Implant Technology Unit 6a Flashcards

Question

what is the time frame for most long bone fractures to heal via secondary healing

Answer 1

6 to 12 weeks [metaphyseal (cancellous bone) # heal in a slightly shorter period]

Answer 2

if movement is inhibited early in the healing process

Answer 3

bony union will not take place may be described as an “atrophic” or fibrous union

Answer 4

cartilage rather than bone cells is laid down if there is a lot of movement a false joint (or pseudoarthrosis) may form between rapidly proliferating cartilage cells at either end - gives what is called an "elephant foot" appearance

Answer 5

If there is no relative movement (or micromovement) taking place between fracture fragments during the healing process, the fracture heals without external callus formation new Haversian systems grow directly across the fracture gap.

Answer 6

primary is quicker however, bone does not quickly recover its original strength therefore, fracture fixation devices that promote secondary bone healing have been preferred in recent years

Answer 7

increases in bone density and thickness of cortical bone, therefore increasing its strength and stiffness [Wolff's law]

Answer 8

the large callus cross-sectional area at the fracture site significantly increases its second moment of area. This gives structural support that compensates for the lower strength and rigidity of the material of the callus

Answer 9

R = EI ``` E = young's modulus I = second moment of area ```

Answer 10

by low Young's Modulus being compensated for by a higher value of I

Answer 11

with the increase of strength and stiffness of the callus, its cross sectional area decreases until bone regains its original shape

Answer 12

loading bone along its long axis

Answer 13

piezoelectric effects - Electrical effects caused by moving crystals of hydroxyapatite, which are the basic mineral constituents of bone. Hydroxyapatite is known to be piezoelectric, that is it develops an electric charge when loaded. hormonal factors - hormone "substance P" found to be produced at fracture sites electromagnetic effects - Electro-magnetic effects produced through electron flow away from the fracture site

Answer 14

In primary bone healing, a fracture heals without a callus.

Answer 15

save life treat pain restore function

Answer 16

femoral - 1 litre blood loss pelvis - 3 litres blood loss wrist - only few millilitres blood loss

Answer 17

opiates splintage - reduces the muscle spasm which are very painful

Answer 18

- reduction - holding - bone fracture fixation

Answer 19

closed reduction - manipulation of the fracture fragments open (surgical) reduction - fracture site opened by surgical op and fracture fragments restored to alignment directly

Answer 20

internal fixation

Answer 21

external fixation internal fixation

Answer 22

plaster of paris [and its derivatives] traction external fixator

Answer 23

plates and screws pins and wires rods and nails

Answer 24

After fracture, bone has lost its continuity as a rigid link to support the body and to facilitate muscle action and body movement To restore this continuity, it is essential to regain relative stability between fracture fragments, since excessive movement would result in non-union.

Answer 25

minimise deformation (or movement) between fracture fragments

Answer 26

stabilises a fracture through the soft tissue help the injured limb to resist bending forces after reduction are of little use in resisting torsional and compression forces can only be used for relatively stable fractures

Answer 27

treated non-surgically

Answer 28

- by dissolving calcium sulphate hemihydrate in an organic solvent, such as ether, which contains no water. - Starch is added to this mixture and the whole paste is spread on a cotton bandage. - wet bandage is then dried and the solvent collected for re-use. - The bandage is therefore coated with calcium sulphate ‘held on’ by starch.

Answer 29

cotton bandages, hard coated with crystals of calcium sulphate hemihydrate bandage adds little to the strength but provides a vehicle for getting the wet plaster on the part to be splinted consists of cotton thread which may be double woven to prevent it fraying (known as leno cloth)

Answer 30

the starch - called an accelerator - speeds up the chemical reaction also the temp of the water

Answer 31

materials that slow down the setting of POP cast examples - alum and borax

Answer 32

considerable heat production when calcium sulphate hemihydrate mixed with water need to make sure it isn't gonna hurt the patient

Answer 33

long crystals - sharp - called alabaster - give cast hard quality smaller crystals - give cast softer feel properties of the material of the final splint are largely dependent on the physical interlocking of the 2 types of crystals

Answer 34

1 - By encasing the limb in a rigid exoskeleton it provides support to the soft tissues which in turn support the broken bone. This so called hydraulic theory has been well proven. 2 - By moulding the cast against the fracture it is possible to obtain a gentle three point fixation system, giving a so-called periosteal hinge. [Most casts work by a combination of both methods and the 1st probably predominates in most situations except in childhood when the tough periosteum provides a gentle hinge about which fulcrum a three point mould can be achieved]

Answer 35

1 - length i.e. prevent shortening 2 - position i.e. prevent tilt and shift in anterior/posterior and medio/lateral planes 3 - rotation i.e. about the long axis of the bone

Answer 36

by incorporating the whole of the broken bone and limb segment in the cast including the joint i.e. above knee cast, below knee cast, cylinder

Answer 37

- if casting is prolonged, the encased joints become stiff and their muscle waste through disuse - prolongs overall rehabilitation - impairment caused by immobilisation of joints may lead to disability sufficient to induce dependency and prolong the stay in hospital - especially for elderly patients.

