Novel Coronoid Reconstruction Using a Patient-Specific 3-Dimensional Metal-Printed Prosthesis and Guide for Comminuted Coronoid Process Fractures.

Background: The coronoid process is essential for elbow stability, and its severe comminuted fractures may require coronoid reconstruction. While coronoid reconstruction using autologous bone grafts has shown positive clinical outcomes, it has inherent limitations that create uncertainty in its outcomes. To our knowledge, while the potential for coronoid prostheses has emerged, there are currently no commercially available options, and clinical results remain insufficient. Thus, this study aimed to develop a new patient-specific coronoid prosthesis using 3-dimensional (3D) metal printing technology and to report clinical outcomes in patients with comminuted coronoid fractures where fixation was not feasible. Methods: We conducted a cadaveric validation to determine the optimal surgical approach and iteratively develop a patient-specific coronoid prosthesis and cutting guide. Bilateral 3D computed tomography was used to mirror and register the unaffected ulna to the injured side and define a cutting plane that removed only comminuted and nonviable bone while preserving key footprints such as the sublime tubercle. The patient-specific coronoid prosthesis was then applied in 2 patients with comminuted coronoid fractures not amenable to stable fixation. Evaluations comprised clinical and radiologic assessments. Clinical assessment included serial elbow range of motion (ROM), functional scoring, and documentation of the presence or absence of ulnar nerve symptoms. Radiologic assessment evaluated joint surface regularity, prosthesis-related complications, and evidence of bony integration at the titanium mesh interface. Results: We designed an integrated prosthesis and cutting guide that achieved favorable clinical outcomes with over 1 year of follow-up. Radiologic assessments of our patient-specific coronoid prosthesis demonstrated no irregularities on the joint surface, and no prosthesis-related complications were identified. Complete bony integration of the reconstructed area was confirmed approximately 6 months postoperatively, which can be attributed to the titanium mesh structure in the reconstruction area. Conclusions: Our patient-specific coronoid prosthesis, developed using 3D printing technology, achieved good clinical and radiologic outcomes with anatomical conformity. Our novel approach may improve recovery and function in patients with comminuted coronoid fractures for whom conventional fixation is difficult or unreliable, offering a promising alternative treatment option.