Download Click on the link(s) to view your course **Netter: Shoulder and Arm

Anatomy Extravaganza of the Upper Extremity
4.0 contact hours or .4 AOTA CEUs
Editor: Walter B. Greene, MD
Illustrated by: Frank H. Netter, MD
EHT Instructors:
Nancy Falkenstein, OTR/L, CHT and Susan Weiss OTR/L, CHT
Click on SECTIONS (below) to View your Course:
Description:
This course is in written format. This is a mixed level learning course teaching the clinician an abundance
of upper extremity anatomy details. View amazing Netter photographs and learn anatomy biomechanics,
physical exam as well as a wide array of various disorders from the shoulder to the hand. The detailed
photographs in this book will increase your understanding of fractures, bone anatomy, nerve compressions,
the brachial plexus, muscular structures and more. You can print the chapters out and have a wonderful
anatomy reference booklet to use in the clinic. This jammed packed anatomy course is priced right making
it a fantastic way to earn CEU’s for less. Used with permission from Elsevier/Mosby.
Objectives:
*Review the pertinent basic science of the more common clinical disorders of the
shoulder, elbow wrist and hand.
*Review rotator cuff pathology and treatment regimes
*Introduce shoulder arthritis and intervention techniques
*Review nerve entrapment syndromes and brachial plexus injuries
*Learn about fractures of the proximal humerus, clavicle and scapula
*Review the nerves passing the elbow and the various nerve entrapments
*Learn about elbow arthritis, lateral epicondylitis, medial epicondylitis, and fractures
about the elbow
*Introduce hand anatomy and biomechanics
*Review physical examination of the hand
*Introduce the student to osteoarthritis of the hand, Kienbocks’s disease, tendonitis,
*Dupuytren’s disease, ganglia, nerve entrapments, wounds, tendon injuries and
*fractures
*Introduce to pediatric conditions and congenital anomalies
Sections: Click on the link(s) to view your course
**Netter: Shoulder and Arm
**Netter: Elbow and Forearm
**Netter: Hand and Wrist
Chapter 14
T
he purpose of this chapter is to review the pertinent basic science of the more
common clinical disorders of the shoulder.
tion. The anterior half of the deltoid elevates
(flexes) the shoulder, and the posterior half
provides extension. Underneath the deltoid
are the four rotator cuff muscles: the subscapularis, located anteriorly; the supraspinatus, located superiorly; and the infraspinatus
and teres minor muscles, located posteriorly.
The deltoid provides most of the power in
shoulder motion, whereas the rotator cuff
muscles act as a force couple to fine-tune and
enhance the efficiency and stability of shoulder motion by compressing, depressing, and
thus maintaining the humeral head in the
glenoid fossa. Other important shoulder
muscles include the trapezius, the latissimus
dorsi, the serratus anterior, and the pectoralis
major.
The subclavian artery passes under the clavicle and continues as the axillary artery as it traverses the anterior aspect of the shoulder
joint. Anastomoses of branches of the axillary
artery provide important collateral circulation
to the upper extremity (Figure 14-4). The main
blood supply to the humeral head is the anterior humeral circumflex artery. The nerves
about the shoulder include the brachial plexus
and its terminal branches, the sympathetic
nerves, the supraclavicular nerves, and cranial
nerve XI.
Important posterior landmarks include the
quadrangular space and the triangular interval (Figure 14-5). The quadrangular space is
bordered by the long head of the triceps, the
surgical neck of the humerus, the inferior border of the scapula, and the teres major. The
axillary nerve and the posterior humeral
circumflex artery fill this space. The triangular
interval houses the radial nerve and the
deep brachial artery. Its borders are the teres
major superiorly, the long head of the triceps
medially, and the lateral head of the triceps
laterally.
