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.