucent months. No patients had died or were lost to follow-up. Indi- lines greater than 1 mm around the acetabular component in cations for surgery were primary osteoarthritis (OA) (n = 70), the zones of DeLee and Charnley (DeLee and Charnley 1976) OA secondary to dysplasia (n = 3), post trauma (n = 2), avas- as modified by Beaulé et al. (2004). Radiolucency around the cular necrosis (n = 2), and OA secondary to Perthes’ (n = 2). femoral stem was recorded using the zones of Amstutz et al. (2004) for resurfacing arthroplasty and of Gruen for stemmed Implants total hip arthroplasty. The median size of the femoral head component was 49 (43– Metal artifact-reduction MRI 57) mm). For the resurfacing group, the median size was 51 (45–57) mm and for the THR group it was 49 (43–55) mm. 31 All MR examinations were performed on a 1.5T machine cases had a “large” femoral head (51–63 mm) and 48 cases a (Siemens Symphony; Siemens Healthcare, Erlangen, Ger- “small” head (38–49 mm). many) using sequences adapted for metal artifact suppression. All images were reviewed by two musculoskeletal radiolo- Follow-up assessments gists (each had 5 years’ experience in reporting MRI findings The departmental policy at our institution is that all patients around MoM hip prostheses of various designs) and consen- who have undergone a MoM hip replacement should remain sus findings were recorded. under review and be assessed annually. The review involves Findings were categorized as: normal (Cahir et al. 2007), clinical assessment, radiological assessment, and a patient- abnormal and typical of an adverse reaction to metal debris based self-assessment questionnaire. The questionnaire (Fang et al. 2008, Pandit et al. 2008, Toms et al. 2009), or includes the Oxford hip score (Dawson et al. 1996) (OHS) abnormal but typical of a disease other than a metal-on-metal (where 12 = best score and 60 = worst score), an assessment of reaction—e.g. infection (Cahir et al. 2007). For those cases the patients’ satisfaction with the outcome of their hip replace- with characteristic findings of ARMD, they were further clas - ment (possible responses: Yes, No, Uncertain), and rating the sified into mild, moderate, or severe disease (Figures 1–3). result of their hip replacement on a visual analog scale (VAS) Mild changes constituted periprosthetic collections less than from 0 (unsatisfactory) to 10 (perfect). 5 cm in diameter, moderate comprised soft tissue masses of Patients who were scheduled for revision were asked to com- fluid collections greater than 5 cm in diameter, gluteal muscle plete a questionnaire before to revision surgery. All patients at atrophy or bone marrow edema and severe changes including our hospital with a MoM hip replacement are also routinely extension through deep fascia, tendon avulsion, bone marrow invited to undergo an MRI scan, even if they are asymptomatic replacement or fracture, or neurovascular involvement. This (provided there are no contraindications). grading system has been shown to be reliable (Anderson et al. 2011). Plain radiographs Histopathology Plain radiographs were assessed by one of the authors (HWJ) on a diagnostic PACS workstation. The acetabular implant ori- The tissue specimens in those patients who were revised, or entation, leg length, offset, and femoral component alignment underwent a biopsy, were assessed by a histopathologist expe- were measured. Two techniques were used for measurement rienced in evaluation of metal debris-related periprosthetic of acetabular component orientation. Acetabular inclination tissue reactions. Acta Orthopaedica 2011; 82 (3): 301–307 303 Figure 1. Mild adverse reaction to metal Figure 2. Moderate adverse reaction to metal Figure 3. Severe adverse reaction to metal debris. Sagittal T2W MR through the femo- debris. A sagittal T2W MR positioned just debris. Coronal T1W MR through the mid-cor- ral stem (S) of a Corail total hip replacement medial to the acetabular cup demonstrates onal plane of the femoral head (black arrows demonstrating mild periprosthetic disease. A moderate periprosthetic disease with a large indicate the medial wall of the acetabulum), small fluid-filled cavity (asterisk) surrounding cystic collection, demarcated by a low signal demonstrating severe periprosthetic disease the neck of the prosthesis is encapsulated by wall (black arrow), and filled with debris (white with bone marrow replacement in the acetab- a thick, ragged low-signal rim (white arrow). arrow) extending proximally in the line of the ular roof (white arrow). iliopsoas bursa. The relatively thick low signal wall and the debris are not typical of conven- tional iliopsoas bursae. Statistics had neck thinning, with resorption of the superior aspect of the Statistical analysis was performed using StatsDirect statis- femoral neck on the anteroposterior radiograph. There was no tical software version 2.7.7 (StatDirect Ltd., Altrincham, lysis, and no radiolucent lines around the stem of the femoral UK). Dichotomous variables were analyzed using Fisher’s resurfacing component. exact test. Continuous parametric data were analyzed using 52 of the 62 Corail stems appeared well fixed on the latest unpaired t-tests and non-parametric data were assessed with radiographs, and had no radiolucent lines in any of the 7 Gruen the Mann-Whitney U-test. zones. 10 hips had radiolucent lines in 1 or more Gruen zone. In 7 of these hips, a radiolucent line was seen only in Gruen zone 1. 3 hips also had lucent lines in Gruen zone 7. In all 10 hips, the Corail femoral component appeared well fixed from Results zones 2 to 6, and had not migrated. Plain radiographs MAR MRI examinations The mean cup inclination angle measured manually on digi- tal plain radiographs was 50 (36–74) degrees. The acetabular 75 patients had MAR MRI examinations (59 THR, 16 resur- orientation using Wrightington cup orientation software had a facing) at a mean of 31 (12–52) months after surgery. 4 hips mean inclination of 50 (34–75) degrees and mean anteversion were not scanned because 2 patients (3 hips) had a contrain- of 12 (2.3–39) degrees. dication to MRI (1 pacemaker and 1 spinal cord stimulator) The intra- and inter-observer reliabilities of Wrightington and 1 patient declined to be scanned as he was claustropho- cup orientation software for measuring ASR acetabular ori- bic (Table 1). 