The influence of oral cavity physiological parameters: temperature, pH, and swelling on the performance of denture adhesives - in vitro study.

BACKGROUND: The various physical and chemical conditions within the oral cavity are hypothesized to have a significant influence on the behavior of denture adhesives and therefore the overall comfort of denture wearers. As such, this study aims to understand the influence of oral cavity physiological parameters such as temperature (17 to 52 °C), pH (2, 7, 10), and denture adhesive swelling due to saliva (20-120%) on the behavior of denture adhesives. This study further aims to emphasize the need for a collective approach to modelling the in-situ behavior of denture adhesives. METHODS: Rheological measurements were carried out using the Super Polygrip Ultra fresh brand denture adhesive cream to evaluate its storage modulus (G´) and loss modulus (G´´) values at a range of physiologically relevant temperatures, pH values, and degrees of swelling, to represent and characterize the wide variety of conditions that occur within the oral cavity. RESULTS: Rheological data was recorded with respect to variation of temperature, pH, and swelling. Overall, it can be seen that the physiological conditions of the oral cavity have an influence on the rheological properties of the denture adhesive cream. Specifically, our data indicates that the adhesive's mechanical properties are weakly influenced by pH, but do change with respect to the temperature in the oral cavity and the swelling rate of the adhesive. CONCLUSIONS: Our results suggest that the collective inter-play of the parameters pH, temperature and swelling ratio have an influence on the behavior of the denture adhesive. The results clearly highlight the need for developing a multi-parameter viscoelastic material model to understand the collective influence of physiological parameters on the performance of denture adhesives. Multi-parameter models can also potentially be utilized in numerically simulating denture adhesives using finite element simulations.

Mapping the role of oral cavity physiological factors into the viscoelastic model of denture adhesives for numerical implementation.

Physiological parameters of the oral cavity have a profound impact on any restorative solutions designed for edentulous patients including denture adhesives. This study aims to mathematically quantify the influence of three such variables, namely: the temperature, pH, and the swelling of such adhesives under the influence of saliva on its mechanical behavior. The mathematical quantification is further aimed to implement a material model for such adhesives which considers the impact of such physiological factors. The denture adhesive is experimentally investigated by means of rheological steady state frequency sweep tests to obtain the relaxation spectrum of the material. The relaxation behavior is measured for a wide range of oral cavity temperatures and pH. Also, the adhesive is hydrated and upon swelling to different levels again tested to understand the impact of swelling on the mechanical behavior. The experimentally measured continuous relaxation spectrum is modeled as a viscoelastic material using a discrete set of points based on the Prony series discretization technique. The relaxation spectrums for various temperatures are compared and the possibility of a time-temperature superposition is explored for the model. Similarly, the measured values of Storage and loss modulus are investigated to understand the role of pH and swelling. The results in this study clearly indicated a horizontal shift in the relaxation behavior with increase in temperature. And hence, the time-temperature shift factor was calculated for the adhesive. The relaxation spectrum also showed a strong correlation with swelling of the adhesive and the pH. The influence of these two parameters were captured into the model based on the relaxation time parameter in the Prony series approach. Based on this study the impact of these parameters could be appreciated on the performance and mechanical behavior of denture adhesives and implemented into a Prony series based viscoelastic material model which can be used with numerical simulations.

Perioperative outcome of minimally invasive stabilisation of bilateral fragility fractures of the sacrum: a comparative study of bisegmental transsacral stabilisation versus spinopelvic fixation.

