OVERVIEW OF KNEE REPLACEMENT AND IMPLANT
Knee replacement or arthroplasty, is a surgical process to resurface a knee which had been damaged by arthritis. Damaged bones ends are capped by metal and plastic parts, which will help in forming the knee joint, along with the kneecap. Goal of this treatment is to provide relief form the pain that had been caused by the damaged knee.
In knee replacement surgery, an orthopedic surgeon resurfaces the damaged knee with an artificial components, called as implants .These implants are made of metal alloys, ceramic material, or strong plastic part.
Implants differ greatly by their design, fixation and materials. Manufacturers are offering different models and features, which are designed on the basis of a patient’s size and activity level as not one-size-fits-all or even one-style-fits-all. The brand and design used by the doctor or hospital will depends on many factors, including
An individual needs, which will be based on the knee problem and knee anatomy, as well as the patients age, weight, activity level, and general health
Doctor's experience and familiarity with the device
COMPONENTS OF IMPLANTS
Commonly used material for implant is Metal. There are a variety of different metal alloys being used, few of the common ones are:
There is no consensus as to which material is better and more suitable.
Titanium & its alloys
Titanium alloy being biocompatible in nature has been the preferred material. The most popular titanium alloy being used in knee implants is Ti6Al4V.
Titanium alloy: Mostly contain amounts of vanadium and aluminum in addition to Titanium. Titanium & its alloys have great corrosion resistance, which makes them inert biomaterial (means there will be no change in them after being implanted in the body).Titanium implant can act more like the natural joint, due to which the risk of some complications like bone resorption and atrophy is reduced. This is because of the elastic nature of titanium and its alloys, which is lower than any other metals being used in knee implants
Pure titanium: Is mostly used in implants when high strength is not needed. For example, pure titanium is sometimes used to create fiber metal, a layer of metal fibers bonded to the surface of an implant which allows bone to grow into the implant or allows cement to better bond to the implant for stronger fixation.
Is a type of pure metal, having excellent biological and physical properties. Flexibility, corrosion resistant, and biocompatibility are its main properties.
Trabecular Metal: Is a porous material which has been made of tantalum .Pore size of this material helps in bone regrowth, forming a better bridge between the metal & bone. In addition to this, trabecular Metal also has an elastic nature which aids in bone remodeling.
There are two types of Zirconium materials
Zirconium alloy and all plastic tibial component
Oxinium oxidized zirconium
Zirconium alloy and all plastic tibial component:
Zirconium alloy is being used in a new ceramic knee implant. It is used in combination with an all-plastic tibial component, and not the traditional metal tray and plastic insert, which are used in other knee replacements. It is believed that this new knee could last for approximately 20-25 years.
Lubrication: This new combination can be lubricated, resulting in a smoother and easier articulation through plastic.
Biocompatibility: This is an important property of this material. That is, it is suitable for people who are allergic to nickel and cannot have cobalt- chromium alloy based knee implants.
Oxinium oxidized zirconium:
This is the most recent material being used in knee implants. It is primarily a transformed metal alloy having a ceramic bearing surface. It contains zirconium and niobium alloy that are oxidized to convert the surface of the material into zirconia ceramic.
Advantage: As only the surface of the metal has been changed, the rest of the implant component still has a high tensile metal. It is twice as hard as cobalt chromium alloys, it provides half the friction thus performs with higher quality and lasts for a longer time.
It is an extremely inert, bio-compatible, hard, tough, corrosion resistance and durable material. It has all the ideal properties for a surrogate knee joint.
Disadvantage: The only disadvantage of this material is the release of tiny metal ions due to joint movement i.e. while moving, walking, etc. Mostly these fragments are harmless. But at times, these particles can cause reactions in the human body, commonly in case of those patients who are allergic to special metals like nickel.
Finally, the knee replacement surgeon will be the one to decide, using whichever implant or implants he or she feels is best for the situation and whichever product he or she has had previous success with.
KNOWN IMPLANT PRODUCTS
Zimmer persona knee by Zimmer Biomed
Zimmer world headquarters are in Warsaw, Indiana & was founded in 1927.
Morphologic knee implant designs
Comprehensive sizing with tighter increments
Cruciate Retaining and Posterior Stabilized philosophies
BIOLOX delta by CeramTec (Metal free arthroplasty)
Ceramtec is a European based private equity firm which founded in 1977. It has its offices in Guernsey, London, Frankfurt, Paris, Milan, Luxembourg and Hong Kong.
Excellent biological behavior
No known risk of allergy
No metal ion release
No known pathogenic reaction to ceramic particles
Reduced risk of infection
Lower wear of polyethylene against ceramic
High hardness and scratch resistance
Resistance to third-body wear
5 successful years in clinical use
Universal Rolflex by Evolutis
Evolutis was created in 1999 by a group of experienced orthopedic professionals.
Femoral Condyles and tibial baseplates are made of Cobalt-Chromium
Reversible femoral Condyles right and left are available in 6 sizes for cemented use only
A/P and M/L dimensions, and femoral resections identical to those of the Anatomic version
Accentuated and highly congruent trochlear groove identical to Anatomic version
Reversible tibial baseplate right and left available in 6 sizes, including the 3 smaller sizes with short keel
Center of rotation of tibial insert in the middle of the M/L dimension
The available tibial inserts, available in 5 thicknesses are made of polyethylene PEXEL moderately crosslinked and vacuum-packed.
Instrumentation set limited to 3 trays
Vanquish Ligamentoplasty by Evolutis
VANQUISH system is meant to facilitate both ACL (Anterior Cruciate Ligament) and PCL (Posterior Cruciate Ligament) plasties through Kenneth-Jones or semitendinous-gracilis autograft techniques. The system is based on a unique and complete instrument set which includes a graft tensioning table, ACL and PCL guides, and strippers among others.
The VANQUISH implants can be combined with one another so as to adapt to the dedicated technique of the surgeon: interference screws, endo-button, and staples.
Composite of D & L lactic acid, bio absorbable and biocompatible
Progressive resorption with no crystalline residues
Soft thread armless to the graft and the sutures
Titanium plate with rounded angles to prevent chaffing of the loop and threads
Made of cobalt-chromium
Internal spikes for graft stability
Direct impaction into bone, no necessary preparation
ATTUNE Knee by DePuy Synthes part of Johnson & Johnson family
The DePuy Synthes Companies is a part of the Johnson & Johnson Family of Companies. The DePuy Synthes Companies have been innovating and discovering for over 100 years.
Designed to help improve stability and motion.
It combines the latest in design, kinematics, engineering and materials to deliver a high level of stability and motion to help patients achieve their optimum range of motion, giving them freedom to move while remaining very stable
Freedom total knee system by Maxx medical
The Freedom Total Knee® System allow patients to achieve high-flexion motion regardless of whether the all-poly or metal-backed tibial component is chosen. This approach provides surgeons with unique component options that deliver successful and predictable results.
Incorporates design that redefines the high-flexion arc of the femur while limiting bone resection along the posterior condyles of the femur.
Provides a deeper patella-femoral groove for natural patella tracking with or without resurfacing the patella.
Offers multiple size options that feature dynamically proportioned M/L and A/P femoral components in CR and PS options.
WHICH IMPLANT IS THE BEST?
There are numerous orthopedic manufacturing companies today producing different types of implants used in knee replacement surgery. It is recommend that while selecting an implant that is fit for the patient, following criteria should be seen:
Your implant manufacturer and product should have a successful track record of use (minimum of 5-10 years)
Your surgeon must have a considerable experience in using this implant before
As per your discussion with the surgeon and based on your medical condition