Lab Manual - Flexor Compartment of the Forearm, Superficial Hand, and Elbow Joint
Upon completion of this session, the student will be able to:
1. Review the bony landmarks. (Play movie; View images: N 420, 421, 436, 439, 440, 450, 451, 452, 456, TG 2-03A, 2-03B, 2-04, 2-21, 2-22, 2-31, 2-32)
Review bony processes of the humerus, radius and ulna previously examined. Identify supinator crest, posterior border, and interosseous crest of ulna. Identify the dorsal radial tubercle and interosseous crest of radius. Locate grooves at the distal end of radius which accommodate tendons as they cross the wrist. Examine an articulated hand, noting arrangements of carpals, metacarpals, and phalanges. Identify proximal, middle and distal phalanges.
Bones of the elbow
Bones of the elbow
Bones of the forearm
Bones of the forearm
Bones of the wrist
Review radius and ulna and general arrangement of carpals, metacarpals, and phalanges in an articulated hand. Identify the scaphoid, lunate,triquetrum, pisiform, trapezium, trapezoid, capitate, hamate, and hook of hamate. (Handy Mnemonic: Some Lovers Try Positions That They Can't Handle)
Examine the anterior part of the antebrachial fascia and, in its distal part, the palmar carpal ligament spanning between the distal end of the radius and ulna. Note differences between this and the extensor retinaculum. What muscles lie within this fascial plane? What muscles lie deep to it? Where are the arteries, veins and nerves in relation to it? With what is it continuous distally? Remove the antebrachial fascia, leaving the palmar carpal ligament intact.
2. On flexor side of forearm, separate and dissect the various muscular layers and trace the median and ulnar nerves. (Play movie; View images: N434, 445, 446, 447, 448, 449, 450, 451, 460, 461, 465, 466, 468, 472, 475, 476, 481, TG 2-19, 2-21, 2-22, 2-23, 2-24, 2-25, 2-27A, 2-27B, 2-28B, 2-28C2-30, 2-33, 2-34, 2-36, 2-37A, 2-37B2-38, 2-39, 2-40, 2-41, 2-48, 2-49A, 2-49B, 2-51A, 2-51B)
The forearm flexor muscles are arranged in three layers. Dissect each layer separately.
LAYER 1. Pronator teres. Note two heads of origin, relation of median nerve. What structures cross its insertion? The tendons of flexor carpi radialis,palmaris longus, and flexor carpi ulnaris lie within the palmar carpal ligament at the wrist. Trace them through the palmar carpal ligament. Note points of insertion on a skeleton, but do not trace the tendons into the palm. Do you have a palmaris longus? The flexor carpi ulnaris has two heads of origin; note the ulnar nerve entering the forearm between these two heads. Cut the insertion of pronator teres from the radius, leaving a short (1 cm) stump, and reflect toward the ulnar border of the forearm to expose the next (second) layer of muscle. This maneuver also reveals the deep head of pronator teres and the course of the median nerve between the two heads. Do any structures lie between the first two layers of muscles?
LAYER 2. Flexor digitorum superficialis. Trace its origin along the oblique line of the radius to the coronoid process of the ulna and to the medial epicondyle of the humerus. Note the fibrous arch spanning between radius and ulna. What passes beneath this arch? Trace three or four tendons as they pass beneath the palmar carpal ligament. Do not trace into palm. What is their arrangement? Locate the median nerve in relation to the tendons at the wrist.
LAYER 3. Incise the radial origin of flexor digitorum superficialis and reflect. Dissect flexor pollicis longus, flexor digitorum profundus and pronator quadratus (deep to the tendons of the above muscles). Trace tendons to the wrist but do not invade the palm. Compare the arrangement of the tendons of flexor digitorum superficialis and profundus as they enter the wrist. Note the anterior interosseous artery, vein and nerve.
Return to the cubital fossa and trace the brachial artery as it divides into radial and ulnar arteries. Where is the point of bifurcation? Trace the radial artery. Define its course and relations. Follow the radial artery as it courses through the "anatomical snuffbox" to the dorsum of the hand.
NOTE specifically the relations at the wrist between the radial artery and the flexor carpi radialis and the brachioradialis in the palmar carpal ligament. This is a pulse point. Palpate on your partners. The grouping of the radial artery and superficial radial nerve under cover of brachioradialis constitutes a convenient dividing line between forearm flexor and extensor muscle groups.
Follow the ulnar artery, noting course and specific relations to median and ulnar nerves and to muscles. Locate it at the wrist between the flexor carpi ulnaris and flexor digitorum superficialis, deep to the palmar carpal ligament. This is a pulse point; palpate on your partners. Identify the following branches: common interosseous, anterior interosseous, posterior interosseous; note the muscular branches. Consider the collateral circulation of the elbow between branches of brachial, deep brachial, radial and ulnar arteries. Note the accompanying veins (venae comitantes). Consider the blood supply to the entire forearm.