PURPOSE: Pelvic fragility fractures have steadily risen over the past decades. The primary treatment goal is the fastest possible mobilisation. If conservative therapy fails, surgical fixation is a promising approach. This study compares the outcome of bisegmental transsacral stabilisation (BTS) and spinopelvic fixation (SP) as minimally invasive techniques for bilateral fragility fractures of the sacrum (BFFS). METHODS: We performed a prospective, non-randomised, case-controlled study. Patients were included if they remained bedridden due to pain despite conservative treatment. Group assignment depended on sacral anatomy and fracture type. The outcome was estimated by blood loss calculation, cut-seam time, fluoroscopy time, complications, duration of stay at the intensive/intermediate care unit (ICU/IMC), and total inpatient stay. The mobility level at discharge was recorded. RESULTS: Seventy-three patients were included (SP: 49, BTS: 24). There was no difference in blood loss (BTS: 461 ± 628 mL, SP: 509 ± 354 mL). BTS showed a significantly lower cut-seam time (72 ± 23 min) than SP (94 ± 27 min). Fluoroscopy time did not differ (BTS: 111 ± 61 s vs. 103 ± 45 s). Thirteen percent of BTS and 16% of SP patients required ICU/IMC stay (BTS: 0.6 ± 1.8 days, SP: 0.5 ± 1.5 days) during inpatient stay (BTS: 9 ± 4 days, SP: 8 ± 3 days). Fourteen patients suffered from urinary tract infections (BTS: 8%; SP: 25%). In-patient mortality was low (BTS: 4.2%, SP: 4.1%). At discharge, the BTS group was almost back to the initial mobility level. In SP patients, mobility was significantly lower than before complaints (p = 0.004). CONCLUSION: Both methods allow early mobilization of BFFS patients. Blood loss can be kept low. Hence, transfusion requirement is correspondingly low. The IMC/ICU and the total inpatient stay are lower than reported in the literature. Both BTS and SP can be recommended as safe and low-complication methods for use in BFFS patients. BTS is superior to SP with respect to surgery duration and level of mobility at discharge.

A software-based approach for calculating spatially resolved radiation exposure for structural radiation protection in nuclear medical imaging.

The objective of the work described is the development of a software tool to provide the calculation routines for structural radiation protection from positron and gamma emitters, for example,18F. The calculation of the generated local annual dose in the vicinity of these radioactive sources supports the engineering of structural measures necessary to meet regulatory guidelines. In addition to accuracy and precision, a visual and intuitive presentation of the calculation results enables fast evaluation. Finally, the calculated results are presented in a contour plot for design, evaluation, and documentation purposes. A python program was used to provide the calculation routines for structural radiation protection. For simplicity, the radiating sources can be considered as point sources. The attenuation of structural elements can be specified or, in the case of lead, calculated by virtue of its thickness. The calculated attenuation for the lead shielding is always slightly underestimated, which leads to a marginally higher calculated local dose rate than would be physically present. With the conservatively determined value, the structural radiation protection can be optimised in accordance with the general rule of as low as reasonably achievable. The pointwise comparison between the software results and the standard procedure for calculating the dose of points in space leads to similar values. In comparison with the general approach of calculating single representative points in the radiation protection area, the visual and intuitive presentation of the results supports the design and documentation of the measures required for structural radiation protection. In the present version of the software, the local dose rate and local annual dose are overestimated by a maximum of 4.5% in the case of lead shields. The proposed software, termed RadSoft, was successfully used to develop the structural radiation protection of a controlled area for hybrid magnetic resonance - positron emission tomography imaging, with the focus herein being on the requirements for PET.

Numerical study of the stress state on the oral mucosa and abutment tooth upon insertion of partial dentures in the mandible.

The introduction of a removable partial denture onto the dental arch significantly influences the mechanical stress characteristics of both the jawbone and oral mucosa. The aim of this study was to analyze the stress state caused by biting forces upon insertion of partial dentures into the assembly, and to understand the influence of the resulting contact pressure on its retention behavior. For this purpose, a numerical model of a removable partial denture is proposed based on 3D models developed using computer tomography data of the jawbone and the removable partial denture. The denture system rests on the oral mucosa surface and three abutment teeth. The application of bite forces on the denture generated a stick condition on the loaded regions of the denture-oral mucosa interface, which indicates positive retention of the denture onto the oral mucosa surface. Slip and negative retention were observed in the regions of the contact space that were not directly loaded. The contact pressures observed in the regions of the oral mucosa in contact with the denture were below the clinical pressure pain threshold value for soft tissue, which potentially lowers the risk of pain being experienced by denture users. Further, the variation of the retention behavior and contact pressures across different regions of the denture assembly was observed. Thus, there is a need for adhesives or restraining mechanisms for the denture system in order to avoid bending and deformation of sections of the denture as a consequence of the applied bite force.

