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BMSc Biomechanics > Unit 4 - Biomechanics of the upper limb & spine > Flashcards

Unit 4 - Biomechanics of the upper limb & spine Flashcards

1
Q

What 2 bones make up shoulder girdle?

A

Clavicle & scapula

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2
Q

What 4 articulations make up the shoulder joint & what type of articulations are they?

A 
3 synovial:
  - glenohumeral
  - acromioclavicular
  - sternoclavicular
1 bone-on-muscle-on-bone joint:
  - scapulothroacic
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3
Q

What type of joint is the glenohumeral?

A

Ball (humeral head) & socket (glenoid fossa of scapula)

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4
Q

What structures aid stability of the glenohumeral joint?

A

Glenoid labrum (thick cartilagenous rim)
Capsule
Rotator cuff

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5
Q

What muscles make up the rotator cuff & what is its function?

A

Muscles:

  • Subscapularis
  • Infraspinatus
  • Supraspinatus
  • Teres minor

Pushes on humeral head, providing dynamic restraints to anterior, posterior & inferior displacement

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6
Q

What structures stabilise the AC joint?

A

Superior & inferior AC ligaments which prevent joint being pulled apart

2 parts of the coracoclavicular ligament which limits movement of clavical

RoM limited to a few degrees during arm abduction (restricted by thorax & muscle attachments)

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7
Q

How much does the clavicle elevate during arm elevation?

A

~4 degrees for every 10 of arm elevation (for first 90 of arm elevation - past 90 clavicle elevation is negligible)

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8
Q

Why does the clavicle rotate?

A

During arm elevation/depression clavicle rotates about longitudinal axis due to attachment of costoclavicular ligament

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9
Q

Why is the scapulothoracic articulation not a true joint?

A

No direct bony/ligamentus connections

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10
Q

What 2 muscles separate scapula from posterior thorax?

A

Serratus anterior:

  • originates on upper 8/9 ribs & inserts on anterior surface of scapula along vertebral boarder
  • helps hold scapula against thorax (preventing winging) & is a strong abductor (for pulling/pushing)

Subscapularis:

  • originates from subscapular fossa & inserts on lesser tubercle of humerus
  • medially rotates humerus
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11
Q

What is the range of motion of the shoulder in the sagittal plane?

A

Forward flexion - 180

Backward extension - 60

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12
Q

What is the range of motion of the shoulder in the coronal plane?

A

Abduction - 180

Adduction - 75

Internal rotation - 90

External rotation - 90

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13
Q

What is the range of motion of the shoulder in the transverse plane?

A

Horizontal flexion - 135

Horizontal extension - 45

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14
Q

What is the most common type of shoulder dislocation?

A

Anterior dislocation of glenohumeral joint

Heavy blow when arm abducted & extended. If blow too heavy/muscles too weak –> dislocation

Arm & shoulder acting as 1st class lever with resistance to dislocation at a disadvantage

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15
Q

What 3 articulations make up the elbow joint?

A

Humeroradial

Humeroulnar

Proximal radioulnar

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16
Q

How much extension & flexion are possible at the elbow?

A

Extension - 0
Flexion - 140 (40 between arm & forearm when fully flexed)

Humeroradial/ulnar articulations allow hinge movement - axis of rotation through middle of trochlea

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17
Q

What articulation in the elbow allows for pronation & supination?

Describe hoe it comes about

A

Proximal radioulnar

Rotation of radial head in radial notch of unla in pivot-like manner (occurs in annular ligament - ligamentous sling wich binds through radius to ulna)

Longitudinal axis passes through radial head & distal unla articular surface - rotation about this axis results in migration of distal radius around ulna

18
Q

What is the max RoM for pronation & supination of forearm?

A

Pronation - 70

Supination - 80

19
Q

How is stability achieved at the elbow?

A

Olecranon process holding trochlea like a spanner & nut (for anterior-posterior stability)

2 collateral ligaments:

  • medial (ulnar): most important, preventing abduction
  • lateral: provides limited resistance to adduction. Aided by anconeus muscle located on lateral aspect of elbow (weakness doesn’t cause problem as valgus stability more important)
20
Q

What bones make up the carpals?

A 
Scaphoid
Lunate 
Triquetrum
Pisiform
Trapezium
Trapezoid
Capitate
Hamate
21
Q

What is the function of the pisifrom?

A

Is the insertion point of flexor carpi ulnaris (flexes & adducts wrist)

Increases lever arm of flexor carpi ulnaris - decreasing the force required from the muscle

22
Q

What articulations are involved in the wrist?

