Introduction. The hematoma occurring at a fracture site is known to play an important role in fracture healing. Previously, we demonstrated that fracture hematoma contained multilineage mesenchymal progenitor cells. On the other hand, the process of fracture healing is associated by two different mechanisms, intramembranous and endochondral. However, there are no reports proving the details about cellular analysis in the process of endochondoral ossification. Hypothesis. We hypothesized that one of the cell origins for endochondral ossification after fracture was hematoma. Materials & Methods. Fracture hematoma was obtained during osteosynthesis. Hematoma-derived cells were isolated and cultured for 5-weeks of chondrogenic induction followed by 2-weeks hypertrophic induction using pellet culture system. The pellets were analyzed histologically and immunohistochemically. The gene expression levels of chondrogenic, hypertrophic, osteogenic and angiogenic markers were measured by real-time PCR. Results. The histological and immunohistochemical analysis revealed that the Hematoma-derived cells differentiated into hypertrophic chondrocytes through chondrocytes, and finally differentiate into calcifying chondrocytes. The same trend was seen in the gene expression using real-time PCR analysis. Discussion & Conclusions. Our results suggest that fracture hematoma may be an origin of cells which play key roles in the process of endochondoral ossification during fracture healing

Introduction. It is well known that blood flow is a critical key component of fracture repair. Previously, we demonstrated that transcutaneous application of CO2 increased blood flow in the human body. To date, there has been no report investigating the effect of the carbonated therapy on fracture repair. Hypothesis. We hypothesized that the transcutaneous application of CO2 to fracture site would accelerate fracture repair. Materials & Methods. A closed femoral shaft fracture was produced in rats. Transcutaneous CO2 absorption enhancing hydrogel and CO2 adaptor that sealed the body surface and retained the gas inside were used for CO2 treatment. Rats without CO2 treatment served as control. Radiographic, biomechanical and histological analysis was performed to assess the fracture repair. Gene expression of chondrogenic, hypertrophic, osteogenic and angiogenic markers was measured by real-time PCR at 1, 2, 3, and 4 weeks post-fracture. Results. Union rate, biomechanical properties, and gene expression of chondrogenic, hypertrophic, osteogenic and angiogenic markers was significantly higher in CO2 group compared to control group. Histological evaluation demonstrated that enchondral ossification was promoted in CO2 group. Discussion & Conclusions. Our study indicate that transcutaneous application of CO2 accelerates fracture repair via acceleration of endochondral ossification and vascularization, and may become a novel and useful therapy for promoting fracture repair

INTRODUCTION. Autologous bone grafts are considered gold standard in the repair of bone defects. However they are limited in supply and are associated with donor site morbidity. This has led to the development of synthetic bone graft substitute (BGS) materials, many of which have been reported as being osteoinductive. The structure of the BGS is important and bone formation has been observed in scaffolds with a macroporous morphology. Smaller pores termed ‘strut porosity’ may also be important for osteoinduction. The aim of this study was to compare the osteoinductive ability of one silicate-substituted calcium phosphate (SiCaP) with differing strut porosities in an ectopic ovine model. Our hypothesis was that SiCaP with greater strut porosity would be more osteoinductive. METHODS. The osteoinduction of SiCaP BGS with two different strut porosities (AF and AF++) was investigated. The materials had an identical chemical composition and morphological structure but differing strut porosity (AF=22.5%, AF++=47%). Implants were inserted into the paraspinal muscles in skeletally mature sheep. Procedures were carried out in compliance with UK Home Office regulations. There were 12 implants in each group. Implants remained in vivo for 8 and 12 weeks and on retrieval were prepared for undecalcified histology. Sections were stained and examined using light microscopy. A line intersection method was used to quantify bone, implant and implant surface/bone contact within seven random regions of interest along each implant. A Mann-Whitney U test was used for statistical analysis where p values < 0.05 were considered significant. RESULTS. Bone formation was observed to be greater in the AF++ group at 8 (AF=0.2%+/−0.15; AF++=0.44%+/−0.12) and significantly higher at 12 weeks (AF=1.33% +/−0.84; AF++=6.17%+/−1.51) (p=0.04). Significantly higher implant surface/bone contact was observed in the AF++ group at 8 (AF=0.67%+/−0.52; AF++=3.30%+/−1.17) (p=0.04) and 12 weeks (AF=3.06%+/−1.89; AF++=21.82%+/−5.59) (p=0.01). The % implant measured was less in the AF++ group at 8 (AF=39.06%+/−1.26; AF++=33.09%+/−2.14) and 12 weeks (AF=36.05% +/−3.55; AF++=30.60%+/−2.29) but this was not significant. Histology revealed bone formation within BGS strut pores measuring < 50um. Endochondral and intramembranous ossification were also observed in both groups. DISCUSSION. The results indicate that higher strut porosity promotes greater osteoinduction in SiCaP materials. This could be attributed to the micropores providing a greater surface area for the action of growth factors and osteoblasts leading to the formation of bone at an earlier time point. Endochondral ossification was an unusual finding as this is usually associated with bone formation secondary to Bone Morphogenetic proteins (BMPs). This suggests that the osteoinductive mechanisms by SiCaP may involve cytokines such as BMPs