42 MRI scans were classified as consistent with entation were satisfactory. The intra-observer repeatability normal postoperative appearances (including seromas and for version was ± 0.55 degrees, and it was ± 0.49 degrees for atrophy of the short external rotators). 33 scans were consid- inclination. The inter-observer limits of agreement (95%) for ered to be abnormal, of which 3 were not thought to be typi- version were –1.9 to 6.6 degrees, and for inclination they were cal of an adverse reaction to metal debris, including: infection –2.8 to 2.4 degrees. All 79 acetabular components appeared to (n = 1), iliopsoas bursa (n = 1), and osteolysis (n = 1). 27 be well fixed, with good bone ongrowth on the last follow-up scans were considered to be abnormal and demonstrated fea- radiograph. None of the acetabular components had osteoly- tures consistent with an adverse reaction to metal debris. 5 sis or radiolucent lines greater than 1 mm in any of the three cases were considered to be mild, 18 were considered moder- Charnley DeLee zones. ate, and 4 were classified as severe. The typical appearance 16 of the 17 resurfacing femoral components had no evi- was of a fluid signal collection extending from, and surround - dence of loosening, migration, neck thinning, or radiolucent ing, the bearing that was demarcated by a very low-signal lines around the stem in any of Amstutz zones. One patient capsule, which was often ragged. Debris and a heterogeneous 304 Acta Orthopaedica 2011; 82 (3): 301–307 Table 1. Summary of metal artifact-reduction (MAR) MRI findings Table 3. Summary of revisions MAR MRI findings A B C D E F G H I J K A B C D E F G H I J 1 51 F P 34 30 47 58 20 + + ASR resurfacing 7 0 2 3 1 6 3 1 17 2 59 M P 40 40 49 49 24 + + Corail with XL head 3 60 M S 34 15 51 60 13 + + and ASR cup 35 3 3 15 3 21 0 3 62 4 55 F P 38 46 51 56 13 + – Total 42 3 5 18 4 27 3 4 79 5 57 F P 32 14 51 57 3 (+) + a a 6 67 F P+S 23 22 45 53 + + A Prosthesis 7 60 M P 16 57 49 56 11 – – B Normal 8 55 M P 29 55 47 53 7 + + C Abnormal, not ARDM D Mild ARMD Only conventional radiograph available; cup inclination measured E Moderate ARMD manually. F Severe ARMD A Case G All ARDM B Age H Unclassifiable C Sex I Not scanned D Indication for revision J Total P pain S squeaking E Time to revision (months) F OHS Table 2. Metal artifact-reduction MRI findings in relation to potential risk G Head size (mm) factors for metal debris-related reactions H Cup inclination I Cup version J MRI findings MRI classification – normal Not ARMD ARMD p-value (+) mild (A and B) (C1, C2, C3) + moderate K Histology (+ ARMD) Sex, F / M 13 / 35 9 / 18 0.4 Mean head size (mm) 50 49 0.2 Mean acetabular inclination (°) 50 51 0.4 Mean acetabular anteversion (°) 13 12 0.2 > 50 mm, small: < 50 mm) and acetabular orientation (incli- Head, small / large 26 / 22 19 / 8 0.2 nation, version, and location within or outside Lewinneck’s Cup in Lewinnek’s “safe zone”, “safe zone”(Lewinnek et al. 1978)) are summarized in Table yes / no 24 / 21 10 / 16 0.2 2. There was an increased risk of MRI-detected adverse reac- tion to metal debris with small femoral heads and cup orienta- signal were common findings within the fluid collections. tion outside Lewinnek’s “safe zone”, but this increase was not The patients with severe disease included 3 cases with bone statistically significant. marrow replacement around either the acetabulum (n = 1) or Implant survival the proximal femur (n = 2), and 1 patient had encasement of the sciatic nerve. The radiologists were not able to classify 3 At a mean follow-up of 32 (14–51) months, 8 revisions had of the MRI examinations and recommended follow-up with been performed in 8 patients (4 female) (Table 3). The cumu- repeat imaging after a further 6 months. There were 2 cases lative revision rate at 40 months with revision for any reason of atrophy of the gluteus medius and minimus but no cases of was 11% (95% CI: 4–18). gluteal avulsion. There were 7 cases of bone marrow edema in All the cases that were revised had an ASR acetabular com- the proximal femur without any other abnormal findings. The ponent with an XL head and a Corail femoral component. 6 significance of bone marrow edema in the proximal femur is revisions were performed for pain (1 of these patients also unknown, but may be part of the spectrum of normal MAR reported squeaking). MRI confirmed an adverse reaction to MRI appearances in the absence of other changes. These cases metal debris before revision in 4 of these patients. 2 patients were classified as normal postoperative appearances. had minimal pain (1 had a squeaking hip), but screening MRI In patients with normal MAR MRI findings or abnormali - revealed changes consistent with a moderate adverse reac- ties that were not an adverse reaction, the mean corrected cup tion to metal debris in one case and mild in the other case inclination angle was 50 (34–75) degrees, the mean anteversion that was squeaking. Both patients elected to undergo revision. was 13 (2.3–33) degrees, and mean head size was 50 (43–57) The plain radiographs were unremarkable, with no osteolysis mm. In those patients with an adverse reaction to metal debris, in 7 of these patients. In 1 patient, there were radiolucencies the mean cup inclination was 50 (37–60) degrees, mean ante- with the appearance of a neocortex in Gruen zones 1 and 7. At version was 12 (2.3–39) degrees, and mean head size was 49 the time of revision, the proximal stem was found to be loose (45–57) mm. The MAR MRI findings, and potential risk fac - with necrotic tissue, metal-stained debris, and fluid between tors associated with ARMD, including sex, head size (large: the stem and the bone. The stem was well fixed distally. This Acta Orthopaedica 2011; 82 (3): 301–307 305 patient underwent revision of both components. In the remain- Table 4. Patient-related outcome in relation to MAR MRI findings ing revisions, the femoral component was preserved and the acetabular component revised to an uncemented acetabular A B C D E F G component with a polyethylene or ceramic liner. The XL Normal 42 33 5 4 7.9 23 heads were exchanged to appropriate ceramic heads to match Abnormal (not ARMD) 3 3 0 0 8 25 the acetabular components. Mild ARMD 5 5 0 0 9 18 Moderate ARMD 18 14 1 2 7.6 21 Histopathology Severe ARMD 4 4 0 0 9.5 13 Unclassifiable 3 3 0 0 9 15 All 6 patients with a MAR MRI diagnosis of ARMD had his- Not scanned 4 4 0 0 9.5 12 