Finite Element Evaluation of the Effect of Adhesive Creams on the Stress State of Dentures and Oral Mucosa.

The base fit between a removable partial denture (RPD) and the underlying soft tissue plays a significant role in its performance. The application of a denture adhesive is hypothesized to result in better retention of RPDs and, as a result, contribute to lower stress on the oral mucosa. The objectives of this study were to observe and compare the distribution of simulated bite forces applied to the RPD through the abutments and soft tissue for models with and without the use of a denture adhesive. Furthermore, we evaluated the possible benefit of using a denture adhesive in lowering stresses on the oral mucosa. The RPD, mandible, oral mucosa, abutment teeth supporting the RPD, and the corresponding abutment periodontal ligaments (PDLs) were modelled as 3D volumes based on computer tomography (CT) datasets. A viscoelastic adhesive layer between the RPD and oral mucosa was incorporated into this base model using Prony series approximation. The layer was developed as a volume extract using the denture surface. Finite element (FE) simulations were performed for the bite force on one of the RPD segments, with the resulting force and moments experienced by the dental structures and oral mucosa compared between the model with the adhesive layer and the base model without. As a result, the contact pressure on the oral mucosa for the model with the denture adhesive decreased to 0.15 MPa as compared to 0.25 MPa for the model without the adhesive. The potential role of denture adhesives in leading to a better fit between the RPD and oral mucosa as well as lowering contact pressures could be used to improve comfort in patients wearing RPDs.

Long-term pre-clinical evaluation of an injectable chitosan nanocellulose hydrogel with encapsulated adipose-derived stem cells in an ovine model for IVD regeneration.

The potential therapeutic benefit of adipose-derived stem cells (ASCs) encapsulated in an injectable hydrogel for stimulating intervertebral disc (IVD) regeneration has been assessed by a number of translational and preclinical studies. However, previous work has been primarily limited to small animal models and short-term outcomes of only a few weeks. Long-term studies in representative large animal models are crucial for translation into clinical success, especially for permanent stabilization of major defects such as disc herniation. An injectable chitosan carboxymethyl cellulose hydrogel scaffold loaded with ASCs was evaluated regarding its intraoperative handling, crosslinking kinetics, cell viability, fully-crosslinked viscoelasticity, and long-term therapeutic effects in an ovine model. Three IVDs per animal were damaged in 10 sheep. Subcutaneous adipose tissue was the source for autologous ASCs. Six weeks after IVD damage, two of the damaged IVDs were treated via ASC-loaded hydrogel injection. After 12 months following the implantation, IVD disc height and histological and cellular changes were assessed. This system was reliable and easy to handle intraoperatively. Over 12 months, IVD height was stabilized and degeneration progression significantly mitigated compared to untreated, damaged IVDs. Here we show for the first time in a large animal model that an injectable chitosan carboxymethyl cellulose hydrogel system with encapsulated ASCs is able to affect long-term stabilization of an injured IVD and significantly decrease degeneration processes as compared to controls.

Bone Micromorphology and Material Attrition After Sonic, Ultrasonic and Conventional Osteotomies.

