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RESEARCH ARTICLE

Development and Biomechanical Evaluation of an

Anatomical 3D Printing Modularized Proximal

Inter-Phalangeal Joint Implant Based on the Computed

Tomography Image Reconstructions

Yi-Chao Hunag , Chun-Ming Chang , Shao-Fu Huang , Chia-Heng Hong , Chun-Li Lin *
2
2,4
2,4
1,2
3
1 Department of Orthopedics and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan
2 Department of Biomedical Engineering, National Yang Ming Chiao Tung University, Taipei, Taiwan
3 Taiwan Instrument Research Institute, National Applied Research Laboratories, Hsinchu, Taiwan
4 Medical Device Innovation and Translation Center, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
Abstract: In this study, we developed a modularized proximal interphalangeal (PIP) joint implant that closely resembles the
anatomical bone articular surface and cavity contour based on computed tomography (CT) image reconstruction. Clouds of
points of 48 groups reconstructed phalanx articular surfaces of CT images, including the index, middle, ring, and little fingers,
were obtained and fitted to obtain the articular surface using iterative closest points algorithm. Elliptical-cone stems, including the
length, the major and minor axis at the stem metaphyseal/diaphyseal side for the proximal and middle phalanxes, were designed.
The resurfacing PIP joint implant components included the bi-condylar surface for the proximal phalanx with elliptical-cone
stem, ultra-high molecular weight polyethylene bi-concave articular surface for middle phalanx with hook mechanism, and the
middle phalanx with elliptical-cone stem. Nine sets of modularized designs were made to meet the needs of clinical requirements
and the weakness structure from the nine sets, that is, the worst structure case combination was defined and manufactured using
titanium alloy three-dimensional (3D) printing. Biomechanical tests including anti-loosening pull-out strength for the proximal
phalanx, elliptical-cone stem, and articular surface connection strength for the middle phalanx, and static/dynamic (25000 cycles)
dislocation tests under three daily activity loads for the PIP joint implant were performed to evaluate the stability and anti-dislocation
capability. Our experimental results showed that the pull-out force for the proximal phalanx implant was 727.8N. The connection
force for the hook mechanism to cone stem of the middle phalanx was 49.9N and the hook mechanism was broken instead of stem
pull out from the middle phalanx. The static dislocation forces/dynamic fatigue limits (pass 25000 cyclic load) of daily activities
for piano-playing, pen-writing, and can-opening were 525.3N/262.5N, 316.0N/158N, and 115.0N/92N, respectively, and were
higher than general corresponding acceptable forces of 19N, 17N, and 45N from the literatures. In conclusion, our developed
modularized PIP joint implant with anatomical articular surface and elliptical-cone stem manufactured by titanium alloy 3D
printing could provide enough joint stability and the ability to prevent dislocation.
Keywords: Proximal interphalangeal joint; Articular surface; Stem; 3D printing; Biomechanics

*Correspondence to: Chun-Li Lin, Department of Biomedical Engineering, Medical Device Innovation and Translation Center, National Yang
Ming Chiao Tung University, Taipei, Taiwan; cllin2@nycu.edu.tw
Received: March 23, 2022; Accepted: April 21, 2022; Published Online: June 10, 2022

Citation: Hunag YC, Chang CM, Huang SF, et al., 2022. Development and biomechanical evaluation of an anatomical 3D printing modularized
proximal inter-phalangeal joint implant based on the CT image reconstructions. Int J Bioprint, 8(3):579. http://doi.org/10.18063/ijb.v8i3.579

1. Introduction advanced arthritis, including osteoarthritis and
inflammatory arthritis, can cause painful disability, joint
The proximal interphalangeal (PIP) joint is the key destruction, and deformity. Conservative treatment,
actuator for finger motion and function. However, the frontline for symptomatic relief includes oral anti-

© 2022 Author(s). This is an Open-Access article distributed under the terms of the Creative Commons Attribution License, permitting distribution and
reproduction in any medium, provided the original work is properly cited.
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