topathological findings (in the tissue taken at the time of revi - All 79 66 6 6 8.2 21 sion) consistent with an ARMD. The findings were similar in A MRI classification the 6 cases: a fibrous capsular wall was seen, showing fibri - B No. of cases noid proliferation, with surface necrosis. A wide band of bland Patient satisfaction: C Yes necrosis was seen. Perivascular lymphocytic infiltration was D Doubtful seen with macrophages or histiocytes containing small metal E No particles. F VAS (0–10): 0 = unsatisfactory; 10 = perfect. G OHS: 12 = best; 60 = worst. The histology in the 2 patients who were revised for pain, but with normal MRI scans, revealed normal fibrous tissue with no evidence of inflammation or adverse reaction to metal debris. worst MAR MRI findings. One quarter of patients with a best possible OHS (12) had MRI-based evidence of ARMD. This Patient-related outcome suggests that even a policy of frequent clinical review would All hips were assessed with a hip questionnaire and an OHS not detect patients developing soft tissue complications until at mean 32 (14–51) months after the primary procedure. The extensive damage had occurred. It is unclear why there is assessment scores were those at the latest follow-up or last often no pain. assessment prior to revision. A comparison can be made with the problem of silent oste- 66 patients were satisfied with their hip replacements olysis, which is well documented in patients with uncemented whereas 7 were not, and 6 were doubtful. The mean overall acetabular components with a polyethylene liner (Hozack et al. “success” rating by patients of their hip replacements (on a 1996, Utting et al. 2008). It is generally accepted that patients VAS from 1 to 10) was 8. with such implants should be routinely assessed from plain The mean OHS in all patients—either at the latest follow- radiographs—even in the absence of symptoms—in order up or before revision—was 21. In the 8 patients who had a to detect osteolysis before it becomes extensive. The differ- revision, the mean OHS before revision was 37. In patients ence with metal-on-metal related pathology is that soft tissue without MRI-based evidence of an adverse reaction to metal pathology is of particular concern, and this is not visible on a debris, the mean OHS was 23, and in those with MRI-based plain radiograph. We believe it is preferable to detect ARMD evidence of ARMD it was 19 (p = 0.3) (Table 4). soft tissue damage and fluid-filled cavities at an early stage 51 patients had an OHS at latest follow-up of 20 or less, and before the damage becomes extensive and irreversible. Gram- 18 of these patients had MRI-based evidence of an adverse matopolous et al. (2009) reported that resurfacing prostheses reaction to metal debris. 26 patients had a “perfect” OHS of revised for pseudotumors have a poor outcome. This may 12 at latest follow-up, and 6 of these had MRI-based evidence well be because, in their series, patients only presented once of ARMD. they had become symptomatic and the disease had become extensive. Our experience with an earlier-generation 28-mm bearing MoM prosthesis, used in the 1990s, was that it func- tioned well for several years and then some patients suddenly Discussion presented with severe extensive soft tissue and bone necrosis, We found MRI-detected metal debris-related abnormalities which was often undetectable on plain radiographs (Nolan et in one third of patients with a modern MoM bearing. Previ- al. 2008). ous studies have concentrated on the MRI findings in patients The pattern of disease seen in our series on MRI shares investigated for painful prostheses (Boardman et al. 2006, similarities with those previously described for other pros- Fang et al. 2008, Pandit et al. 2008, Toms et al. 2008). theses, but there are also key differences. The pseudocysts One of our most concerning findings was that MRI- in this group of patients commonly contained debris result- based evidence of an adverse reation to metal debris does ing in heterogeneous signal patterns (Figure 2), whereas those not appear to correlate with symptoms. In fact, some of the described with other prostheses were typically homogeneous highest levels of satisfaction were in those patients with the fluid-filled cavities (Fang et al. 2008, Toms et al. 2008, 2009). 306 Acta Orthopaedica 2011; 82 (3): 301–307 Gluteal myositis, atrophy, and avulsion have been described with this implant be carefully followed up on a regular basis. on MR with metal-on-metal-associated disease (Toms et al. We believe that routine assessment of these implants should 2008) but these were not common findings in our series of include soft tissue imaging. patients. This may be because MRI has been performed on asymptomatic patients and patients earlier in their postopera- tive course than previously described. HWJ: Main author, data collection, data analysis, radiographic analysis. RM: Coordinated imaging and MRI scans, data collection and radiographic analy- A number of factors, including female sex, small prosthetic sis. JW: Clinical follow-up and manuscript preparation. NC: Clinical follow- head size, “poor” acetabular component orientation, and com- up. BD: Radiographic analysis. AT: MRI scanning, interpretation and clas- ponent design may contribute to ARMD. Hart et al. (2009) sification. JC: MRI scanning, interpretation and classification have shown that in a series of 16 failed large-head MoM pros- theses, 13 were positioned outside the Lewinnek “safe zone”. We have found MRI-based evidence of MoM disease in 41% No competing interests declared. of prostheses with “small heads” (38–49 mm) and cup orienta- tions outside Lewinneck’s “safe zone”. With “large heads” and a cup within the “safe zone”, the incidence of MoM disease Amstutz H C, Grigoris P. Metal on metal bearings in hip arthroplasty. Clin Orthop (Suppl) 1996; (329): S11-34. was still one fifth. 