ANATOMY AND BIOMECHANICS
The shoulder girdle includes three bones
(the scapula, clavicle, and humerus) and three
joints (the glenohumeral, acromioclavicular
[AC], and sternoclavicular [SC] joints). The
scapulothoracic articulation is also considered
part of the shoulder girdle. For every 2° of
glenohumeral motion, approximately 1° of
scapulothoracic motion occurs. The AC and
SC joints also participate in this scapulohumeral rhythm. As a result of this coordinated
movement, the shoulder has a greater range of
motion than any other joint in the body.
The scapula is a triangular, flat bone that
is surrounded by muscle (Figures 14-1 and
14-2). Its curved coracoid process projects anteriorly from the superior border and is the
site of origin for the coracobrachialis and
the short head of the biceps muscle. The
other notable scapular prominence is the
acromion, a spinelike process on the posterior aspect. The coracoacromial ligament
stabilizes the humeral head in the superior direction. The two coracoclavicular ligaments
prevent the clavicle from riding superiorly.
The clavicle is an S-shaped tubular bone that
articulates with the acromion laterally and the
manubrium medially.
The proximal end of the humerus includes
the humeral head, the greater and lesser
tuberosities, and the humeral neck. The head
of the humerus is retroverted, or posteriorly
angled, approximately 30° to match the anterior position of the scapula as it rests on the
thoracic cavity. The pear-shaped glenoid
fossa articulates with the humerus in a neutral
or slightly retroverted position. The glenoid
labrum is a rim of fibrocartilaginous tissue that
increases the surface area of the glenoid fossa
and the stability of the shoulder (Figure 14-3).
The deltoid is a large, powerful muscle
whose primary function is shoulder abduc-
284
The Shoulder and Arm
Figure 14-1: Anterior View Scapula and Proximal Humerus
Acromion
Coracoid process
Clavicle (cut)
Superior angle
Superior border
Anatomic neck
Suprascapular notch
Greater tubercle
Neck
Lesser tubercle
Medial border
Surgical neck
Subscapular fossa
Intertubercular
sulcus
Crest of
greater tubercle
Crest of
lesser tubercle
Deltoid tuberosity
Glenoid
Lateral border
Head of
humerus
Humerus
Trapezius muscle
Inferior angle
Scapula
Pectoralis minor muscle
Omohyoid muscle
Deltoid muscle
Biceps brachii muscle
(long head)
Muscle attachments
Origins
Insertions
Supraspinatus muscle
Subscapularis muscle
Coracobrachialis muscle
and
Biceps brachii muscle
(short head)
Pectoralis major muscle
Latissimus dorsi muscle
Triceps
brachii
muscle
(long head)
Teres major muscle
Deltoid muscle
Subscapularis
muscle
Coracobrachialis muscle
Brachialis muscle
Acromioclavicular joint capsule
(incorporating acromioclavicular ligament)
Shoulder joint, anterior view
Clavicle
Trapezoid
Coracoligament
clavicular
Conoid
ligament
ligament
Acromion
Coracoacromial ligament
Supraspinatus tendon (cut)
Coracohumeral ligament
Greater tubercle and
Lesser tubercle
of humerus
Transverse humeral ligament
Superior transverse
scapular ligament and
suprascapular notch
Coracoid process
Intertubercular tendon sheath
(communicates with synovial cavity)
Communications of
subtendinous
bursa of subscapularis
Subscapularis tendon (cut)
Biceps brachii tendon (long head)
Serratus
anterior
muscle
Capsular
ligaments
285
Broken line indicates
position of subtendinous
bursa of subscapularis
Chapter 14
Figure 14-2: Posterior View Scapula and Proximal Humerus
Suprascapular notch
Clavicle (cut)
Coracoid process
Superior border
Acromion
Superior angle
Acromial angle
Supraspinous fossa
Spinoglenoid notch
connecting supraspinous
and infraspinous fossae
Spine
Neck
Greater tubercle
Head of humerus
Infraspinous fossa
Anatomic neck
Medial border
Surgical neck
Lateral border
Inferior angle
Scapula
Deltoid tuberosity
Trapezius
Supraspinatus muscle
muscle
Humerus
Levator
scapulae
muscle
Deltoid muscle
Supraspinatus muscle
Rhomboid
minor
muscle
Infraspinatus muscle
Teres minor muscle
Rhomboid
major
muscle
Infraspinatus
muscle
Latissimus dorsi
muscle (small
slip of origin)
Radial groove
Triceps brachii muscle
(lateral head)
Triceps
brachii
muscle
(long head)
Muscle attachments
Origins
Insertions
Deltoid muscle
Teres minor
muscle
Brachialis muscle
Teres major
muscle
PHYSICAL EXAMINATION
Begin the physical examination with an inspection of the patient’s overall posture and
alignment of the shoulder. Look for swelling
and ecchymosis, which may indicate recent
trauma. Note areas of muscle atrophy suggestive of nerve dysfunction. Injury to cranial nerve
XI results in atrophy of the trapezius muscle,
which is seen superiorly as a reduced neckto-shoulder contour. Supraspinatus nerve dysfunction causes loss of the normal posterior
shoulder contour and prominence of the
scapular spine and acromion.
