Lateral fenestration of lumbar intervertebral discs in rabbits: development and characterisation of an in vivo preclinical model with multi-modal endpoint analysis

PURPOSE

To evaluate the biological and biomechanical effects of fenestration/microdiscectomy in an in vivo rabbit model, and in doing so, create a preclinical animal model of IVDD.

METHODS

Lateral lumbar IVD fenestration was performed in vivo as single- (L3/4; n = 12) and multi-level (L2/3, L3/4, L4/5; n = 12) fenestration in skeletally mature 6-month-old New Zealand White rabbits. Radiographic, micro-CT, micro-MRI, non-destructive robotic range of motion, and histological evaluations were performed 6- and 12-weeks postoperatively. Independent t tests, one-way and two-way ANOVA and Kruskal-Wallis tests were used for parametric and nonparametric data, respectively. Statistical significance was set at P < 0.05.

RESULTS

All rabbits recovered uneventfully from surgery and ambulated normally. Radiographs and micro-CT demonstrated marked reactive proliferative osseous changes and endplate sclerosis at fenestrated IVDs. Range of motion at the fenestrated disc space was significantly reduced compared to intact controls at 6- and 12-weeks postoperatively (P < 0.05). Mean disc height index percentage for fenestrated IVDs was significantly lower than adjacent, non-operated IVDs for both single and multi-level groups, at 6 and 12 weeks (P < 0.001). Pfirrmann MRI IVDD and histological grading scores were significantly higher for fenestrated IVDs compared to non-operated adjacent and age-matched control IVDs for single and multi-level groups at 6 and 12 weeks (P < 0.001).

CONCLUSIONS

Fenestration, akin to microdiscectomy, demonstrated significant biological, and biomechanical effects in this in vivo rabbit model and warrants consideration by veterinary and human spine surgeons. This described model may be suitable for preclinical in vivo evaluation of therapeutic strategies for IVDD in veterinary and human patients.

The influence of polyimide MP-1™ wear particles on a rodent closed fracture healing model

Joint replacements provide pain free movement for the injured or our aging population. Current prothesis mainly consist of hard metal on metal, or ceramic femoral head on ultra-high-molecular weight polyethylene (UHMWPE). In this study, a rodent fracture model was used to test the influence of wear debris from a high-performance polymer (polyimide MP-1™). Saline, MP-1™ Low Dose in Saline (1%), or MP-1 High Dose (2%) in Saline was injected directly into a standard closed unilateral femoral fracture in 12-week old Sprague Dawley rats (n = 25) for 1, 3 and 6 weeks. Endpoints included radiography, micro-computed tomography, mechanical testing and paraffin histology. No adverse effects from the wear particles were observed from the current study based on radiology, mechanical or histological data. Although the particles were present, histological analysis revealed a progression in healing between the Polyimide treated groups and the non-treated saline control groups over the duration of 1, 3, and 6 weeks, with no inhibition from the particles. The MP-1™ wear debris generated are larger than 1 µm thus are not able to be engulfed by macrophages and cause osteolysis. This family of polymers (polyimides) may be an ideal material to consider for articulating joints and other implants in the human body.

Quantitative analysis of carbon impurity concentrations in GaN epilayers by cathodoluminescence

In this work, a technique for quantifying carbon doping concentrations in GaN:C/AlGaN buffer structures using cathodoluminescence (CL) is presented. The method stems from the knowledge that the blue and yellow luminescence intensity in CL spectra of GaN varies with the carbon doping concentration. By calculating the blue and yellow luminescence peak intensities normalised to the peak GaN near-band-edge intensity for GaN layers of known carbon concentrations, calibration curves that show the change in normalised blue and yellow luminescence intensity with carbon concentration in the 1016 - 1019 cm-3 range were derived at both room temperature and 10 K. The utility of such calibration curves was then examined by testing against an unknown sample containing multiple carbon-doped GaN layers. The results obtained from CL using the normalised blue luminescence calibration curves are in close agreement with those from secondary-ion mass spectroscopy (SIMS). However,the method fails when applying calibration curves obtained from the normalised yellow luminescence likely due to the influence of native VGa defects acting in this luminescence region. Although this work shows that indeed CL can be used as a quantitative tool to measure carbon doping concentrations in GaN:C, it is noted that the intrinsic broadening effects innate to CL can make it difficult to differentiate between the intensity variations in thin ( < 500 nm) multilayered GaN:C structures such as the ones studied in this work.

Mesoderm-derived PDGFRA+ cells regulate the emergence of hematopoietic stem cells in the dorsal aorta

Mouse haematopoietic stem cells (HSCs) first emerge at embryonic day 10.5 (E10.5), on the ventral surface of the dorsal aorta, by endothelial-to-haematopoietic transition. We investigated whether mesenchymal stem cells, which provide an essential niche for long-term HSCs (LT-HSCs) in the bone marrow, reside in the aorta-gonad-mesonephros and contribute to the development of the dorsal aorta and endothelial-to-haematopoietic transition. Here we show that mesoderm-derived PDGFRA⁺ stromal cells (Mesp1^der PSCs) contribute to the haemogenic endothelium of the dorsal aorta and populate the E10.5-E11.5 aorta-gonad-mesonephros but by E13.5 were replaced by neural-crest-derived PSCs (Wnt1^der PSCs). Co-aggregating non-haemogenic endothelial cells with Mesp1^der PSCs but not Wnt1^der PSCs resulted in activation of a haematopoietic transcriptional programme in endothelial cells and generation of LT-HSCs. Dose-dependent inhibition of PDGFRA or BMP, WNT and NOTCH signalling interrupted this reprogramming event. Together, aorta-gonad-mesonephros Mesp1^der PSCs could potentially be harnessed to manufacture LT-HSCs from endothelium.

The efficacy of a nanosynthetic bone graft substitute as a bone graft extender in rabbit posterolateral fusion

BACKGROUND CONTEXT

Synthetic bone graft substitutes are commonly used in spinal fusion surgery. Preclinical data in a model of spinal fusion to support their efficacy is an important component in clinical adoption to understand how these materials provide a biological and mechanical role in spinal fusion.

PURPOSE

To evaluate the in vivo response of a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft compared to autograft alone or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft in a rabbit spinal fusion model.

STUDY DESIGN

Efficacy of a nanosynthetic silicated calcium phosphate putty as an extender to autograft was studied in an experimental animal model of posterolateral spinal fusion at 6, 9, 12 and 26 weeks, compared to a predicate device.

METHODS

Skeletally mature female New Zealand White rabbits (70) underwent single level bilateral posterolateral intertransverse process lumbar fusion, using either autograft alone (AG), a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft (1:1), or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft (1:1). Iliac crest autograft was harvested for each group, and a total of 2 cc of graft material was implanted in the posterolateral gutters per side. Fusion success was assessed at all time points by manual palpation, radiographic assessment, micro-CT and at 12 weeks only using non-destructive range of motion testing. Tissue response, bone formation and graft resorption were assessed by decalcified paraffin histology and by histomorphometry of PMMA embedded sections.

RESULTS

Assessment of fusion by manual palpation at the 12 week endpoint showed 7 out of 8 (87.5%) bilateral fusions in the OstP extender group, 4 out of 8 (50%) fusions in the MasP extender group, and 6 out of 8 (75%) fusions in the autograft alone group. Similar trends were observed with fusion scores of radiographic and micro-CT data. Histology showed a normal healing response in all groups, and increased bone formation in the OstP extender group at all timepoints compared to the MasP extender group. New bone formed directly on the OstP granule surface within the fusion mass while this was not a feature of the Collagen-Biphasic CaP material. After 26 weeks the OstP extender group exhibited 100% fusions (5 out of 5) by all measures, whereas the MasP extender group resulted in bilateral fusions in 3 out of 5 (60%), assessed by manual palpation, and fusion of only 20 and 0% by radiograph and micro-CT scoring, respectively. Histology at 26 weeks showed consistent bridging of bone between the transverse processes in the Ost P extender group, but this was not observed in the MasP extender group.

