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. 2015;2(1):4.
doi: 10.1186/s41205-016-0007-7. Epub 2016 Sep 22.

A rapid and intelligent designing technique for patient-specific and 3D-printed orthopedic cast

Hui Lin  1 , Lin Shi  2   3 , Defeng Wang  1   4
Affiliations

A rapid and intelligent designing technique for patient-specific and 3D-printed orthopedic cast

Hui Lin et al. 3D Print Med. 2015.

Abstract

Background: Two point four out of 100 people suffer from one or more fractures in the course of average lifetimes. Traditional casts are featured as cumbersome structures that result in high risk of cutaneous complications. Clinical demands for developing a hygienic cast have gotten more and more attention. 3D printing technique is rapidly growing in the fabrication of custom-made rehabilitation tools. The objective of this study is to develop a rapid and intelligent modeling technique for developing patient-specific and hygienic orthopedic casts produced by 3D printing technologies.

Results: A cast model is firstly created from a patient's image to develop patient-specific features. A unique technique to creating geometric reference has been developed to perform detail modeling cast. The cast is modeled as funnel-shaped geometry to create smooth edges to prevent bruises from mild movements of injured limbs. Surface pattern includes ventilation structure and opening gap for hygienic purpose and wearing comfort. The cast can be adjusted to accommodate swelling from injured limbs during treatment. Finite element analysis (FEA) is employed to validate the mechanical performance of the cast structure and identify potential risk of the structural collapse due to concentrated stresses. The cast is fabricated by 3D printing technology using approval material.

Conclusions: The 3D-printed prototype is featured as super lightweight with 1/10 of weight in compared with traditional alternatives. Medical technicians with few experiences can design cast within 20 min using the proposed technique. The image-based design minimizes the distortion during healing process because of the best fit geometry. The highly ventilated structure develops hygienic benefits on reducing the risk of cutaneous complications and potentially improve treatment efficacy and increase patients' satisfactions.

Keywords: 3D-printed; Hygienic; Intelligent; Orthopedic cast; Patient-specific; Rapid; Ventilated.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The scanned data of a limb and a raw cast surface cut from the data
Fig. 2
Fig. 2
Generation of flare opening. Extending coefficients are applied on the surface points near the opening end and funnel-shaped opening end are developed
Fig. 3
Fig. 3
a Centerline is sliced as segments with equal distance and generated as a number of polyline loops on the cross section of the cast surface. b User-specified point is selected by a technician for locating the opening gap. Alpha point is a reference point for further locating centers of holes. c A bundle of vector lines are created for locating the hole centers
Fig. 4
Fig. 4
a A micro sphere is created in each center for modeling a hole. b The ventilation holes distribute on the free cast surface
Fig. 5
Fig. 5
A control point set is created for generating the path of opening gap. A tube is modeled along the path and for further creating opening gap via Boolean operation
Fig. 6
Fig. 6
a Offset a surface vertex along a normal vector of a patch. b The modeling technique of the cast including centerline, ventilation hole, opening gap, and flare. Thickness of the cast is modelled in the last step
Fig. 7
Fig. 7
a The boundary condition of FEA analysis. A 3Mpa pressure is applied on the cast, and two opening edges are applied fixed support. b Results of finite element analysis. The maximal stress is around 10.18Mpa (left) and the maximal deformation is 0.15 mm (right). High stresses and deformities occur in the areas where mechanical loads are applied
Fig. 8
Fig. 8
A 3D-printed cast designed by the intelligent system using rapid modelling techniques
See this image and copyright information in PMC

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