Next, palpate subcutaneous landmarks to
detect deformity or tenderness. For example,
with an AC separation, the distal end of the
clavicle is prominent. Start at the sternoclavicular joint, and proceed laterally along the clavicle to the acromioclavicular joint. Proceed to
the lateral edge of the acromion and the
greater tuberosity of the proximal humerus.
Also, palpate the long head of the biceps in
the bicipital groove of the proximal humerus
to detect subluxation or tenderness.
Shoulder range of motion is assessed in
four planes (Figure 14-6). The zero starting
286
The Shoulder and Arm
Figure 14-3: Shoulder Joint Opened (lateral view)
Coracoacromial ligament
Acromion
Coracoid process
Supraspinatus tendon
(fused to capsule)
Coracohumeral ligament
Subdeltoid bursa
Biceps brachii tendon (long head)
Infraspinatus tendon
(fused to capsule)
Superior glenohumeral ligament
Subscapularis tendon
(fused to capsule)
Glenoid cavity (cartilage)
Teres minor tendon
(fused to capsule)
Middle glenohumeral
ligament
Insertion of synovium
(enlarged for depiction)
Inferior glenohumeral
ligament
Figure 14-4: Axillary and Brachial Arteries
Acromial branch
Deltoid branch
Clavicular branch
Pectoral branch
Superior thoracic
artery
Thoracoacromial
artery
Axillary artery
Lateral thoracic
artery
Anterior circumflex humeral artery
Subscapular artery
Posterior circumflex humeral artery
Circumflex scapular
artery
Thoracodorsal
artery
Brachial artery
Level of lower margin
of teres major muscle
is landmark for name
change from axillary
to brachial artery
Deep artery of arm
Radial collateral artery
Middle collateral artery
287
Chapter 14
Figure 14-5: Posterior View of Shoulder and Arm
Superficial layer
Acromion
Supraspinatus muscle
Greater tubercle of humerus
Infraspinatus muscle
Teres minor muscle
Axillary nerve and posterior
circumflex humeral artery
Deltoid muscle (cut and reflected)
Superior lateral cutaneous nerve of arm
(from axillary nerve)
Teres major muscle
Long head
Lateral head Triceps brachii muscle
Tendon
Posterior cutaneous
nerve of arm
(from radial nerve)
Medial intermuscular septum
Brachioradialis muscle
Ulnar nerve
Medial epicondyle of humerus
Extensor carpi
radialis longus muscle
Olecranon of ulna
Flexor carpi ulnaris muscle
Extensor carpi
radialis brevis muscle
Anconeus muscle
Extensor carpi ulnaris muscle
Extensor digitorum muscle
Posterior cutaneous
nerve of forearm
(from radial nerve)
Capsule of shoulder joint
Supraspinatus tendon
Infraspinatus and
Teres minor tendons (cut)
Axillary nerve
Teres
major
muscle
Long head of
triceps brachii muscle
Lateral head of triceps
brachii muscle (cut)
Medial head of triceps
brachii muscle
Medial epicondyle
of humerus
Ulnar nerve
Olecranon of ulna
Deep layer
Anconeus muscle
288
Posterior circumflex
humeral artery
Superior lateral cutaneous
nerve of arm
Deep artery of arm
Radial nerve
Middle collateral artery
Radial collateral artery
Inferior lateral cutaneous
nerve of arm
Lateral intermuscular
septum
Nerve to anconeus
and lateral head of
triceps brachii muscle
Posterior cutaneous
nerve of forearm
Lateral epicondyle
of humerus
fifteen
Elbow and
Forearm
Edward D. Wang, MD
Lawrence C. Hurst, MD
Chapter 15
spool and fits in the wrench-shaped trochlear
notch. This anatomic configuration, in conjunction with the collateral ligaments, provides a stable hinge joint that can lift heavy
objects. Rotation of the forearm occurs
through the proximal and distal radioulnar articulations.
