The effect of operative factors on outlier ion levels in patients with metal-on-metal hip arthroplasties.
Cobalt and chromium metal ion release occur through mechanical wear and galvanic corrosion. The volumetric wear rates of modern MoM articulations are in the range of 0.13 to 5 [mm.sup.3] per [10.sup.6] cycles, which is significantly lower when compared to conventional metal-on-polyethylene articulations. (16) Metal debris is small (less than 50 nm per particle), and although volumetric wear rates are decreased, the surface area exposed to various bodily surfaces is substantially higher. (5,17,18) This large surface area of cobalt and chromium ions are subsequently released into the circulation and have been found in the serum, blood, and urine of patients. (19-26) Hip simulator, retrieval, and clinical studies have identified technical and prosthetic risk factors for increased systemic metal ion values. For example, the introduction of the Morse taper in the Durom prosthesis (Zimmer, Warsaw, Indiana) led to significantly increased metal ion values forcing the investigators' recommendation against the use of a modular junction in MoM total hip replacement. (27) Acetabular abduction angles above 50[degrees] in most studies have demonstrated higher metal ion release. (28-30) Hip simulator studies and tribology suggest that by maintaining all manufacturing parameters constant, increasing femoral head diameter leads to improved lubrication and decreased circulating metal ions (16); however, the clinical data have been conflicting. (19,31-36)
MoM hip implants continue to be successful alternatives to conventional bearings in younger patients with hip arthritis. A subset of patients have unusually high circulating levels of cobalt and chromium ions. Given the lack of consensus regarding the etiology of increased whole blood cobalt and chromium ions following MoM arthroplasty and the increasing the potential for cellular toxicity, the purpose of the current study was to explore the potential patient and surgical factors that could lead to abnormally high concentrations of whole blood metal ion values.
Materials and Methods
This study represents a cohort of 761 patients who underwent unilateral MoM THA or hip resurfacing from April 2002 to October 2008 at a single institution. Whole blood cobalt and chromium metal ion values, as well as clinical outcomes, were prospectively recorded. We retrospectively reviewed our database to identify patients who had outlier metal ion values, defined as those who had ion levels greater than or equal to three-fold the median values. This resulted in cobalt and chromium concentrations of greater than or equal to 10 [micro]g/L and greater than or equal to 5 [micro]g/L, respectively. The project was approved by our Institutional Review Board (IRB) prior to recruitment of patients. At the 6-week follow-up clinic visit, patients provided informed consent for the study, including analysis of their whole blood metal ion values. The inclusion criteria were patients greater than 18 years of age, no previous metallic implants or chronic medical illness. Patients with limited mobility and abnormal pre-operative screening renal function (serum creatinine range, 55 to 110 [micro]mol/L) were excluded from the study.
Of the 36 outlier patients, two were lost to follow-up. Both were unable to be contacted by telephone and did not present for clinical and radiographic follow-up examinations. Thirty-four patients (4.5%) had complete clinical, radiographic, and blood metal ion values for inclusion in the final analysis. This included 20 patients who underwent THA (20 hips) and 14 patients (14 hips) who had hip resurfacing. All total hip prostheses were implanted without cement. The Articular Surface Replacement[TM] (ASR[TM], DePuy, Warsaw, Indiana) was the implant used for all patients in the resurfacing group. In the MoM THA group, 28 mm femoral heads were used for three patients (Metasul, Zimmer, Warsaw, Indiana), while the remaining femoral head components used were from DePuy (Ultamet[TM], DePuy, Warsaw, Indiana). Metasul[R] and Ultamet[TM] femoral heads have similar manufacturing properties. They are both forged, wrought, high-carbon cobalt-chrome alloys, with radial clearances of 75 [micro]m and 40 to 80 [micro]m, respectively.
