Measuring compressive loads on a 'smart' lumbar interbody fusion cage: Proof of concept

Vivek A S Ramakrishna; Uphar Chamoli; Subhas C Mukhopadhyay; Ashish D Diwan; B Gangadhara Prusty

doi:10.1016/j.jbiomech.2023.111440

Measuring compressive loads on a 'smart' lumbar interbody fusion cage: Proof of concept

J Biomech. 2023 Jan:147:111440. doi: 10.1016/j.jbiomech.2023.111440. Epub 2023 Jan 9.

Authors

Vivek A S Ramakrishna¹, Uphar Chamoli², Subhas C Mukhopadhyay³, Ashish D Diwan⁴, B Gangadhara Prusty⁵

Affiliations

¹ School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, Kensington, New South Wales, Australia; Spine Labs, St. George & Sutherland Clinical School, University of New South Wales, Sydney, New South Wales, Australia; School of Engineering, Faculty of Science and Engineering, Macquarie University, Sydney, New South Wales, Australia. Electronic address: v.ramakrishna@student.unsw.edu.au.
² Spine Labs, St. George & Sutherland Clinical School, University of New South Wales, Sydney, New South Wales, Australia; School of Biomedical Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Ultimo, New South Wales, Australia.
³ School of Engineering, Faculty of Science and Engineering, Macquarie University, Sydney, New South Wales, Australia.
⁴ Spine Labs, St. George & Sutherland Clinical School, University of New South Wales, Sydney, New South Wales, Australia; Spine Service, Department of Orthopaedic Surgery St. George Hospital Campus, Kogarah, New South Wales, Australia.
⁵ School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, Kensington, New South Wales, Australia.

PMID: 36640615
DOI: 10.1016/j.jbiomech.2023.111440

Abstract

There are several complications associated with lumbar interbody fusion surgery however, pseudarthrosis (non-union) presents a multifaceted challenge in the postoperative management of the patient. Rates of pseudarthrosis range from 3 to 20 % in patients with healthy bone and 20 to 30 % in patients with osteoporosis. The current methods in post-operative follow-up - radiographs and CT, have high false positive rates and poor agreement between them. The aim of this study was to develop and test a proof-of-concept load-sensing interbody cage that may be used to monitor fusion progression. Piezoresistive pressure sensors were calibrated and embedded within a polyether ether ketone (PEEK) interbody cage. Silicone and poly (methyl methacrylate) (PMMA) were inserted in the graft regions to simulate early and solid fusion. The load-sensing cage was subjected to distributed and eccentric compressive loads up to 900 N between synthetic lumbar vertebral bodies. Under maximum load, the anterior sensors recorded a 56-58 % reduction in pressure in the full fusion state compared to early fusion. Lateral regions measured a 36-37 % stress reduction while the central location reduced by 45 %. The two graft states were distinguishable by sensor-recorded pressure at lower loads. The sensors more effectively detected left and right eccentric loads compared to anterior and posterior. Further, the load-sensing cage was able to detect changes in endplate stiffness. The proof-of-concept 'smart' cage could detect differences in fusion state, endplate stiffness, and loading conditions in this in vitro experimental setup.

Keywords: Instrumented implant; Interbody cage; Interbody fusion; Load sensing; Smart implant.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cadaver
Humans
Lumbar Vertebrae / surgery
Polyethylene Glycols
Pseudarthrosis*
Spinal Fusion*

Substances

Polyethylene Glycols