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Forearm (Antebrachium)


Atlas References

  • Netter: 430–440, 463–469

  • McMinn: 148–153

  • Gray's Atlas: 424, 430–439, 457–459

Before You Begin

Palpate the following bony landmarks on the cadaver or on yourself:

  • Lateral and medial epicondyles of the humerus

  • Styloid process of the radius

  • Head, styloid process, olecranon, and shaft of the ulna

  • Carpal bones

Getting Started

  • o

    Continue the incision from the lateral side of the shoulder with a vertical incision across the length of the forearm toward the wrist.

  • o

    Make an encircling incision around the wrist ( Fig. 8.1 ).

    Fig. 8.1, Skin incisions for arm and forearm dissections.

  • o

    Reflect the skin medially from the anterior compartment of the forearm, and expose the antebrachial fascia and the extensor retinaculum ( Fig. 8.2 ).

    Fig. 8.2, Lateral arm and posterior forearm view with skin reflected, demonstrating superficial structures.

  • o

    Identify the posterior cutaneous nerve of the forearm (posterior antebrachial nerve) (see Fig. 8.2 ).

  • o

    Identify the lateral cutaneous nerve to the forearm (lateral antebrachial cutaneous nerve) , and medial cutaneous nerve to the forearm (medial antebrachial cutaneous nerve) ( Fig. 8.3 ).

    Fig. 8.3, Lateral arm view with skin reflected, demonstrating superficial structures.

Dissection Tip

Preserve as many of the cutaneous nerve branches as possible. Typically, the posterior cutaneous nerve to the forearm emerges between the triceps brachii and brachialis muscles; the lateral cutaneous nerve to the forearm emerges lateral to the bicipital aponeurosis between the biceps brachii and brachioradialis muscles; and the medial cutaneous nerve to the forearm can be traced proximally to the medial cord of the brachial plexus.

Cubital Fossa

  • o

    Reflect the skin over the bicipital aponeurosis, and expose the cubital fossa. The biceps brachii tendon enters the cubital fossa as an aponeurotic expansion.

  • o

    Remove the deep fascia and the fat on the anterior surface of the cubital fossa, preserving the bicipital aponeurosis.

  • o

    Observe how the lateral and medial cutaneous nerves to the forearm relate to the bicipital aponeurosis ( Fig. 8.4 ).

    Fig. 8.4, Cubital region with skin reflected, showing superficial structures.

  • o

    Lateral to the tendon of the biceps brachii, separate the brachioradialis muscle from the brachialis muscle, and identify the radial nerve as it enters the forearm.

  • o

    Reflect the bicipital aponeurosis laterally, and identify the brachial artery , just deep to the veins of the cubital fossa.

  • o

    Retract the brachial artery laterally, and on its medial side, identify the median nerve .

Lateral Arm and Extensor Compartment

  • o

    Continue the dissection by reflecting the skin over the extensor compartment of the forearm, and identify the distribution of the medial and lateral cutaneous nerves to the forearm ( Fig. 8.5 ).

    Fig. 8.5, Anterior arm and forearm view with skin reflected, demonstrating superficial structures.

  • o

    Identify the superficial branch of the radial nerve just proximal to the lateral side of the wrist ( Fig. 8.6 ).

    Fig. 8.6, Cubital fossa view with skin reflected, showing superficial structures.

  • o

    With a pair of scissors, make a small incision into the antebrachial fascia (deep fascia) near the lateral epicondyle ( Fig. 8.7 ).

    Fig. 8.7, Anterior forearm and cubital fossa view with skin removed, demonstrating fascia.

  • o

    Reflect the antebrachial fascia, and expose the underlying musculature of the extensor compartment of the forearm ( Figs. 8.8 to 8.10 ).

    Fig. 8.8, Posterior forearm with skin removed, showing fascia.

    Fig. 8.9, Posterolateral forearm view with skin removed, demonstrating fascia and superficial structures.

    Fig. 8.10, Posterior forearm view with skin reflected, showing fascia and superficial structures.