The study cohort consisted of 17 females and 17 males, whose mean age at the time of arthroplasty was 60 years (range, 48 to 75 years). The mean follow-up was 2 years (range, 6 months to 3 years). The mean femoral head diameters in patients who had outlier metal ions was 37 mm (range, 28 to 44 mm) and 51 mm (range, 46 to 55 mm) for THA and hip resurfacing procedures, respectively. The diagnosis was osteoarthritis (OA) in 32 (94%) patients, osteonecrosis in one (3%) patient, and hip dysplasia in one (3%) patient. One patient, a 54-year-old male, initially underwent hip resurfacing for OA and required conversion to a THA 32 days later, due to a postoperative femoral neck fracture. The patient was included in the THA group. He was converted to a hybrid implant with a 51 mm diameter femoral head and retained his 58 mm acetabular cup.
Clinical outcome scores were performed prospectively using the Harris hip score (HHS) (37) and the University of California Los Angeles (UCLA) activity scores. (38) Serial radiographs and ion levels were also analyzed at regular intervals. Laboratory personnel involved in data analysis were blinded to the study protocol.
Blood Collection and Metal Ion Analysis
Cobalt and chromium ion levels were analyzed from whole blood. Blood sampling was performed using a technique aimed at minimizing metal ion contamination, as previously described. (19,39) At a mean follow-up of 2 years (range, 6 months to 3 years), the median values for cobalt and chromium ions were 13.7 [micro]g/L (range, 4.98 to 105.0 [micro]g/L) and 6.0 [micro]g/L (range, 0.405 to 38.00 [micro]g/L), respectively (Fig. 1). Outlier metal ion levels were calculated from 761 patients (1317 blood samples) and included values of cobalt greater than or equal to 10 [micro]g/L or chromium greater than or equal to 5 [micro]g/L. In 14 samples (41%), both cobalt and chromium ion values were above 10 [micro]g/L and 5 [micro]g/L, respectively and, thus, were considered outliers. In 26 samples (76%), the cobalt but not chromium values were in the outlier range. Finally, in 22 samples (65%), the chromium, and not cobalt metal ion values, were in the outlier range (Table 1).
Acetabular inclination and anteversion were determined using the Einzel-Bild-Roentgen-Analyse software (EBRA, University of Innsbruck, Innsbruck, Austria). (40) This was performed by one of the investigators (SG) on anteroposterior pelvic digital radiographs.
The HHS and UCLA scores were symmetrically distributed, and differences were calculated using ANOVA, followed by a protected Fisher's least significant difference (PLSD). Correlations in the outlier metal ion values and the various parameters (femoral head diameter, acetabular cup size) were performed using the Spearman's rank correlation coefficient. The metal ion values were asymmetrically distributed and therefore a non-parametric equivalent of one-way analysis of variance (ANOVA) was used, the Kruskal-Wallis test. Statistical analysis software used was StatView (SAS Institute, Cary, North Carolina). Significance was set using p values less than 0.05.
The clinical outcome scores (HHS and UCLA activity scores) in patients with outlier metal ion values were similar to those that were in the 28 to 36 mm and 40 to 44 mm femoral head THA groups and patients with hip resurfacing procedures (Table 1).
We observed similar mean acetabular inclination angles when comparing patients with outlier metal ion values to those in the 28 to 36 mm femoral head (p = 0.44), 40 to 44 mm femoral head (p = 0.06), and hip resurfacing groups (p = 0.87). There was no difference in mean acetabular anteversion between patients in the outlier metal ion group and those that received 28 to 36 mm and 40 to 44 mm femoral head THAs, p = 0.06 and p = 0.75, respectively. However, we observed a higher (p = 0.039) mean acetabular anteversion in the outlier metal ion group, compared to those patients who underwent hip resurfacing procedures (mean 17.8[degrees] versus 13.0[degrees]) (Table 1).
