The effect of head injury on systemic physiology, including bone healing is still a topic of vivid discussion. We aimed to investigate whether in patients with long bone fractures the presence of head injury is associated with excessive callus formation. Data on patients with head injury and femoral diaphyseal fracture admitted to our trauma unit between 1997- 2002 were collected and analysed. Patients with factors that could influence bone healing such as smoking, NSAIDs and hormonal disorders were excluded. The severity of head injury was quantified using GCS, AIS and CT scan reports. Patients matched for age, sex and ISS with femoral shaft fractures and no head injury formed the control group of the study. All the fractures were stabilised with reamed femoral nail. The quantification of fracture healing response was estimated by taking the radiological ratio of the largest diameter of callus formed into two planes and the adjacent normal diameter of femoral canal. The minimum follow-up of the patients was 12 months. In total 42 patients were studied, 17 with head injury and femoral fracture and 25 with an isolated femoral fracture, (control group). Both groups were comparable in terms of age, sex, ISS. The difference between the mean callus to diaphyseal ratio was statistically significant for both the AP and Lateral projections (AP – mean difference 0.462, 95% CI 0.312 to 0.602, p<0.0001, LAT – mean difference 0.289, 95% CI 0.142 to 0.436, p<0.001) with the head injured patients having more florid callus compared to the control group. This study supports the view that head injury leads to exuberant callus formation in patients with long bone fractures. The mechanisms of this response could be both central and local. Research is ongoing to elucidate the pathways involved in this biological phenomenon

Patients with bone and muscle weakness from disuse have higher risk of fracture and worse post-injury mortality rates. The goal of this current study was to better inform post-fracture rehabilitation strategies by investigating if physical remobilization following disuse by hindlimb unloading improves osteochondral callus formation compared to continued disuse by hindlimb suspension (HLS). We hypothesized that continued HLS would impair callus bone and cartilage formation and that physical rehabilitation after HLS would increase callus properties. All animal procedures were approved by the VCU IACUC. Skeletally mature, male and female C57BL/6J mice (18 weeks) underwent HLS for 3 weeks. Mice then had their right femur fractured by open surgical dissection (stabilized with 24-gauge pin). Mice were then either randomly assigned to continued HLS or allow normal physical weight-bearing remobilization (HLS + R). Mice allowed normal cage activity throughout the experiment served as controls (GC). All mice were sacrificed 14-days following fracture with 4-8 mice (male and female) per treatment. Data analyzed by respective ANOVA with Tukey post-hoc (*p< 0.05; # p < 0.10). Male and female mice showed conserved and significant decreases in hindlimb callus bone formation from continued HLS versus HLS + R. Combining treatment groups regardless of mouse sex, histological analyses using staining on these same calluses demonstrated that HLS resulted in trends toward decreased cartilage cross-sectional area and increased osteoclast density in woven bone versus physically rehabilitated mice. In support of our hypothesis, physical remobilization increases callus bone formation following fracture compared to continued disuse potentially due to increased endochondral ossification and decreased bone resorption. In all, partial weight-bearing exercise immediately following fracture may improve callus healing compared to delayed rehabilitation regimens that are frequently used

