PROCEDURE

1. PRE-WORK (before lab) review the organization of the bony upper extremity from your atlas or on an articulated skeleton in the lab.
    (Netter429) (Netter442) (Netter446)

a) Review the motions of pronation and supination. The radius and ulna bones cross over each other when the hand is fully pronated and are essentially parallel when the hand is fully supinated. During supination/pronation the radius rotates while the ulna remains fixed.

b) On your own hand with the thumb fully extended, palpate to find the anatomical snuff box formed by the tendons of abductor pollicis longus and extensor pollicis longus & brevis. The floor of the snuff box is the scaphoid and trapezium bones.

The radial artery courses from the anterior wrist through the anatomical snuff box to supply the deep palmar arch (a radial branch also contributes to the superficial palmar arch seen on the anterior side).

A radial pulse can also be detected in many, but not all, individuals by pressing a finger firmly into the anatomical snuff box while extending the thumb. Detection of the radial pulse is typically more reliable on the anterior side of the wrist, but detection is sometimes possible in the anatomic snuff box.

2. During this lab session, as most donor forearms are halfway pronated, a good position is to partly flex the elbow and rotate the forearm such that the palm is angled over the abdomen providing ready access to the posterior aspect of the forearm and hand.
    (Photo6104)

If it is necessary for the individual donor to abduct the forearm over the edge of the table, remember to place one of the disposable chuck pads on the floor to catch potential drips.

CLINICAL EXERCISE - Thumb carpometacarpal platelet rich plasma injection

3. An emerging tool in combating degenerative disorders, such as osteoarthritis, is platelet rich plasma injection into the tendon, ligament, or joint cavity. 

In this clinical exercise, you have the chance to perform a base of thumb injection inserting a needle into the thumb carpometacarpal joint. For the steps to take:
                                 ------ click here ------

4. Remove skin from the posterior forearm and dorsum of the hand.
    (Figure633) (Netter458) (Photo6105) (Photo6105a)

Not all fingers need to have skin removed, but remove skin completely from digit 2 (index finger).

Numerous cutaneous nerves and superficial veins are present in the forearm, but we will not examine these in detail and they should be removed along with the skin. This network extends as a rich venous plexus on the dorsum of the hand.

The superficial dorsal veins of the hand are a common target for blood collection or I.V. lines. The other common upper limb venous access location is the median cubital vein. Additionally, proximal venous access can be achieved through a central line into the subclavian vein.

PROCEDURE - POSTERIOR FOREARM

5. Use scissors to make a longitudinal cut through the antebrachial fascia from the elbow to the wrist.
    (Netter406)

The posterior forearm compartment (extensor compartment) is sheathed by the antebrachial fascia.

The antebrachial fascia at the wrist thickens into a specialization of stronger connective tissue securing the extensor tendons, called the extensor retinaculum.

6. Use your fingers and blunt dissection to spread open and remove the antebrachial fascia working laterally over to the radius bone and medially over to the ulna bone. 
    (Netter406) (Photo6106) (Photo6039)

Delicate connective tissue septa extend from the antebrachial fascia to wrap each muscle in the posterior compartment.  It may be necessary to trim through these septa as you spread open the antebrachial fascia.

The antebrachial fascia may be removed as needed to clear the dissection area.

7. Examine at the lateral epicondyle of the humerus for the brachioradialis muscle.
    (Figure635) (Netter434) (Netter436)
    (Photo6107) (Photo6041)

The brachioradialis muscle originates from the humerus just superior the lateral epicondyle of the humerus, thus the muscle is not part of the group that utilizes the common extensor tendon.

8. Isolate the brachioradialis muscle and follow the muscle distally as it courses along the anterolateral side of the forearm.
    (Figure635) (Netter434) (Netter436) (Photo6107)

Although the brachioradialis muscle spans to the anterolateral aspect of the forearm attaching to the distal radius, the muscle originates posteriorly and is innervated by the radial nerve. 

