, Volume 472, Issue 2, pp 543-554
Date: 30 Jul 2013

What Causes Unexplained Pain in Patients With Metal-on metal Hip Devices? A Retrieval, Histologic, and Imaging Analysis

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Topic
Hip

Abstract

Background

Adverse tissue reactions associated with metal-on-metal (MOM) hips are common in resurfacing and total hip arthroplasty (THA) designs. The etiology of these reactions in painful, well-positioned arthroplasties is inconsistently described.

Questions/purposes

The purposes of this study were to compare the (1) articular wear rates; (2) histologic findings; (3) synovial response on MRI; and (4) graded intraoperative tissue damage between well-positioned, MOM hips revised for unexplained pain and MOM hips revised for other reasons and to (5) determine whether the presence of a taper junction on a MOM articulation affects these four parameters in unexplained pain.

Methods

We retrospectively studied 88 patients (94 hips) who had undergone revision of either a hip resurfacing or a large-head (> 36 mm) THA. Thirty-five hips revised for unexplained pain were compared with a control group of 59 hips revised for other causes. Articular wear was measured using three-dimensional contactless metrology and histologic analysis was performed using the aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) score. Preoperative MRI was performed on 57 patients to determine synovial volumes and thicknesses. Tissue damage was graded from intraoperative reports.

Results

Articular wear rates in the unexplained pain group were lower than in the control group (median 2.6 μm/year versus 12.8 μm/year, p < 0.001). Sixty-six percent of patients in the unexplained pain group had histologic confirmation of ALVAL compared with 19% in the control group (p < 0.001). The synovial thickness on MRI was higher in the unexplained pain group (p = 0.04) and was highly predictive of ALVAL. Severe intraoperative tissue damage was noted in more cases in the unexplained pain group (p = 0.01). There were no differences in articular wear, histology, MRI, and tissue damage between resurfacings and THAs revised for unexplained pain.

Conclusions

Unexplained pain in patients with well-positioned MOM hips warrants further investigation with MRI to look for features predictive of ALVAL. Tissue destruction in these cases does not appear to be related to high bearing wear or the presence of a taper.

Level of Evidence

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

One or more of the authors certifies that he (EPS) or she, or a member of his or her immediate family, has or may receive payments or benefits, during the study period, an amount less than USD 100,000 from Smith & Nephew (Memphis, TN, USA). One or more of the authors certifies that he (TW) or she, or a member of his or her immediate family, has or may receive payments or benefits, during the study period, an amount less than USD 10,000, from Mathys ABG (Bettlach, Switzerland), and an amount USD 10,000 to USD 100,000, from Exactech (Great Neck, NY, USA). One or more of the authors certifies that he or she (HGP), or a member of his or her immediate family, has or may receive payments or benefits, during the study period, an amount less than USD 10,000, from Regentis Biomaterials Ltd (Or-Akiva, Israel), and receives institutional research support from General Electric Healthcare (Waukesha, WI, USA). One or more of the authors certifies that he (DEP) or she, or a member of his or her immediate family, has or may receive payments or benefits, during the study period, an amount less than USD 100,000 from MAKO (Fort Lauderdale, FL, USA) and an amount less than USD 10,000 from Stryker (Mahwah, NJ, USA).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.
Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.