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BMSc Orthopaedic Module > Biomechanics - Upper Limb & Spine > Flashcards

Biomechanics - Upper Limb & Spine Flashcards

1
Q

5 parts of the upper limb?

3 main joints?

A

Shoulder girdle, arm, forearm, wrist and hand

Shoulder, elbow and wrist

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2
Q

Articulations in the shoulder joint?

A

Glenohumeral
Acromioclavicular joint
Sternoclavicular joint
Scapulothoracic

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3
Q

Glenohumeral joint bone/cartilage anatomy?

A

Ball and socket joint formed by the humeral head and the glenoid fossa of the scapula. The fossa is shallow allowing for wide ROM, but means it is less stable.

To assist stability, it has a thick cartilaginous rim called the glenoid labrum.

The articulation is surrounded by a capsule and, more importantly, rotator cuff

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4
Q

How does the rotator cuff air in stability?

A

Tendons of supraspinatus, infraspinatus, subscapularis and teres minor form a cuff of tissue, like fingers cupping a ball. They prevent anterior, posterior and inferior by pushing on the humeral head

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5
Q

What forms the AC joint and what type of joint is it?
How is it stabilised?
What restricts ROM?

A

Synovial joint between the proximal acromion of the scapula and distal clavicle.

Stabilised by superior and inferior acromioclavicular ligaments which prevent the joint from being pulled apart.

Further stability provided by 2 parts of the coracoclavicular ligament between the clavicle and coracoid process, which limit upward movement of the clavicle.

ROM restricted by thorax and muscle attachments, being limited to a few degrees during arm abduction

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6
Q

What forms the sternoclavicular joint?

Motion?

A

Synoivial joint between the manubrium and proximal clavicle. It is the only bony joint connecting the shoulder girdle to the trunk.

For first 90 degrees of arm elevation, the clavicle also elevates at 4 degrees for every 10 degrees of arm elevation at the sternoclavicular joint. After this, elevation of the clavicle is almost negligible.

During elevation and depression the clavicle rotates around an axis determined by the attachment of the costoclavicular ligament

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7
Q

What is the scapulothoracic articulation?

What separates it?

A

Bone-muscle-bone articulation between the scapula and posterior thoracic wall - not a true joint but significantly contributes to wide ROM of scapula, which enhances mobility of shoulder.

Broad anterior scapular surface is separated from the thorax by serratus anterior and subscapularis.

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8
Q

Origin, insertion and function of:

  • serratus anterior?
  • subscapularis?
A

Originates on upper 8-9 ribs and inserts on anterior surface of scapula along vertebral border - helps hold scapula to thorax, preventing ‘winging’, and is a strong abductor that is useful in pulling and pushing movements

Subscapularis originates from sub scapular fossa and inserts onto lesser tubercle of humerus. It is one of the rotator cuff muscles and acts to internally rotate the humerus

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9
Q

What is shoulder elevation and depression?

A

Elevation is any movement of the humerus away from the side of the thorax

Depression is movement towards the side of the thorax

Angle is measured between the axis passing through the joint centre parallel to the longitudinal axis of the trunk, and the longitudinal axis of the humerus

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10
Q

Shoulder movements in each plane?

ROM of each?

A

Sagittal:

  • forward flexion: 180ᵒ
  • backward extension: 60ᵒ

Coronal:

  • Abduction: 160ᵒ
  • Adduction: 75ᵒ

Longitudinal axis of humerus:

  • internal rotation: 90ᵒ
  • external rotation: 90ᵒ

Transverse (axial):

  • horizontal flexion: 135ᵒ
  • horizontal extension: 45ᵒ
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11
Q

Most common dislocation of shoulder?

Most common MOI?

A

Anterior dislocation of glenohumeral joint

heavy blows when the shoulder is abducted and extended horizontally

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12
Q

Articulations in the elbow joint, and what forms each?

A

Humeroradial articulation:
Capitellum of distal humerus and head of radius

Humeroulnar articulation:
Trochlea of distal humerus and reciprocally shaped trochlear fossa of proximal ulna

Proximal radioulnar articulation:
Head of radius and radial notch of proximal ulna

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13
Q

Which elbow articulations cause flexion and extension in a hinge-like manner?

