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Mechanically assisted crevice corrosion in THA higher than previously reported
Metal-on-polyethylene THA and mechanically assisted crevice corrosion linked to risk of major complications with revision.
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The prevalence of mechanically assisted crevice corrosion was higher than researchers expected when they studied patients who underwent non-cemented contemporary metal-on-polyethylene total hip arthroplasty.
“With a high percentage of patients who have this problem, there are adverse local tissue reactions that occur. So, if you have symptomatic corrosion you often have a lot of damage of the soft tissues,” Brian J. McGrory, MD, MS, in the division of joint replacement at Maine Medical Center, told Orthopedics Today. “... That is something to worry about and, therefore, my recommendation is we should use non-cobalt femoral heads until we figure out why this seems to occur at a higher rate than we expect.”
Mechanically assisted corrosion
McGrory and his colleagues followed up 1,352 consecutive THAs performed by a single surgeon using titanium M/L Taper stems with a 12/14 taper, cobalt-chromium alloy femoral head and highly cross-linked polyethylene liner (Zimmer Biomet) at 1-year and 5-year intervals or earlier, if patients had symptoms. Patients underwent examinations, radiographs, complete blood count, tests for erythrocyte sedimentation rate, C-reactive protein and serum cobalt and chromium levels. Serum metal levels were checked in patients who had osteolysis greater than 1 cm or unexplained pain.
Results showed 3.2% of patients presented with symptomatic mechanically assisted crevice corrosion (MACC), which ranged in prevalence from 0% to 10.5% based on the year of THA surgery.
Source: Brian J. McGrory, MD, MS
“No one has done a prevalence study with this particular implant or set of implants, and this number is similar in magnitude to some of the prevalence estimates you see with implants that have been recalled, and this implant set has not been recalled,” McGrory said.
Researchers noted a 4.7% prevalence of MACC with the M/L Taper stem vs. 1.2% with all other Zimmer 12/14 trunnion stem types combined. Overall, 62.8% of patients underwent revision surgery and 37.2% of patients selected ongoing surveillance.
There was no demographic, clinical or radiographic difference between symptomatic patients with and without MACC. Compared with neck lengths of –3.5 mm, as well as +3.5 mm, a neck length of 0 mm showed an increased risk for MACC.
High complication rate
In a second study of the revisions, 25.9% of 27 patients who underwent revision THA for MACC experienced major orthopedic complications at 6 months follow-up, minimum. The Harris hip score (HHS) improved significantly with surgery and there were good or excellent outcomes in 74.1% of patients, but McGrory and colleagues found the HHS was lower for patients with major complications.
“Patients who have a symptomatic MACC have a high complication rate after they have been revised. So that is worrisome,” McGrory said. “Not only is the prevalence higher than we thought, but when you try and fix it, a high percentage of those patients do not do well.” – by Casey Tingle
- References:
- Hussey DK, et al. J Arthroplasty. 2017;doi:10.1016/j.arth.2017.03.020.
- McGrory BJ, et al. J Arthroplasty. 2017;doi:10.1016/j.arth.2017.07.004.
- For more information:
- Brian J. McGrory, MD, MS, can be reached at Division of Joint Replacement, Maine Medical Center, 5 Bucknam Rd., Suite 1D, Falmouth, ME 04105; email: mcgrob1@mmc.org.
Disclosure: McGrory reports he is a consultant for Smith & Nephew.
Perspective
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Antonia F. Chen, MD, MBA
This is an interesting study that adds to the expanding body of literature on metal corrosion present after implanting metal-on-polyethylene THA prostheses. What distinguishes this research is that a single implant was differentiated as exhibiting a higher rate of MACC during a certain year (2009). Although the authors do not provide an explanation for this finding, it is imperative that the manufacturing process used for these implants be regularly scrutinized and implant performance data be periodically assessed to determine irregularities. National registries, such as the American Joint Replacement Registry, are of utmost importance when providing surveillance for implants and will potentially alert orthopedic surgeons to implant problems before they become rampant.
Another benefit of this study is a single-surgeon series is reported, so a denominator is present in order to determine the prevalence of MACC. This study can be combined with other studies to determine if the prevalence of MACC is specific to this implant during a certain year or if other factors impact the presence of MACC from all metal-on-polyethylene THA implants.
Finally, this study highlights the importance of using ceramic femoral heads. Although metal femoral heads are still more accessible and more cost effective worldwide, ceramic heads can circumvent the problem with MACC and may be the material choice for femoral heads in the future.
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