Continuous Implant Load Monitoring to Assess Bone Healing Status—Evidence from Animal Testing

Windolf, Markus; Varjas, Viktor; Gehweiler, Dominic; Schwyn, Ronald; Arens, Daniel; Constant, Caroline; Zeiter, Stephan; Richards, R. Geoff; Ernst, Manuela

doi:10.3390/medicina58070858

Cited by 17 publications

(10 citation statements)

References 36 publications

(61 reference statements)

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“…The principle of continuous implant load monitoring has recently proven its potential as a relevant metric for assessing bone consolidation processes [ 20 ]. After having obtained encouraging results for long-bone healing, the question about transferability of the concept to spinal fusion is apparent.…”

Section: Discussionmentioning

confidence: 99%

“…The utilized metric to access fusion, relative implant load (RIL), was defined as the average of the highest 50 loading events over one day. This approach, taken from the trauma application [ 20 ], intends to maximize the observable difference between non-fused and fused states. While the vast majority of loading events occur in the low-amplitude range, the higher magnitude events were found to be most predictive for resolving bony consolidation and, thus, are collected in a peak event buffer.…”

Section: Discussionmentioning

confidence: 99%

“…A direct comparison between the studies is not feasible due to differences in the used model and our single-case data. It is worth noting that, in long-bone trauma applications, the implant load signal of the sensor appears particularly sensitive to early changes in fracture stiffness [ 20 ], while in this first spinal fusion case the signal response seems to be less pronounced early on. Over 16 weeks, RIL dropped to 30% for sensor L34 and only to 67% for sensor L23, indicating that in the least sensitive configuration the fusion process was resolved by ~30% of implant load drop.…”

Section: Discussionmentioning

confidence: 99%

“…An existing implantable sensor prototype, designed for plate load measurement in long bone fractures [ 20 ], was used in this study in a modified form. The sensor is actively powered by a battery, made for implant applications, to operate continuously and autonomously.…”

Section: Methodsmentioning

confidence: 99%

“…While Szivek et al [ 16 ] observed a decrease in bone strain during fusion in a single patient, Rohlmann et al [ 17 ] could not demonstrate a distinct response of fixator loading on the fusion process in ten patients with an instrumented screw-rod system. As opposed to these passively powered snapshot measurements, a novel approach involving the continuous measurement of implant loading has been recently developed by our group for trauma applications [ 9 , 18 , 19 , 20 ]. The system comprises an implantable datalogger which can be releasably attached to conventional bone plates.…”

Section: Introductionmentioning

confidence: 99%

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Continuous Rod Load Monitoring to Assess Spinal Fusion Status–Pilot In Vivo Data in Sheep

et al. 2022

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Background and Objectives: Spinal fusion is an effective and widely accepted intervention. However, complications such as non-unions and hardware failures are frequently observed. Radiologic imaging and physical examination are still the gold standards in the assessment of spinal fusion, despite multiple limitations including radiation exposure and subjective image interpretation. Furthermore, current diagnostic methods only allow fusion assessment at certain time points and require the patient’s presence at the hospital or medical practice. A recently introduced implantable sensor system for continuous and wireless implant load monitoring in trauma applications carries the potential to overcome these drawbacks, but transferability of the principle to the spine has not been demonstrated yet. Materials and Methods: The existing trauma sensor was modified for attachment to a standard pedicle-screw-rod system. Two lumbar segments (L2 to L4) of one Swiss white alpine sheep were asymmetrically instrumented. After facetectomy, three sensors were attached to the rods between each screw pair and activated for measurement. The sheep was euthanized 16 weeks postoperatively. After radiological assessment the spine was explanted and loaded in flexion-extension to determine the range of motion of the spinal segments. Sensor data were compared with mechanical test results and radiologic findings. Results: The sensors measured physiological rod loading autonomously over the observation period and delivered the data daily to bonded smartphones. At euthanasia the relative rod load dropped to 67% of the respective maximum value for the L23 segment and to 30% for the L34 segment. In agreement, the total range of motion of both operated segments was lower compared to an intact reference segment (L23: 0.57°; L34: 0.49°; intact L45: 4.17°). Radiologic assessment revealed fusion mass in the facet joint gaps and bilateral bridging bone around the joints at both operated segments. Conclusions: Observations of this single-case study confirm the basic ability of continuous rod load measurement to resolve the spinal fusion process as indicated by a declining rod load with progressing bone fusion. A strong clinical potential of such technology is eminent, but further data must be collected for final proof of principle.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Continuous Rod Load Monitoring to Assess Spinal Fusion Status–Pilot In Vivo Data in Sheep

