Hand Exam: Motor 7/13 – Extensor Pollicis Brevis (EPB) and Abductor Pollicis Longus (APL)

Thenar Muscles: Instruct the patient “Bring your thumb out to the side”
All supplied by posterior interosseous branch of the radial nerve 

Abductor Pollicis Longus (APL)

  • Insertion: base of the 1st metacarpal
  • Action: extension of the 1st metacarpal and helps with abduction
  • Innervation: posterior interosseous branch of the radial nerve

Extensor Pollicis Brevis (EPB)

  • Insertion: base of the proximal phalanx of thumb
  • Action: combines with EPL to extend thumb IP joint
  • Innervation: posterior interosseous branch of the radial nerve

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis

Hand Exam: Motor 6/13 – Hypothenar Muscles

Hypothenar Muscles: Instruct the patient “Bring your little finger away from the others”
All supplied by deep branch of ulnar nerve 

Abductor Digiti Minimi (ADM)

  • Origin: pisiform
  • Insertion: medial side of base of proximal phalanx of small finger
  • Action: abducts small finger, extends IP joints when MCP joint is stabilized
  • Innervation: deep branch of ulnar nerve

Flexor Digiti Minimi (FDM)

  • Origin: Flexor retinaculum and hook of the hamate
  • Insertion: medial side of base of proximal phalanx of small finger
  • Action: flexes MCP joint
  • Innervation: deep branch of ulnar nerve

Opponens Digiti Minimi (ODM) 

  • Origin: Flexor retinaculum and hook of the hamate
  • Insertion: medial border of 5th metacarpal
  • Action: rolls 5th metacarpal toward thumb, flexes 4th and 5th MCP joints for better thumb opposition
  • Innervation: deep branch of ulnar nerve

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis


Hand Exam: Motor 5/13 – Interosseous Muscles

 

Interosseous Muscles: Instruct the patient “Spread your fingers apart”

Palmar Interossei (3) – PAD (Palmars ADduct, bring fingers together)

  • Action: adduction of index, ring and small fingers
  • Innervation: deep branch of ulnar nerve

Dorsal Interossei (4) – DAB (Dorsals ABduct, bring fingers apart)

  • Action: abduction of index, long, ring and small fingers
  • Innervation: deep branch of ulnar nerve

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis

Hand Exam: Motor 4/13 – Thenar Muscles

Thenar Muscles (radial group): Instruct the patient “Touch the thumb to the small finger”
All supplied by recurrent branch of median nerve 

Abductor Pollicis Brevis (APD)

  • Origin: flexor retinaculum and tubercles of scaphoid and trapezium
  • Insertion: lateral side of base of the proximal phalanx of the thumb
  • Action: palmar abduction, tiny bit MP flexion and IP extension
  • Innervation: recurrent branch of median nerve

Opponens Pollicis (OP)

  • Origin: Flexor retinaculum and tubercle of trapezium
  • Insertion: lateral side of first metacarpal bone
  • Action: rotates thumb pinch with index finger
  • Innervation: recurrent branch of median nerve

Flexor Pollicis Brevis (FPB)

  • Origin: Flexor retinaculum and tubercle of trapezium
  • Insertion: medial side of base of proximal phalanx of the thumb
  • Action: flexes and stabilizes MPJ
  • Innervation: recurrent branch of median nerve

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis


Hand Exam: Motor 3/13 – Flexor Digitorum Superficialis (FDS)

Flexor Digitorum Superficialis (FDS)

  • Instruct the patient “Bend your finger at the middle joint” while stabilizing their other fingers (otherwise FDP tries to help out)
  • Insertion: middle phalanxes of fingers
  • Action: flexion of proximal interphalangeal joints
  • Innervation: Median nerve

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis


Hand Exam: Motor 2/13 – Flexor Digitorum Profundus (FDP)

Flexor Digitorum Profundus (FDP)

  • Instruct the patient “Bend the tip of your finger” while stabilizing their PIP joint
  • Insertion: distal phalanxes of fingers
  • Action: flexion of distal interphalangeal joints
  • Innervation: Median nerve (radial half), Ulnar nerve (ulnar half)

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis

Hand Exam: Motor 1/13 – Flexor Pollicis Longus (FPL)

Flexor Pollicis Longus (FPL)

  • Instruct the patient “Bend the tip of your thumb”
  • Insertion: distal phalanx of thumb
  • Action: flexion of thumb IP joint
  • Innervation: Median nerve

The 13 muscle groups you need to test in the hand exam:

  1. FPL
  2. FDP
  3. FDS
  4. Thenar muscles
  5. Interosseous
  6. Hypothenar muscles
  7. EPB and APL
  8. EPL
  9. EDC
  10. EIP and EDM
  11. ECRL and ECRB
  12. ECU
  13. Adductor Pollicis


Local Anesthetics and Freezing Fingers

Local anesthetics work by blocking afferent pain sensation. This is great because it means that the patient can be wide awake and not able to feel you reduce their fracture, sew up their gaping laceration or release their carpal tunnel.