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Adelaide: AOA; (2009). overall revision rate for ARMD was 8%. Other authors have Beaule P E, Dorey F J, LeDuff M, Gruen T, Amstutz H C. Risk factors affect- ing outcome of metal-on-metal surface arthroplasty of the hip. Clin Orthop reported a high early revision rate with the ASR. Langton et 2004; (418): 87-93. al. (2010) reported poor early results with the ASR system, Bland J M, Altman D G. Statistical methods for assessing agreement between with a revision rate for symptomatic ARMD of 3% at 3 years. two methods of clinical measurement. Lancet 1983; (i): 307-10. The revision rate in the subgroup of patients in their series Boardman D R, Middleton F R, Kavanagh T G. A benign psoas mass follow- with a total hip replacement (ASR cup, ASR XL head, and a ing metal-on-metal resurfacing of the hip. J Bone Joint Surg (Br) 2006; 88 (3): 402-4. Corail stem) rather than resurfacing was higher, at 6%. The Cahir J G, Toms A P, Marshall T J, Wimhurst J, Nolan J. 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Utting M R, Raghuvanshi M, Amirfeyz R, Blom A W, Learmonth I D, Ban- Lewinnek G E, Lewis J L, Tarr R, Compere C L, Zimmerman J R. Disloca- nister G C. The Harris-Galante porous-coated, hemispherical, polyethyl- tions after total hip-replacement arthroplasties. J Bone Joint Surg (Am) ene-lined acetabular component in patients under 50 years of age: a 12- to 1978; 60 (2): 217-20. 16-year review. J Bone Joint Surg (Br) 2008; 90 (11): 1422-7. Nolan J F, Darrah C, Donell S T, Wimhurst J, Toms A, Marshall T, Barker T, Willert H G, Buchhorn G H, Fayyazi A, Flury R, Windler M, Koster G, Lohm- Case C P, Peters C, Tucker J K. Metal on metal hip replacement. J Bone ann C H. Metal-on-metal bearings and hypersensitivity in patients with Joint Surg (Br) (suppl III) 2008; 90: 531. artificial hip joints. A clinical and histomorphological study. J Bone Joint Surg (Am) 2005; 87 (1): 28-36. Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons C L, Ostlere S, Athanasou N, Gill H S, Murray D W. Pseudotumours asso- ciated with metal-on-metal hip resurfacings. J Bone Joint Surg (Br) 2008; 90 (7): 847-51. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Acta Orthopaedica Taylor & Francis

Silent soft tissue pathology is common with a modern metal-on-metal hip arthroplasty

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10.3109/17453674.2011.579518
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Abstract

Acta Orthopaedica 2011; 82 (3): 301–307 301 Silent soft tissue pathology is common with a modern metal-on- metal hip arthroplasty Early detection with routine metal artifact-reduction MRI scanning 1 2 2 2 1 2 Henry Wynn-Jones , Rory Macnair , James Wimhurst , Nish Chirodian , Brian Derbyshire , Andoni Toms , and John Cahir 1 2 The Centre for Hip Surgery, Wrightington Hospital, Lancashire; Department of Trauma and Orthopaedics, Norfolk and Norwich University Hospital NHS Foundation Hospital, Norwich, Norfolk, UK Correspondence: hwj@doctors.net.uk Submitted 10-06-06. Accepted 10-12-16 Background and purpose Adverse reactions to metal debris et al. 1996). Improved manufacturing and engineering tech- have been reported to be a cause of pain in metal-on-metal hip niques enabled the development of a new generation of MoM arthroplasty. We assessed the incidence of both symptomatic and hip replacements. In the 1990s, the Birmingham Hip Resur- asymptomatic adverse reactions in a consecutive series of patients facing (BHR) was developed, and good early to medium-term with a modern large-head metal-on-metal hip arthroplasty. results have been published (Daniel et al. 2004, Treacy et al. Methods We studied the early clinical results and results of 2005, Heilpern et al. 2008). Similar implants, both resurfac- routine metal artifact-reduction MRI screening in a series of ings and large MoM bearings, coupled with standard femoral 79 large-head metal-on-metal hip arthroplasties (ASR; DePuy, stems were subsequently developed and marketed by other Leeds, UK) in 68 patients. 75 hips were MRI scanned at mean 31 manufacturers. (12–52) months after surgery. The development of magnetic resonance imaging (MRI) Results 27 of 75 hips had MRI-detected metal debris-related metal artifact reduction (MAR) sequences has enabled good abnormalities, of which 5 were mild, 18 moderate, and 4 severe. visualization of the periprosthetic tissues (Toms et al. 2008), 8 of these hips have been revised, 6 of which were revised for an and been reported to be a clinically useful part of the assess- adverse reaction to metal debris, diagnosed preoperatively with ment of painful MoM hip replacements (Hart et al. 2009). A MRI and conr fi med histologically. The mean Oxford hip score number of authors have described the appearance of collec- (OHS) for the whole cohort was 21. It was mean 23 for patients tions of fluid and inflammatory masses around painful MoM with no MRI-based evidence of adverse reactions and 19 for those hip arthroplasties (Boardman et al. 2006, Pandit et al. 2008, with adverse reactions detected by MRI. 6 of 12 patients with a Toms et al. 2008). These have been grouped under a variety best possible OHS of 12 had MRI-based evidence of an adverse of headings such as “aseptic lymphocyte-dominated vasculi- reaction. tis-associated lesions” (Willert et al. 2005), “pseudotumors” Interpretation We have found a high early revision rate with (Pandit et al. 2008), or “adverse reactions to metal debris a modern, large-head metal-on-metal hip arthroplasty. MRI- (ARMD)” (Langton et al. 2010). Although these lesions have detected adverse rections to metal debris was common and often been previously described in patients investigated for pain, clinically “silent”. We recommend that patients with this implant there have been no studies on the overall incidence of these should be closely followed up and undergo routine metal artifact- lesions in an unselected series of patients, including those with reduction MRI screening. no, or few, symptoms. It is not known whether these lesions  may occur in the absence of symptoms. At our institution, we have a policy of offering routine MAR MRI imaging to patients who have undergone MoM total hip Metal-on-metal (MoM) total hip replacements have been replacement or resurfacing. We determined the early clinical used since the 1960s. Failure in early designs was attributed outcome, revision rate, and incidence of ARMD using MAR to mechanical loosening caused by poor bearing tolerances MRI screening in a consecutive series of patients with an ASR producing high friction (Amstutz and Grigoris 1996, Kothari THR or resurfacing (ASR; DePuy, Leeds, UK). Open Access - This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the source is credited. DOI 10.3109/17453674.2011.579518 302 Acta Orthopaedica 2011; 82 (3): 301–307 angle was measured manually (on the earliest postoperative, Patients and methods anteroposterior, supine pelvis radiograph of sufficient qual - The ASR system was used at our institution between Feb- ity) with reference to the inter-teardrop line using tools on ruary 2005 and March 2008. This study is a report of the the PACS workstation. Acetabular component orientation was results of our standard follow-up and imaging protocol. 