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Introduction
  • Joint includes
    • ulnohumeral joint
    • radiocapitellar joint
    • proximal radioulnar joint
  • Elbow function
    • crucial for activities of daily living
    • acts as a lever arm when positioning the hand
    • functions as a fulcrum for forearm lever
ROM
  • Functional ROM
    • 30° to 130 flexion/extension
      • total ROM is 0-150 degrees
    • 50° supination/supination
  • Normal carrying angle
    • normal valgus carrying angle
      • 5-10° for males
      • 10-15° for females
      • this diminishes with flexion
  • Axial loading
    • in extended elbow 
      • 40% of weight is through ulnohumeral joint
      • 60% of weight is through radiohumeral joint
Osteology & Arthrology
  • Osteology  
    • spiral groove
      • the shaft for humerus has a spiral groove posteriorly (contains radial nerve)
      • this lies approximately 13 cm proximal to the articular surface of trochlea
    • distal flare  
      • the distal flare of humerus includes the medial and lateral epicondyles
        • the flare accounts for half of the elbow joint
      • trochlea
        • is spool shaped and is located medially
      • capitellum
        • located laterally
    • sublime tubercle  
      • the sublime tubercle on the ulna is where the anterior bundle of the medial ulnar collateral ligament attaches distally
    • columns
      • distal humerus contains medial and lateral column
  • Arthrology
    • axis and alignment
      • anterior tilt
        • the joint surface is anteriorly tilted approximately 30 deg relative to shaft of humerus
      • varus/valgus
        • 6 deg of valgus
      • rotation
        • internally rotated by 5 deg
      • axis of rotation
        • is centered at trochlea and capitellum
        • it passes through anteroinferior medial epicondyle
    • joint type
      • pivot joint - the radiohumeral articulation is a pivot joint
        • radial head is covered by cartilage for approximately 240 degrees  
          • the lateral 120 degrees contains no cartilage
          • this is crucial for internal fixation of radial head fractures
      • hinge joint - the ulnohumeral articulation is a hinge joint
        • coronoid fossa
          • coronoid fossa on distal humerus receives the coronoid tip in deeper flexion
        • coronoid tip
          • the coronoid tip has a buttress effect in the prevention of posterior dislocations
    • capsule  
      • capsule is maximally distended at 70-80 deg of flexion
      • distal attachment of  anterior capsule is found 6 mm distal to tip of coronoid
        • coronoid is an intra-articular structure
Muscles of the Elbow
  • Flexors
    • biceps
      • the distal biceps attachment is at the level of the radial tuberosity
    • brachialis
      • the attachment of the brachialis 11 mm distal to the tip of the coronoid
    • brachoradialis
  • Extensors
    • triceps
Ligaments & Stability of Elbow
  • Primary static stabilizers
    • ulnohumeral joint (coronoid)
      • loss of 50% or more of coronoid height results in elbow instability
    • medial (ulnar) collateral ligament (MCL)  
      • overview
        • the MCL is composed of the anterior, posterior and transverse bundles
        • the MCL provides resistance to valgus and distractive stresses
      • anatomy
        • origin
          • posterior medial epicondyle
        • insertion
          • sublime tubercle of medial coronoid process
      • components
        • anterior bundle of MCL
          • most important restraint against valgus stresses
            • radial head is second most important
        • posterior bundle of MCL
          • the posterior bundle forms the floor of the cubital tunnel
          • primary restraint to valgus stress in maximal elbow flexion
          • if this is contracted, flexion may be limited 
        • transverse bundle of MCL
    • lateral collateral ligament complex (LCL)  
      • overview
        • consists of the 
          • radial collateral ligament (RCL)
          • lateral ulnar collateral ligament (LUCL)
            • function
              • primary restraint to varus and external stress during full arc of elbow motion
            • origin
              • posterior lateral epicondyle
            • insertion
              • crista supinatoris of proximal ulna
          • accessory collateral ligament
            • some believe that the the accessory collateral ligament and the radial collateral ligament contribute substantially to lateral elbow stability
          • annular ligament