Most local anesthetics fall into two broad categories, the esters and the amides. To remember which is which, think about amIdes having an I in the prefix and esters not.

Amides Esters
Lidocaine (Xylocaine)
Mepivacaine
Bupivacaine
Ropivacaine
Procaine (Novocaine)
Chloroprocaine
Cocaine
Benzocaine

Epinephrine can be added to local anesthetics to induce vasoconstriction. This reduces blood loss and prevents excess systemic spread of the anesthetic. As a result, the maximum dose and the duration of action are less without epi than with.

Duration Maximum Dose
Lidocaine without 0.5-1h 5mg/kg (35mL of 1% for a 70kg adult)
Lidocaine with epi 2-6h 7mg/kg (49mL of 1% for 70kg adult)

Signs of local anesthetic overdose

  • Early signs: Perioral numbness/tingling, tinnitus
  • Severe toxicity: grand mal seizures
    * Some people are sensitive to the metabolite PABA that the ester class produces, however amides do not have this metabolite.

How to Freeze a finger

Ring blocks (aiming for the digital nerves on either side of the finger) ARE NOT necessary, you just increase the likelihood that you’re going to injure one with the needle. Instead do a single poke on the volar aspect of the MCP joint, perpendicular to the skin and inject 2-3 cc.  The freezing should go in without much resistance, too much means that the needle is either in the dermis or in the flexor tendon sheath. This should freeze the entire volar aspect of the finger and roughly to from the tip to the DIP joint on the dorsum. If you need the entire finger frozen (e.g. for a reduction), you can also inject 1-2 cc on the dorsal MCP.

The smaller the needle, the less pain is caused by the freezing (which is acidic and stings more than you’d think). Adding 1 cc of bicarb for every 10cc of lidocaine also helps reduce pain, making you a nice person.

Median Nerve Distribution

The median nerve provides sensory and motor innervation to the anterior compartment of the forearm and hand.

  • Motor branches
    • Pronator teres
    • Flexor carpi radialis
    • Flexor carpi sublimis
  • Anterior interosseus (motor)
    • Flexor pollicis longus
    • Flexor digitorum profundus to 2nd & 3rd fingers
    • Pronator quadratus
  • Palmar cutaneous
    • Sensory distribution: Skin over thenar eminence
  • Terminal motor
    • Abductor pollicis brevis
    • Opponens pollicis
    • Lumbricals: 1st & 2nd
    • ± Flexor pollicis brevis: Also innervated by ulnar nerve
  • Terminal sensory
    • Sensory to palmar surface of thumb, 2nd, 3rd & lateral 1/2 of 4th finger

Physical exam for different muscles supplied by median nerve

  • Flexor digitorum superficialis: patient flexes fingers at PIP joint against resistance
  • Flexor digitorum profundus: patient flexes fingers at DIP joint against resistance
  • Flexor pollicis longus (anterior interosseous nerve): flexes distal phalanx of thumb against resistance
  • Abductor pollicis brevis: patient abducts thumb at right angles to palm against resistance
  • Opponens pollicis: patient touches base of little finger with the thumb, examiner tries to pull  apart
  • 1st lumbrical interosseous: patient extends finger at the PIP joint against resistance with the MCP joint hyperextended and fixed

Holding Hands (the hand exam)

This wasn’t even going to be an education post, but I got guilted into it. The original is 18×24″, oil on canvas.

The hand exam

  • Inspection: You can use the acronym SEADS: swelling, erythema, atrophy, deformity, skin changes. Remember: you should be able to see their whole arm up to the elbows
  • Palpation: You can use the acronym TEST CA: tenderness, effusion, swelling, temperature, crepitations, atrophy
  • Range of Motion and Power: Do active, if it’s not full you can then check passive.
  • Special Tests: fancy things for carpal tunnel like Phalen’s and Tinel’s