Injury and Healing Flashcards
What are the mechanisms of bone fracture?
A fracture is a break in the structural continuity of a bone. Can be caused by trauma (high energy or low energy), stress fracture (abnormal stresses on normal bone) and pathological causes (normal stresses on abnormal bone).
What is the difference between a stress fracture, a pathological fracture and an insufficiency fracture?
A stress fracture is caused by injury or repetitive stress. A pathological fracture is caused by some abnormal weakening of the bones and an insufficiency fracture is a form of pathological fracture caused by a deficiency underlying the abnormal weakening.
Describe mechanism of stress fracture
Overuse of the muscles and bones leads to stress being placed on bone being greater than the bone’s capacity to remodel. Hence, bone weakens and a stress fracture occurs.
What bones are prone to stress fractures and what activities make it more likely?
Weight-bearing bones such as femur, tibia, metatarsals and navicular are vulnerable. Athletes and people in occupations requiring high physical activity such as military particularly prone.
What are causes of pathological fractures?
Classified as local or general. Local abnormalities include infection and cancer (can be benign, primary malignant or metastatic). General causes can be osteoporosis, metabolic bone disease, Paget’s disease, osteogenesis imperfecta, osteomyelitis or Vitamin D deficiency.
Where are pathological fractures most common and how are they evaluated?
Pathological fractures most common in thoracic spine and lumbar spine and corticocancellous junctions of bone (proximal end of femur). Mirel’s score = quantify risk of impending pathological fracture in malignant lesion. Evaluates based on site, size, nature and pain.
What are 4 types of insufficiency fractures?
Osteopenia and osteoporosis can cause it. Vitamin D deficiency. Congenital osteogenesis imperfecta. Paget’s disease.
How do osteopenia and osteoporosis lead to insufficiency fractures?
When osteoclast activity exceeds that of osteoblast activity, microarchitecture is disrupted. Affects females more than males in a 4:1 ratio. Postmenopausal osteoporosis most common in women 50-70 while senile osteoporosis affects people over 70. Secondary osteoporosis affects people of any age but more men (60%). Can be caused by hypogonadism, glucocorticoid excess and alchoholism. It is associated with fragility fractures most common in hips, spine and wrist. Low energy trauma can also lead to a fracture.
How does a vitamin D deficiency lead to insufficiency fractures?
Vitamin D facilitates calcium, magnesium and phosphate absorption. Vitamin D gained from diet or synthesized from the sun. Inadequate Calcium or Phosphate leads to defect in osteoid matrix mineralization. In children, known as rickets. Once physis fused and stops growing, known as osteomalacia.
How does congenital osteogenesis imperfecta lead to insufficiency fractures?
This is a hereditary condition that can be autosomal recessive or dominant. Type I collagen is decreased due to decreased secretion or production of abnormal collagen. Hence, there is insufficient osteoid production. This affects bones, hearing, heart and sight.
How does Paget’s disease lead to insufficiency fractures?
There are both genetic and acquired factors which influence. Excessive bone breakdown and disorganised remodelling lead to deformity, pain, fracture or arthritis. This may transform into a malignant disease. Four stages of disease:
- Osteoclastic Activity
- Mixed osteoclastic-osteoblastic activity
- Osteoblastic activity
- Malignant degeneration
What are the two types of tumours?
Blastic is bone forming (prostate) and lytic is bone eating (kidney, thyroid, lung).
How are fracture patterns described?
Described in terms of soft tissue integrity, bony fragments and movement. Alternative classification system includes: aetiology, fracture displacement, change in length, relationship with external environment, complexity of treatment and quantum of force causing fracture.
What are the different fracture patterns?
Simple or closed, open, transverse, spiral, impacted, greenstick and torus, comminuted (multifragmentary)
Explain some fracture patterns
Transverse fracture - perpendicular to long axis of bone caused by application of bending force
Oblique fracture - forms acute angle with long axis of bone as bending force had a longitudinal component
Spiral fracture - fracture line runs spirally in more than one plane caused by a rotational force
Comminuted fracture - multiple fragments formed from high energy injury
Segmental fracture - two fractures in same bone at diff places leading to free segments in between
Impacted fracture - caused by a high impact compression of bone
Avulsion fracture - caused by explosive muscular contraction or violent joint movements and caused by traction from ligament, tendon or a capsular insertion
What are the 3 aetiologies of fractures?
Traumatic fracture - fracture of bone following abnormal excessive force on a normal healthy bone
Pathological fracture - normal force on an abnormally weak bone. Pathology may be restricted to one area (tumour deposit) or be generalised due to osteoporosis/osteomalacia
Stress/Fatigue fracture - Cyclical application of normal forces in excessive frequency to the normal bone of a healthy patient leading to break in bony trabeculae
How is fracture displacement described?
Undisplaced - a complete fracture but no movement from anatomical position
Minimally displaced fracture - no significant displacement but slight movement
Displaced fracture - displacement of the distal fragment from the proximal fragment
Described in terms of change in length, angulation, rotation and translation
How can limbs change in length when fractures occur?
Apposition is the amount of end-to-end contact of fracture fragments. Bayonet apposition = overlap of fracture fragments in longitudinal axis so bones have no contact as they have slipped past each other. Known as off-ended. Leads to shortening of limb length. Distraction is when the bones move further away from one another leading to limb lengthening.
How is soft tissue integrity evaluated?
Closed fracture is one that is not communicating with external environment e.g. overlying skin/soft tissue
Open means communicating with external environment so soft tissue and skin affected.
What is a high energy/low energy fracture?
High energy fracture - caused by trauma and associated with severe soft tissue damage and extensive devascularization. Usually complex and such fractures are unstable + slow to heal.
Low energy fracture - mild trauma force and little associated soft tissue injury.
What determines how a fracture heals?
Amount of movement at site of fracture. If movement is present, there is relative stability (2-10% strain) and secondary healing via intermediate stages occurs.
If there is no movement, then there is absolute stability and compression (<2% strain) and primary healing where direct healing with bone occurs, will take place.
What are the 4 general principles of tissue healing and what cells are present at each stage?
Firstly, bleeding (blood). Then inflammation (macrophages and neutrophils). Then, new tissue formation (different blasts). Then, remodelling (macrophages, osteoclasts and blasts).
What are the stages of secondary bone healing?
- Tissue destruction and haematoma formation
- Inflammation (week 1)
- Soft callus formation (weeks 2-3)
- Hard callus formation (weeks 4-12)
- Remodelling (months to years)
Describe what happens in the inflammation phase
Inflammatory phase (duration: hours–days):Broken bones result in torn blood vessels and the formation of haematoma. The inflammatory reaction results in the release of cytokines, growth factors and prostaglandins, all of which are important in healing. The fracture haematoma becomes organised and is then infiltrated by fibrovascular tissue, which forms a matrix for bone formation and primary callus.