A

Radiocarpal
Midcarpal
Carpometacarpal
Intercarpal

23
Q

Describe the radiocarpal joint

A

Condyloid joint - oval shaped condyle of radius fits into eliptical depression between lunate & scaphoid

Allows flexion, extension, abduction, adduction & circumduction

24
Q

Describe the range of motion at the wrist

A

Flexion: 80-90 (40% at radiocarpal & 60% at midcarpal)

Extension: 70-80 (67% at radiocarpal & 33% at midcarpal). Most critical movement

Abduction: 15-20

Adduction: 35

25
Q

What articulations are found in the hand?

A 
Carpometacarpal
Intermetacarpal
Metacarpophalangeal
Proximal interphalangeal
Distal interphalangeal
26
Q

Describe 1st carpometacarpal joint

A

Saddle joint between trapezium & 1st metacarpal at base of thumb

Most freely moving CMC joint & allows thumb to oppose fingers giving great dexterity

All CMC joints surrounded by joint capsule & reinforced by ligaments

27
Q

Describe intermetacarpal joints

A

Irregular articulations formed by prox ends of adjacent metacarpals

Share joint capsules of CMC joints

28
Q

Describe metacarpophalangeal joints

A

Condyloid - rounded distal heads of metacarpals & concave prox ends of phalanges

Forms the knuckles

Each enclosed in a capsule & stabilised by strong collateral ligaments (MCP of thumb strengthened by additional dorsal ligament)

29
Q

What type of joints are DIP & PIPs?

A

Hinge joints allowing only flexion/extension

30
Q

Describe the range of motion in the:

  • Metacarpals?
  • MCPs?
  • DIP/PIPs?
A

Metacarpals - 2nd & 3rd immobile while a small amount of flexion/extension is allowed in 4th & 5th

MCPs - allow flex/extension & add/abduction. Max flex ~90 & extension varies between individuals depending on ligament laxity

PIPs - flexion 100-110
DIPs - flexion 90
(extension for both depends on ligament laxity)

31
Q

Describe the range of motion at the thumb

A

MCP does not allow as much flexion as fingers (30-90) but has more extension

CMC joint:

  • flexion (thumb across palm) - 15
  • extension (thumb away from side of palm) - 20
  • abduction (thumb away from palm) - 60
  • small degree of rotation
32
Q

What is the interaction between hand and wrist movements?

A

As wrist changes positions it alters lengths of tendons crossing from forearm into wrist

When wrist straight fingers can be easily clenched however if wrist is flexed it becomes difficult to fully flex fingers (and vice versa)

33
Q

What common features do unfused vertebrae have (bar C1 & 2)?`

A

Vertebral body - flat round central body

Neural arch - arch of bone that forms spinal foramen

Spinous process - projects inferoposteriorly

2x transverse processes - project laterally

34
Q

At what points to adjacent vertebrae articulate?

A

Vertebral body via intervertebral disc

2x facet joints - synovial joints either side of the arch

35
Q

Describe the nucleus pulposus

A

Lies in centre of intervertebral discs

Formed by strongly hydrophilic gel enmeshed in random collagen matrix

Gel produces high water content & elevated nucleus pressure which balances compressive stress

If applied stress increases, water is driven out of disc until new equilibrium is reached (disc rehydrates when stress decreases)

36
Q

Describe the annulus fibrosis

A

Tough layer that surrounds nucleus pulposus composed of collagen fibres forming concentric layers (lamellae) with alternating orientations

Arrangement resists high bending & torsional loads

37
Q

How are C1 & C2 different to other vertebrae?

A

C1 (atlas) - no body, composed of a ring withing which an oval fossa articulates with axis

C2 (axis) - has dens which protrudes superiorly & forms small synovial joint with oval fossa of atlas

38
Q

At which points of the thoracic vertebrae do the ribs articulate with?

A

Head of each rib with vertebral body

Tubercle of each rib with transverse process

39
Q

Describe motion in the spine:

  • flexion-extension?
  • lateral bending?
  • rotation?
A

Flexion-extension:

  • varies between different regions (cervical>thoracic)
  • extent of flexion & extension also varies between regions

Lateral bending:

  • similarly cervical has greatest Rom & thoracic least
  • no lateral bending between C1 & 2

Rotation:

  • decreases down spine
  • greatest between C1 & 2
40
Q

How can you explain higher load on spine when sitting compared to standing?

A

Moment arm of upper body weight about lumbar spine increases during sitting due to backward tilt of pelvis

This moment must be counter balanced by extension moment produced by posterior back muscles (producing compressive load)

BMSc Biomechanics (4 decks)

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