Design of a 3D Printed Patient Specific Cutting Guide for use in Anterior Closing Wedge High Tibial Osteotomy

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Date

2021-05

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The Ohio State University

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Abstract

Anterior closing wedge high tibial osteotomy (ACWHTO) is a type of orthopaedic surgery in which a wedge is cut and removed from the upper tibia to decrease the posterior tibial slope (PTS). Decreasing the PTS reduces the risk of anterior cruciate ligament (ACL) injuries. Current ACWHTO surgical procedures use a free-hand technique which results in poor intra-operative surgical accuracy. 3D printed patient specific cutting guides have improved intra-operative surgical accuracy in other types of surgical procedures; however, this technology does not currently exist for ACWHTO. The purpose of this research project is to design and test a 3D printed patient specific cutting guide for use in ACWHTO to provide an easier, more reproducible surgical technique and improve the intra-operative surgical accuracy. The cutting guide was designed with clinical guidance and modelled in CAD software. It consists of a base guide design with parameters that can be easily modified based on a patient's anatomy and operative plan. Two rounds of testing were completed for concept validation and to assess the guide's ability to improve surgical accuracy. The acceptance criteria used for testing was a 2° range of PTS correction and this value was based on previous studies examining outcomes of ACWHTO procedures. The first round of testing tested 2 prototype 3D printed cutting guides on 4 PVC pipe sections representing bones. This testing was a preliminary validation of the guide design and revealed improvements that needed to be made in the design like increasing the guide width and depth and decreasing the pin hole diameter. None of the 4 pipe sections had measured slope correction values within the acceptance range, and the range of percent differences between the intended slope correction and measured slope correction was 13%-29%. The second round of testing used a porcine tibia to test 1 3D printed cutting guide in a mock ACWHTO surgical procedure. The post-operative PTS measured did fall within the acceptance criteria range, and the percent difference between the intended slope correction and the measured slope correction was found to be 8.572%. Design improvements identified included reducing the amount of surface contact between the guide and the bone to reduce soft tissue interference and optimizing the use of materials in the guide. This research shows that the 3D printed patient specific cutting guide developed in this project has the potential to improve intra-operative surgical accuracy in ACWHTO procedures leading to better patient outcomes. It also provides an easier, more reproducible surgical technique making this procedure more accessible for surgeons who might not otherwise consider this technique for care of patients with elevated PTS.

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Keywords

3D printed surgical cutting guide design, Orthopaedic surgery, Surgical technology

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