bones and fractures

• bone tissue

  • Osteology is the study of bone
  • Osseous tissue (bone tissue) is a connective tissue whose matrix is composed of water, protein fibers and mineral salts (mainly calcium carbonate and hydroxyapatite). These salts give bones its hardness.
  • Collagen are proteins that make up the fibers which enables bone to resist being stretched or torn apart.
  • This is known as the tensile strength and without collagen bones would be hard and brittle
• composition of bone tissue

  • Osteoprogenitor cells - these are stem cells derived from mesenchyme (connective tissue found in the embryo) they have the ability to become osteoblasts
  • Osteoblasts - secretes collagen and other organic components to form bones
  • Osteocytes - mature bone cells that maintain the daily activities of the bone
  • Osteoclasts - cells found on the surface of bones and they destroy or reabsorb bone tissue
• spongy bone

  • Also known as cancellous or trabecular bone
  • Makes up the inner portion of the bone
  • It is light, porous, and is made up of small, needle-like pieces of bone arranged like a honeycomb
  • It is responsible for the flexibility and weight distribution shifts that can withstand multidirectional forces
  • It houses the bone marrow that allows for RBC formation
  • found in the ends of long bones, carpals, tarsals, pelvic/innominate bones, vertebrae, ribs, skull, shoulder blades
• compact bone

  • Also known as cortical bone
  • It forms the outer layer of most bones
  • It is dense, hard and heavy tissue which makes up most of the bone’s weight
  • It provides strength and protection, insulation, movement frameworks and ideal for resisting compressive forces
  • It is made up of units called osteons or Haversian systems
  • Can be found in shafts of femur, fibula and tibia
• periosteum


  rich nerve and blood supply = whacking shin on bed = lump, excruciating pain etc 
• sharpey's fibers


  are tufts of collagen fibers which adhere the periosteum to the bone and in areas where there are ligamentous/tendon attachment these fibers are more densely packed
• endosteum


  lines the medullary cavity and contains osteogenic cells as does the periosteum = these are stems cells which can change when stimulated to differentiate into other cells such as osteoblasts – these are the whose role it is to secrete and build bone matrix and are responsible for bone growth/osteocytes = these guys are mature bone cells and responsible for the formation the structure of the bone itself, finally osteoclasts = these guys break down and reabsorb bon
• bone function

  • Support
  • Protection (e.g. skull encloses brain)
  • Movement - muscles use bones as levers
  • Mineral storage calcium, phosphate and fat storage
  • Blood cell production in bone marrow

  Interrelationship with other body systems eg think about bone as protecting the lungs ie ribs, a rib fracture could potentially damage the lung tissue too = pneumothorax for example
• What is the process through which most bones are formed?

  Ossification
• When does the process of ossification begin during embryonic life?


  During the 6th and 7th week
• What is intramembranous ossification?


  Bone forms on or within loose, fibrous connective tissue membranes without a cartilage stage
• What is endochondral ossification?


  Bone forms in hyaline cartilage produced by cells and chondroblasts
• What is the most common type of cartilage in the body?

  Hyaline cartilage
• Where can hyaline cartilage be found in the body?


  In the ends of bones that form joints, between the ribs, nasal passages, larynx, and trachea
• What are the main components of hyaline cartilage?


  Chondrocytes and an extracellular matrix (ECM) made mostly of collagen, proteoglycans, and water
• Why is hyaline cartilage difficult to repair once damaged?


  It is avascular and has limited cell replication potential
• What are the key differences between intramembranous and endochondral ossification?


  • Intramembranous ossification:
  • Bone forms directly in connective tissue
  • No cartilage stage
  • Endochondral ossification:
  • Bone forms in hyaline cartilage
  • Involves a cartilage stage before bone formation
• fracture


  an interruption in the continuity of the bone
• causes of fractures

  • Trauma
  • Pathological factors e.g Paget’s disease, osteoporosis, carcinoma, osteomyelitis, osteogenesis imperfecta or brittle bone disease
• clinical features of fractures

  • Pain
  • Deformity 
  • Oedema
  • Muscle spasm 
  • Abnormal movement
  • Crepitus
  • Loss of function
  • Hypovolemic shock
  • Limitation of joint movement
  • Muscle atrophy
• hypovolemic shock


  is an emergency condition in which severe blood or other fluid loss makes the heart unable to pump enough blood to the body. This type of shock can cause many organs to stop working.
• muscle atrophy


  is the wasting or thinning of muscle mass. It can be caused by disuse of your muscles or neurogenic conditions. Symptoms include a decrease in muscle mass, one limb being smaller than the other, and numbness, weakness and tingling in your limbs
• fracture healing

  • Haematoma formation and inflammation (inflammatory cells appear in the haematoma)
  • Callus formation (woven bone/spongy bone formation)
  • Consolidation (lamellar bone formation - solid union of fracture)
  • Remodelling
• inflamation and haematoma formation


  The initial response to a fracture, involving the release of chemical mediators and recruitment of inflammatory cells. This stage lasts 24–48 hours and prevents infection. Blood vessels crossing the fracture line are broken = periosteum, osteons, Haversian systems medullary cavity​. Blood leaks out and forms a clot​ - hematoma formation. Swelling and inflammation and blood capillaries grow into the blood clot​ to prevent bleeding. Phagocytes and osteoclasts cells start to remove the dead tissue – several; weeks
• fibrocartilaginous callus


  fragile not bone. The capillary growth supplies blood which helps to organize the clot and the haematoma into granulation tissue called callus​. Then fibroblasts and osteogenic cells from the periosteum and the endosteum invade the callus and work with osteoblasts to make fibrocartilage​. Eventually a mass of repair tissue called the fibrocartilaginous callus bridges the gap across the fracture site​, this remains for 3 weeks​
• bony callus formation


   this is when osteoblast activity ramps up and begin to produce spongy bone and eventually all the fibrocartilaginous callus is formed into spongy bone then the callus is referred to as a bony callus
• remodelling


  tidy up and refining stage where any remaining dead tissue continue to be reabsorbed by osteoclasts; compact bone replaces spongy bone
• what suggests complete fracture healing

  • Absence of pain on weight-bearing, lifting or movement
  • No tenderness on palpitation at the fracture site
  • Blurring or disappearance of the # line on the x-ray
  • Full or near full functional ability
• What type of bone heals more quickly, cancellous or compact bone?


  Cancellous (spongy) bone
• How long does it typically take for upper limb (UL) bone to unite?


  1. 12 weeks
• How long does it typically take for lower limb (LL) bone to unite?


  12-18 weeks
• What is the role of revascularization in fracture healing?


  It restores blood supply to devitalized bone and soft tissue adjacent to the fracture site
• How does the mechanical environment of a fracture influence healing?


  A more disrupted soft tissue environment leads to slower healing
• What effect does loss of bone apposition have on fracture healing?


  It affects the healing process negatively
• Which area of the tibia is notoriously slow to heal?


  The lower third of the tibia
• What is the impact of vascular injury on fracture healing?


  It disrupts blood supply, hindering healing
• What are two complications of fractures?

  Pulmonary embolism and deep vein thrombosis
• What factors influence the healing of a fracture?

  Bone type, fracture type, patient’s age, treatment, nutritional status, and comorbidities
• What can hypovolemic shock result from in the case of a femoral shaft fracture?


  It may bleed 3 pints
• How does adequate fixation affect fracture healing?


  It prevents impairment of blood supply and maintains reduction