Introduction: Angiogenesis is essential during bone formation. Many studies have looked at the developing vascular network during normal and abnormal bone growth, using histological, immunohistological and contrast-radiological techniques; however all require sacrifice of animals to obtain tissue samples for examination and consequently chronological investigation of angiogenesis is not possible. We have endeavoured to produce an animal model, whereby quantitative assessment of blood flow, and callus formation across a fracture gap, can be repeatedly assessed. Methods: The model is an adaptation of a 4-pin externally fixated murine femoral fracture previously developed in this department. Three extra conduits have been drilled onto the fixator cross-bar, such that it now links with an x-ray jig and implantable optical cable. The x-ray jig permits repeated lateral x-rays whereas the optical cable which is implanted adjacent to the fracture gap and connected to a laser, measures blood flow using the principle of the Doppler shift of light. Ten mice underwent surgery. Doppler readings and x-rays were taken on the day of surgery and subsequently at days 1, 2, 4, 8, 12, 16, 24 and 32. Results: Fracture gap pixel density was seen to rise steadily and plateau at day 24, with significant statistical differences between the day of surgery and early time points, and then again between these early time-points (days 2, 4 and 8) and the late time-point day 24. Blood flow was noted to fall following the day of surgery and then slowly increase, with a rapid rise in flow at day 8 until day 16, when levels began to fall again to resting levels. Conclusion: The data correlates with previous histo-morphological work performed in this department and also with early results from immunohistochemical studies. The above graph for blood flow conforms to that expected in a murine model of fracture healing, with a short initial drop in flow followed by a large rise as angiogenesis follows chondrocyte hypertrophy at the end of the first week, leading to callus formation. This in vivo model may be used to assess the effects on angiogenesis and callus formation of osteogenic compounds and investigate possible antiangiogenic mechanisms of action of medications such as NSAIDs that are known to be detrimental to fracture repair

Our purpose is to use radiographs to compare callus formation with two types of intramedullary nailing for femoral shaft fractures: reamed interlocking (IL) and Ender nails. Femoral shaft type A fractures according to AO classification were studied. From 1991 to 1995, 27 patients with 27 fractures were treated with reamed IL nailing and 79 patients with 81 fractures were treated with Ender nailing. IL group included with an average of 22 (range, 16–28) years, and the Ender group included with an average of 28 (range, 15–72) years. Patients had been followed for an average of 1.8 (range, 1–2.8) years after surgery. In all cases of IL group, the femoral canal was reamed. For type A3 fractures, an interlocking screw was inserted only at the distal site. For type A1 and A2 fractures, both proximal and distal locking screws were placed. In the Ender nailing cases, 3 to 5 Ender nails were inserted from medial or lateral side of the supracondylar or intertrochanteric regions of the femur as was dictated by the fracture site. All of these fractures were reduced by a closed technique. The measurement of postoperative callus area was calculated from the maximum cross-sectional area on the anteroposterior and lateral radiographs. Fracture healing was successful in all patients. On the radiograph, the callus for the IL group appeared at a mean of 3.9 weeks after surgery, and at a mean of 2.8 weeks for the Ender group. In the IL and Ender groups, fracture healing was noted at a mean of 3.4 and 2.0 months, respectively. The mean area of callus formation in the IL and Ender nailing was 439.5mm2 and 699.4 mm2, respectively. To compare the two groups by using a Mann-Whitney U test, the significant differences were seen in the callus appearance period (p< 0.05) and in the callus area (p< 0.01). Dynamization at the fracture site is reported to increase external callus formation. Our results indicate that the elasticity of the fixation obtained with Ender nailing promotes callus formation

The aim of this study was to examine whether the assessment BsALP as a biochemical parameter in the early posttraumatic phase may indicate the course of fracture healing. The methods used for monitoring the bone healing process have been based on the patient’s subjective evaluation and radiographic findings. The activity of bone-specific alkaline phosphatase was measured in the sera of 41 patients who had sustained fractures of long bones. All the patients had been treated surgically. The activity of BsALP was assessed every seven days over a four-week period. The same patients were subject to radiology follow-ups for several months. Our research showed that the increase of alkaline phosphatase correlated with an increase of BsALP levels. The volume of callus correlated with a decrease, no change or an increase in the level of ALP and BsALP in the same way. It can be concluded that the monitoring of changes in the biochemical parameters of alkaline phosphatase and bone-specific alkaline phosphatase allows the early detection of the fracture healing dynamics.

Introduction: Patients who are prescribed bisphosphonates are still at risk to endure a fracture from weak and brittle bones. The question is what pharmacologic strategy should be taken to accelerate fracture healing when the patient is currently taking a bisphosphonate. Ibandronate, was tested in an osteoporotic rat model to determine how it modified the callus healing and resistance to torsion after a transverse fracture was produced in a femur.

