Elbow anatomy

Question 1

describe the ostoeology of the elbow ?

Answer 1

• shaft of humerus - spiral groove for the radial n
• radial n 13 cm from articular surface of trochlear
• distal flare contains medial and lateral epicondyles
• trochlea is spoon shaped - medially
• capitellum is lateral
• radiohumeral joint is a pivot joint
  
  • lateral radial head 120o devoid of cartilage
  • crucial for internal fixation of radial head fx
• ulnohumeral articuation is a hinge
  
  • coronoid fossa recieved coronoid tip in deep flexion
  • coronoid tip prevent post dislocations
  • sublime tubercle on ulna - anterior bundle of medial unlnar collateral ligament attaches distaly
• Distal attachment of capsule is 6mm distal to tip of coronoid

Question 2

Describe the muscles of the elbow?

Answer 2

• Flexors
  
  • Biceps
    
    • distal attachment is level of radial tuberosity
  • Brachialis
    
    • Attaches 11mm distal to tip of coronoid
  • Brachioradialis
• Extensors
  
  • triceps

Question 3

Describe the static primary stabilisers of the elbow?

Answer 3

• Static Primary
  
  • ulnohumeral joint - Coronoid
    
    • loss of 50% or more of coronoid height-> instability
  • Anterior bundle of MCL
    
    • MCL= ant/post/transverse bundles
    • Provides resistance to valgus/distractive stresses
    • ant oblique fibres- most important against valgus stress
    • in complex instability, mcl may unnecessary need repair/recon as teh 2ary function of radial head as valgus stabiliser.
  • **LCL complex **
    
    • Lateral ulnar collateral lig
    • radial collateral lig
    • annular lig
      
      • provides stability prox radioulnar joint
    • accessory collateral lig

Question 4

Describe the static secondary stabilisers of the elbow?

Answer 4

• Radiocapitellar joint
  
  • constraint to valgus stress
  • radial head provides approx 30^o valgus stability
  • most important at 0-30 o of flexion/pronation
• Capsule
  
  • greatest contribution when elbow extended
• origins of flexors and extensor tendons

Question 5

Describe the dynamic stabilisers of the elbow?

Answer 5

• muscles that cross elbow joint
  
  • Anconeus
  • Brachialis
  • Triceps
• they provide compressive stability

Question 6

Describe the secondary dynamic stabilisers to elbow?

Answer 6

• LCL
• Anconeus
• Lateral capsule
• 2ry dynamic stability to varus stress

Question 7

Dsecribe the nerves of the elbow?

Answer 7

• Musculcutanous n ( lateral cord BP)
  
  • supplies Biceps and brachialis
  • runs between these muscles
  • exits laterally , distal to biceps tendon
  • terminates as LABC ( forearm) deep to cephalic v
• Radial Nerve ( post cord BP)
  
  • leaves triangular interval ( Teresmaj, long head triceps, humeral shaft)
  • found in spiral groove 13 cm above trochlea
  • pierces lateral intermuscular septum 7.5cm above trochlea
    
    • usually junction middle/distal 3rd humerus
    • lies between brachialis /brachoradialis
  • distally located superifical to joint capsule at level of radiocapitellar joint
• Median N ( med/lat cords of BP)
  
  • course with brachial artery
  • runs lateral to medial
    
    • lies superficial to brachialis muscle at level of elbow jont
    • no branches in upper arm, branches to elbow joint
• Ulna Nerve ( medial cord)
  
  • runs medial to brachial artery
  • pierce medial intermuscular septum at level of arcade of Struthers and enters post compartment
  • transverses post to medial epicondyle thru cubital tunnel
  • no branches in upper arm
  • gives branches to elbow joint
    
    • first motor branch to FCU distal to elbow

Question 8

What is the blood supply to the elbow?

Answer 8

• Brachial artery
  
  • located medially in upper arm
  • enters cubital fossa laterally
    
    • contents
    • biceps tendon lateral, brachial artery , median n ( medial)
    • lateral border - brachioradialis
    • medial border- pronator teres
    • proximal border- distal humerus
  • ​at level of elbow splits into radial and ulnar arteries​

Question 9

Describe the kinematics of the elbow?

Answer 9

• Functional rom = 0-130^o
• although total rom = 0-150^o
• 50o pronation/supination
• flexion/extension
  
  • axis of rotation at trochlea
• valgus alignment
  
  • normal valgus carrying angle 7 males, 13 females

Question 10

Can you draw a free body diagram of the elbow?

Answer 10

• Sum Moments= 0
• 5B= 15W
• B= 3W
• Static loads are close to boy weight
• Dynamic loads are > than body weight

Question 11

What is the optimal posiiton for arthrodesis of the elbow?

Answer 11

• unilateral arhrodesis
  
  • 90^o flexion
  • 0-7^o valgus
• bilateral
  
  • one elbow 110^o for feeding
  • one elbow in 65^o of flexion for perineal hygiene