Distal to the radial head, the bone tapers to
form the radial neck, then flares at the radial
tuberosity—the insertion site of the biceps tendon. Between the radius and the ulna is the
interosseous membrane—a thickened, ligamentous structure that connects the two
ANATOMY
The elbow is a functional link for positioning the hand in space, a fulcrum for the forearm lever, and a load-carrying joint. As such, it
requires a combination of mobility and stability. The three articulations of the elbow provide flexion and extension, as well as forearm
rotation (Figure 15-1). Control and stability of
flexion and extension are provided primarily
through the ulnohumeral (trochlea and olecranon) articulation and secondarily through
the radiohumeral (capitellum and radial head)
articulation. The trochlea is shaped like a
Figure 15-1: Bones of Right Elbow Joint
Humerus
Humerus
Medial
supracondylar ridge
Lateral
supracondylar ridge
Olecranon
fossa
Coronoid
fossa
Medial condyle
Medial epicondyle
Radial fossa
Lateral condyle
Lateral epicondyle
Capitulum
Lateral epicondyle
Trochlea
Groove for
ulnar nerve
Coronoid
process
Head
Neck
Radial notch of ulna
Tuberosity
Radius
Olecranon
Head
Neck
Tuberosity
Tuberosity
Ulna
Radius
Ulna
In extension: anterior view
In extension: posterior view
Humerus
Medial epicondyle
Capitulum
Trochlea
Head
Neck
Radial tuberosity
Humerus
Lateral epicondyle
Capitulum
Head
Neck
Radial tuberosity
Radius
Radial notch
Coronoid process
Trochlear notch
Olecranon
Ulna
Coronoid process
Trochlear notch
Olecranon
of ulna
In 90˚ flexion: lateral view
In 90˚ flexion: medial view
308
Elbow and Forearm
bones in a manner that provides stability
while allowing forearm rotation.
Muscles that cross the elbow anteriorly include the elbow flexors and the flexor-pronator
forearm muscles that originate from the medial
epicondyle (Figure 15-2). In the forearm, the
volar muscles are arranged in three layers. The
superficial group includes the pronator teres,
flexor carpi radialis, palmaris longus, and flexor
carpi ulnaris. The middle layer is the flexor digitorum superficialis. The deep layer comprises
the supinator, flexor digitorum profundus,
flexor pollicis longus, and pronator quadratus.
The flexor-pronator muscle group primarily
provides wrist flexion and forearm pronation.
The biceps is a secondary flexor of the elbow
and a strong supinator. Immediately deep to
the biceps lies the brachialis muscle—the major
flexor of the elbow.
Posterior elbow muscles include elbow extensors, wrist and finger extensors, and the
supinator. Posterior forearm muscles are arranged in two layers. The superficial group
originates from a common tendon at the lateral epicondyle and includes a lateral component (brachioradialis, extensor carpi radialis
longus, and extensor carpi radialis brevis) and
a medial subgroup (extensor digitorum, extensor digiti minimi, extensor carpi ulnaris,
and anconeus). The deep posterior forearm
muscles are the supinator, abductor pollicis
longus, extensor pollicis brevis, and extensor
pollicis longus (see Figure 15-2).
