Bone and Fracture Healing powerpoint for resident

Fracture healing for residen

1. Bone and Fracture Healing .

2. Bone Healing 01

3. Remodeling

4. Cellular Mechanisms The cellular mechanisms of bone healing involve different cell types, including osteoblasts, osteoclasts, and chondrocytes. Osteoblasts are responsible for new bone formation, while osteoclasts facilitate bone resorption. Chondrocytes play a crucial role in the cartilage stage of healing. Additionally, signaling molecules such as growth factors and cytokines coordinate these cellular activities, ensuring a successful and effective healing process.

5. Phases of Bone Healing Bone healing typically involves three phases: the inflammatory phase, the reparative phase, and the remodeling phase. The inflammatory phase begins immediately after the fracture, characterized by hematoma formation and inflammation, which provide the necessary environment for healing. The reparative phase involves the formation of a soft callus, which later transforms into a hard callus as new bone starts to form. Finally, the remodeling phase refines the bone structure, restoring its original shape and strength over time.

6. Fracture healing involves a complex and sequential set of events to restore injured bone to pre-fracture condition  stem cells are crucial to the fracture repair process periosteum and endosteum are the two major sources Fracture stability dictates the type of healing that will occur   mechanical stability governs the mechanical strain when the strain is below 2%, primary bone healing will occur when the strain is between 2% and 10%, secondary bone healing will occur 

7. Modes of bone healing  primary bone healing (strain is < 2%)   intramembranous healing occurs via Haversian remodeling occurs with absolute stability constructs   secondary bone healing (strain is between 2%-10%) involves responses in the periosteum and external soft tissues. endochondral healing   occurs with non-rigid fixation, as fracture braces, external fixation, bridge plating, intramedullary nailing, etc.  bone healing may occur as a combination of the above two process depending on the stability throughout the construct

8. Secondary Bone Healing Inflammation He matoma forms and provides a source of hematopoietic cells capable of secreting growth factors.  Macrophages, neutrophils, and platelets release several cytokines      this includes PDGF, TNF-Alpha, TGF-Beta, IL-1,6, 10,12     they may be detected as early as 24 hours post-injury     lack of TNF-Alpha ( ie . HIV) results in delay of both endochondral/ intramembranous ossification  BMPs, fibroblasts and mesenchymal cells migrate to fracture site and granulation tissue forms around fracture ends      During fracture healing granulation tissue tolerates the greatest strain before failure  Osteoblasts and fibroblasts proliferate      Inhibition of COX-2 ( ie NSAIDs) causes repression of runx-2/ osterix , which are critical for differentiation of osteoblastic cells 

9. Repair Primary callus forms within two weeks. If the bone ends are not touching, then bridging soft callus forms.     The mechanical environment drives differentiation of either osteoblastic (stable enviroment ) or chondryocytic (unstable environment) lineages of cells Endochondral ossification converts soft callus to hard callus (woven bone). Medullary callus also supplements the bridging soft callus     Cytokines drive chondocytic differentiation.     Cartilage production provides provisional stabilization Type II collagen (cartilage) is produced early in fracture healing and then followed by type I collagen (bone) expression Amount of callus is inversely proportional to extent of immobilization     Primary cortical healing occurs with rigid immobilization ( ie . compression plating)     Endochondral healing with periosteal bridging occurs with closed treatment

10. Begins in middle of repair phase and continues long after clinical union    Chondrocytes undergo terminal differentiation             Complex interplay of signaling pathways including, indian hedgehog ( Ihh ), parathyroid hormone-related peptide ( PTHrP ), FGF and BMP             These molecules are also involved in terminal differentiation of the appendicular skeleton     Type X collagen types is expressed by hypertrophic chondrocytes as the extraarticular matrix undergoes calcification       Proteases degrade the extracellular matrix     Cartilaginous calcification takes place at the junction between the maturing chondrocytes and newly forming bone             Multiple factors are expressed as bone is formed including TGF-Betas, IGFs, osteocalcin, collagen I, V and XI     Subsequently, chondrocytes become apoptotic and VEGF production leads to new vessel invasion     Newly formed bone (woven bone) is remodeling via organized osteoblastic/osteoclastic activity Shaped through      Wolff's law: bone remodels in response to mechanical stress     Piezoelectric charges: bone remodels is response to electric charges: compression side is electronegative and stimulates osteoblast formation, tension side is electropostive and simulates osteoclasts REMODELLING

11. Factors Affecting Healing patient age, nutritional status, Younger patients Nutritional deficiencies, such as a lack of vitamin D or calcium, can impede the healing process. comorbidities like diabetes or osteoporosis can complicate healing by affecting bone density and circulation.

12. Fracture Management 02

13. Complications and Challenges Fracture healing can be complicated by issues such as non-union or malunion, where the bone does not heal correctly, leading to persistent pain or functional limitations. Infections are a significant concern, particularly in open fractures. Additional challenges include addressing pain management and rehabilitation to ensure a successful recovery post-fracture. Identifying and mitigating these complications is critical in orthopedic practice.

14. Conclusions Understanding the processes of bone healing and the intricacies of fracture management is essential for optimizing patient outcomes in orthopedic practice. Adequate knowledge of the factors influencing healing, types of fractures, available treatment options, and potential complications equips healthcare providers to make informed decisions for effective patient care.

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