CONCLUSIONS

The nanosynthetic bone graft substituted studied here, used as an extender to autograft, showed a progression to fusion between 6 and 12 weeks that was similar to that observed with autograft alone, and showed excellent fusion outcomes, bone formation and graft resorption at 26 weeks.

CLINICAL SIGNIFICANCE

This preclinical study showed that the novel nanosynthetic silicated CaP putty, when combined with autograft, achieved equivalent fusion outcomes to autograft. The development of synthetic bone grafts that demonstrate efficacy in such models can eliminate the need for excessive autograft harvest and results from this preclinical study supports their effective use in spinal fusion surgery.

Temporal response of an injectable calcium phosphate material in a critical size defect

BACKGROUND

Calcium phosphate-based bone graft substitutes are used to facilitate healing in bony defects caused by trauma or created during surgery. Here, we present an injectable calcium phosphate-based bone void filler that has been purposefully formulated with hyaluronic acid to offer a longer working time for ease of injection into bony defects that are difficult to access during minimally invasive surgery.

METHODS

The bone substitute material deliverability and physical properties were characterized, and in vivo response was evaluated in a critical size distal femur defect in skeletally mature rabbits to 26 weeks. The interface with the host bone, implant degradation, and resorption were assessed with time.

RESULTS

The calcium phosphate bone substitute material could be injected as a paste within the working time window of 7-18 min, and then self-cured at body temperature within 10 min. The material reached a maximum ultimate compressive strength of 8.20 ± 0.95 MPa, similar to trabecular bone. The material was found to be biocompatible and osteoconductive in vivo out to 26 weeks, with new bone formation and normal bone architecture observed at 6 weeks, as demonstrated by histological evaluation, microcomputed tomography, and radiographic evaluation.

CONCLUSIONS

These findings show that the material properties and performance are well suited for minimally invasive percutaneous delivery applications.

Dislocations at coalescence boundaries in heteroepitaxial GaN/sapphire studied after the epitaxial layer has completely coalesced

We have performed cross-sectional scanning capacitance microscopy (SCM), cathodoluminescence (CL) microscopy in the scanning electron microscope (SEM) and transmission electron microscopy (TEM) all on the same few-micron region of a GaN/sapphire sample. To achieve this, it was necessary to develop a process flow which allowed the same features viewed in a cleaved cross-section to be traced from one microscope to the next and to adapt the focused ion beam preparation of the TEM lamella to allow preparation of a site-specific sample on a pre-cleaved cross-section. Growth of our GaN/sapphire samples involved coalescence of three-dimensional islands to form a continuous film. Highly doped marker layers were included in the sample so that coalescence boundaries formed late in the film growth process could be identified in SCM and CL. Using TEM, we then identified one or more dislocations associated with each of several such late-coalescing boundaries. In contrast, previous studies have addressed coalescence boundaries formed earlier in the growth process and have shown that early-stage island coalescence does not lead to dislocation formation.

Directly correlated microscopy of trench defects in InGaN quantum wells

Directly correlated measurements of the surface morphology, light emission and subsurface structure and composition were carried out on the exact same nanoscale trench defects in InGaN quantum well (QW) structures. Multiple scanning probe, scanning electron and transmission electron microscopy techniques were used to explain the origin of their unusual emission behaviour and the relationship between surface morphology and cathodoluminescence (CL) redshift. Trench defects comprise of an open trench partially or fully enclosing material in InGaN QWs with different CL emission properties to their surroundings. The CL redshift was shown to typically vary with the width of the trench and the prominence of the material enclosed by the trench above its surroundings. Three defects, encompassing typical and atypical features, were prepared into lamellae for transmission electron microscopy (TEM). A cross marker technique was used in the focused ion beam-scanning electron microscope (FIB-SEM) to centre the previously characterised defects in each lamella for further analysis. The defects with wider trenches and strong redshifts in CL emission had their initiating basal-plane stacking fault (BSF) towards the bottom of the QW stack, while the BSF formed near the top of the QW stack for a defect with a narrow trench and minimal redshift. The raised-centre, prominent defect showed a slight increase in QW thickness moving up the QW stack while QW widths in the level-centred defect remained broadly constant. The indium content of the enclosed QWs increased above the BSF positions up to a maximum, with an increase of approximately 4% relative to the surroundings seen for one defect examined. Gross fluctuations in QW width (GWWFs) were present in the surrounding material in this sample but were not seen in QWs enclosed by the defect volumes. These GWWFs have been linked with indium loss from surface step edges two or more monolayers high, and many surface step edges appear pinned by the open trenches, suggesting another reason for the higher indium content seen in QWs enclosed by trench defects.

Point Defects in InGaN/GaN Core–Shell Nanorods: Role of the Regrowth Interface

Core-shell nanorod based light-emitting diodes (LEDs) with their exposed non-polar surfaces have the potential to overcome the limitations of planar LEDs by circumventing the quantum confined stark effect. In this experiment, InGaN/GaN core-shell nanorods were fabricated by a combination of top-down etching and bottom-up regrowth using metal-organic vapour phase epitaxy. When viewing the nanorods along their long axis, monochromatic cathodoluminescence maps taken at the GaN near-band-edge emission energy (3.39 eV) reveal a ring-like region of lower emission intensity. The diameter of this ring is found to be 530 (±20)nm corresponding to the ∼510 nm diameter nickel etch masks used to produce the initial GaN nanopillars. Thus, the dark ring corresponds to the regrowth interface. To understand the origin of the ring, scanning transmission electron microscopy (STEM) and cathodoluminescence (CL) hyperspectral mapping at 10K were performed. STEM imaging reveals the absence of extended defects in the nanorods and indeed near the regrowth interface. Monochromatic CL maps recorded at 10K show that the ring remains dark for monochromatic maps taken at the GaN near-band-edge emission energy (3.47 eV) but is bright when considering the donor-acceptor pair emission energy (3.27 eV). This peculiar anticorrelation indicates that the dark ring originates from an agglomeration of point defects associated with donor-acceptor pair emission. The point defects are incorporated and buried at the GaN regrowth interface from the chemical and/or physical damage induced by etching and lower the radiative recombination rate; limiting the radiative efficiency close to the regrowth interface.

Single level posterolateral lumbar fusion in a New Zealand White rabbit (Oryctolagus cuniculus) model: Surgical anatomy, operative technique, autograft fusion rates, and perioperative care

INTRODUCTION

The posterolateral lumbar fusion (PLF) New Zealand White (NZW) (Oryctolagus cuniculus) rabbit model is a long-standing surgical technique for the preclinical evaluation of materials for spinal fusion. A detailed understanding of lumbar spine anatomy and perioperative care requirements of rabbits is imperative for correct execution of the model both scientifically and ethically. This study describes the preoperative procedures and surgical techniques used in single level PLF in a NZW rabbit model as it pertains to the animal husbandry, lumbar spine anatomy, anesthesia, surgical approach, and perioperative care of rabbits in a research setting.

MATERIALS AND METHODS

We describe the surgical technique and perioperative patient care for single level PLF in a NZW rabbit model. Medical records from a single research facility were retrospectively reviewed for adult NZW rabbits that underwent single level PLF (L4-L5) between January 2016 and December 2019. The number of lumbar vertebrae per rabbit, fusion rates at 12 weeks using iliac crest autograft and complications are reported. Skeletal maturity was confirmed by preoperative fluoroscopic and radiographic documented closure of hindlimb physes.

