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LOCOMOTOR – Wound & fracture healing Wound = “any break in the skin, mucous membrane or organ via a tear/cut/puncture Fracture = “a complete or incomplete break in a bone resulting from the application of excessive force” WOUNDS Sequence of changes in wounds: Coagulation Inflammation Granulation tissue formation Angiogenesis Contraction to reduce the size of the wound: fibroblasts myofibroblasts Re-epithelialisation Arrest of proliferation Remodelling 0-24 hours - Small vessel damage haemorrhage. - Coagulation results in fibrin filling the wound gap. 1-2 days - Neutrophils migrate acute inflammation - Erythema & swelling - Basal epithelia proliferat n - Migration of 3-4 days - Vascular granulation tissue fills the space - More fibroblasts & myofibroblasts are recruited - Collagen deposition 5 days - Temporary type III collagen matrix replaced by type I collagen arranged in bundles to form a scar - Epidermis returns to normal thickness What effects do growth factors have? - Attract macrophages - Attract fibroblasts - Fibroblast proliferation - Angiogenesis (by VEGF) - Collagen synthesis - Proliferation of epidermis After 2 weeks – wound has 50% strength of normal skin After 12 months – wound has 80% strength of normal skin Total blanching of scar takes months/years Granulation tissue = combination of a rich vascular supply

Wound and Fracture Healing

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Page 1: Wound and Fracture Healing

LOCOMOTOR – Wound & fracture healingWound = “any break in the skin, mucous membrane or organ via a tear/cut/punctureFracture = “a complete or incomplete break in a bone resulting from the application of excessive force”

WOUNDSSequence of changes in wounds:

Coagulation↓Inflammation↓Granulation tissue formation↓Angiogenesis↓Contraction to reduce the size of the wound:fibroblasts myofibroblasts↓Re-epithelialisation↓Arrest of proliferation↓Remodelling

0-24 hours

- Small vessel damage haemorrhage.- Coagulation results in fibrin filling the wound gap.

1-2 days

- Neutrophils migrate acute inflammation- Erythema & swelling- Basal epithelia proliferatn

- Migration of keratinocytes to cover wound- Macrophages infiltrate- Granulation tissue forms

3-4 days

- Vascular granulation tissue fills the space- More fibroblasts & myofibroblasts are recruited- Collagen deposition- Growth factor secretion

5 days

- Temporary type III collagen matrix replaced by type I collagen arranged in bundles to form a scar- Epidermis returns to normal thickness- Inflammation subsides

What effects do growth factors have?- Attract macrophages- Attract fibroblasts- Fibroblast proliferation- Angiogenesis (by VEGF)- Collagen synthesis- Proliferation of epidermisEarly in wound healing = FGFLater in wound healing = TGFβ

After 2 weeks – wound has 50% strength of normal skinAfter 12 months – wound has 80% strength of normal skin

Total blanching of scar takes months/years

Granulation tissue = combination of a rich vascular supply (due to angiogenesis) in which inflammatory cells & fibroblasts are presentKeloid scarring = exaggerated scarring/hypertrophic scar

Removal of dead tissue/regeneration/replacement by new CT/resolution

Page 2: Wound and Fracture Healing

FRACTURESSIMPLE – Intact skin surfaceCOMPOUND – bone fragments breach the skin, and infection risk increasesCOMMINUTED – multiple bone fragments due to >1 breakage siteGREENSTICK – incomplete fractureSTRESS – abnormal stresses applied to bonePATHOLOGICAL – abnormal bone which fractures easily e.g. osteoporosis/bone metastases

Woven bone = disorganised structure/high number of osteocytes/weak.Woven bone is produced when osteoblasts produce osteoid rapidly, which occurs initially in fetal bone but also appears in adults after a fracture or in Paget’s disease.

Lamellar bone = highly organised concentric sheets/low number of osteocytes/strongBoth compact & trabecular (spongy) bone are examples of lamellar bone. After a fracture, woven bone forms initially and is gradually

replaced by lamellar bone during a process known as "bony substitution." Compared to woven bone, lamellar bone formation takes place more slowly.

Endochondral ossification Bone marrow can be found in almost any bone that holds cancellous tissue. In newborns, all such bones are filled exclusively with red marrow, but as the child ages it is mostly replaced by yellow, or fatty marrow. In adults, red marrow is mostly found in the marrow bones of the femur, the ribs, the vertebrae and pelvic bones.

What may impede healing?i) LOCAL FACTORS- Foreign bodies & infections both increase amount & duration of inflammation- Poor immobilisation of wound edges- Arterial & venous vascular supply may be compromised

ii) SYSTEMIC FACTORS- Nutrition: protein/vits A&C/zinc- Steroids: suppression of macrophages entering the wound & reduction in collagen synthesis- Chemotherapy & radiotherapy: reduces number of circulating monocytes

Problems specific to fracturesNon-union

Pseudoarthrosis – a false joint in formed by poorly healed bone ends

Mal-union – ends are soundly united by in the wrong position

Osteomyelitis – infection of the bone

Page 3: Wound and Fracture Healing

1. Reactive phasei) Fracture & inflammatory phase- Soon after fracture, blood vessels constrict- Extravascular blood cells HAEMATOMA FORMATION within fractureii) Granulation tissue formation- Cells within the clot degenerate & die, but fibroblasts survive & replicate GRANULATION TISSUE FORMATION.

2. Reparative phaseiii) Callus formation (IMMOBILSATION IS NECESSARY FOR THIS)Cells of periosteum replicate & transform:Cells proximal to fracture: chondroblasts hyaline cartilageCells distal to fracture: osteoblasts woven bone 2 new tissues grow in size & unit to form the fracture callus.iv) Lamellar bone depositionHyaline cartilage & woven bone is then replaced with lamellar bone. Replacement process = endochondrial ossification (wrt cartilage) or bony substitution (wrt woven bone)1. Collagen tissue of cartilage/woven bone becomes mineralised2. Vascular channels with osteoblasts penetrate mineralised matrix3. Osteoblasts form new lamellar bone upon exposed surface of mineralised matrix4. New lamellar bone = TRABECULAR BONE5. Eventually, all fracture callus is replaced by trabecular bone

3. Remodelling phaseTrabecular bone is replaced with compact bone.The trabecular bone is absorbed by osteoclasts, and compact bone is then deposited by osteoblasts in the Howship’s lacunae (resorption pits).Eventually, callus is remodelled into a new shape which closely replicates the bones original shape & strength