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CASE REPORT

Correlation between inclination of the acetabular component and metal ion levels in metal on metal hip resurfacing /  replacement

Khan A *,Ebreo D *,El Meligy *,Armstrong C*,Peter V *

Address for Correspondence

Lower Limb Arthroplasty Unit,
Department of Trauma & Orthopaedics,
The Royal Liverpool and Broadgreen University Hospital,
Prescot Street,
Liverpool L7 8XP (UK).

 

Abstract:

Aim:

Metal wear particles and metal ions are released from large diameter metal-on-metal
(MoM) hip articulations possibly resulting in local soft tissue toxicity. Periprosthetic
osteolysis from biological response to particulate wear debris results in implant loosening and failure.
Our aim was to determine whether steeply inclined acetabular components give rise to
higher metal ion concentrations.

Patients and methods:

Between April 2003 and June 2006, 22 patients had large diameter MoM THA or hip
resurfacings by a single Surgeon.12 male and 10 female patients. Average age was 56
years (44 - 69 years ).
Patients were divided into 2 groups. Group A, acetabular inclination angle > 45 degrees
(n=14) and Group B with an angle <45 degrees(n=8). Acetabular cup inclination was
measured using standard pelvic AP radiograph. Blood chromium(Cr) and serum cobalt
(Co) were measured at an average follow up of 3.2 years (2.4 to 5 years ).

Results:

Mean blood Cr level in Group A (236 nM/L) was significantly higher
( p = 0.04* ) than Group B ( 124 nM/L).Mean serum Co level in Group A
(387 nM/L) was significantly higher ( p = 0.02* ) than Group B ( 177 nM/L).

Conclusion:

Elevated metal ion levels in the blood is not a good thing as the long term systemic
consequences are not known and predict a poor outcome.
Recent literature suggests acetabular component positio influences bearing wear
contributing to metal ion release after MoM hip replacement. Our findings indicate that
acetabular components with inclination angle >45 degrees produce significantly higher
metal ion concentrations leading to a poor result.

J.Orthopaedics 2011;8(1)e16

Introduction

Metal-on-metal resurfacing hip replacement (1-3) is becoming an increasingly common
alternative to total hip replacement, particularly in younger patients.(4-8) It preserves femoral bone,has a lesser risk of dislocation and better wear characteristics than metal on polyethylene.(2,6)The early to mid-term published results have been encouraging. (4,9-12) There are, however, a number of concerns about the metal-on-metal bearing. Although its wear rate is low,(13) it still releases metal particles and ions into the body,(14,15) particularly cobalt and chromium since most metal on-metal bearings are made of a cobalt chromium alloy (CoCr). The diameter of a hip resurfacing bearing is more than that of most THR components and theoretically, if the lubrication conditions are not ideal, may increase the amount of metal ions released.(16) Several studies have reported increased serum concentrations of both Co and Cr after resurfacing/ hip replacement.(16-22) The long-term consequences of increased levels of these ions in the body are not known. High concentrationsof Co and Cr are toxic and are known to interfere with anumber of biological functions.(23-25) Willert et al (26) have described a soft tissuereaction thought to be related to metalsensitivity in patients with a metal-on-metal THR.
There have also been recent reports of soft-tissue reactions with resurfacing/
Hip replacement.(27,28) In the light of these concerns, it is important to examine factors
which may influence the release of metal ions after resurfacing hip replacement. It has
been reported that the position of the acetabular component will influence the bearing
wear of a resurfacing/ hip replacement.(29) Further, it has been observed that large amounts of metallosis are found during the revision of steeply-inclined acetabular components.(30,31) The relationship between wear and inclination angle in THR was examined by Brodner et al(17) who showed that there was considerable variation in the measurements of metal ions, but no clear relationship between the abduction angle and the level of metal ions. The relationship between level of activity and the concentration of metal ions was studied by Heisel et al(19 ) but no correlation was found between acute changes in activity level and the concentration of metal ions. Our aims in this study was to determine whether a steeply-inclined acetabular component would give rise to a higher concentration of metal ions