Thus, the muscle is classified in posterior compartment even though it has flexor function.  The brachioradialis muscle is a 'paradoxical' muscle compared to the general extensor function of other posterior muscles. All posterior muscles are innervated by branches of the radial nerve, including brachioradialis muscle.

9. Dissect parallel and medial to the brachioradialis muscle on the posterior side of the limb to identify the extensor carpi radialis longus muscle and tendon. 
    (Figure635) (Netter434) (Netter431) (Photo6108)

The extensor carpi radialis longus tendon passes deep to two thumb muscles, abductor pollicis longus and extensor pollicis brevis. These are termed 'outcropping' muscles and will be examined later in the lab. Follow the tendon only as far as where it passes deep to the two outcropping muscles.

The extensor carpi radialis longus muscle lies adjacent to brachioradialis, but has a tendon that extends further to attach to the base of the 2nd metacarpal bone and has typical posterior compartment extensor function.

10. Blunt dissect at the elbow to find a group of muscles that all share a common tendon attached to the lateral epicondyle of the humerus.
     (Figure635) (Netter434) (Netter431) (Photo6108)

This is the common extensor tendon to which the remaining four of the superficial layer muscles of the posterior forearm attach.

The muscles that share the common extensor tendon will be examined individually below, but are the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris muscles.

11. Blunt dissect along the lateral side of the common extensor tendon for fibers of the extensor carpi radialis brevis muscle.
     (Figure635) (Netter434) (Netter431) (Photo6109)

The extensor carpi radialis brevis tendon also passes deep to two thumb outcropping muscles, abductor pollicis longus and extensor pollicis brevis. Follow the tendon only as far as where it passes deep to the thumb muscles.

The tendon can 'hide' slightly below to the extensor carpi radialis longus tendon so what looks like one tendon might be two closely associated tendons.

Extensor carpi radialis brevis is the most lateral of the four muscles sharing the common extensor tendon (extensor carpi radialis longus is more lateral, but is not part of the common extensor tendon).

12. Blunt dissect medial to the extensor carpi radialis brevis for the large extensor digitorum muscle.
     (Figure635) (Netter434) (Netter431) (Photo6110)

Distally, the muscle belly separates forming four tendons that arise from the muscle and travel into the wrist. Follow them just to the wrist as we will examine the dorsum of the hand later in the lab.

These tendons attach to the extensor expansion over the phalanges of the four fingers.

13. Blunt dissect medial to the extensor digitorum muscle for the extensor digiti minimi muscle.
     (Figure635) (Netter434) (Netter431) (Photo6110)

The extensor digiti minimi muscle is slender and often has proximal muscle fibers blending with those of the extensor digitorum muscle rather than being a completely separately muscle. Follow the tendon only as far as the wrist for now.

The distal tendon attaches to the extensor expansion over the phalanges of digit 5 (little finger).

14. Blunt dissect to the most medial of the superficial extensor muscles sharing the common extensor tendon, the extensor carpi ulnaris muscle.
     (Figure635) (Netter434) (Netter431) (Photo6110)

Extensor carpi ulnaris is the most medial of the superficial extensor muscles, attaching to the base of the 5th metacarpal bone. Follow it only as far as the wrist for now.

15. Follow the extensor carpi radialis brevis and longus muscles distally and observe the tendons passing deep to the abductor pollicis longus.
    (Figure636) (Netter435) (Netter431) (Photo6041)

The abductor pollicis longus tendon attaches to the 1st metacarpal bone. Follow it just as far as the wrist for now.

16. Blunt dissect distal to the abductor pollicis longus to identify the extensor pollicis brevis muscle.
    (Figure636) (Netter435) (Netter431) (Photo6041)

Extensor pollicis brevis is adjacent to the abductor pollicis longus muscle. The tendon of extensor pollicis brevis attaches to the proximal phalanx of the 1st digit. Follow it just as far as the wrist for now.

