Custom-Made 3D-Printed Implants for Paprosky Type 3A and 3B Acetabular Defects: Early Surgical and Functional Outcomes from a Multicentre Study.

Background and Objectives: Reconstruction of extensive acetabular bone defects in revision total hip arthroplasty (THA) remains technically demanding and is associated with a high risk of complications. Custom-made three-dimensional (3D)-printed implants have emerged as a patient-specific option for managing severe bone loss, particularly in Paprosky type 3A and 3B defects. The aim of this multicentre study was to evaluate the early clinical, radiographic, and surgical outcomes following single-stage reconstruction using custom-made 3D-printed acetabular implants. Materials and Methods: This retrospective multicentre study included 62 patients treated between 2021 and 2024 at four orthopaedic departments. All patients had Paprosky type 3A (n = 34) or 3B (n = 28) acetabular defects and underwent reconstruction with custom-made 3D-printed implants. A minimum clinical follow-up of 6 months was required for inclusion. Preoperative computed tomography was used for implant design and surgical planning. Clinical assessment included pain using the Visual Analogue Scale, functional evaluation using the Harris Hip Score and Karnofsky Performance Scale, mobility, range of motion, and use of orthopaedic aids. Radiographic evaluation included plain radiographs and computed tomography. Standardised functional and CT outcome assessments were performed during the first 6 months after surgery, whereas the mean overall follow-up represented subsequent clinical surveillance. Mean follow-up was 27 months. Results: All patients had undergone multiple previous surgical procedures before implantation of the custom-made prosthesis. The interval between primary arthroplasty and implantation of the custom-made implant ranged from 9 to 31 years. During follow-up, improvements in pain, mobility, and functional performance were observed across the entire cohort. The reported functional and CT outcomes refer to the standardised 6-month assessment period. Radiographic evaluation demonstrated satisfactory implant positioning and restoration of hip biomechanics. Progressive radiographic findings suggestive of implant integration were observed during follow-up. The most common complications were postoperative wound-healing disorders and prosthetic dislocation, particularly in patients with more extensive bone defects. Conclusions: Single-stage reconstruction using custom-made 3D-printed implants appears to be a feasible treatment option for patients with Paprosky type 3A and 3B defects, resulting in improvements in pain, mobility, and functional performance. Radiographic assessment suggested stable implant fixation and progressive implant integration during early follow-up. However, postoperative wound-healing disorders, infection, and prosthetic dislocation remain clinically relevant complications, particularly in patients with more extensive bone defects. Further studies with longer follow-up are required to determine long-term implant durability, implant survivorship, and functional outcomes.