Apr 12, 2016 | By Benedict

A group of researchers has developed a new, low-cost method for studying knee pain and immobility caused by abnormal movement of the patella. The method used a realistic 3D printed model knee and 3D printed navigation system.

There are numerous ways in which knees can malfunction, causing pain and problems with movement. When the knee flexes and extends, the kneecap should slide, or “track”, evenly. However, problems with muscular control and other, generally unknown structural problems can cause uneven patellofemoral tracking, which is stressful to the knee and can cause serious problems for the patient. Unfortunately, the physiology of the knee is far from fully understood, so medical researchers are constantly looking for new and innovative techniques through which they can learn more about patellofemoral tracking and the causes of uneven tracking, or “maltracking”.

Medical researchers can perform experiments on living patients, but there are problems associated with doing so. Patellofemoral tracking can, for example, be monitored with external apparatus. However, data acquired with the appropriate motion-tracking system can be influenced and skewed by the relative movement of markers on the skin. This causes errors in the recorded data, resulting in less useful findings. Alternatively, apparatus can be attached directly to the bone, but this can be harmful to the patient, with tests showing reduced knee stability following the procedure. 3D printing could potentially offer a solution to these problems. If a suitably lifelike knee model can be built, a human patient would not be required, and the problems associated with in vivo and in vitro research could be eliminated.

In a research paper titled “A Novel Approach for Patellofemoral Tracking Using a Knee Model Reconstructed with a Three-Dimensional Printer,” researchers Gian Luca Gervasi, Roberto Tiribuzi, Anastasios Georgoulis, Giuliano Cerulli, and Marco Freddolini document their 3D printer-assisted research, which could help doctors to better understand how the knee works, as well as going some way to eliminating the need for cadavers in medical experiments on knee function. According to the paper’s abstract, the study “proposes a new approach to evaluate…patellofemoral tracking using a knee model composed of femur, tibia, and patella reconstructed with a three-dimensional (3D) printer.”

To create a 3D printed model knee with which they could evaluate patellofemoral tracking, the researchers first had to obtain a digital 3D model of a human knee. To do so, they used an MRI scanner to capture image data of a control patient’s healthy knee. Once this data was obtained, the team used ITK-SNAP software to divide the model into segments, before processing it into a lifelike 3D model using FreeCAD. This 3D model was then converted into STL format using the Repetier-Host software native to the group’s MakerGear RepRap Prusa FDM 3D printer. The knee model was printed in PLA, with an infill of 50% and a layer thickness of 0.2 mm. To create realistic knee movement, a polyvinylchloride cord was used to simulate the quadriceps tendon.

The 3D printed knee model was a success. It was fixed to a tensile test machine and subjected to four static tests, performed by applying a 200N load through the cord at various angles of knee flexion, mimicking the possible causes of maltracking. The position of the 3D printed patella was then measured using a 3D printed, custom-made navigation system, which showed both the “mediolateral displacement” (how much the patella moved “off track”) and the “lateral tilt” (how much it angled sideways) of the 3D printed model to be consistent with the knee movement of cadaveric specimens, i.e., the knees of corpses.

The researchers believe that their 3D printed model and navigation system could be used as an alternative to the problematic in vivo and in vitro methods presently employed: “In summary, the results demonstrated that the low-cost knee model reconstructed with the 3D printer machine closely simulates the patellar behavior at different knee flexion angles of an in vitro cadaveric specimen,” they explain in the conclusion of their study. “Our custom-made model could be used by researchers to overcome the limitation of in vivo and in vitro patellofemoral kinematic analysis and by clinicians to evaluate a tailored surgical treatment for each patient.”

The paper has been published in the journal 3-D Printing and Additive Manufacturing, where it is free to download online.

 

 

Posted in 3D Printing Application

 

 

Maybe you also like:


   






Leave a comment:

Your Name:

 


Subscribe us to

3ders.org Feeds 3ders.org twitter 3ders.org facebook   

About 3Ders.org

3Ders.org provides the latest news about 3D printing technology and 3D printers. We are now seven years old and have around 1.5 million unique visitors per month.

News Archive