Answer 38

- careful moulding | - application of hinges incorporated into the cast i.e. known as functional or cast bracing

Answer 39

the upper third of the femoral component is gently squared off so that the soft tissues are slightly distorted but not sufficiently to raise high points of pressure knee is freed by the use of hinges which permit the knee to move normally the position of the broken fragments are held reduced whilst the joints move normally and the muscles can rehabilitate early.

Answer 40

achieves rotatory control through moulding around the upper third of the tibia and by extensions to the cast which encaptures the femoral condyles in knee flexion.

Answer 41

so the soft tissue injuries have settled down and there is no swelling

Answer 42

adjustable | always need to be in contact with skin

Answer 43

isoprene rubbers (or polycarprolactone sheets) and glass fibre artificial fibre and polyurethane composites

Answer 44

become ductile at fairly low temperatures, so that whilst warm they can be moulded directly onto the skin achieving a reciprocal shape to the limb When at room temperature they become firm, but remain flexible enough to be gently adjustable, retaining a “memory” of their formed shape.

Answer 45

expensive - require purchase of an oven require a lot of skill

Answer 46

woven bandages made of glass fibre or fabric which is impregnated with a urethane monomer and a catalyst

Answer 47

When exposed to warmth and moisture, forms a true fibre/polyurethane composite which is very light and extremely strong, yet flexible

Answer 48

1 - forming braces when they are applied to a reasonably stable, healing fracture as they can form very sophisticated shapes and interface well with hinge materials, ensuring a firm anchorage. 2 - make excellent secondary casts once swelling has settled and the soft tissues confer a degree of stability to a fractured limb. [They are not very useful as a primary splintage material as they are conforming rather than being very mouldable and are difficult to use on unstable and swollen limbs.]

Answer 49

cheap easy to obtain easy to apply very versatile

Answer 50

Reducing a fracture And Holding a fracture

Answer 51

altering muscle tone in order to maintain a position achieved at reduction.

Answer 52

10N per 100N of BW must be countered by an equal force otherwise patient would be pulled out of the bed counter force achieved by tilting the bed backwards

Answer 53

skin traction skeletal traction

Answer 54

load is applied via a foam or sticky bandage applied to the skin. The attachment to the limb is dependent on the adhesiveness of the bandage or the frictional resistance of the foam. This method, although convenient, can only be used for loads up to 50 N as otherwise there is a very real danger of injuring the skin.

Answer 55

load is applied via a pin inserted through the bone. can be used to apply large loads and has advantage that the load can be precisely relative to the long axis of the bone - this is important when traction is being used in dynamic situations. Disadvantage of skeletal traction is the risk of bone infection at the pin bone interface [can be countered by careful pin insertion and good pin site care by nursing staff]

Answer 56

static (fixed) traction dynamic traction balanced traction

Answer 57

load is applied to the limb and attached to a splint so that the splint itself provides the counter force Thomas splint

Answer 58

mainly used for treating children’s fractures because they do not cope well with complicated traction and their fractures heal quickly.

Answer 59

acceptable for a week or two but the immobility prevents joint movement, does not induce axial movement at the fracture site and leads to muscle disuse

Answer 60

same principles apply as in static traction but the patient is encouraged to use their joints and the load is arranged so that, irrespective of limb position, the net pull is maintained along the axis of the bone achieved through PULLEYS

Answer 61

1 - they alter the direction of the force by being statically mounted on a surrounding bed frame 2 - they may alter the magnitude of the traction force by being mounted on the limb or “free floating” within the traction cord system.

Answer 62

useful when the physiotherapist wants to counter the weight of a limb segment so that very weak muscles can be exercised without the full weight of the limb early in treatment.

Answer 63

used as a supplement to either static or dynamic traction used to offset pressure effects caused by splints i.e. used for Thomas splints where a counter force is applied to the groin

Answer 64

by applying a small load to the splint as a whole which tends to draw the pressure off the groin area

Answer 65

[problems associated with having to lie in bed for long periods of time] ``` bed sores chest infection UTI atrophy of muscles and bones [need active physio program] ```

Answer 66

requires long period of hospitalisation

Answer 67

bones are in reasonable apposition subjected to axially orientated [not shearing] loads little bit of movement

Answer 68

the patient the injury the facilities available the skill of the operator

Answer 69

age - elderly have more co-morbities - children, bones heal more rapidly and have more capacity to naturally remodel their shape after fracture health - co-morbidites - functional requirements

Answer 70

- weeks 0-2 haematoma is invaded by macrophages in surrounding tissue which are responsible for “mopping up” dead and damaged tissue. The haematoma and dead cells are absorbed into the macrophages.

Answer 71

- weeks 2-6 New capillaries grow into the fracture haematoma bringing with them cells of healing and repair including fibroblasts, which form fibrin (scar tissue) and also other cells including bone forming osteoblasts. At the same time the surviving periosteum begins to regenerate and grow between the bone fragments

Answer 72

- weeks 6-12 New bone tissue is laid down in the endosteal space from the residual living bone and eventually the two ends are reunited as a ball of “provisional callus” which appears as a dense area on an X-ray.

Answer 73

- up to about 12 months | provisional callus continues to form woven bone which gradually remodels to form a cortex.

Answer 74

- up to 2 years callus matures so that the trabecular pattern is reformed and the bone remodels to accommodate the stresses that the bone experiences in that anatomical region.

Implant Technology Unit 6a Flashcards

(98 cards)