Patients and Methods

Between April 2003 and June 2006, 22 patients had large diameter MoM THA or hip
resurfacings by a single Surgeon.12 male and 10 female patients. Average age was 56
years (44 - 69 years ).Patients were divided into 2 groups. Group A, acetabular inclination angle > 45 degrees(n=14) and Group B with an angle <45 degrees(n=8). Acetabular cup inclination was measured using standard pelvic AP radiograph. Blood chromium(Cr) and serum cobalt (Co) were measured at an average follow up of 3.2 years (2.4 to 5 years ).These  patients did not have any other metal implants at the time of measurement. The reason for the minimum one-year post-operative sample time was to avoid the confounding factor of higher levels of wear during the run-in  period.(13,18)

The samples were obtained using an intravenous catheter. After the catheter had been
introduced, the metal needle was withdrawn and the first 5 ml of blood were discarded
to avoid possible contamination from the needle. A second 5 ml were collected using a
vaccum tube.Blood  levels of Co and serum levels of Cr were measured using inductive-coupled plasma mass spectrometry.The value of 45° was chosen based on the previous work of Brodneret al (17) who reported higher levels of metal ions in patients with an abduction angle greater than 45°.

Statistical analysis.

All statistical analyses were performed using Sigma plot software . The level of
significance was set at p ≤ 0.05.

Results

Mean blood Cr level in Group A (236 nM/L) was significantly higher ( p = 0.04* ) than Group B ( 124 nM/L).Mean serum Co level in Group A 387 nM/L) was significantly higher ( p = 0.02* ) than Group B ( 177 nM/L).

Discussion

Our findings indicate that steeply-inclined acetabular resurfacing components give rise to higher concentrations of metal ions. The reason for a very high concentration of metal
ions in some cases may be edge-loading which causes marked localized wear (30) and
gives rise to elevated levels of ions. (32) The more steeply-inclined the acetabular component, the more likely the occurrence of edge-loading. What is not clear from the literature is the relationship  between the level of metal ion and complications. It is clear, however, that a soft-tissue reaction to large quantities of  particulate debris can result in fluid or mass formation with subsequent destruction of soft tissues (19,28,33) as well as bone resorption leading to loosening of the implant or fracture of the femoral neck.(28) Our findings are in agreement with those of the present literature (34,35) who reported that inclination of the cup are related to the level of metal ions for patients implanted with the resurfacing/ hip replacement.The positioning of the acetabular component seems to be much more critical in metal-on-metal resurfacing hip replacement  than in conventional THR. This is in part because the acetabular component has a low profile to avoid impingement on the femoral neck, and in part because the wear associated with edge-loading has much more serious consequences.Edge-loading of metal-on-metal devices can disrupt the fluid film lubrication mechanism,(37) resulting in inadequate lubrication and increased wear.(38) Surgeons must therefore take great care to avoid edge-loading. This principle also applies to metal-on-metal THRs of larger diameter. The achievement of correct acetabular orientation isdifficult for a number of reasons.(36,39) First, the position of the pelvis on the  operating table is poorly defined and may alter. It is often very different from that perceived by the surgeon. Secondly, when the surgeon implants the acetabular component the estimate of its position relative to the patient is usually made by eye.This is likely to introduce errors. Thirdly, the appearance of the acetabulum at operation differs from that measured on the post-operative radiographs. When implanting the acetabular component, the surgeon considers the degree of opening to be the angle between the axis of the acetabular component and the sagittal plane, and anteversion the angle between the axis of the component and the coronal plane. When measuring acetabular inclination on radiographs, the angle between the axis of the acetabular component and the transverse plane is projected on to and measured in the coronal plane. Since the angles are measured in different ways they are profoundly different. If there is no acetabular component anteversion then that measured by the surgeon and that on the radiograph are the same, but as the anteversion increases the inclination measured on radiograph also increases, even though the inclination at surgery does not. At resurfacing, surgeons tend to antevert the acetabular component substantially to prevent impingement, and this will therefore appreciably increase the inclination of this component. In our study we have shown that high wear is very likely to occur in metal-on-metal resurfacings if the acetabular components are implanted steeply. The clinical message, therefore, is that surgeons should be to ensure that these are never implanted more than 45° open. In order to achieve this, surgeons should probably aim to implant them less than 45° open. There is a need for improvement in instrumentation and possibly navigation in order to assist surgeons to achieve this aim.(40)

Conclusion:

Elevated metal ion levels in the blood is not a good thing as the long term systemic
consequences are not known and predict a poor outcome.
Recent literature suggests acetabular component position influences bearing wear
contributing to metal ion release after MoM hip replacement. Our findings indicate that
acetabular components with inclination angle >45 degrees produce significantly higher
metal ion concentrations leading to a poor result.