RESULTS

The PLF rabbit surgical model and perioperative patient care is described. PLF was performed in 868 adult female entire NZW rabbits. The majority of rabbits had seven lumbar vertebrae (620/868; 71.4%), followed by six (221/868; 25.5%), and eight (27/868; 3.1%). Fusion rates at 12 weeks for PLF using iliac crest autograft as assessed by manual palpation and radiographic assessment was 76.9% and 70.0%, respectively. Postoperative complications included occasional partial autograft site wound dehiscence due to self-trauma.

CONCLUSIONS

For PLF rabbit models, a detailed understanding of the surgical technique, rabbit lumbar anatomy including number of lumbar vertebrae, and dietary and husbandry requirements of rabbits, is essential for execution of the model and animal welfare.

Moment arm function dictates patella sagittal height anatomy: Rabbit epiphysiodesis model alters limb length ratios and subsequent patellofemoral anatomical development

Patellofemoral anatomical dysplasia is associated with patellofemoral instability and pain. The closure of the knee physis occurs at the same age as the peak incidence of patellofemoral dislocation. This study determined the effect on the patellofemoral anatomical development in a rabbit epiphysiodesis model. Twenty-four skeletally immature New Zealand White rabbits were divided into three groups (a) distal femur epiphysiodesis (FE) (b) proximal tibia epiphysiodesis (TE) (c) control; no epiphysiodesis (C) performed at 6 weeks of age. The primary endpoint was shape analysis using three-dimensional reconstructions of micro-computed tomographys (CTs) performed at 30 weeks of age. The limb length ratios (femur:tibia) were significantly different for both FE (mean 0.72, SD 0.0381, P < .001) and TE (mean 0.91, SD 0.0383, P < .001) treatment groups compared to control (mean 0.81, SD 0.0073). Patella height, as measured from the most distal point of the patella to the tibial joint surface (modified Caton-Deschamps measurement), was lower (baja) in the FE and higher (alta) for the TE, compared with the control group. Our findings suggest femoral and tibial shortening can influence the development of the patellofemoral joint, which may be dictated by moment arm function and is potentially responsible for the etiology of patella alta. Future studies are warranted to explore this association further with the view for the development of treatment options for patella alta in human patients.

Induction of muscle-regenerative multipotent stem cells from human adipocytes by PDGF-AB and 5-azacytidine

Terminally differentiated murine osteocytes and adipocytes can be reprogrammed using platelet-derived growth factor-AB and 5-azacytidine into multipotent stem cells with stromal cell characteristics. We have now optimized culture conditions to reprogram human adipocytes into induced multipotent stem (iMS) cells and characterized their molecular and functional properties. Although the basal transcriptomes of adipocyte-derived iMS cells and adipose tissue-derived mesenchymal stem cells were similar, there were changes in histone modifications and CpG methylation at cis-regulatory regions consistent with an epigenetic landscape that was primed for tissue development and differentiation. In a non-specific tissue injury xenograft model, iMS cells contributed directly to muscle, bone, cartilage, and blood vessels, with no evidence of teratogenic potential. In a cardiotoxin muscle injury model, iMS cells contributed specifically to satellite cells and myofibers without ectopic tissue formation. Together, human adipocyte-derived iMS cells regenerate tissues in a context-dependent manner without ectopic or neoplastic growth.

Comparative osteoconductivity of bone void fillers with antibiotics in a critical size bone defect model

The study aimed to evaluate the comparative osteoconductivity of three commercially available bone void fillers containing gentamicin with respect to new bone, growth, host tissue response and resorption of the implant material. Defects were created in the cancellous bone of the distal femur and proximal tibia of 12-skeletally mature sheep and filled with three commercially available bone void fillers containing gentamicin (Stimulan-G, Cerament-G, Herafill-G). Peripheral blood was taken pre-operatively and at the time of implantation, as well as at intermittent timepoints following surgery to determine systemic gentamicin levels (5-,15- and 30- minutes, 1, 2, 3, 6, 12, 24, 48- and 72-hours, 3-, 6- and 12-weeks). Decalcified, embedded samples were stained with haematoxylin and eosin (H&E) and used to assess the host tissue response and the formation of new bone in the presence of test implant materials. No adverse reactions were noted at harvest at any time points for any cancellous implantation sites with the various implant materials. Comparative microCT analysis of the Stimulan-G, Cerament-G and Herafill-G test materials revealed a similar increase in bone surface area and volume between animals implanted with Stimulan-G or Cerament-G test materials. Animals implanted with Herafill-G test materials demonstrated the lowest increases in bone volume and surface area of the test materials tested, at levels similar to the negative control sites. By 12-weeks, Stimulan-G defects were completely closed with mature bone and bone marrow whilst the Cerament-G material was still present after 12 weeks by histological examination. In conclusion, this study demonstrated differences in the bone regenerative capacity of a range of bone void fillers in an in vivo setting.

Cross-shaped markers for the preparation of site-specific transmission electron microscopy lamellae using focused ion beam techniques

We describe the use of a cross-shaped platinum marker deposited using electron-beam-induced deposition (EBID) in a focused ion beam - scanning electron microscope (FIB-SEM) system to facilitate site-specific preparation of a TEM foil containing a trench defect in an InGaN/GaN multiple quantum well structure. The defect feature is less than 100 nm wide at the surface. The marker is deposited prior to the deposition of a protective platinum strap (also by EBID) with the centre of the cross indicating the location of the feature of interest, while the arms of the square cross make an acute angle of 45° with the strap's long axis. During the ion-beam thinning process, the marker may be viewed in cross-section from both sides of the sample alternately, and the coming together of the features relating to the arms of the cross indicates increasing proximity to the feature of interest. Although this approach does allow increased precision in locating the region of interest during thinning, it also increases the time required to complete the sample preparation. Hence, this method is particularly well suited to directly correlated multi-microscopy investigations in previously characterised material where high yield and the precise location are more important than preparation time. In addition to TEM lamella preparation, this method could equally be useful for preparing site-specific atom probe tomography (APT) samples.

Effects of SCCO2, Gamma Irradiation, and Sodium Dodecyl Sulfate Treatments on the Initial Properties of Tendon Allografts

Sterile and decellularized allograft tendons are viable biomaterials used in reconstructive surgeries for dense connective tissue injuries. Established allograft processing techniques including gamma irradiation and sodium dodecyl sulfate (SDS) can affect tissue integrity. Supercritical carbon dioxide (SCCO₂) represents a novel alternative that has the potential to decellularize and sterilize tendons with minimized exposure to denaturants, shortened treatment time, lack of toxic residues, and superior tissue penetration, and thus efficacy. This study attempted to develop a single-step hybrid decellularization and sterilization protocol for tendons that involved SCCO₂ treatment with various chemical additives. The processed tendons were evaluated with mechanical testing, histology, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. Uniaxial mechanical testing showed that tendons treated with SCCO₂ and additive NovaKill^TM Gen2 and 0.1% SDS had significantly higher (p < 0.05) ultimate tensile stress (UTS) and Young's modulus compared to gamma-irradiated and standard-SDS-treated tendons. This was corroborated by the ultrastructural intactness of SCCO₂-treated tendons as examined by SEM and FTIR spectroscopy, which was not preserved in gamma-irradiated and standard SDS-treated tendons. However, complete decellularization was not achieved by the experimented SCCO₂-SDS protocols used in this study. The present study therefore serves as a concrete starting point for development of an SCCO₂-based combined sterilization and decellularization protocol for allograft tendons, where additive choice is to be optimized.

