Injury and Healing

Question 1

What are the mechanisms of bone fracture?

Answer 1

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).

Question 2

What is the difference between a stress fracture, a pathological fracture and an insufficiency fracture?

Answer 2

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.

Question 3

Describe mechanism of stress fracture

Answer 3

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.

Question 4

What bones are prone to stress fractures and what activities make it more likely?

Answer 4

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.

Question 5

What are causes of pathological fractures?

Answer 5

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.

Question 6

Where are pathological fractures most common and how are they evaluated?

Answer 6

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.

Question 7

What are 4 types of insufficiency fractures?

Answer 7

Osteopenia and osteoporosis can cause it. Vitamin D deficiency. Congenital osteogenesis imperfecta. Paget’s disease.

Question 8

How do osteopenia and osteoporosis lead to insufficiency fractures?

Answer 8

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.

Question 9

How does a vitamin D deficiency lead to insufficiency fractures?

Answer 9

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.

Question 10

How does congenital osteogenesis imperfecta lead to insufficiency fractures?

Answer 10

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.

Question 11

How does Paget’s disease lead to insufficiency fractures?

Answer 11

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:

1. Osteoclastic Activity
2. Mixed osteoclastic-osteoblastic activity
3. Osteoblastic activity
4. Malignant degeneration

Question 12

What are the two types of tumours?

Answer 12

Blastic is bone forming (prostate) and lytic is bone eating (kidney, thyroid, lung).

Question 13

How are fracture patterns described?

Answer 13

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.

Question 14

What are the different fracture patterns?

Answer 14

Simple or closed, open, transverse, spiral, impacted, greenstick and torus, comminuted (multifragmentary)

Question 15

Explain some fracture patterns

Answer 15

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

Question 16

What are the 3 aetiologies of fractures?

Answer 16

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

Question 17

How is fracture displacement described?

Answer 17

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

Question 18

How can limbs change in length when fractures occur?

Answer 18

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.

Question 19

How is soft tissue integrity evaluated?

Answer 19

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.

Question 20

What is a high energy/low energy fracture?

Answer 20

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.

Question 21

What determines how a fracture heals?

Answer 21

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.

Question 22

What are the 4 general principles of tissue healing and what cells are present at each stage?

Answer 22

Firstly, bleeding (blood). Then inflammation (macrophages and neutrophils). Then, new tissue formation (different blasts). Then, remodelling (macrophages, osteoclasts and blasts).

Question 23

What are the stages of secondary bone healing?

Answer 23

1. Tissue destruction and haematoma formation
2. Inflammation (week 1)
3. Soft callus formation (weeks 2-3)
4. Hard callus formation (weeks 4-12)
5. Remodelling (months to years)

Question 24

Describe what happens in the inflammation phase

Answer 24

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.

Question 25

Describe what happens in the reparative phase

Answer 25

Reparative phase (duration: days-weeks): A thick mass of callus forms around the bone ends, from the fracture haematoma. Bone-forming cells are recruited from several sources to form new bone, which can be seen on radiographs within 7-10 days after injury. Soft callus is organised and remodelled into hard callus over several weeks. Soft callus is plastic and can easily deform or bend if the fracture is not adequately supported. Hard callus is weaker than normal bone but is better able to withstand external forces and equates to the stage of “clinical union”, i.e. the fracture is not tender to palpation or with movement.

Question 26

Describe what happens in the remodelling phase

Answer 26

Remodelling phase (duration: months-years):This is the longest phase and may last for several years. During remodelling, the healed fracture and surrounding callus responds to activity, external forces, functional demands and growth. Bone (external callus) which is no longer needed is removed and the fracture site is smoothed and sculpted until it looks much more normal on an x-ray (Figure 9). The epiphyses gradually realign and residual angulation may be slowly corrected, in accordance with the rules of remodelling.

Question 27

What is primary bone healing?

Answer 27

Intramembranous healing. Occurs when there is absolute stability. Direct to woven bone.

Question 28

What is secondary bone healing?

Answer 28

Endochondral healing. Involves responses in the periosteum and external soft tissues. Occurs when there is relative stability. If endochondral ossification occurs,, more callus formation.

Question 29

How long does a fracture take to heal?

Answer 29

Can take 3-12 weeks depending on location. Healing visible on X-ray from 7-10 days. 
Phalanges: 3 weeks
Metacarpals: 4-6 weeks
Distal radius: 4-6 weeks
Forearm: 8-10 weeks
Tibia: 10 weeks
Femur: 12 weeks

Question 30

What are the general principles of fracture management?

Answer 30

Reduction, Holding and Rehabilitation. Reducing depends on whether fracture is open/closed. Holding can be done with metal/without metal. Rehabilitation involves movement, physiotherapy and use.

Question 31

What are the principles of reduction?

Answer 31

If the fracture is closed, manipulation can be used or traction can be applied. Traction can be applied via skin or skeletal (pins in bone). If the fracture is open, mini-incision or full exposure may be needed.

Question 32

What are the principles of holding?

Answer 32

Fixation required if open. If closed, plaster can be used or traction.

Question 33

What are the types of fixation?

Answer 33

External fixation can be monoplanar or multiplanar. Internal fixation can be intramedullary or extramedullary. Intramedullary involves pins or needles. Extramedullary methods are pins or plates/screws.

Question 34

What are the principles of rehabilitation?

Answer 34

Need to use the bone which may need pain relief and retraining. Movement, strengthening and weight bearing required.

Question 35

What are the types of tendinopathies?

Answer 35

Tendinosis occurs when there is abnormal thickening. Tendinitis is inflammation. Tendon rupture can also occur.

Question 36

How are ligament injuries classified?

Answer 36

Grade I – Slight incomplete tear – no notable joint instability

Grade II – Moderate / Severe Incomplete Tear – Some joint instability. One ligament may be completely torn

Grade III – complete tearing of 1 or more ligaments – Obvious instability. Surgery usually required

Question 37

What are the treatment options for a ligament tear?

Answer 37

Surgical repair may require sutures. Immobilisation can be done with a plaster or boot/brace.

Question 38

What are the effects of immobilization on injured ligamentous tissue?

Answer 38

Less ligament laxity. However, ligament repair scar has less strength and protein degradation exceeds protein synthesis in collage quantity. Blast cells produce inferior tissue. Resorption of bone occurs at site of ligament insertion. Tissue tensile strength 50% in 6-9 weeks.

Question 39

What are the benefits of mobilization (movement) on injured ligamentous tissue?

Answer 39

Ligament scars are wider, stronger, and are more elastic. Better alignment / quality of collagen.

Question 40

What factors affect tissue healing?

Answer 40

1. Mechanical environment - movement and forces.

2. Biological environment - blood supply, immune function, infection and nutrition