References

1. Amstutz HC, Grigoris P. Metal on metal bearings in hip arthroplasty. Clin Orthop
   1996;329(Suppl):11-34.
2. McMinn D, Treacy R, Lin K, Pynsent P. Metal on metal surface replacement of the
    hip: experience of the McMinn prosthesis. Clin Orthop 1996;329(Suppl):89-98.
3. McMinn D, Daniel J. History and modern concepts in surface replacement. Proc
    Inst Mech Eng [H] 2006;220:239-51.
4. Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip
    in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg [Br]
    2004;86-B:177-84.
5. Amstutz HC, Su EP, Le DUff MJ. Surface arthroplasty in young patients with hip
   arthritis secondary to childhood disorders. Orthop Clin North Am 2005;36:223-30.
6. Hing C, Back D, Shimmin A. Hip resurfacing indications, results, and conclusions.
    Instr Course Lect 2007;56:171-8.
7. Steffen RT, Pandit HP, Palan J, et al. The five-year results of the Birmingham Hip
    Resurfacing arthroplasty: an independent series. J Bone Joint Surg [Br] 2008;90-
    B:436-41.
8. Pollard TC, Baker RP, Eastaugh-Waring SJ, Bannister GC. Treatment of the
    young active patient with osteoarthritis of the hip: a five- to seven-year comparison of
    hybrid total hip arthroplasty and metal-on-metal resurfacing. J Bone Joint Surg [Br]
    2006;88-B:592-600.
9. Amstutz HC, Beaulé PE, Dorey FJ, et al. Metal-on-metal hybrid surface
    arthroplasty:two to six-year follow-up study. J Bone Joint Surg [Am] 2004;86-A:28-
    39.
10. Back DL, Dalziel R, Young D, Shimmin A. Early results of primary Birmingham
      hip resurfacings: an independent prospective study of the first 230 hips. J Bone Joint
      Surg [Br] 2005;87-B:324-9.
11. Treacy RB, McBryde CW, Pynsent PB. Birmingham hip resurfacing arthroplasty: a
       minimum follow-up of five years. J Bone Joint Surg [Br] 2005;87-B:167-70.
12. De Smet KA. Belgium experience with metal-on-metal surface arthroplasty. Orthop
      Clin North Am 2005;36:203-13.
13. Chan FW, Bobyn JD, Medley JB, Krygier JJ, Tanzer M. Wear and lubrication of
     metal-on-metal hip implants. Clin Orthop 1999;369:10-24.
14. Brodner W, Bitzan P, Meisinger V, et al. Elevated serum cobalt with metal-onmetal
      articulating surfaces. J Bone Joint Surg [Br] 1997;79-B:316-21.
15. Daniel J, Ziaee H, Pradhan C, Pynsent PB, McMinn DJ. Blood and urine metal
      ionlevels in young and active patients after Birmingham hip resurfacing arthroplasty:
     fouryearresults of prospective longitudinal study. J Bone Joint Surg [Br] 2007;89-
     B:169-73.
16. Clarke MT, Lee PT, Arora A, Villar RN. Levels of metal ions after small- and
    largediameter metal-on-metal hip arthroplasty. J Bone Joint Surg [Br] 2003;85-B:913-17.
17. Brodner W, Grübl A, Jankovsky R, et al. Cup inclination and serum concentration
    of cobalt and chromium after metal-on-metal total hip arthroplasty. J Arthroplasty
    2004;19:66-70.
18. Back DL, Young DA, Shimmin AJ. How do serum cobalt and chromium levels
     change after metal-on-metal hip resurfacing? Clin Orthop 2005;438:177-81.
19. Heisel C, Silva M, Skipor AK, Jacobs JJ, Schmalzried TP. The relationship
    between activity and ions in patients with metal-on-metal bearing hip prostheses. J
    Bone Joint Surg [Am] 2005;87-A:781-7.
20. Daniel J, Ziaee H, Salama A, Pradhan C, McMinn DJ. The effect of the diameter
   of metal-on-metal bearings on systemic exposure to cobalt and chromium. J
   Bone Joint Surg [Br] 2006;88-B:443-8.
21. Rasquinha VJ, Ranawat CS, Weiskopf J, et al. Serum metal levels and bearing
      surfaces in total hip arthroplasty. J Arthroplasty 2006;21:47-52.
