Expert consensus on the design, manufacture, materials, and clinical application of customized three-dimensional printing scoliosis orthosis

Dezhi Lu; Tao Li; Wenqiang Yu; Haiyang Feng; Yuanjing Xu; Zhenjiang Ma; Jun Tan; Guoqi Niu; Pengfei Zheng; Ying Xiong; Hongbo Zhang; Feng Li; Rui Zhu; Zhao Mei; Yu Zhang; Dongming Liu; Xiaofeng Nan; Jinwu Wang; Kerong Dai

doi:10.4103/digm.digm_34_21

EDITORIAL

Year : 2022 | Volume : 8 | Issue : 1 | Page : 2

Expert consensus on the design, manufacture, materials, and clinical application of customized three-dimensional printing scoliosis orthosis

Dezhi Lu¹, Tao Li², Wenqiang Yu³, Haiyang Feng³, Yuanjing Xu⁴, Zhenjiang Ma⁵, Jun Tan⁶, Guoqi Niu⁷, Pengfei Zheng⁸, Ying Xiong⁹, Hongbo Zhang¹⁰, Feng Li¹¹, Rui Zhu¹², Zhao Mei¹³, Yu Zhang¹⁴, Dongming Liu¹⁵, Xiaofeng Nan¹⁶, Jinwu Wang⁵, Kerong Dai⁵
¹ Department of Orthopaedic Surgery, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine; School of Medicine, Shanghai University, shanghai, China
² Department of Orthopaedics, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China
³ School of Rehabilitation Medicine, Weifang Medical University, Weifang, Shandong, China
⁴ School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
⁵ Department of Orthopaedic Surgery, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, shanghai, China
⁶ Department of Surgery, United Family Healthcare, Shanghai, China
⁷ Department of Spinal Surgery, The Second Affiliated Hospital of Bengbu Medical College, Bengbu, Anhui, China
⁸ Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing, Jiangsu, China
⁹ Department of Orthorpaedics, Yan'an Hospital Affiliated to Kunming Medical University, Kunming, Yunnan, China
¹⁰ East China University of Science and Technology, Shanghai, China
¹¹ Tongji Hospital, Tongji Medical School, Huazhong University of Science and Technology, Wuhan, Hubei, China
¹² Department of Orthopedics, Division of Spine, Tongji Hospital Affiliated to Tongji University School of Medicine, Shanghai, China
¹³ Huazhu Medical Technology (Shanghai) Co., Ltd., Shanghai, China
¹⁴ Shanghai CoinRobotics Technology Co., Ltd., Shanghai, China
¹⁵ Wanhua Chemical Group Co., Ltd, Shanghai, China
¹⁶ Nan Xiaofeng's Spinal Orthopedic Workshop, Xi'an, Shaanxi, China

Date of Submission	09-Aug-2021
Date of Decision	01-Oct-2021
Date of Acceptance	20-Aug-2021
Date of Web Publication	25-Jan-2022

Correspondence Address:
Jinwu Wang
Room 701, No. 3 Building, 639 Zhizaoju Road, Shanghai 200011
China
Kerong Dai
Room 701, No. 3 Building, 639 Zhizaoju Road, Shanghai 200011
China

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/digm.digm_34_21

Abstract

The digitalization of medicine promises great advances for global health. Combined with three-dimensional (3D) printing technology, noncontact optical scanner, and computer-aided design, we can make personalized 3D printing scoliosis orthosis for patients across the country – with better diagnostics, personalized treatments, and early disease prevention. We hope optimize the production process of scoliosis orthotics, improve the production efficiency of orthotics, and promote the clinical transformation of 3D-printed scoliosis orthosis. To standardize the design, manufacture, materials, and clinical applications of 3D printing technology in the scoliosis orthosis, Chinese experts in relevant fields were organized to formulate this expert consensus.

