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Controversy remains over use of metal-on-metal implants for total hip arthroplasty
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Amid the recent recall of two popular metal-on-metal total hip implants, an investigation of these constructs by the Medicines and Healthcare products Regulatory Agency in the United Kingdom and an FDA order for postmarket surveillance studies on these bearing couples, Adolph V. Lombardi Jr., MD, FACS, cautioned an audience at the SICOT XXV Triennial World Congress 2011 to remember that, “not all metal-on-on metal articulations are created equal.”
“We know that there is a low wear couple,” Lombardi said during his presentation. “There is still some ongoing concern regarding metallosis and hypersensitivity. ... I think that, at least on my end, it is still indicated in the high-demand, active male.”
Although metal-on-metal (MoM) constructs show low clinical wear and give surgeons the opportunity to perform anatomic reconstructions, Lombardi noted that these implants have come under criticism because of adverse tissue reactions to metal debris often cited as metallosis, aseptic lymphocytic vasculitis-associated lesions (ALVAL) and hypersensitivity. He said that MoM systems vary by aspects including metallurgy, the design of the components, geometry and type of fixation, and that design and manufacturing conditions impact wear behavior and rates.
He cited a study by Daniel et al which showed no significant differences in the chromium and cobalt concentrations at 1 year between patients who underwent hip resurfacing and those who had total hip replacement (THR) using a 28-mm MoM construct. However, Lombardi noted that recently published studies comparing resurfacing and THA with larger heads showed higher concentrations of the metal ions in the total hip patients, which he attributed to possible “fretting corrosion that occurs at the head-neck junction.”
Other studies have pointed to the sensitivity of MoM constructs to component positioning.
“We learned that the safe position [of] 45° may not be that appropriate for metal-on-metal for abduction.” He also noted that excessive anteversion can cause impingement, dysplasia and pseudotumors.
Adverse reactions
The results from a study by Pandit et al highlighted the development of pseudotumors in patients who underwent MoM procedures, Lombardi said. Based on his study of 17 patients, Pandit estimated that 1% of patients would develop a pseudotumor within 5 years of a MoM resurfacing. Further research by Glyn-Jones et al, however, showed that pseudotumors were more likely to develop in patients with smaller components, those who are younger than 40 years and women. Pseudotumors were present in 13% of women younger than 40 years at 6 postoperative years, in 6.2% of women older than 40 years at 8 postoperative years and in 0.5% of men at 8 years after surgery.
Rates in non-MoM implants
Lombardi noted that histology of perivascular lymphocytic infiltration and the presence of pseudotumors are not specific to cases using MoM constructs. He and colleagues examined perivascular lymphocytic infiltration in 215 revision hip and 242 knee cases. They found PLI in cases of failed knees as well as THAs with MoM and metal-on-polyethylene constructs.
“We concluded that it was not limited to failed MoM arthroplasty, but [was] obviously more extensive,” Lombardi said.
He also cited a separate systematic review of soft tissue complications in THA by Carli et al that identified 27 reports representing 30 cases in which a pseudotumor was present in cases with non-MoM implants.
Hypersensitivity reaction tests that use lymphocyte proliferation response may not be helpful, Lombardi said, as a study by Kwon et al found that lymphocytic metal-induced reactivity, while increasing with metal exposure, could not be connected to patients with pseudotumors since researchers found no difference in the cobalt, chromium and nickel reactivity in patients with or without pseudotumors.
Lombardi recognized the ongoing controversies with MoM implants and closed his lecture by indicating that how the implant is inserted makes a difference in the wear rate of the component. He stressed the importance of checking patients for sensitivity to metallurgy and checking metal ion levels before doing any unnecessary revisions. – by Gina Brockenbrough, MA, and Jeff Craven
References:
- Lombardi A. International Hip Society Symposium: Bearing couples: Metal-metal. Presented at the SICOT XXV Triennial World Congress 2011. Sept 6-9. Prague.
- Carli A, Reuven A, Zukor DJ, Antoniou J. Adverse soft-tissue reactions around non-metal-on-metal total hip arthroplasty - A systematic review of the literature. Bull NYU Hosp Jt Dis. 2011;69(1):47-51.
- Daniel J, Ziaee H, Salama A, Pradhan C, et al.The effect of the diameter of metal-on-metal bearings on systemic exposure to cobalt and chromium. J Bone Joint Surg Br. 2006;88(4):443-448.
- Glyn-Jones S, Pandit H, Kwon YM, et al. Risk factors for inflammatory pseudotumor formation following hip resurfacing. J Bone Joint Surg Br. 2009;91(12):1566-1574.
- Kwon YM, Thomas P, Summer B, et al. Lymphocyte proliferation responses in patients with pseudotumors following metal-on-metal hip resurfacing arthroplasty. J Orthop Res. 2010;28(4):444-450.
- Ng VY, Lombardi AV Jr, Berend KR, Skeels MD, et al. Perivascular lymphocytic infiltration is not limited to metal-on-metal bearings. Clin Orthop Relat Res. 2011;469(2):523-529.
- Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, et al. Pseudotumors associated with metal-on-metal hip resurfacings. J Bone Joint Surg Br. 2008;90(7):847-851.
- Adolph V. Lombardi Jr., MD, FACS, can be reached at Joint Implant Surgeons, 7277 Smith’s Mill Road, Suite 200, New Albany, Ohio 43054; 614-221-6331; email: lombardiav@joint-surgeons.com.
- Disclosure: Lombardi receives royalties from, is on the speaker’s bureau for, is a paid consultant of and receives research/institutional support from Biomet.