Scaphoid Shift Test

Posted on October 31, 2015 by Ali

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)

Use the same hand as the patient’s affected hand (suspicious of a right scaphoid problem? Use your right hand to test)
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)
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
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
Note the degree of shift, any crepitus or clunk, and pain evoked.
Remember to compare this to the opposite wrist

Extensor Compartments and Extensor Zones of the Hand

Posted on October 21, 2012 by Ali

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.

First compartment – it’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
Second compartment
- ECRB (extensor carpi radialis brevis): attaches to 3rd MC
- ECRL (extensor carpis radialis longus): attaches to 2nd MC
Third compartment
- EPL (extensor pollicis longus): passes around Lister’s tubercle of radius and inserts on distal phalanx of thumb (extends thumb IPJ)
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)
Fifth compartment
- EDM (extensor digiti minimi): attaches to extensor expansion of little finger
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)

Posted on October 4, 2012 by Ali

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)

Tenderness along the whole tendon sheath (late sign)
Finger held in flexion
Fusiform swelling (sausage finger)
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

Posted on April 16, 2012 by Ali

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:

Hand Exam: Motor 12/13 – Extensor Carpi Ulnaris (ECU)

Posted on April 16, 2012 by Ali

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

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

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

Posted on April 16, 2012 by Ali

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:

Hand Exam: Motor 10/13 – Extensor Indicis Proprius (EIP) and Extensor Digiti Minimi (EDM)

Posted on April 16, 2012 by Ali

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:

Hand Exam: Motor 9/13 – Extensor Digitorum Communis (EDC)

Posted on April 13, 2012 by Ali

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:

Hand Exam: Motor 8/13 – Extensor Pollicis Longus (EPL)

Posted on April 12, 2012 by Ali

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:

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

Posted on April 11, 2012 by Ali

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:

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Scaphoid Shift Test