Comparative Clinical and Biomechanical Assessment of Patient-Specific 3D-Printed Monoblock Versus Commercial Modular Acetabular Prostheses in Hip Arthroplasty for Reconstruction of Severe Acetabular Bone Defects

Abstract Background Commercial modular acetabular prostheses are widely used to reconstruct severe acetabular defects in hip arthroplasty. However, modular techniques may be limited by suboptimal defect matching and technical complexity. Patient-specific 3D-printed monoblock acetabular prostheses represent a novel reconstructive strategy that enables precise bone defect matching, customized fixation and facilitates restoration of the hip center of rotation. Nevertheless, clinical and biomechanical evidence regarding these prostheses remains limited. This study aimed to compare the clinical outcomes and biomechanical behavior of patient-specific 3D-printed monoblock prostheses with those of commercial modular prostheses. Methods Thirty-five patients with Paprosky type II–III acetabular defects were retrospectively divided into a 3D-printed group (n = 17) and a modular group (n = 18). Clinical outcomes and radiographic parameters were compared between groups. Biomechanical evaluations combining cadaveric testing and finite element analysis (FEA) were performed using cadaveric Paprosky type IIIA acetabular defect models. Results At a mean follow-up of approximately 32 months, the 3D-printed group had higher Harris hip scores (82.8 ± 6.1 vs. 76.6 ± 5.2, p = 0.003) and lower visual analogue scale pain scores (median 1 [interquartile range 0.5–1.5] vs. 2 [1–2], p = 0.003). The 3D-printed group also showed more accurate restoration of the vertical and horizontal positions of the hip center of rotation ( p = 0.016 and 0.045), less leg-length discrepancy (3.1 ± 1.8 vs. 6.2 ± 2.9 mm, p < 0.001), and a smaller femoral offset difference (3.3 ± 2.2 vs. 5.1 ± 1.2 mm, p = 0.006). At 800 cycles, permanent migration (86 [82–94] vs. 181 [178–186] µm, p < 0.001) and inducible micromotion (126 [119–128] vs. 289 [248–296] µm, p < 0.001) were markedly lower for the 3D-printed prostheses. The monoblock prostheses exhibited higher periacetabular bone strain and a more even prosthetic stress distribution than the modular prostheses, as demonstrated by cadaveric strain measurement and FEA, respectively. Conclusions Patient-specific 3D-printed monoblock acetabular prostheses were associated with better clinical outcomes and more accurate anatomical reconstruction than commercial modular acetabular prostheses. Independent biomechanical analyses suggested improved initial stability and more favorable periacetabular load transfer with monoblock prostheses.