BACKGROUND/AIM: Osteotomy as the first step in surgery, provides access to the field and its application could influence the outcome. Nowadays, the conventional burr reduction is being challenged by newer sonic and ultrasonic methods. We investigated the bone structural integrity and metal attrition residues both in bone and the irrigation fluid. MATERIALS AND METHODS: Bovine ribs were cut using three methods. Bone cuts were studied using Environmental Scanning Electron Microscopy (ESEM) for tissue discrepancies and Scanning Electron Microscopy/Energy Dispersion X-Ray Microanalysis (SEM/EDX) for organic and inorganic debris. RESULTS: Better preservation of bone architecture was seen in piezo and sono surgery while metal attrition was not conclusive (p>0.05). Unlike in bone analyses, both bur and ultrasonic osteotomies showed statistically significant higher median inorganic detection per analysis (p=0.021 and p=0.037, respectively). CONCLUSION: Sono and piezo surgery proved to be less invasive while attrition properties were the same.

Intervertebral Disc Regeneration Injection of a Cell-Loaded Collagen Hydrogel in a Sheep Model.

Degenerated intervertebral discs (IVDs) were treated with autologous adipose-derived stem cells (ASC) loaded into an injectable collagen scaffold in a sheep model to investigate the implant's therapeutic potential regarding the progression of degeneration of previously damaged discs. In this study, 18 merino sheep were subjected to a 3-step minimally invasive injury and treatment model, which consisted of surgically induced disc degeneration, treatment of IVDs with an ASC-loaded collagen hydrogel 6 weeks post-operatively, and assessment of the implant's influence on degenerative tissue changes after 6 and 12 months of grazing. Autologous ASCs were extracted from subcutaneous adipose tissue and cultivated in vitro. At the end of the experiment, disc heights were determined by µ-CT measurements and morphological tissue changes were histologically examined.Histological investigations show that, after treatment with the ASC-loaded collagen hydrogel implant, degeneration-specific features were observed less frequently. Quantitative studies of the degree of degeneration did not demonstrate a significant influence on potential tissue regeneration with treatment. Regarding disc height analysis, at both 6 and 12 months after treatment with the ASC-loaded collagen hydrogel implant a stabilization of the disc height can be seen. A complete restoration of the intervertebral disc heights however could not be achieved.The reported injection procedure describes in a preclinical model a translational therapeutic approach for degenerative disc diseases based on adipose-derived stem cells in a collagen hydrogel scaffold. Further investigations are planned with the use of a different injectable scaffold material using the same test model.

Mid-term outcome of bilateral fragility fractures of the sacrum after bisegmental transsacral stabilization versus spinopelvic fixation.

AIMS: Minimally invasive fixation of pelvic fragility fractures is recommended to reduce pain and allow early mobilization. The purpose of this study was to evaluate the outcome of two different stabilization techniques in bilateral fragility fractures of the sacrum (BFFS). METHODS: A non-randomized, prospective study was carried out in a level 1 trauma centre. BFFS in 61 patients (mean age 80 years (SD 10); four male, 57 female) were treated surgically with bisegmental transsacral stablization (BTS; n = 41) versus spinopelvic fixation (SP; n = 20). Postoperative full weightbearing was allowed. The outcome was evaluated at two timepoints: discharge from inpatient treatment (TP1; Fitbit tracking, Zebris stance analysis), and ≥ six months (TP2; Fitbit tracking, Zebris analysis, based on modified Oswestry Disability Index (ODI), Majeed Score (MS), and the 12-Item Short Form Survey 12 (SF-12). Fracture healing was assessed by CT. The primary outcome parameter of functional recovery was the per-day step count; the secondary parameter was the subjective outcome assessed by questionnaires. RESULTS: Overall, no baseline differences were observed between the BTS and SP cohorts. In total, 58 (BTS = 19; SP = 39) and 37 patients (BTS = 14; SP = 23) could be recruited at TP1 and TP2, respectively. Mean steps per day at TP1 were median 308 (248 to 434) in the BTS group and 254 (196 to 446) in the SP group. At TP2, median steps per day were 3,759 (2,551 to 3,926) in the BTS group and 3,191 (2,872 to 3,679) in the SP group, each with no significant difference. A significant improvement was observed in each group (p < 0.001) between timepoints. BTS patients obtained better results than SP patients in ODI (p < 0.030), MS (p = 0.007), and SF-12 physical status (p = 0.006). In all cases, CT showed sufficient fracture healing of the posterior ring. CONCLUSION: Both groups showed significant outcome improvement and sufficient fracture healing. Both techniques can be recommended for BFFS, although BTS was superior with respect to subjective outcome. Step-count tracking represents a reliable method to evaluate the mobility level. Cite this article: Bone Joint J 2021;103-B(3):462-468.