Aims

Heterotopic ossification (HO) is a common complication after elbow trauma and can cause severe upper limb disability. Although multiple prognostic factors have been reported to be associated with the development of post-traumatic HO, no model has yet been able to combine these predictors more succinctly to convey prognostic information and medical measures to patients. Therefore, this study aimed to identify prognostic factors leading to the formation of HO after surgery for elbow trauma, and to establish and validate a nomogram to predict the probability of HO formation in such particular injuries.

MicroRNAs (miRNAs ) are small non-coding RNAs that regulate gene expression. We hypothesised that the functions of certain miRNAs and changes to their patterns of expression may be crucial in the pathogenesis of nonunion. Healing fractures and atrophic nonunions produced by periosteal cauterisation were created in the femora of 94 rats, with 1:1 group allocation. At post-fracture days three, seven, ten, 14, 21 and 28, miRNAs were extracted from the newly generated tissue at the fracture site. Microarray and real-time polymerase chain reaction (PCR) analyses of day 14 samples revealed that five miRNAs, miR-31a-3p, miR-31a-5p, miR-146a-5p, miR-146b-5p and miR-223-3p, were highly upregulated in nonunion. Real-time PCR analysis further revealed that, in nonunion, the expression levels of all five of these miRNAs peaked on day 14 and declined thereafter.

Our results suggest that miR-31a-3p, miR-31a-5p, miR-146a-5p, miR-146b-5p and miR-223-3p may play an important role in the development of nonunion. These findings add to the understanding of the molecular mechanism for nonunion formation and may lead to the development of novel therapeutic strategies for its treatment.

Cite this article: Bone Joint J 2015; 97-B:1144–51.

Objectives

Bisphosphonates are widely used as first-line treatment for primary and secondary prevention of fragility fractures. Whilst they have proved effective in this role, there is growing concern over their long-term use, with much evidence linking bisphosphonate-related suppression of bone remodelling to an increased risk of atypical subtrochanteric fractures of the femur (AFFs). The objective of this article is to review this evidence, while presenting the current available strategies for the management of AFFs.

Heterotopic ossification occurring after the use of commercially available bone morphogenetic proteins has not been widely reported. We describe four cases of heterotopic ossification in patients treated with either recombinant bone morphogenetic protein 2 or recombinant bone morphogenetic protein 7. We found that while some patients were asymptomatic, heterotopic ossification which had occurred around a joint often required operative excision with good results.

In patients with traumatic brain injury and fractures of long bones, it is often clinically observed that the rate of bone healing and extent of callus formation are increased. However, the evidence has been unconvincing and an association between such an injury and enhanced fracture healing remains unclear. We performed a retrospective cohort study of 74 young adult patients with a mean age of 24.2 years (16 to 40) who sustained a femoral shaft fracture (AO/OTA type 32A or 32B) with or without a brain injury. All the fractures were treated with closed intramedullary nailing. The main outcome measures included the time required for bridging callus formation (BCF) and the mean callus thickness (MCT) at the final follow-up. Comparative analyses were made between the 20 patients with a brain injury and the 54 without brain injury. Subgroup comparisons were performed among the patients with a brain injury in terms of the severity of head injury, the types of intracranial haemorrhage and gender. Patients with a brain injury had an earlier appearance of BCF (p < 0.001) and a greater final MCT value (p < 0.001) than those without. There were no significant differences with respect to the time required for BCF and final MCT values in terms of the severity of head injury (p = 0.521 and p = 0.153, respectively), the types of intracranial haemorrhage (p = 0.308 and p = 0.189, respectively) and gender (p = 0.383 and p = 0.662, respectively).

These results confirm that an injury to the brain may be associated with accelerated fracture healing and enhanced callus formation. However, the severity of the injury to the brain, the type of intracranial haemorrhage and gender were not statistically significant factors in predicting the rate of bone healing and extent of final callus formation.