Introduction

Canonical Wnt inhibitor Sclerostin (SOST) may be a key mechanotransduction regulator.

Despite its clinical significance, metaphyseal fracture healing has received little attention in research and experimental models have been limited. In particular it is not known to what extent the mechanical environment plays a role in metaphyseal fracture healing. Recently, a new murine internal fixation plate has been developed to stabilise fractures in the distal femur under highly standardised conditions. Goal of the current study was to modify this design, in order to be able to evaluate the influence of the fixator bending stiffness on metaphyseal fracture healing in mice. Adapting the existing single body design, resulting in low flexibility fixation, two new plates were developed with a decreased bending stiffness of approximately 65% and 45% of the original implant (100%). Pilot experiments were performed on 54 animals, whereas the mice were sacrificed and fracture healing assessed radiologically and biomechanically after 14 and 28 days. MicroCT evaluation confirmed that the osteotomy was created in the trabecular, metaphyseal bone of the distal mouse femora. All bones showed progressive fracture healing over time, with decreased implant stiffness leading to increased periosteal callus formation. These implants represent an important new research tool to study molecular and genetic aspects of metaphyseal fracture healing in mice under standardized mechanical conditions, in order to improve clinical treatment in challenging situations, such as in osteoporotic bone

Introduction. Bone tissue engineering approaches are an emerging strategy to treat bone defects, and commonly involve the delivery of osteogenic cells and/or drugs via a porous scaffold. We have been exploring an alternative injectable approach for drug delivery that would obviate the need for invasive surgery. Hypothesis. Sucrose Acetate Isobutyrate (SAIB) is a sucrose-based ester that is a highly viscous semi-solid. Diluting SAIB with 10–20% ethanol markedly reduces its viscosity, with ethanol diffusing rapidly after in vivo injection. This phase transitioning property makes SAIB an ideal candidate for bone tissue engineering. Materials and methods. The capacity of SAIB to act as a delivery system for recombinant human BMP-2 (rhBMP-2) was tested in a mouse ectopic bone formation model. In this model SAIB was used to deliver 0 to 10μg rhBMP-2. Next, SAIB was compared with porous collagen scaffold used clinically to delivery rhBMP-2 in a head-to-head trial. Commercial SAIB and SAIB produced in-house were also compared. Bone volumes were quantified by μCT. Discussion. Bone was found to form with as little as 2μg rhBMP-2 when delivered with SAIB. Injected SAIB also showed minimal inflammatory response and rapid breakdown, with bone formation occurring between one and two weeks. Conclusion. SAIB was found to be an effective delivery system for rhBMP-2 with translational utility. Future work will be required to examine the upscaling of this delivery system

Exercise deters systemic diseases such as osteoporosis, sarcopenia, diabetes and obesity. Brief daily periods of low intensity vibration (LIV; <0.4g) is anabolic to bone and muscle, an adaptive response achieved in part by biasing mesenchymal stem cell (MSC) fate selection towards forming higher order connective tissues. In the clinic, LIV has protected the musculoskeletal system even under severe challenges such as Crohn Disease, Cerebral Palsy, and end-stage renal disease. Low magnitude mechanical signals also suppress adipogenesis in the mouse, with reductions in subcutaneous and visceral fat. The starkly distinct response of these tissues (augment bone & muscle; suppress fat) suggests that LIV influences the differentiation pathway of MSCs. Extending this diet induced obesity model to 7 months increased total adiposity, accelerated age-related loss of trabecular bone and severely reduced B & T-cell number in the marrow and blood, shifting hematopoietic stem cells (HSC) towards the myeloid lineage. LIV introduced at 4 months rescued bone and B-cells to those levels measured in regular diet controls. These data emphasise why inactivity can promote osteoporosis, diabetes and obesity, and why a sedentary individual is predisposed to disease sequelae. Protection of MSC and HSC populations by mechanical signals may represent a unique strategy by which adiposity can be suppressed, the immune system protected, and a musculoskeletal system enhanced

