Functional anatomy and biomechanics (Upper Extremity)

Question 1

Humerus

Answer 1

• proximal end of humerus is approximately half a spheroid
• articular surface is coveredby hyaline cartilage
• head is retroverted 20-30 degrees
• longitudinal axis of head is 135 degrees from axos of neck

Question 2

Scapula

Answer 2

• large, flat triangular bone
• sits over 2nd-7th ribs
• three angles
• orientation of glenoid fossa places true abduction at 30 degrees anterior to frontal plane

Question 3

Shoulder biomechanics: GHJ arthro/osteo-kinematics

Answer 3

• occurs in opposite direction
  
  • with shoulder elevation of humerus, head of humerus moves in an inferior direction because of convex moving on concave
• rolling/gliding occurs during elevation of the humerus, so that the instantaneous center of rotation varies considerably during the complete range
• at approx 75 degrees of elevation, ER occurs, preventing compression of great tubercle against acromion

Question 4

Shouder biomechanics: Scapulothoracic and glenohumeral rhythm

Answer 4

• ratio of movement of the GH with the scapulothoracic joint
• with 180 deg ABD, there is a 2:1 ratio of movement between the two joints
• first 30-60 degrees of elevation occurs mainly in the GHJ
• 120 degrees of movement occurs at GHJ
• 60 degrees of movement at scapulothoracic joint

Question 5

Requirements of full elevation

Answer 5

• scapular stabilization
• inferior glide of humerus
• ER of humerus
• rotation of the clavicle at SC joint
• scapular abduction and lateral rotation of AC joint
• straightening of thoracic kyphosis

Question 6

Humeroulnar joint

Answer 6

• distal end humerus (trochlea) articulates with proximal end of ulna
• trochlea and trochlear notch face anteriorlyat a 45 degree angle, allowing space between ulna and humerus during flexion

Question 7

Humeroradial joint

Answer 7

• distal end humerus (capitulum) articulates with concave over facet of proximal radius

Question 8

Proximal radioulnar joint

Answer 8

• radial head is ovoid and cone shaped
• medil radius articulates with radial notch (of ulna)

Question 9

Distal radioulnar joint

Answer 9

• convex ulna articulates with concave radius (opposite to proximal articulation)

Question 10

Elbow ligaments

Answer 10

• UCL
• RCL
• Annular
• Quadrate
• Distal radioulnar

Question 11

Annular ligament

Answer 11

• osteofibrous ring attached to medial ulna and encircles radial head
• cone shaped, inner surface is lined with fibrocartilage
• protects radial head, especially in semiflexion, where it is unstable
• taut in extremes of pronation and supination

Question 12

Quadrate ligament

Answer 12

• extends from radial notch (una) to the neck of radius
• reinforces inferior joint capsule, maintains radial head in opposition to ulna, limits amount of spin in supination and pronation

Question 13

Elbow biomechanics

Answer 13

• ulna pronates slightly with extension. Ulna supinates slightly with flexion
• proximal ulna glides medially during extension and laterally during flexion
• flexion/extension of elbow is accompanied by screw-home mechanism with conjunct rotation ofulna. Ulna externally rotates (or supinates) during elbow flexion and internally rotates (or pronates) during

Question 14

Wrist and hand osteology

Answer 14

• radius is bioconcave relative to carpals
• ulna is convex at its distal end relative to the triquetrum

Question 15

Radiocarpal joint

Answer 15

• convex scaphoid and lunate articulate with concave radius

Question 16

Midcarpal joint

Answer 16

• articulation between four proximal and four distal carpal bones is known as midcarpal joint
• functional rather than anatomical joint
• middle and lateral pillars

Question 17

Carpometacarpal joint (CMC)

Answer 17

• first CMC (thumb) is a saddle articulation with trapezium being convex in medial/lateral direction and concave in anterior/posterior direction
• first metacarpal is opposite in shape to trapezium
• second through fifth CMC joints are essentially flat between bases of matacarpals and distal row of carpals

Question 18

Metacarpalphalangeal (MCP) joints

Answer 18

• consists of convex metacarpals with concave proximalm phalanges

Question 19

Extensor hood

Answer 19

• fibrous mechanism on the dorsum of each finger that is a fibrous expansion of the extensor digitorum tendon
• purpose is to assist with extension of the PIP and DIP joints

Question 20

Wrist and hand region nerves

Answer 20

• ulnar innervates hypothenar region (palmarly and dorsally), fifth digit, and medial half of fourth digit
• median nerve innervates reminder of palmar surface not innervated by ulnar nerve and dorsal portions of second, third, and lateral half of fourth digit from DIP to tip of finger
• radial nerve innervates remainder of dorsum not innervated b ulnar or median nerves

Question 21

Wrist flexion biomechanics

Answer 21

• proximal aspect of scaphoid/lunate glide dorsally relative to radius

Question 22

Wrist extension biomechanics

Answer 22

• proximal aspect of scahpoid/lunate glie ventrally relative to radius

Question 23

Wrist radial deviation biomechanics

Answer 23

• proximal row glides ulnarly
• proximal surface of scaphoid rotates palmarly

Question 24

Wrist ulnar deviation biomechanics

Answer 24

• proximal row glides radially as a unit