Progressive instability of bilateral sacral fragility fractures in osteoporotic bone: a retrospective analysis of X-ray, CT, and MRI datasets from 78 cases.

PURPOSE: The pathogenetic mechanism, progression, and instability in geriatric bilateral fragility fractures of the sacrum (BFFSs) remain poorly understood. This study investigated the hypothesis of sequential BFFS progression by analysing X-ray, computed tomography (CT), and magnetic resonance imaging (MRI) datasets. METHODS: Imaging data from 78 cases were retrospectively analysed. Fractures were categorized using the CT-based Fragility Fractures of the Pelvis classification. MRI datasets were analysed to detect relevant fracture location information. The longitudinal sacral fracture was graded as stage 1 (bone oedema) on MRI, stage 2 (recent fracture), stage 3 (healing fracture), or stage 4 (non-union) on CT. Ligamentous avulsions at the L5 transverse process and iliac crest were also captured. RESULTS: Contralateral sacral lesions were only recognized by initial bone oedema on MRI in 17/78 (22%) cases. There were 22 cases without and 56 cases with an interconnecting transverse fracture component (TFC) [between S1/S2 (n = 39) or between S2/S3 (n = 17)]. With 30/78 patients showing bilateral fracture lines at different stages (1/2: n = 13, 2/3: n = 13, 1/3: n = 4) and 38 at similar stages, Wilcoxon tests showed a significant stage difference (p < 0.001). Forty cases had a coexistent L5 transverse process avulsion, consistent with a failing iliolumbar ligament. Analysis of variance revealed significant increases in ligamentous avulsions with higher fracture stages (p < 0.001). CONCLUSION: Our results support the hypothesis of stagewise BFFS progression starting with unilateral sacral disruption followed by a contralateral lesion. Loss of sacral alar support leads to a TFC. Subsequent bone disruption causes iliolumbar ligament avulsion. MRI is recommended to detect bone oedema.

Calvarial Reconstruction Following Massive Tissue Loss: A Feasible Treatment Strategy and Surgical Technique.

BACKGROUND: Severe cranial injuries require reconstructive surgeries to protect the underlying brain and to restore cranial contour and scalp integrity, as well as avoid complications such as neurocognitive decline. In cases of full-thickness cranial tissue damage, adept surgical skill in both bone and soft tissue reconstruction is critical for a minimally invasive surgery and successful bone integration without endangering previous soft tissue efforts. Different surgical techniques and materials are beset with various problems. OBJECTIVE: To present a surgical procedure intended for the reconstruction of complex calvarial and associated tissue defects with reduced invasiveness and improved soft tissue healing compared to the existing gold standard. Both soft tissue and bone reconstruction techniques are described in detail due to their intertwined importance for successful full thickness skull and scalp reconstruction. METHODS: During initial medical care, aseptic wound treatment and temporary wound closure are performed. Two weeks postinjury, extensive necrotic tissue debridement and soft tissue reconstruction lay the foundation for well-vascularized tissue regeneration. Soft tissue healing is followed by minimally invasive cranioplasty using autologous split-rib transplants after approximately 6 mo. RESULTS: With consideration of the established gold standards for treatment, soft tissue regenerated without complications. The minimally invasive insertion of autologous rib grafts underneath the healed soft tissue allowed for quick recovery without requiring further follow-up treatments. CONCLUSION: We optimized initial scalp wound healing and bone regeneration by making use of minimally invasive procedures and autologous materials, offering a viable treatment alternative to existing methods for treating large cranial bone injuries.

