Different Types of Hip Replacement Implants
Ultimately, the hip replacement implant you end up with is selected by your surgeon depending on fit, your arthritic damage, activity level, weight, age, and other lifestyle factors. In saying this, like most things in life, the more you know, the better you can do.
Knowing about the different manufacturers, styles and materials will help you work with your surgeon to select the best implant for you beforehand. Since each implant is very different, surgeons tend to work with only a couple of styles and brands.
The number one thing when zeroing-in on the best hip replacement prosthesis: your surgeon is an absolute expert in the implant style that he or she will be working with.
Let’s learn about hip replacement implants, shall we? This way, you can join the conversation when picking the implant that best matches your lifestyle, activity level, metal allergy or other requirements you may have.
What a Good Hip Replacement Implant Should Have Going For It:
- Allows for normal activities and motion.
- Lasts the expected 15-20 years or more.
- Has a good track record of use in joint replacement recipients (this should be 5-10 years minimum).
- Meets your condition, needs, and any additional requirements (e.g. is biocompatible for those with nickel allergies). Your surgeon will ask about lifestyle, allergies and so forth.
- A very familiar brand and style to your chosen surgeon.
What is Involved in a Standard Hip Replacement?
*Image from OrthoInfo AAOS
A typical hip replacement, regardless of approach (anterior or posterior) involves resurfacing bone and fitting your body with the best components to make up a new hip joint.
Here’s what is involved in a typical hip replacement procedure:
First, the hip is dislocated. This involves pulling the “ball” (femur head) out of its socket (we know, this is a bit cringing to read). The socket is then resurfaced, removing the damaged bone and cartilage. Then, an artificial metal cup is set into place. The small metal cup fits perfectly into the hollow of your bone. It can either be cemented on or “press fit”. Then, a plastic, bowl-shaped insert is fastened into the metal cup. These two pieces form your new socket and is called the “acetabular component”.
What’s the difference between a cemented and press-fit implant? With cement, a fast drying cement is used to “glue” the prosthesis to your actual bone. With cementless or a press-fit, the implant is specially textured so that your actual bone will grow onto the prosthesis and secure it into place. Cemented implants used to be more common but now the cementless options are more used more widely.
Next, the ball-shaped head of your femur (upper thigh bone) that was dislocated from the socket is removed completely. Once the head is removed, the inside of your thigh bone (femur) is resurfaced and an artificial piece is attached to the femur. The stem of the femoral component is then fitted with a new femur head (also called a ball). There are many femoral head sizes and variations, so your surgeon will test which one fits your artificial socket the best. Once attached, the ball piece will be “plugged” into the bowl-shaped socket (the acetabular component). This piece is called the “femoral component”.
All four components will replace your hip’s natural ball and socket. These are the parts that make up a total hip replacement!
The Components: What Makes Up a Hip Replacement Implant?
A natural hip joint is composed of two main components: the ball and socket. During a total hip arthroplasty four parts are introduced to create a new hip. As mentioned in the above (simplified) description of hip replacement surgery, the four artificial components are: the acetabular component, a plastic liner, a femoral head and the femoral stem.
- Acetabular component (socket)– The bowl shaped piece that represents your new socket. This bowl or “cup” shaped piece is fit into your resurfaced socket. This piece is usually made of metal but is occasionally made of ceramic or a combination of plastic and metal.
- Acetabular liner– The plastic liner fits into the acetabular component and allows the femoral head (ball) to glide easier and more naturally in the socket. This piece is usually made of high-quality plastic.
- Femoral head (ball)– The ball that will fit directly into the new, plastic lined socket and is attached to the femoral stem. There are many shapes and sizes of “heads”. These are made of durable metal, plastic, ceramic, or a combination of materials.
- Femoral stem– The stem attaches to the ball and supports the new hip joint. Usually, this metal piece if porous, allowing for natural bone to grow and attach to this piece which replaces your femur.
What materials are used in a hip replacement?
Artificial replacement parts can be made of strong plastic, metal, or ceramic. In most cases, the femoral stem component is built from titanium, titanium cobalt, stainless steel, cobalt-chromium alloys, or a titanium and cobalt mixed metal. The head, liner and acetabular parts can be made of either metal, plastic or ceramic, or a combination of the above. Implant materials have to be strong but flexible in order to allow for everyday movement. They also must be biocompatible (meaning suitable for the body and won’t cause any reactions).
Standard Implant Component Materials
- Metal on Metal (MOM)– This is when the socket and the ball components are all made of metal. The metal components can be a combination of metals like titanium, cobalt-chromium alloys, or cobalt mixed metals.
- Polyethylene and Metal on Polyethylene (MOP)– Polyethylene is a high-quality metal-free plastic. The socket or acetabular liner is usually made of this plastic. In addition, other components can be made of metal and covered with plastic. When a socket is plastic and the ball is metal, this is considered MOP.
- Ceramic on Metal (COM), Ceramic on Polyethylene (COP), Ceramic on Ceramic (COC)– Ceramic hips are less common, and a material not used by all surgeons. Ceramic material is often used in combination with special metal components or plastic components for those allergic to metals. Although ceramic parts are durable, historically, they have been more fragile than metal components. However, this is changing. Today’s ceramic parts are argued to outlast metal part.
For those allergic to metals, titanium alloy is a softer metal with very low (almost untraceable) amounts of nickel. There are components of a replacement that are 100% metal-free. When in doubt, always speak to your care team about a potential metal allergy and ask to get tested.
