Should metal hypersensitivity skin-patch testing be included in the usual preoperative total joint arthroplasty work-up?
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Nickel sensitivity of greatest concern
I do not include metal sensitivity testing in the preoperative evaluation of patients undergoing total joint arthroplasty. Given the increased use of ceramic heads, most total hips implanted in the U.S. today are nickel-free. The issue is more about total and unicompartmental knees, most of which have a cobalt-chromium-nickel alloy femoral component. Further, there is a higher rate of “unexplained dissatisfaction” with total knee arthroplasty.
A distinction should be made between the results of metal sensitivity testing and a periprosthetic immune or hypersensitivity reaction as the cause of a loose or poorly functioning total knee. There is no consensus on the diagnostic criteria for immune failure of a TKA. Immune sensitization to metals is increasing in the general population, likely due to increased environmental exposure. The estimated prevalence of metal sensitivity in the general population is 10% to 15% as diagnosed by SPT, with sensitivity to nickel being the most common (14%). SPT is of little prognostic utility in the setting of TKA, as SPT-positive patients with TKA have no difference in outcome at 5 years compared to a matched cohort of SPT-negative patients. A meta-analysis found metal sensitivity in 25% of patients with a well-functioning TKA, which led many to conclude that such tests are not predictive of any clinical result.
In response to the limitations of SPT in TKA, use of the LTT has increased. However, its validity for the diagnosis of immune failure of TKA has not been established; the prevalence of a positive LTT in patients with TJA who have well-functioning implants has not been reported. An allergic reaction to a joint implant should be apparent in periprosthetic tissue. Willert and colleagues described a deep tissue reaction that is uniquely associated with cobalt-based alloys, which is consistent with a cell-mediated type-IV (delayed) hypersensitivity reaction: an aseptic, lymphocyte-dominated vasculitis-associated lesion, subsequently referred to as ALVAL. In a recent study of TKA with a positive LTT for nickel and persistent pain and stiffness, the histopathology did not demonstrate a significant immune reaction.
- Bravo D, et al. J Arthroplasty. 2016;doi:10.1016/j.arth.2016.01.024.
- Granchi D, et al. J Bone Joint Surg Br. 2012;doi:10.1302/0301-620X.94B8.28135.
- Willert HG, et al. J Bone Joint Surg Am. 2005;doi:10.2106/JBJS.A.02039pp.
- Yang S, et al. J Bone Joint Surg Am. In press.
Thomas P. Schmalzried, MD, is medical director of Joint Replacement Institute in Los Angeles, and Joint Reconstruction Section Editor of Orthopedics Today.
Disclosure: Schmalzried reports he receives royalties from DePuy Synthes.
No current support for skin-patch testing
The question of an “allergic reaction” to the biomaterials used in total hip and total knee implants has been raised by patients and physicians for decades.
Scientifically, this “allergic reaction” is described by immunologists as delayed-type hypersensitivity (DTH), which implies a “sensitization” phase. “Hypersensitivity” refers to an undesirable and at times damaging reaction produced by the normal immune system. Type 4 hypersensitivity, also referred to as cell-mediated or DTH, is most consistent with described implant hypersensitivity reactions around hip and knee arthroplasty prostheses.
Virtually all recent literature has described a hypersensitivity response, initially termed by Willert and colleagues as ALVAL, most commonly described with metal-on-metal articulations. Mechanistically, it was felt that cobalt and chrome particles complexed with host proteins to create haptens that were highly immunogenic. With the decline in the use of metal-on-metal articulations in total hip arthroplasty, the concern for hypersensitivity reactions has decreased significantly, but there is still the concern related to taper corrosion of the numerous modular taper junctions in both THA and TKA.
If we accept that such an “allergic” reaction can occur, is there currently any way to predict which patients are susceptible? Although skin testing for sensitivity to particulate biomaterials is commercially available, there are significant concerns regarding its accuracy, and thus its utility as a screening tool. The haptenic potential of metal on open-testing dermal contact is likely quite different from that in a closed periprosthetic in vivo environment. A meta-analysis by Granchi and colleagues in 2012 found hypersensitivity testing was unable to discriminate between stable and failed TJA. There is also recent evidence that SPT had no correlation with patient outcomes after TKA.
In summary, there is no current information to support routine SPT for all patients undergoing THA or TKA. There is limited support for preoperative testing of “high-risk” patients, defined as patients with a documented history of serious metal allergy, or revision arthroplasty candidates with unexplained pain following careful history and physical exam.
- Kuby J. Immunology. 2nd ed. New York, NY: W.H. Freeman; 1994.
- Middleton S, et al. Bone Joint J. 2016;doi:10.1302/0301-620X.98B4.36767.
- Pinson ML, et al. Ann Allergy Asthma Immunol. 2014;doi:10.1302/0301-620X.98B4.36767.
- Watters TS, et al. Am J Clin Pathol. 2010;doi:10.1309/AJCPLTNEUAH8XI4W.
William A. Jiranek, MD, FACS, is professor and vice chair of the department of orthopaedic surgery at Duke University School of Medicine, in Durham, North Carolina.
Disclosure: Jiranek reports he is a consultant for DePuy Synthes Orthopaedics and receives royalties for certain hip and knee products from DePuy Synthes Orthopaedics; and is a member of the board of directors for the American Association of Hip and Knee Surgeons and The Hip Society.
Not ready for prime time
In the past decade, there have been increasing concerns about metal hypersensitivity-associated failure in TJA. While hypersensitivity reactions in the skin to metal exposure are common in the general population (up to 15% for nickel), the incidence of failure due to this hypersensitivity reaction in TJA is less clear and the source of controversy. The most well-accepted and available test for metal hypersensitivity is SPT. Unfortunately, clinical studies in THA and TKA have not demonstrated increased rates of complications or reoperations in patients with positive SPT vs. a negative test. Importantly, there does seem to be a correlation with patient-reported metal allergies and decreased functional outcomes regardless of SPT results. These inferior outcomes also occur in patients with a higher number of self-reported allergies suggesting that self-reported allergies may correlate to a currently unknown mental-health or physical source of risk for adverse outcomes after TJA.
Given the current literature, there should not be any recommendation for routine SPT prior to TJA because there is little evidence to support adverse outcomes in patients that test positive. However, for patients with self-reported metal allergies, using a hypoallergenic implant may be worthwhile because it may at the very least improve the mental aspects of recovery and make the patient feel their surgeon has listened to their concerns. Additionally, worse outcomes have been shown in patients with self-reported metal allergies regardless of the results of SPT, and eliminating the potential for a metal hypersensitivity associated failure might be worthwhile despite the lack of evidence.
- Lachiewicz PF, et al. J Am Acad Orthop Surg. 2016;doi:10.5435/JAAOS-D-14-00290.
- Nam D, et al. J Arthroplasty. 2016;doi:10.1016/j.arth.2016.02.016.
Benjamin F. Ricciardi, MD, is assistant professor of orthopedic surgery in the department of orthopedic surgery, Center for Musculoskeletal Research, University of Rochester School of Medicine, in Rochester, New York.
Disclosure: Ricciardi reports no relevant financial disclosures.