Ergonomics of surgical microscopes for the sitting position as determined by ocular-corpus length.

BACKGROUND: The sitting position is favorable for microsurgical procedures applied to posterior midline pathologies in both the supra- and infratentorial regions. The dimensions of the microscope corpus affect the device's comfort and handling in the hands of the microneurosurgeon for such procedures. A shorter microscope corpus provides more favorable intraoperative ergonomics for surgical practice. METHODS: Evaluation of the most comfortable microscope for its application in microsurgical procedures in the sitting position as determined by ocular-corpus length. RESULTS: Six modern surgical microscopes were tested and evaluated regarding their ocular-corpus lengths and working distances: the Mitaka MM90, Zeiss Kinevo 900, Zeiss Pentero 900, Leica M530, Zeiss Neuro NC4, and Möller-Wedel Hi-R 1000. The ocular-corpus lengths vary between 270 and 380 mm. The Mitaka MM90 microscope has the shortest ocular-corpus length at 270 mm. CONCLUSION: The ocular-corpus length determines the predominant part of the lever arm, which affects the fatigue of the surgeon. By virtue of its short ocular-corpus length, the Mitaka MM90 is currently the most favorable microscope for microsurgical procedures using a sitting position.

Arthrodesis of the equine proximal interphalangeal joint: a biomechanical comparison of 2 different LCP systems.

OBJECTIVE: This study compares the mechanical stability and surgical usability of 2 locking plate systems (Kyon ALPS-20 and Synthes PIP-LCP system) for arthrodesis of the equine proximal interphalangeal joint (PIJ). MATERIAL AND METHODS: The experimental ex vivo study included 6 pairs of cadaver distal limbs (n = 12). All specimens were derived from Warmblood horses of various ages that were euthanized for non-orthopedic reasons. Of the 12 limbs collected, 3 left and 3 right distal limb specimens were randomly assigned to each system for implantation. Two abaxial 4.5-mm cortical screws were inserted transarticularly in all cases. Both systems were implanted according to the manufacturer's instructions with the plates placed centrally between the 2 transarticular screws. The ALPS-20 systems were implanted using Kyon B-6.4-mm monocortical locking screws in all positions. The LCP systems were implanted axially using 2 Synthes 5-mm locking screws in the proximal and distal positions, with a standard 4.5-mm cortical screw inserted in the middle position. All constructs underwent CT-scans after implantation and biomechanical testing to detect implant deformation. Uniaxial mechanical loading was applied via a servo-hydraulic test system at a test speed of 50 mm/s, up to a maximum displacement of 80 mm. The resulting load-displacement curves were used to calculate yield point, stiffness, and maximum force for each construct. The measured values were evaluated for statistical significance (p < 0.05) between the 2 plate systems via one-factor ANOVA (Tukey test). The statistical power was verified for yield force, stiffness, and maximum load. RESULTS: No statistically significant differences between the 2 preparation groups were calculated across all of the measured parameters (p > 0.05). The ALPS system implants showed no signs of deformation, either in the plates or the screws. In contrast, the LCP demonstrated visible deformation, which had already occurred at the time of implantation from the tightening of the middle screw, as well as during the subsequent testing of the implants. After biomechanical testing, deformations ranging between 3.1° and 7.0° were measured in 4 LCPs. A total implant failure was observed for 2 LCPs. CONCLUSION AND CLINICAL RELEVANCE: Both systems demonstrated comparable mechanical properties in the present study's ex vivo test model for equine PIJ arthrodesis. As such, the Kyon ALPS-20 may be a good alternative to the Synthes LCP for equine PIJ arthrodesis.