Keywords: Clinical application, Expert consensus, Orthosis, Scoliosis, Three-dimensional printing

How to cite this article:
Lu D, Li T, Yu W, Feng H, Xu Y, Ma Z, Tan J, Niu G, Zheng P, Xiong Y, Zhang H, Li F, Zhu R, Mei Z, Zhang Y, Liu D, Nan X, Wang J, Dai K. Expert consensus on the design, manufacture, materials, and clinical application of customized three-dimensional printing scoliosis orthosis. Digit Med 2022;8:2

How to cite this URL:
Lu D, Li T, Yu W, Feng H, Xu Y, Ma Z, Tan J, Niu G, Zheng P, Xiong Y, Zhang H, Li F, Zhu R, Mei Z, Zhang Y, Liu D, Nan X, Wang J, Dai K. Expert consensus on the design, manufacture, materials, and clinical application of customized three-dimensional printing scoliosis orthosis. Digit Med [serial online] 2022 [cited 2023 Mar 24];8:2. Available from: http://www.digitmedicine.com/text.asp?2022/8/1/8/336593

Introduction

Adolescent idiopathic scoliosis (AIS)^[1] is a relatively common spinal deformity in adolescents, with structural changes of the spine in the coronal plane with abnormal curvature, accompanied by rotation of the vertebrae, causing the loss of the original curvature of the spine.^[1],[2] The etiology of which is not yet clear.

The use of scoliosis orthosis for AIS treatment originated in the 1930s and 1940s. Over the past few decades, some studies have confirmed that the natural history of AIS can be positively affected. The Scoliosis Research Society (SRS) established the inclusion criteria for orthosis treatment in 2008, which aims to provide a unified subject inclusion criteria and efficacy evaluation methods for orthosis treatment studies, and the International Society for Scoliosis Orthopaedic and Rehabilitation Treatment (SOSORT) established standards for the management of idiopathic scoliosis orthosis in consensus, aimed at minimizing care requirements while maximizing efficacy and compliance to treatment.^[3],[4],[5]

In recent years, the introduction of three-dimensional (3D) printing, also known as additive manufacturing, has shown great potential for obtaining patient-specific solutions in the medical field. This technology is capable of constructing complex custom structures based on digital models. Several 3D printing technologies have been used for medical applications, such as polyjet modeling (PJM), selective laser sintering (SLS), Stereo Lithography Appearance (SLA)^[2] and fused deposition modeling (FDM). Higher equipment costs (especially SLS and PJM) and processing time are the main limiting factors for the production of large orthopedic devices using 3D printing. Among these 3D printing technologies, FDM is the most suitable and least costly method to produce scoliosis orthosis, despite its slightly lower dimensional accuracy.^[6] 3D-printed scoliosis orthosis is environmental-friendly, not only generating limited waste but also requiring no tooling; each component can be customized and reproduced without additional preparation costs. Fewer manual operations are required, thereby reducing the risk of human error and increasing interoperator repeatability. With the development of computer-aided design technology, 3D printing combined with finite element and topology optimization techniques allows for the design of more biomechanical, lightweight, and esthetically pleasing orthosis. More and more 3D-printed scoliosis orthoses are being used to treat patients.

Since 3D-printed scoliosis orthoses are designed based on specific patient needs and are highly individualized with a small number of products, preclinical and clinical trial studies cannot be conducted according to the sample size requirements of standardized medical devices, and therefore, the regulatory and registration systems applicable to standardized medical devices are no longer fully applicable to 3D-printed scoliosis orthosis.^[7] To date, several countries have introduced regulatory regulations and guidance documents for customized additive manufacturing medical device products. The US Food and Drug Administration first issued draft guidelines for 3D-printed medical devices in May 2016. The 3D Printing Medical Device Manufacturing Guidance was published on December 4, 2017. 3D printing as a new technology is applied to the production of scoliosis orthosis; the development of its related standards is also an urgent matter to be resolved. The development of this standard can provide reference for the domestic application of 3D-printed scoliosis orthosis and further improve the existing laws and regulations for rehabilitation aids.

Definition and Classification of Three-Dimensional Printing Scoliosis Orthosis

Definition

Part or all of the external spine orthopedic device formed by digital 3D printing is mainly used to correct scoliosis to achieve the purpose of controlling and improving scoliosis deformity.

Classification

According to the anatomical position (such as neck, chest, waist, and sacrum),^[8],[9],[10] it can be divided into the following categories.

Customized three-dimensional printing cervicothoracic lumbosacral orthosis

Using customized additive manufacturing technology, including human cervical spine, thoracic spine, lumbar spine, and pelvis, it is suitable for cervical thoracic or cervical scoliosis with lumbar.

Customized three-dimensional printing thoracolumbar and sacral orthosis

Using customized 3D printing technology, including the thoracic spine, lumbar spine, and pelvis of the human body, it is suitable for thoracic or thoracic and lumbar scoliosis deformities.

