When is knee prosthesis surgery necessary, and what are the results?

The goal of knee prosthesis surgery, or knee arthroplasty—the replacement of articular surfaces with artificial metallic and polyethylene implants—is to restore the joint's shape and alignment, restore its stability and mobility, and eliminate pain as much as possible. The fundamental indication for total knee arthroplasty (TKA) is pain. While functional disability and severe deformities are important factors, pain is the symptom that most often brings the patient to the doctor.

 

The "ideal" surgical candidate experiences moderate or severe pain during normal daily activities and possibly at rest. The pain is chronic, progressive, and resistant to all conservative treatment methods. A decreased range of motion generally accompanies a painful knee. While loss of mobility alone is not an indication for knee prosthesis, knee stiffness can be debilitating, especially in patients with polyarticular involvement. In these cases, arthroplasty may be indicated even if pain is mild or absent.

 

Angular deformities in valgus or varus (knock-knee or bowleg) (Figure 2) can be an important factor but must be assessed according to the degree of deviation in the frontal plane, as well as the association with pain and instability. Aesthetic appearance should not be considered in the indication for a knee prosthesis.

 

How to further increase patient satisfaction?

One goal of the prosthesis is the return of sufficient knee movement to avoid limiting daily activities. This includes full knee extension and flexion of at least 120 degrees. Individuals with significant knee stiffness before surgery are more likely to not regain a full range of motion. Yet, the vast majority of patients experience excellent pain control and good function after surgery. To increase patient satisfaction undergoing knee arthroplasty, experts have developed new surgical techniques involving the creation of custom-made knee prostheses, which greatly increase patients' motor capacity post-surgery.

 

In which cases is a custom-made knee prosthesis particularly indicated?

The ideal candidate is relatively young, often suffered ligament or meniscus injuries around age 20, is motivated to continue sports after surgery, and does not have excessive overweight. Once clinical and radiographic feasibility is verified, the patient undergoes a 3D scan about 30 days prior, on which the prosthesis to be printed is designed. After manufacturing, the prosthesis will undergo conventional testing before implantation. The patient will then have a uniquely custom-built, 3D-printed knee.

 

What are the benefits of a custom-made knee prosthesis for the surgeon and the healthcare team?

The perfect adherence of the prosthesis to the patient's bone morphology allows for much better results in recovering knee function. This type of implant allows for greater preservation of bone tissue, reduced blood loss during surgery, reduced surgery time, and consequently reduced septic risks. The innovation lies in the personalization of the implant: the scan performed on the patient is transmitted to the manufacturer, who constructs the prosthesis, along with the accompanying instrumentation, in 5 to 6 weeks, as if it were a bespoke suit. This innovation allows a significant step forward in the field of knee arthroplasty, as standard prostheses fail to adapt optimally, which has consequences for knee function. In addition to the benefits for the patient, implant personalization allows for better process management, as only the necessary devices are produced.

 

Is this type of prosthesis stronger? More durable?

Partial or total knee arthroplasty is an intervention certainly linked to the degree of knee wear, that is, the degree of osteoarthritis, i.e., the disappearance or degeneration of the cartilaginous part.

 

The choice of implant type is linked to several factors such as:

• bone quality;
• type of deformity;
• ligament functionality;
• patient weight;
• type of joint movement;
• expectations;
• patient's lifestyle;

This procedure has seen considerable growth in recent decades, becoming one of the most widely performed procedures in orthopedic surgery worldwide. Implantation of a custom-made knee prosthesis in a high-demand subject, athletes, or patients who, in any case, require a different lifestyle—for example, frequent squatting (either for work or social or religious habits)—will be less "comfortable" in the immediate postoperative period, but over time, it will allow for great muscular strength associated with adequate ligament stability, fundamental conditions to meet the patient's high functional demand. This type of operation is mainly indicated to eliminate arthritic degeneration of the joint and presents considerable advantages.

• pain elimination;
• improved functionality;
• resumption of physical and sports activities (except contact sports and jumping);