The brachial artery, the main artery of the
arm and elbow, travels in the anterior compartment of the arm adjacent to the median
nerve. Proximal to the elbow, it gives off collateral arteries that help form a rich plexus of vessels around the elbow. At the level of the radial
head, the brachial artery bifurcates into the radial and ulnar arteries. The ulnar artery enters
the forearm posterior to the pronator teres,
whereas the radial artery travels between the
brachioradialis and the supinator muscle.
The median nerve enters the forearm between the humeral and ulnar heads of the
pronator teres and travels inferior to the flexor
digitorum superficialis muscle (Figure 15-3).
The anterior interosseous nerve branches in-
309
nervate the index, and sometimes, the long,
finger component of the flexor digitorum profundus, the flexor pollicis longus, and the
pronator quadratus. Because of the location
of its fibers in the median nerve, isolated
paralysis of the anterior interosseous nerve
may occur with an elbow fracture. The rest of
the median nerve innervates all the volar forearm muscles except the ulnar half of the flexor
digitorum profundus (fourth and fifth fingers)
and the flexor carpi ulnaris, both of which are
supplied by the ulnar nerve.
The ulnar nerve exits the anterior compartment of the arm, passing behind the medial
epicondyle into the cubital tunnel at the elbow, then enters the forearm between the
two heads of the flexor carpi ulnaris (Figure
15-4). It innervates the flexor carpi ulnaris
muscle, the ulnar half of the flexor digitorum
profundus muscle, and, ultimately, the intrinsic muscles of the hand.
In the arm, the radial nerve travels within the
posterior compartment, then enters the anterior compartment lateral to the humerus. In
the antecubital fossa, the radial nerve innervates the brachioradialis and extensor carpi radialis longus before dividing into superficial
(sensory) and deep (mostly motor) branches
(Figure 15-5). The superficial radial nerve provides sensation to the radial dorsal wrist and
hand. The deep branch innervates the remaining extensor muscles of the forearm. It travels
deep and through the supinator muscle and
exits this muscle as the posterior interosseous
nerve. Distal to the radial tuberosity, the deep
branch of the radial nerve may lie “on the
bone” and, as such, is vulnerable to injury in
fractures of the proximal radius or in operations at this site.
PHYSICAL EXAMINATION
Inspect the elbow for swelling and ecchymosis, and determine the carrying angle (the
axial alignment of the humerus and the ulna
with the elbow extended). The normal carrying angle is 10° to 20°, with most studies
observing slightly greater cubitus valgus in
females. Angular deformities may occur secondary to previous trauma, growth distur-
Chapter 15
Figure 15-2: Bony Attachments of Muscles of Forearm
Anterior view
Brachioradialis muscle
Extensor carpi radialis
longus muscle
Extensor carpi radialis
Common
brevis, extensor
extensor
digitorum, extensor
tendon
digiti minimi, extensor
carpi ulnaris muscles
Brachialis muscle
Biceps brachii muscle
Supinator muscle
Flexor digitorum superficialis
muscle (radial head)
Pronator teres muscle
Flexor pollicis
longus muscle
Brachialis muscle
Pronator teres muscle
(humeral head)
Common Pronator teres, flexor carpi
radialis, palmaris longus, flexor
flexor
carpi ulnaris, flexor digitorum
tendon
superficialis (humeroulnar head)
Flexor digitorum superficialis
muscle (humeroulnar head)
Pronator teres muscle
(ulnar head)
Flexor digitorum
profundus muscle
Note: Attachments of instrinsic
muscles of hand not shown
Ulna
Radius
Flexor carpi
ulnaris muscle
(humeral origin
via common
flexor tendon)
Pronator
quadratus
muscle
Pronator quadratus muscle
Brachioradialis muscle
Flexor carpi
ulnaris muscle
Abductor pollicis
longus muscle
Anconeus muscle
Flexor carpi ulnaris
muscle (ulnar origin)
Flexor pollicis
