Custom-made implants for the most demanding needs—that’s what patient-specific knee prostheses are all about. PD Dr. med. Erhan Basad uses a case study to explain the applications and unique features of these custom-made prostheses produced using 3D printing. You’ll also learn everything about the surgical technique.
Soccer, cycling, skiing—Peter Schneider, 58, has always been an active person. Since the age of 17, the banker from Frankfurt has suffered from various knee injuries.
Arthroscopic procedures provided relief for many years. In recent years, however, he developed knee osteoarthritis (gonarthrosis) with pain that could no longer be managed. Doctors now recommended a total knee replacement (TKR).
The athletic banker is hesitant because he fears a loss of mobility and physical limitations after the surgery.
© artstudio_pro / Fotolia
Osteoarthritis develops when the joint cartilage is damaged, causing the bones to rub against each other during movement and under stress.
According to PD Dr. Basad, the causes are:
In the early stages, physical therapy and joint-preserving surgeries can help.
Advanced knee osteoarthritis can be successfully treated with a total knee replacement (endoprosthesis).
The first step involves shaping the joint surfaces. The surgeon then secures the implants to the surfaces of the thigh and lower leg. This prevents the painful rubbing of the cartilage-free joint surfaces against each other.
The better the patient’s overall health, the faster they can regain their quality of life and activity level after surgery.
One of the most challenging issues following knee replacement surgery is regaining muscle strength and mobility.
In the long term, the durability of a knee replacement depends on mechanical and biological factors.
For example, an imperfect fit of the implants or being overweight are among the risks that can lead to loosening.
A knee prosthesis can help patients regain their quality of life. In Peter Schneider’s case, a patient-specific knee implant was the appropriate solution.
“This implant is ‘custom-made’ and restores the individual’s anatomy,” explains Heidelberg knee expert PD Dr. Basad. “Conventional endoprostheses come in ‘off-the-shelf sizes’ based on average shapes. The individually adapted implants, on the other hand, are custom-made.”
The size, shape, and axes of the knee prostheses are taken into account during the manufacturing process. As a result, the implants and bones fit together perfectly.
Computer-assisted techniques help with joint implants by facilitating planning and enabling the individual (personalized) fabrication of implants.
Custom implants manufactured using CAD/CAM technology replicate the natural geometry of the knee joint and allow for significantly better positioning. The system is used to treat knee osteoarthritis.
This treatment is indicated in cases of particularly complex anatomical conditions or when the patient has high performance expectations.
© alexonline / Fotolia
To create a custom knee implant, doctors first take a virtual 3D scan using computed tomography. Experts in Boston (USA) then use specialized computer programs to determine the optimal shape.
There, 3D printers manufacture the knee prosthesis along with the corresponding surgical instruments for each individual patient.
“The instruments are milled to fit the patient’s bones precisely. This ensures that bone preparation is performed safely and without error. The templates include all the dimensions and axial corrections necessary for a perfect implant placement,” explains Dr. Basad, describing the surgical technique.
Just a few days after the surgery, Peter Schneider was able to walk on his own and already bend his knee 90 degrees.
“The feeling of walking after the surgery felt really familiar. Once the initial postoperative pain subsided, I felt confident my joint could handle almost anything,” says the enthusiastic athlete, emphasizing: “Not long after the surgery, I was already riding my bike and playing golf again.”
According to the surgeon, it should be noted that such rapid recovery is only possible if the patient was physically active beforehand.
Dr. Basad also prefers to carefully explain to patients: “Adapting to the new material, the altered biomechanics, and the regained mobility can take several months.”
© elnariz / Fotolia
Which knee patients need a knee replacement?
In general, a knee prosthesis should only be used when joint-preserving measures are no longer sufficiently effective.
In the early stages of osteoarthritis, these include:
Before deciding on joint replacement, doctors must determine whether a total or partial replacement is appropriate.
In cases of medial or lateral knee osteoarthritis, a less invasive partial replacement using a sled prosthesis is possible.
A customized implant can account for patient-specific characteristics and preserve bone. Every knee is as unique as the person. Therefore, every patient can benefit from a custom-made implant.
It’s not just the precise fit without any overhang that’s important; the implant also covers all exposed bone surfaces.
Sliding prostheses offer an additional advantage: The implant harmonizes with the glide-like shape of the preserved joint component. As a result, the joint moves just as it did when it was healthy.
In principle, the surgery proceeds similarly to the implantation of a standard prosthesis. However, the implants and instruments are manufactured specifically for the patient. Doctors have already successfully simulated the surgery using a 3D model on the computer.
A surgical planning sketch is used to guide the surgical technique. This sketch outlines all necessary steps, including the respective resection heights and angles. This allows doctors to confirm the correct positioning of instruments and implants during the surgery.
Regarding the instruments, it is particularly worth noting that the customized saw guides are precisely adapted to the bone. Each resection therefore requires individual monitoring during the surgery.
Thanks to preoperative navigation and the alignment specified in the guides, the intraoperative steps are reduced and technically simplified.
Osteoarthritis develops when the articular cartilage is damaged, causing the bones to rub against each other during movement and under load.
Causes include:
In the early stages, physical therapy and joint-preserving surgeries can help, such as:
Advanced knee osteoarthritis can be successfully treated with total knee replacement (endoprosthesis).
Conventional endoprostheses come in “one-size-fits-all” sizes based on average shapes.
Computer-assisted techniques help to manufacture joint implants individually (personalized). They adapt to the patient’s anatomy and help conserve bone and reduce blood loss during surgery.
For over 14 years, we have had access to the system presented here—a system that has been used tens of thousands of times worldwide and offers truly customized prosthetics.
CAD (Computer-Aided Design) technology enables preoperative navigation that identifies anatomical problems and potential solutions at an early stage.
Clinical results have validated the system’s effectiveness in terms of fit, blood loss, safety, and cost-effectiveness.
Surgeries on the knee joint are performed by specialists in orthopedics and trauma surgery.
Typically, these doctors specialize in a specific joint, such as the knee. They therefore have extensive experience in diagnosing all possible conditions and performing the appropriate treatment.
Therefore, be sure to consult a proven specialist in knee surgery.
Every physician listed in the Leading Medicine Guide has attained the highest level of training and certification within their respective medical specialty society. Furthermore, we contacted this physician based, among other factors, on their case volume (surgeries, treatments, and therapies), which we determined by cross-referencing various publicly available sources. Following discussions with the selected physicians and the directors of the medical facilities, as well as a subsequent internal review, they were admitted to the Leading Medicine Guide.
The quality assurance of the Leading Medicine Guide is further ensured by 8 admission criteria. Each member must meet at least 6 of them:
