Understanding the Multiple Aspects of Head-Neck Taper Corrosion in Metal-on-Polyethylene Total Hip Arthroplasty
In This Article
- Head-neck taper corrosion is an infrequent but emerging serious complication of total hip arthroplasty (THA)
- Multiple aspects must be considered for optimal management to prevent adverse local tissue reactions (ALTR)
- Few physicians and surgeons are educated about these aspects
- Failure to diagnose ALTR early can lead to revision surgeries and implant failure
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Managing adverse local tissue reactions (ALTR) complications in metal-on-polyethylene total hip arthroplasty (THA) patients arising from head-neck taper corrosion is critical to producing successful outcomes.
As Massachusetts General Hospital's Director of the Metal-on-Metal Hips and Tribocorrosion Center, Program Director for the Adult Reconstructive Surgery Fellowship Program and a Harvard Medical School orthopaedic surgery associate professor, Young-Min Kwon, MD, PhD, specializes in minimally invasive total hip and knee replacements and complex revision surgeries through Mass General's Center for Hip & Knee Replacement.
"We are one of the first groups to quantify taper corrosion impact," Dr. Kwon says, "and we did so based on our expertise in managing adverse local tissue reactions in patients with metal-on-metal hips who present with similar clinical challenges, and we know that a lot of patients are really concerned about risks and the metal levels in their body." A Mass General team led by Dr. Kwon has recently published a series of reports on the clinical impact of head-neck taper corrosion, providing clinical guidelines to the surgeons in diagnosis and treatment of this emerging complication in patients with THA.
Preventing Complications
Head-neck taper corrosion-related ALTR is an infrequent complication of THA with modular implants. Yet, the issue merits urgent attention to avoid joint failure and revision surgery because of the large number of patients undergoing THA each year and the potential risk many people may face. More than 600,000 THA procedures are performed in the US annually in patients 45 years and older. The reported prevalence of adverse tissue reactions ranges from 1-3% of modular THA patients.
Moreover, after revision of ALTR associated with head-neck taper corrosion, a high rate of early complications (25%) and re-revisions (10%) was reported by a Mass General team led by Dr. Kwon.
A Systematic Approach
Early diagnosis of head-neck taper corrosion is imperative if patients are to avoid substantial necrosis in the joint and revision surgery. To support early diagnosis, Dr. Kwon and colleagues devised a systematic approach focused on three key aspects of head-neck taper corrosion:
- Recognizing the risk factor evidence from Dr. Kwon's team's research into ALTR
- Measuring patient sensitivity to metal ions as a possible early predictor of ALTR
- Understanding the fate of metal levels after surgery
Risk Factors
Adverse local tissue reactions were first described as a complication of metal-on-metal bearings. Recently, Dr. Kwon's research extended the understanding of ALTR to metal-on-polyethylene bearings in modular taper junctions, reporting in The Journal of Arthroplasty.
Following ALTR associated with head-neck taper corrosion, the team observed a significant rate of early complications (25%) and re-revisions (10%). Risk factors associated with post-revision surgery included pre-revision MRI findings of solid lesions with abductor deficiency and intraoperative tissue damage.
"This information is highly relevant and helpful for clinical decision-making and preoperative counseling of metal-on-polyethylene THA patients undergoing revision surgery for head-neck taper corrosion," says Dr. Kwon.
Measuring Sensitivity to Predict ALTR
The understanding of the impact of taper corrosion on the levels of metals in the blood serum is evolving, and Dr. Kwon's team's research is contributing significantly to the science.
"We are among the first groups to educate surgeons that a lower metals level needs to be flagged as important in the setting of taper corrosion," he says.
Where 5 parts per billion (pbb) is not a worrisome level when metal-on-metal implants are in place, if there is taper corrosion involvement involving metal-on-polyethylene, a 1 ppb measurement is an elevated level.
"That's very important," Dr. Kwon says. "Because a lot of surgeons think the metal levels they are used to in assessing metal-on-metal cases apply here. But with a non-metal-on metal hip, a 1ppb level should trigger further investigation. "
Understanding the Post-Operative Fate of Metals
Because MoP THA patients are concerned about post-operative levels of metals in their blood, Dr. Kwon sought to understand the fate of those metals over time.
Elevated metal ion levels have been associated with the presence of ALTR in patients with MoP total hip arthroplasty (THA) secondary to corrosion at head-neck taper junction, so the question was pressing.
Dr. Kwon's research team investigated the rate of decline of serum metals levels of cobalt and chromium ion after revision surgery. Results showed that three months after revision surgery, cobalt and chromium ion levels declined by 34% and 8% of pre-revision level, respectively.
"This kind of practical evidence is what surgeons need to guide clinical decision-making," he says. "This is a new area we are entering with the metal-on-polyethylene hips, and Mass General's research, clinical expertise and leadership are all critical in providing the best care for patients."
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