Tendon disorders frequently occur and recent evidence has clearly implicated the presence of immune cells and inflammatory events during early tendinopathy. However, the origin and properties of these cells remain poorly defined. Therefore, the aim of this study was to determine the presence of cells in healthy rodent and human tendon tissue fulfilling macrophage-like functions. Using various transgenic reporter mouse models, we demonstrate the presence of tendon-resident cells in the dense matrix of the tendon core expressing the fractalkine (Fkn) receptor CX3CR1 and its cognate ligand CX3CL1/Fkn. Pro-inflammatory stimulation of 3D tendon-like constructs in vitro resulted in a significant increase in the expression of IL-1β, IL-6, Mmp3, Mmp9, CX3CL1 and epiregulin, which has been reported to contribute to inflammation, wound healing and tissue repair. Furthermore, we demonstrate that inhibition of the Fkn receptor blocked tendon cell migration in vitro, and show the presence of CX3CL1/CX3CR1/EREG-expressing cells in healthy human tendons. Taken together, we demonstrate the presence of CX3CL1+/CX3CR1+ ‘tenophages’ within the healthy tendon proper, which potentially fulfill surveillance functions in tendons.This article has an associated First Person interview with the first author of the paper.

Purpose Developing a guideline for orthopedic trauma surgeons working in civilian trauma hospitals in low-income countries. Methods This is a retrospective data analysis in a non-governmental organizational trauma hospital in Sierra Leone, Africa. Trauma victims (282), with 349 fractures, were admitted to the hospital 10/2015–01/2016. The incidence of open and closed fractures and the use of implants were evaluated. Results The most common fractures were open and closed tibial shaft fractures and closed femoral shaft fractures in adults, and closed supracondylar humerus fractures in children. The most used implants were external fixators, K-wires, and intramedullary nails. External fixators were used for open fractures, K-wires for closed fractures in children, hand and foot, and nails for closed fractures of the lower extremity in adults. Plates were used the least and mostly for fractures of the upper extremity, the proximal tibia and malleolar region in adults. The complication rate was 5.67%. Conclusion Surgeons in low-income country trauma hospitals should treat conservatively on outpatient basis only, to reduce the amount of stationary patients. Open fractures should be treated with external fixators, and closed fractures in children, hand and foot, with K-wires. Closed fractures in adults of the lower extremity should be nailed, and closed fractures in adults of the upper extremity can be treated with plates.

Objectives We carried out a retrospective cohort study to differentiate geriatric odontoid fractures into stable and unstable and correlated it with fracture fusion rates. Results are based on the literature and on our own experience. The authors propose that the simple Anderson and D’Alonzo classification may not be sufficient for geriatric patients. Methods There were 89 patients ≥ 65 years who presented at our institution with type II and III odontoid fractures from 2003 until 2017 and were included in this study. Each patient was categorized with CT scans to evaluate the type of fracture, fracture gap (mm), fracture angulation (°), fracture displacement (mm) and direction (ventral, dorsal). Fractures were categorized as stable [SF] or unstable [UF] distinguished by the parameters of its angulation (< / > 11°) and displacement (< / > 5 mm) with a follow-up time of 6 months. SFs were treated with a semi-rigid immobilization for 6 weeks, UFs surgically—preferably with a C1–C2 posterior fusion. Results The classification into SFs and UFs was significant for its angulation (P = 0.0006) and displacement (P < 0.0001). SF group (n = 57): A primary stable union was observed in 35, a stable non-union in 10, and an unstable non-union in 8 patients of which 4 were treated with a C1/2 fixation. The overall consolidation rate was 79%. UF group (n = 32): A posterior C1–C2 fusion was carried out in 23 patients, a C0 onto C4 stabilization in 7 and an anterior odontoid screw fixation in 2. The union rate was 100%. Twenty-one type II SFs (91%) consolidated with a nonoperative management (P < 0.001). A primary non-union occurred more often in type II than in type III fractures (P = 0.0023). There was no significant difference in the 30-day overall case fatality (P = 0.3786). Conclusion To separate dens fractures into SFs and UFs is feasible. For SFs, semi-rigid immobilization provides a high consolidation rate. Stable non-unions are acceptable, and the authors suggest a posterior transarticular C1–C2 fixation as the preferred surgical treatment for UFs. Level of evidence Level III.

The repair of large bone defects remains challenging and often requires graft material due to limited availability of autologous bone. In clinical settings, collagen sponges loaded with excessive amounts of bone morphogenetic protein 2 (rhBMP-2) are occasionally used for the treatment of bone non-unions, increasing the risk of adverse events. Therefore, strategies to reduce rhBMP-2 dosage are desirable. Silk scaffolds show great promise due to their favorable biocompatibility and their utility for various biofabrication methods. For this study, we generated silk scaffolds with axially aligned pores, which were subsequently treated with 10× simulated body fluid (SBF) to generate an apatitic calcium phosphate coating. Using a rat femoral critical sized defect model (CSD) we evaluated if the resulting scaffold allows the reduction of BMP-2 dosage to promote efficient bone repair by providing appropriate guidance cues. Highly porous, anisotropic silk scaffolds were produced, demonstrating good cytocompatibility in vitro and treatment with 10× SBF resulted in efficient surface coating. In vivo, the coated silk scaffolds loaded with a low dose of rhBMP-2 demonstrated significantly improved bone regeneration when compared to the unmineralized scaffold. Overall, our findings show that this simple and cost-efficient technique yields scaffolds that enhance rhBMP-2 mediated bone healing.