Hip and Knee Replacement: Cementless vs. Cemented Implants

The development of orthopedic implants have come a long way and so have the fixation options for these implants. There are two primary methods of fixation (adhering the implant to your bone): one uses bone cement and the other uses material that provides a surface to which bone can attach (cementless). Implants are designed specifically for either cementless or cemented fixation.  

Bone cement is a methylmethacrylate. It’s a very strong grout cement with some adhesive capabilities early in the fixation process. Cement fixation is immediate; it’s as good as it’s ever going to be immediately.

Notice the smooth interior surface of this femoral (thighbone) knee implant. The bone cement is applied, then placed onto your prepared thighbone. 

Cementless implants have either a textured, rough surface for your bone to grow on to, or a porous surface for your bone to grow in to. The implants are typically either scratch fit or pressfit implanted, meaning that the implant is driven into the bone very tightly, or is screwed or pinned in place. This keeps the implant “fixed” to the bone initially. Then, over time, the bone can grow on or in to the metal surface of the implant for long-term fixation. This bone in-growth can take a while to occur, perhaps more than a year for complete integration of the bone into the implant.

Notice the porous surface of the inside of this femoral (thighbone) knee implant. 

Cement fixation uses man-made acrylic bone cement to secure the implant to your bone; whereas, cementless fixation uses your biologic bone growth on or in to a coated or porous implant for fixation.

The advantage of using bone cement is that it can immediately achieve excellent fixation. And, if the surrounding bone isn’t good, say in a patient with osteoporosis or compromised bones, it’s a much better choice. However, there are additional surgical risks associated with the use of bone cement, and it can break or crack over years and can become loose.

The advantage of cementless fixation is that it’s more of a natural fixation. But, for cementless fixation, you need to have reasonably good bone quality with the ability for it to grow on to or in to the surface. Younger, healthier, and more active patients who typically have better quality bone are potential candidates for a cementless implant. The disadvantage is that there’s a possibility of fracture or subsidence of the implant and perhaps persistent pain until the implant has fully in-grown. 

In the USA, most hip replacements are cementless. However, patients with osteoporosis may still receive cemented implants if their doctor feels fixation could be compromised from the disease. Cement  is also more likely to be used in a hip fracture because the broken bone indicates that the bone may be weak. Sometimes we can use a combination, which is called a hybrid. Here, one component may be cemented and one may be cementless depending on the bone defects and quality. 

Hip replacement implants have improved significantly for cementless fixation. Many have titanium surfaces, which is bone-friendly. Some implants are manufactured with porous surfaces to mimic bone, providing a surface for bone to grow in to. However, there’s a chance of bone fracture at the time of implantation, and in the post-operative period, as well as subsidence and persistent pain until the in-growth occurs. Screws or pins may be added in some cases, giving additional early fixation.

In the USA, knee replacements have been primarily cemented. Though, there’s a growing trend towards cementless because of the benefits of biologic fixation. However, bone in-growth is difficult to achieve on the shinbone (tibia) component.

Improvements in implant designs and fixation methods have increased our use of cementless knee implants. Like in hip replacement, hybrid fixation is sometimes used with knee implants. The shinbone (tibia) may be cemented and the thighbone (femur) may be cementless.

The kneecap (patella) tends to be cemented. There are some cementless patella implants that have done well, but overall, many surgeons prefer to cement the patella component due to the high forces experienced on the kneecap. 

All of this, of course, is dependent on your individual deformity, bone quality, and finally your surgeon’s experience and preference. You and your surgeon should decide together what’s best for your particular situation, realizing that your surgeon is likely to have familiar implant experience that he/she uses regularly. Find an experienced surgeon to find out if you are a candidate for knee or hip replacement and discuss the options that you are interested in considering. While both cemented and cementless can be good options in experienced hands, it’s important for you to discuss all of the risks with both implants with your surgeon. Click here to find an orthopedic surgeon near you.