PHTH1110 002 Fracture Healing - Wright.pdf

BONE STRUCTURE & FRACTURE HEALING Dr Dean Everett Wright 2019 Bone consists of Living cells embedded in mineralized organic matrix collagen calcium hydroxyapatite & other calcium phosphates content = function Inorganic content give RIGIDITY lack …. SOFT bone organic lack content give ELASTICITY …. B...

BONE STRUCTURE & FRACTURE HEALING Dr Dean Everett Wright 2019 Bone consists of Living cells embedded in mineralized organic matrix collagen calcium hydroxyapatite & other calcium phosphates content = function Inorganic content give RIGIDITY lack …. SOFT bone organic lack content give ELASTICITY …. BRITTLE bone content = function Inorganic lack content give RIGIDITY …. SOFT bone organic content give ELASTICITY lack …. BRITTLE bone Bone Cells Bone function x 6 support movement protection haematopoiesis store minerals and fat endocrine regulation BONE TYPES Long bones strength/ support structure/ mobility body weight metaphysis ends of diaphysis maximum blood supply physis cartilage growth Cortical. Compact. Lamellar Spongy. Cancellous. Trabecular WOVEN BONE Woven or Fibrous bone haphazard organization of collagen fibers and is mechanically weak. seen at sites *fracture *tendon healing and ligament attachment *pathological conditions Developmental Classification membranous cartilaginous bones BONE FORMATION INTRAMEMBRANOUS (PRIMARY) ENDOCHONDRAL (SECONDARY) Fracture Break in bone or periosteum Fracture Healing Bony bridge forms strong enough for functional needs BEGINS WHEN: IMMEDIATELY many years continues Fracture Healing Bony bridge forms strong enough for functional needs BEGINS WHEN: IMMEDIATELY many years continues end result BONE mineralised mesenchymal tissue end result BONE mineralised mesenchymal tissue Fracture Healing Bony bridge forms strong enough for functional needs BEGINS WHEN: IMMEDIATELY years continues many stages Inflammation Bleeding Haematoma Haemopoeitic stem cells Growth factors Fibroblasts Mesenchymal cells Osteoprogenitor cells Granulation tissue Osteoblasts from osteogenic precursor cells and / fibroblasts proliferate Repair 1° Callus within 2/52 Bridging (soft) Callus if space Replaced by enchondral ossification by woven bone (hard callus) Slower forming medullary callus Type II collagen, then Type 1 collagen expression in unstable # patterns Primary bone healing with no callus Remodelling Begins during middle of repair phase Continues for up to 7 years According to Wolff’s Law based on stresses #healing is complete when there is repopulation of the marrow space Repair Haematoma replaced by callus Fibroblasts, chondroblasts, osteoblasts ; with their matrices Endochondral ossification in centre, direct generation of woven bone from cambium layer of periosteumintrammbranous ossification Repair Exact interaction of Fibroblastic growth factor factors poorly understood stimulates angiogenesis Role of cytokines: Transforming growth factor β initiates chondroblast and osteoblast formation Transforming growth factor β also stimulates enchondral classification Repair Early fracture callus Intramemebranous and woven bone formation – Consists of indicated by high glycosaminoglycans and type II and III collagen concentrations of Alkaline phsphatase, Type I collage Transformation to hyaline and osteocalcin and fibrocartilage – Cartilage specific proteoglycans and type II collagen become more abundant Remodelling Continuous process of Haversian remodelling Osteoclastic resorption, possibly guided by electrical or mechanical strain fields remove extraneous peripheral bone An example of Wolff’s Law Factors in fracture healing Age Comorbidity Blood supply Nicotine NSAIDs Nutrition Vascular injury Soft tissue envelope Functional Level Soft tissue Nerve Function Hormones attachments to bone Stability Growth Factors Site/location Sterility Energy Local pathology eg Bone Loss Ca Type of bone Bone loss Primary Bone Healing Temporary acceleration of Haversian remodelling Only occurs with rigid fixation No callus Lag period Osteoclast Jumping Distance Bone metabolising units – Linear resorption rate of 50 microns per day – X-section 200 microns – Walls of osteon lined by osteoblasts – Circumferentially appose new osteoid at 1 micron per day – New osteon (3mm long x 90 microns wall thickness) will take 3-4 months Primary Bone Healing Fixation methods and mode of healing examples of … Low intensity ultrasound pulsed low-energy ultrasound used for 20 mins daily may enhance fracture healing, via enhanced angiogenesis and the induction of IL8, basic FGF and VEGF Reports say healing time reduced by up to 38%