            • provides stability to the proximal radioulnar joint
        • anatomy
          • the LCL arises from isometric point on lateral aspect of capitellum
        • function
          • optimal stability is conferred with an appropriately tensioned LCL repair
  • Secondary static stabilizers
    • radiocapitellar joint
      • this functions as an important constraint to valgus stress
        • the radial head provides approximately 30% of valgus stability
        • this is most important at 0-30 deg of flexion/pronation
    • capsule
      • greatest contribution the capsule on stability occurs with the elbow extended
    • origins of the flexor and extensor tendons
  • Dynamic stabilizers
    • includes muscles crossing elbow joint
      • anconeus
      • brachialis
      • triceps
      • biceps
    • they provide compressive stability
Nerve of the Elbow
  • Musculocutaneous nerve  
    • origin
      • lateral cord of the brachial plexus
    • anatomy at elbow
      • it exits laterally, distal to the biceps tendon 
      • it will terminate as the LABC (forearm), which is found deep to the cephalic vein
    • innervation at elbow
      • it supplies the biceps and brachialis
        • the nerve runs between these muscles 
  • Radial nerve 
    • origin
      • posterior cord of the brachial plexus
    • anatomy at elbow
      • it leaves the triangular interval (teres major, long head of triceps and humeral shaft)
      • found in spiral groove 13 cm above the trochlea
      • pierces lateral intermuscular septum 7.5 cm above the trochlea
        • this is usually at the junction of the middle and distal third of the humerus
        • lies between the brachialis and the brachioradialis
      • distally it is located superficial to the joint capsule, at the level of the radiocapitellar joint
  • Median nerve 
    • origin
      • medial/lateral cords of the brachial plexus
    • anatomy at elbow
      • it courses with brachial artery, running from lateral to medial
      • lies superficial to brachialis muscle at level of elbow joint
    • innervation at elbow
      • it gives branches to elbow joint
      • it has no branches in upper arm
  • Ulnar nerve
    • origin
      • medial cord of brachial plexus
    • anatomy at elbow
      • runs medial to brachial artery, pierces medial intermuscular septum (at the level of the arcade of Struthers) and enters posterior compartment
      • it traverses posterior to the medial epicondyle through the cubital tunnel
    • innervation at elbow
      • it gives branches to elbow joint
      • it has no branches in upper arm
      • first motor branch to FCU is found distal to the elbow joint
Blood Supply of Elbow
  • Brachial artery
    • is located medially in the upper arm
    • it enters cubital fossa laterally
      • contents-- biceps tendon (lateral), brachial artery, median nerve (medial) 
      • lateral border--brachoradialis
      • medial border--pronator teres
      • proximal border --distal humerus
    • at the level of elbow it splits into the radial and ulnar arteries
  • Principle branches
    • superior/inferior ulnar collateral
    • nutrient/muscular
    • supratrochlear
Kinematics
  • Motion vectors
    • flexion & extension
      • the axis of rotation is found at the center of trochlea
    • pronation (pronator teres and quadratus) & supination (biceps and supinator)
      • the axis of motion is found at the capitellum through to the radial/ulnar heads
      • this effectively forms a cone
  • Joint reaction force
    • there are large joint reaction forces due to short and inefficient lever arms around elbow (biceps inserts not far from center of rotation)
    • this contributes to degenerative changes of the elbow
  • Center of rotation
    • is a line through isometric points on the capitellum about trochlea
    • the axis of pronation / supination is a line drawn from capitellum, through radial head, to distal ulna
Free Body Diagram
  • Free body diagram demonstrate inefficiencies of elbow
    • sum M = 0
    • 5B = 15W
    • B = 3W
  • Static loads are close to body weight
  • Dynamic loads are greater than body weight
Arthrodesis
  • Optimal position
    • in a unilateral arthrodesis
      • 90° of flexion
      • 0-7° of valgus
    • in a bilateral arthrodesis
      • one elbow in 110 ° of flexion for feeding
      • one elbow in 65 ° of flexion for perineal hygiene
Diagnostic Injections
  • Intra-articular injection best given in soft spot formed by  
    • lateral epicondyle
    • the olecranon
    • radial head
 

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