Inception of early-life allergen-induced airway hyperresponsiveness is reliant on IL-13+CD4+ T cells

Airway hyperresponsiveness (AHR) is a critical feature of wheezing and asthma in children, but the initiating immune mechanisms remain unconfirmed. We demonstrate that both recombinant interleukin-33 (rIL-33) and allergen [house dust mite (HDM) or Alternaria alternata] exposure from day 3 of life resulted in significantly increased pulmonary IL-13⁺CD4⁺ T cells, which were indispensable for the development of AHR. In contrast, adult mice had a predominance of pulmonary Lin^negCD45⁺CD90⁺IL-13⁺ type 2 innate lymphoid cells (ILC2s) after administration of rIL-33. HDM exposure of neonatal IL-33 knockout (KO) mice still resulted in AHR. However, neonatal CD4^creIL-13 KO mice (lacking IL-13⁺CD4⁺ T cells) exposed to allergen from day 3 of life were protected from AHR despite persistent pulmonary eosinophilia, elevated IL-33 levels, and IL-13⁺ ILCs. Moreover, neonatal mice were protected from AHR when inhaled Acinetobacter lwoffii (an environmental bacterial isolate found in cattle farms, which is known to protect from childhood asthma) was administered concurrent with HDM. A. lwoffii blocked the expansion of pulmonary IL-13⁺CD4⁺ T cells, whereas IL-13⁺ ILCs and IL-33 remained elevated. Administration of A. lwoffii mirrored the findings from the CD4^creIL-13 KO mice, providing a translational approach for disease protection in early life. These data demonstrate that IL-13⁺CD4⁺ T cells, rather than IL-13⁺ ILCs or IL-33, are critical for inception of allergic AHR in early life.

Evaluation of comparative soft tissue response to bone void fillers with antibiotics in a rabbit intramuscular model

Management of osseous and soft tissue dead space can be a significant challenge in the clinical setting. Calcium sulphate and calcium phosphate-based biomaterials are increasingly being used as alternatives to PMMA for local release of antibiotics, in particular to fill dead space following surgical debridement. This study aims to observe the in-vivo absorption characteristics and tissue response of three commercially available calcium sulphate-based materials combined with gentamicin in an established soft tissue rabbit model. The implant materials (1cc) were placed into four intramuscular sites in 18 New Zealand White rabbits (n = 6). In-life blood samples and radiographs were taken from each animal following implantation. Animals were sacrificed at 0, 1, 7, 21, 42 and 63 days post-operatively (n = 3) and implant sites analysed by micro-computed tomography and histology. Radiographically and histologically, recrystallized calcium sulphate (RCS) absorbed the fastest with complete absorption by day 21. Calcium sulphate/HA composite (CSHA) and Calcium sulphate/calcium carbonate (CSCC) absorbed slower and were detectable at day 63. Residual bead analysis revealed the presence of detectable gentamicin at 24 h and 7 days for CSHA and RCS but none in CSCC. Systemic levels of gentamicin were only detected between 1 h and 24 h. Serological inflammatory cytokine expression for IL-6, TNF-α and IL-1β indicated no unusual inflammatory response to the implanted materials. Calcium sulphate materials loaded with gentamicin are effective in resolving a surgically created dead space without eliciting any adverse host response.

Suture wear particles cause a significant inflammatory response in a murine synovial airpouch model

Background

Commonly used contemporary orthopaedic sutures have been identified as a potential causative factor in the development of post-arthroscopic glenohumeral chondrolysis. Currently, little is known about the body’s immune response to these materials. The aim of this study was to examine the biological response of synovial tissue to three commonly used orthopaedic sutures, using a murine airpouch model.

Methods

Fifty rats were used in this study (ten per group). An airpouch was created in each rat, and test materials were implanted. Test materials consisted of an intact polyethylene terephthalate suture with a polybutilate coating (suture A), an intact polyethylene suture braided around a central polydiaxannone core (suture B), an intact polyethylene/polyester cobraid suture with a silicone coating (suture C), and particles of suture C (particles C). Rats were sacrificed at 1 or 4 weeks following implantation. Histological (multinucleated giant cell count) and immunohistochemical (expression of matrix metalloproteinases MMP-1,-2,-3,-9,-13) markers of inflammation were examined.

Results

Multinucleated giant cells were present in all specimens containing suture material but not in the control specimens. No significant differences were found in the number of giant cells between the intact suture groups at either time point. Significantly higher numbers of giant cells were noted in the particles C group compared to the intact suture C group at both time points (p = 0.021 at 1 week, p = 0.003 at 4 weeks). Quantitative analysis of immunohistochemical staining expression at 4 weeks showed that significantly more MMP (-1,-2,-9,-13) was expressed in the particles C group than the intact suture C group (p = 0.024, p = 0.009, p = 0.002, and p = 0.007 for MMP-1, MMP-2, MMP-9, and MMP-13, respectively). No significant difference was seen in the expression of MMP-3 (p = 0.058).

Conclusions

There were no differences observed between the biological reactivity of commonly used intact orthopaedic sutures A, B, and C. However, wear particles of suture C elicited a significantly greater inflammatory response than intact suture alone. This was confirmed by increased numbers of multinucleated giant cells as well as MMP ( -1,-2,-9,-13) expression. Further studies are needed to determine whether this inflammatory response may play a role in the development of post-arthroscopic glenohumeral chondrolysis or interfere with biological healing. These findings have important clinical implications relating to surgical technique and surgical implant design.

Resonant photoluminescence studies of carrier localisation in c-plane InGaN/GaN quantum well structures

In this paper we report on changes in the form of the low temperature (12 K) photoluminescence spectra of an InGaN/GaN quantum well structure as a function of excitation photon energy. As the photon energy is progressively reduced we observe at a critical energy a change in the form of the spectra from one which is determined by the occupation of the complete distribution of hole localisation centres to one which is determined by the resonant excitation of specific localisation sites. This change is governed by an effective mobility edge whereby the photo-excited holes remain localised at their initial energy and are prevented from scattering to other localisation sites. This assignment is confirmed by the results of atomistic tight binding calculations which show that the wave function overlap of the lowest lying localised holes with other hole states is low compared with the overlap of higher lying hole states with other higher lying hole states.

Periostin as a marker of mucosal remodelling in chronic rhinosinusitis

BACKGROUND

Although extracellular matrix (ECM) proteins are associated with irreversible lower airway changes, the relationship with upper airway remodelling which occurs during chronic rhinosinusitis (CRS) is poorly understood. This study assessed the expression of ECM proteins periostin, fibulin-1, fibronectin and collagenIV in nasal mucosa of patients with and without histologic features of remodelling.

METHODS

A cross-sectional study of sinonasal mucosal biopsies taken from patients, undergoing surgery for CRS was performed, where patients were grouped according to remodelling, defined by basement membrane thickening (BMT over 7.5 micrometer) and subepithelial fibrosis. An overall view and three random fields of immunostained tissue sections that included epithelium, basement membrane and submucosa, were imaged using Zeiss Zen software. The area and intensity of positive staining were scored by two blinded observers, using a 12-point ordinal scale of weak to strong.

RESULTS

65 patients (47.6 +/- 13.4years, 44.6% female) were assessed. Patients were grouped as controls 26.2%, BMT/no fibrosis 38.5% or BMT and fibrosis 33.8%. Stronger grade of periostin expression was associated with remodelling changes and tissue eosinophilia over 10/HPF. Fibulin-1, fibronectin and collagenIV did not differ.