79 also measured using Wrightington cup orientation software. hip arthroplasties using ASR components were performed This enables measurement of inclination and version, and cor- in 68 patients by 5 surgeons. 17 ASR resurfacing procedures rects for angular artifact due to the central X-ray beam offset were performed in 14 patients. 62 THRs were performed in from the hip (Derbyshire and Porter 2003, Derbyshire 2008). 54 patients using an ASR acetabular component, a matched 2 of the authors (HWJ and BD) tested the inter-observer and cobalt-chrome ASR XL head, and a Corail titanium hydroxy- intra-observer reliability of this software using standard sta- apatite-coated uncemented stem (DePuy, Leeds, UK). 14 head tistical techniques (Bland and Altman 1983, Ranstam et al. sizes were available, ranging from 39 mm to 63 mm in diam- 2000). Using these measurements, we designated acetabu- eter in 2-mm increments. For the purposes of comparative lar components as being within or outside Lewinnek’s “safe analysis, we designated femoral head component sizes in the zone” (anteversion 5–25 degrees, and inclination 30–50 range 39–49 mm as “small”, and 51–63 mm as “large”. degrees) (Lewinnek et al. 1978). The mean age of the 79 cases (56 males) at the time of Serial radiographs were compared to assess for peripros- surgery was 55 (30–76) years. The mean time from the pri- thetic osteolysis, lucent lines, bone loss, prosthesis migration, mary procedure to last follow-up or revision was 32 (14–51) and soft tissue swelling. We noted osteolysis and radiolucent months. No patients had died or were lost to follow-up. Indi- lines greater than 1 mm around the acetabular component in cations for surgery were primary osteoarthritis (OA) (n = 70), the zones of DeLee and Charnley (DeLee and Charnley 1976) OA secondary to dysplasia (n = 3), post trauma (n = 2), avas- as modified by Beaulé et al. (2004). Radiolucency around the cular necrosis (n = 2), and OA secondary to Perthes’ (n = 2). femoral stem was recorded using the zones of Amstutz et al. (2004) for resurfacing arthroplasty and of Gruen for stemmed Implants total hip arthroplasty. The median size of the femoral head component was 49 (43– Metal artifact-reduction MRI 57) mm). For the resurfacing group, the median size was 51 (45–57) mm and for the THR group it was 49 (43–55) mm. 31 All MR examinations were performed on a 1.5T machine cases had a “large” femoral head (51–63 mm) and 48 cases a (Siemens Symphony; Siemens Healthcare, Erlangen, Ger- “small” head (38–49 mm). many) using sequences adapted for metal artifact suppression. All images were reviewed by two musculoskeletal radiolo- Follow-up assessments gists (each had 5 years’ experience in reporting MRI findings The departmental policy at our institution is that all patients around MoM hip prostheses of various designs) and consen- who have undergone a MoM hip replacement should remain sus findings were recorded. under review and be assessed annually. The review involves Findings were categorized as: normal (Cahir et al. 2007), clinical assessment, radiological assessment, and a patient- abnormal and typical of an adverse reaction to metal debris based self-assessment questionnaire. The questionnaire (Fang et al. 2008, Pandit et al. 2008, Toms et al. 2009), or includes the Oxford hip score (Dawson et al. 1996) (OHS) abnormal but typical of a disease other than a metal-on-metal (where 12 = best score and 60 = worst score), an assessment of reaction—e.g. infection (Cahir et al. 2007). For those cases the patients’ satisfaction with the outcome of their hip replace- with characteristic findings of ARMD, they were further clas - ment (possible responses: Yes, No, Uncertain), and rating the sified into mild, moderate, or severe disease (Figures 1–3). result of their hip replacement on a visual analog scale (VAS) Mild changes constituted periprosthetic collections less than from 0 (unsatisfactory) to 10 (perfect). 5 cm in diameter, moderate comprised soft tissue masses of Patients who were scheduled for revision were asked to com- fluid collections greater than 5 cm in diameter, gluteal muscle plete a questionnaire before to revision surgery. All patients at atrophy or bone marrow edema and severe changes including our hospital with a MoM hip replacement are also routinely extension through deep fascia, tendon avulsion, bone marrow invited to undergo an MRI scan, even if they are asymptomatic replacement or fracture, or neurovascular involvement. This (provided there are no contraindications). grading system has been shown to be reliable (Anderson et al. 2011). Plain radiographs Histopathology Plain radiographs were assessed by one of the authors (HWJ) on a diagnostic PACS workstation. The acetabular implant ori- The tissue specimens in those patients who were revised, or entation, leg length, offset, and femoral component alignment underwent a biopsy, were assessed by a histopathologist expe- were measured. Two techniques were used for measurement rienced in evaluation of metal debris-related periprosthetic of acetabular component orientation. Acetabular inclination tissue reactions. Acta Orthopaedica 2011; 82 (3): 301–307 303 Figure 1. Mild adverse reaction to metal Figure 2. Moderate adverse reaction to metal Figure 3. Severe adverse reaction to metal debris. Sagittal T2W MR through the femo- debris. A sagittal T2W MR positioned just debris. Coronal T1W MR through the mid-cor- ral stem (S) of a Corail total hip replacement medial to the acetabular cup demonstrates onal plane of the femoral head (black arrows demonstrating mild periprosthetic disease. A moderate periprosthetic disease with a large indicate the medial wall of the acetabulum), small fluid-filled cavity (asterisk) surrounding cystic collection, demarcated by a low signal demonstrating severe periprosthetic disease the neck of the prosthesis is encapsulated by wall (black arrow), and filled with debris (white with bone marrow replacement in the acetab- a thick, ragged low-signal rim (white arrow). arrow) extending proximally in the line of the ular roof (white arrow). iliopsoas bursa. The relatively thick low signal wall and the debris are not typical of conven- tional iliopsoas bursae. Statistics had neck thinning, with resorption of the superior aspect of the Statistical analysis was performed using StatsDirect statis- femoral neck on the anteroposterior radiograph. There was no tical software version 2.7.7 (StatDirect Ltd., Altrincham, lysis, and no radiolucent lines around the stem of the femoral UK). Dichotomous variables were analyzed using Fisher’s resurfacing component. exact test. Continuous parametric data were analyzed using 52 of the 62 Corail stems appeared well fixed on the latest unpaired t-tests and non-parametric data were assessed with radiographs, and had no radiolucent lines in any of the 7 Gruen the Mann-Whitney U-test. zones. 