  • o

    Remove all remnants of deep fascia covering the extensor surface.

Dissection Tip

Take special care when the deep fascia is removed. In the majority of cases, the deep fascia adheres tightly to the muscles of the extensor compartment ( Fig. 8.11 ). To identify the tendinous insertions of the muscles of the extensor compartment, the skin over the dorsum of the hand also is removed.

Fig. 8.11, Posterior arm and forearm view with skin removed, demonstrating fascia.

  • o

    Make a vertical incision at the midpoint of the wrist to the midline of the 3rd digit ( Fig. 8.12 ).

    Fig. 8.12, Posterior wrist view with skin removed, showing extensor retinaculum.

  • o

    With a pair of forceps, lift the skin over the dorsum of the hand, and detach it from the underlying dermis ( Fig. 8.13 ).

    Fig. 8.13, Posterior wrist view with skin removed, demonstrating extensor retinaculum.

  • o

    Reflect the skin laterally without cutting any of the nerves and tributaries of the dorsal venous arch ( Figs. 8.14 and 8.15 ).

    Fig. 8.14, Posterior hand view after skin reflection.

    Fig. 8.15, Posterior hand and wrist view with skin reflected, demonstrating superficial structures.

  • o

    With a fine pair of scissors, expose the dorsal venous arch ( Fig. 8.16 ).

    Fig. 8.16, Posterior hand and wrist view with skin reflected, showing venous arch.

  • o

    As the subcutaneous tissue is removed, pay special attention to identifying the cutaneous nerves running alongside the dorsal venous arch ( Fig. 8.17 ).

    Fig. 8.17, Posterior hand and wrist view with skin reflected, highlighting superficial nerves and veins.

Dissection Tip

Exposing the dorsal venous arch and the cutaneous nerves on the dorsum of the hand can take some time (see Fig. 8.17 ). If time does not permit, skip this step and remove the subcutaneous tissue, dorsal venous arch, and cutaneous branches en bloc.

  • o

    Continue the reflection of the skin over the 3rd digit ( Fig. 8.18 ).

    Fig. 8.18, Posterior hand and wrist with skin reflected, exposing extensor tendons.

  • o

    Identify the extensor retinaculum, a thick fibrous band of the antebrachial fascia that holds the tendons of the extensor compartment in place ( Fig. 8.19 ).

    Fig. 8.19, Posterior hand and forearm with skin removed, demonstrating superficial structures.

  • o

    Place a probe or scissors underneath the extensor retinaculum ( Fig. 8.20 ), and release it from the underlying tendons.

    Fig. 8.20, Posterior hand and forearm view with skin removed, showing superficial structures.

  • o

    Make a vertical incision, and retract the retinaculum laterally to expose the tendons of the extensor compartment ( Fig. 8.21 ).

    Fig. 8.21, Posterior hand and forearm with skin removed, highlighting superficial structures.

  • o

    Identify the extensor digitorum muscle (see Fig. 8.21 ).

  • o

    Lift its tendons and clean away its tendinous sheath ( Fig. 8.22 ).

    Fig. 8.22, Posterior hand and forearm with skin reflected, demonstrating musculotendinous structures.

  • o

    On the radial side of the extensor digitorum muscle, identify the tendons of the abductor pollicis longus, extensor pollicis brevis , and extensor pollicis longus muscles (see Fig. 8.22 ).

  • o

    On its ulnar side, identify the extensor digiti minimi muscle , which is seen traveling to the 5th digit. In the majority of specimens, this muscle belly is fused with the extensor digitorum muscle ( Fig. 8.23 ).

    Fig. 8.23, Posterior hand and forearm with skin reflected, highlighting musculotendinous structures.

Dissection Tip

In the majority of specimens, the muscle bellies of the abductor pollicis longus and extensor pollicis brevis muscles are fused. Use your scissors to separate them (see Fig. 8.23 ).

  • o

    Lift the extensor digitorum muscle, and identify the extensor indicis muscle deep to it ( Fig. 8.24 ). The extensor indicis typically runs along the ulnar side of the tendon from the extensor digitorum to the 2nd digit.