Materials and Methods: 36 female rats were divided into 3 groups; ovariectomized (OVX) placebo control, non-OVX control and Ibandronate. Prior to the osteotomy, the Ibandronate treatment group was injected with the drug over 21 days healing. Each sample was scanned by the SCANCO uCT 80 to measure volume of the callus and quality of the trabeculae in the proximal femur. Instron testing recorded the modulus of rigidity and torque until failure. Yield point and toughness were also calculated.

Results: uCT images taken over the fracture gap showed that the Ibandronate rats had greater bone volume fraction of woven callus by ANOVA compared to control groups (p< 0.05). Significant in total callus volume for Ibandronate, were shown to be 32% larger than the non-OVX control group and 45% larger than the placebo group. Ibandronate also increased BMD of woven bone in the callus by 14%. Ibandronate showed the highest polar moment of inertia as well.

The torsion testing in Ibandronate had 51% greater toughness than placebo and 69% greater than the non-OVX group. Ibandronate increased trabecular number significantly over the placebo and was not significantly different from the non-OVX group. Trabecular separation was less in Ibandronate compared to the placebo group. Volume in the trabecular neck increased by 35% for the Ibandronate over the placebo.

Discussion: Ibandronate had an anabolic effect to produce more callus tissue at the fracture site, most likely by suppressing osteoclast remodelling activity. A large callus with more bone would increase fracture stability and reduce risk of non union. This is supported by a larger polar moment of inertia. Ibandronate had greater resistance to torsion, which could indicate better healing. However increased rigidity would not entirely benefit the healing unless the bone could handle load plastically. The toughness results showed that Ibandronate can absorb more energy than the control groups before refracturing. Continued treatment with this drug after a fracture could form a larger callus with greater mechanical toughness while also treating the disease of osteoporosis in other fracture risk sites of the body.

Introduction and Objective. It is widely accepted that interfragmentary strain stimulus promotes callus formation during secondary bone healing. However, the impact of the temporal variation of mechanical stimulation on fracture healing is still not well understood. Moreover, the minimum strain value that initiates callus formation is unknown. The goal of this study was to develop an active fixation system that allows for in vivo testing of varying temporal distribution of mechanical stimulation and that enables detection of the strain limit that initiates callus formation. Materials and Methods. We employed a previously established wedge defect model at the sheep tibia. The model incorporates two partial osteotomies directed perpendicularly to each other, thus creating a bone fragment in the shape of a wedge. The defect was instrumented with an active fixator that tilts the wedge around its apex to create a gradient of interfragmentary strain along the cutting line. The active fixator was equipped with a force and displacement sensors to measure the stiffness of the repair tissue during the course of healing. We developed a controller that enabled programming of different stimulation protocols and their autonomous execution during the in vivo experiment. The system was implanted in two sheep for a period of five weeks. The device was configured to execute immediate stimulation for one animal (stimulation from Day 1), and delayed stimulation for the other (stimulation from Day 22). The daily stimulation protocol consisted of 1’000 loading events evenly distributed over 12 hours from 9:00 am to 9:00 pm. The healing progression was monitored by the in vivo stiffness measurements provided by the fixator and by weekly radiographs. The impact of the local strain magnitude on bone formation was qualitatively evaluated on a post-mortem high-resolution CT scan of the animal with immediate stimulation. Results. The animals tolerated the fixator system well. Both devices operated seamlessly throughout the entire experiment. Callus formation was initiated earlier for the immediately stimulated animal which was also confirmed by a faster stiffness increase. In this pilot feasibility experiment, the initiation of callus formation was observed between 0% and 4% local interfragmentary strain. Conclusions. We developed an autonomous stimulation system for large animal research that enables systematic investigation of fracture healing processes. The in vivo pilot study demonstrated the feasibility of the system and delivered first interesting insides on temporal stimulation impact and callus induction strain limit. These observations, however, require further validation

