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DPT 726: Orthopaedic Foundations > Functional Anatomy and Biomechanics of Elbow and Radioulnar Joints > Flashcards

Functional Anatomy and Biomechanics of Elbow and Radioulnar Joints Flashcards

1
Q

Elbow and Radioulnar Joint Intro

A
  • elbow has 3 joints between 3 bones
  • movements between arm and forearm occurs at humeroulnar and humeroradial joints
  • movement within forearm occurs within proximal radioulnar joint and distal radioulnar joint
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2
Q

Humeroulnar Joint (HU)

A
  • articulation between humerus and ulna
  • major articulation in elbow
  • joint is composed of trochlea on distal humerus, trochlear notch on proximal ulna
  • flexion is limited by approximation of coronoid fossa on anterior humerus, coronoid process on front of ulna
  • extension is limited by approximation of olecranon fossa on humerus, and olecranon process on
  • motion: flexion/extension (hinge jt)
  • trochlea covered with articular cartilage: asymmetrical joint surface, asymmetry creates lateral angulation (valgus) of ulna when joint is extended
  • carrying angle describes this angulation: ranges from ~10-15* in males, and ~20-25* in females
  • valgus position lessens with elbow flexion
  • articular cartilage also covers anterior, inferior, and posterior surfaces of trochlear notch
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3
Q

Osteokinematics at HU Joint

A
  • flexion ROM ~145*: limited by soft tissue, posterior capsule, extensor mm, terminally restrained by bone on bone contact of coronoid process and fossa
  • extension ROM 0: 5-10 hyperextension more common in females, typically limited by joint capsule and flexor mm, terminally restrained by bone on bone contact
  • flexion/extension ROM needed for ADL ranges from 30-130* of flexion
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4
Q

Arthrokinematics in HU Joint

A
  • joint orientation: humerus-inferior, posterior; ulna-superior, anterior
  • concave surface: ulna
  • loose-pack position: 70* flexion, 10* supination
  • close-pack position: full extension and supination
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5
Q

Humeroradial Joint (HR)

A
  • 2nd joint participating in elbow flexion/extension
  • capitulum is distal articulation of humerus: articular cartilage on anterior and inferior surfaces, provides support against lateral compression in high velocity activities: eg throwing etc
  • pivot joint exists between capitulum and radial head
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6
Q

Osteokinematics at HR Joint

A
  • motion: flexion/extension, supination/pronation
  • pivot joint
  • same as osteokinematics in HU joint
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7
Q

Arthrokinematics in HR Joint

A
  • joint orientation: humerus inferior, radius superior
  • concave joint surface: radius
  • loose-pack position: full extension and supination
  • close-pack position: 90* flexion, 5* supination
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8
Q

Proximal Radioulnar Joint (PRU)

A
  • establishes motion in pronation and supination
  • articulation exists between: radial head, radial fossa on side of ulna
  • radial head rotates within fibrous osseous ring and annular ligament
  • radius and ulna lie parallel in neutral position
  • in full pronation radius crosses ulna diagonally, ulna moves laterally slightly
  • opposite happens in supination
  • interosseous membrane runs between ulna/radius and maintains specific relationship between bones-transmits force
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9
Q

Osteokinematics at PRU and DRU Joints

A
  • motion: pronation/supination
  • pronation ROM ~70*: limited by ligaments, joint capsule, and soft tissue compression as radius and ulna cross
  • supination ROM ~85*: limited by ligaments, capsule, and pronator mm
  • ~50* pronation and ~50* supination needed for most ADL
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10
Q

Arthrokinematics in PRU Joint

A
  • joint orientation: ulna-lateral, anterior; radius-medial, posterior
  • concave surface is ulna
  • loose-pack position is 35* flexion, 70* supination
  • close-pack position: full supination or pronation
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11
Q

Distal Radioulnar Joint

A
  • located at distal radius and ulna
  • adjacent to wrist joint
  • ulna separated from carpals by fibrocartilage disc: allows ulna to pronate/supinate without influencing wrist or carpal movements
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12
Q

Arthrokinematics at DRU Joint

A
  • joint orientation: ulna-lateral; radius-medial
  • concave joint surface is radius
  • loose-pack position is 10* of supination
  • close pack is full supination or pronation
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13
Q

Ligaments

A
  • collateral ligaments support medial and lateral elbow
  • medial (ulnar) collateral ligament connects ulna to humerus: resists valgus stress upon elbow, most forces directly medially in elbow
  • lateral (radial) collateral ligament provide support against rarer varus forces
  • annular ligament wraps around radial head, attaches to ulna, holds radius in elbow but allows rotation
  • quadrate ligament and interosseous membrane provide additional support to radioulnar joint
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14
Q

Gross Motion in Elbow Region

A
  • close pack position for 3 joints are at different points in ROM
  • radio-humeral joint at 90* and in semi-pronated position
  • ulnar-humeral joint is full extension
  • proximal radio-ulnar joint when in slightly flexed, semi-pronated position: complements HRJ
  • approximate ROM values for flexion/extension: ~145* active flexion, 160* passive, ~0-10* hyperextension
  • flexion limited by soft tissue, posterior capsule, extensor tightness; bone-to-bone restriction at coronoid process
  • extension limited by anterior capsule, flexor tightness; bone-to-bone restriction at olecranon at end range
  • most ADL require 100-140* flexion/extension ROM: ranges from 30-120* for many activities
  • pronation ROM ~70* limited by ligaments, joint capsule, soft tissue compression as radius and ulna cross
  • supination ROM ~85* limited by ligaments, joint capsule and pronator muscle
  • most ADL require ~50* pronation to ~50* supination
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15
Q

Case Study-Jenny works in purse factory and quits and has tennis elbow. How might we deduce whether the lateral elbow pain is truly coming from structures in elbow or somewhere else?

