Approach to Fracture Repair PDF 2024 (University of Surrey)

APPROACH TO FRACTURES ALISON LIVESEY NOVEMBER 2024  LEARNING OBJECTIVES By the end of this session you should be able to: Describe normal bone structure and development Classify fractures according to type, location and nature Explain the terms primary and secondary bone healing...

APPROACH TO FRACTURES ALISON LIVESEY NOVEMBER 2024  LEARNING OBJECTIVES By the end of this session you should be able to: Describe normal bone structure and development Classify fractures according to type, location and nature Explain the terms primary and secondary bone healing Discuss the principles of fracture repair Identify delayed unions, non unions and malunions Fracture Repair 2024 2  BONE STRUCTURE Bone is composed of: Cells Osteoblasts – make bone Osteocytes – bone cells Osteoclasts – resorb bone Organic matrix (1/3 mass) Collagen fibres and proteoglycans Mineral (2/3 mass) Calcium phosphate -as hydroxyapatite Fracture Repair 2024 3  BONE STRUCTURE Long bones epiphysis/physis/metaphysis/diaphysis Short bones cuboidal bones – carpus/tarsus Sesamoid bones usually in or adjacent to a tendon protect tendons increase mechanical efficiency of tendon unit Flat bones skull/scapula protective function Irregular bones vertebrae Non-flat bones of skull (zygomatic arch) Fracture Repair 2024 4  BONE FUNCTION Axial skeleton: skull and hyoid apparatus vertebral column ribs and sternum Appendicular skeleton: thoracic limb pelvic limb Heterotopic skeleton: os penis Fracture Repair 2024 5  BONE DEVELOPMENT Initially during development – woven bone – immature bone Gradually replaced by more organised -lamellar bone – mature bone Lamellar bone Two types: Hard compact cortical bone (shafts of long bones) - made up of osteons Spongy or cancellous bone (ends of long bones, inner layer of long bones, vertebrae) -made up of trabeculae Fracture Repair 2024 6 BONE DEVELOPMENT Fracture Repair 2024 7 BONE DEVELOPMENT Derived from a condensation of mesenchymal cells 2 distinct mechanisms: 1. Intramembranous ossification Formation of bone directly from osteogenic mesenchyme cells - most flat bones - periosteal cells increase width of long bones 2. Endochondral ossification Formation of bone from a cartilage precursor − formation of vertebrae, ribs, sternebrae and pelvis − formation of long bones and primary means of growth of long bones − prominences on long bones may have separate centres of ossification Fracture Repair 2024 8  BONE DEVELOPMENT INTRAMEMBRANOUS O S S I F I C AT I O N Osteoblasts - produce extracellular matrix Formation of a number of primary ossification centres Osteoblasts become encased in matrix - transform into osteocytes Woven bone formed - loosely organized and rapidly made Additional osteoblasts and osteocytes arrive and reorganise to lamellar bone Fracture Repair 2024 9  BONE DEVELOPMENT: ENDOCHONDRAL OSSIFICATION Starts with formation of a cartilage template Cartilage template replaced by the coordinated activity of mesenchymal stem cells, chondrocytes, osteoblasts, osteoclasts, and endothelial cells Fracture Repair 2024 10  BONE DEVELOPMENT Endochondral ossification Chondrocytes form columns with: Primary centre 1. Resting or reserve zone at the epiphyseal end (contains normal hyaline cartilage) 2. Zone of proliferation where they multiply 3. Zone of hypertrophy and calcification where they get bigger and the matrix begins to mineralise 4. Zone of cartilage erosion where the matrix is removed by chondroclasts and blood vessels invade 5. Zone of endochondral ossification where bone replaces the removed cartilage and bone elongation Fracture Repair 2024 11 #universityofsurrey occurs 12 BONE DEVELOPMENT Endochondral Ossification Secondary centres Separate ossification centres arise in the epiphyseal areas. These centres allow the joint cartilage and bone to be shaped locally They have separate blood supply which does not cross the growth plate. Fracture Repair 2024 12  REMODELLING I F Y O U D O N ’ T U S E I T , Y O U ’ L L L O S E I T Wolff’s law - bone responds to the loads placed upon it.. Bone and cartilage need to see load to remain healthy When bone is subjected to stress- electric currents are induced - Piezoelectric effect electropositivity on convex surface – osteoclastic activity electronegativity on concave surface – osteoblastic activity Trabecular struts or plates will form in orientation with the largest applied forces Fracture Repair 2024 13 Bone Fractures Fracture Repair 2024 14  DIAGNOSIS Imaging Radiography – orthogonal views important History CT Trauma MRI Ultrasound Usually sudden onset Scintigraphy Signs Injury Pain Swelling Altered gait, lameness Crepitus Neurological dysfunction Shock/pallor Fracture Repair 2024 15  WHEN DOES A BONE BREAK If the energy delivered to bone is greater than the energy that it can absorb, fracture will occur. Ability