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Elbow Anatomy

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Muscles of the Arm
Muscle Innervation Origin Insertion Action Nerve Root
1 Coracobrachialis Musculocutaneous Coracoid mid.humerus medial Flexion, adduction C5,6,7 lat cord
2 Biceps Musculocutaneous Coracoid(SH), Supraglenoid (LH) Radial tuberosity Supination, flexion C5,6 lat cord
3 Brachialis Musculocutaneous-medial, radial lateral Ant. Humerus Ulnar tuberosity (ant) Flexes forearm C5,6 lat/post cord
4 Triceps Radial Infraglenoid(LH), Post.Humerus(lat H.), Post. Humerus (MH) Olecranon Extends forearm C6,7,8,T1 post cord
Arthrex

Muscles of the Forearm
Muscle Innervation Origin Insertion Action Nerve Root
Superficial Flexors          
Pronator teres(PT) median Med. Epicondyle and coronoid Mid. Lat. Radius Pronate, flex, forearm C6,7 med/lat cords
Flexor carpi radialis(FCR) median Med. Epicondyle and coronoid 2nd and 3rd Metacarpal bases Flex wrist C6,7,8 med/lat cords
Palmaris Longus(PL) median Med. Epicondyle  Palmar aponeurosis Flex wrist C7,8,T1 med/lat cords
Flexor carpi ulnaris(FCU) Ulnar Med. Epicondlye and post. Ulna Pisiform Flex wrist  
Flexor digitorum superficialis(FDS) Median Med. Epicondyle and ant. Radius base of middle phalanges Flex PIP C7,8,T1 med/lat cords
Deep flexors          
Flexor digitorum profundus(FDP) medain-ant. interoseous and ulnar Ant. and Med. ulna Base of distal phalanges Flex DIP  
Flexor pollicis longus Median-ant. interosseous Ant. and lat. radius base of distal phalanxy Flex IP, thumb  
Pronator quadratus Medain-ant. interosseous Distal ulna volar radius Pronate, hand  
Superficial Extensors          
Brachioradialis Radial Lat.supracondylar humerus Lat. distal radius Flex forearm  
Ext. carpi radialis longus (ECRL) Radial Lat. supracondylar humerus 2nd Metacarpal base Extend wrist  
Ext. carpi radialis brevis (ECRB) Radial Lat. epicondyle of humerus 3rd Metacarpal Base Extend wrist  
Anconeus Radial Lat. epicondyle of humerus Prox. dorsal ulna Extend forearm  
Extensor digitorum Radial-post. interosseous Lat.epicondyle of humerus Extensor aponeurosis Extends digits  
Extensor digiti minimi Radial-post. interosseous Common extensor tendon Small finger extensor carpi ulnaris Extend small finger  
Ext. Carpi ulnaris Radial-post. interosseous Lat. epicondyle of humerus 5th metacapal base Extend/adduct hand  
Deep Extensors          
Supinator Radial-post. interosseous Lat. epicondyle of humerus, ulna Dorsoloateral radius Supinate forearm  
Abductor pollicis longus(APL) Radial-post. interosseous Dorsal ulna/radius 1st Metacarpal base abduct thumb,extend  
Extensor Pollicis Brevis (EPB) Radial-post. interosseous dorsal radius thumb prox phalangeal base extend thumb MCP C6,7,8 post cord
Extensor Pollicis Longus (EPL) Radial-post. interosseous dorsolateral ulna thumb dorsal phalanx base extend thumb IP C6,7,8 post cord
Extensor Indicis Proprius (EIP) Radial-post. interosseous dorsolateral ulna index finger extensor apparatus extend index finger C6,7,8 post cord

Normal elbow ROM

Extension/Flexion

0/150

Pronation

80

Suppination

80

Flexion from = 0° to 140° +/- 10°
Forearm rotation = 80° to 90° in both supination and pronation.
American Academy of Orthopaedic Surgeons: Joint Motion: Method of Measuring and Recording. Chicago, AAOS, 1965
Boone DC, Azen SP: Normal range of motion of joints in male subjects. JBJS 61A: 756–759, 1979
Morrey BF, Chao EY: Passive motion of the elbow joint. J Bone Joint Surg 58A: 501–508, 1976

Functional elbow ROM (Morrey BF, JBJS 63A;872:1981)