The primary aim was to assess the reliability of ultrasound in the assessment of humeral shaft fracture healing. The secondary aim was to estimate the accuracy of ultrasound assessment in predicting humeral shaft nonunion. Twelve patients (mean age 54yrs [20–81], 58% [n=7/12] female) with a non-operatively managed humeral diaphyseal fracture were prospectively recruited and underwent ultrasound scanning at six and 12wks post-injury. Scans were reviewed by seven blinded observers to evaluate the presence of sonographic callus. Intra- and inter-observer reliability were determined using the weighted kappa and intraclass correlation coefficient (ICC). Accuracy of ultrasound assessment in nonunion prediction was estimated by comparing scans for patients that united (n=10/12) with those that developed a nonunion (n=2/12). At both six and 12wks, sonographic callus was present in 11 patients (10 united, one developed a nonunion) and sonographic bridging callus (SBC) was present in seven patients (all united). Ultrasound assessment demonstrated substantial intra- (6wk kappa 0.75, 95% CI 0.47-1.03; 12wk kappa 0.75, 95% CI 0.46-1.04) and inter-observer reliability (6wk ICC 0.60, 95% CI 0.38-0.83; 12wk ICC 0.76, 95% CI 0.58-0.91). Absence of sonographic callus demonstrated a sensitivity of 50%, specificity 100%, positive predictive value (PPV) 100% and negative predictive value (NPV) 91% in nonunion prediction (accuracy 92%). Absence of SBC demonstrated a sensitivity of 100%, specificity 70%, PPV 40% and NPV 100% (accuracy 75%). Of three patients at risk of nonunion based on reduced radiographic callus formation (Radiographic Union Score for HUmeral fractures <8), one had SBC on 6wk ultrasound (and united) and the other two had non-bridging or absent sonographic callus (both developed a nonunion). Ultrasound assessment of humeral shaft fracture healing was reliable and predictive of nonunion, and may be a useful tool in defining the risk of nonunion among patients with reduced radiographic callus formation

Aims. Impaired fracture repair in patients with type 2 diabetes mellitus (T2DM) is not fully understood. In this study, we aimed to characterize the local changes in gene expression (GE) associated with diabetic fracture. We used an unbiased approach to compare GE in the fracture callus of Zucker diabetic fatty (ZDF) rats relative to wild-type (WT) littermates at three weeks following femoral osteotomy. Methods. Zucker rats, WT and homozygous for leptin receptor mutation (ZDF), were fed a moderately high-fat diet to induce T2DM only in the ZDF animals. At ten weeks of age, open femoral fractures were simulated using a unilateral osteotomy stabilized with an external fixator. At three weeks post-surgery, the fractured femur from each animal was retrieved for analysis. Callus formation and the extent of healing were assessed by radiograph and histology. Bone tissue was processed for total RNA extraction and messenger RNA (mRNA) sequencing (mRNA-Seq). Results. Radiographs and histology demonstrated impaired fracture healing in ZDF rats with incomplete bony bridge formation and an influx of intramedullary inflammatory tissue. In comparison, near-complete bridging between cortices was observed in Sham WT animals. Of 13,160 genes, mRNA-Seq analysis identified 13 that were differentially expressed in ZDF rat callus, using a false discovery rate (FDR) threshold of 10%. Seven genes were upregulated with high confidence (FDR = 0.05) in ZDF fracture callus, most with known roles in inflammation. Conclusion. These findings suggest that elevated or prolonged inflammation contributes to delayed fracture healing in T2DM. The identified genes may be used as biomarkers to monitor and treat delayed fracture healing in diabetic patients. Cite this article: Bone Joint Res 2023;12(10):657–666