A

Humeroradial

Humeroulnar

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14
Q

What is the axis of rotation for elbow flexion and extension?
ROM?

A

It passes through the middle of the trochlea and is roughly parallel to the line joining the medial and lateral epicondyles of the humerus

140 degrees flexion
0 degrees extension

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15
Q

What elbow articulation causes pronation and supination?
How is this achieved?
Axis of movement?

A

Proximal radioulnar

Rotation of the radial head in the radial notch of the ulna in a pivot-like manner. This occurs inside the ligamentous sling which binds the radius to the ulna, the annular ligament.

The longitudinal axis passes through the radial head and distal ulnar articular surface - results in migration of the distal end of the radius around the ulna

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16
Q

ROM pronation and supination?

A

Pronation: 70ᵒ

Supination: 80ᵒ

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17
Q

Stability of the elbow joint? (4)

A

Mechanically stable joint with bony structure and its assoc ligaments and muscles all contributing to its stability

Olecranon process resists forces in anterior and posterior directions, however doesn’t provide resistance against medial and lateral forces

The side-to-side stability is provided by 2 collateral ligaments. The Ulnar (medial) collateral ligament is most important, preventing abduction go the elbow. The lateral collateral ligament only provides limited resistance to adduction forces.

The aconeus muscle has its origin in the lateral epicondyle of the humerus, and inserts in the olecranon and superior portion of ulnar shaft, which aids in lateral stability.

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18
Q

Why are the forces through the elbow commonly 2.5-3x body weight?

A

Large muscle forces are needed to pull the 2 sides of the joint together since the muscles generally have small moment arms

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19
Q

What forms the wrist joint?

A

Distal radius
Carpal bones
Proximal ends of metacarpals
(plus structures in the ulnocarpal space)

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20
Q

8 carpal bones?

A

Proximal row:
Scaphoid
Lunate
Triquetrum (pisiform)

Distal row:
Trapezium
Trapezoid
Capitate
Hamate

The pisiform is located anterior to the triquetrum

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21
Q

What is the only carpal bone easily palpable?

What muscle inserts here and what is its function?

A

Pisiform, as it projects anteriorly at the medial aspect

Flexor carpi ulnaris - flexes and adducts the wrist
(it is a sesamoid bone - similar to patella - pisiform is within tendon and it increases lever arm of muscle)

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22
Q

What forms the radiocarpal joint?
What type of joint is it?
Movements?

A

Distal end of radius, lunate and scaphoid

Condyloid joint - where an oval-shaped condyle fits into an elliptical depression

Flexion/extension; abduction/adduction; circumduction

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23
Q

What makes the wrist stable?

A

Intricate ligamentous structures

Precise opposition of the multifaceted articular surfaces

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24
Q

Describe the articulation between the triquetrum and distal ulna

A

Triquetrum articulates with distal ulna via a triangular shaped inter-articular disc which occupies the ulnocarpal space. This is attached to the styloid process of the ulna at its apex, and to the ulnar notch of the radius at its base.

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25
Q

Wrist flexion/extension ROM?

How does this occur?

A

Flexion: 80ᵒ-90ᵒ
Extension: 70ᵒ-80ᵒ

Flexion: first 60% occurs at the mid-carpal joints, the next 40% at the radoiocarpal

Extension: first 67% at radoiocarpal joint and final 33% at mid-carpal joints

26
Q

Wrist abd/add-uction ROM?

A

Abduction: 15ᵒ-20ᵒ

Adduction: 35ᵒ

27
Q

Wrist ROM required for ADL’s?

A

10ᵒ flexion to 35ᵒ extension.

For immobilised wrists, fixing at 15ᵒ extension allows most ADL’s to be performed to a satisfactory level

28
Q

What bones form the hand?

A

5 metacarpals and 14 phalanges on each hand

29
Q

5 joints of the hand?

A 
CMC
intermetacarpal
MCP
PIP
DIP
30
Q

What forms the CMC joints?
What is the most important one and why?
What type of joint is it?

A

The carpals and metacarpals

The first CMC joint, between the trapezium and first metacarpal, as it is the most freely moving one and allows opposition of the thumb and fingers.

