niveles de organización tras fractura incompleta

Healing following an incomplete fracture involves multiple intertwined levels of biological organization that range from molecular signaling pathways to cellular, tissue, and organ system processes, ultimately restoring bone integrity and function.

At the molecular and biochemical level, early fracture healing is initiated by hypoxia-induced signaling pathways involving reactive oxygen species (ROS) that regulate key transcription factors such as APEX1, HIF-1α, BMP2, and others. These factors control gene expression essential for initiating repair mechanisms including chondrocyte differentiation and osteogenesis Valdés-Fernández et al. 2026,Hu et al. 2025. Molecules like Noggin and SLIT3 modulate bone morphogenetic protein (BMP) signaling and vascular guidance, thereby regulating the timing and coordination of angiogenesis and osteogenesis Kim et al. 2025,Hu et al. 2025. Additionally, extracellular vesicles such as exosomes ferry microRNAs and proteins that modulate cell behavior during bone regeneration Hu et al. 2025.

At the cellular level, numerous cell types participate sequentially and concurrently. Mesenchymal progenitor/stem cells proliferate and differentiate into chondrocytes and osteoblasts, while osteoclasts contribute to remodeling the bone matrix. Endothelial cells form specialized H type blood vessels that both sustain osteogenesis and support hematopoiesis within the bone marrow microenvironment Kim et al. 2025. Immune cells such as macrophages orchestrate inflammation and subsequent healing phases, and their derived exosomes enhance osteogenesis and angiogenesis Hu et al. 2025. The proliferation marker Ki-67 shows active cell proliferation in the periosteal layer early in healing Valdés-Fernández et al. 2026.

At the tissue level, the healing process progresses through the establishment of a hematoma and periosteal response, formation of a soft callus rich in cartilage matrix, followed by a hard callus through endochondral ossification involving cartilage resorption and replacement by woven bone, and eventual remodeling into lamellar bone Valdés-Fernández et al. 2026,Hu et al. 2025. This involves deposition of collagen I, osteocalcin expression, and matrix metalloproteinases (MMPs) that degrade cartilage to allow vascular invasion. Angiogenesis is tightly coupled with osteogenesis via the formation of H type blood vessels characterized by CD31 and endomucin expression Kim et al. 2025. Exosome-mediated signaling enhances this vascularization Hu et al. 2025.

Finally, at the level of organ and system integration, restoration of bone strength and continuity involves the re-establishment of cortical and trabecular bone density, integration with surrounding skeletal structures, and normalization of biomechanical function Kim et al. 2025. Although localized bone mineral density may transiently decrease at the fracture site during callus remodeling, complete consolidation typically occurs within weeks to months Kim et al. 2025. This multi-level coordinated response ensures functional fracture healing.

In summary, healing after an incomplete fracture is orchestrated through a complex, hierarchical interplay involving:

• Molecular signals regulating gene expression and cell behavior (e.g., APEX1-mediated control of BMP2, HIF-1α mediated angiogenesis)
• Cellular players including mesenchymal progenitors, chondrocytes, osteoblasts, osteoclasts, endothelial and immune cells
• Tissue-level events such as callus formation, cartilage resorption, and bone remodeling mediated by extracellular matrix deposition and vascular invasion
• Organ-level processes restoring bone architecture and mechanical integrity

These biological levels are emphasized in both UK clinical guidelines on fracture management NICE NG37,NICE NG38 and recent experimental and translational studies highlighting molecular and cellular mechanisms underpinning fracture repair and potential therapeutic targets Kim et al. 2025,Valdés-Fernández et al. 2026,Hu et al. 2025.