We understand that "30 years of wear performance" is a pretty significant statement for any implant manufacturer to make. That's why we want you to see how we can back it up.
Using an internationally accepted testing protocol, our LEGION◊ Knee with VERILAST◊ Technology was placed alongside identical implants made from cobalt chrome and a standard plastic liner and cobalt chrome and an XLPE liner into a sophisticated machine that continually simulates the cycle of movement required by a normal walking motion. Each cycle is equivalent to the range of movement required for an average person to take a step.2
During the first phase of testing, all three implant types were placed under a load of 899 pounds, or 4.9 times the typical body weight of a knee replacement patient (185 pounds), while the machine completed 5 million cycles. The machine was then stopped and all of the implants were carefully measured to determine how much wear had occurred to the metal and plastic components. The results from this first phase of wear testing very encouraging.
Armed with the data from the first 5 million cycles, we decided to continue "walking" the LEGION CR Knee with VERILAST Technology Implant out to 45 million cycles - the equivalent of 30 years of an active adult's life under typical conditions.1
After a total of nearly three years of continuous laboratory wear testing, the results surpassed even our high expectations.
After 45 million cycles, the LEGION CR Knee with VERILAST Technology showed 81% less wear - even when compared to the cobalt chrome knee that was stopped after only 5 million cycles.1
Based on scientific literature reviews, a person who undergoes knee replacement surgery at the relatively young age of 45 years old would subject the implant to between 36 and 44 million cycles over a 30-year period, depending on how active the person's lifestyle is.3-9 Smith & Nephew chose the high end of this range - 45 million cycles - as the simulated 30-year mark.
VERILAST knee wear testing and results apply only to the VERILAST LEGION CR Primary Knee System only. Extended lab-testing for other VERILAST knee systems have not been performed. The results of laboratory wear simulation testing have not been proven to predict actual joint durability and performance in people. A reduction in wear alone may not result in improved joint durability and performance because other factors, such as bone structure, can affect joint durability and performance and cause medical conditions that may result in the need for additional surgery. These other factors were not studied as part of the testing.
Individual results of joint replacement vary. Implants are intended to relieve knee pain and improve function, but may not produce the same feel or function as your original knee. There are potential risks with knee replacement surgery such as loosening, wear and infection that may result in the need for additional surgery. Patients should not perform high impact activities such as running and jumping unless their surgeon tells them that the bone has healed and these activities are acceptable. Early device failure, breakage or loosening may occur if a surgeon's limitations on activity level are not followed.
1 ASTM F2384.19404-1 and ASTM F75.17485-1
2 ISO 14243-3
3 R. Papannagari, G. Hines, J. Sprague and M. Morrison, "Long-term wear performance of an advanced bearing knee technology," ISTA, Dubai, UAE, Oct 6-9, 2010.
4 Goldsmith AA et al., "Comparative study of the activity of the total hip arthroplasty patients and normal subjects". J Arthrop, (16)5:613-619, 2001.
5 Morbidity and mortality weekly report, 55(40):1089-1092, October 13, 2006.(http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5540a2.htm?s_cid=mm5540a2_e. Accessed on October 30, 2009).
6 Gioe TJ et al., "Knee Arthroplasty in the young patient - Survival in a community registry". Clin Orthop Relat Res, 464:83-87, 2007.
7 Wallbridge N and Dowson D. "The walking activity of patients with artificial hip joints". Eng Med 11:95, 1982
8 Wimmer M A et al., "Joint motion and daily activity profile of total knee patients in comparison with the ISO knee wear simulator". Paper 0159, 48th ORS, 2002. - 8 Huddleston J I et al., "How often do patients with high-flex total knee arthroplasty use high flexion?",Clin Orthop Relat Res, 467:1898-1906, 2009.
9 Naal F D et al., "How active are patients undergoing total joint arthroplasty? A systematic review", Clin Orthop Relat Res, DOI 10.1007/s11999-009-1135-9, published online: 28 October 2009.
The information listed on this site is for informational and educational purposes and is not meant as medical advice. Every patient's case is unique and each patient should follow his or her doctor's specific instructions. Please discuss nutrition, medication and treatment options with your doctor to make sure you are getting the proper care for your particular situation.