The number of U.S. residents over the age of 65 is expected to almost double by the year 2030. According to Zacks.com,¹ a stock advisory service, Stryker, Zimmer Biomet, and other orthopedic companies benefit from the aging of the U.S. population because knee and hip implants will deteriorate and need to be replaced. New technology has increased the durability of knee replacement solutions and longer-lasting implants have led to an increase in the number of younger patients receiving them. While technology improvements lead to better outcomes, it is reported that approximately 19 percent of patients with otherwise well-placed knee implants are dissatisfied with the implant results.² Some patients report experiencing pain, stiffness, and swelling after total knee arthroplasty (TKA) which, in part, may be attributable to metal hypersensitivity—a controversial topic in orthopedics.

Why This is Important
In the United States, surgeons performed slightly more than 542,000 total knee replacements (TKRs) in 2006,³ and it is estimated that this number grew to 670,000 in 2012 (Chart 1).⁴ Increasing demand for TKR will place a growing burden on the U.S. healthcare system, a strong need for faster and easier procedures, and a decrease in revision, which all drive reduced cost.

What Are the Causes of Patient Dissatisfaction with Knee Implants?
There are several possible causes of patient dissatisfaction with knee implants, and a diagnosis of metal hypersensitivity is one of the most challenging. According to a recent article, metal hypersensitivity after TKA is infrequent and should only be considered after ruling out infection, instability, loosening of components or mal-rotation, localized pain, and ongoing complex regional pain syndrome.⁵ One study advises that if metal hypersensitivity is assumed to be the root cause (assuming nonsurgical methods are unsuccessful), revision to components made with zirconium coating or from titanium alloy may be the next step to alleviating symptoms.⁶ Of course, revision should always be the last option of care.

The incidence of metal sensitivity in the general population is lower (10-15 percent, and varies by metal type) than that in patients with well-functioning implants, estimated at 25 percent.⁸ Prevalence is shown to increase in clinical studies of patients with “failed, loose, or poorly functioning implants” and has been measured up to 60 percent of this patient population (range: 13 percent to 71 percent).

New Technology in Development
While implant-linked metal sensitivity has been studied, it is still a random complication that needs further clinical study.^9-11 Manufacturers such as Smith & Nephew plc and Aesculap Inc. are leading the way to develop implant technology to directly address metal sensitivity concerns associated with joint replacement implants. The results? Knee and hip implants are a mature market but innovation in this space can still drive change. 


References:

1. http://www.zacks.com/ZER/rd_get_pdf.php?r=SYK
2. Bourne, RB et. al Patient Satisfaction after Total Knee Arthroplasty, Clin Orthop Relat Res (2010) 468:57–63
3. http://www.cdc.gov/nchs/data/nhsr/nhsr005.pdf
4. Agency for Healthcare Research and Quality. Healthcare Cost and Utilization Project database. 2012
5. J Am Acad Orthop Surg 2016;24: 106-112
6. Mulhall KJ, Ghomrawi HM, Scully S, Callaghan JJ, Saleh KJ: Current etiologies and modes of failure in total knee arthroplasty revision. Clin Orthop Relat Res 2006;446(446):45-50.
7. Op cit 2
8. Op cit 2
9. Basketter DA, et. al. Nickel, cobalt and chromium in consumer products: a role in allergic contact dermatitis? Contact Dermatitis. 1993;28:15-25.
10. Cramers M, Lucht U. Metal sensitivity in patients treated for tibial fractures with plates of stainless steel. Acta Orthop Scand. 1977;48:245-9.
11. Fisher AA. Allergic dermatitis presumably due to metallic foreign bodies containing nickel or cobalt. Cutis. 1977;19:285-6

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Maria Shepherd has 20 years of leadership experience in medical device/life-science marketing in both small startups and top-tier companies. After her industry career, including her role as vice president of marketing for Oridion Medical, where she helped boost the company valuation prior to its acquisition by Covidien plc (now Medtronic), director of marketing for Philips Medical, and senior management roles at Boston Scientific Inc., she founded Medi-Vantage (formerly Data Decision Group). Medi-Vantage provides medtech marketing and business strategy and white-space research to support medical device decision-making. The firm quantitatively and qualitatively sizes opportunities, evaluates new technologies, provides marketing services, and assesses prospective acquisitions. Shepherd has taught marketing and product development courses, and is on the board of the Aligo Investment Committee. She can be reached at 855-343-3100  or at mshepherd@medi-vantage.com.