BONE PATHOLOGY Flashcards
BONE REMODELING: def of bone homeostasis, steps + def of each + duration of each
Life long process of bone remodelling to maintain density, chemical composition & shape of bone
Activation of osteoclasts: Happens by osteoblasts stimulating conversion of haemopoietic stem cells to osteoclasts - Happens when osteoblast sense area old bone tissue that require resorption
- Resorption happen before bone formation - Mediated by cytokines
Bone resorption: Osteoclasts dissolve bone mineral & break down bone matrix
- Minerals derived from resorption (most calcium & phosphate) released into blood
Reversals of bone resorption: Period between cessation of bone resorption & beginning of bone formation
- Osteoclasts undergo programmed cell death
Bone formation: - Osteoblasts lay down layers of bone matrix
- Mineralisation of new bone matrix by addition of calcium & phosphate completes bone formation phase
Step 1-2-3 = 2 to 3 weeks
Step 4 = 3-4 months
Characteristics of healthy mature bone, if imbalance
Balance between formation & resorption, formation longer time than resorption
If imbalance = nb disease such as osteoarthritis & Paget’s disease
Osteoclast: def & characteristics
= multi nucleated cells derived from haemopoietic stem cells -> larger than osteocytes
Few osteoclasts in normal bone
- occupy pits in bone matrix
- tend to concentrate in areas of areas requiring resorption
- present in blood for easy transportation to areas of old bone tissue requiring resorption
Osteoblast: def & characteristics
= only 1 nucleus per cells & formed from mesenchymal stem cells
Many osteoblasts in normal bone
- needed to begin 1st phase of remodeling because only ones recognizing old bone tissue & start process to replace it with new bone tissue
- when osteoblasts become osteocytes, also become trapped within bone matrix & stop forming new bone
- function of osteocyte: maintain structure of bone by their inter connective dendritic network & act as surfaces for osteoblasts to travel on during bone remodeling
FRACTURE: def, classification, ≠ types & def of each
D: = breaking of bone in to 2 or + fragments
C: 1. Environmental exposure
2. Mechanism of injury
3. By number & orientation of fragments
- Simple fracture = minimal damage to other tissues around fracture fragments. Fragments not exposed to external environment, no joint involvement Compound fracture = extensive damage to soft tissue around fracture fragment. Fragments exposed to environment with high risk of infection
- Stress fracture = common in endurance runners & soldiers who march long distances. Bone breaks as result of repetitive loading
Pathological fracture = break in bone already weakened by primary disease. Resulting in pathological fractures include osteoporosis, osteomalacia & bone cancer
Sudden trauma = caused by roads traffic accidents, domestic accidents such as fall down stairs, domestic violence, assault & industrial accidents - Comminuted fracture = fracture with + 2 fragments
Segmental fracture = happen when one bones broken in at least 2 places, leaving segment of bone totally separated by breaks
Butterfly fracture = 2 oblique fracture lines meeting to create large triangular fragment located between proximal & distal fracture fragments
Transverse fracture = bone broken perpendicular to its length Oblique fracture = bone broken at angle
Spiral fracture = bone broken with twisting motion
GREENSTICK FRACTURE: def & characteristics
= special type of fracture
- Most common on children & very rare in adults because children’s bones are softer & more able to bend than adult’s bone - Most common in long bone as tibia, femur or humerus but can happen in any bone of body
- Cortex & periosteum on 1 side of bone broken while other side only bent but not broken
- Angulation at fracture side not severe => usually treated by immobilization with cast or removable splint for few weeks
FRACTURE: diagnosis
- Most used diagnostic tool for fractures = X-ray
- Sometimes, X-ray not detect fracture such as scaphoid fracture
- Fracture not detectable on plain X-ray = occult fracture
- MRI & ultrasound scan detect occult fractures
- Other examples of occult fracture = paediatric supracondylar humeral fracture & fracture of head of radius in adults
- On clinical examination, fracture site swollen, bruise & deformed
FRACTURE HEALING: ≠ phases & characteristics of each
Fractures can heal in 2 ways
a) Primary union:
- Rarely happens
- Requires fragments to be undisplaced & held together by rigid immobilization - Healing by medullary callus formation
- Callus size small because it does not involve periosteum
b) Secondary union:
- Fracture healing in most fractures
- Callus larger & stronger because involves both medullary & periosteal callus formation
1. Inflammation
- Haematoma: immediately after bone breaks, bleeding in space between fracture fragments - Inflammation
- Clotted haematoma forms fibrin rich granulation tissue which acts as template for soft callus formation
2. Soft callus
- Mesenchymal cells derived from bone marrow & periosteum differentiate into osteopenia cells (osteoblasts)
- Osteoblasts infiltrate granulation tissue to secrete matrix composed of collagen I & II to form soft callus (= fibrocartilage) & unite fragments
3. Hard callus
- Angiogenesis = infiltration of soft callus by new blood vessels
- Osteoclasts perform resorption of soft callus to allow new bone formation
- New bone formation by osteoblasts replace soft callus with lamella bone (hard callus) - Lamella bone form Haversian system around new blood vessels