Introduction. Intraosseous transcutaneous amputation prostheses (ITAP) provide an alternative means of attaching artificial limbs for amputees. Conventional stump-socket devices are associated with soft tissue complications including; pressure sores and tissue necrosis. ITAP resolves these problems by attaching the exo-prosthesis transcutaneously to the skeleton. The aim of this study is to increase the attachment of dermal fibroblasts to titanium alloy in vitro. Fibronectin (Fn) and laminin 332 (Ln) enhance early cell growth and adhesion. We hypothesize that silanized dual coatings of fibronectin and laminin (SiFnLn) will be more durable when compared with adsorbed dual coating (AdFnLn), and will enhance early fibroblast growth and adhesion compared to single coatings. Methods. The kinetics of dual single and dual protein coating attachment onto titanium alloy was quantified on silanized 10mm diameter discs using radiolabelled Fn (125I-Fn) and Ln (125I-Ln). Sixty discs were polished, sterilized and silanized. Coating durability was assessed when soaked in fetal calf serum (FCS) for 0, 1, 24, 48 and 72hrs. Data was compared to un-silanized Ti discs with the same coatings. Five thousand human dermal fibroblasts were seeded on discs (n = 6) of Ti polished alone (Pol), Ti with adsorbed fibronectin (AdFn), Ti with adsorbed laminin (AdLn), Ti adsorbed dual coating (AdFnLn), Ti silanized (Si), Ti silanized with fibronectin (SiFn), Ti silanized with laminin (SiLn), Ti silanized with a dual coating (SiFnLn) for 24hrs. In order to measure cell adhesion fibroblasts were fixed, vinculin stained using mouse vinculin antibody and alexa fluor. Axiovision Image Analysis software was used to measure cell area, vinculin focal adhesion markers per cell and per unit cell area. Data was analysed in SPSS and significance was assumed at the 0.05 level. Results. Silanized dual coatings bonded to Ti alloy in significantly larger quantities compared with adsorbed coatings at all time points (all p values < 0.05). Fibroblasts cultured on dual coatings were significantly larger, produced more vinculin markers per cell, and per unit cell area compared with single coatings. Cells on SiFnLn were larger with more numerous vinculin markers per cell, and per unit cell area compared with AdFnLn (p<0.05). Conclusion. This study has demonstrated that covalently bonding both fibronectin and laminin to Ti alloy provides a durable, dual coating that enhances early fibroblast growth and attachment compared with either protein coating alone in vitro. Our study showed that there is non-competitive binding of laminin on Ti surfaces in the presence of fibronectin. Dual coatings may be applied to the skin-penetrating region of transcutaneous devices to improve the skin seal and this may have positive implications for the development of ITAP