The abductor pollicis longus and extensor pollicis brevis both 'wrap' across the tendons of the extensor carpi radialis brevis and longus. This arrangement can be very useful for identifying the muscles.

17. Distal and medial to the outcropping muscles (abductor pollicis longus and extensor pollicis brevis) is the extensor pollicis longus muscle.
    (Figure636) (Netter435) (Netter431) (Photo6043)

Extensor pollicis longus is most medial of the three muscles acting on the thumb. Extensor pollicis longus attaches to the distal phalanx of the 1st digit. Follow it just as far as the wrist for now.

18. The last of the deep posterior forearm muscles is the extensor indicis muscle, located distal and medial to the extensor pollicis longus muscle.
    (Figure636) (Netter435) (Netter431) (Photo6043)

Extensor indicis acts only on the index finger, the 2nd digit.

PROCEDURE - POSTERIOR HAND (DORSUM)

19. Follow any of the extensor tendons to the wrist where they pass deep to the extensor retinaculum thickening of the antebrachial fascia.
    (Figure639) (Netter459) (Netter460) (Photo6042)

The extensor retinaculum spans across all the extensor tendons. The extensor retinaculum prevents the tendons undergoing a 'bowstringing' when extending the wrist by holding the tendons in against the wrist during movements.

20. Clean the surface of the extensor retinaculum sufficiently to observe the tendons passing under the retinaculum.

Avoid cutting completely through the extensor retinaculum as this will disrupt the tendon organization of the dorsum of the hand by allowing them to 'bowstring' away from the wrist. 

21. Return to the extensor pollicis longus and brevis muscles and follow their tendons down to the dorsal side of the thumb.
     (Figure639) (Netter457) (Netter460)

22. Return to the extensor digitorum muscle and observe that the four tendon slips spread out across the dorsal hand with each passing into a fibrous fascia across the dorsal digits 2-5, the extensor expansion.
    (Figure639) (Netter459) (Netter460) (Photo6042)

The extensor expansion holds the extensor tendons against the phalanges and is a shared anchor for the attachment of many of the tendons acting on the phalanges.

There are multiple fascial 'slips' of the expansion forming these attachment points for the various muscles. The detailed anatomy of the extensor expansion is beyond the scope of anyone other than a hand surgeon. (Figure640) (Netter460)

23. Return to the extensor indicis muscle and follow its tendon which connects into the extensor expansion of the 2nd digit (index finger).
    (Figure639) (Netter460) (Photo6043)

PROCEDURE - ELBOW JOINT

24. The following dissection steps on the elbow joint should be performed only on one limb.
    (Figure637) (Netter428)

The elbow joint is a compound hinge joint with humeroulnar, humeroradial, and proximal radioulnar articulations.

In flexion/extension of the elbow the humeroulnar and humeroradial joints act together as a hinge joint.

In pronation/supination of the elbow, the humeroradial and proximal radioulnar joints act as pivots to allow rotation of the radius bone (the ulnar bone is 'fixed' allowing only flexion/extension and does not rotate during pronation/supination).

Stability of the elbow joint depends on the configuration of the bones, ligaments and to some extent on the surrounding muscles.

25. In the cubital fossa, retract the brachial artery laterally and clean any fascia away from the biceps brachii and brachialis tendons.
    (Photo6091)

26. Using a Weitlaner retractor, forcibly spread the space between the biceps brachii and brachialis tendons to expose the surface of the elbow joint capsule.
    (Figure638) (Netter428)(Photo6092)

The joint capsule is thin anteriorly and posteriorly, but thicker laterally and medially. These thickenings are the ulnar collateral ligament and radial collateral ligament which reinforce the joint and resist abduction/adduction at the joint.
(Photo6046) (Photo6047)

The capsule of the joint also extends to cover the proximal radioulnar joint between the head of the radius and the radial notch of the ulna.