[FIGURE 1 OMITTED]
The femoral head diameter was not correlated with the concentration of whole blood cobalt ([R.sup.2] = 0.004, p = 0.23) or chromium ([R.sup.2] = 0.001, p = 0.73). Similarly, there was no correlation with the size of the acetabular cup with cobalt ([R.sup.2] = 0.0198, p = 0.45) or chromium ([R.sup.2] = 0.00947, p = 0.21) metal ion values (Table 2). There was also no correlation between the age of the patient and the level of cobalt ([R.sup.2] = 0.083, p = 0.67) and chromium ([R.sup.2] = -0.276, p = 0.11). Anteversion did not correlate with cobalt ([R.sup.2] = 0.086, p = 0.62) and chromium ([R.sup.2] = -0.002, p = 0.99) ion levels. Inclination also did not correlate with cobalt ion levels ([R.sup.2] = -0.180, p = 0.86). However, inclination correlated with chromium levels ([R.sup.2] = 0.560, p = 0.001) in outlier patients (Table 2). Finally, there were no differences between the levels of cobalt (14.2 vs. 13.7 [micro]g/L, p = 0.99) and chromium (7.8 vs 4.9 [micro]g/L, p = 0.14) in outlier male and female patients. Cobalt ion levels were higher (p = 0.03) in patients with THA, compared to those who underwent hip resurfacing procedures (19.4 vs. 10.5 [micro]g/L), while there was no difference (p = 0.12) in chromium concentrations (4.53 vs. 6.92 [micro]g/L) (Fig. 2).
[FIGURE 2 OMITTED]
Metal ion release in MoM articulations occurs from corrosion and wear at the bearing surface. (41,42) Cobalt and chromium are subsequently released into the circulation and have led to concern, because these are biologically active ions that are chronically elevated in blood and tissues of patients.11,43 Recent literature has established the trend of metal ion values over time, as well as identifying patient and surgical factors that lead to elevated ion levels. (9,10,30,31,33,44) However, there is a paucity of data identifying reasons why patients develop extremely high concentrations of metal ions after hip arthroplasty with MoM bearings. The aim of the present study was to determine if any patient or surgical factors could account for outlier concentrations of cobalt and chromium metal ions from a cohort of 761 patients with MoM hip arthroplasty implants.
There are several limitations to this study. Our project was performed in a retrospective manner, despite the data being prospectively collected. Therefore, our study might not account for all known confounders, even if a multivariate analysis was performed. Another limitation is that we are using cobalt and chromium as markers for poorly functioning implants. Our study, as well as what is published in the literature, cannot include as part of its findings that in a given prosthesis there is no substantial contribution from localized corrosion, or other patient factors that could account for higher concentrations of metal ions. (45,46) Even in a well-functioning, metal-on-polyethylene articulation, it is estimated that cobalt and chromium ions still increase five-times the amount found in normal controls. (47) We also did not collect pre-operative metal ion values, which would have been useful for comparison to the absolute magnitude difference in patients with outlier metal ion values. With those acknowledgements, our results should still be considered valid, since all of our patients had no other sources of metal ions in the body, had normal renal function, and were not limited in mobility, all of which could have falsely elevated the results. We were not able to assess for impingement as a potential source of increased concentration of metal ion values, which has proven to be a source of increased levels of cobalt and chromium ions in several studies. (48-50)
Our study group contained outlier patients with levels of cobalt and chromium between 4.7 to 5.9, and 8- to 15.4-times the levels in non-outlier patients, respectively. Despite this increased metal ion load, we did not demonstrate any difference in the HHS or UCLA activity scores. The data from the literature is contradictory and has included variable sampling and statistical methods. Desy and and colleagues (44) demonstrated a negative correlation with cobalt and functional outcome scores and an inverse relationship with chromium and UCLA activity scores. In another 7-year follow-up study, the investigators reported good-to-excellent HHS scores despite higher levels of circulating chromium ions. (26) However, cobalt levels were not reported, and the peak chromium was 1.76 [micro]g/L at a mean of 3-years. Vendittoli and coworkers (27) reported 1-year whole blood mean cobalt (2.2 [micro]g/L) and chromium (1.3 [micro]g/L) ion levels and found no correlation with UCLA or Western Ontario McMaster OA index (WOMAC) scores. Similarly, De Haan and associates (30) found no relationship between metal ions and UCLA scores, even in patients with outlier metal ion values. The previous studies did not exclusively evaluate patients with cobalt and chromium ions over 10 [micro]g/L and 5.0 [micro]g/L, respectively, making comparison with the literature difficult.