Fracture fixation has advanced significantly with the introduction of locked plating and minimally invasive surgical techniques. However, healing complications occur in up to 10% of cases, of which a significant portion may be attributed to unfavorable mechanical conditions at the fracture. Moreover, state-of-the-art plates are prone to failure from excessive loading or fatigue. A novel biphasic plating concept has been developed to create reliable mechanical conditions for timely bone healing and simultaneously improve implant strength. The goal of this study was to test the feasibility and investigate the robustness of fracture healing with a biphasic plate in a large animal experiment. Twenty-four sheep underwent a 2mm mid-diaphyseal tibia osteotomy stabilized with either the novel biphasic plate or a control locking plate. Different fracture patterns in terms of defect location and orientation were investigated. Animals were free to fully bear weight during the post-operative period. After 12 weeks, the healing fractures were evaluated for callus formation using micro-computer tomography and strength and stiffness using biomechanical testing. No plate deformation or failures were observed under full weight bearing with the biphasic plate. Osteotomies stabilized with the biphasic plate demonstrated robust callus formation. Torsion tests after plate removal revealed no statistical difference in peak torsion to failure and stiffness for the different fracture patterns stabilized with the biphasic plate. However, the biphasic plate group specimens were 45% stronger (p=0.002) and 48% stiffer (p=0.007) than the controls. The results of this large animal study demonstrate the clinical potential of this novel stabilization concept

Introduction. Cancellous and cortical bone used as a delivery vehicle for antibiotics. Recent studies with cancellous bone as an antibiotic carrier in vitro and in vivo showed high initial peak concentrations of antibiotics in the surrounding medium. However, high concentrations of antibiotics can substantially reduce osteoblast replication and even cause cell death. Objectives. To determine whether impregnation with gentamycine impair the incorporation of bone allografts, as compared to allografts without antibiotic. Materials and method. Seventy two healthy rabbits (24 rabbits in each group) were used for this study. Bone defects (3-mm diameter, 10-mm depth) were created in the femur. Human femoral head prepared according to the Marburg bone bank system was used as bone allograft. In the experimental groups, in 1 group - the defects were filled with bone allografts, in 2 group – Perforated Gentamycin-impregnated bone allografts. The control group did not receive any filling. The animals were killed after 14, 30 and 60 days. Evaluations consisted of X-ray plain radiography, histology at 14-, 30- and 60-days post-surgery. Results. Active osteoblast activity and active formation of new bones were detected around the defect area in all groups, but the amount of new bone formation was greater in the experimental groups than the control group. We found no statistically significant differences in the rate of bone formation between 1 and 2 groups at 14, 30 and 60 days in any of the parameters studied. X-ray results showed no significant difference in bony callus formation around allografts in 1 and 2 groups. In contrast, no significant callus formation was observed in the control group. Conclusion. The use of gentamycin-impregnated bone allografts may be of value in procedures performed at the site of osteomyelitis which require a second stage reconstruction with impacted bone grafting techniques

Aims. A growing number of fractures progress to delayed or nonunion, causing significant morbidity and socioeconomic impact. Localized delivery of stem cells and subcutaneous parathyroid hormone (PTH) has been shown individually to accelerate bony regeneration. This study aimed to combine the therapies with the aim of upregulating fracture healing. Methods. A 1.5 mm femoral osteotomy (delayed union model) was created in 48 female juvenile Wistar rats, aged six to nine months, and stabilized using an external fixator. At day 0, animals were treated with intrafracture injections of 1 × 10. 6. cells/kg bone marrow mesenchymal stem cells (MSCs) suspended in fibrin, daily subcutaneous injections of high (100 μg/kg) or low (25 μg/kg) dose PTH 1-34, or a combination of PTH and MSCs. A group with an empty gap served as a control. Five weeks post-surgery, the femur was excised for radiological, histomorphometric, micro-CT, and mechanical analysis. Results. Combination therapy treatment led to increased callus formation compared to controls. In the high-dose combination group there was significantly greater mineralized tissue volume and trabecular parameters compared to controls (p = 0.039). This translated to significantly improved stiffness (and ultimate load to failure (p = 0.049). The high-dose combination therapy group had the most significant improvement in mean modified Radiographic Union Score for Tibia fractures (RUST) compared to controls (13.8 (SD 1.3) vs 5.8 (SD 0.5)). All groups demonstrated significant increases in the radiological scores – RUST and Allen score – histologically compared to controls. Conclusion. We demonstrate the beneficial effect of localized MSC injections on fracture healing combined with low- or high-dose teriparatide, with efficacy dependent on PTH dose. Cite this article: Bone Joint Res 2021;10(10):659–667

