Using an aggressive testing protocol, we placed our VERILAST◊ Hip implants along with an implant made from cobalt chrome and a standard plastic liner, and an implant made from cobalt chrome and an XLPE liner onto 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.
During the first phase of testing, all three implant types were placed under a load of 899 pounds (4000 Newton), which is approximately 4.9 times the typical body weight of a hip replacement patient (185 pounds), while the machine completed nearly 8 million cycles. The machine was then stopped and all of the implants were carefully measured to determine how much wear had occurred to the ball and liner components. The results from this first phase of wear testing were very encouraging.
Armed with the data from the first 7.8 million cycles, we decided to continue "walking" the two best performing implants (VERILAST Technology and cobalt chrome on XLPE) out to 45 million cycles - the equivalent of 9-times the industry standard.1-8
The results surpassed even our high expectations.
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.
Hip replacement surgery is intended to relieve hip pain and improve hip function. However, implants may not produce the same feel or function as your original hip. There are potential risks with hip replacement surgery such as loosening, fracture, dislocation, wear and infection that may result in the need for additional surgery. Longevity of implants depends on many factors, such as types of activities and weight. Do not perform high impact activities such as running and jumping unless your surgeon tells you the bone has healed and these activities are acceptable. Early device failure, breakage or loosening may occur if you do not follow your surgeon's limitations on activity level. Early failure can happen if you do not guard your hip joint from overloading due to activity level, failure to control body weight, or accidents such as falls. Talk to your doctor to determine what treatment may be best for you.
1 Testing concluded at 45 million cycles. ISO 14242-1 defines test completion at 5 million cycles.
2 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.
3 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).
4 Gioe TJ et al., "Knee Arthroplasty in the young patient - Survival in a community registry". Clin Orthop Relat Res, 464:83-87, 2007.
5 Wallbridge N and Dowson D. "The walking activity of patients with artificial hip joints". Eng Med 11:95, 1982
6 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.
7 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.
8 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.
9 ASTM F2384.19404-1 and ASTM F75.17485-1
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.