The surgical variables in our study included analyses of femoral head diameter, as well as acetabular cup size, inclination, and abduction angles. At a mean 2-year follow-up, we could only account for a difference in acetabular anteversion in patients in the hip resurfacing and outlier group (13.0[degrees] vs. 17.8[degrees]). However, the anteversion in the resurfacing group may not be clinically relevant, since it was found in the published acceptable range.51 We found a positive correlation with outlier chromium ion levels and acetabular inclination, consistent with previous studies demonstrating that acetabular abduction angles above 50[degrees] result in higher metal ion release. (28-30) It is unclear why cobalt was not correlated, but may be related to our clinically acceptable mean acetabular inclination angle (48[degrees]). The acetabular abduction was also comparable to the measurement in the comparative groups. Similarly, hip simulator studies have shown that by increasing femoral head diameters, wear rates are decreased. (16,52-54) This occurs because manufacturers can improved diametric bearing clearances only as femoral head diameters increase.55 The assumption is that in clinical practice MoM bearings are operating with mixed-film lubrication; however, clinical studies regarding wear and femoral head diameters have been inconsistent with in vitro studies. (19,31,34) Furthermore, it has been shown that acetabular cup deformation, which depends on patient weight, quality of the underlying bone, and diametric bearing clearance, can lead to poor wear performance. (56,57)
We only found a correlation with cobalt outlier metal ion values and the type of arthroplasty (THA vs. hip resurfacing). This is similar to other studies published and may, in part, be due to the tribological advantage of larger head use in the resurfacing group. Garbuz and colleagues, (34) in a prospectively randomized trial, compared 73 patients with MoM large-head THA and hip resurfacing at a mean follow-up of 1.1 years. They had serum metal ion values on 30 patients and found a 10-fold and 2.6-fold increase in cobalt and chromium metal ions, respectively, following large-head THA. Comparison to our study is difficult because there is a lack of an outlier metal ion group and an inferior sampling method. (58) Some studies have failed to show any difference in metal ion values comparing 28-mm femoral heads and hip resurfacing procedures, (33,36) while a similar study design demonstrated a decrease in cobalt and chromium ion values. (32) Study comparison continues to be difficult, due to of lack of consensus with regard to sampling methods, manufacturing variables, and statistical analysis. (59)
The results of this study suggest that metal ion release after THA and resurfacing procedures is multifactorial and includes patient, surgical, and manufacturing parameters. Prospective studies that can better control for each variable are warranted due to insufficient data to conclude on the optimal bearing couple.
The authors would like to thank Maricar Alminia and Laura Desrosiers for their assistance in the administration of the questionnaires, recording of the clinical data, and collection of the blood samples.
John Antouiou, M.D., is a consultant for Depuy, Johnson & Johnson. None of the other authors have a financial or proprietary interest in the subject matter or materials discussed, including, but not limited to, employment, consultancies, stock ownership, honoraria, and paid expert testimony.
(1.) Mai K, Verioti C, Ezzet KA, et al. Incidence of 'squeaking' after ceramic-on-ceramic total hip arthroplasty. Clin Orthop Relat Res. 2010 Feb;468(2):413-7.
(2.) Jarrett CA, Ranawat AS, Bruzzone M, et al. The squeaking hip: a phenomenon of ceramic-on-ceramic total hip arthroplasty. J Bone Joint Surg Am. 2009 Jun;91(6):1344-9.
(3.) Sharma V, Ranawat AS, Rasquinha VJ, et al. Revision total hip arthroplasty for ceramic head fracture: a long-term follow-up. J Arthroplasty. 2010 Apr;25(3):342-7.
(4.) Rhoads DP, Baker KC, Israel R, et al. Fracture of an alumina femoral head used in ceramic-on-ceramic total hip arthroplasty. J Arthroplasty. 2008 Dec;23(8):1239.e25-30; Epub 2008 Apr 11.
(5.) Chan FW, Bobyn JD, Medley JB, et al. The Otto Aufranc Award. Wear and lubrication of metal-on-metal hip implants. Clin Orthop Relat Res. 1999 Dec;(369):10-24.
