Biomechanical comparative finite element analysis between a conventional proximal interphalangeal joint flexible hinge implant and a novel implant design using a rolling contact joint mechanism

Abstract

Background The rolling contact joint (RCJ) mechanism is a system of constraint that allows two circular bodies connected with flexible straps to roll relative to one another without slipping. This study aims to compare the biomechanical characteristics between the conventional proximal interphalangeal joint (PIPJ) flexible hinge (FH) implant and the novel PIPJ implant adopting a RCJ mechanism during PIPJ range of motion using finite element (FE) analysis. Methods The three-dimensional (3D) surface shape of a conventional PIPJ FH implant was obtained using a 3D laser surface scanning system. The configuration and parameters of the novel PIPJ implant were adapted from a previous study. The two implants were assumed to have the same material characteristics and each implant was composed of a hyperelastic material, silicone elastomers. The configuration data for both implants were imported to a computer-aided design program to generate 3D geometrical surface and hyperelastic models of both implants. The hyperelastic models of both implants were imported into a structural engineering software to produce the FE mesh and to perform FE analysis. The FE analysis modeled the changes of mechanics during flexion–extension motion between 0° and 90° of two PIPJ implants. The mean and maximum values of von-Mises stress and strain as well as the total moment reaction based on the range of motion of the PIPJs were calculated. The mean values within the PIPJ’s functional range of motion of the mean and maxinum von-Mises stress and strain and the total moment reaction were also determined. Results The maximum values for the von-Mises stress, and strain, as well as the total moment reactions of the conventional PIPJ FH and novel PIPJ implants were all at 90° of PIPJ flexion. The maximum value of each biomechanical property for the novel PIPJ implant was considerably lower compared with that of the conventional PIPJ FH implant. The mean values within the PIPJ’s functional range of motion of the maximum von-Mises stress and strain for the novel PIPJ implant was approximately 6.43- and 6.46-fold lower compared with that of the conventional PIPJ FH implant, respectively. The mean value within a PIPJ’s functional range of motion of the total moment reaction of the novel PIPJ implant was approximately 49.6-fold lower compared with that of the conventional PIPJ FH implant. Conclusions The novel PIPJ implant with an RCJ mechanism may offer improved biomechanical performance compared with conventional PIPJ FH implant.

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“…The 3D laser surface scanning technique has been used in a broad range of industries: assessment of residual stresses in the laser powder bed fusion of metals [17], improvement of the rolling contact joint of biomechanical implants [18], or the creation of three-unit fixed partial dentures [19]. In this study, this technique was applied to evaluate the sphericity of the soy balls using a coordinate measuring machine, NIKON Altera 10.10.8 (LK Metrology Ltd., Derby, UK), equipped with a non-contact NIKON LC15Dx laser scanning probe (Left panel, Figure 1).…”