Robot-assisted implantation of additively manufactured patient-specific orthopaedic implants: evaluation in a sheep model

Abstract

Purpose Bone tumours must be surgically excised in one piece with a margin of healthy tissue. The unique nature of each bone tumour case is well suited to the use of patient-specific implants, with additive manufacturing allowing production of highly complex geometries. This work represents the first assessment of the combination of surgical robotics and patient-specific additively manufactured implants. Methods The development and evaluation of a robotic system for bone tumour excision, capable of milling complex osteotomy paths, is described. The developed system was evaluated as part of an animal trial on 24 adult male sheep, in which robotic bone excision of the distal femur was followed by placement of patient-specific implants with operative time evaluated. Assessment of implant placement accuracy was completed based on post-operative CT scans. Results A mean overall implant position error of 1.05 ± 0.53 mm was achieved, in combination with a mean orientation error of 2.38 ± 0.98°. A mean procedure time (from access to implantation, excluding opening and closing) of 89.3 ± 25.25 min was observed, with recorded surgical time between 58 and 133 min, with this approximately evenly divided between robotic (43.9 ± 15.32) and implant-based (45.4 ± 18.97) tasks. Conclusions This work demonstrates the ability for robotics to achieve repeatable and precise removal of complex bone volumes of the type that would allow en bloc removal of a bone tumour. These robotically created volumes can be precisely filled with additively manufactured patient-specific implants, with minimal gap between cut surface and implant interface.

Finite element analysis of patient-specific additive-manufactured implants

“…This research was conducted as a part of a larger animal study which was designed to investigate bone ingrowth and the biomechanical properties of sheep femora reconstructed with just-in-time patient-specific additive manufacturing (AM) implants ( Shidid et al, 2016 ), following robot-assisted partial resection of distal metaphysis ( Williamson et al, 2023 ). All animal procedures in this work were approved by the Animal Ethics Committee of the Faculty of Veterinary and Agricultural Sciences, the University of Melbourne (Infonetica # 10442) and were compliant with the Australian Code for the Care and Use of Animals for Scientific Purposes (2013).…”

“…All animal procedures in this work were approved by the Animal Ethics Committee of the Faculty of Veterinary and Agricultural Sciences, the University of Melbourne (Infonetica # 10442) and were compliant with the Australian Code for the Care and Use of Animals for Scientific Purposes (2013). Readers are referred to Williamson et al (2023) and Sanaei et al (2023) for further information on the design and outcome of this study.…”

“…What sets this study apart is its rigorous validation process, where the FE model’s predictions are compared against experimental data derived from an in vivo animal study. This animal study investigated the potential of enhancing tumor resection outcomes by incorporating patient-specific AM implants using surgical robotics ( Williamson et al, 2023 ). The aim of this work was to uncover the disparities between solid and lattice implants using an in vivo validated finite element (FE) model to analyze the influence of implant geometry and stiffness on the overall stiffness of implanted sheep femora.…”