(6.) 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 Jan;87(1):28-36.
(7.) Engh CA Jr, Ho H, Engh CA. Metal-on-metal hip arthroplasty: does early clinical outcome justify the chance of an adverse local tissue reaction? Clin Orthop Relat Res. 2010 Feb;468(2):406-12.
(8.) Pandit H, Glyn-Jones S, McLardy-Smith P, et al. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg Br. 2008 Jul;90(7):847-51.
(9.) Prosser GH, Yates PJ, Wood DJ, et al. Outcome of primary resurfacing hip replacement: evaluation of risk factors for early revision. Acta Orthopaedica. 2010 Feb;81(1):66-71.
(10.) Corten K, MacDonald SJ. Hip resurfacing data from national joint registries: what do they tell us? What do they not tell us? Clin Orthop Relat Res. 2010 Feb;468(2):351-7.
(11.) Huk OL, Catelas I, Mwale F, et al. Induction of apoptosis and necrosis by metal ions in vitro. J Arthroplasty. 2004 Dec;19(8 Suppl 3):84-7.
(12.) Hallab NJ, Anderson S, Caicedo M, et al. Immune responses correlate with serum-metal in metal-on-metal hip arthroplasty. J Arthroplasty. 2004 Dec;19(8 Suppl 3):88-93.
(13.) Hart AJ, Skinner JA, Winship P, et al. Circulating levels of cobalt and chromium from metal-on-metal hip replacement are associated with CD8+ T-cell lymphopenia. J Bone Joint Surg Br. 2009 Jun;91(6):835-42.
(14.) Amstutz HC, Le Duff MJ, Campbell PA, et al. Clinical and radiographic results of metal-on-metal hip resurfacing with a minimum ten-year follow-up. J Bone Joint Surg Am. 2010 Nov;92(16):2663-71.
(15.) Girard J, Bocquet D, Autissier G, et al. Metal-on-metal hip arthroplasty in patients thirty years of age or younger. J Bone Joint Surg Am. 2010 Oct 20;92(14):2419-26.
(16.) Chan FW, Bobyn JD, Medley JB, et al. Engineering issues and wear performance of metal on metal hip implants. Clin Orthop Relat Res. 1996 Dec;(333):96-107.
(17.) Doorn PF, Campbell PA, Worrall J, et al. Metal wear particle characterization from metal on metal total hip replacements: transmission electron microscopy study of periprosthetic tissues and isolated particles. J Biomed Mater Res. 1998 Oct;42(1):103-11.
(18.) Campbell P, Shen FW, McKellop H. Biologic and tribologic considerations of alternative bearing surfaces. Clin Orthop Relat Res. 2004 Jan;(418):98-111.
(19.) Antoniou J, Zukor DJ, Mwale F, et al. Metal ion levels in the blood of patients after hip resurfacing: a comparison between twenty-eight and thirty-six-millimeter-head metal-on-metal prostheses. J Bone Joint Surg Am. 2008 Aug;90 (Suppl) 3 142-8.
(20.) Daniel J, Ziaee H, Pradhan C, et al. Blood and urine metal ion levels in young and active patients after Birmingham hip resurfacing arthroplasty: four-year results of a prospective longitudinal study. J Bone Joint Surg Br. 2007 Feb;89(2):169 73.
(21.) Daniel J, Ziaee H, Pradhan C, et al. Renal clearance of cobalt in relation to the use of metal-on-metal bearings in hip arthroplasty. J Bone Joint Surg Am. 2010 Apr;92(4):840-5.
(22.) Jacobs JJ, Skipor AK, Doorn PF, et al. Cobalt and chromium concentrations in patients with metal on metal total hip replacements. Clin Orthop Relat Res. 1996 Aug;329(Suppl):S256-63.
(23.) Skipor AK, Campbell PA, Patterson LM, et al. Serum and urine metal levels in patients with metal-on-metal surface arthroplasty. J Mater Sci Mater Med. 2002 Dec;13(12):1227 34.