Customized three-dimensional-printed lumbosacral orthosis

Using customized 3D printing technology, including the lower thoracic spine, lumbar spine, and pelvis of the human body, it is suitable for lumbar scoliosis.

Basic Process of Design, Manufacturing, and Application of Customized Three-Dimensional-Printed Scoliosis Orthosis

The manufacturing process of a custom 3D-printed scoliosis orthosis is usually classified as: disease examination and diagnosis, prescribing custom orthosis, collection of patient imaging data, personalized design of orthotics, 3D printing processing, postprocessing, patient adaptation, effect monitoring, and feedback.

Disease examination and diagnosis

The doctor should conduct a professional examination of the patient's condition. According to the actual situation, the doctor should decide whether the patient needs X-ray, computed tomography (CT), or magnetic resonance imaging (MRI) examination to assist the diagnosis of the patient's condition. The doctor should make a detailed record of the patient's condition.

Prescribe three-dimensional-printed scoliosis orthosis

After comprehensive consideration, the doctor decides whether to prescribe a 3D-printed scoliosis orthosis for the patient. The prescription should be clear and reasonable, including key points such as location, purpose, and materials.

Collect patient imaging data

The design of the 3D-printed scoliosis orthosis should be based on the actual medical imaging data of the patient, collecting body surface data near the patient's spine. Moreover, according to the design needs, the patient should also provide X-rays, CT, or MRI images. The design of a 3D-printed scoliosis orthosis should be based on actual medical imaging data of the patient, with the relevant professionals using 3D scanning equipment to collect body surface data in the vicinity of the patient's spine. In addition, the patient should provide recent X-rays and, if necessary, collect CT or MRI images, depending on the design needs. Surface scanning and other methods can be used to collect data on the body surface.

Personalized design of orthosis

The orthodontist performs three-dimensional reconstruction of the obtained data through relevant professional software and then uses the corresponding software to design a 3D-printed scoliosis orthosis that is suitable for the patient and has a good orthopedic effect. When necessary, it simulates the mechanical properties of the orthosis. The design scheme should be feasible and effective, and the original design documents should be archived.

Three-dimensional printing processing

It converts the design files of the 3D-printed scoliosis orthosis into a file format that can be recognized by 3D printers such as STL through relevant professional software and determines the materials, types, and parameters of the 3D printing according to the orthopedic needs.

Postprocessing

After completing the production of the 3D-printed scoliosis orthosis, the orthosis needs to be appropriate postprocessed, mainly to remove supports, polish the surface, and add linings according to actual needs.

Patient adaptation

Under the guidance of professionals, put on the 3D-printed scoliosis orthosis for the patient. Before fitting the orthosis, the doctor or technician should inform the patient of the instructions for wearing the orthosis. It should be worn by a professional technician or under the guidance of a professional technician. Check whether the 3D-printed scoliosis orthosis meets the design and structural requirements, check whether the wearing position is correct, and inform the patient of the time and frequency of wearing.

Effect monitoring and feedback

Patients should be revisited regularly, and the results of follow-up consultations should be recorded and archived in detail. If the 3D-printed scoliosis orthosis cannot meet the patient's further orthopedic needs, it should be replaced in time.

Relevant Technical Specifications for the Quality Control of Three-Dimensional-Printed Scoliosis Orthosis

The relevant technical specifications should follow the principles of risk management and carry out relevant work in accordance with the requirements of the quality management system.

Scanning requirements

Pay attention to protect the privacy of the patient during the scan, and try to expose the scanned part as much as possible after obtaining the patient's consent.
During optical scanning, the patient Keep being in a standing position with shoulder abduction of 60°-80°.
The X-ray film patient maintains a standing position, and the doctor can perform CT or MRI examination according to the patient's condition to rule out other diseases.

Data requirements

The human body data model after the body surface scan contains the human body segment from the neck to 10 cm below the greater trochanter of the femur. The minimum requirements for the design and development of the orthosis should be met. There should be no holes, dislocations, superimposed models, etc., within the identifiable range. The accuracy of the scanning instrument used and the actual limb error should not exceed 1 mm to ensure the accuracy of the orthosis matching the patient.
Clinicians can collect the patient's clinical imaging data as needed, which should include full length anteroposterior and lateral X-ray of the spine in standing position or CT.
The authenticity, accuracy, and completeness of the data should be ensured. It also requires the security and integrity of data storage and privacy protection, as well as the exclusivity except for clinicians, designers and developers, production managers, patients, and regulators.