    Fig. 8.24, Posterior forearm view with brachioradialis muscle reflected, demonstrating muscles and tendons.

  • o

    At the distal third of the forearm, lift the extensor pollicis longus and extensor pollicis brevis muscles, and underneath them, identify the extensor carpi radialis longus and brevis muscles ( Figs. 8.25 and 8.26 ).

    Fig. 8.25, Posterior hand and forearm view with skin reflected.

    Fig. 8.26, Posterior hand and forearm with skin reflected.

  • o

    Medial to the extensor carpi radialis brevis muscle, palpate Lister's (dorsal radial) tubercle ( Fig. 8.27 ).

    Fig. 8.27, Posterior hand and forearm with skin reflected.

  • o

    On the ulnar side of the extensor digitorum, identify the extensor digiti minimi and the extensor carpi ulnaris muscles ( Fig. 8.28 ).

    Fig. 8.28, Anteromedial forearm view, demonstrating ulnar artery and nerves.

  • o

    Follow the extensor carpi ulnaris to the wrist. Cut the extensor retinaculum ( Fig. 8.29 ), and release the tendons underneath it ( Fig. 8.30 ).

    Fig. 8.29, Medial posterior view of wrist, demonstrating superficial structures.

    Fig. 8.30, Medial posterior view of wrist, demonstrating superficial structures.

  • o

    Retract the extensor carpi ulnaris muscle, and separate it from the adjacent extensor digiti minimi muscle ( Figs. 8.31 and 8.32 ).

    Fig. 8.31, Posteromedial view of wrist, showing muscle tendons.

    Fig. 8.32, Posteromedial view of wrist, exposing muscle tendons.

  • o

    On the radial aspect of the proximal part of the forearm, identify and separate the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis , and extensor digitorum muscles ( Fig. 8.33 ).

    Fig. 8.33, Posterior view of upper forearm, highlighting musculature.

  • o

    Lift the brachioradialis from the underlying extensor carpi radialis longus muscle. Use a probe or scissors to complete the separation of these two muscles ( Figs. 8.34 and 8.35 ).

    Fig. 8.34, Posterior upper forearm view, demonstrating musculature.

    Fig. 8.35, Posterior upper forearm view, showing musculature.

  • o

    Reflect or lift the brachioradialis muscle anteriorly, and identify the radial nerve ( Fig. 8.36 ). Lift the brachioradialis muscle to allow maximum exposure of the radial nerve.

    Fig. 8.36, Posterior view of forearm, demonstrating musculature.

  • o

    Clean the radial nerve and identify its division into superficial and deep branches . The superficial branch runs beneath the brachioradialis to reach the dorsum of the hand. The deep branch of the radial nerve runs through the supinator muscle .

  • o

    With a pair of scissors, cut between the fibers of the extensor carpi radialis brevis and extensor digitorum muscles, and expose the supinator muscle lying underneath ( Fig. 8.37 ).

    Fig. 8.37, Posterior view of forearm, showing musculature.

  • o

    Reflect the extensor digitorum away from the supinator muscle to expose the supinator's borders ( Fig. 8.38 ).

    Fig. 8.38, Posterior view with brachioradialis muscle cut, demonstrating radial nerve and supinator muscle.

  • o

    At the inferior border of the supinator, trace and expose the deep radial nerve ( Fig. 8.39 , Plate 8.1 ). With a scalpel, make an incision in the supinator where the deep branch of the radial nerve first enters it ( Fig. 8.40 ).

    Fig. 8.39, Posterior view with brachioradialis muscle cut, showing radial nerve and supinator muscle.

    Plate 8.1, Arteries and nerves of the extensor compartment of the forearm.

    Fig. 8.40, Posterior view with brachioradialis cut, demonstrating supinator muscle.

  • o

    Reflect the supinator, and expose the deep radial nerve ( Fig. 8.41 , Plate 8.2 ).

    Fig. 8.41, Posterior forearm view with brachioradialis cut, demonstrating radial nerve branches, supinator muscle, and posterior interosseous nerve.

