Updated January 01, 2014.

Knee Replacement Surgery:

Knee replacement surgery is the last resort treatment for patients with severe knee arthritis. A new type of knee replacement that has received attention is called a 'custom knee replacement.'

A knee replacement implant has three basic parts called components. The tibial component of the knee replacement sits on top of the shin bone. The femoral component fits on the end of the thigh bone.

Between these metal implants is a plastic component called the spacer.

Custom Knee Replacements:

A custom knee replacement is similar to standard knee implants in that the same types of parts are used as described above. The difference with the custom knee replacement is that, prior to undergoing surgery, the patient has an MRI of the knee. Specially designed cutting guides are then made for the patient, which help the surgeon remove a precise amount of bone at specific angles to accept the knee replacement implant. The hope is that by customizing the cuts made to fit the knee implant, the surgeon will be able to remove less normal bone and more reliably correct alignment problems within the knee.

Custom Replacements Do Not Use Custom Parts:

I do find it misleading to call this a custom knee replacement. Many patients believe the actual knee replacement implant used will be custom fit to their knee. That is not the case.

The only custom part of a custom replacement is the guide that helps your surgeon make precise bone cuts.

The rest of the knee replacement is the same as a standard knee replacement. While the guides used to place the implants are custom made, the actual implants are not custom made for you.

Benefits of a Custom Knee Replacement:

There certainly are possible benefits of a custom knee replacement system. These include more limited trauma to the knee by possibly removing less bone. Also, because the alignment is custom made for your knee, less work has to be done at the time of surgery to determine alignment and ensure the knee implant will be properly positioned. Some surgeons feel that the operation can be done more quickly, with less soft-tissue disruption. The hope for the long-term is that if the implants of a knee replacement can be placed more accurately, they may last longer by not wearing out as quickly.

Is a Newer System Better?:

While manufacturers want their knee replacements to be improvements, newer models do not always turn out to be better. Many knee replacements have been pulled off the market, even years after being introduced, because they were found to be worse than knee replacements that have been used for a longer time.

That is not to say that older style knee implants are the best we can do. But we should be cautious about thinking or hoping that a design change will lead to better results, as it does not always work out that way.

Bottom Line: Custom Knee Replacement Thoughts:

I think the custom knee replacement is an exciting development in knee replacement surgery. There are two things I think patients should understand about custom knee replacements:

• The implant itself is not custom made for you. Only the tools used to guide the bone cuts around the knee are custom made to fit you specifically.
• There is no data to show that this system is any better than other knee replacements your doctor may recommend. In fact, some doctors may argue there is not enough data to yet recommend this system over other systems that have longer-term results.

<sub>Sources:

Howell, SM, et al. "Results of an Initial Experience with Custom-fit Positioning Total Knee Arthroplasty in a Series of 48 Patients" Orthopedics 2008; 31:857.</sub>