et al. 2022

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Evolution of Musculoskeletal Electronics

Li,

Zhang,

Lyu

et al. 2024

Advanced Materials

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The musculoskeletal system, constituting the largest human physiological system, plays a critical role in providing structural support to the body, facilitating intricate movements, and safeguarding internal organs. By virtue of advancements in revolutionized materials and devices, particularly in the realms of motion capture, health monitoring, and postoperative rehabilitation, “musculoskeletal electronics” has actually emerged as an infancy area, but has not yet been explicitly proposed. In this review, we attempt to elucidate the concept of musculoskeletal electronics, and summarize the evolution history, representative progress and key strategies of the involved materials and state‐of‐the‐art devices. Therefore, we first introduce the fundamentals of musculoskeletal electronics and key functionality categories. Subsequently, we present recent advances in musculoskeletal electronics from the perspectives of “in‐vitro” to “in‐vivo” signal detection, interactive modulation, and therapeutic interventions for healing and recovery. Additionally, we propose nine strategies avenues for the development of advanced musculoskeletal electronic materials and devices. Finally, concise summaries and perspectives are proposed to highlight the directions that deserve focused attention in this booming field.This article is protected by copyright. All rights reserved

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Longitudinal CT‐based finite element analyses provide objective fracture healing measures in an ovine tibia model

Hetreau,

Mischler,

Schlatter

et al. 2024

Journal Orthopaedic Research

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Measuring the healing status of a bone fracture is important to determine the clinical care a patient receives. Implantable devices can directly and continuously assess the healing status of fracture fixation constructs, while subject‐specific virtual biomechanical tests can noninvasively determine callus structural integrity at single time points. Despite their potential for objectification, both methods are not yet integrated into clinical practice with further evidence of their benefits required. This study correlated continuous data from an implantable sensor assessing healing status through implant load monitoring with computer tomography (CT) based longitudinal finite element (FE) simulations in a large animal model. Eight sheep were part of a previous preclinical study utilizing a tibial osteotomy model and equipped with such a sensor. Sensor signal was collected over several months, and CT scans were acquired at six interim time points. For each scan, two FE analyses were performed: a virtual torsional rigidity test of the bone and a model of the bone‐implant construct with the sensor. The longitudinal simulation results were compared to the sensor data at corresponding time points and a cohort‐specific empirical healing rule was employed. Healing status predicted by both in silico simulations correlated significantly with the sensor data at corresponding time points and correctly identified a delayed and a nonunion in the cohort. The methodology is readily translatable with the potential to be applied to further preclinical or clinical cohorts to find generalizable healing criteria. Virtual mechanical tests can objectively measure fracture healing progressing using longitudinal CT scans.

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Continuous Implant Load Monitoring to Assess Bone Healing Status—Evidence from Animal Testing

Cited by 17 publications

References 36 publications

Continuous Rod Load Monitoring to Assess Spinal Fusion Status–Pilot In Vivo Data in Sheep

Continuous Rod Load Monitoring to Assess Spinal Fusion Status–Pilot In Vivo Data in Sheep

Evolution of Musculoskeletal Electronics

Longitudinal CT‐based finite element analyses provide objective fracture healing measures in an ovine tibia model

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