10 hips had radiolucent lines in 1 or more Gruen zone. In 7 of these hips, a radiolucent line was seen only in Gruen zone 1. 3 hips also had lucent lines in Gruen zone 7. In all 10 hips, the Corail femoral component appeared well fixed from Results zones 2 to 6, and had not migrated. Plain radiographs MAR MRI examinations The mean cup inclination angle measured manually on digi- tal plain radiographs was 50 (36–74) degrees. The acetabular 75 patients had MAR MRI examinations (59 THR, 16 resur- orientation using Wrightington cup orientation software had a facing) at a mean of 31 (12–52) months after surgery. 4 hips mean inclination of 50 (34–75) degrees and mean anteversion were not scanned because 2 patients (3 hips) had a contrain- of 12 (2.3–39) degrees. dication to MRI (1 pacemaker and 1 spinal cord stimulator) The intra- and inter-observer reliabilities of Wrightington and 1 patient declined to be scanned as he was claustropho- cup orientation software for measuring ASR acetabular ori- bic (Table 1). 42 MRI scans were classified as consistent with entation were satisfactory. The intra-observer repeatability normal postoperative appearances (including seromas and for version was ± 0.55 degrees, and it was ± 0.49 degrees for atrophy of the short external rotators). 33 scans were consid- inclination. The inter-observer limits of agreement (95%) for ered to be abnormal, of which 3 were not thought to be typi- version were –1.9 to 6.6 degrees, and for inclination they were cal of an adverse reaction to metal debris, including: infection –2.8 to 2.4 degrees. All 79 acetabular components appeared to (n = 1), iliopsoas bursa (n = 1), and osteolysis (n = 1). 27 be well fixed, with good bone ongrowth on the last follow-up scans were considered to be abnormal and demonstrated fea- radiograph. None of the acetabular components had osteoly- tures consistent with an adverse reaction to metal debris. 5 sis or radiolucent lines greater than 1 mm in any of the three cases were considered to be mild, 18 were considered moder- Charnley DeLee zones. ate, and 4 were classified as severe. The typical appearance 16 of the 17 resurfacing femoral components had no evi- was of a fluid signal collection extending from, and surround - dence of loosening, migration, neck thinning, or radiolucent ing, the bearing that was demarcated by a very low-signal lines around the stem in any of Amstutz zones. One patient capsule, which was often ragged. Debris and a heterogeneous 304 Acta Orthopaedica 2011; 82 (3): 301–307 Table 1. Summary of metal artifact-reduction (MAR) MRI findings Table 3. Summary of revisions MAR MRI findings A B C D E F G H I J K A B C D E F G H I J 1 51 F P 34 30 47 58 20 + + ASR resurfacing 7 0 2 3 1 6 3 1 17 2 59 M P 40 40 49 49 24 + + Corail with XL head 3 60 M S 34 15 51 60 13 + + and ASR cup 35 3 3 15 3 21 0 3 62 4 55 F P 38 46 51 56 13 + – Total 42 3 5 18 4 27 3 4 79 5 57 F P 32 14 51 57 3 (+) + a a 6 67 F P+S 23 22 45 53 + + A Prosthesis 7 60 M P 16 57 49 56 11 – – B Normal 8 55 M P 29 55 47 53 7 + + C Abnormal, not ARDM D Mild ARMD Only conventional radiograph available; cup inclination measured E Moderate ARMD manually. F Severe ARMD A Case G All ARDM B Age H Unclassifiable C Sex I Not scanned D Indication for revision J Total P pain S squeaking E Time to revision (months) F OHS Table 2. Metal artifact-reduction MRI findings in relation to potential risk G Head size (mm) factors for metal debris-related reactions H Cup inclination I Cup version J MRI findings MRI classification – normal Not ARMD ARMD p-value (+) mild (A and B) (C1, C2, C3) + moderate K Histology (+ ARMD) Sex, F / M 13 / 35 9 / 18 0.4 Mean head size (mm) 50 49 0.2 Mean acetabular inclination (°) 50 51 0.4 Mean acetabular anteversion (°) 13 12 0.2 > 50 mm, small: < 50 mm) and acetabular orientation (incli- Head, small / large 26 / 22 19 / 8 0.2 nation, version, and location within or outside Lewinneck’s Cup in Lewinnek’s “safe zone”, “safe zone”(Lewinnek et al. 1978)) are summarized in Table yes / no 24 / 21 10 / 16 0.2 2. There was an increased risk of MRI-detected adverse reac- tion to metal debris with small femoral heads and cup orienta- signal were common findings within the fluid collections. tion outside Lewinnek’s “safe zone”, but this increase was not The patients with severe disease included 3 cases with bone statistically significant. marrow replacement around either the acetabulum (n = 1) or Implant survival the proximal femur (n = 2), and 1 patient had encasement of the sciatic nerve. The radiologists were not able to classify 3 At a mean follow-up of 32 (14–51) months, 8 revisions had of the MRI examinations and recommended follow-up with been performed in 8 patients (4 female) (Table 3). The cumu- repeat imaging after a further 6 months. There were 2 cases lative revision rate at 40 months with revision for any reason of atrophy of the gluteus medius and minimus but no cases of was 11% (95% CI: 4–18). gluteal avulsion. There were 7 cases of bone marrow edema in All the cases that were revised had an ASR acetabular com- the proximal femur without any other abnormal findings. The ponent with an XL head and a Corail femoral component. 6 significance of bone marrow edema in the proximal femur is revisions were performed for pain (1 of these patients also unknown, but may be part of the spectrum of normal MAR reported squeaking). MRI confirmed an adverse reaction to MRI appearances in the absence of other changes. These cases metal debris before revision in 4 of these patients. 