Elbow and Forearm Moore
Added surface area for attachment of flexors and extensors of the wrist is provided by the...
epicondyles, the medial and lateral extensions of the distal end of the humerus
The combined synovial proximal and distal radio-ulnar joints plus the interosseous membrane enable _______________ of the forearm.
pronation and supination
The common place for measuring the pulse rate is where the _____ artery lies on the anterior surface of the distal end of the radius, lateral to the tendon of the FCR. Here the artery is covered by only fascia and skin. The artery can be compressed against the distal end of the radius, where it lies between the tendons of the FCR and APL. When measuring the radial pulse rate, the pulp of the thumb should not be used because it has its own pulse, which could obscure the patient's pulse. If a pulse cannot be felt, try the other wrist because an aberrant radial artery on one side may make the pulse difficult to palpate. A radial pulse may also be felt by pressing lightly in the anatomical snuff box.
radial
The extensor-supinator muscles of the posterior compartment of the forearm are located posterolaterally in the proximal forearm and are innervated by the _____ nerve
radial
The integrity and functions of the humeroradial joint and proximal radio-ulnar joint complex depends primarily on the combined ______________
radial collateral and anular ligaments.
The _____________ bundle—containing the radial artery, accompanying veins, and superficial radial nerve—courses along and defines the border between the anterior and the posterior forearm compartments (the vascular structures serving both) deep to the brachioradialis.
radial neurovascular
Three major (___________) and two minor (___________) neurovascular bundles occur deep to the antebrachial fascia.
radial, median or middle, and ulnar anterior and posterior interosseous
More than 27% of nerve lesions of the upper limb affect the ulnar nerve (Rowland, 2010). Ulnar nerve injuries usually occur in four places: _______________________________________________________________________________________ Ulnar nerve injury occurs most commonly where the nerve passes posterior to the medial epicondyle of the humerus (Fig. B3.27). The injury results when the medial part of the elbow hits a hard surface, fracturing the medial epicondyle ("funny bone"). Any lesion superior to the medial epicondyle will produce paresthesia of the median part of the dorsum of the hand. Compression of the ulnar nerve at the elbow (cubital tunnel syndrome) is also common (see the clinical box "Cubital Tunnel Syndrome"). Ulnar nerve injury usually produces numbness and tingling (paresthesia) of the medial part of the palm and the medial one and a half fingers (Fig. B3.28). Pluck your ulnar nerve at the posterior aspect of your elbow with your index finger and you may feel tingling in these fingers. Severe compression may also produce elbow pain that radiates distally. Uncommonly, the ulnar nerve is compressed as it passes through the ulnar canal (see the clinical box "Ulnar Canal Syndrome").
(1) posterior to the medial epicondyle of the humerus, (2) in the cubital tunnel formed by the tendinous arch connecting the humeral and ulnar heads of the FCU, (3) at the wrist, and (4) in the hand.
Although the elbow joint appears simple because of its primary function as a hinge joint, the fact that it involves the articulation of a single bone proximally with two bones distally, one of which rotates, confers surprising complexity on this compound _____________. The hinge movement, the ability to transmit forces, and the high degree of stability of the joint primarily result from the conformation of the articular surfaces of the humero-ulnar joint (i.e., of the trochlear notch of the ulna to the trochlea of the humerus).
(three-part) joint.
