A Swedish teenage girl was facing a lifetime in a wheelchair because of a congenital disease that left her with a severely deformed left hip joint. Her painful condition forced her to be home schooled. With the 3D-printed hip implant and virtual planning in Materialise’s Mimics and 3-matic software, she is now pain-free, walking without crutches and going back to school like a normal teenager.
Virtual design of tri-flange patient-specific cup
Reconstructing the Pelvis Deformation in Mimics®
Since childhood, a 15-year old Swedish girl was suffering from neurofibromatosis, a congenital disease also known as ‘Von Recklinghausen’s disease’, which caused a severe skeletal deformation of the left hip because of a neurofibroma that destroyed her pelvis, which was causing a lot of pain. In 2010, the neurofibroma was surgically removed. After a femur fracture a few months later, her situation took a turn for the worse, forcing her to leave school to be home educated for the next 2 years. Her doctors initially saw very limited or no treatment options for her hip and she was looking at a life in a wheelchair.
In 2012, Professor Rydholm from Skane University Hospital in Lund, Sweden, contacted Materialise subsidiary Mobelife and their team of engineers set to design a custom acetabular implant. To this end, they imported and segmented the patient’s CT scan in Mimics to reconstruct the defect and analyze the pre-operative situation. Based on anatomical templates, a surgical planning was made directly on the patient’s anatomy. This involved placing landmark points and determining the position of the acetabular cup and flanges to secure the cup in the best position, with the surgeon’s blessing.
FEA simulation of the triflange cup
Designing a Patient-Specific Acetabular Implant in 3-matic®
FEA simulation of the triflange cup
Using 3-matic, an implant was designed to match the anatomy of the patient’s hip, providing a perfect fit. The software facilitates an accurate evaluation of the screw and implant positioning. The patient-specific flanges were designed in 3-matic and the location for the screws was determined. To support screws, the bone has to be in a sufficiently good condition, so bone quality was analyzed using, amongst other techniques, the grey values of the CT data in Mimics. In addition, a Finite Element Analysis (FEA) was performed to verify whether the implant and bone assembly will withstand the forces and stresses in the hip joint. The final design was verified by the surgeon and exported for 3D Printing. The patient-specific ”triflanged cup” was manufactured in titanium by LayerWise.
Shortly after, the 3D-printed titanium implant was delivered to the hospital in Sweden and the girl underwent surgery. Almost immediately afterwards, she was pain-free. A few months later, she was out of her wheelchair and walking with just one crutch. Now, about one year and a half after the surgery, she is going to school again and this without crutches!
The Standard in ‘Engineering on AnatomyTM’
The Mimics Innovation Suite turns 3D image data into high-quality digital models in an accurate and efficient way. Starting from CT, MRI or 3D ultrasound images, the Mimics Innovation Suite offers the most advanced image segmentation, the broadest anatomical measurement options, powerful CAD tools for Engineering on Anatomy and 3D Printing, and accurate model preparation for FEA and CFD.
The authors used the Medical edition of the Mimics Innovation Suite to design a patient-specific acetabular implant using following steps:
- Convert CT images of a hip joint to digital models
- Design of a patient-specific acetabular implant (triflange cup) directly on anatomical data
- Export the design for FEA and 3D Printing
The aMace implant is a custom-made medical device per European definition and conforms to Annex VIII and essential requirements of Annex I of the Council Directive 93/42/EEC. The implant is not commercially available in the US.