Early stage prediction of bone regeneration using FEA and cell differentiation algorithms with 3D-printed PLA and PCL scaffolds: modeling and application to dorsal double-plating in distal radius fractures

Abstract

This study introduces an advanced framework that integrates biphasic cell differentiation bone remodeling theory with finite element (FE) analysis and multi-remodeling simulation to evaluate the performance of 3D-printed biodegradable scaffolds for bone defect repair. The program incorporates a time-dependent cell differentiation stimulus (S), accounting for fluid-phase shear stress and solid-phase shear strain, to dynamically predict bone cell behavior. The study focuses on polylactic acid (PLA) and polycaprolactone (PCL) scaffolds with diamond (DU) and random (YM) lattice designs, applied to a dorsal double-plating (DDP) fixation model for distal radius fractures. Material testing reveals that PLA provides higher rigidity and strength, while PCL offers superior ductility. Mechanical strength tests confirm the superior performance of DU lattice structures under compression, shear, and torsion forces. The bone remodeling program, applied to 36 model combinations of fracture gaps, materials, and lattice designs, computes the total percentage of cell differentiation (TPCD), identifying scaffold material as the key factor, with PLA significantly enhancing TPCD values. Biomechanical analysis after 50 remodeling iterations in a 5.4 mm fracture gap shows that the PLA + DU scaffold reduces displacement by 35%/39%/75%, bone stress by 19%/16%/67%, and fixation plate stress by 77%/66%/93% under axial/bending/torsion loads, respectively, compared to the PCL + YM scaffold. This study highlights the critical role of dynamic remodeling programs in optimizing scaffold material properties and lattice architectures, establishing a robust platform for patient-specific bone repair solutions in regenerative medicine.

Keywords: 3D printing; Biomechanical; Bone remodeling; Lattice; PLA/PCL; Scaffold.

Fig. 1

(a) Dimension of the Type I specimen according to ASTM D638 standards; (b) schematic diagram of tensile testing for PLA, including longitudinal and transverse strain gages; (c) schematic diagram of tensile testing for PCL, including an extensometer and transverse strain gage; (d) testing stress-strain curves for PLA; (e) testing stress-strain curves for PCL

Fig. 2

(a) Dimensions of compression, shear and torsion testing specimens with DU and YM lattice designs, along with their corresponding unit size, pore size, porosity, and pillar diameter; (b) schematic diagram of PLA specimens before and after compression, shear and torsion testing (left: DU lattice; right: YM lattice); (c) schematic diagram of PCL specimens before and after compression, shear and torsion testing (left: DU lattice; right: YM lattice)

Fig. 3

The simulated distal radius fracture FE model, including three fracture gaps (2.7 mm, 5.4 mm and 8.1 mm) with DDP and corresponding loading and boundary conditions. The fracture gap was bridged by 3D-printed PLA/PCL scaffold and cell differentiation region

Fig. 4

Flowchart of the bone remodeling simulation iteration process

Fig. 5

The average failure strength of 3D-printed lattice specimens under compression, shear, and torsional forces. (a) for PLA specimens and (b) for PCL specimens

Fig. 6

(a) Results of the TPCD; (b) calculation results of the main effect, indicating that a steep slope had a greater impact on TPCD

Fig. 7

Illustration of the bone cell differentiation ratios, i.e. PCD value, in a distal radius fracture with a 5.4 mm gap using PLA + DU and PCL + YM scaffolds under compression, shear and torsion

Fig. 8

(a) The sum of S values for 50 iterations, showing less than 1% variation between iterations and reaching the convergence stage; (b) bone density distribution at the bone cell differentiation region for two bone remodeling models before and after 50 iterations

Fig. 9

Cross-sectional views of the bone cell differentiation region during bone remodeling process under compression, shear and torsion, where the top-right corner corresponded to the dorso-ulnar side, and the bottom-left corner corresponded to the dorso-radial side. (a) PLA + DU scaffold for 50 iterations; (b) PCL + YM scaffold for 50 iterations

Fig. 10

Results of biomechanical analysis from FE simulations before and after bone remodeling for PLA + DU and PCL + YM models under compression, shear and torsion. (a) total displacement; (b) maximum bone stress; (c) maximum plate stress

Fig. 11

Total displacement, bone plate stress distribution for PLA + DU model after 50 iteration bone remodeling. The maximum total displacement occurred at the distal end of the radius, the maximum bone stress was concentrated around the areas near the bone screws, and the maximum plate stress was located at the midsection of the bone plate regardless of the loading type