Design, mechanical validation, and clinical application of 3D-printed customized porous tantalum prostheses for total hip arthroplasty in fibrous dysplasia with shepherd's crook deformity

Abstract

For patients with fibrous dysplasia and severe “shepherd’s crook” deformity, total hip arthroplasty presents substantial challenges because of complex anatomy, pathological bone changes, and prosthesis instability. This study reports an integrated clinical pathway encompassing digital virtual planning, three-dimensional (3D) printing customization, and biomechanical evaluation. Using the Mimics software, patient computed tomography data were reconstructed, and a biplanar oblique osteotomy below the greater trochanter was simulated to correct the deformity. An individualized cementless long-stem prosthesis was designed based on the corrected medullary canal, followed by topology optimization and construction of a 70% porosity biomimetic porous structure to induce bone ingrowth. Finite element analysis under 1,800 N axial load and ±10 N•m torque showed peak stresses of 183.7 MPa in the femoral stem and 316.92 MPa in locking screws, both below material yield limits. Interface micromotion ranged from 0.21 mm to 0.48 mm, within the 0.5 mm threshold for promoting bone ingrowth, confirming the superior stability of the 3D-printed customized porous tantalum prosthesis system. Clinical follow-up of two patients demonstrated improved Harris Hip Scores, with one case showing a stable prosthesis position without loosening or subsidence at five years postoperatively. These findings support the potential value of precisely tailored 3D-printed prostheses in managing complex femoral deformities and pathological bone defects.

Keywords

Fibrous dysplasia / Shepherd's crook deformity / 3D printing / Total hip arthroplasty / Porous tantalum / Finite element analysis

Funding

This research was funded by the Dalian Dengfeng Plan Medical Key Specialty Construction Project (2021) (No. 243), the Dalian Science and Technology Innovation Fund (No. 2024ZDJH01PT140 and No. 2024RQ095), and the Liaoning Provincial Department of Education Basic Scientific Research Project Fund (No. LJ232511258004).

Conflict of Interest

The authors declare no conflicts of interest.

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