(24.) Vendittoli PA, Mottard S, Roy AG, et al. Chromium and cobalt ion release following the Durom high carbon content, forged metal-on-metal surface replacement of the hip. J Bone Joint Surg Br. 2007 Apr;89(4):441-8.
(25.) Walter LR, Marel E, Harbury R, et al. Distribution of chromium and cobalt ions in various blood fractions after resurfacing hip arthroplasty. J Arthroplasty. 2008 Sep;23(6):814-21.
(26.) Maezawa K, Nozawa M, Yuasa T, et al. Seven years of chronological changes of serum chromium levels after Metasul metal-on-metal total hip arthroplasty. J Arthroplasty. 2010 Dec;25(8):1196-200.
(27.) Vendittoli PA, Amzica T, Roy AG, et al. Metal ion release with large-diameter metal-on-metal hip arthroplasty. J Arthroplasty. 2011 Feb;26(2):282-8; Epub 2010 Mar 4.
(28.) Khan M, Kuiper JH, Richardson JB. The exercise-related rise in plasma cobalt levels after metal-on-metal hip resurfacing arthroplasty. J Bone Joint Surg Br. 2008 Sep;90(9):1152-7.
(29.) Brodner W, Grubl A, Jankovsky R, et al. Cup inclination and serum concentration of cobalt and chromium after metal-on-metal total hip arthroplasty. J Arthroplasty. 2004 Dec;19(8 Suppl 3):66-70.
(30.) De Haan R, Pattyn C, Gill HS, et al. Correlation between inclination of the acetabular component and metal ion levels in metal-on-metal hip resurfacing replacement. J Bone Joint Surg Br. 2008 Oct;90(10):1291-7.
(31.) Bernstein M, Walsh A, Petit A, et al. Femoral head size does not affect ion values in metal-on-metal total hips. Clin Orthop Relat Res. 2010 Oct 21; Epub ahead of print.
(32.) Clarke MT, Lee PT, Arora A, et al. Levels of metal ions after small- and large-diameter metal-on-metal hip arthroplasty. J Bone Joint Surg Br. 2003 Aug;85(6):913-7.
(33.) Daniel J, Ziaee H, Salama A, et al. The effect of the diameter of metal-on-metal bearings on systemic exposure to cobalt and chromium. J Bone Joint Surg Br. 2006 Apr;88(4):443-8.
(34.) Garbuz DS, Tanzer M, Greidanus NV, et al. The John Charnley Award: metal-on-metal hip resurfacing versus large-diameter head metal-on-metal total hip arthroplasty: a randomized clinical trial. Clin Orthop Relat Res. 2010 Feb;468(2):318-25.
(35.) Langton DJ, Jameson SS, Joyce TJ, et al. The effect of component size and orientation on the concentrations of metal ions after resurfacing arthroplasty of the hip. J Bone Joint Surg Br. 2008 Sep;90(9):1143-51.
(36.) Vendittoli PA, Roy A, Mottard S, et al. Metal ion release from bearing wear and corrosion with 28 mm and large-diameter metal-on-metal bearing articulations: a follow-up study. J Bone Joint Surg Br. Jan;92(1):12-9.
(37.) Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am. 1969 Jun;51(4):737-55.
(38.) Zahiri CA, Schmalzried TP, Szuszczewicz ES, et al. Assessing activity in joint replacement patients. J Arthroplasty. 1998 Dec;13(8):890-5.
(39.) Case CP, Ellis L, Turner JC, et al. Development of a routine method for the determination of trace metals in whole blood by magnetic sector inductively coupled plasma mass spectrometry with particular relevance to patients with total hip and knee arthroplasty. Clin Chem. 2001 Feb;47(2):275-80.
(40.) Krismer M, Bauer R, Tschupik J, et al. EBRA: a method to measure migration of acetabular components. J Biomech. 1995 Oct;28(10):1225-36.
(41.) Urban RM, Jacobs JJ, Gilbert JL, et al. Migration of corrosion products from modular hip prostheses. Particle microanalysis and histopathological findings. J Bone Joint Surg Am. 1994 Sep;76(9):1345-59.
(42.) Gilbert JL, Buckley CA, Jacobs JJ. In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling. Journal of biomedical materials research. 1993 Dec;27(12):1533-44.