Median nerve. Trace through the forearm, noting specific relations to pronator teres, the fibrous arch of flexor digitorum superficialis, the ulnar artery, its location between flexor digitorum superficialis and profundus. Where do muscular branches to the flexor muscles arise? Locate precisely at the wrist. Locate theanterior interosseous nerve; where does it arise? What muscles does it supply? Relations?
Ulnar nerve. Trace through the forearm; note specific relations to flexor carpi ulnaris, to flexor digitorum superficialis and profundus, and to the ulnar artery. Precisely locate at the wrist. What muscles does it supply? Where do these branches leave the ulnar nerve? Locate the dorsal cutaneous branch of the ulnar nerve (previous dissection). Organize the innervation of the muscles of the forearm into simple groupings.
3. Open the hand, look at creases, and skin the palm (do not cut the recurrent branch of median n.). (Play movie; View images: N 447, 448, 459, 460,461, 465, 466, 468, 472A, 472B, 459, 460, 462, TG 2-24, 2-25, 2-33A, 2-33B, 2-34A, 2-34B, 2-38A, 2-38B, 2-40)
PALM OF THE HAND. Remove the skin from the palm of the hand. If the digits are more than slightly flexed, it is difficult if not impossible to dissect the digits and palm. To make the dissection easier, the flexor digitorum superficialis and profundus and flexor pollicis longus should be transected in the forearm. Sever them at different levels (proximal to distal) so that their tendons can be distinguished from each other. Be careful not to cut the median nerve directly beneath flexor digitorum superficialis. It should then be possible to straighten the digits, thus making the dissection easier. Note the dense attachment to deep fascia and dense subcutaneous tissue.
Locate the palmar digital branches of the median and ulnar nerves along the borders of the digits. Determine area of distribution. Do they supply any portion of the dorsal side of the digit? How much? Significance? What do they accompany?
Scrape the subcutaneous fat from the deep fascia of the palm. In the thenar eminence do not clean completely down to the muscle until the recurrent (motor) branch of the median nerve has been located. Define the parts of the deep fascia: thenar fascia, hypothenar fascia, palmar aponeurosis and fibrous flexor digital sheaths. Characterize each, define boundaries and extent.
Palmar aponeurosis. Using a sharp scalpel, clean its surface thoroughly to display fibrous structure and orientation of fibers. What is its relation to palmaris longus, the palmar carpal ligament and the flexor retinaculum? Identify the superficial transverse metacarpal ligament and transverse fasciculi; note the gaps between them. What can be seen in these gaps? Note the digital fibers extending to the sides of the digits and the flexor digital sheaths.
4. Reflect the palmar aponeurosis distalward and identify neurovascular structures. (Play movie; View images: N 447, 448, 459, 460, 461, 462, 465,466, 468, 462, 459, 460, 462, TG 2-33, 2-34, 2-36, 2-37A, 2-37B, 2-38, 2-39, 2-40)
Clean the subcutaneous fat from the digits and expose the fibrous flexor digital sheaths. Note attachments and structures.
Reflect the palmar aponeurosis distalward, separating it from the palmaris longus and the flexor retinaculum, defining the distal border of the latter. As you reflect, note the septa at its medial and lateral margins that extend to the second and fifth metacarpals. Continue reflecting and note septa extending to metacarpals II-V. These form compartments for the flexor tendons in the central compartment of the palm. What is the carpal tunnel and its associated syndrome?
Pick up the median nerve at the proximal border of the flexor retinaculum then cut the retinaculum following the median nerve to the distal border of the flexor retinaculum. Identify the recurrent (motor) branch of the median nerve at the distal border of the flexor retinaculum; trace it into the thenar muscles. Trace the superficial palmar branch of the radial artery to the thenar compartment. Does it continue beyond? Where? Define the common and proper digital branches of the median nerve, and areas of distribution. How do median and ulnar nerves share in the cutaneous innervation of the digits (review)? Note the change in relationship of palmar nerves and arteries as they reach the digits.
Trace the ulnar artery and nerve into the palm across the flexor retinaculum to the interval between the hook of the hamate and the pisiform. Note their bifurcation here. Trace the superficial ulnar artery into the superficial palmar arterial arch; note its position, relation, and distribution (common and proper digital arteries). What artery completes the superficial palmar arterial arch? Trace the superficial ulnar nerve into common and proper digital nerves. (Review pattern of distribution.)
5. Examine the muscles of the thenar and hypothenar compartments. (Play movie; View images: N 461, 462, 465, 466, TG 2-34A, 2-34B, 2-35, 2-37, 2-38)
Consider the basic compartmental structure of the hand and dissect each compartment separately (thenar compartment, hypothenar compartment, central compartment, adductor-interosseous compartment).
Examine the thenar fascia; open and remove. Dissect abductor pollicis brevis and flexor pollicis brevis. Does the flexor pollicis brevis have a deep head? Examine opponens pollicis (deep to the other thenar muscles) and the insertion of adductor pollicis (not a thenar compartment muscle). Note the position of the tendon of flexor pollicis longus surrounded by the radial bursa.