27. Place your fingers against the anterior elbow capsule and flex the forearm.

You should be able to feel where the radius and ulnar bones articulate with the humerus.

28. At the articulation point between the radius/ulna and humerus, make a transverse cut through the anterior surface of the capsule.
    (Figure638a) (Netter428) (Photo6093)

29. Cut away capsule tissue proximal and distal to observe the smooth articular surfaces of the humerus with the radius (humeroradial joint).
    (Figure638a) (Netter428) (Photo6094)

The head of the radius is covered by thin anterior capsule tissue (cut away here). The neck of the radius bone is wrapped by the thicker annular ligament.

The annular ligament is a strong band of fibrous connective tissue thickening that encircles the head of the radius keeping the radius in contact with the ulna (radioulnar joint) while allowing free rotation of the radius. 

A common elbow dislocation is a radial head subluxation. This condition is most common in children. Yanking excessively hard on a child's hand can pull the radial head out of the annular ligament, causing what is colloquially known as 'nursemaids elbow'. The radial head can be pushed back into position with a specific series of reduction motions of the forearm.

30. Rotate the donor's hand back and forth in pronation and supination such that you can observe the rotation of the head of the radius.
    (Figure638) (Netter428) (Photo6094)

31. Extend the capsule incision medially to expose the humeroulnar joint.
    (Figure638) (Netter428) (Photo6095) (Photo6069)

If the brachialis muscle is large, it may be necessary to cut or partially detach the edge of the brachialis muscle to allow the joint capsule to be exposed.

PROCEDURE - WRIST JOINT

32. Do not dissect the wrist joint  but examine the organization from your atlas.
    (Figure641) (Netter445)

The wrist joint is a series of articulating surfaces making a joint complex, rather than a single point of contact. The major articulations are between the radius and ulna (distal radioulnar joint) and the radius with the carpal bones (radiocarpal joint). These joints are stabilized by an articular cartilage disk between the bones at the distal pole of the ulna.

PROCEDURE - CARPAL JOINTS

33. Do not dissect the carpal joints but examine their organization from your atlas.
    (Netter448)

The intercarpal articulations are gliding joints between the proximal and distal rows of carpal bones and between individual carpal bones themselves which contribute to the flexibility of the hand.

A complex of ligaments supports these joints, with one of the most important being the scapholunate (scaphoid to lunate bones). The scapholunate ligament is commonly injured in a Fall On Out Stretched Hands (FOOSH) or with degenerative tears in aging.

PROCEDURE - DIGIT JOINTS

34. Do not dissect the digit joints but examine their organization from your atlas.
    (Netter448)

Carpometacarpal joints - These are articulations between the carpal and metacarpal bones.

Metacarpophalangeal joints - The joints are synovial joints between metacarpal and phalanx bones.

Interphalangeal joints - These are synovial joints formed between the phalanx bones.

CHECKLIST

Skeletal Structures

Radius

Ulna
    Olecranon process

Carpal bones
    Scaphoid
    Lunate

Metacarpal bones (digits 1-5)

Phalanges
    Digits 2-5 (fingers)
        Proximal
        Middle
        Distal
    Digit 1 (thumb)
        Proximal
        Distal

Soft Structures

Extensor retinaculum

Posterior forearm superficial
    Brachioradialis muscle & tendon
    Extensor carpi radialis longus muscle & tendon
    Extensor carpi radialis brevis muscle & tendon
    Extensor digitorum muscle & tendon
    Extensor digiti minimi muscle & tendon
    Extensor carpi ulnaris muscle & tendon

Posterior forearm deep
    Abductor pollicis longus muscle & tendon
    Extensor pollicis brevis muscle & tendon
    Extensor pollicis longus muscle & tendon
    Extensor indicis muscle & tendon

Extensor expansion

Elbow joint
    Humeroulnar
    Humeroradial
    Proximal radioulnar joint
    Annular ligament