Metal-on-Metal: Letters to the Editor (Spine)

[Harrison]

To the Editor:

Re: Sasso RC, Foulk DM, Hahn M. Prospective, randomized trial of metal–on–metal artificial lumbar disc replacement: initial results for treatment of discogenic pain. Spine 2008;33:123–31.

I read carefully the interesting and important prospective comparative study by Sasso et al regarding the initial results with an artificial lumbar disc (Flexicore) with a metal-on-metal articulation compared with standard circumferential fusion with a follow-up of 2 years. The authors concluded that the Flexicore artificial arthroplasty compared very favorably to circumferential fusion for the treatment of lumbar degenerative disc disease. I would like to congratulate the authors for their study and ask some essential questions:

1. Did the authors perform any histologic examination in the retrievals from the revision surgery? It would be interesting to show any granulomas.
2. The authors reported 2% hardware migration. Although the follow-up of 2 years is relative short I am wondering if the authors measured any focal osteolysis at the endplate-implant interface in the cases with migration and in the other cases.
3. Did the authors see any skin or other allergic reactions following implantation?
4. Did the authors measure metal ions in the blood of the patients who received the Flexicore?

The above posed questions to the authors were based on observations made in the last few years in the metal-on-metal total hip arthroplasties. More specifically, several authors 1–5 reported periprosthetic osteolysis and aseptic failure following contemporary total hip arthroplasties with second-generation metal-on-metal articulations. Metal hypersensitivity has been proposed as a mechanism of aseptic loosening of these components.3,5–7,8,9 Histologic examination of the retrieved periprosthetic tissues from patients who had undergone revision because of aseptic loosening or technical failure showed metallosis and extensive lymphocytic and plasma-cell infiltration around the metal debris.10,11

In the retrievals derived from our revised hips 11 there was evidence of cobalt-chromium metallosis in the capsule and the periprosthetic tissues from all revised hips. Extensive necrosis within the new synovial membrane was observed in all revised hips. Moreover, a predominantly perivascular lymphoplasmacytic infiltrate was observed in the periprosthetic tissues retrieved during the revisions for aseptic indications.

With respect to the short-term results of the authors' study, I would like to draw attention to these authors that implantation of disc arthroplasties with Co-Cr metal on metal articulation should be performed taking always under consideration the results from implantation of metal-on-metal articulating surfaces in other joints. It is quite clear that the range of movement in a lumbar disc arthroplasty is not comparable to that of a big joint as that of the hip, but the observed allergy and subsequent osteolysis leading to loosening of the implants should be reconsidered.

Panagiotis G. Korovessis, MD, PhD

Orthopaedic Surgeon

Department of Orthopaedics

General Hospital Agios Andreas

Patras, Greece

References

1.Gawkrodger DJ. Metal sensitivities and orthopaedic implants revisited: the potential for metal allergy with the new metal-on-metal joint prostheses. Br J Dermatol2003;148:1089–93. [Context Link]

2.Antony FC, Holden CA. Metal allergy resurfaces in failed hip endoprostheses. Contact Derm 2003;48:49–50. [Context Link]

3.Park YS, Moon YW, Lim SJ, et al. Early osteolysis following second-generation metal-on-metal replacement. J Bone Joint Surg Am 2005;87:1515–21. [Context Link]

4.Willert HG, Buchhorn GH, Fayyazi A, et al. Histopathologische Veränderungen bei Metall/Metall-Gelenken geben Hinweise auf eine zellvermittelte Überempfindlichkeit-vorläufige Untersuchungsergebnisse von 14 Fällen. Osteologie 2000;9:165–79. [Context Link]
5.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;87:28–36. Ovid Full Text Bibliographic Links [Context Link]

6.Klapperich C, Graham J, Pruitt L, et al. Failure of a metal-on-metal total hip arthroplasty from progressive osteolysis. J Arthroplasty 1999;14:877–81. ExternalResolverBasicBibliographic Links [Context Link]

7.Visuri T, Pukkala E, Paavolainen P, et al. Cancer risk after metal on metal and polyethylene on metal total hip arthroplasty. Clin Orthop Relat Res 1996;329:S280–89. Ovid Full Text Bibliographic Links [Context Link]

8.Beaule PE, Campbell P, Mirra J, et al. Osteolysis in a cementless, second generation metal-on-metal hip replacement. Clin Orthop Relat Res 2001;386:159–65. Ovid Full TextBibliographic Links [Context Link]

9.Jasty M, Bragdon C, Jiranek W, et al. Etiology of osteolysis around porous-coated cementless total hip arthroplasties. Clin Orthop Relat Res 1994;308:111–26. Ovid Full TextBibliographic Links [Context Link]

10.Sieber HP, Rieker CB, Kottig P. Analysis of 118 second-generation metal-on-metal retrieved hip implants. J Bone Joint Surg Br 1999;81:46–50. [Context Link]

11.Korovessis P, Petsinis G, Repanti M, et al. Metallosis after contemporary metal-on-metal total hip arthroplasty. Five- to nine-year follow-up. J Bone Joint Surg Am 2006;88:1183–91.