longus muscle
Flexor digitorum
profundus muscle
Flexor digitorum
superficialis muscle
Flexor digitorum
profundus muscle
Triceps brachii muscle
(medial head)
Triceps brachii
tendon
Extensor carpi
ulnaris muscle
Flexor carpi
radialis muscle
Posterior view
Extensor carpi ulnaris
muscle (ulnar origin)
Extensor pollicis
longus muscle
Extensor indicis
muscle
Origins
Ulna
Insertions
Extensor carpi radialis
longus muscle
Extensor carpi radialis
brevis muscle
Extensor carpi
ulnaris muscle
Extensor digitorum
muscle (central bands)
Extensor digiti
minimi muscle
Extensor digitorum
muscle (lateral bands)
310
Biceps brachii
muscle
Supinator muscle
Abducor pollicis
longus muscle
Pronator teres
muscle
Extensor pollicis
brevis muscle
Radius
Brachioradialis
muscle
Abductor pollicis
longus muscle
Extensor pollicis
brevis muscle
Extensor pollicis
longus muscle
Extensor indicis
muscle
Elbow and Forearm
Figure 15-3: Median Nerve
Pronator teres m. (humeral head)
Articular branch
Flexor carpi radialis m.
Median nerve
Palmaris longus m.
Pronator teres m. (ulnar head)
Flexor digitorum superficialis m. (turned up)
Flexor digitorum profundus m.
(lateral portion supplied via anterior
interosseous n.; medial portion by ulnar n.)
Anterior interosseous n.
Flexor pollicis longus m.
Thenar muscles
Pronator quadratus m.
Cutaneous
innervation
Palmar branch
Abductor pollicis brevis
Opponens pollicis
Flexor pollicis brevis
(superficial head;
deep head supplied
by ulnar n.)
Flexor
retinaculum
Anastomotic
branch to
ulnar n.
1st and 2nd lumbrical mm.
Branches to dorsum of
middle and distal phalanges
Common
Proper
bances, or genetic syndromes. Ecchymosis,
swelling, or both about the elbow indicate a
muscle or tendon injury, fracture, or elbow
sprain or dislocation.
Palpate subcutaneous landmarks for sites of
tenderness, deformity, or effusion that indicate the site of occult fracture, tendinosis, ligament sprain, or tendon rupture. From lateral
to medial, the structures in the antecubital
fossa are the biceps tendon, brachial artery,
and median nerve. A palpable defect is key to
diagnosing rupture of the distal biceps tendon
or disruption of the triceps tendon. Joint effusion is best detected in the “soft spot” between the lateral epicondyle, radial head, and
Palmar
digital nn.
olecranon. Tenderness over the radial head or
humeral condyles may indicate an occult fracture that is not visible on radiographs.
The zero starting position for measurement
of elbow motion is a straight extremity (Figure
15-6). Young children commonly extend the
elbow by 10° to 15°, but adults usually cannot
extend the elbow past the zero starting position. The normal range of elbow flexionextension is 0° to 145°. The plane of forearm
rotation is pronation-supination. Pronation literally means “the state of being prone” or, as
it relates to the forearm, “the palm being
turned backward.” Likewise, supination literally means “the state of being supine” (ie, the
311
sixteen
The Hand
and Wrist
John D. Lubahn, MD
D. Patrick Williams, DO
Chapter 16
T
he human hand, as an extension of the brain, allows us to manipulate and interact with our environment and to perform activities as routine as opening a
door or as intimate as caressing a loved one. The hand also functions as part of
the sensory system, providing tactile sensation for complex hand movements
without the necessity of constant visual guidance; this function is epitomized
by blind people who read and musicians who entertain. An understanding and careful examination of hand anatomy and function is crucial for the student of medicine.
carpometacarpal (CMC) joint of the thumb is
saddle-shaped, a configuration that permits
abduction-adduction, as well as the circumduction that permits opposition of the thumb
to the fingers. The metacarpophalangeal
(MP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints basically are
flexion-extension hinge joints.