Introduction. Following amputation, residual stumps used to attach the external prostheses can be associated with sores, infection and skin necrosis. These problems could be overcome by off loading the soft tissues. Intraosseous transcutaneous amputation prostheses (ITAP) attach external implants directly to residual bone reducing these complications. However, a tight seal at the skin implant interface is crucial in preventing epithelial down-growth and infection. Fibronectin (Fn) and laminin 332 (Ln), enhance early cell growth and adhesion of keratinocytes. Silanization to titanium alloy (Ti) allows these proteins to bond to the metal directly. We hypothesize that silanized dual coatings of fibronectin and laminin (SiFnLn) will be more durable than absorbed proteins and that keratinocyte adhesion will be increased compared with Ti controls and single silanized proteins. Methods. 10 mm diameter Ti alloy discs were polished, sterilized and silanized. The kinetics of silanized single and dual protein coating attachment onto titanium alloy was quantified using radio-labelled Fn(125I-Fn) and Ln(125I-Ln). Coating durability was assessed when soaked in fetal calf serum (FCS) for 0, 1, 24, 48, 72hrs. Data was compared to un-silanized Ti discs with the same amount of adsorbed proteins. In order to study cell attachment 20 × 103 keratinocytes were seeded on the discs (n = 6): silanized (Si), silanized fibronectin (SiFn), silanized laminin (SiLn), silanized dual coating (SiFnLn) for 1, 4 and 24hrs. Adhesion of cells was assessed using mouse vinculin antibody for 2hrs and alexafluor for 1hr which stains focal adhesions responsible for attaching cells to surfaces. Axiovision Image Analysis software was used to measure cell area, vinculin markers per cell unit and per unit cell area on 15 cells per disc. Data was analysed in SPSS and significance was assumed at the 0.05 level. Results. Silanized dual coatings bonded to Ti alloy in significantly larger quantities compared with adsorbed coatings (all p values < 0.05). When proteins were combined on silanized discs the same amount of each protein was attached as when used as a single coating (i.e. non competitive binding). Keratinocytes cultured on silanized dual coatings were significantly larger, produced more vinculin markers per unit cell and per cell area compared with single coatings at all time points. Conclusion. This study has demonstrated that silanized using dual proteins on Ti alloy enhances early keratinocyte growth and attachment in vitro. It also shows that there is non-competitive binding of laminin to Ti alloys in presence of fibronectin. This may lead to improved epidermal attachment to ITAP creating a tight seal at the implant interface, which will prevent migration of the epithelium and subsequent infection in vivo

Objectives

Nonunion is one of the most troublesome complications to treat in orthopaedics. Former authors believed that atrophic nonunion occurred as a result of lack of mesenchymal stem cells (MSCs). We evaluated the number and viability of MSCs in site of atrophic nonunion compared with those in iliac crest.

Objectives

The biomembrane (induced membrane) formed around polymethylmethacrylate (PMMA) spacers has value in clinical applications for bone defect reconstruction. Few studies have evaluated its cellular, molecular or stem cell features. Our objective was to characterise induced membrane morphology, molecular features and osteogenic stem cell characteristics.

We hypothesised that cells obtained via a Reamer–Irrigator–Aspirator (RIA) system retain substantial osteogenic potential and are at least equivalent to graft harvested from the iliac crest. Graft was harvested using the RIA in 25 patients (mean age 37.6 years (18 to 68)) and from the iliac crest in 21 patients (mean age 44.6 years (24 to 78)), after which ≥ 1 g of bony particulate graft material was processed from each. Initial cell viability was assessed using Trypan blue exclusion, and initial fluorescence-activated cell sorting (FACS) analysis for cell lineage was performed. After culturing the cells, repeat FACS analysis for cell lineage was performed and enzyme-linked immunosorbent assay (ELISA) for osteocalcin, and Alizarin red staining to determine osteogenic potential. Cells obtained via RIA or from the iliac crest were viable and matured into mesenchymal stem cells, as shown by staining for the specific mesenchymal antigens CD90 and CD105. For samples from both RIA and the iliac crest there was a statistically significant increase in bone production (both p < 0.001), as demonstrated by osteocalcin production after induction.

Medullary autograft cells harvested using RIA are viable and osteogenic. Cell viability and osteogenic potential were similar between bone grafts obtained from both the RIA system and the iliac crest.

Cite this article: Bone Joint J 2013;95-B:1269–74.

Heterotopic ossification (HO) is perhaps the single most significant obstacle to independence, functional mobility, and return to duty for combat-injured veterans of Operation Enduring Freedom and Operation Iraqi Freedom. Recent research into the cause(s) of HO has been driven by a markedly higher prevalence seen in these wounded warriors than encountered in previous wars or following civilian trauma. To that end, research in both civilian and military laboratories continues to shed light onto the complex mechanisms behind HO formation, including systemic and wound specific factors, cell lineage, and neurogenic inflammation. Of particular interest, non-invasive in vivo testing using Raman spectroscopy may become a feasible modality for early detection, and a wound-specific model designed to detect the early gene transcript signatures associated with HO is being tested. Through a combined effort, the goals of early detection, risk stratification, and development of novel systemic and local prophylaxis may soon be attainable.