(43.) Hart AJ, Hester T, Sinclair K, et al. The association between metal ions from hip resurfacing and reduced T-cell counts. J Bone Joint Surg Br. 2006 Apr;88(4):449-54.
(44.) Desy NM, Bergeron SG, Petit A, et al. Surgical variables influence metal ion levels after hip resurfacing. Clin Orthop Relat Res. 2010 Oct 23; Epub ahead of print.
(45.) Urban RM, Jacobs JJ, Tomlinson MJ, et al. Dissemination of wear particles to the liver, spleen, and abdominal lymph nodes of patients with hip or knee replacement. J Bone Joint Surg Am. 2000 Apr;82(4):457-76.
(46.) Langkamer VG, Case CP, Heap P, et al. Systemic distribution of wear debris after hip replacement. A cause for concern? J Bone Joint Surg Br. 1992 Nov;74(6):831-9.
(47.) Jacobs JJ, Skipor AK, Patterson LM, et al. Metal release in patients who have had a primary total hip arthroplasty. A prospective, controlled, longitudinal study. J Bone Joint Surg Am. 1998 Oct;80(10):1447-58.
(48.) Iida H, Kaneda E, Takada H, et al. Metallosis due to impingement between the socket and the femoral neck in a metal-on-metal bearing total hip prosthesis. A case report. J Bone Joint Surg Am. 1999 Mar;81(3):400-3.
(49.) Onda K, Nagoya S, Kaya M, et al. Cup-neck impingement due to the malposition of the implant as a possible mechanism for metallosis in metal-on-metal total hip arthroplasty. Orthopedics. 2008 Apr;31(4):396.
(50.) Williams D, Royle M, Norton M. Metal-on-metal hip resurfacing: the effect of cup position and component size on range of motion to impingement. J Arthroplasty. 2009 Jan;24(1):144-51.
(51.) Lewinnek GE, Lewis JL, Tarr R, et al. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am. 1978 Mar;60(2):217-20.
(52.) Goldsmith AA, Dowson D, Isaac GH, et al. A comparative joint simulator study of the wear of metal-on-metal and alternative material combinations in hip replacements. Proceedings of the Institution of Mechanical Engineers Part H, Journal of engineering in medicine. 2000 214(1):39-47.
(53.) Udofia IJ, Jin ZM. Elastohydrodynamic lubrication analysis of metal-on-metal hip-resurfacing prostheses. Journal of biomechanics. 2003 Apr;36(4):537-44.
(54.) Smith SL, Dowson D, Goldsmith AA. The effect of femoral head diameter upon lubrication and wear of metal-onmetal total hip replacements. Proc Inst Mech Eng H. 2001 215(2):161-70.
(55.) Khan M, Kuiper JH, Richardson JB. Can cobalt levels estimate in-vivo wear of metal-on-metal bearings used in hip arthroplasty? Proc Inst Mech Eng H. 2007 Nov;221(8):929-42.
(56.) Liu F, Jin Z, Roberts P, et al. Effect of bearing geometry and structure support on transient elastohydrodynamic lubrication of metal-on-metal hip implants. J Biomech. 2007;40(6):1340 9.
(57.) Liu F, Jin ZM, Hirt F, et al. Effect of wear of bearing surfaces on elastohydrodynamic lubrication of metal-on-metal hip implants. Proc Inst Mech Eng H. 2005 Sep;219(5):319-28.
(58.) Daniel J, Ziaee H, Pynsent PB, et al. The validity of serum levels as a surrogate measure of systemic exposure to metal ions in hip replacement. J Bone Joint Surg Br. 2007 Jun;89(6):736-41.
(59.) MacDonald SJ, Brodner W, Jacobs JJ. A consensus paper on metal ions in metal-on-metal hip arthroplasties. J Arthroplasty. 2004 Dec;19(8 Suppl 3):12-6.
