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Ortho Implant technology > Unit 5: Upper Limb Joint Replacement > Flashcards

Unit 5: Upper Limb Joint Replacement Flashcards

1
Q

Which upper limb joints may be replaced?

A

shoulder
elbow
wrist
finger

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2
Q

After pain-relief, what does upper limb replacement aim to achieve?

A

restoration of hand function

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3
Q

What conditions do patients undergoing upper limb replacement suffer from?

A 
rheumatoid arthritis
osteoarthritis
osteonecrosis
post-traumatic arthritis
fracture
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4
Q

In what order are spine, upper limb and lower limb replacements carried out in a patient with rheumatoid arthritis?

A

spine and lower limb before upper limb

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5
Q

Why are spinal surgeries prioritised over upper limb in a patient with rheumatoid arthritis?

A

cervical spine instability may damage the spine and cause neurological symptoms

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6
Q

Why are lower limb replacements prioritised over upper limb in a patient with rheumatoid arthritis?

A

it lessens the need for upper body to support the body weight which may compromise survival of an upper limb replacement

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7
Q

If several joints in the upper limb are diseased, how is priority given?

A

most painful

distal to proximal

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8
Q

Why are the distal joints restored first in the upper limb?

A

to restore hand function
distal joints may compromise proximal joint rehab
more functional improvement

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9
Q

Why do some surgeons prioritise shoulder over elbow replacement ?

A

shoulder pain radiates to elbow
immobilised shoulder loads elbow which may cause prosthesis to fail
rehab of elbow is easier with a pain-free shoulder

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10
Q

What materials are upper limb replacements made from?

A 
stainless steel
titanium and titanium alloys
cobalt chrome alloys
vitallium alloy
HDP
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11
Q

What material is used to fixate upper limb replacements?

A

PMMA bone cement

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12
Q

Which type of shoulder replacement gives worse results?

A

hemi-arthroplasty

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13
Q

In what order do upper limb replacements last?

A

shoulder is best
elbow
wrist + fingers are worst

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14
Q

What material works well in flexible hand and wrist replacements?

A

silicone elastomer

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15
Q

Can a general orthopaedic surgeon perform upper limb replacement? why?

A

no

small dimensions + complex

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16
Q

Why does a non-specialist orthopaedic surgeon struggle with shoulder replacement?

A

balancing soft-tissue and inadequate scapula bone stock

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17
Q

List the three categories of shoulder prosthesis that are based on movement constraint and give an example of each

A

unconstrained eg neer
semiconstrained eg gristina
constrained eg michael reese

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18
Q

What is the stability of an unconstrained shoulder replacement dependent on?

A

intact, functional rotator cuff

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19
Q

What material is used to construct the glenoid component of a Neer type shoulder prosthesis

A

polyethylene

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20
Q

Why is it important not to remove soft-tissue attachments when fitting a shoulder joint replacement?

A

they provide stability

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21
Q

How could an unconstrained design be converted to a semi- constrained design

A

addition of a hooded glenoid component

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22
Q

What are the disadvantages of a semiconstrained design compared to an unconstrained design?

A

limited motion means that a greater force is transmitted to the bone-cement interface of the glenoid component which can cause it to loosen

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23
Q

What does a hooded glenoid component do?

A

resists the upward shear force when elevating the arm to prevent subluxation ( if weak rotator cuff) and avoid tearing supraspinatus tendon

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24
Q

What design is predominantly used for constrained total shoulder replacements?

A

ball in socket

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25
Q

What is unusual about the Trispherical total shoulder replacement?

A

it has three balls instead of one

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26
Q

Why is glenoid component fixation important?

A

as the scapula has a small amount of bone so it is hard to fix to it

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27
Q

What type of glenoid fixation does the Neer prosthesis have?

A

keel

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28
Q

Do unconstrained or constrained designs need more elaborate glenoid fixation? Why?

A

constrained due to larger loads

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29
Q

In a total shoulder arthroplasty is the humeral or glenoid component more likely to loosen ?

A

the glenoid component

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30
Q

What is the function of the shoulder joint?

A

to position the hand in space

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31
Q

If someone has good rotator cuff function which shoulder replacement would be appropriate?

A

unconstrained

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32
Q

If someone has poor rotator cuff function which shoulder replacement would be appropriate?

A

constrained

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33
Q

Name the 3 synovial joints of the shoulder

A

the glenohumeral, the acromio- clavicular, and the sternoclavicular

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34
Q

Name the other articulation of the shoulder

A

scapulothoracic bone-on-muscle-on-bone articulation

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35
Q

What is the most important articulation of the shoulder?

A

glenohumeral

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36
Q

What bony feature of the glenohumeral joint is important in determining its range of motion and stability?

A

shallow glenoid fossa gives good ROM but low stability

37
Q

What are the 2 primary aims of an elbow prosthesis?

A

to relieve pain and provide stability

38
Q

What are 3 functions of the elbow?

A

position hand
allow forearm to act as lever
can be weight-bearing

39
Q

What are the 3 articulations of the elbow?

A

humeroradial
humeroulnar
proximal radioulnar

40
Q

What is the most important articulation of the elbow for supporting the load?

A

humeroulnar

41
Q

In full extension, what is the angle of the forearm?

A

10-15 degrees valgus

42
Q

What 2 things provide elbow stability?

A
  1. congruent joint surface

2. soft tissues

43
Q

Which soft tissues are particularly important for elbow stability?

A

anterior joint capsule
medial collateral ligament (50% of joint stability in flexion)
lateral collateral ligament

44
Q

Which structure is loaded if the radial head is removed?