The skin on the dorsal surface of the hand is
thin and flexible to allow full flexion of the fingers, whereas the palmar surface skin is
thicker and characterized by creases. The
ANATOMY AND BIOMECHANICS
The carpus, or wrist, is composed of eight
carpal bones that link the forearm to the hand
(Figure 16-1). The proximal carpal row
(scaphoid, lunate, and triquetrum) articulates
with the distal radius and ulna, as well as the
distal carpal row (trapezium, trapezoid, capitate, and hamate). The pisiform, also part of
the proximal row, is a sesamoid bone in the
flexor carpi ulnaris tendon that articulates
only with the triquetrum. The bones of the
hand are the metacarpals and phalanges. The
Figure 16-1: Bones and Joints of Hand
Distal
phalanges
Head
Tuberosity
Shafts
Base
Head
Shafts
Base
Middle phalanges
Right hand:
anterior (palmar)
view
Proximal phalanges
Head
Shafts
Base
Metacarpal bones
Head
Shafts
Base
Carpal
bones
5
4
3
Sesamoid
bones
2
1
Hamate and
Hook
Capitate
Trapezoid
Pisiform
Triquetrum
Lunate
336
Trapezium
and
Tubercle
Scaphoid
and
Tubercle
Carpal
bones
The Hand and Wrist
distal volar crease of the wrist crosses the
proximal scaphoid and the pisiform. The distal
palmar crease of the hand corresponds to the
MP joint, and the proximal finger crease is at
the base of the proximal phalanx.
The extrinsic muscles of the wrist and hand
originate on the medial and lateral humeral
condyles and the proximal radius and ulna
(see Figure 15-2). The extrinsic extensor tendons cross the wrist and are surrounded by
tendon sheaths in six compartments bounded
by the extensor retinacular ligament (Figure
16-2). The extrinsic finger and thumb flexor
tendons and the median nerve enter the hand
through the carpal canal (Figure 16-3). The
transverse carpal ligament, a thick band extending from the hamate and pisiform to the
scaphoid and trapezium, forms the inelastic
roof of the carpal canal. A decrease in the size
of the canal or an increase in the size of its
contents can cause compression of the median nerve (carpal tunnel syndrome).
Intrinsic musculature includes thenar, hypothenar, and interosseous muscles (Figure
16-4; see also Figures 15-4 and 15-5). The
thenar muscles are the abductor pollicis
brevis, the opponens pollicis, and the superficial head of the flexor pollicis brevis. The hypothenar muscles are composed of the abductor digiti quinti, the opponens digiti quinti,
and the flexor digiti quinti. The dorsal interossei, commonly referred to as dorsal intrinsics,
abduct the fingers; the palmar interossei (palmar intrinsics) adduct the fingers.
The DIP joint of the fingers is flexed by the
flexor digitorum profundus (FDP). It has a separate muscle belly for the index finger (which
therefore flexes independently) but a common muscle belly for the long, ring, and small
fingers (which tend to work as a single unit).
The PIP joint of the fingers is primarily flexed
by the flexor digitorum superficialis (FDS). It
has individual muscle bellies for each finger,
thus providing the individual finger flexion at
the PIP joint that is necessary for activities
such as playing a musical instrument and typing. The FDS separates into two parts before
its point of insertion, and the FDP passes
through the split (Figure 16-5). Both finger
337
flexors are enclosed in a common tendon
sheath. The proximity of the FDS and FDP tendon to the surrounding sheath promotes efficient movement, but adhesions from injury or
infection can be problematic in this region.
The interossei, along with the lumbrical
muscles, flex the MP joints and extend the PIP
and DIP joints. The lumbrical muscles are
unique in that they originate from the profundus tendons to insert into the dorsal apparatus of the antagonistic extensor mechanism
(see Figure 16-5). The interossei and the two
ulnar lumbricals are innervated by the ulnar
nerve, but the two radial lumbricals are innervated by the median nerve.
The MP joints of the fingers are extended
by the extensor digitorum longus, extensor indicis proprius, and extensor digiti quinti.