Extension/Flexion

30/130

Pronation

50

Suppination

50
Elbow Ligaments

Medial Collateral Ligament

  • synonyms: Ulnar collateral ligament.
  • consists of anterior bundle, posterior bundle and transverse segment
  • Anterior bundle: origin=inferior aspect of the medial epicondyle. Insertion=sublime tubercle of ulna. Primary restraint to valgus stress at the elbow from 30° to 120°. Taut in extension. (Morrey BF, CORR 1991;265:187). Subjected to near-failure tensile stresses during the acceleration phase of the throwing motion.
  • Posterior bundle; Origin=medial epicondyle slightly posterior to its most inferior portion. Insertion=broadly onto the olecranon. Taut in flexion.
  • MCL is taut in pronation. LCL is taut in supination.
  • Morrey BF, CORR 1985;201:84
  • Morrey BF, CORR 1991;265:187
  • Morrey BF, AJSM 1983;11:315

Lateral Collateral Ligament

  • Synonyms: lateral ulnar collateral ligament, LUCL, LCL (sometimes considered to include: radial collateral ligament(radial band), annular ligament, & lateral ulnar collateral ligament(ulnar band).  Ulnar band of LCL is the primary lateral stabilizer.)
  • Origin: lateral epicondyle
  • Insertion: tubercle of the supinator crest of the ulna.
  • Stabilizer against posterolateral rotational instability
  • Taut throughout entire range of motion of the elbow.
  • MCL is taut in pronation. LCL is taut in supination.

Annular Ligament

  • the primary restraint to posterolateral rotatory instability of the elbow is the combination of the lateral collateral and annular ligaments. The principal secondary restraints are the extensor muscles with their fascial bands and intermuscular septa. (Cohen MS, JBJS 1997;79A:225)
Elbow Arteries and Veins
Radial artery
Ulnar artery
Leash of Henry
  • series of veins encountered in volar approaches to the proximal forearm (Henry approach).
Elbow Nerves
Radial Nerve
  • in average male the radial nerve at the spiral groove is @15cm from the distal humeral articular surface (Uhl RL, J Orthop Trauma 10:338;1996)
  • Proximal to elbow radial nerve is bewteen the brachioradialis and brachialis. Divides into superficial radial nerve and the PIN at the level of the radial head.
Ulnar Nerve
Median Nerve
Lateral Antebrachial Cutaneous Nerve
  • lateral antebrachial cutaneous nerve-at risk during lateral approaches and anterior approaches for distal biceps tendon repair.  Pierces brachial fascia 3cm proximal to the lateral epicondyle and passes 4.5cm medial to the lateral epicondyle.  Passes lateral to the biceps tendon. Ant/ post branches supply anteriolateral/posterolateral surfaces of forearm.
Medial Antebrachial Cutaneous Nerve
  • medial antebrachial cutaneous nerve-at risk during medial approaches.  Posterior branch divides into 2-3 branches that cross from 6cm proximal to 6cm distal to medial epicondyle.Lie just superficial to deep fascia
  • Painful neuormas / paresthesias can develop due to injury during medial approaches / cubital tunnel surgery (Dellon AL, J Hand Surg 1985;10Br:33).
Posterior Interosseus Nerve
  • Pierces the supinator muscle and wraps around the radius approximately 1-1.5cm distal to the radial tuberosity.
  • The forearm should be fully pronated during lateral approaches to the elbow and fully supinated (moves PIN laterally) during anterior approaches to decrease risk of PIN injury.
  • Exposure past the midline of the radial tuberosity during lateral approaches risks PIN injury. (Tornetta P, 3rd, CORR 1997;215)
Elbow Approaches

References

  1. Patterson, Surgical Exposures of the elbow. CORR 370:19;2000
  2. Bryan Morrey Triceps sparing approach CORR 166:188;1982

Arthroscopy
Posterior Utilitarian Approach
  • Longitudinal midline posterior incision minimizes risk to cutaneous nerves.
Posteromedial approach
Medial Approach to Ulnar Nerve
Carrying Angle
  • 11° of valgus in men
  • 13° of valgus in women
  • Beals RK: The normal carrying angle of the elbow. A radiographic study of 422 patients. Clin Orthop 119: 194–196, 1976
  • Throwing athletes: may be greater than 15° due to adaptive changes from repetitive stress. (King JW, Clin Orthop 1969;67: 116–123)
  • The carrying angle progresses into a more varus alignment as the elbow is flexed (Morrey BF, JBJS 1976;58A:501)
  • Carrying angle is difficult to assess if there is any flexion contracture.
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