It is a saddle joint, with he articulating surfaces resembling reciprocally shaped saddles, which allows the first metacarpal to flex, extend, adduct and abduct. The remaining CMC joints are essentially modified saddle joints

31
Q

What are the inter metacarpal joints?

A

Irreglar articulations between the proximal ends of adjacent metacarpals. They share joint capsules with the CMC joints

32
Q

Features of the MCP joints?

A

Condyloid joints formed by the rounded the rounded distal heads of the metacarpals and the concave proximal ends of the phalanges.

Each joint is enclosed in a capsule and stabilised by strong collateral ligaments. The MCP of the thumb is strengthened by an additional dorsal ligament

33
Q

ROM metacarpals?

A

2nd and 3rd immboile
4th - 10ᵒ-15ᵒ flexion/extension
5th - 20ᵒ-30ᵒ flexion/extension

34
Q

ROM MCP joints?

A

90ᵒ flexion
Extension varies considerably

Also allows abd/add-uction

35
Q

ROM PIP/DIP joints?

A

PIP: 100ᵒ-110ᵒ flexion

DIP: 90ᵒ

Hyperextension varies widely among individuals

36
Q

ROM thumb MCP joint?

A

Varies 30ᵒ-90ᵒ flexion

15ᵒ extension (greater than the others)

37
Q

What is thumb flexion and extension?
ROM thumb CMC joint?
Movements involved in thumb touching base of 5th finger?
Then if it moves to tough tip?

A

Thumb flexion = thumb moving across palm

Thumb extension = thumb away from side of palm

Around 15ᵒ flexion and 20ᵒ extension is possible.

Thumb abduction = 60ᵒ

A small amount of rotation is possible

If thumb opposes 5th finger base this is achieved by flexion and rotation of CMC joint, with MCP and PIP/DIP flexion

Moving to touch the tip, abduction is required

38
Q

Origin and insertions of flexor digitorum profundus?

A

Originates from anterior aspect of ulna

Inserts on distal phalanges, allowing it to flex the DIP joints

39
Q

How does changing wrist position alter the function of the forearm muscles controlling wrist and hand movement?

A

Changing wrist position alters the functional lengths of the muscle tendons that cross it.

e.g. if the wrist is neutral it is easy to clench fist, but if the wrist is flexed first it is not so easy

Similarly, if the wrist is straight you can flex to roughly 90ᵒ, but if in a fist already, it is impossible to do so

40
Q

How many fused and unfused vertebrae are there?

A

24 unfused, then sacrum (5) and coccyx (4) giving 33 vertebrae in total

41
Q

Describe the structure of a vertebra?

A

All unfused vertebrae, except C1 and C2, resemble each other.

They have:

  • a flat, round vertebral body anteriorly and centrally
  • an arch of bone called the neural arch which forms the spinal foramen through which the spinal cord passes
  • a spinous process projecting inferiorly in the posterior midline
  • 2 transverse processes projecting laterally
42
Q

vertebral articulations?

A

Each vertebra articulates with each adjacent vertebra at 3 points:

  • main one: intervertebral disc
  • other 2: synovial facet joints positioned on either side of the arch

(upper facets articulate with lower facets of the vertebra above and vice versa)

43
Q

2 roles of the intervertebral discs?

2 main parts of intervertebral disc?

A
  • Bearing and distributing loads
  • Restraining excess movement

Inner nucleus pulposus and outer annulus fibrosus

44
Q

Where is nucleus pulposus found?

What is it composed of?

A

In centre of all discs, except lumbar where it is slightly posterior

Formed by strongly hydrophilic gel enmeshed in a random collagen matrix

45
Q

Mechanism by which the nucleus pulposus absorbs load?

A

The hydrophilic gel produces a high water content and an elevated nucleus pressure, which balances the applied compressive stress.

If stress increases then water is drive out until a new steady state is reached. Likewise if the load decreases then the disc rehydrates.

However, this mechanism is not capable of maintaining a constant level of hydration over a long period of time - the reduction results in decreased disc height, which is evident from loss of standing height at the end of the day, as much as 1cm

46
Q

Composition of the annulus fibrosus?

