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Pseudotumors in Association with Well-Functioning Metal-on-Metal Hip ProsthesesA Case-Control Study Using Three-Dimensional Computed Tomography and Magnetic Resonance Imaging
Alister J. Hart, MA, MD, FRCSG(Orth)1; Keshthra Satchithananda, BDS, FDSRCS, MBBS, FRCS, FRCR1; Alexander D. Liddle, MBBS, MRCS1; Shiraz A. Sabah, MBBS, BSc1; Donald McRobbie, PhD1; Johann Henckel, MBBS, MRCS1; Justin P. Cobb, BMBCh, FRCS, MCh1; John A. Skinner, FRCS(Orth)2; Adam W. Mitchell, MBBS, FRCS, FRCR1
1 Departments of Orthopaedic Surgery (A.J.H, A.D.L., S.A.S., J.H., and J.P.C.) and Radiology (K.S., D.M., and A.W.M.), Charing Cross Hospital (Imperial College Healthcare NHS Trust and Imperial College London), Fulham Palace Road, London W6 8RF, United Kingdom. E-mail address for A.J. Hart: a.hart@imperial.ac.uk
2 Royal National Orthopaedic Hospital (University College London), Brockley Hill, Middlesex, London HA7 4LP, United Kingdom
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Investigation performed at Charing Cross Hospital and Imperial College, London, United Kingdom

A commentary by Joshua J. Jacobs, MD, is linked to the online version of this article at jbjs.org.



Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

Copyright © 2012 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2012 Feb 15;94(4):317-325. doi: 10.2106/JBJS.J.01508
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Abstract

Introduction: 

Many papers have been published recently on the subject of pseudotumors surrounding metal-on-metal hip resurfacing and replacement prostheses. These pseudotumors are sterile, inflammatory lesions within the periprosthetic tissues and have been variously termed masses, cysts, bursae, collections, or aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL). The prevalence of pseudotumors in patients with a well-functioning metal-on-metal hip prosthesis is not well known. The purpose of this study was to quantify the prevalence of pseudotumors adjacent to well-functioning and painful metal-on-metal hip prostheses, to characterize these lesions with use of magnetic resonance imaging, and to assess the relationship between their presence and acetabular cup position with use of three-dimensional computed tomography.

Methods: 

We performed a case-control study to compare the magnetic resonance imaging findings of patients with a well-functioning unilateral metal-on-metal hip prosthesis and patients with a painful prosthesis (defined by either revision arthroplasty performed because of unexplained pain or an Oxford hip score of <30 of 48 possible points). Thirty patients with a painful hip prosthesis and twenty-eight controls with a well-functioning prosthesis were recruited consecutively. All patients also underwent computed tomography to assess the position of the acetabular component.

Results: 

Thirty-four patients were diagnosed with a pseudotumor. However, the prevalence of pseudotumors in patients with a painful hip (seventeen of thirty, 57%) was not significantly different from the prevalence in the control group (seventeen of twenty-eight, 61%). No objective differences in pseudotumor characteristics between the groups were identified. No clear association between the presence of a pseudotumor and acetabular component position was identified. The Oxford hip score in the group with a painful hip (mean, 20.2; 95% confidence interval [CI], 12.7 to 45.8) was poorer than that in the control group (mean, 41.2; 95% CI, 18.5 to 45.8; p ≤ 0.0001).

Conclusions: 

A periprosthetic cystic pseudotumor was diagnosed commonly (in thirty-four [59%] of the entire study cohort) with use of metal artifact reduction sequence (MARS) magnetic resonance imaging in this series of patients with a metal-on-metal hip prosthesis. The prevalence of pseudotumors was similar in patients with a well-functioning hip prosthesis and patients with a painful hip. Pseudotumors were also diagnosed commonly in patients with a well-positioned acetabular component. Although magnetic resonance imaging is useful for surgical planning, the presence of a cystic pseudotumor may not necessarily indicate the need for revision arthroplasty. Further correlation of clinical and imaging data is needed to determine the natural history of pseudotumors to guide clinical practice.

Level of Evidence: 

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Vanessa Starks
    Posted on March 22, 2012
    matching of study subjects
    Medical Student, Morehouse School of Medicine

    Hart and colleagues provide an excellent evaluation of painful prostheses by using the Oxford hip score which can be used in place of the Harris hip score without losing any valuable patient information[1]. An additional point can be made on this topic. The logistic regression model used determined differences between the two groups with regard to prevalence of pseudotumor, age at the time of primary arthroplasty, and time since the last arthroplasty, but not for the type of implant. Of note, the painful group consisted of 6 Durom implant recipients, 5 ASR, and 1 Biomet implant recipient who were not matched in the well-functioning control group. Pseudotumors were detected in patients with these implants but there was no asymptomatic group of patients with these implants with which to compare pseudotumor detection, prevalence, or pseudotumor relation to the acetabular component position. Pseudotumor will continue to be an important issue in understanding metal-on-metal hip arthroplasty complications and failures. In the future, adequate matching of study subjects on type of implant will further clarify outcome differences. REFERENCE: [1]Parsons NR, DeSouza RM, Oni T, Achten J, Krikler SJ, Costa ML. A comparison of Harris and Oxford hip scores for assessing outcome after resurfacing arthroplasty of the hip: can the patient tell us everything we need to know. Hip Int. 2010 Oct-Dec;20(4):453-9

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