Microstructure and biomechanical characteristics of bone substitutes for trauma and orthopaedic surgery

Abstract. BACKGROUND: Many (artificial) bone substitute materials are currently available for use in orthopaedic trauma surgery. Objective data on their biological and biomechanical characteristics, which determine their clinical application, is mostly lacking. The aim of this study was to investigate structural and in vitro mechanical properties of nine bone substitute cements registered for use in orthopaedic trauma surgery in the Netherlands. METHODS: Seven calcium phosphate cements (BoneSource®, Calcibon®, ChronOS®, Eurobone®, HydroSet™, Norian SRS®, and Ostim®), one calcium sulphate cement (MIIG® X3), and one bioactive glass cement (Cortoss®) were tested. Structural characteristics were measured by micro-CT scanning. Compression strength and stiffness were determined following unconfined compression tests. RESULTS: Each bone substitute had unique characteristics. Mean total porosity ranged from 53% (Ostim®) to 0.5% (Norian SRS®). Mean pore size exceeded 100 μm only in Eurobone® and Cortoss® (162.2 ± 107.1 μm and 148.4 ± 70.6 μm, respectively). However, 230 μm pores were found in Calcibon®, Norian SRS®, HydroSet™, and MIIG® X3. Connectivity density ranged from 27/cm3 for HydroSet™ to 0.03/cm3 for Calcibon®. The ultimate compression strength was highest in Cortoss® (47.32 MPa) and lowest in Ostim® (0.24 MPa). Young's Modulus was highest in Calcibon® (790 MPa) and lowest in Ostim® (6 MPa). CONCLUSIONS: The bone substitutes tested display a wide range in structural properties and compression strength, indicating that they will be suitable for different clinical indications. The data outlined here will help surgeons to select the most suitable products currently available for specific clinical indications

Whole-scalp EEG mapping of somatosensory evoked potentials in macaque monkeys

High-density scalp EEG recordings are widely used to study whole-brain neuronal networks in humans non-invasively. Here, we validate EEG mapping of somatosensory evoked potentials (SSEPs) in macaque monkeys (Macaca fascicularis) for the long-term investigation of large-scale neuronal networks and their reorganisation after lesions requiring a craniotomy. SSEPs were acquired from 33 scalp electrodes in five adult anaesthetized animals after electrical median or tibial nerve stimulation. SSEP scalp potential maps were identified by cluster analysis and identified in individual recordings. A distributed, linear inverse solution was used to estimate the intracortical sources of the scalp potentials. SSEPs were characterised by a sequence of components with unique scalp topographies. Source analysis confirmed that median nerve SSEP component maps were in accordance with the somatotopic organisation of the sensorimotor cortex. Most importantly, SSEP recordings were stable both intra- and interindividually. We aim to apply this method to the study of recovery and reorganisation of large-scale neuronal networks following a focal cortical lesion requiring a craniotomy. As a prerequisite, the present study demonstrated that a 300-mm2 unilateral craniotomy over the sensorimotor cortex necessary to induce a cortical lesion, followed by bone flap repositioning, suture and gap plugging with calcium phosphate cement, did not induce major distortions of the SSEPs. In conclusion, SSEPs can be successfully and reproducibly recorded from high-density EEG caps in macaque monkeys before and after a craniotomy, opening new possibilities for the long-term follow-up of the cortical reorganisation of large-scale networks in macaque monkeys after a cortical lesion

Reconstitution bicorticale de grande taille de l’os calvarial par ciment ostéoconducteur Hydroset® associé à une grille en titane. Étude préliminaire

International audienceSummaryIntroductionBi-cortical calvarial bone loss is a very frequent issue for neurosurgery and craniofacial surgery. Several techniques can be used to reconstruct the skull, with variable difficulty and costs. The purpose of our study was to assess the use of Hydroset® osteoconductive cement for large size bicortical cranioplasties.Materials and methodsThree patients presented with extensive loss of calvarial bone bi-cortical substance (> 25 cm2), between 2010 and 2012. The 3 patients underwent cranioplasty with Hydroset® osteoconductive cement and titanium mesh.ResultsThe esthetic results were very satisfactory, especially for the skull dome, with a completely invisible and non-palpable cement/native skull junction. Scalp adherence to the cement was natural with maintenance of skin mobility.DiscussionBicortical calvarial bone reconstruction with Hydroset® cement is technically easy to perform, gives very good results, with an uneventful outcome, and induces lower costs.IntroductionLes pertes de substance bicorticales de l’os calvarial sont un problème fréquemment rencontré en neurochirurgie et en chirurgie craniofaciale. Plusieurs techniques existent afin de reconstruire le crâne, avec des difficultés de réalisation et des coûts variables. Le but de cette étude préliminaire est de voir si le ciment ostéoconducteur Hydroset® peut être utilisé pour des cranioplasties bicorticales de grandes tailles.Patients et méthodeEntre 2010 et 2012, trois patients ont présenté des pertes de substance bicorticales de grandes tailles (> 25 cm2) de l’os calvarial. Les 3 patients ont eu une cranioplastie par ciment ostéoconducteur Hydroset® associé à une grille en titane.RésultatsLes résultats esthétiques étaient très satisfaisants, en particulier sur le bombé du crâne et avec une jonction ciment/crâne natif parfaitement invisible et non palpable. L’adhérence du scalp à la cranioplastie en ciment était naturelle avec préservation d’un plan de glissement.DiscussionLa reconstruction bicorticale de l’os calvarial par ciment Hydroset® offre certains avantages sur le plan technique (facilité d’utilisation, très bons résultats, suites simples) et sur le plan économique