Orthotic design requirements

Orthotic design software should have functions such as patient information management, database management, insertion of patient pictures or medical image data, and guided design process.
The design should be carried out by or under the guidance of an orthopedist who trained by the design software. The design input is formed according to the orthosis prescription. After the purpose of the orthosis is clarified, the corresponding structural design can be carried out. The postdesign processing can be operated by the operator of the additive manufacturing equipment. Provide the correct orthodontic force to the deformed part, and the orthodontic force can be simulated by finite element modeling and simulation. Lightweight design should be adopted as much as possible, and hollow structures should be designed in nonload-bearing parts. The hollow structure is not <1 cm away from the edge of the orthosis, which is convenient for the adjustment and cutting of the orthosis. Must go through necessary design verification, and design verification can use multiple modes, such as physical testing, design evaluation, finite element analysis, and clinical comparison. When the patient's data belong to the design within the size boundary value of the original verification model, the risk can be evaluated by design evaluation, finite element analysis, etc. If the patient case data exceed the original verification range boundary, it should be re-evaluated and verified. Must go through the necessary design confirmation, and the designer should hand over the design plan documents to the clinician, sign and confirm, and archive. Any design change must be notified to and approved by the clinician, and sufficient reasons should be provided, and the medical–industrial interaction team should sign and confirm again. The main pressure surface cannot be hollowed out, and large holes can be opened in the release area to increase the permeability of the orthosis. A rib can be designed in the middle of the back spine to increase the overall strength of the orthosis.
The size should be 1:1 in proportion to the scanned data and design model, and the shape error should not exceed 1 mm. The thickness should be as thin as possible under the condition of meeting the strength.

Appearance requirements of orthotics

The surface should be smooth and flat, without sharp edges, burrs, and cracks. The customized additive manufacturing scoliosis orthosis printed by SLS should be sandblasted during postprocessing, and there should be no powder residue on the surface.

Material requirements

The materials used in customized 3D printing scoliosis orthosis should be comply with: can be used for SLS, FDM, and other printing; the material in direct contact with the skin should be nontoxic and nonirritating, the strength of the material should be moderate, and the mechanical properties of the material should be stable and should not fluctuate greatly with time or environment; if there is a risk of flammable or toxic gas, a description of warning information and preventive measures to reduce the risk should be provided at the time of product delivery.
After the compressive strength test, the compressive strength of the custom-made 3D-printed scoliosis orthosis should be ≥28 MPa; after the drop test, there should be no cracks, shedding, or fragmentation in any part.
The shore hardness of the customized 3D-printed scoliosis orthosis is not less than 58 D.

Biological evaluation

In vitro cytotoxicity: Cytotoxicity should not be >level 2.
Skin irritation: The primary irritation score should not exceed 1.
Delayed hypersensitivity: There should be no delayed hypersensitivity.

Adaptation requirements

Before the customized 3D-printed scoliosis orthosis is delivered to the patient, professionals check whether the orthosis meets the prescription design requirements and clinical treatment requirements.
Before adaptation, if necessary, patients should undergo flexible intervention training to meet the wearing requirements.
Under the guidance of clinicians and rehabilitation physicians, a rehabilitation therapist or orthotist should perform dressing and fitting, provide the patient with instructions for dressing, and inform the dressing instructions.
Clearly inform the start transition time, discontinuation indications, and re-examination time for wearing spinal orthosis.
After adaptation, the customized 3D-printed scoliosis orthosis does not affect the patient's activities of daily life.

Inspection Method

Design inspection

When necessary, finite element modeling software can be used for simulation mechanical analysis to ensure that the correction is effective and the hollow design does not affect the mechanical performance.

Commonly used finite element analysis software includes ANSYS, ABAQUS, ADINA, and MSC. Finite element simulation mainly considers the interaction between bones, torso surface, and orthosis. The bones include thoracic vertebrae, lumbar vertebrae, intervertebral discs, ribs, sternum, costal cartilage, and abdominal cavity. Simulation is carried out by dividing meshes, assigning material properties, defining contact characteristics, and confirming boundary conditions and loads. The geometric characteristics of the orthosis, such as alignment, opening area, pressure relief area, and strap position, were modified based on the calculated results of trunk deformation, lateral bending line, and stress and strain distribution. A good treatment effect needs to be modified repeatedly through numerical simulation.

