Scaphoid Shift Test

Scaphoid-Shift

The scaphoid shift test aka midcarpal shift test is a variation of the Watson Test for scaphoid instability. A positive test can be caused by scapholunate ligament laxity or injury.

The Watson test evaluates scaphoid instability as the wrist is moved from radial to ulnar deviation (it’s not an “active” test)

To do the scaphoid shift test (as described by Lane in 1993)

  1. Use the same hand as the patient’s affected hand (suspicious of a right scaphoid problem? Use your right hand to test)
  2. Place your hand on the patient’s so that your thumb is over the volar surface of the scaphoid tubercle (the distal pole). Don’t apply any pressure (remember this area is probably at least a little sore and you want to remain friends for now)
  3. Gently move the wrist through ulnar/radial deviation (you can be fancy and consider this your Watson Test) and flexion/extension to relax the patient
  4. With the patient’s wrist in neutral extension and neutral (or slight radial deviation), forcefully and quickly push the scaphoid tubercle in the dorsal direction
    1. At this point, the patient is likely no longer your friend
  5. Note the degree of shift, any crepitus or clunk, and pain evoked.
  6. Remember to compare this to the opposite wrist

Extensor Compartments and Extensor Zones of the Hand

Extensor Compartments

There are a whole lot of wrist/finger extensors trying to fit in the wrist and anatomically these are divided into 6 compartments.

  1. First compartmentit’s this that is affected in de Quervain tenosynovitis
    • APL (abductor pollicis longus): attaches to 1st MC
    • EPB (extensor pollicis brevis): attaches to base of proximal phalanx
  2. Second compartment
    • ECRB (extensor carpi radialis brevis): attaches to 3rd MC
    • ECRL (extensor carpis radialis longus): attaches to 2nd MC
  3. Third compartment
    • EPL (extensor pollicis longus): passes around Lister’s tubercle of radius and inserts on distal phalanx of thumb (extends thumb IPJ)
  4. Fourth compartment – the posterior interosseus nerve lies on the floor of this compartment
    • EDC (extensor digitorum communis): no direct attachment to phalanx, attaches to the extensor expansions
    • EIP (extensor indicis proprius): lies ulnar to 1st EDC tendon)
  5. Fifth compartment
    • EDM (extensor digiti minimi): attaches to extensor expansion of little finger
  6. Sixth compartment
    • ECU (extensor carpi ulnaris): attaches to base of 5th MC

Extensor Zones

  • Zone I: over the DIP (this is where mallet finger injuries occur)
  • Zone II: middle phalanx
  • Zone III: over the PIP
  • Zone IV: proximal phalanx
  • Zone V: over the MCP
  • Zone VI: dorsum of hand/metacarpals
  • Zone VII: over the extensor retinaculum/carpals
  • Zone VIII: proximal wrist

Juncturae Tendinum

  • This is the connections of fascia between the EDC tendons and why you can’t stick your ring finger up alone, as it prevents independent movement.
  • It can also lead to confusion about whether an extensor tendon has been cut as the juncture tendinum transmits MCP joint extension even if a tendon is cut (as long as it’s cut distal to the JT)
  • But it’s also helpful as it prevents the cut tendon from retracting up into the forearm

Flexor Tenosynovitis (Kanavel’s Signs)

Suppurative (infectious) flexor tenosynovitis is a medical emergency because the tendon sheath is a closed space and too much swelling can lead to compartment syndrome and necrosis.

* You can’t really get these complications in extensor tendons as it is an open space (no tendon sheath)

There are 4 cardinal signs of flexor tenosynovitis (Kanavel’s Signs)

  1. Tenderness along the whole tendon sheath (late sign)
  2. Finger held in flexion
  3. Fusiform swelling (sausage finger)
  4. Pain with passive extension *this is the earliest finding

It is usually caused by some sort of inoculation, but this can be something very small and the patient may not be aware that he/she had ever been injured (can also be caused by local or hematogenous spread). It’s not unreasonable to get an x-ray to rule out other things and if there’s a fever or they seem very unwell, you can do blood cultures. You also probably want to start the patient on some broad spectrum antibiotics such as vancomycin + ciprofloxacin (or ceftriaxone).

Treatment is tendon sheath drainage and debridement as well as antibiotics.

Hand Exam: Motor 13/13 – Adductor Pollicis

Adductor Pollicis

  • Instruct the patient to do Froment’s sign – get the patient to forcibly grasp a piece of paper between the thumb and radial side of the index proximal phalanx
  • Origin:
    Oblique head: bases of 2nd and 3rd metacarpals, capitate and adjacent carpal bones
    Transverse head: anterior surface of body of 3rd metacarpal
  • Insertion: lateral side of base of proximal phalanx of thumb
  • Action: adducts thumb and flexes MP joint
  • Innervation: deep branch of the ulnar nerve

In a complete ulnar collateral ligament tear, the adductor pollicis can become entrapped between the remnants of the ligament

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 12/13 – Extensor Carpi Ulnaris (ECU)

Extensor Carpi Ulnaris (ECU)

  • Instruct the patient “Pull your hand up and out to the side”
  • Insertion: base of 5th metacarpal
  • Action: primarily ulnar deviation of the wrist, helps with wrist extension some too
  • Innervation: posterior interosseous branch of the radial nerve

Hand Exam: Motor 11/13 – Extensor Carpi Radialis Longus (ECRL) and Extensor Carpi Radialis Brevis (ECRB)

Extensor Carpi Radialis Longus (ECRL)

  • Instruct the patient “Make a fist and strongly bring your wrist back” and palpate over the tendons
  • Insertion: base of 2nd metacarpal
  • Action: radial deviation of wrist and some wrist extension too
  • Innervation: radial nerve

Extensor Carpi Radialis Brevis (ECRB)

  • Instruct the patient “Make a fist and strongly bring your wrist back” and palpate over the tendons
  • Insertion: base of 3rd metacarpal
  • Action: wrist extension (this is the major muscle for that)
  • Innervation: deep branch of 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 10/13 – Extensor Indicis Proprius (EIP) and Extensor Digiti Minimi (EDM)

Extensor Indicis Proprius (EIP)

  • Instruct the patient “Point with your index finger with the rest of your hand in a fist”
  • Insertion: extensor hood of index finger
  • Action: extension of MCP joints and IP joints of the index finger
  • Innervation: posterior interosseous branch of radial nerve

Extensor Digiti Minimi (EDM)

  • Instruct the patient “Stick out your little finger with the other fingers in a fist”
  • Insertion: extensor expansion at the base of the proximal phalanx of the little finger
  • Action: extension of MCP joints and IP joints of the little finger
  • Innervation: posterior interosseous branch of radial nerve
Alternatively you can get the patient to ROCK ON!!!! (testing both EIP and EDM at the same time)

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 9/13 – Extensor Digitorum Communis (EDC)

Extensor Digitorum Communis (EDC)

  • Instruct the patient “Straighten your fingers”
  • Insertion: no direct bony attachment, instead has a funky extensor mechanism involving the central slip
    * The EDC to the small finger is absent in 50% of the population
  • Action: extension of MCP joints and IP joints (IP joints with the help of the intrinsic muscles)
  • Innervation: posterior interosseous branch of 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 8/13 – Extensor Pollicis Longus (EPL)

 

EPL

Extensor Pollicis Longus (EPL)

  • Instruct the patient to lay their hand flat on a table and to “Lift only your thumb off the table”
  • Insertion: distal phalanx of thumb (first passes around Lister’s tubercle of the radius)
  • Action: extends 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 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
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