For patients with fibrous dysplasia (FD) accompanied by severe "shepherd's crook" deformity, total hip arthroplasty (THA) faces significant challenges due to complex anatomy, pathological bone changes, and prosthesis instability. This study reports an integrated clinical pathway encompassing digital virtual planning, 3D printing customization, and biomechanical evaluation. Using Mimics software, patient CT data were reconstructed and 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 1800N 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 superior stability of the 3D-printed porous tantalum customized prosthesis system. Clinical follow-up of two patients demonstrated significantly improved Harris Hip Scores, with one case showing stable prosthesis position with no loosening or subsidence at 5 years postoperatively. This study demonstrates the value of precise, individualized 3D-printed customized prostheses in managing complex femoral anatomical deformities and pathological bone defects.