Hip Implant Types and Materials: Bearings, Fixation, and What Goes In

A modern hip implant is really three parts working together: a metal stem driven into your thigh bone, a ball that sits on top of it, and a cup that lines the socket, with the ball and cup forming the smooth bearing that lets the joint glide. When my surgeon first said “ceramic head, cross-linked poly, uncemented cup”, I nodded as if that meant something. It did not, not then. So here is the plain version I went home and pieced together, because knowing what was about to be put inside me made the whole thing feel less like a mystery and more like a decision I was part of.

The three parts that replace your hip

A total hip replacement does not swap out one lump for another; it rebuilds the joint from a few pieces. The worn ball at the top of your thigh bone (the femoral head) is removed, and a stem is fitted down inside the bone with a new ball on top. The worn socket in your pelvis (the acetabulum) is reshaped and lined with a cup, often with a separate liner clipped inside it ¹. Osteoarthritis, the wear of the joint cartilage, is the most common reason this is needed in the first place ².

What surprised me is how much of the result comes down to two questions about those parts: what the gliding surfaces are made of, and how the pieces hold to my bone. Everything else is detail. I have written the wider picture of hip replacement surgery if you want the whole operation rather than the hardware.

The bearing: the surfaces that glide

The bearing is the heart of the implant: the ball and the inside of the cup, the two surfaces that rub against each other thousands of times a day. This is where material choice matters most, because wear here is the main thing that limits how long a hip lasts ³. The two mainstream combinations are ceramic-on-polyethylene and metal-on-polyethylene: a ceramic or metal ball running inside a tough plastic liner.

That plastic is not the brittle stuff you picture. It is highly cross-linked polyethylene, a hard, slippery, heavily engineered material that wears far more slowly than the older plastics did, which is a big part of why modern implants last as long as they do ³. Mine is a ceramic ball on a cross-linked plastic liner. The honest truth is that most people will never feel which bearing they have. Day to day, a well-made ceramic-on-plastic and a well-made metal-on-plastic hip behave the same.

Ceramic, metal, and the choice between them

If you are offered a choice, here is the comparison in plain terms. Ceramic balls are extremely hard and smooth, resist scratching well, and cannot release metal ions, which is why surgeons often favour them, particularly in younger or more active patients ¹. The trade-off is small but real: ceramic can very rarely chip, and a tiny number of people notice an occasional squeak.

Metal balls (a cobalt-chromium alloy) on plastic are also long-proven and slightly more forgiving to handle, with no risk of ceramic fracture. Neither is a wrong answer. What I would not lose sleep over is the title for “best material”, because the registries show both bearings performing strongly over many years ³. When I raised it, my surgeon’s reasoning was about my age and activity, not a league table, and that is the conversation to have. My list of questions to ask your hip surgeon includes how to ask about this without feeling out of your depth.

Why metal-on-metal fell out of favour

You may read about metal-on-metal hips, where both the ball and the cup were metal, and wonder why no one suggested it. For standard total hip replacement these are now rarely used ¹. Some designs released fine metal particles as they wore, which could irritate the surrounding tissue and raise metal levels in the blood, leading to extra monitoring and, for some people, an earlier revision than expected.

I mention it not to alarm anyone but because it is the one material question worth being clear on: if a hip is being discussed today, the bearing will almost always involve ceramic or metal running against cross-linked plastic, not metal against metal. If you had a metal-on-metal hip fitted years ago and it is comfortable, that is a conversation for your own surgeon, not a reason to panic.

Fixation: cemented or uncemented

Fixation is the second big question: how the stem and cup actually hold to your bone. There are two well-proven answers. Uncemented parts have a rough, often porous coating that your own bone grows into over the weeks after surgery, gripping the implant like roots; this suits denser, healthier bone, which is why it is common in younger patients ⁴. Cemented parts are fixed with an acrylic grout (bone cement) that sets within minutes and grips immediately, which can suit softer or more fragile bone, often in older patients.

What no one told me until I asked: surgeons frequently mix the two, cementing one component and not the other (a “hybrid” hip), and this is normal good practice, not a compromise ⁴. Both approaches give excellent fixation with decades of registry support behind them. As with the bearing, the choice is matched to your bone and your surgeon’s experience rather than one being plainly better.

How much the material really decides

Here is the reassurance no one handed me earlier. Whatever combination ends up in you, the destination is good: modern hip implants typically last 15 to 25 years, with around 90 to 95% still in place at 10 years, and roughly 6 to 8 in 10 still working at 25 years in large pooled studies ⁵. The materials are part of why those numbers are so strong, but within today’s mainstream options the differences are modest.

So I would put your energy where it counts. The bearing and fixation are worth understanding and worth one good conversation, but they are rarely the thing that decides your result. Your surgeon’s experience, the operation going smoothly, and the recovery you put in matter at least as much. Knowing what was going inside me did not change which implant I had; it changed how I walked into the day, which was steadier and far less afraid.

This is general information from a patient’s perspective, not medical advice. Implant choice depends on your individual anatomy, bone quality, age, and activity, and only a qualified surgeon who can assess you can recommend the right components for your hip.