2 patients were classified as normal postoperative appearances. had minimal pain (1 had a squeaking hip), but screening MRI In patients with normal MAR MRI findings or abnormali - revealed changes consistent with a moderate adverse reac- ties that were not an adverse reaction, the mean corrected cup tion to metal debris in one case and mild in the other case inclination angle was 50 (34–75) degrees, the mean anteversion that was squeaking. Both patients elected to undergo revision. was 13 (2.3–33) degrees, and mean head size was 50 (43–57) The plain radiographs were unremarkable, with no osteolysis mm. In those patients with an adverse reaction to metal debris, in 7 of these patients. In 1 patient, there were radiolucencies the mean cup inclination was 50 (37–60) degrees, mean ante- with the appearance of a neocortex in Gruen zones 1 and 7. At version was 12 (2.3–39) degrees, and mean head size was 49 the time of revision, the proximal stem was found to be loose (45–57) mm. The MAR MRI findings, and potential risk fac - with necrotic tissue, metal-stained debris, and fluid between tors associated with ARMD, including sex, head size (large: the stem and the bone. The stem was well fixed distally. This Acta Orthopaedica 2011; 82 (3): 301–307 305 patient underwent revision of both components. In the remain- Table 4. Patient-related outcome in relation to MAR MRI findings ing revisions, the femoral component was preserved and the acetabular component revised to an uncemented acetabular A B C D E F G component with a polyethylene or ceramic liner. The XL Normal 42 33 5 4 7.9 23 heads were exchanged to appropriate ceramic heads to match Abnormal (not ARMD) 3 3 0 0 8 25 the acetabular components. Mild ARMD 5 5 0 0 9 18 Moderate ARMD 18 14 1 2 7.6 21 Histopathology Severe ARMD 4 4 0 0 9.5 13 Unclassifiable 3 3 0 0 9 15 All 6 patients with a MAR MRI diagnosis of ARMD had his- Not scanned 4 4 0 0 9.5 12 topathological findings (in the tissue taken at the time of revi - All 79 66 6 6 8.2 21 sion) consistent with an ARMD. The findings were similar in A MRI classification the 6 cases: a fibrous capsular wall was seen, showing fibri - B No. of cases noid proliferation, with surface necrosis. A wide band of bland Patient satisfaction: C Yes necrosis was seen. Perivascular lymphocytic infiltration was D Doubtful seen with macrophages or histiocytes containing small metal E No particles. F VAS (0–10): 0 = unsatisfactory; 10 = perfect. G OHS: 12 = best; 60 = worst. The histology in the 2 patients who were revised for pain, but with normal MRI scans, revealed normal fibrous tissue with no evidence of inflammation or adverse reaction to metal debris. worst MAR MRI findings. One quarter of patients with a best possible OHS (12) had MRI-based evidence of ARMD. This Patient-related outcome suggests that even a policy of frequent clinical review would All hips were assessed with a hip questionnaire and an OHS not detect patients developing soft tissue complications until at mean 32 (14–51) months after the primary procedure. The extensive damage had occurred. It is unclear why there is assessment scores were those at the latest follow-up or last often no pain. assessment prior to revision. A comparison can be made with the problem of silent oste- 66 patients were satisfied with their hip replacements olysis, which is well documented in patients with uncemented whereas 7 were not, and 6 were doubtful. The mean overall acetabular components with a polyethylene liner (Hozack et al. “success” rating by patients of their hip replacements (on a 1996, Utting et al. 2008). It is generally accepted that patients VAS from 1 to 10) was 8. with such implants should be routinely assessed from plain The mean OHS in all patients—either at the latest follow- radiographs—even in the absence of symptoms—in order up or before revision—was 21. In the 8 patients who had a to detect osteolysis before it becomes extensive. The differ- revision, the mean OHS before revision was 37. In patients ence with metal-on-metal related pathology is that soft tissue without MRI-based evidence of an adverse reaction to metal pathology is of particular concern, and this is not visible on a debris, the mean OHS was 23, and in those with MRI-based plain radiograph. We believe it is preferable to detect ARMD evidence of ARMD it was 19 (p = 0.3) (Table 4). soft tissue damage and fluid-filled cavities at an early stage 51 patients had an OHS at latest follow-up of 20 or less, and before the damage becomes extensive and irreversible. Gram- 18 of these patients had MRI-based evidence of an adverse matopolous et al. (2009) reported that resurfacing prostheses reaction to metal debris. 26 patients had a “perfect” OHS of revised for pseudotumors have a poor outcome. This may 12 at latest follow-up, and 6 of these had MRI-based evidence well be because, in their series, patients only presented once of ARMD. they had become symptomatic and the disease had become extensive. Our experience with an earlier-generation 28-mm bearing MoM prosthesis, used in the 1990s, was that it func- tioned well for several years and then some patients suddenly Discussion presented with severe extensive soft tissue and bone necrosis, We found MRI-detected metal debris-related abnormalities which was often undetectable on plain radiographs (Nolan et in one third of patients with a modern MoM bearing. Previ- al. 2008). ous studies have concentrated on the MRI findings in patients The pattern of disease seen in our series on MRI shares investigated for painful prostheses (Boardman et al. 2006, similarities with those previously described for other pros- Fang et al. 2008, Pandit et al. 2008, Toms et al. 2008). theses, but there are also key differences. The pseudocysts One of our most concerning findings was that MRI- in this group of patients commonly contained debris result- based evidence of an adverse reation to metal debris does ing in heterogeneous signal patterns (Figure 2), whereas those not appear to correlate with symptoms. In fact, some of the described with other prostheses were typically homogeneous highest levels of satisfaction were in those patients with the fluid-filled cavities (Fang et al. 2008, Toms et al. 2008, 2009). 