I had a partial knee replacement last year. But within six months, the thing had come loose and I had a bone fracture just above the implant in the tibia. I’m wondering if the surgeon had used a different brand of implant (there were three to choose from) if I would have had a better result.

Joint implants (an implant is also called prosthesis) continue to improve in design and materials. Surgical techniques and tools have also been improved over the years. More and more implants are now available with different design features.

The best implant for you may depend on whether you have strong, stable knee ligaments (or not). Some implants are made with a more porous surface to allow better bone growth around them. This type may not require the use of cement to hold it in place.

Because there are so many competing manufacturers and designs, research comparing them is fairly limited. But there was a recent study in Norway where the results of over 1300 different implants were gathered and analyzed.

The authors of this study compared outcomes for the unicompartmental versus the total knee replacement. As the name suggests, with a total knee replacement (TKR), the surgeon removes the entire damaged knee joint and replaces both the upper and lower sides of the joint.

The unicompartmental arthroplasty (UKA) involves just replacement of the inner or outer half of the joint. Most patients having a UKA have problems with knee alignment and have worn out just the medial joint surface. Medial refers to the side closest to the other knee.

Norway has an established registry for arthroplasties (implants) making this type of comparison possible with a large number of patients. All patients having any artificial joint implants in Norway are registered. Information about their diagnosis, age, joint involved, and surgery performed is included in the database. Baseline pain and function are not part of the registry information, so patients selected to be in the study were sent a survey of questions by mail.

Patient selection was based on current age (less than 85 years) and when the surgery was done (at least two years ago). Differences in results were compared by implant type and brand, patient age, sex (male versus female), and time since the operation.

As shown in previous studies, the unicompartmental knee arthroplasty did have more favorable results with less pain and better function at all time points. But the differences weren’t all statistically significant. And when asked about quality of life, patient ratings were equal between the two groups.

The authors took a closer look at various implant brands (i.e., made by different manfacturers). Again, there weren’t significant differences among the three prostheses included. One difference that did stand out was based on sex. Men with unicompartmental arthroplasties (UKAs) had less pain and better knee motion and function compared with women who had the same implants. The men also had better scores for function based on daily activities, sports, and recreational activities.

There could be any number of reasons why your implant came loose. The fracture as a second complication may (or may not) have been related to the implant loosening. Studies are needed to compare implants and determine patient factors that might suggest one type (design) or brand would be best suited for each individual person.