22. Witzleb WC, Ziegler J, Krummenauer F, Neumeister V, Guenther KP. Exposure
      to chromium, cobalt and molybdenum from metal-on-metal total hip replacement
      and hip resurfacing arthroplasty. Acta Orthop 2006;77:697-705.
23. Anissian L, Stark A, Dahlstrand H, et al. Cobalt ions influence proliferation and
      function of human osteoblast-like cells. Acta Orthop Scand 2002;73:369-74.
24. Keegan GM, Learmonth ID, Case CP. Orthopaedic metals and their potential
      toxicity in the arthroplasty patient: a review of current knowledge and future
      strategies.
      J Bone Joint Surg [Br] 2007;89-B:567-73.
25. 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;88-B:449-54.
26. Willert HG, Buchhorn GH, Fayyazi A, et al. Metal-on-metal bearings and
      hypersensitivity in patients with artificial hip joints: a clinical and
      histomorphological
     study. J Bone Joint Surg [Am] 2005;87-A:28-36.
27. Boardman DR, Middleton FR, Kavanagh TG. A benign psoas mass following
      metal-on-metal resurfacing of the hip. J Bone Joint Surg [Br] 2006;88-B:402-4.
28. Pandit H, Glyn-Jones S, McLardy-Smith P, et al. Pseudotumours associated
      with metal-on-metal hip resurfacings. J Bone Joint Surg [Br] 2008;90-B:847-51.
29. Liu F, Jin Z, Roberts P, Grigoris P. Importance of head diameter, clearance, and
     cup wall thickness in elastohydrodynamic lubrication analysis of metal-on-metal
     hip resurfacing prostheses. Proc Inst Mech Eng [H] 2006;220:695-704.
30. Campbell P, Beaulé PE, Ebramzadeh E, et al. A study of implant failure in
     metal-on-metal surface arthroplasties. Clin Orthop 2006;453:35-46.
31. De Haan R, Campbell PA, Su EP, De Smet KA. Revision of metal-on-metal
     resurfacing arthroplasty of the hip: the influence of malpositioning of the  
     components. J
     Bone Joint Surg [Br] 2008;90-B:1158-63.
32. Zahiri CA, Schmalzried TP, Szuszczewicz ES, Amstutz HC. Assessing activity
     in joint replacement patients. J Arthroplasty 1998;13:890-5.
33. Kretzer JP, Heisel C. A new method to quantitatively detect ultra low wear rates
     of metal-metal bearings in a simulator. 6th Combined Meeting of the Orthopaedic
     Research Societies, Honolulu, 2007 (abstract).
34. Madan S, Jowett RL, Goodwin MI. Recurrent intrapelvic cyst complicating
      metal-on-metal cemented total hip arthroplasty. Arch Orthop Trauma Surg
      2000;120:508-10.
35. Vendittoli PA, Mottard S, Roy AG, Dupont C, Lavigne M. 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;89-B:441-8.
36. Murray DW. The definition and measurement of acetabular orientation. J Bone
      Joint Surg [Br] 1993;75-B:228-32.
37. Barrett AR, Davies BL, Gomes MP, et al. Computer-assisted hip resurfacing
      surgery using the acrobot navigation system. Proc Inst Mech Eng [H] 2007;221:773-
      85.
38. Udofia IJ, Jin ZM. Elastohydrodynamic lubrication analysis of metal-on-metal
      hip-resurfacing prostheses. J Biomech 2003;36:537-44.
39. Milosev I, Trebse R, Kovac S, Cör A, Campbell P. Dissociation of the metal
      inlay from the polyethylene liner in an uncemented threaded cup. Arch Orthop
      Trauma Surg 2005;125:134-41.
40. Cobb JP, Kannan V, Brust K, Thevendran G. Navigation reduces the learning
     curve in resurfacing total hip arthroplasty. Clin Orthop 2007;463:90-7.

This is a peer reviewed paper 

Please cite as :Khan A: Correlation between inclination of the acetabular component and metal ion levels in metal on metal hip resurfacing /  replacement

J.Orthopaedics 2011;8(1)e16

URL: http://www.jortho.org/2011/8/1/e16

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