Fracture hematoma micro-architecture influences transcriptional profile and plays a crucial role in determining bone healing outcomes.

The hematoma that forms between broken fragments of bone serves as a natural fibrin scaffold, and its removal from the defect site delays bone healing. The hypothesis of this study is that the microarchitectural and mechanical properties of the initially formed hematoma has a significant effect on the regulation of the biological process, which ultimately determines the outcome of bone healing. To mimic three healing conditions in the rat femur (normal, delayed, and non-healing bone defects), three different defect sizes of 0.5, 1.5, and 5.0 mm, are respectively used. The analysis of 3-day-old hematomas demonstrates clear differences in fibrin clot micro-architecture in terms of fiber diameter, fiber density, and porosity of the formed fibrin network, which result in different mechanical properties (stiffness) of the hematoma in each model. Those differences directly affect the biological processes involved. Specifically, RNA-sequencing reveals almost 700 differentially expressed genes between normally healing and non-healing defects, including significantly up-regulated essential osteogenic genes in normally healing defects, also differences in immune cell populations, activated osteogenic transcriptional regulators as well as potential novel marker genes. Most importantly, this study demonstrates that the healing outcome has already been determined during the hematoma phase of bone healing, three days post-surgery.

Antegrade Elastic Intramedullary Nailing Insertion Technique Results in Higher Incidence of Symptomatic Implants in Pediatric Ulnar Fractures.

Retrograde and antegrade nailing techniques are the two options available to a surgeon when using elastic stable intramedullary nailing; however, the literature comparing these two nailing techniques is scarce. Thus, we conducted a retrospective review of all pediatric and adolescent ulnar fractures treated with elastic stable intramedullary nailing at our facility. We hypothesize that the clinical outcomes (implant and wound complications) and the time between surgery and radiographic union will be similar for both techniques. Methods: A retrospective chart review of pediatric ulnar fracture patients treated at our facility was performed. Demographic and health information associated with the injury were collected, and the clinical outcomes of the two techniques were compared. Results: A total of 53 patients with 54 fractures were included in this study. Antegrade nail insertion was used to treat 59.2% fractures. Radiographic union was achieved in all patients. Nail insertion technique was not associated with postoperative wound complications, time to radiographic union or implant removal, or significant deficits in upper extremity rotation (P > 0.05). Antegrade nailing resulted in a symptomatic implantation 3.97 times more frequently than compared with retrograde nailing (P = 0.036). Discussion: Antegrade nailing demonstrates a similar healing profile but higher implant complications compared with the retrograde nailing technique in pediatric ulnar fractures.