    Plate 8.2, Arteries and nerves of the extensor compartment of the forearm (deeper dissection).

  • o

    Make an incision on the posterior border of the ulna, and detach the extensor carpi ulnaris muscle. Look for the emergence of the posterior interosseous artery running parallel to the deep branch of the radial nerve between the radius and the ulna.

Dissection Tip

The recurrent interosseous artery can be found between the anconeus and supinator muscles. Remove the anconeus, which travels from the lateral epicondyle to the lateral aspect of the olecranon. Just beneath it, on the anterior surface of the supinator, identify the recurrent interosseous artery. This artery is usually small and often is cut during routine dissection.

Flexor Compartment

  • o

    After completion of the dissection of the extensor compartment, rotate the upper limb and visualize the flexor compartment ( Fig. 8.42 ).

    Fig. 8.42, Anterior view of arm, forearm, and hand, with dashed lines for incisions.

  • o

    Make a vertical incision across the length of the forearm toward the wrist. Make an encircling incision around the cubital fossa and the wrist (see Fig. 8.42 ).

  • o

    Reflect the skin medially and laterally from the flexor compartment, and expose the antebrachial fascia and the flexor retinaculum ( Fig. 8.43 ). Continue the vertical midline incision toward the 3rd digit. Chapter 9 details the dissection of the hand.

    Fig. 8.43, Anterior view of forearm and hand with skin reflected, demonstrating superficial structures.

  • o

    Identify the venous network in the flexor compartment and in the cubital fossa. Trace the tributaries of the basilic vein.

  • o

    Identify the median cubital vein connecting the basilic and cephalic veins ( Fig. 8.44 ).

    Fig. 8.44, Anterior cubital fossa demonstrating superficial structures.

  • o

    Once you identify the cephalic vein, trace it proximally to the arm. Lateral to the cephalic vein, identify the lateral cutaneous nerve to the forearm, or lateral antebrachial cutaneous nerve .

  • o

    This nerve is the cutaneous branch of musculocutaneous nerve and supplies the lateral aspect of the forearm (see Fig. 8.44 ).

  • o

    Notice the thick, flat connective tissue aponeurosis of the biceps brachii muscle, the bicipital aponeurosis.

  • o

    An easy way to identify the muscles of the forearm is to expose them from the wrist toward the cubital fossa.

  • o

    At the wrist, the tendons of each muscle are fairly evident and require minimal dissection.

  • o

    The following three muscles occupy the superficial layer of the muscles of the flexor compartment.

    • o

      On the radial side of the forearm, identify the flexor carpi radialis muscle ( Fig. 8.45 ). The flexor carpi radialis attaches to the second metacarpal bone, and some of its fibers may radiate to the adjacent 3rd metacarpal.

      Fig. 8.45, Anterior view of forearm and hand showing muscle-tendon units.

    • o

      Medial to the flexor carpi radialis, note the palmaris longus muscle inserting into the palmar aponeurosis.

    • o

      On the ulnar side of the forearm, identify the flexor carpi ulnaris muscle.

Dissection Tip

The palmaris longus muscle is absent in roughly 10% of the population.

  • o

    Dissect out the deep fascia and the connective tissue over the tendons and the muscles of the flexor compartment ( Figs. 8.46 and 8.47 ).

    Fig. 8.46, Anterior forearm and hand demonstrating muscle-tendon units.

    Fig. 8.47, Anterior forearm and hand, highlighting muscle-tendon units.

  • o

    Expose the tendon insertions of the flexor carpi ulnaris and flexor carpi radialis muscles ( Fig. 8.48 ).

    Fig. 8.48, Anterior view of forearm and hand showing muscle-tendon units.

  • o

    Deep to the palmaris longus muscle, note the flexor digitorum superficialis muscle .

  • o

    Retract the flexor carpi ulnaris, and in the space between it and the flexor digitorum superficialis , identify a thick bundle of connective tissue encircling the ulnar artery and nerve ( Fig. 8.49 ).