CONCLUSION

Periostin expression was associated with the presence of BMT, fibrosis and tissue eosinophilia and may identify patients undergoing remodelling changes.

Periostin as a marker of mucosal remodelling in chronic rhinosinusitis

BACKGROUND

Although extracellular matrix (ECM) proteins are associated with irreversible lower airway changes, the relationship with upper airway remodelling which occurs during chronic rhinosinusitis (CRS) is poorly understood. This study assessed the expression of ECM proteins periostin, fibulin-1, fibronectin and collagenIV in nasal mucosa of patients with and without histologic features of remodelling.

METHODS

A cross-sectional study of sinonasal mucosal biopsies taken from patients, undergoing surgery for CRS was performed, where patients were grouped according to remodelling, defined by basement membrane thickening (BMT over 7.5 micrometer) and subepithelial fibrosis. An overall view and three random fields of immunostained tissue sections that included epithelium, basement membrane and submucosa, were imaged using Zeiss Zen software. The area and intensity of positive staining were scored by two blinded observers, using a 12-point ordinal scale of weak to strong.

RESULTS

65 patients (47.6 +/- 13.4years, 44.6% female) were assessed. Patients were grouped as controls 26.2%, BMT/no fibrosis 38.5% or BMT and fibrosis 33.8%. Stronger grade of periostin expression was associated with remodelling changes and tissue eosinophilia over 10/HPF. Fibulin-1, fibronectin and collagenIV did not differ.

CONCLUSION

Periostin expression was associated with the presence of BMT, fibrosis and tissue eosinophilia and may identify patients undergoing remodelling changes.

InGaN µLEDs integrated onto colloidal quantum dot functionalized ultra-thin glass

Red-, orange-, and green-emitting integrated optoelectronic sources are demonstrated by transfer printing blue InGaN µLEDs onto ultra-thin glass platforms functionally enhanced with II-VI colloidal quantum dots (CQDs). The forward optical power conversion efficiency of these heterogeneously integrated devices is, respectively, 9%, 15%, and 14% for a blue light absorption over 95%. The sources are demonstrated in an orthogonal frequency division multiplexed (OFDM) visible light communication link reaching respective data transmission rates of 46 Mbps, 44 Mbps and 61 Mbps.

Polarisation-controlled single photon emission at high temperatures from InGaN quantum dots

Solid-state single photon sources with polarisation control operating beyond the Peltier cooling barrier of 200 K are desirable for a variety of applications in quantum technology. Using a non-polar InGaN system, we report the successful realisation of single photon emission with a g⁽²⁾(0) of 0.21, a high polarisation degree of 0.80, a fixed polarisation axis determined by the underlying crystallography, and a GHz repetition rate with a radiative lifetime of 357 ps at 220 K in semiconductor quantum dots. The temperature insensitivity of these properties, together with the simple planar epitaxial growth method and absence of complex device geometries, demonstrates that fast single photon emission with polarisation control can be achieved in solid-state quantum dots above the Peltier temperature threshold, making this system a potential candidate for future on-chip applications in integrated systems.

Critical Size Bone Defect Healing Using Collagen-Calcium Phosphate Bone Graft Materials

The need for bone graft materials to fill bony voids or gaps that are not related to the intrinsic stability of the bone that arise due to trauma, tumors or osteolysis remains a clinically relevant and significant issue. The in vivo response of collagen-tricalcium phosphate bone graft substitutes was evaluated in a critical size cancellous defect model in skeletally mature rabbits. While the materials were chemically virtually identical, new bone formation, implant resorption and local in vivo responses were significantly different. Differences in the in vivo response may be due, in part, collagen source and processing which influences resorption profiles. Continued improvements in processing and manufacturing techniques of collagen-tricalcium phosphate bone graft substitutes can result in osteoconductive materials that support healing of critical size bone defects even in challenging pre-clinical models.

The histological and elemental characterisation of corrosion particles from taper junctions

OBJECTIVES

This study aimed to characterise and qualitatively grade the severity of the corrosion particles released into the hip joint following taper corrosion.

METHODS

The 26 cases examined were CoC/ABG Modular (n = 13) and ASR/SROM (n = 13). Blood serum metal ion levels were collected before and after revision surgery. The haematoxylin and eosin tissue sections were graded on the presence of fibrin exudates, necrosis, inflammatory cells and corrosion products. The corrosion products were identified based on visible observation and graded on abundance. Two independent observers blinded to the clinical patient findings scored all cases. Elemental analysis was performed on corrosion products within tissue sections. X-Ray diffraction was used to identify crystalline structures present in taper debris.

RESULTS

The CoC/ABG Modular patients had a mean age of 64.6 years (49.4 to 76.5) and ASR/SROM patients had a mean age of 58.2 years (33.3 to 85.6). The mean time in situ for CoC/ABG was 4.9 years (2 to 6.4) and ASR/SROM was 6.1 years (2.5 to 8.1). The blood serum metal ion concentrations reduced following revision surgery with the exception of Cr levels within CoC/ABG. The grading of tissue sections showed that the macrophage response and metal debris were significantly higher for the ASR/SROM patients (p < 0.001). The brown/red particles were significantly higher for ASR/SROM (p < 0.001). The taper debris contained traces of titanium oxide, chromium oxide and aluminium nitride.

CONCLUSION

This study characterised and qualitatively graded the severity of the corrosion particles released into the hip joint from tapers that had corrosion damage.Cite this article: S. Munir, R. A. Oliver, B. Zicat, W. L. Walter, W. K. Walter, W. R. Walsh. The histological and elemental characterisation of corrosion particles from taper junctions. Bone Joint Res 2016;5:370-378. DOI: 10.1302/2046-3758.59.2000507.

Evaluation of Transbronchial Lung Cryobiopsy Size and Freezing Time: A Prognostic Animal Study

BACKGROUND

Transbronchial lung biopsy using a cryoprobe is a novel way of sampling lung parenchyma. Correlation of freezing time with biopsy size and complications has not been evaluated in vivo.

OBJECTIVES

The primary aim of the study is to evaluate the correlation between transbronchial cryobiopsy freezing time and size. The secondary aims are to evaluate histological quality of the biopsy and evaluate procedure-associated complications.

METHODS

Transbronchial lung cryobiopsies were obtained from two anaesthetised sheep using a 1.9-mm cryoprobe inserted into a flexible bronchoscope under fluoroscopic guidance. Freezing times ranged from 1 to 6 s (n = 49). The cryobiopsies were evaluated histologically with respect to their size and quality. Complications of bleeding and pneumothorax were recorded.

RESULTS

The mean cross-sectional area of the cryobiopsy ranged from 4.7 ± 2.1 to 15.7 ± 15.3 mm2. There was a significant positive correlation between increasing freezing time and cryobiopsy cross-sectional area (p = 0.028). All biopsies contained lung tissue with preserved parenchyma. Crush and freeze artefacts were not observed and tissue architecture was intact in all specimens. Small blood vessels and terminal bronchioles were observed in 88% of specimens. All cryobiopsies caused nil or mild haemorrhage with the exception of only 1 episode of severe haemorrhage at 6 s freezing time. Pneumothoraces occurred at 2, 5 and 6 s freezing time and required chest tube insertion. The most significant haemorrhage and pneumothoraces occurred at 5 and 6 s. Our results suggest an initial freezing time of 3 s can provide the maximal biopsy size while minimising major complications.

CONCLUSION

The optimal transbronchial cryobiopsy freezing time is initially 3 s. This time is associated with minimal complications and large artefact-free biopsies.