Patient-Specific Bone Multiscale Modelling, Fracture Simulation and Risk Analysis-A Survey.

This paper provides a starting point for researchers and practitioners from biology, medicine, physics and engineering who can benefit from an up-to-date literature survey on patient-specific bone fracture modelling, simulation and risk analysis. This survey hints at a framework for devising realistic patient-specific bone fracture simulations. This paper has 18 sections: Section 1 presents the main interested parties; Section 2 explains the organzation of the text; Section 3 motivates further work on patient-specific bone fracture simulation; Section 4 motivates this survey; Section 5 concerns the collection of bibliographical references; Section 6 motivates the physico-mathematical approach to bone fracture; Section 7 presents the modelling of bone as a continuum; Section 8 categorizes the surveyed literature into a continuum mechanics framework; Section 9 concerns the computational modelling of bone geometry; Section 10 concerns the estimation of bone mechanical properties; Section 11 concerns the selection of boundary conditions representative of bone trauma; Section 12 concerns bone fracture simulation; Section 13 presents the multiscale structure of bone; Section 14 concerns the multiscale mathematical modelling of bone; Section 15 concerns the experimental validation of bone fracture simulations; Section 16 concerns bone fracture risk assessment. Lastly, glossaries for symbols, acronyms, and physico-mathematical terms are provided.

Long-Term Pathology of Ovine Lumbar Spine Degeneration Following Injury Via Percutaneous Minimally Invasive Partial Nucleotomy.

The focus of this work is to assess the long-term progression of degeneration in the ovine lumbar spine following a minimally invasive model injury comparable to the damage of an intervertebral disc (IVD) herniation. A partial nucleotomy was performed on 18 sheep via the percutaneous dorsolateral approach. The animals were culled at 6 and 12 months to evaluate the damaged and neighboring functional spine units (FSUs) for degenerative characteristics via µ-CT and histology. Both quantitative µ-CT and histology investigations demonstrated statistically significant differences between the native and damaged FSUs investigated. Qualitative analysis of µ-CT revealed numerous pathological markers consistent with intervertebral disc degeneration (IDD), with differences in frequency and severity between the native and damaged FSUs. The annulus fibrosus reforms a pressure seal within 6 weeks, but the extent of the trauma is significant enough to initiate IVD degeneration, which is already clearly visible at 6 months and especially so 12 months post-op. IDD pathology consistent with signs of a herniation was seen in both the 6- and 12-month groups. This technique provides a useful model injury for the preclinical evaluation of IDD in large animal models, especially in regards to simulating disc herniation as well as for testing the efficacy of associated therapies in the future. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2376-2388, 2019.

TachoSil Dural Reconstruction in Extracranial-Intracranial Bypass Surgeries.

BACKGROUND: Superficial temporal artery to middle cerebral artery (STA-MCA) bypass is a treatment option for hemodynamic insufficiency in the anterior cerebral circulation. Complications associated with extracranial-intracranial bypass surgeries are ischemic strokes caused by bypass failure, wound-healing disorders, and further issues from cerebrospinal fluid (CSF) leakage. CSF leakage can provide pathways for infection. It is well known in general neurosurgery that watertight closure of the dura mater is necessary to prevent such complications. OBJECTIVE: To provide a technical description of TachoSil dural reconstruction in standard STA-MCA bypasses and their follow-up analyses. METHODS: In this technical report with observational follow-up, the dura mater was closed partially by adaptive sutures, and the perforation site of the donor vessel was sealed with TachoSil. TachoSil is a collagen sponge covered with clotting factors that provides hemostatic and sealing effects. RESULTS: Our study included eight cases of standard STA-MCA bypasses that had been operated between July 2015 and September 2016. Follow-up examinations were completed for all patients at 1 month and 6 months after surgery. Duplex and Doppler ultrasound demonstrated regular bypass patency in all patients without increased flow velocity at the perforation sites, which is a possible sign of stenosis. No wound-healing disorders or CSF leakage occurred. No cerebrovascular stroke events were observed. CONCLUSION: Duraplasty with TachoSil enables the elastic reconstruction of the dura perforation gap in standard extracranial-intracranial bypass surgeries.