A

medial collateral ligament

45
Q

What relevance does a stiff shoulder have to the prosthetic replacement of the elbow?

A

A stiff shoulder increases the loads placed on the bone-cement interface of a prosthetic replacement of the elbow when the patient internally or externally rotates their upper arm. Ultimately this may cause the prosthesis to loosen.

46
Q

What are the two main problems with uniaxial hinged elbow prostheses?

A

loosening and loss of bone stock.

47
Q

Why do uniaxial hinged elbow prostheses loosen?

A

fixed coronal plane means that there are excessive shearing forces at the bone-cement interface

48
Q

In the early metal-on-metal hinged elbow prosthesis designed by Dee, what was a contributory factor to loosening?

A

The high amount of metal wear debris from the metal-on-metal articulations was also a contributory factor to loosening.

49
Q

How do semiconstrained elbow prostheses differ from the first generation of hinged elbow prostheses?

A

they have “sloppy” hinges with varying degrees of side-to-side laxity

50
Q

When would a semiconstrained elbow prosthesis be used over an unconstrained elbow prosthesis?

A

soft tissue insufficiency or loss of bone stock

51
Q

What is an unconstrained elbow prosthesis?

A

resurfaces the lower end of humerus and ulnar articulating surface

52
Q

What is required for an unconstrained elbow prosthesis?

A

intact collateral ligaments for stability

53
Q

Does semicostrained or unconstrained have higher rates of

a) dislocation?
b) loosening?

A

a) unconstrained

b) semiconstrained

54
Q

What benefit may be gained from resurfacing the radial head?

A

additional load-transmission stability can be

gained.

55
Q

What are the two types of wrist joint replacement?

A

flexible hinge

total wrist

56
Q

What procedure is preferred, if disease only affects the radiocarpal joint?

A

arthrodesis

57
Q

What is the function of the distal radio-ulnar joint?

A

pronation/supination

58
Q

Which wrist movement is most important?

A

extension

59
Q

Where does the axis of rotation of wrist pass through ?

A

capitate

60
Q

How does the radiocarpal joint contribute to wrist motion?

A

large ROM during flexion/extension

stability during abduction/adduction

61
Q

Which property of the radiocarpal joint can prosthesis not replicate?

A

stability during abduction/adduction as it is a condyloid joint replaces with a ball-in-socket

62
Q

What is a flexible hinge prosthesis used in combination with?

A

resection arthroplasty

63
Q

Describe a flexible hinge prosthesis

A

proximal and distal stem with a barrel-shaped misdsection, slides in and out of medullary canal of radius and 3rd metacarpal

64
Q

What is a flexible hinge prosthesis made of?

A

silicone elastomer

65
Q

What percentage of flexible wrist prostheses have been found to tear on the sharp bony edges of the medullary canal?

A

20%

66
Q

Which design feature prevents flexible wrist prostheses from tearing?

A

titanium bone liners (grommits)

67
Q

What are the two main types of total wrist replacement?

A

Meuli and Voltz

68
Q

What design is the meuli total wrist?

A

ball and socket with 2 pronged distal and radial pronged

69
Q

What prevents rotatory motion in the meuli total wrist?

A

soft tissue balance

70
Q

Which normal wrist articulation does the Voltz prosthesis resemble?

A

radiocarpal joint: increased abduction/adduction

71
Q

What components make up the voltz total wrist?

A

single stem metacarpal component
polyethylene cup
single stem radial component

72
Q

What are the main problems associated with total wrist prosthesis?

A

loosening and stress-shielding of the distal radius.

73
Q

Which hand joint is most frequently replaced?

A

MCP

74
Q

What are the two types of MCP replacement?

A

flexible hinge

total

75
Q

What are the main indications for MCP replacement?

A

pain and deformity due to RA

impaired function due to soft tissue imbalance

76
Q

What MCP procedure would be carried out in a younger patient requiring a strong pinch?

A

arthrodesis

77
Q

What type of joint is the MCP?

A

condyloid

78
Q

What hand movement is the MCP important for?

A

80% of finger flexion

79
Q

How is a flexible hinge MCP replacement stabilised?

A

new capsuloligamentous sttructure forms

80
Q

Why is it beneficial to have a sliding flexible hinge MCP replacement ?

A

even force transmission

increased ROM

81
Q

How are the grommets, used with flexible hinge prostheses, fixed in position?

A

press fit

82
Q

Is flexible hinge or total MCP replacement more successful?

A

flexible hinge but this may not be suitable for a younger patient who has greater requirements

83
Q

List the three problems associated with total MCP replacements.

A

implant fracture, implant migration, implant loosening.

84
Q

What are the main indications for interphalangeal joint replacement?

A

pain and deformity associated with rheumatoid arthritis, degenerative arthritis and post-traumatic arthritis

85
Q

Is arthrodesis or implant arthroplasty a more reliable procedure in the interphalangeal joints?

A

arthrodesis as the joint contributes little to the overall motion

86
Q

What type of joints are the interphalangeal?

A

bicondyloid between proximal and distal phalanx

87
Q

What stabilises the interphalangeal joints?

A

bony articulation itself and the surrounding soft tissues (joint capsule, collateral ligaments, the fibrocartilaginous palmar plate and muscle tendons).

88
Q

Functionally which is the most important interphalangeal joint?

A

proximal as it has 85% overall motion

89
Q

Which implant arthroplasty has satisfactory results in the interphalangeal joints?

A

flexible hinge

Ortho Implant technology (7 decks)

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