Development of a Novel Model for the Assessment of Dead-Space Management in Soft Tissue

Following extensive surgical debridement in the treatment of infection, a “dead space” can result following surgical closure that can fill with hematoma, an environment conducive to bacterial growth. The eradication of dead space is essential in order to prevent recurrent infection. This study describes a novel small animal model to investigate dead-space management in muscle tissue. Two absorbable test materials were implanted in each animal; beads of calcium sulfate alone, and beads loaded with vancomycin and tobramycin. In-life blood samples and radiographs were taken from each animal following implantation. Animals were sacrificed at 1, 7, 21, 42, and 63 days post-operatively (n = 4), and implant sites were analysed by micro-computed tomography, histology and immunohistochemistry. Complete resorption was confirmed radiographically at 3 weeks post-implantation. Histologically, the host tissue response to both materials was identical, and subsequent healing at the implant sites was observed with no dead space remaining. Vancomycin was not detected in blood serum. However, peak tobramycin levels were detected in all animals at 6 hours post-implantation with no detectable levels in any animals at 72 hours post implantation. Serological inflammatory cytokine expression for IL-6, TNF-α and IL-1β indicated no unusual inflammatory response to the implanted materials or surgical procedure. The model was found to be convenient and effective for the assessment of implant materials for management of dead space in muscle tissue. The two materials tested were effective in resolving the surgically created dead space, and did not elicit any unexpected adverse host response.

Transdermal fentanyl and its use in ovine surgery

Fentanyl delivered via a transdermal patch has the potential to decrease the need for post-operative handling of sheep undergoing surgical procedures. Two studies were performed to test: (1) the ideal timing for the application of pre-emptive analgesic patches and (2) the efficacy of a 2 µg/kg/h dose, as extrapolated from other species. The first study had sheep divided into two groups. Group 1 had a fentanyl patch applied for 24 h prior to a patch change and group 2 had a fentanyl patch applied 72 h prior to a change. The second study applied the results obtained in the first and tested the efficacy of 2 µg/kg/h as an effective dose in an orthopaedic surgical environment. Results indicated that the ideal time for pre-emptive fentanyl patch administration is 24-36 h prior to surgery and that 2 µg/kg/h is an effective minimum therapeutic dose rate for the use of fentanyl as an analgesic in an orthopaedic surgical environment.

The Masquelet technique for membrane induction and the healing of ovine critical sized segmental defects

The healing of critical sized segmental defects is an ongoing clinical problem. No method has achieved pre-eminence. The Masquelet technique is a relatively new innovation involving the induction of a fibrous tissue membrane around the bone defect site taking advantage of the body's foreign body reaction to the presence of a polymethylmethacrylate (PMMA) spacer. The aim of this study was to investigate the properties and characteristics of this induced membrane and its effectiveness when used in conjunction with allograft or an allograft/autograft mix as filler materials in an ovine critical sized defect model. The resultant induced membrane was found to be effective in containing the graft materials in situ. It was demonstrated to be an organised pseudosynovial membrane which expressed bone morphogenic protein 2 (BMP2), transforming growth factor-beta (TGFβ), vascular endothelial growth factor (VEGF), von Willerbrand factor (vWF), interleukin 6 (IL-6) and interleukin 8 (IL-8). While more new bone growth was evident in the test groups compared to the controls animals at 12 weeks, the volumes were not statistically different and no defects were fully bridged. Of the two graft material groups, the allograft/autograft mix was shown to have a more rapid graft resorption rate than the allograft only group. While the Masquelet technique proved effective in producing a membrane to enclose graft materials, its ability to assist in the healing of critical sized segmental defects when compared to empty controls remained inconclusive.

Fibulin-1 predicts disease progression in patients with idiopathic pulmonary fibrosis

BACKGROUND

The underlying mechanisms of idiopathic pulmonary fibrosis (IPF) are unknown. This progressive disease has high mortality rates, and current models for prediction of mortality have limited value in identifying which patients will progress. We previously showed that the glycoprotein fibulin-1 is involved in enhanced proliferation and wound repair by mesenchymal cells and, thus, may contribute to lung fibrosis in IPF.

METHODS

Serum, lung tissue, and lung function values were obtained from four independent locations (Sydney, NSW, and Perth, WA, Australia; San Francisco, CA; and Modena, Italy). Patients with IPF were followed for a minimum of 1 year and progression was defined as a significant decline in lung function or death. Primary parenchymal lung fibroblasts of 15 patients with and without IPF were cultured under nonstimulatory conditions. Fibulin-1 levels in serum, and secreted or deposited by fibroblasts, were measured by western blot and in lung tissue by immunohistochemistry.

RESULTS

Serum fibulin-1 levels were increased in patients with IPF compared with subjects without lung disease (P = .006). Furthermore, tissue fibulin-1 levels were increased in patients with IPF (P = .02) and correlated negatively with lung function (r = -0.9, P < .05). Primary parenchymal fibroblasts from patients with IPF produced more fibulin-1 than those from subjects without IPF (P < .05). Finally, serum fibulin-1 levels at first blood draw predicted disease progression in IPF within 1 year (area under the curve , 0.71; 95% CI, 0.57-0.86; P = .012).

CONCLUSIONS

Fibulin-1 is a novel potential biomarker for disease progression in IPF and raises the possibility that it could be used as a target for the development of new treatments.

Ovine model for critical-size tibial segmental defects

A segmental tibial defect model in a large animal can provide a basis for testing materials and techniques for use in nonunions and severe trauma. This study reports the rationale behind establishing such a model and its design and conclusions. After ethics approval of the study, aged ewes (older than 5 y; n = 12) were enrolled. A 5-cm mid diaphyseal osteoperiosteal defect was made in the left tibia and was stabilized by using an 8-mm stainless-steel cross-locked intramedullary nail. Sheep were euthanized at 12 wk after surgery and evaluated by using radiography, microCT, and soft-tissue histology techniques. Radiology confirmed a lack of hard tissue callus bridging across the defect. Volumetric analysis based on microCT showed bone growth across the 16.5 cm(3) defect of 1.82 ± 0.94 cm(3). Histologic sections of the bridging tissues revealed callus originating from both the periosteal and endosteal surfaces, with fibrous tissue completing the bridging in all instances. Immunohistochemistry was used to evaluate the quality of the healing response. Clinical, radiographic, and histologic union was not achieved by 12 wk. This model may be effective for the investigation of surgical techniques and healing adjuncts for nonunion cases, where severe traumatic injury has led to significant bone loss.

Lumbar spinal fusion with β-TCP granules and variable Escherichia coli-derived rhBMP-2 dose

BACKGROUND CONTEXT

The ideal tissue-engineered solution for any bone graft substitute is to assist in the rapid formation of bone and facilitate fusion.

PURPOSE

The present study aims to evaluate this E-BMP-2 (Escherichia coli-derived human bone morphogenetic protein-2) in ovine posterolateral lumbar fusion (PLF) to examine the influence of dose and overall performance in a model with similar graft size and diffusive challenges to the human.

STUDY DESIGN/SETTING

In vivo large animal model study.

METHODS

An adult ovine PLF was performed in 30 animals with groups of E-BMP-2 with a beta-tricalcium phosphate (β-TCP) carrier at three different dosages, β-TCP alone, and autograft from the iliac crest. The fusions were assessed by radiography (X-ray and microcomputed tomography), mechanical testing, and hard-tissue histology with bone labels at 6, 8, and 10 weeks along with routine paraffin histology at 12 weeks.