A
  • check dermatomes or myotomes try to recreate pain-if able to recreate more likely to be within our scope of practice; non-reproducible means a metabolic problem outside the scope of our practice
  • dx by exclusion: ask questions to rule options out
  • medical hx: any prior elbow issues
  • pain rating at beginning of work vs end
  • anything you do to relieve the pain?
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16
Q

Muscular Actions in Elbow Region

A
  • 24 muscles cross elbow
  • some act exclusively at elbow (brachialis)
  • most are capable of contributing to three movements at elbow, wrist, and fingers
  • yet one mm is usually dominant: it is the movement for which mm or muscle group is associated
17
Q

Elbow Flexors

A
  • biceps, brachialis, brachioradialis, pronator teres, extensor carpi radialis
  • collectively become more effective as elbow flexion increases: increase mechanical advantage with increase in moment arm
18
Q

Brachialis

A
  • deep to biceps
  • strongest flexor
  • secondary to its role as only pure elbow flexor
  • does more work than the other muscles
  • output not influenced by pronation or supination of forearm
  • maximum output at ~120* elbow flexion
  • active at all positions, speeds, with or without resistance
19
Q

Biceps Brachii

A
  • proximal attachment: long head originates at supraglenoid fossa of scapula; short head to coracoid process
  • distal to radial tuberosity of radius
  • contribution to flexion depends on position of arm: most active during middle 90* of flexion (between 30* and 120*)
  • contribution to flexion also depends on position of forearm in pronation and supination: most effective flexor within forearm in supination; attachment twisted under radius when pronated
  • activity drops in semi-pronated position-in prone position contributes minimally, even against resistance
  • its contribution can be affected if arm is extended or hyperextended
  • maximal output occurs at ~120* of flexion
20
Q

Brachioradialis

A
  • between distal humerus and styloid process of radius
  • small volume and very long fibers
  • efficient muscle used with rapid elbow flexion and against resistance
  • produces greatest activity at ~120* of flexion with forearm in supinated position
  • does not increase its activity when arm is semi-pronated or pronated
21
Q

Elbow Extensors

A
  • functional antagonist of elbow flexors
  • located on posterior humerus
  • triceps and anconeus (4th head of triceps)
22
Q

Triceps Brachii

A
  • strongest arm muscle: secondary to greatest mm volume in upper arm
  • output not affected by position of forearm supination/pronation
  • has 3 portions: long head (least active), medial, and short heads
  • long head only portion to cross shoulder joint, makes its action and effectiveness partially dependent upon shoulder position, least active of 3 heads
23
Q

The Pronators

A
  • pronation the 3rd motion produced at radioulnar articulations
  • pronator quadratus: between distal ulna and radius, activity and production greater of 2 pronator mm, more active regardless of elbow position, fast or slow activity, or with or without resistance
  • pronator teres: contribution increases with rapid pronation or against high load; most active at 60* forearm flexion
24
Q

Supinators

A
  • produced primarily by biceps brachii and supinator mm
  • supinator: between humerus, ulna on one side and radius
  • only muscle contributing to slow unresisted supination in all elbow positions
  • biceps: active when elbow is flexed, very effective supinator at 90* of elbow flexion, increased effectiveness with rapid or resisted supination
25
Q

Strength of Forearm Muscles

A
  • flexors nearly 2x stronger than extensors in all positions
  • makes us more effective at pulling than pushing
  • flexion force production: semi-pronated > supinated > pronated; semi-pronated most common in ADL, include semi-pronated strengthening to take advantage of forearm strength
26
Q

Therapeutic Exercise in Elbow Region

A
  • complete isolation of specific muscle very difficult
  • because arm and forearm mm work in combination functionally
  • stretching exercise, manual resistance, isotonic resistance commonly used in rehab
  • therapeutic exercise best prescribed with an eye on return to function
  • eccentric resistance exercise very important for conditions such as lateral epicondylitis
  • typically need to modify exercise prescription for individual patient
27
Q

Lateral Epicondylitis

A
  • aka tennis elbow
  • onset may be slow/insidious or linked to trauma
  • usually involves inflammation of tendinous attachment into periosteum
  • irritation of forearm extensors-ECRB, ECRL, ECU, extensor communis, supinator
  • repetitive activities a common trigger
  • palpation to lateral humeral condyle is typically painful
28
Q

Medical Epicondylitis

A
  • aka golfer’s elbow
  • common in any repetitive gripping activity
  • irritation of flexors and pronators-teres, FCR
  • patient hx and intervention conceptually as with lateral epicondylitis
29
Q

Bursitis

A
  • olecranon bursa most commonly affected
  • may be caused by variety of irritants: trauma, gout, RA, etc
  • most common symptom is edema
  • intervention: anti-inflammatories, remove/change irritating stimulus, strengthen/stretch muscles in area
30
Q

Ulnar Nerve Injuries

A
  • often develop secondary to entrapment at cubital tunnel
  • also irritated by OA, spurs, fracture, soft tissue lesions
  • patient hx: numbness/tingling 4th and 5th fingers, elbow/forearm pain
  • PT often focuses on change in biomechanics, change in motor programs, neural glides
  • address ROM at neighboring joints
  • radial and median nerves are also injured too

DPT 726: Orthopaedic Foundations (14 decks)

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