Strength inspection

Drop test: After 24 h at −25°C, the height should not be <2 m, and the free fall drop test should be performed 5 times at this height.
Fatigue performance test: A mechanical testing machine is used to load a cyclic load on the customized 3D-printed scoliosis orthosis, and the cycle test is not <2500 times. The load should be determined according to the actual use.
Compressive strength test: Prepare samples for 3D-printed samples, the size and thickness of the samples shall meet the requirements of 4.0 ± 0.2 mm, and the test shall be carried out after 48 h at 23°C and 50% humidity.

Fit test

Under the guidance of clinicians and rehabilitation physicians, the orthosisist checks whether the suitability of the wear meets the design and fit requirements, and the wearer reports whether there is obvious discomfort.
Check the patient's intuitive perception of the back chest pressure pad and lumbar pressure pad; check that the position of the release force window should correspond to the pressure area, and the force should meet the release requirements; customized 3D-printed scoliosis orthosis on the back. The pressure on the edges and the cutting of the edges should not entrap the skin of the patient; the position of the subclavian pressure pad should not be too high or raised and should fit the patient's body; the height of the armpit should not cause pressure on the underarm nerve and blood circulatory system; abdominal pressure. The upper edge of the cushion shall not compress the ribs.
When the patient is in the sitting position after being worn, the distance between the lower edge of the customized 3D-printed scoliosis orthosis and the seat plane is at least 2 cm; the lower edge of the front abdomen of the customized 3D-printed scoliosis orthosis shall not compress the pubic symphysis or compress the rectus femoris and do not compress the iliac crest and the anterior superior iliac spine; after debugging, the orthopedist will mark the main pressure position with metal, take the full spine orthographic film in the standing position, and check the custom-made 3D-printed scoliosis orthosis. The effect is that it can generally be corrected 5° and above after being worn.

Full Process Supervision

The 3D-printed scoliosis orthosis is a second-class medical device. Considering that the 3D-printed scoliosis orthosis is an exclusive customized device, its entire process supervision needs to be different from the traditional medical device supervision. The market entry of 3D-printed scoliosis orthosis must strike a balance between encouraging innovation and protecting patients. It is necessary to use a combination of premarket testing and postmarket surveillance and prevention. Refer to the related procedures of traditional rehabilitation assistive devices/orthotics. Standards provide a basis for the whole-process supervision of 3D printing scoliosis.

The 3D-printed scoliosis orthosis supervision process is as follows: (1) a clinician or rehabilitation physician issues a 3D-printed scoliosis orthosis prescription and fills in complete technical documents; (2) a qualified orthopedist designs a personalized orthosis; (3) product quality inspection process, quality control personnel's signature, and registration number; (4) clinicians or rehabilitation physicians, signatures, prescriptions, data, and design plans are stored in the warehouse; (5) wearing and follow-up under the guidance of orthopedists; (6) adverse events of the product development after the market monitoring; (7) recall the defective products until they are delisted.

Conclusion

The prescription for 3D-printed scoliosis orthosis should be issued by a professional doctor in a regular hospital; the complete technical document should include the diagnosis result, the purpose of wearing the orthosis, the technical indicators (Cobb angle) measured by the professional and technical personnel, and the history of joint deformity and trauma. Qualification assessments should be set up for orthopedic design practitioners, and only those who pass the assessment can engage in orthopedic design-related work; because 3D-printed scoliosis orthosis is a personalized customized product, the design corresponds to the patient one-to-one, so the quality inspection is better than traditional. Orthotics should be more strict and standardized.

Financial support and sponsorship

This study was supported by grants from National Key R&D Program of China (2018YFC2002300/2018YFC2001300); Project of Shanghai Science and Technology Commission (18441903700/19XD1434200

/19441908700/19441917500); National Natural Science Foundation of China(81902195); Two-hundred Talent Support (20152224); Translational Medicine Innovation Project of Shanghai Jiao Tong University School of Medicine (TM201613/TM201915); Clinical Research Project of Multi-Disciplinary Team, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine (201914).

Conflicts of interest

Kerong Dai is a Honorary Editors-in-Chief of the journal. Jinwu Wang is an Associate Editor of the journal. Guoqi Niu is an Editorial Board Member of the journal. The article was subject to the journal's standard procedures, with peer review handled independently of this editor and his research groups.

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