    Fig. 8.49, Anterior forearm and hand view, demonstrating muscle-tendon units, with traction of flexor carpi ulnaris.

  • o

    With the aid of scissors, separate the connective tissue over the ulnar artery and nerve ( Fig. 8.50 ).

    Fig. 8.50, Anterior view of forearm and wrist demonstrating muscle-tendon units.

  • o

    Further retract the flexor digitorum superficialis muscle, and clean and expose the ulnar artery and nerve along the entire length of the forearm ( Figs. 8.51 and 8.52 ).

    Fig. 8.51, Anterior forearm with traction to flexor digitorum superficialis muscle, showing intermediate layer.

    Fig. 8.52, Anterior forearm noting the flexor carpi ulnaris and palmaris longus muscles.

  • o

    Underneath the flexor digitorum superficialis, identify the flexor digitorum profundus muscle.

  • o

    Clean the loose connective tissue over the flexor digitorum profundus ( Fig. 8.53 ).

    Fig. 8.53, Anterior forearm view with traction to flexor digitorum superficialis muscle, exposing the flexor digitorum profundus.

  • o

    Identify the radial artery between the brachioradialis and flexor carpi radialis muscles ( Fig. 8.54 ).

    Fig. 8.54, Anterolateral view of distal forearm, demonstrating radial neurovascular bundle.

  • o

    Further retract the brachioradialis muscle, and expose the radial artery in the forearm ( Figs. 8.55 and 8.56 ).

    Fig. 8.55, Anteromedial view of forearm with skin reflected, demonstrating radial artery and vein.

    Fig. 8.56, Anterior forearm view with skin reflected, demonstrating radial artery and vein.

  • o

    Parallel to the radial artery, identify and expose the superficial branch of the radial nerve ( Fig. 8.57 ).

    Fig. 8.57, Anterior forearm view, showing radial artery, vein, and nerve.

Dissection Tip

Note the following landmarks in the course of the radial artery:

  • Passes superficial to the pronator teres muscle.

  • Travels deep to the brachioradialis muscle.

At the wrist, the radial artery is found between the tendons of the flexor carpi radialis and the brachioradialis muscles. This point is used to feel the radial pulse or to perform arterial catheterization.

  • o

    The flexor digitorum profundus muscle inserts onto the bases of the distal phalanx of each of the medial four digits.

Dissection Tip

A common variation of the flexor digitorum profundus is that its tendon to the 2nd digit may form an independent muscle. The flexor pollicis longus muscle inserts onto the distal phalanx of the 1st digit.

  • o

    The flexor digitorum superficialis muscle inserts onto the base of the middle phalanx of digits 2 to 5. However, the tendon to the 5th digit may be absent.

  • o

    Expose the radial artery ( Fig. 8.58 ).

    Fig. 8.58, Anterior forearm view with radial artery and traction, demonstrating musculature.

Cubital Fossa and Flexor Compartment

  • o

    Cut the bicipital aponeurosis ( Fig. 8.59 ) to trace the radial artery to its branch point from the brachial artery.

    Fig. 8.59, Anterior view of cubital fossa with bicipital aponeurosis reflected, demonstrating brachial artery and median nerve.

  • o

    Coursing with the ulnar artery, identify the median nerve, and the vena comitans ( Fig. 8.60 ).

    Fig. 8.60, Anterior cubital fossa view with bicipital aponeurosis reflected, highlighting brachial artery and median nerve.

  • o

    Lift the brachial and radial arteries, and expose the ulnar artery with its branches ( Fig. 8.61 ).

    Fig. 8.61, Anterior view of cubital fossa with bicipital aponeurosis cut, demonstrating the bifurcation of the brachial artery.

  • o

    At this point, use a retractor between the brachioradialis and the flexor digitorum superficialis muscles to expose deeper structures ( Fig. 8.62 ).

    Fig. 8.62, Anterior cubital fossa view with bicipital aponeurosis reflected, exposing neurovascular structures.

  • o

    Follow the course of the ulnar and radial arteries, and identify the recurrent ulnar and recurrent radial arteries.

