In Vivo Assessment of Bone Graft/Endplate Contact Pressure in a Caprine Interbody Pseudarthrosis Model: A Preliminary Biomechanical Characterization of the Fusion Process for the Development of a Microelectromechanical Systems (MEMS) Biosensor

Abstract

BackgroundIn this preliminary study we used a goat model to quantify pressure at an interbody bone graft interface. Although the study was designed to assess fusion status, the concept behind the technology could lead to early detection of implant failure and potential hazardous complications related to motion-preservation devices. The purpose of this study was to investigate the feasibility of in vivo pressure monitoring as a strategy to determine fusion status.MethodsTelemetric pressure transducers were implanted, and pressure at the bone graft interfaces of cervical interbody fusion autografts placed into living goats (Groups A and B) was evaluated. Group A constituted the 4-month survival group and Group B the 6-month survival group. One goat served as the study control (Group C) and was not implanted with a pressure transducer. An additional six cadaveric goat cervical spines (Group D) were obtained from a local slaughterhouse and implanted with bone grafts and ventral plates and used for in vitro biomechanical comparison to the specimens from Groups A and B.ResultsAll goats demonstrated an increase in interface pressure within the first 10 days postoperatively, with the largest relative change in pressure occurring between the sixth and ninth days. The goats from Groups A and B had a 200% to 400% increase in relative pressure.ConclusionsAlthough this was a pilot study to assess pressure as an indicator for a fusion or pseudarthrosis, the preliminary data suggest that early bone healing is detectable by an increase in pressure. Thus, pressure may serve as an indicator of fusion status by detecting altered biomechanical parameters.

Biomechanical Evaluation of Intervertebral Fusion Process After Anterior Cervical Discectomy and Fusion: A Finite Element Study

“…The novel method is based on the load transmission during bone healing. Ferrara et al (2007 ) and Ferrara et al (2008 ) investigated the feasibility of biomechanical characterization as a strategy to determine fusion status after ACDF with anterior plate and autografts. They found an increase in pressure at the graft–endplate interface and a decrease in load transmission along the ventral plate after bone fusion biomechanically simulated by polymethylmethacrylate (PMMA) insertion ( Ferrara et al, 2007 ).…”

“…They found an increase in pressure at the graft–endplate interface and a decrease in load transmission along the ventral plate after bone fusion biomechanically simulated by polymethylmethacrylate (PMMA) insertion ( Ferrara et al, 2007 ). Further in vivo assessment using telemetric pressure transducers demonstrated an increased pressure at the bone graft interfaces in living goats during the early stages after surgery, which may correlate with early graft subsidence ( Ferrara et al, 2008 ). Despite the absence of fusion in this preliminary study, their results emphasized the implications of pressure at bone graft interfaces and its relevance to the clinical setting.…”

“…Therefore, the mechanical loading on the instrumentation may be a promising indicator to evaluate the fusion status after ACDF, which has the potential to advance current diagnostic methods for interbody fusion. Several animal experiments suggested that the mechanical load on the spinal instrumentation may have the potential to reflect the fusion process and evaluated the stability of implant ( Takahata et al, 2005 ; Ferrara et al, 2007 ; Ferrara et al, 2008 ; Peterson et al, 2018 ). However, the inability to precisely measure the mechanical load of interbody implant in human body remains a significant barrier to determine the feasibility of reflecting the status of fusion through load changes on the instrumentation.…”