Examine the hypothenar fascia; open and remove. Dissect abductor digiti minimi, flexor digiti minimi (brevis), and opponens digiti minimi. Innervation of hypothenar muscles? Note relations of the deep ulnar nerve and artery to the origins of these muscles.
6. Cut the flexor retinaculum and pull the long flexor tendons toward the fingertips. (Play movie; View images: N 450, 450, 460, 461, 462, 463, 464,465, 466, 475, TG 2-21, 2-31, 2-34A, 2-34B, 2-35, 2-37A, 2-37B, 2-38, 2-45, 2-48)
Examine the flexor retinaculum. Determine its attachments and extent. Review its relationships with the palmar carpal ligament, palmaris longus and palmar aponeurosis. Examine the contents of the carpal tunnel. How is it formed? Examine tendons of flexor digitorum superficialis and profundus; note their relative positions in the canal and the ulnar bursa. Into which digital sheath does the bursa continue distally? Pull the long flexor tendons toward the fingers from beneath the superficial palmar arterial arch and trace the tendons of the long flexors to the flexor digital sheaths. Incise a sheath longitudinally, noting the synovial lining and the manner of insertion of flexor digitorum superficialis and profundus tendons into the middle and distal phalanges, respectively. What are vincula? If you have not already done so, cut the tendons of flexor digitorum superficialis and profundus near the wrist (but at different distances from the retinaculum), pull distally and separate. Identify the lumbrical muscles, noting origin; trace to their insertion into extensor expansions; innervation? Consider function.
Return to the carpal tunnel and trace the flexor pollicis longus tendon to its insertion. Note the radial bursa.
Locate the flexor carpi radialis tendon. Is it in the carpal tunnel? What happens to it? Trace it to its insertion. Trace the median nerve and bring all of its branches in the hand into continuity (motor and sensory).
Pull the tendons of the long flexors distally to expose the adductor-interosseous compartment. Clean the adductor pollicis muscle and identify its oblique andtransverse heads. Clear the anterior interosseous fascia from interosseous muscles and identify the deep palmar arterial arch; note the accompanying deep branch of the ulnar nerve.
Plastinated specimens are available for the study of joints. Review joints on plastinated speciments. If you wish to perform joint dissections, please do so on one limb only.
7. Open the elbow by removing the anterior and posterior capsules. (Play movie; View images: N 431, 432, 438, 438, 439, 454, 455, TG 2-17, 2-18, 2-43A, 2-43BC, 2-44A, 2-44B, 2-44C)
Elbow joint. The elbow joint consists of the humeroulnar, humeroradial (true elbow articulations), and the proximal radioulnar articulation. Though contained in a single cavity, they move independently.
Remove the muscles on both the posterior and anterior surfaces of the joint. Do not enter the joint cavity at this time. Examine carefully the biceps tendon at its insertion, noting associated bursae and dual action at elbow joint and proximal radioulnar joint. Clean the capsule and define the ulnar collateral, radial collateral and annular ligaments. Remove the capsule anteriorly and posteriorly to expose the joint surfaces, leaving the ligaments intact. Examine actions. Consider the action of pronators and supinators. What is a "pulled elbow"?
Examine the interosseous membrane and note the direction of its fibers. What is the significance of their direction? Examine the distal radioulnar joint and its articular disc. Determine the action of the proximal radioulnar joint and its axis of rotation. Do the same for the distal radioulnar joint. How does the combined motion of these two joints affect the position of the hand?
8. Dissect the wrist by making a frontal section through the distal radius and ulna, carpals and proximal metacarpals. (Play movie; View images: N 453, 454, 455A, 455B, 458, TG 2-44A, 2-44B, 2-44C, 2-45)
Radiocarpal (wrist) joint. Remove all tendons and muscles of the wrist and hand, and identify the capsule, dorsal radiocarpal, palmar radiocarpal, ulnar collateral and radial collateral ligaments.
Section the wrist in the frontal plane, in the following manner. Flex the wrist and hand. Saw through the distal end of the radius and ulna, continuing through both the proximal and distal rows of carpals and the proximal end of the four ulnar metacarpals. The procedure may require sawing in more than one plane to expose all joints. This section exposes the distal radioulnar, the radiocarpal, the intercarpal, midcarpal, carpometacarpal, and the intermetacarpal articulations. Note the extent of each synovial cavity and the interosseous intercarpal ligaments. Consider the combined actions of the "greater wrist" in flexion, extension, adduction, abduction, and circumduction. How do these articulations combine to provide these actions at the "wrist"?
Examine the carpometacarpal articulation of the thumb (saddle type).
Examine the deep transverse metacarpal ligaments. Note that each one lies between interosseous and lumbrical muscle tendons for that digit. What are their relationships to the extensor expansion and fibrous flexor sheath? Open any of the metacarpophalangeal and interphalangeal joints, noting the capsule and collateral ligaments.
|Copyright© 2000 The University of Michigan. Unauthorized use prohibited.|