to absorb energy (toughness) varies with the direction that load is applied ( compressing, rotating, bending, distracting) Rate of loading will influence fracture patterns. KE = ½ x mass x velocity2 – high velocity injuries deliver a lot of energy to the bone – the bone absorbs the energy and then releases this upon fracture Larger the energy transfer the greater structural damage caused Fracture Repair 2024 16  BIOMECHANICS OF FRACTURE REPAIR Different forces produce different fractures: Compression/shearing......oblique fracture Distraction/tension………..transverse fracture Bending………………………...transverse fracture Torsion………………………….spiral fracture Multidirectional……………..comminuted fracture NB often a combination of forces Fracture Repair 2024 17 TYPES OF FRACTURE What causes load delivered to exceed load that can be absorbed? Monotonic fracture Supramaximal loading of a bone that ultimately leads to failure Pathological Fracture A bone that is weakened by a pathological process such as neoplasia, osteoporosis or osteomyelitis. Stress Fracture If the rate of accumulation of fatigue damage surpasses the body’s ability to remodel it may become weakened to the point of fracture Fracture Repair 2024 18  C L A S S I F I C AT I O N O F F R A C T U R E S Historically: Simple (closed)vs Compound (open) Classified according to Location Displacement Direction of fracture line Type of fragment Number of fracture lines Stability after anatomical reconstruction Open or closed Complicated- major blood vessel, nerve or joint involvement Fracture Repair 2024 19 C L A S S I F I C AT I O N : LO C AT I O N General Articular Epiphyseal Physeal Metaphyseal Diaphyseal Special Condylar Trochanteric Fracture Repair 2024 20 C L A S S I F I C AT I O N : LO C AT I O N P H Y S E A L Fracture Repair 2024 21 CLASSIFICATION : LOCATION PHYSEAL Type IV Type V Fracture Repair 2024 22 C L A S S I F I C AT I O N : D I S P L A C E M E N T Greenstick Incomplete fracture in juveniles. Periosteum is largely or completely intact Folded Form of greenstick - resembles a folded cardboard tube Fissure Undisplaced fragments which could displace under stress Depressed Fragments invade underlying cavity Compression Cancellous bone, e.g vertebral body; or involving subchondral bone Impacted One fragment driven into cancellous bone of opposing fragment Complete Cortex is broken with separation of fragments Incomplete Part of bone remains intact Fracture Repair 2024 23 CLASSIFICATION : DIRECTION Avulsion (tensile) Transverse Spiral ( bending/tensile) (torsion) Oblique (>30o to transverse) (shear/compression) Fracture Repair 2024 24  CLASSIFICATION : NUMBER OF FRACTURE LINES Multiple: fractures at >1 level or >1 bones Comminuted: more than 2 fragments - minimal, moderate, severe Polish Journal of Veterinary Sciences Fracture Repair 2024 25  CLASSIFICATION : STABILITY Stable after reduction – tend to remain in place without force, so may be treatable by coaptation Unstable after reduction – the fracture collapses as soon as the reducing forces are removed; these may require operative stabilization Fracture Repair 2024 26  CLASSIFICATION : OPEN vs CLOSED Type I The Gustilo-Anderson open fracture classification system is a commonly used classification system for open fractures. © Vetarian Key The amount of energy, the extent of soft-tissue injury Type IIIB and the extent of contamination determine fracture severity. Classified I, II, IIIA, IIIB, IIIC © Vetarian Key Progression from grade 1 to 3C implies a higher degree of energy involved in the injury, higher soft tissue and bone damage and higher potential for complications (a score of grade 3C implies vascular injury as well as bone and connective-tissue damage) Fracture Repair 2024 27 Bone Healing Fracture Repair 2024 28  BONE HEALING: INDIRECT(CALLUS FORMATION) Inflammatory phase haemorrhage – haematoma neutrophils /macrophages growth factors Reparative phase granulation tissue vascularisation collagen fibres – soft callus (chondrogenesis) gradual mineralisation – hard callus (endochondral ossification) bone union achieved Remodelling phase woven bone above replaced by lamellar bone Fracture Repair 2024 29 31  BONE HEALING: D I R E C T H E A L I N G Direct bone healing - Primary bone union Occurs under rigid fixation – no callus formation Gap healing (bone ends < 0.8mm) Fracture gap fills with primary bone No connective tissue or cartilage prior to bone Orientation of new bone is transverse to long axis Gradually get remodelling in second phase Contact healing (bone ends 2% Fibrocartilage is strains of >15% Granulation tissues can tolerate almost 100% Primary Secondary Requires absolute stability Increases in stability during healing Minimises strain at fracture Strain induction high:strain tolerance high Healing is slow Tolerance gradually decreases as fracture stabilises Risk of metal fatigue/failure Once strain