  • o

    Identify the pronator teres and its two heads; the humeral (superficial) head is attached to the medial epicondyle and the ulnar (deep) head to the coronoid process of the ulna.

  • o

    Trace the course of the medial nerve as it travels from the cubital fossa and then enters the forearm between the two heads of the pronator teres (see Fig. 8.62 ).

  • o

    Note the ulnar artery entering the forearm deep to the ulnar (deep) head of the pronator teres muscle (see Fig. 8.62 ).

  • o

    Lift up the median nerve, and identify its muscular branches ( Fig. 8.63 ).

    Fig. 8.63, Cubital fossa view with bicipital aponeurosis reflected, demonstrating neurovascular structures.

Dissection Tip

To continue the dissection, the vena comitans must be removed ( Fig. 8.64 ). Cut the veins in the cubital fossa and as distal as possible in the forearm. Use paper towels to absorb any fluid that issues from the cut veins.

Fig. 8.64, Anterior view of cubital fossa with bicipital aponeurosis reflected, highlighting neurovascular structures.

  • o

    Expose the borders of the pronator teres, and retract the radial artery ( Fig. 8.65 ).

    Fig. 8.65, Anterolateral forearm view with skin reflected, demonstrating radial artery and musculature.

  • o

    Carefully split the humeral head of the pronator teres ( Fig. 8.66 ) from the underlying ulnar (deep) head and flexor digitorum superficialis muscle ( Figs. 8.67 and 8.68 ).

    Fig. 8.66, Anterior cubital fossa with bicipital aponeurosis cut, exposing median nerve, radial artery, and pronator teres muscle.

    Fig. 8.67, Anterior view of lateral cubital fossa and forearm with reflected pronator teres, demonstrating musculature.

    Fig. 8.68, Anterior cubital fossa view with pronator teres muscle reflected, demonstrating deeper structures.

  • o

    Lift the median nerve and expose its course in the deep flexor compartment of the forearm ( Fig. 8.69 ).

    Fig. 8.69, Anterior cubital fossa view with superficial (humeral) head of pronator teres muscle reflected, and median nerve traction demonstrating deep (ulnar) head of pronator teres.

  • o

    Dissect distally the ulnar artery and identify the common interosseous artery ( Fig. 8.70 ).

    Fig. 8.70, Anterior cubital fossa view with superficial pronator teres head reflected, and median nerve traction demonstrating deep pronator teres head, and radial and ulnar arteries.

  • o

    The common interosseous artery arises from the ulnar artery and then divides into the anterior and posterior interosseous branches ( Fig. 8.71 ).

    Fig. 8.71, Anterior cubital fossa view with superficial head of pronator teres reflected, and median nerve traction demonstrating deep head of pronator teres and radial and ulnar arteries.

  • o

    The posterior interosseous artery passes through the interosseous membrane to reach the extensor compartment of the forearm.

  • o

    As the median nerve is lifted, identify the anterior interosseous nerve, which arises from the median nerve just proximal to the pronator teres muscle (see Figs. 8.70 and 8.71 , Plate 8.3 ).

    Plate 8.3, Arteries and nerve of the flexor compartment of the forearm.

Deep Flexor Compartment

  • o

    Cut the tendons of the flexor digitorum superficialis, or widely retract them, and identify the flexor digitorum profundus and flexor pollicis longus muscles ( Fig. 8.72 ).

    Fig. 8.72, Anterior forearm view with superficial and intermediate muscle layers cut and reflected, exposing deeper structures.

  • o

    Finally, identify the pronator quadratus , which connects the distal portions of the ulna and radius ( Fig. 8.73 ).

    Fig. 8.73, Anterior view of forearm with superficial and intermediate muscle layers cut and reflected, demonstrating deeper structures.

  • o

    In the space between the flexor pollicis longus and flexor digitorum profundus muscles, trace the course of the anterior interosseous artery and anterior interosseous nerve, a branch of the median nerve (see Figs. 8.72 and 8.73 ).

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