RESULTS

Results showed increasing new bone and fusion rate with E-BMP-2 dose, whereas β-TCP alone was largely resorbed and did not achieve fusion in this model at 12 weeks. Autograft showed similar grading for the amount of bone between the transverse processes but a lower fusion rate than β-TCP/E-BMP-2 groups. Bone labels revealed new bone formation at all time points for the E-BMP2 groups, whereas the autograft group showed active bone formation at 10 weeks. Beta-tricalcium phosphate displayed reliable incorporation into the decorticated host bone, whereas limited new bone was found between the transverse processes. At the center of the fusion mass, increased E-BMP-2 dose led to increased incorporation of β-TCP by new bone.

CONCLUSIONS

These results suggest that E-BMP-2 was capable of producing posterolateral fusion in the ovine model that is equal to or superior to autologous graft in terms of fusion rate and mechanical strength. E-BMP-2 dose had considerable influence on β-TCP granule resorption.

Human polyethylene granuloma tissues inhibit bone healing in a novel xenograft animal model

During revision of a conventional polyethylene joint replacement, surgeons usually remove the source of osteolysis (polyethylene) but cannot always remove all of the polyethylene granuloma tissues. We developed a human/rat xenograft model to investigate the effects of polyethylene granuloma tissues on bone healing. Human osteoarthritic and periprosthetic tissues collected during primary and revision hip arthroplasty surgeries were transplanted into the distal femora of athymic nude rats. After 3 weeks in vivo, there was a significant difference in the bone volume fraction (Vf ) between empty, primary, and revision defects (p = 0.02), with a lower Vf in defects with revision granuloma tissues compared to defects with primary osteoarthritic tissues. Polyethylene granuloma tissues in trabecular bone defects inhibited bone healing. Therefore, debridement around a metal-on-polyethylene hip replacement may shorten the time it takes to achieve secondary stability around a revision hip replacement.

Poor histological healing of a femoral fracture following 12 months of oestrogen deficiency in rats

SUMMARY

Fractures in post-menopausal osteoporosis cause significant morbidity; however, animal models for post-menopausal fracture healing lack the effect of ageing. Therefore, we developed a model using aged animals with chronic oestrogen deficiency, which demonstrates inferior fracture repair (decreased healing histologically, bone mineral density and content and strength). This novel model may help develop molecular strategies for osteoporotic fracture repair.

INTRODUCTION

The femur is susceptible to damage by both systemic conditions such as osteoporosis and locally by traumatic injury. The capacity for fracture repair decreases with age, while the risk of fracture increases. As studies of osteoporotic fracture healing in rats traditionally use a period of 3 months or less of oestrogen deficiency prior to fracturing, we aimed to establish a osteoporosis model in rats with chronic oestrogen deficiency by 12 months to better mimic human female osteoporosis.

METHODS

Seventy female Sprague-Dawley rats (10 weeks old) were ovariectomised or sham operated and housed for 12 months. The right femur was fractured by way of an open osteotomy and fixed with an intramedullary Kirschner wire. Animals were sacrificed at 1, 3 and 6 weeks for radiography, dual-energy X-ray absorptiometry, tensile testing and histology.

RESULTS

Bone mineral density and bone mineral content were lower by 60 and 63 %, respectively, (p < 0.05) in the bilaterally ovariectomized (OVX) groups than those in the sham groups at 6 weeks in the right fractured femurs. Maximum breaking force of the OVX group was lower than that of the sham group, with the greatest difference seen at 6 weeks following osteotomy. Histologically, the OVX groups demonstrated a delay in cellular differentiation within the fracture callus and the presence of bone resorption. The sham animals had a superior histological healing pattern with an Allen score of 4 at 6 weeks compared to a score of 1 for the OVX groups (p < 0.01).

CONCLUSIONS

Long-term ovariectomy has a deleterious effect on fracture healing in a rodent model.

The effect of sterilization methods on the osteoconductivity of allograft bone in a critical-sized bilateral tibial defect model in rabbits

Clinically, allogeneic bone graft is used extensively because it avoids the donor site morbidity associated with autograft. However, there are concerns over the optimal sterilization method to eliminate immunological risks whilst maintaining the biological efficacy of the graft. This study compared the effect of Supercritical fluid (SCF) treatment and gamma irradiation at 25 kGy on the osteoconductivity of allograft bone in a bilateral critical sized defect rabbit model. Osteoconductivity was evaluated at 2 and 4 weeks using X-ray, CT, histology (qualitative and quantitative) and immunohistochemistry (Alkaline Phosphatase and Cathepsin-K). Both grafts were well tolerated and osteoconductive. At 2 weeks, there was decreased bone volume and density in the gamma irradiated graft compared to the SCF treated graft, corresponding with a greater inflammatory response histologically and increased Cathepsin-K expression. Catabolic activity predominated at 4 weeks, with both grafts undergoing significant resorption and remodeling inside the defect. Alkaline Phosphatase expression was greater in the SCF group at both time points indicative of a more anabolic response. Allograft bone sterilized with either gamma irradiation or SCF treatment was osteoconductive and capable of healing a critical sized tibial defect in a rabbit. Gamma irradiated allografts elicited an acute inflammatory reaction when implanted which may increase the amount of graft resorption compared to the SCF treated bone.

The effects of low-intensity pulsed ultrasound on tendon-bone healing in a transosseous-equivalent sheep rotator cuff model

PURPOSE

The purpose of this study was to examine the effects Low-intensity Pulsed Ultrasound has on initial tendon-bone healing in a clinically relevant extra-articular transosseous-equivalent ovine rotator cuff model.

METHODS

Eight skeletally mature wethers, randomly allocated to either control group (n = 4) or treatment group (n = 4), underwent rotator cuff surgery following injury to the infraspinatus tendon. All animals were killed 28 days post surgery to allow examination of early effects of Low-intensity Pulsed Ultrasound treatment.

RESULTS

General improvement in histological appearance of tendon-bone integration was noted in the treatment group. Newly formed woven bone with increased osteoblast activity along the bone surface was evident. A continuum was observed between the tendon and bone in an interdigitated fashion with Sharpey's fibres noted in the treatment group. Low-intensity Pulsed Ultrasound treatment also increased bone mineral density at the tendon-bone interface (p < 0.01), while immunohistochemistry results revealed an increase in the protein expression patterns of VEGF (p = 0.038), RUNX2 (p = 0.02) and Smad4 (p = 0.05).

CONCLUSIONS

The results of this study indicate that Low-intensity Pulsed Ultrasound may aid in the initial phase of tendon-bone healing process in patients who have undergone rotator cuff repair. This treatment may also be beneficial following other types of reconstructive surgeries involving the tendon-bone interface.

Effects of demineralized bone matrix on tendon-bone healing in an intra-articular rodent model

BACKGROUND

Techniques to improve and accelerate tendon-bone healing could be advantageous in anterior cruciate ligament (ACL) reconstruction. Effects of demineralized bone matrix (DBM) on intra-articular tendon-bone healing have not been examined.

HYPOTHESIS

Demineralized bone matrix has the potential to convey osteoinductive growth proteins to the site of healing at the tendon-bone interface. We hypothesized that the presence of DBM will result in more bone formation and hasten tendon-bone healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifty-six female athymic rnu/rnu (nude) rats were used. Rats were randomly allocated into 2 groups (control or treatment). The control group underwent an ACL reconstruction, while the treatment group had human DBM implanted in the tendon graft and bone tunnel before reconstruction. Rats were sacrificed at 2 (n = 8), 4 (n = 24), and 6 (n = 24) weeks for histological, and immunohistochemical (t = 2, 4, and 6 weeks), and biomechanical testing and micro-computed tomography (t = 4 and 6 weeks) end points.