Hip Replacement Implant Manufacturers/Brands
There are several major companies within the US that produce high-quality hip replacement implants. Each of these companies make a variety of styles with different metals, plastic, and ceramic parts to cover a wide-range of patients and their specific needs. Every surgeon has a preferred brand (or two) and a handful of styles that they work with. Do not expect your surgeon to be well-versed in the offerings of every brand. When it comes to a replacement, you want your surgeon to be an expert in the brand and styles they work with. The more they’ve performed a replacement using your exact type, the better.
Here are the top brands and styles used by surgeons in the US.
Among the most popular manufacturers in the US, Stryker has been around for over 30 years. They offer a variety of femoral components and acetabular components designed to meet the needs of surgeons and patients. There are also different styles of acetabular components like modular dual mobility (mobile) versus the traditional “closed” cup (we know this is a lot of information to take in!).
- Mobile Bearing Hip™ System-- The first Modular Mobile Bearing head by Stryker. It works differently than the standard fixed bearing hip replacement. The acetabular liner and shell allow for motion, rather than being fixed into place. Stryker says this new type of replacement “potentially allows for natural range of motion, enhanced joint stability and minimizes the risk of wear”. Component is made of metal alloys and polyethylene.
- Tritanium Acetabular Shell-- A standard fixed shell component made from “commercially-pure Titanium matrix”. Available for primary joint replacements (not revisions).
- Trident Alumina Ceramic Bearing-- A new technology ceramic socket. Ceramic components are said to be advanced when it comes to extending the lifetime of the implant. Stryker says this ceramic acetabular part “demonstrated significantly lower wear versus conventional plastic-on-metal, or metal-on-metal,joint systems in the laboratory.” Component is made from ceramic material with a titanium shell.
- Trident Polyethylene Bearings-- Stryker offers both mobile bearing and fixed bearing acetabular (socket) components made from high-quality poly (plastic). Stryker also claims that their poly components showed reduced wear when compared to other polyethylene competitors.
- Accolade II-- Fits all surgical approached (posterior or anterior) and bones types. A tapered wedge system that is made of metal alloys. It’s designed to fit a variety of heads (balls).
- Anato-- A shorter stem designed for a variety of surgical approaches (including direct anterior). It comes in 8 different sizes. Made of metal alloys.
- Secur-Fit (Advanced, Max, Plus Max-- 3 different variations available of the Secur-Fit, press-fit (non-cemented) style. All made from biocompatible CP Titanium coating.
- Accolade TMZF-- A tapered wedge, fixed press-fit style. A large selection of femoral heads, including ceramic available. Made of metal alloys.
- Accolade C-- A cemented option. Made of metal alloys, this design can accommodate a variety of femoral heads, like ceramic.
- Omnifit EON-- A femoral stem that’s “designed to offer intelligent design features, proportional stem size choices, and optimal component strength”. This is another cemented option. Can be combined with ceramic or metal head.
Zimmer, now called Zimmer Biomet, is the most popular manufacturer of knee replacements. They also produce a lot of commonly used hip replacement components.
- Trabecular Metal™ Modular Acetabular System-- Made from Trabecular Metal Material that has similar properties to bone and is a porous material that encourages natural bone growth and stability. This implant can be fitted with a variety of poly liners.
- Trilogy Acetabular Hip System-- An improved version of a widely used traditional cup design. It’s porous metal material attaches directly to bone. This implant can be fitted with numerous sizes and thicknesses of poly that are said to be long-lasting without compromising movement.
- Zimmer M/L Taper with Kinectiv Technology-- Comes with a wide array of neck options to fit patients. Designed with different styles to accommodate men, women, older patients, hip fracture patients etc. Made of metal alloys.
- Fitmore Hip Stem-- This femoral piece “offers a personalized fit with a bone conserving, curved stem”. It’s smaller in design and allows for a smaller incision to be made when implanting. It’s designed for natural bone conservation. Made of metal alloys.
- VerSys Epoch® FullCoat Hip-- This stem was designed to mimic the bending stiffness of bone. It’s more flexible and aims at reducing thigh pain. The stem is “75% less stiff than cobalt-chromium (CoCr) alloy stems and 50% less stiff than titanium alloy stems”.
DePuy, which has consolidated with Synthes, is apart of Johnson & Johnson Companies. Founded in 1895, DePuy was the first commercial orthopaedics company in the USA. In total, DePuy has more than 200 products used for joint replacement surgery.
- PINNACLE® Hip Solutions-- Offers a wide variety of shells and liners. They have porous coating options that allow for non-cemented, fixed-fit application that encourages stable bone attachment. They also offer their own “ALTRX Polyethylene” which is low wear plus an advanced ceramic option which they claim has “33 percent less volumetric wear than ALTRX Polyethylene Liners with cobalt chrome heads.”
- RECLAIM® Modular Revision Hip System-- Suited for moderate and complex hip surgery. This is a strong implant and in-house research showed that “600 million cycles of fatigue testing to demonstrate a superior construct strength profile.” Made of metal alloys.
- SUMMIT® Tapered Hip System-- Has been used for over 15 years and continues to be used today by trusted surgeons. Available in cementless and cement options. It’s porous material allows for natural bone growth. There are a variety of sizes and styles.
- ACTIS® Total Hip System-- A femoral component designed for tissue sparing, minimally invasive approaches (like anterior approach), as well as traditional approaches. Geared to offer greater stability, while preserving more natural bone.
- CORAIL® Revision Stem-- Another bone-conserving option instead of other modular revision systems. Suitable for primary and revision hip replacements. Designed for easy surgical installation, and to prevent thigh pain.
Knowledge is power, so the more you know about replacement types and styles, the deeper the conversation you can have with your care team about the best implant for you. In saying this, nothing is more important to your surgical outcome than working with a surgeon you trust and doing all you can to prepare yourself before surgery. Keep up the great research!