Occasional reports of joint replacement implant failure because of an apparent allergy to one of the metals in the device have appeared in the orthopedic literature ever since metal implants were used. (1-3) It is now recognized that a small number of patients will suffer from a form of allergy or hypersensitivity to constituents of the metal-on-metal bearings even in the absence of high wear or a known metal sensitivity (4-6). The histological features of the reaction characterizing the joint tissues from these hypersensitive patients are different from the classical text-book form of Type 4 DTH. (7) For this reason, the term ALVAL (aseptic lymphocytic vasculitis associated lesions) has been coined to describe the histological features associated with an allergy-like reaction in the joint tissues. (8) It should be noted that some pathologists object to the inclusion of the “vasculitis” part of this new name and vasculitis in the strict sense of the word is not a prominent feature of the lesions.

The characteristic histological features in the periprosthetic tissues are infiltrates of lymphocytes, often with plasma cells, arranged perivascularly or in dense aggregates. In severe cases, there may be a wide necrotic tidemark between the tissue edge and the lymphocytes which are then arranged in a broad band at the back of the tissue section. These infiltrates appear in the absence of infection or mechanical causes for pain. It is important to note that lymphocytes can be present in relatively large numbers in response to excessive wear debris and the reason for their presence is unclear (9,10).

Diagnosing metal sensitivity can be difficult, and it may be hard to differentiate it from a reaction to excessive wear or to infection if an organism is not cultured from the tissue or joint fluid. There is a wide variety of clinical presentations of metal sensitivity; typically the patients report ongoing pain or discomfort, typically in the groin, often accompanied over time with an effusion which may progress to form an enlarged fluid hernia or a groin mass. If all possible causes for the patient’s pain can be eliminated by imaging or hematological testing, a diagnosis of metal sensitivity should be entertained and if confirmed, the cobalt chromium bearings should be removed to avoid ongoing soft tissue damage. (11) The number of revisions performed to remove cobalt chromium bearings because of a metal allergy is unknown, but it is thought to be a relatively rare complication.

Skin Sensitivity and Hip Sensitivity

Approximately 10–15% of the general population has a skin sensitivity to metal, nickel being the most common sensitizer, followed by cobalt and chromium. (5) There is concern, therefore, that patients with a skin sensitivity will also have an adverse reaction to a cobalt chromium hip replacement although there is little actual evidence to support this concern. It should be noted that the FDA lists skin sensitivity as a contraindication to metal-on-metal hip resurfacing.

A small retrospective survey of patients with a metal-on-metal hip resurfacing

arthroplasties was carried out at one center which performs a large number of hip resurfacings (the Joint Replacement Institute, St Vincent’s Hospital, Los Angeles ). Patients were asked about reactivity to jewelry (type of jewelry involved, the metal involved, and the nature of the reaction). One hundred seventy-eight patients responded (142 male 35 female) and 21 (5.6%) reported they had a skin problem, mostly to stainless steel (which contains a small amount of nickel) or “cheap” jewelry in the form of rashes, redness and itching. Of those 21, 11 were male and 13 were female, but since most of the overall patient cohort was male, the proportion of females with skin reactions was relatively higher. However, regardless of their problems with jewelry, none of these patients had any problems with their hip replacement. Unfortunately, patch tests that can demonstrate skin sensitivity are not reliable to predict if a problem will occur in the hip after a cobalt chromium implant is inserted. Newer blood tests as “lymphocyte aggregation” tests are also not yet reliable, but research into better screening tests for metal sensitivity is ongoing.

In my Orthopaedic Practice

The definitive diagnose of metalsensitivity only can be given after examination by an experienced anatomopathologist of thetissues surrounding the prosthesis. On x-rays these soft tissue and bonychanges can be seen as progressive necknarrowing (white arrows), osteolytic lines (bone that is absent) around the stem of the resurfacing head (yellow arrows) and osteolysis even behind the cup (black arrows).

Taking in account that most of the metal sensitivity cases are seen after a time frame of more then 3 years, the incidence in my patient series is 6/1346.( Number ofpatients with longer follow up then 3 years (3-9y))

This incidence ofapproximate 1/200 should even be equated to be higher in females (1/60) because the only allergies are seen in females, who are only 1/3 of the whole resurfacing group. Timely revision should be performed to avoid progressive local tissue damage.

With special thanks to Pat Campbell PhD Orthopaedic Hospital/UCLA, Los Angeles, CA USA

Pat Campbell, Ph.D. Director, Implant Retrieval Lab. J. Vernon Luck, Sr., MD Orthopaedic Research Center , UCLA/ Orthopedic Hospital

Scott D. Nelson MD, Chief of Pathology Santa Monica UCLA/ Orthopedic Hospital

References 1. Evans EM, Freeman MAR, Miller AJ, and Vernon-Roberts B: Metal sensitivity as a cause of bone necrosis and loosening of the prosthesis in total joint replacement. J Bone Joint Surg 56B:626-642, 1974.

2. Vernon-Roberts B, and Freeman MAR: Morphological and Analytical Studies of the Tissues Adjacent to Joint Prostheses: Investigations Into the Causes of Loosening of Prostheses. IN Schaldach M Hofmann D (eds). Advances in Hip and Knee Joint Technology, Springer-Verlag, New York, 1976, 148-186.

3. Deutman R, Mulder THJ, Brian R, and Nater JP: Metal sensitivity before and after total hip arthroplasty. J Bone Joint Surg 59A:862-865, 1977.

4. Gawkrodger DJ: Metal sensitivities and orthopaedic implants revisited: the potential for metal allergy with the new metal-on-metal joint prostheses. Br J Dermatol. 148:1089-1093., 2003.

5. Hallab N, Merritt K, and Jacobs JJ: Metal sensitivity in patients with orthopaedic implants. J Bone Joint Surg 83A:428-436., 2001.

6. Willert H, Buchorn G, Fayaayazi A, and Lohmann C: Histopathological changes around metal/metal joints indicate delayed type hypersensitivity. Preliminary results of 14 cases. Osteologie 9:2-16, 2000.

7. Davies AP, Willert HG, Campbell PA, Learmonth ID, and Case CP: An Unusual Lymphocytic Perivascular Infiltration in Tissues Around Contemporary Metal-on-Metal Joint Replacements. J Bone Joint Surg 87:18-27, 2005.

8. Willert H-G, Buchhorn GH, Dipl-Ing, Fayyazi A, Flury R, Windler M, Koster G, and Lohmann CH: Metal-on-metal bearings and hypersensitivity in patients with artificial hip joints. A clinical and histomorphological study. J Bone Joint Surg 87:28-36, 2005.

9. Campbell P, Mirra J, Doorn P, Mills B, Alim R, and Catelas I: Histopathology of Metal- on-Metal Hip Joint Tissues. IN Rieker C, Oberholzer S, Wyss U (eds). World Tribology Forum in Arthroplasty, Hans Huber, Gottingen, 2000, 167-180.

10. Campbell P, Beaule P, Ebramzadeh E, Le Duff M, De Smet K, Lu Z, and Amstutz H: A study of implant failure in metal-on-metal surface arthroplasties. Clin Orthop 453:35-46, 2006.

11. Campbell P, Shimmin A, Walter L, and Solomon M: Metal Sensitivity as a Cause of Groin Pain in Metal-on-Metal Hip Resurfacing. J Arthroplasty in press:2007.