RESULTS

Our findings suggest that in the presence of DBM, tendon-bone healing is augmented by increased woven bone formation and enhanced bone remodeling as indicated by histology and micro-computed tomography. This ultimately resulted in a statistically significant increase in peak load to failure of the tendon-bone interface at 4 weeks (DBM group: 5.96 ± 1.36 N; control group: 2.86 ± 0.7 N) and 6 weeks (DBM group: 9.13 ± 0.97 N; control group: 5.81 ± 1.1 N).

CONCLUSION

Demineralized bone matrix at the tendon-bone interface promotes healing between the tendon and bone in a rodent ACL model.

CLINICAL RELEVANCE

Introduction of osteoinductive DBM at the tendon-bone interface during ACL reconstructive surgery may improve short-term outcomes.

Effects of Gaps Induced Into the ACL Tendon Graft on Tendon-Bone Healing in a Rodent ACL Reconstruction Model

Graft necrosis following ACL reconstruction is often associated with the use of autologous grafts. Host cells rather than graft cells contribute to the repair of the tendon-bone interface and the remodeling of the autologous graft. The native tendon-bone interface is not recreated and the biomechanical properties are not restored back to native values. We examined the effects of introducing gaps within the tendon graft prior to ACL reconstruction in a rodent model. We hypothesised that gaps will make physical way for host cells to infiltrate and repopulate the graft and thus enhance healing. Animals were sacrificed at seven, fourteen, and twenty-eight days for biomechanical testing and histology. Our findings indicate that graft necrosis, usually observed in the initial two weeks of the healing process, is averted. Histological observations showed that tendon-bone healing stages were hastened however this didn't translate into improved biomechanical properties.

Relationship between age, skeletal site, and time post-ovariectomy on bone mineral and trabecular microarchitecture in rats

The ovariectomized (OVX) rat is widely used in osteoporosis research, but no standard model exists. The individual effects of rat age, skeletal site, and time post-ovariectomy (post-OVX) on bone have been examined. However, the relationship between them is not yet fully explored. This study examined how various combinations of rat age, skeletal site, and time post-OVX affect bone mineral and microarchitecture. The rats used were 12 (n = 28), 24 (n = 28), and 44 (n = 31) weeks old. In each age group, approximately half underwent OVX and other half underwent Sham surgeries. Bone mineral (content and density) and trabecular morphology was assessed at 2, 5, 10, 15, 20, 25, and 30 weeks post-surgery. Sites examined included the proximal tibia, spine, distal femur, and proximal femur. Overall, the proximal tibia showed the earliest and greatest differences between OVX and Sham groups. The 24-week-old group showed the best osteoporotic response. The 12-week-old group showed growth effects, whilst the 44-week-old group showed aging effects. The response of certain sites to OVX was also found to depend on the rat age used. These findings may aid in explaining discrepancies reported in the literature as well as synergistic combinations that may signify advanced conditions. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:189-196, 2011.

Application of highly silicon-doped marker layers in the investigation of unintentional doping in GaN on sapphire

To provide a route to the assessment of the impact of inclined facets on unintentional n-type doping during the growth of c-plane GaN on sapphire, thin (100 nm), highly Si-doped (at 10¹⁹ cm⁻³) marker layers have been incorporated into a GaN epitaxial layer grown by a method involving a transition from initial three-dimensional island growth to later, two-dimensional, planar growth. Imaging of the completed epitaxial layer in cross-section by scanning capacitance microscopy reveals the shapes of the islands, which were present during the early stages of growth and the relationship between the facets present and the incorporation of unintentional dopants. The results show that unintentional dopants are mostly incorporated on facets inclined to the [0001] direction, and suggest that gaseous impurities present in the MOVPE reactor are one source of dopant species.

Application of resorbable poly(lactide-co-glycolide) with entangled hyaluronic acid as an autograft extender for posterolateral intertransverse lumbar fusion in rabbits

Facilitating fusion between bony segments in a reliable and reproducible manner using a synthetic bone graft material has a number of benefits for the surgeon as well as the patient. Although autograft remains the gold standard, associated comorbidities continue to drive the development of new biomaterials for use in spinal fusion. The ability of autograft alone and autograft combined with a radiolucent biomaterial composed of resorbable osteoconductive poly(lactide-co-glycolide) with entangled hyaluronic acid to facilitate fusion was examined in a single-level noninstrumented posterolateral intertransverse lumbar fusion model in New Zealand White rabbits. Progressive bone formation was demonstrated radiographically for the extender group (synthetic biomaterial plus autograft) between 3 and 6 months. Computed tomography revealed a new cortical shell in the fusion mass at 3 and 6 months for both study groups. Tensile testing at 6 months demonstrated that the quality of bone formed between the intertransverse space was equivalent for both study groups. Histologic evaluation of the fusion mass revealed new bone on and adjacent to the transverse processes with the synthetic biomaterial group that extended laterally, supporting the osteoconductive nature of the material. Histological evidence of endochondral bone growth in the intertransverse space was observed for the autograft plus synthetic biomaterial group. Bone remodeling, new marrow spaces, and peripheral cortices were observed for each study group at 3 months that matured by 6 months. These findings support the use of a radiolucent biosynthetic material comprising poly(lactide-co-glycolide) with integrated hyaluronic acid as an autograft extender for lumbar intertransverse fusion.

Imaging dislocations in gallium nitride across broad areas using atomic force microscopy

We have employed an atomic force microscope with a high sampling rate to image GaN samples grown using an epitaxial layer overgrowth technique and treated with silane and ammonia to enlarge the surface pits associated with threading dislocations (TDs). This allows TDs to be identified in high pixel density images tens of microns in size providing detailed information about the spatial distribution of the TDs. An automated software tool has been developed, which identifies the coordinates of the TDs in the image. Additionally, we have imaged the same sample using Kelvin probe force microscopy, again at high pixel density, providing data about the local changes in surface potential associated with hundreds of dislocations.

Analysis of alloantisera against bovine lymphocytes. Joint report of the 1st International Bovine Lymphocyte Antigen (BoLA) workshop

The results and agreements of the 1 international BoLA workshop, held in Edinburgh, Scotland in August 1978, are reported. Most of these concern the results from a comparison test of 249 alloantisera to bovine lymphocytes, the antisera being contributed by 9 laboratories. These sera were compared directly in Edinburgh on a panel of lymphocytes from 130 cattle of 21 breeds. In the microlymphocytotoxicity test used 75% of the sera reacted. Sixty eight of these sera were grouped into clusters according to their reaction patterns against the lymphocyte panel. Eleven of these clusters were clearly defined and were given workshop BoLA designations. In addition 22 sera were assigned to subgroups of the agreed clusters. There was no evidence that the method of production of the sera had any effect on their specificity. Although genetic data was not available, the phenotypes of the test panel of lymphocytes are consistent with the clusters detecting antigens controlled by multiple alleles at a single autosomal locus. It was agreed to name the genetic region where this putative locus is located BoLA (bovine lymphocyte antigen).

Production of alloantisera against class II bovine lymphocyte antigens (BoLA) by cross-immunization between class I matched cattle

This paper describes the production of alloantisera directed against bovine major histocompatibility complex (MHC) (BoLA) class II antigens in animals whose MHC phenotypes had been defined by one dimensional isoelectric focusing. Animals of closely matched BoLA class I types were selected by serology and subsequently typed for class I and class II by 1D-IEF of immunoprecipitated antigens. Those with similar class I type by both methods, but differing at the class II locus, were chosen for reciprocal immunization. Cross-immunization was by two skin implantations 6 weeks apart. The resulting antisera showed low titre after the first immunization and elevated titre 3 weeks after the second immunization. The sera reacted strongly with cells expressing specific BoLA class II antigens. The pattern of reactivity correlated well with IEF class II typing on a panel of animals representing all of the class II IEF types present in the Friesian population.