When the MP joints are flexed, these muscles
also can extend the PIP joints; otherwise, the
intrinsic muscles extend the PIP and DIP
joints. The complex arrangement of the tendons on the dorsum of the hand provides the
necessary synchrony and balance between
flexors and extensors during the multiple precise motions of the MP, PIP, and DIP joints
working in concert. The main insertion of the
extrinsic extensor muscle tendon is through
the central slip at the base of the middle phalanx. The intrinsic muscles join with the extrinsic extensor through the interdigitating
transverse and oblique fibers of the dorsal apparatus to extend the PIP and DIP joints.
Contracture or spasticity of the intrinsic
muscles creates increased tension on the dorsal hood. A swan-neck deformity develops,
with PIP joint hyperextension and MP and
DIP joint flexion (Figure 16-6). Laceration of
the central extensor tendon proximal to its insertion into the middle phalanx allows the lateral bands to slip volarly and produces the opposite flexion, boutonnière (French from
“button hole”) PIP joint deformity.
The radial artery lies radial to the flexor
carpi radialis tendon at the wrist (see Figure
16-3). After crossing the snuffbox (see Figure
16-2), the radial artery passes through the first
intermetacarpal space to the palm as the
main contributor to the deep palmar arch,
Chapter 16
Figure 16-2: Extensor Tendons at the Wrist
Posterior (dorsal) view
Extensor carpi ulnaris – Compartment 6
Extensor digiti minimi – Compartment 5
Extensor digitorum
Compartment 4
Extensor indicis
Extensor pollicis longus – Compartment 3
Extensor carpi radialis brevis
Extensor carpi radialis longus
Compartment 2
Abductor pollicis longus
Compartment 1
Extensor pollicis brevis
Plane of cross section
shown below
Extensor retinaculum
Radial artery in
anatomical snuffbox
Abductor digiti
minimi muscle
Dorsal interosseous muscles
Intertendinous
connections
Transverse fibers of
extensor expansions (hoods)
Cross section of most distal portion of forearm
Extensor retinaculum
Extensor pollicis longus – Compartment 3
Compartment 4
Compartment 5
Compartment 6
Extensor digitorum and
extensor indicis
Extensor carpi
radialis brevis
Extensor carpi
radialis longus
Extensor
digiti minimi
Extensor
carpi
ulnaris
5
4
3
6
2
1
Ulna
Radius
338
Compartment 2
Extensor
pollicis brevis
Abductor
pollicis longus
Compartment 1
The Hand and Wrist
Figure 16-3: Flexor Tendons, Arteries, and Nerves at Wrist
Palmar view
Median duo
Flexor digitorum
superficialis tendons and
Two
flexor digitorum profundus
tendon
tendons
quartets
Common flexor sheath
(ulnar bursa)
Palmaris longus tendon
Median nerve
Radial artery
Flexor carpi radialis
tendon
Radial trio
Flexor pollicis longus
tendon in tendon
sheath (radial bursa)
Palmar carpal ligament (reflected)
(Synovial) tendon sheath
Ulnar artery
Ulnar nerve
Ulnar trio
Flexor carpi ulnaris
tendon
Pisiform
Transverse carpal ligament
Abductor digiti minimi muscle
Trapezium
1st metacarpal bone
Flexor digiti minimi brevis muscle
Opponens pollicis muscle
Abductor pollicis
brevis muscle
(reflected)
Opponens digiti minimi muscle
Superficial palmar (arterial) arch
Lumbrical muscles
Flexor pollicis brevis
muscle (reflected)
Adductor pollicis muscle
Figure 16-4: Intrinsic Muscles of Hand
Dorsal view
Palmar view
Tendinous slips to
hood of extensor
digitorum muscle
Deep transverse
metacarpal
ligament
Dorsal
interosseous
muscles
Abductor
pollicis
brevis muscle
Palmar
interosseous
muscles
Abductor digiti
minimi muscle
Radial
artery
Radius
Ulna
Radius
339
Ulna