Coronoid process replacement with individually designed 3D printed prosthesis

Background

Coronoid fractures account for 2 to 15% of the cases with elbow dislocations and usually occur as part of complex injuries. Comminuted fractures and non-unions necessitate coronoid fixation, reconstruction or replacement. 

Goal

To develop an individually designed 3D printed coronoid prosthesis with curved cemented intramedullary stem and compare its stability to both radial head grafted reconstruction and coronoid fixation with 2 screws.

Results

Based on CT scans of cadaveric forearms, 6 individualized coronoid prostheses with curved cemented intramedullary stems were designed and 3D printed from stainless steel. Eighteen human cadaveric proximal ulnas were osteotomized at 40% of the coronoid height and assigned to 3 groups treated with either (1) an individualized coronoid prosthesis with curved cemented intramedullary stem, (2) an ipsilateral radial head autograft fixed with two anteroposterior screws, or (3) two anteroposterior screws fixing the osteotomized coronoid. All specimens were biomechanically tested under ramped quasi-static axial loading to failure.

Prosthetic treatment resulted in significantly higher stiffness and failure load compared to both radial head autograft reconstruction and coronoid screw fixation, showing that in cases of coronoid deficiency, replacement of the coronoid process with an anatomically shaped individually designed 3D printed prosthesis with a curved cemented intramedullary stem seems to be an effective method restoring the buttress coronoid function under axial loading. In the clinical practice, implementation of this prosthesis type could allow for early patient mobilization with better short- and long-term treatment outcomes and may be beneficial for patients with irreparable comminuted coronoid fractures, severe arthritic changes or non-unions.