306 Acta Orthopaedica 2011; 82 (3): 301–307 Gluteal myositis, atrophy, and avulsion have been described with this implant be carefully followed up on a regular basis. on MR with metal-on-metal-associated disease (Toms et al. We believe that routine assessment of these implants should 2008) but these were not common findings in our series of include soft tissue imaging. patients. This may be because MRI has been performed on asymptomatic patients and patients earlier in their postopera- tive course than previously described. HWJ: Main author, data collection, data analysis, radiographic analysis. RM: Coordinated imaging and MRI scans, data collection and radiographic analy- A number of factors, including female sex, small prosthetic sis. JW: Clinical follow-up and manuscript preparation. NC: Clinical follow- head size, “poor” acetabular component orientation, and com- up. BD: Radiographic analysis. AT: MRI scanning, interpretation and clas- ponent design may contribute to ARMD. Hart et al. (2009) sification. JC: MRI scanning, interpretation and classification have shown that in a series of 16 failed large-head MoM pros- theses, 13 were positioned outside the Lewinnek “safe zone”. We have found MRI-based evidence of MoM disease in 41% No competing interests declared. of prostheses with “small heads” (38–49 mm) and cup orienta- tions outside Lewinneck’s “safe zone”. With “large heads” and a cup within the “safe zone”, the incidence of MoM disease Amstutz H C, Grigoris P. Metal on metal bearings in hip arthroplasty. Clin Orthop (Suppl) 1996; (329): S11-34. was still one fifth. Lewinnek’s safe zone originally related to Amstutz H C, Beaule P E, Dorey F J, Le Duff M J, Campbell P A, Gruen T dislocation risk in metal-on-polyethylene hip replacements. A. Metal-on-metal hybrid surface arthroplasty: two to six-year follow-up There have been no prospective studies of acetabular compo- study. J Bone Joint Surg (Am) 2004; 86 (1): 28-39. nent position to confirm whether there is actually a safe zone Anderson H, Toms A P, Cahir J G, Goodwin R W, Wimhurst J, Nolan J F. Grading the severity of soft tissue changes associated with metal-on-metal for prevention of ARMD. It is possible that all MoM prosthe- hip replacements: reliability of an MR grading system. Skeletal Radiol ses, in any orientation, would develop a reaction. 2011; 40 (3): 303-7. Our cumulative revision rate at 40 months of 11% is much Australian Orthopaedic Association National Joint Replacement Registry. higher than that for a conventional THR. In our series, the Annual Report. Adelaide: AOA; (2009). overall revision rate for ARMD was 8%. Other authors have Beaule P E, Dorey F J, LeDuff M, Gruen T, Amstutz H C. Risk factors affect- ing outcome of metal-on-metal surface arthroplasty of the hip. Clin Orthop reported a high early revision rate with the ASR. Langton et 2004; (418): 87-93. al. (2010) reported poor early results with the ASR system, Bland J M, Altman D G. Statistical methods for assessing agreement between with a revision rate for symptomatic ARMD of 3% at 3 years. two methods of clinical measurement. Lancet 1983; (i): 307-10. The revision rate in the subgroup of patients in their series Boardman D R, Middleton F R, Kavanagh T G. A benign psoas mass follow- with a total hip replacement (ASR cup, ASR XL head, and a ing metal-on-metal resurfacing of the hip. J Bone Joint Surg (Br) 2006; 88 (3): 402-4. Corail stem) rather than resurfacing was higher, at 6%. The Cahir J G, Toms A P, Marshall T J, Wimhurst J, Nolan J. CT and MRI of hip Australian National Joint Replacement Registry 2009 report arthroplasty. Clin Radiol 2007; 62 (12): 1163-71; discussion 72-3. (AOA NJRR 2009) found that the number of revisions per 100 Daniel J, Pynsent P B, McMinn D J. Metal-on-metal resurfacing of the hip observed component years for the ASR was 2.3 as compared in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg to 0.8 for the Birmingham Hip Resurfacing (BHR). (Br) 2004; 86 (2): 177-84. The design of the ASR acetabular component may be one Dawson J, Fitzpatrick R, Carr A, Murray D. Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg (Br) 1996; 78 of the reasons for the high failure rate. The cup comprises (2): 185-90. between 148 and 160 degrees of a sphere, whereas the BHR DeLee J G, Charnley J. Radiological demarcation of cemented sockets in total ranges from 158 to 166 degrees. This means that for any given hip replacement. Clin Orthop 1976; (121): 20-32. cup position, more of the ASR head is uncovered. This may Derbyshire B. Correction of acetabular cup orientation measurements for lead to increased edge loading and wear of the ASR cup. In a X-ray beam offset. Med Eng Phys 2008; 30 (9): 1119-26. comparative study of the ASR and BHR, Langton et al. (2009) Derbyshire B, Porter M L. An image analysis technique for the radiographic measurement of all-plastic acetabular cup orientation. Proceedings of the found that serum chromium and cobalt levels from ASR pros- 5th EBRA Meeting, Sheffield, Hip International 2003. theses were more strongly influenced by the effect of the ori - Fang C S, Harvie P, Gibbons C L, Whitwell D, Athanasou N A, Ostlere S. The entation of the acetabular component. There was an increase imaging spectrum of peri-articular inflammatory masses following metal- in metal ions at inclinations > 45° and anteversion angles of on-metal hip resurfacing. Skeletal Radiol 2008; 37 (8): 715-22. < 10° and > 20° with the ASR, whereas these levels were only Grammatopolous G, Pandit H, Kwon Y M, Gundle R, McLardy-Smith P, Beard D J, Murray D W, Gill H S. Hip resurfacings revised for inflamma - increased in the BHR group when the acetabular components tory pseudotumour have a poor outcome. J Bone Joint Surg (Br) 2009; 91 were implanted at inclinations > 55°. (8): 1019-24. We conclude that in our series of patients, the ASR Corail Hart A J, Sabah S, Henckel J, Lewis A, Cobb J, Sampson B, Mitchell A, Skin- THR had a high rate of early revision due to MoM-related soft ner J A. The painful metal-on-metal hip resurfacing. J Bone Joint Surg (Br) 2009; 91 (6): 738-44. tissue problems. Furthermore, the incidence of MRI-detected Heilpern G N, Shah N N, Fordyce M J. Birmingham hip resurfacing MoM disease was high in both ASR Corail THRs and ASR arthroplasty: a series of 110 consecutive hips with a minimum five-year resurfacings. 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Acta OrthopaedicaTaylor & Francis

Published: Jun 1, 2011

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