4. Remodeling
- Homeostasis of bone
Duration of healing of: clavicle, humerus, radius, ulna, ribs, femur, tibia, metacarpals & metatarsals
Clavicle 6-8 weeks
Humerus’s shaft 8-12 weeks
Radius’s shaft 6-8 weeks
Ulna 6-8 weeks
Ribs 2-4 weeks
Metacarpals 2-4 weeks
Femur 3-6 months
Tibia 6-12 weeks
Metatarsals 4-6 weeks
Intra articular fractures
- Involves joint surface
- Fracture are within joint & extends to articulating surface of 1 or more bones forming joint
- Articular cartilage & other articular tissues also damaged
- Difficult to manage because of involvement of joints
- Open reduction & fixation (by internal & external fixation) required for most intra articular fractures to achieve anatomical reduction of joint surface
- Risk of 2nd osteoarthritis after intra articular fracture as high as 2000% compared to normal joints
Complications of fracture: ≠ types & def of each
NON-UNION
- Time that has elapsed since fracture happened is longer than maximum time period for that fracture to heal & there is no evidence of soft callus formation on X-ray. This means that there is no attempt at healing. Keep in mind that ≠ bones heal at ≠ time durations for ≠ age groups
- Include infection, too much gap between fracture fragments & malnutrition which caused by limited blood supply to fracture fragments
MAL-UNION
= misalignment of fracture fragments. Fracture actually goes through all 4 stages of healing normally, but fracture fragments are angulated or bone becomes shorter after healing or bone twisted at fracture site
- Caused by improper treatment of fracture to achieve normal alignment or by inadequate immobilization of fracture fragments
INFECTIONS
= complication of fracture that can easily lead to death
- More common in compound fractures but can also happen in simple fractures
INJURY TO NON-SKELETAL TISSUE
- Fracture fragments have sharp jagged edges
- Cause injury to nerves, viscera & blood vessels at time fracture happened or later if fragments unstable & limb not immobilized
PSEUDOARTHROSIS
= formation of false joint at fracture side - type of fracture non union
THROMBO-EMBOLISM
- Thrombose = clotting of blood within blood vessel but blood clot attached to wall of blood vessel. When blood clot detached from wall of blood vessel, it becomes embolus
- Embolus = move along with blood flow to areas of body distal to blood vessel that is too small for size of embolus to pass
- Cause other diseases such as stroke of embolus blocks capillary in lungs
- Blockage of blood vessel that is too small by embolus = INFARCTION
- Apart from embolus derived from bubbles which can be trapped within blood vessel after rib fracture & fat embolus which can happen when fat from bone marrow into circulation after fracture
PRINCIPLE OF FRACTURE MANAGEMENT: 3 ≠ principles & def of each
Fractures heal better when proximal & distal fragments close together & aligned. Perfect alignment not always possible
- Closed reduction: simple uncomplicated fractures reduced by manipulation with analgesia or under anaesthesia
- Open reduction: surgical exposure of fracture fragments to reduce fracture to as perfect alignment as possible
Immobilization = required to allow fracture fragments stay in apposition long enough for callus to form, prevent excess mvts at fracture site. Some mvt between fragments promotes healing but overt mvt delay union or cause non-union & pseudoarthrosis
- Conventional splinting using Plaster of Paris (POP) or same thing such as resin cast. Also, proprietary braces for splinting fractures on market
- External fixation: with devices such. As frames, pins, clamps & rods
- Internal fixation: with plates, screws, wires & intramedullary rods & nails
Rehabilitation = restoration of patient to normal preinjury function
- Walking with partial weight bearing in case of LL fractures to full weight bearing
FACTORS AFFECTING HEALING & WHAT THEY AFFECT
Too much gap between fracture fragments & multiple fragments: Non-union / delayed union
Infections: Non-union
Inadequate immobilization - mvts at fracture site: Mal union - pseudoarthrosis
Inadequate reduction - angulation, overlap, twist at fracture site: Mal union - pseudoarthrosis
Malnutrition = diet or reduced blood supply: Non-union
Radiation therapy or over exposure to X-rays: Non-union / delayed union
Therapeutic pulsed ultrasound & electrical muscle stimulation: Promotes healing, reduces healing
Early mvt - partial or non weight bearing. Mvt of joint prox & distal to fracture site as soon as it’s safe to do: Promotes healing, reduces healing
Medication: Delays healing, increases healing time
SPINAL FRACTURES: def, treatment, diagnosis, signs & symptoms
D: Vertebral fractures caused by trauma or by pathology
- Traumatic vertebral fractures more common among males - Pathological vertebral fractures mostly due to osteoporosis, caused by osteomalacia & bone cancer
T: Mechanical ventilation
- Spinal decompression surgery - Spinal bracing
- Continuous Spinal traction
- 24h postural management
- PT specific to level of injury
D: - X-ray
- CT scan
- Whole body MRI
S&S: - Spinal shock
- Breathing difficulty
- Paralysis below injury level - Incontinence
- Temperature dysregulation - Pain
- Dysphonia
1st aid in suspected spinal fractures
- Do not move victim
- Do not tilt victim’s head back
- Do not remove any article of clothing from victim
- Put towels on both sides of head or hold head steady
- If need to roll victim, one person holds head while another person log roll victim