The course of secondary fracture healing typically consists of four major phases including inflammation, soft and hard callus formation, and bone remodeling. Callus formation is promoted by mechanical stimulation, yet little is known about the healing tissue response to strain stimuli over shorter timeframes on hourly and daily basis. The aim of this study was to explore the hourly, daily and weekly variations in bone healing progression and to analyze the short-term response of the repair tissue to well-controlled mechanical stimulation. A system for continuous monitoring of fracture healing was designed for implantation in sheep tibia. The experimental model was adapted from Tufekci et al. 2018 and consisted of 3 mm transverse osteotomy and 30 mm bone defect resulting in an intermediate mobile bone fragment in the tibial shaft. Whereas the distal and proximal parts of the tibia were fixed with external fixator, the mobile fragment was connected to the proximal part via a second, active fixator. A linear actuator embedded in the active fixator moved the mobile fragment axially, thus stimulating mechanically the tissue in the osteotomy gap via well-controlled displacement being independent from the sheep's functional weightbearing. A load sensor was integrated in the active fixation to measure the force acting in the osteotomy gap. During each stimulation cycle the displacement and force magnitudes were recorded to determine in vivo fracture stiffness. Following approval of the local ethics committee, experiments were conducted on four skeletally mature sheep. Starting from the first day after surgery, the daily stimulation protocols consisted of 1000 loading events equally distributed over 12 hours from 9:00 to 21:00 resulting in a single loading event every 44 seconds. No stimulation was performed overnight. One animal had to be excluded due to inconsistencies in the load sensor data. The onset of tissue stiffening was detected around the eleventh day post-op. However, on a daily basis, the stiffness was not steadily increasing, but instead, an abrupt drop was observed in the beginning of the daily stimulations. Following this initial drop, the stiffness increased until the last stimulation cycle of the day. The continuous measurements enabled resolving the tissue response to strain stimuli over hours and days. The presented data contributes to the understanding of the influence of patient activity on daily variations in tissue stiffness and can serve to optimize rehabilitation protocols post fractures

Intramedullary nails (IMNs) are the current gold standard for treatment of long bone diaphyseal and selected metaphyseal fractures. Their design has undergone many revisions to improve fixation techniques, conform to the bone shape with appropriate anatomic fit, reduce operative time and radiation exposure, and extend the indication of the same implant for treatment of different fracture types with minimal soft tissue irritation. The IMNs are made or either titanium alloy or stainless steel and work as load-sharing internal splints along the long bone, usually accommodating locking elements – screws and blades, often featuring angular stability and offering different configurations for multiplanar fixation – to secure secondary fracture healing with callus formation in a relative-stability environment. Bone cement augmentation of the locking elements can modulate the construct stiffness, increase the surface area at the bone-implant interface, and prevent cut-through of the locking elements. The functional requirements of IMNs are related to maintaining fracture reduction in terms of length, alignment and rotation to enhance fracture healing. The load distribution during patient's activities is along the entire bone-nail interface, with nail length and anatomic fit being important factors to avoid stress risers

Objectives. Small animal models of fracture repair primarily investigate indirect fracture healing via external callus formation. We present the first described rat model of direct fracture healing. Methods. A rat tibial osteotomy was created and fixed with compression plating similar to that used in patients. The procedure was evaluated in 15 cadaver rats and then in vivo in ten Sprague-Dawley rats. Controls had osteotomies stabilised with a uniaxial external fixator that used the same surgical approach and relied on the same number and diameter of screw holes in bone. Results. Fracture healing occurred without evidence of external callus on plain radiographs. At six weeks after fracture fixation, the mean stress at failure in a four-point bending test was 24.65 N/mm. 2. (. sd. 6.15). Histology revealed ‘cutting-cones’ traversing the fracture site. In controls where a uniaxial external fixator was used, bone healing occurred via external callus formation. Conclusions. A simple, reproducible model of direct fracture healing in rat tibia that mimics clinical practice has been developed for use in future studies of direct fracture healing

