Application of 3D printing and topology optimization in rehabilitation medicine

Author: Wei Guoqiang, Chief Physician, Changzhi People's Hospital, Shanxi Province

Xu Yangyang, Chief Technician, Changzhi People's Hospital, Shanxi Province

Wang Yi, Chief Technician, Changzhi People's Hospital, Shanxi Province

Reviewer: Wang Pingzhi Chief Physician, Shanxi Bethune Hospital, Director of Rehabilitation Medicine Department, Member of Neurorehabilitation Group, Physical Medicine and Rehabilitation Branch, Chinese Medical Association, Chairman of Physical Medicine and Rehabilitation Professional Committee, Shanxi Medical Association

3D printing, also known as additive manufacturing, is a rapid prototyping technology that uses a variety of adhesive materials (inks) to construct objects layer by layer based on the created digital model files. 3D printing can quickly achieve "what you want is what you get". After the designer uses the computer to perform digital modeling, the input of the 3D printing device can quickly print out the prototype or product, which significantly shortens the design and production cycle.

The application of 3D printing in clinical medicine is divided into 3D bioprinting and 3D non-biological printing. The former refers to the printing of biologically active tissues and organs, while the latter is the printing that only realizes appearance and function. The biggest difference between the two is that 3D bioprinting involves cell participation, which can achieve more advanced life activities that are even close to normal human tissues and organs, and is the ultimate pursuit of 3D printing in the field of clinical medicine. At present, due to the limitations of technology and raw materials, most domestic rehabilitation medicine departments use 3D non-biological printing, but each work is unique, with accurate data, precise mechanical measurements, personalized design, brand-new appearance and good matching. With the development of science and technology, the application scope of 3D printing will become wider and wider.

Topology optimization (TO), as a computer-aided design method, is often used to design and manufacture various novel and complex structures with advantages such as adjustable stiffness, layered features and excellent lightweight performance.

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Coincidentally, the tissue development of many organ structures in the human body has also gone through the process of additive manufacturing and topological optimization. For example, bones are continuously deposited in key load-bearing areas, while gradually becoming sparse in non-load-bearing areas. Through repeated topological optimization, the bone structure is finally optimized and distributed in important load-bearing areas, achieving a perfect balance between strength and weight. Although the application of 3D printing technology in rehabilitation medicine is limited by proprietary materials, topological optimization can make up for this deficiency to a certain extent. The combination of 3D printing and topological optimization can effectively solve many problems in rehabilitation medicine.

In recent years, we have actively explored the application of 3D printing and topology optimization technology in rehabilitation medicine, mainly involving the following aspects:

1.3D Medical Model

It can be used for clinical teaching and surgical simulation, and can be restored, enlarged or reduced as needed. It has the characteristics of being objective, real, intuitive, touchable and able to be simulated.

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2. Orthopedic treatment

(1) Cervical fixation orthosis: It is personalized according to the injury and surgical conditions, easy to wear and quick to wear. The stability, comfort and range of motion can be adjusted at any time according to the course of the disease and the patient's needs. Topological optimization achieves lightweight and facilitates observation of the injury.

Production process:

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Wear

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(2) Toe orthosis: Collect foot images, perform biomechanical design after modeling, and customize orthotics to accurately correct toe deformities.

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(3) Lightweight fingerboard: The fingerboard is improved and adjusted to the shape to reduce weight and improve breathability.

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(4) Finger joint orthosis: used for interphalangeal joint and metacarpophalangeal joint deformities caused by rheumatoid arthritis, trauma, etc. It has a personalized design and can be adjusted in time.

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(5) Thumb and index finger stretch orthosis: It is used to stretch and correct hand contractures caused by stroke, nerve damage, etc. It is digitally designed and is beautiful, breathable, and comfortable.

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(6) Ankle-foot fixation orthosis: It can replace plaster and can be pre-installed with padding such as clothes and socks. It is easy to remove, breathable, lightweight after topological optimization, and easy to observe the injury.

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(7) Elbow joint fixation orthosis: It replaces traditional plaster and can be pre-installed with clothing padding. It is easy to remove, breathable, lightweight after topological optimization, and easy to observe the injury.

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(8) Thoracolumbar fixation orthosis: lightweight after topological optimization, making it easier to observe the injury.

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(9) T-shoe orthosis: It can be used to treat internal and external rotation deformities of the lower limbs in patients with stroke, lower limb fractures, etc. The heel device can be used to adjust the angle.

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(10) Orthopedic insoles: personalized design, topologically optimized, can adjust the height and stiffness of the arch, sole and toes at any time to achieve orthopedic treatment.

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3. Improved tools

Design and improve tools and equipment suitable for patients and therapists.

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3D printing technology has the following advantages: personalization, good fit, high precision, short manufacturing cycle, light structure, good breathability, good waterproof design, preset padding, fast iteration and update, good permeability (easy to observe), and can be adjusted at any time according to patient response or changes in condition. At the same time, there are also the following shortcomings: first of all, the material is lacking in printing materials that take into account comfort, firmness, and durability. Although topological optimization can make up for the lack of certain rigidity and elasticity, the poor comfort is still not conducive to long-term wear; in addition, there are also problems such as difficulty and high cost in post-professional processing (smoothness, process). With the advancement of materials science and the integration of new technologies, technologies such as 3D printing and topological optimization will bring about rapid changes in rehabilitation medicine.