Percutaneous posterolateral approach for the simulation of a far-lateral disc herniation in an ovine model.

PURPOSE: This work describes a minimally invasive damage model for ovine lumbar discs via partial nucleotomy using a posterolateral approach. METHODS: Two cadavers were dissected to analyze the percutaneous corridor. Subsequently, 28 ovine had their annulus fibrosus punctured via awl penetration under fluoroscopic control and nucleus pulposus tissue removed via rongeur. Efficacy was assessed by animal morbidity, ease of access to T12-S1 disc spaces, and production of a mechanical injury as verified by discography, radiography, and histology. RESULTS: T12-S1 were accessible with minimal nerve damage morbidity. Scar tissue sealed the disc puncture site in all animals within 6 weeks, withstanding 1 MP of intradiscal pressure. Partial nucleotomy led to a significant reduction in intervertebral disk height and an increased histological degeneration score. CONCLUSION: Inducing a reproducible injury pattern of disc degeneration required minimal time, effort, and equipment. The posterolateral approach allows operation on several discs within a single surgery and multiple animal surgeries within a single day.

9.4 T small animal MRI using clinical components for direct translational studies.

BACKGROUND: Magnetic resonance is a major preclinical and clinical imaging modality ideally suited for longitudinal studies, e.g. in pharmacological developments. The lack of a proven platform that maintains an identical imaging protocol between preclinical and clinical platforms is solved with the construction of an animal scanner based on clinical hard- and software. METHODS: A small animal magnet and gradient system were connected to a clinical MR system. Several hardware components were either modified or built in-house to achieve compatibility. The clinical software was modified to account for the different field-of-view of a preclinical MR system. The established scanner was evaluated using clinical QA protocols, and platform compatibility for translational research was verified against clinical scanners of different field strength. RESULTS: The constructed animal scanner operates with the majority of clinical imaging sequences. Translational research is greatly facilitated as protocols can be shared between preclinical and clinical platforms. Hence, when maintaining sequences parameters, maximum similarity between pulses played out on a human or an animal system is maintained. CONCLUSION: Coupling of a small animal magnet with a clinical MR system is a flexible, easy to use way to establish and advance translational imaging capability. It provides cost and labor efficient translational capability as no tedious sequence reprogramming between moieties is required and cross-platform compatibility of sequences facilitates multi-center studies.

Micro-computed tomography, scanning electron microscopy and energy X-ray spectroscopy studies of facet joint degeneration: A comparison to clinical imaging.

Segmental degeneration in the human lumbar spine affects both the intervertebral discs and facet joints. Facet joint degeneration not only affects the cartilage surface, but also alters the cellular properties of the cartilage tissue and the structure of the subchondral bone. The primary focus of this study is the investigation of these microstructural changes that are caused by facet joint degeneration. Microstructural analyses of degenerated facet joint samples, obtained from patients following operative lumbar interbody fusion, have not previously been extensively investigated. This study analyzes human facet joint samples from the inferior articular process using scanning electron microscopy, micro-computed tomography, and energy dispersive X-ray spectroscopy to evaluate parameters of interest in facet joint degeneration such as elemental composition, cartilage layer thickness and cell density, calcification zone thickness, subchondral bone portion, and trabecular bone porosity. These microstructural analyses demonstrate fragmentation, cracking, and destruction of the cartilage layer, a thickened calcification zone, localized calcification areas, and cell cluster formation as pathological manifestations of facet joint degeneration. The detailed description of these microstructural changes is critical for a comprehensive understanding of the pathology of facet joint degeneration, as well as the subsequent development and efficacy analysis of regenerative treatment strategies.