Secondary bone healing is impacted by the extent of interfragmentary motion at the fracture site. It provides mechanical stimulus that is required for the formation of fracture callus. In clinical settings, interfragmentary motion is induced by physiological loading of the broken bone – for example, by weight-bearing. However, there is no consensus about when mechanical stimuli should be applied to achieve fast and robust healing response. Therefore, this study aims to identify the effect of the immediate and delayed application of mechanical stimuli on secondary bone healing. A partial tibial osteotomy was created in twelve Swiss White Alpine sheep and stabilized using an active external fixator that induced well-controlled interfragmentary motion in form of a strain gradient. Animals were randomly assigned into two groups which mimicked early (immediate group) and late (delayed group) weight-bearing. The immediate group received daily stimulation (1000 cycles/day) from the first day post-op and the delayed group from the 22nd day post-op. Healing progression was evaluated by measurements of the stiffness of the repair tissue during mechanical stimulation and by quantifying callus area on weekly radiographs. At the end of the five weeks period, callus volume was measured on the post-mortem high-resolution computer tomography (HRCT) scan. Stiffness of the repair tissue (p<0.05) and callus progression (p<0.01) on weekly radiographs were significantly larger for the immediate group compared to the delayed group. The callus volume measured on the HRCT was nearly 3.2 times larger for the immediate group than for the delayed group (p<0.01). This study demonstrates that the absence of immediate mechanical stimuli delays callus formation, and that mechanical stimulation already applied in the early post-op phase promotes bone healing

Virtual mechanical testing is a method for measuring bone healing using finite element models built from computed tomography (CT) scans. Previously, we validated a dual-zone material model for ovine fracture callus that differentiates between mineralized woven bone and soft tissue based on radiodensity. 1. The objective of this study was to translate the dual-zone material model from sheep to two important clinical scenarios: human tibial fractures in early-stage healing and late-stage nonunions. CT scans for N = 19 tibial shaft fractures were obtained prospectively at 12 weeks post-op. A second group of N = 33 tibial nonunions with CT scans were retrospectively identified. The modeling techniques were based on our published method. 2. The dual-zone material model was implemented for humans by performing a cutoff sweep for both the 12-week and nonunion groups. Virtual torsional rigidity (VTR) was calculated as VTR = ML/φ [N-m. 2. /°], where M is the moment reaction, L is the diaphyseal segment length, and φ is the angle of twist. As the soft tissue cutoff was increased, the rigidity of the clinical fractures decreased and soft tissue located within the fracture gaps produced higher strains that are not predicted without the dual zone approach. The structural integrity of the nonunions varied, ranging from very low rigidities in atrophic cases to very high rigidities in highly calcified hypertrophic cases, even with dual-zone material modeling. Human fracture calluses are heterogeneous, comprising of woven bone and interstitial soft tissue. Use of a dual-zone callus material model may be instrumental in identifying delayed unions during early healing when callus formation is minimal and/or predominantly fibrous with little mineralization. ACKNOWLEDGEMENTS:. This work was supported by the National Science Foundation (NSF) grant CMMI-1943287

Osteoprogenitors on the inner layer of periosteum are the major cellular contributors to appositional bone growth and bone repair by callus formation. Previous work showed that periosteal-derived cells have little or no osteogenic activity under standard in vitro osteogenic culture conditions. This study was conducted to determine what growth factor(s) can activate periosteal osteogenic capacity. This study was conducted with IACUC approval. Periosteum from five equine donors was digested in collagenase for 3-4 hours at 37C. Isolated periosteal cells were maintained in DMEM/10% FBS medium and exposed to PDGF, Prostaglandin E2, BMP-2 and TGF-b3 at a range of concentrations for 72 hours. Changes in osteogenic gene expression (Runx2, OSX and ALP) were measured by qPCR. Periosteal cells were pre-treated with TGF-b3 or maintained in control medium were transferred into basal or osteogenic medium. Osteogenic status was assessed by Alizarin Red staining for mineralized matrix, ALP enzymatic activity and induction of osteogenic genes. PDGF, PgE2 and BMP-2 had little impact on expression of osteogenic markers by periosteal cells. In contrast, TGF-b3 stimulated significant increases in Osterix (over 100-fold) ALP expression (over 70-fold). Pre-treating periosteal cells with TGF-b3 for 72 hours stimulated rapid cell aggregation and aggregate mineralization once cells were transferred to osteogenic medium, while cells not exposed to TGF-b3 exhibited minimal evidence of osteogenic activity. This study indicate that TGF-b signaling is vital for periosteal osteogenic activity. Transient ‘priming’ of periosteal cells through TGF-b exposure was sufficient to activate subsequent osteogenesis without requiring ongoing growth factor stimulation. TGF beta ligands are secreted by many cell types, including periosteal progenitors and osteocytes, providing opportunities for both autocrine and paracrine pathways to regulate periosteal bone formation under homeostatic and reparative conditions

