Total Hip Replacement
How is Hip Surgery Performed?
During hip replacement surgery, the surgeon surgically removes the damaged bone and cartilage of the joint and replaces it with smooth, artificial implants - thereby eliminating painful bone-on-bone contact.
Almost all hip replacement implants consist of a four-part system:
- A hip stem, usually made from a biocompatible metal such as titanium, which is implanted down the shaft of the thigh bone (femur);
- A femoral head which sits on top of the hip stem and replaces the "ball" portion of the hip's "ball and socket" design; and
- A two-part hemispherical or "cup-like" component made up of a metal shell and a plastic liner that replaces the "socket" in which the femoral head sits.
- Once implanted, the new femoral head rotates inside the plastic liner to recreate the ball and socket movement of the original joint.
Hip Metal Sensitivity and Allergy
Could You Be Allergic to Your Hip Implant?
The surprising answer to this question is yes.
While the majority of patients might not make the association between a hip implant and allergies, for anyone who has ever had an adverse reaction to things like jewelry, watches or metal pant buttons, the link is much clearer and more important. That's because your body's potential reaction to an orthopaedic implant may be predicted by your skin's reaction to items containing nickel or chromium - two metals present in cobalt chrome and in most metal hip implants. In many cases, sensitivity to these allergens has resulted in revisions for joint replacement patients.1-4
While studies show that less than 10% of the population has a sensitivity to these metals1, it is possible to develop new allergies over the course of your lifetime. Although it is not clear what triggers new allergies, studies have shown that the rate of metal allergy increases to 25% in people who have a metal implant in their body and to 60% of patients who need to have their first implant surgically replaced.5
VERILAST? Technology uses our proprietary OXINIUM? oxidized zirconium for the hip ball rather than the more commonly used cobalt chrome. Our OXINIUM alloy has less than 0.0035% nickel content, and less than 0.02% chromium content compared to up to 0.5% and 30.0% respectively in cobalt chrome.6 Moreover, oxidized zirconium is a nearly inert material that has not been reported to induce immune reactions.7
Hip Oxinium◊ Oxidized Zirconium
What is OXINIUM◊ Oxidized Zirconium?
If it is determined that an implant made with VERILAST? technology is right for you, the femoral head or ball of your implant will be made from OXINIUM Oxidized Zirconium - a patented ceramicised metal alloy that Smith & Nephew spent more than a decade developing.
During manufacture, OXINIUM implants undergo a process that transforms the zirconium surface into a hard, ceramicised metal - while still retaining all of the durability of the underlying metal. This means that it won't fracture like a true ceramic, yet its ceramicised surface is more than twice as hard and therefore twice as resistant to the kind of scratching that can cause a cobalt chrome implant to wear out before its time.1
Also, unlike cobalt chrome, the OXINIUM material contains almost no nickel (< 0.0035% vs. ? than 0.5%) and is therefore biocompatible for patients with metal allergy or metal sensitivity.
Important Safety Notes:
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 Hallab NJ, Anderson S, Stafford T, Glant T, Jacobs JJ. "Lymphocyte responses in patients with total hip arthroplasty." J Orthop Res 2005; 232:384e91.
2 Niki, Yasuo et al. "Screening for symptomatic metal sensitivity: a prospective study of 92 patients undergoing total knee arthroplasty." Biomaterials 26 (2005) 1019-1026
3 Nesser, s. "Biology of foreign bodies: tolerance, osteolysis, and allergy", Total Knee Arthroplasty, J. Bellemans, M.D. Ries, and J. Victor (eds.), Springer Verlag, Heidelberg, Germany, 2005, pp. 343-352
4 Granchi, Donatella et al. "Sensitivity to implant materials in patients with total knee arthroplasties." Biomaterials 29 (2008) 1494-1500
5 ASTM International Standard Specification for Wrought Zirconium-2.5Niobium Alloy for Surgical Implant Applications (UNS R60901) Designation: F 2384 - 05 and Standard Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants (UNS R30075): Designation: F 75 - 07
6 Hallab, Nadim et al. Metal Sensitivity in Patients with Orthopaedic Implants, The Journal of Bone & Joint Surgery, Vol 83-A No. 3. March 2001 p428-436
7 Zardiackas, Lyle D., Kraay, Matthew J., Freese, Howard L, editors. Titanium, Niobium, Zirconium, and Tantalum for Medical and Surgical Applications ASTM special technical publication; 1471. Ann Arbor, MI: ASTM, Dec. 2005
1 Zardiackas, Lyle D., Kraay, Matthew J., Freese, Howard L, editors. Titanium, Niobium, Zirconium, and Tantalum for Medical and Surgical Applications ASTM special technical publication; 1471. Ann Arbor, MI: ASTM, Dec. 2005
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