A

Composed of collagen fibres in concentric layers (lamellae) with alternating orientations of fibres - this results in high bending and torsional load

47
Q

Describe anatomy of C1 and C2?

A

The atlas (C1) has no body but is composed of a ring within which an oval fossa articulates with the axis (C2)

The axis has an articular process, the Dens, which protrudes superiorly from the vertebral body.

A small synovial joint is formed between the anterior tip of the dens and the oval fossa of the atlas

The atlas rotates around the dens, but the motion is restricted by several ligaments that are attached to the top of the dens

48
Q

Anatomy of the thoracic spine?

ROM?

A

Each vertebra is attached to a pair of ribs.

The head of each rib articulates with its corresponding vertebral body, and the rib tubercle articulates with the transverse process of the same vertebra.

Ribs 2-9 also articulate with the vertebra above, which allows the chest to move up and down during breathing.

The ribs give added rigidity to the thoracic spine, which effectively limits its mobility to a few degrees of flexion, extension and rotation

49
Q

What is different about the lumbar spine?

A

They are subject to much greater loads than the rest of the spine, so their bodies are larger

50
Q

What are the sacrum and coccyx?

Articulations of the sacrum?

A

The sacrum is a triangular-shaped bone that has resulted from the fusion of 5 separate vertebrae

The coccyx is a single bone that has resulted from the fusion of 4 vertebrae

The junction between the sacrum and lumbar spine is very mobile.
The sacrum is joined to the ilium (2 innominate bones) on either side by 2 fibrous joints, that allow only a small amount of relative motion

51
Q

2 factors which can affect ROM of spine?

A

Age - In old age, ROM is roughly half that of in youth. Also sex.

52
Q

How does flexion-extension vary throughout the spine?

A

It is greatest in the C spine , with 21ᵒ between C4-5

It is smallest in the thoracic spine, with 3ᵒ between T9-10

The max amount of flexion and max extension also varies between adjacent segments, where in the lumbar spine max flexion is 10ᵒ and max extension is 4ᵒ

53
Q

What movements occur during bending over?

A

The first 50ᵒ-60ᵒ of flexion occur in the lumbar spine - any additional flexion is achieved by tilting the pelvis

54
Q

How does lateral flexion vary throughout the spine?

A

It follows a similar pattern to flexion-extension, where it is maximal in C spine and minimal in thoracic.

Notable, there is no lateral flexion between C1 and C2, and no rotation between C1 and the occipital bone

55
Q

How does rotation vary throughout the spine?

A

Generally decreases down the spine

Notably, there is much larger range of rotation between C1/C2 than any other vertebrae, because of their unique structures

56
Q

Does standing with arms folded against a wall and twisting back give accurate measure of spinal rotation?

A

No, because pelvis and lower limb will move also if standing

For accurate test, must be seated to stabilise pelvis

57
Q

What mainly causes loadings on the spine?

Why is lower back pain thought to be prevalent?

A

Weight go the upper body, muscle activity and externally applied loads.

Bad posture during sitting or standing, and bad lifting technique

58
Q

From least to most, rank the following in terms of load imposed on the lumbar spine:
erect standing, bent-forward standing, erect sitting, relaxed sitting, prone

A

Prone (25%)

Erect standing (100%)

Erect sitting (140%)

Bent-forward standing (150%)

Relaxed sitting (175%)

(percentage of normal load)

59
Q

Why does leaning/bending forward increase load on lumbar spine?

A

In relation to the lumbar spine, the wright is more anterior due to the upper body being more forward and the pelvis tilting backward.

This increases the Flexion moment arm between the spine and the weight.

This can be counterbalanced by an extension moment arm, with the force coming from the posterior back muscles, however this distance is constant, the the force produced by the muscles must be greater in order to counteract the greater flexion moment arm

The increase in force produced by the muscles creates a greater compressive load on the spine

(even during erect sitting, the moment arm is larger than in erect standing, increasing load on lumbar spine)

60
Q

How does poor lifting technique risk lower back pain?

A

Load on the lumbar spine is in accordance with the moment arms from upper body weight and the object being lifted

Therefore, if bent over with straight legs, the moment arm will be much larger than if bending knees and keeping back straight

BMSc Orthopaedic Module (14 decks)

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