Abstract. Introduction. Vitamin D deficiency in the UK is well documented − 30–40% of the population. It is an essential component of calcium metabolism and adequate levels are important for bone healing. Studies have demonstrated an overall prevalence of vitamin D deficiency/insufficiency at 77% in trauma patients aged >18, deficiency alone was 39%. Adequate vitamin D levels have a positive effect on bone mineral density and callus formation at fracture sites. Methods. We conducted a retrospective consecutive case series of all patients aged 0–50 undergoing surgical management for any fracture in October 2021 to March 2022. We assessed if vitamin D levels were checked and if patients were prescribed replacement as per local guidelines. Results. A total of 131 patients were identified, (mean 29 years; 83 male and 48 female). Most cases were upper limb fractures (n=78, 60%), as opposed to lower limb (n=53, 40%). Only 20 (15%) had their levels checked, of which 13 (65%) were insufficient/deficient (10 insufficiency, 2 deficiency, 1 severe deficiency). Of these 13 patients, only 3 (23%) were prescribed replacement therapy. Conclusions. Only a small proportion of patients had their levels checked, however the majority were insufficient/deficient. The prevalence in our study is consistent with larger epidemiology studies, which reflect a higher rate of deficiency in fracture patients compared to the general population. Thus, we propose that all patients in this age group should undergo a vitamin d level check upon time of clerking and this should be accurately treated as per trust guidance

Our previous rat study demonstrated an ex vivo-created “Biomimetic Hematoma” (BH) that mimics the intrinsic structural properties of normal fracture hematoma, consistently and efficiently enhanced the healing of large bone defects at extremely low doses of rhBMP-2 (0.33 μg). The aim of this study was to determine if an extremely low dose of rhBMP-2 delivered within BH can efficiently heal large bone defects in goats. Goat 2.5 cm tibial defects were stabilized with circular fixators, and divided into groups (n=2-3): 2.1 mg rhBMP-2 delivered on an absorbable collagen sponge (ACS); 52.5 μg rhBMP-2 delivered within BH; and an empty group. BH was created using autologous blood with a mixture of calcium and thrombin at specific concentrations. Healing was monitored with X-rays. After 8 weeks, femurs were assessed using microCT. Using 2.1 mg on ACS was sufficient to heal 2.5 cm bone defects. Empty defects resulted in a nonunion after 8 weeks. Radiographic evaluation showed earlier and more robust callus formation with 97.5 % (52.5 μg) less of rhBMP-2 delivered within the BH, and all tibias were fully bridged at 3 weeks. The bone mineral density was significantly higher in defects treated with BH than with ACS. Defects in the BH group had smaller amounts of intramedullary and cortical trabeculation compared to the ACS group, indicating advanced remodeling. The results confirm that the delivery of rhBMP-2 within the BH was much more efficient than on an ACS. Not only did the large bone defects heal consistently with a 40x lower dose of rhBMP-2, but the quality of the defect regeneration was also superior in the BH group. These findings should significantly influence how rhBMP-2 is delivered clinically to maximize the regenerative capacity of bone healing while minimizing the dose required, thereby reducing the risk of adverse effects