Mitchell Bernstein, M.D., is from the Division of Orthopaedic Surgery, McGill University Health Centre, Montreal, Quebec; Sumit Gupta, M.D., is from the Division of Pediatric Orthopaedics, Department of Surgery, Alberta Children's Hospital, Calgary, Alberta; Alain Petit, Ph.D., is from Lady Davis Institute for Medical Research, SMBD-Jewish General Hospital, Montreal, Quebec; David J. Zukor, M.D., Olga L. Huk, M.D., M.Sc., and John Antoniou, M.D., Ph.D., are from the Division of Orthopaedic Surgery, McGill University Health Centre, Montreal, Quebec, and Lady Davis Institute for Medical Research, SMBD-Jewish General Hospital, Montreal, Quebec, Canada.
Correspondence: John Antoniou, M.D., Ph.D., Room E-003, Department of Orthopaedics, SMBD-Jewish General Hospital, 3755, Chemin de la Cote Ste-Catherine, Montreal, Quebec H3T 1E2, Canada; email@example.com.
Table 1 Results Comparing Patients with Outlier Metal Ion Values and the Different Groups with Non-Outlier metal Ion Levels THA, 28 and 36 mm Functional Outcome ([dagger]) Outliers Femoral Heads Harris hip score 85.5 (14.0) 86.2 (12.8) (standard deviation) UCLA activity score 6.6 (1.47) 5.95 (1.64) (standard deviation) Metal Ion ([double dagger]) Cobalt ([micro]g/L) 13.7 2.3 Chromium ([micro]g/L) 6 0.75 Component Position ([section]) Acetabular inclination (range) 47.5[degrees] 45.9 (36-58) (32-67) Acetabular anteversion (range) 17.8[degrees] 25.6 (5-47) (4-43) THA, 40 and 44 mm Hip Functional Outcome ([dagger]) Femoral Heads Resurfacing Harris hip score 88.3 (11.6) 90.0 (10.0) (standard deviation) UCLA activity score 6.34 (1.70) 7.6 (2.00) (standard deviation) Metal Ion ([double dagger]) Cobalt ([micro]g/L) 2.9 2.9 Chromium ([micro]g/L) 0.39 0.56 Component Position ([section]) Acetabular inclination (range) 42.6 (31-57) 47.8 (37-59) Acetabular anteversion (range) 18.5 (5-36) 13.0 (1-37) ([parallel]) THA, total hip arthroplasty; ([dagger]) These values are given as the mean at 2 years; ([double dagger]) these values are given as the median at 2 years; ([section])these values are given as the mean at 2 years; ([parallel]) p = 0.039 when compared to patients in the outlier metal ion group. Table 2 Effect of Patient or Surgical Factors with Outlier metal Ion Values * Parameter Mean (Range) Cobalt Cup Diameter, mm 56 (50-62) p = 0.45, [R.sup.2] = 0.0198 Head Diameter, mm 43 (28-55) p = 0.23, [R.sup.2] = 0.004 Age, years 59.5 (48-75) p = 0.67, [R.sup.2] = 0.083 Acetabular anteversion, 17.8 (3.5-43) p = 0.62, degrees [R.sup.2] = 0.086 Acetabular inclination, 46.4 (8.4-6.7) p = 0.86, degrees [R.sup.2] = -0.180 Parameter Chromium Cup Diameter, mm p = 0.21, [R.sup.2] = 0.00947 Head Diameter, mm p = 0.73, [R.sup.2] = 0.001 Age, years p = 0.11, [R.sup.2] = -0.276 Acetabular anteversion, p = 0.99, degrees [R.sup.2] = -0.002 Acetabular inclination, p = 0.001, degrees [R.sup.2] = 0.56 * Spearman's rank correlation coefficient.
|Printer friendly Cite/link Email Feedback|
|Author:||Bernstein, Mitchell; Gupta, Sumit; Petit, Alain; Zukor, David J.; Huk, Olga L.; Antoniou, John|
|Publication:||Bulletin of the NYU Hospital for Joint Diseases|
|Date:||Jan 1, 2011|
|Previous Article:||Is there a new learning curve with transition to a new resurfacing system?|
|Next Article:||Narrowed indications improve outcomes for hip resurfacing arthroplasty.|