When the median nerve is severed in the elbow region, flexion of the proximal interphalangeal joints of the________ digits is lost and weakened in the __________ digits. Flexion of the distal interphalangeal joints of the 2nd and 3rd digits is also lost (Fig. B3.25A). Flexion of the distal interphalangeal joints of the 4th and 5th digits is not affected because the medial part of the FDP, which produces these movements, is supplied by the ulnar nerve. The ability to flex the metacarpophalangeal joints of the 2nd and 3rd digits is affected because the digital branches of the median nerve supply the 1st and 2nd lumbricals. Thus, when the person attempts to make a fist, the 2nd and 3rd fingers remain partially extended ("hand of benediction") (Fig. B3.25B). Thenar muscle function (function of the muscles at the base of the thumb) is also lost, as in carpal tunnel syndrome (see the clinical box "Carpal Tunnel Syndrome"). When the anterior interosseous nerve is injured, the thenar muscles are unaffected, but paresis (partial paralysis) of the flexor digitorum profundus and flexor pollicis longus occurs. When the person attempts to make the "okay" sign, opposing the tip of the thumb and index finger in a circle, a "pinch" posture of the hand results instead owing to the absence of flexion of the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger (anterior interosseous syndrome) (Fig. B3.25C).
1st-3rd, 4th and 5th
__________ in children can result from a fall that causes severe abduction of the extended elbow, an abnormal movement of this articulation. The resulting traction on the ulnar collateral ligament pulls the medial epicondyle distally (Fig. B3.38). The anatomical basis of the avulsion is that the epiphysis for the medial epicondyle may not fuse with the distal end of the humerus until up to age 20. Usually, fusion is complete radiographically at age 14 in females and age 16 in males.
Avulsion (forced separation) of the medial epicondyle
_____________ results in pain when the forearm is pronated because this action compresses the bicipitoradial bursa against the anterior half of the tuberosity of the radius (see Fig. 3.103C).
Bicipitoradial bursitis (biceps bursitis)
The supinator acts at the radio-ulnar joint, while the remaining muscles extend and abduct the hand at the wrist joint and the thumb. The _____ may also contribute to adduction of the hand.
ECU
__________________ is a painful musculoskeletal condition that may follow repetitive use of the superficial extensor muscles of the forearm. Pain is felt over the lateral epicondyle and radiates down the posterior surface of the forearm. People with elbow tendinitis often feel pain when they open a door or lift a glass. Repeated forceful flexion and extension of the wrist strain the attachment of the common extensor tendon, producing inflammation of the periosteum of the lateral epicondyle (lateral epicondylitis).
Elbow tendinitis ("tennis elbow")
______ ("cocking") of the wrist is important in enabling the flexors of the fingers to grip tightly or make a fist.
Extension
____________, called a "fractured elbow" by laypersons, is common because the olecranon is subcutaneous and protrusive. The typical mechanism of injury is a fall on the elbow combined with sudden powerful contraction of the triceps brachii. The fractured olecranon is pulled away by the active and tonic contraction of the triceps (Fig. B3.21A, B), and the injury is often considered to be an avulsion fracture (Salter, 1999). Because of the traction produced by the tonus of the triceps on the olecranon fragment, pinning is usually required. Healing occurs slowly, and often a cast must be worn for an extended period of time.
Fracture of the olecranon
____________ may occur when children fall on their hands with their elbows flexed. Dislocations of the elbow may also result from hyperextension or a blow that drives the ulna posterior or posterolateral. The distal end of the humerus is driven through the weak anterior part of the fibrous layer of the joint capsule as the radius and ulna dislocate posteriorly (Fig. B3.40). The ulnar collateral ligament is often torn, and an associated fracture of the head of the radius, coronoid process, or olecranon process of the ulna may occur. Injury to the ulnar nerve may occur, resulting in numbness of the little finger and weakness of flexion and adduction of the wrist.
Posterior dislocation of the elbow joint
_______________, a nerve entrapment syndrome, is caused by compression of the median nerve near the elbow. The nerve may be compressed between the heads of the pronator teres as a result of trauma, muscular hypertrophy, or fibrous bands. Individuals with this syndrome are first seen clinically with pain and tenderness in the proximal aspect of the anterior forearm, and hypesthesia (decreased sensation) of palmar aspects of the radial three and half digits and adjacent palm (Fig. B3.26). Symptoms often follow activities that involve repeated pronation.
Pronator syndrome
_______________ is much less common. It results from excessive friction between the triceps tendon and olecranon, for example, resulting from repeated flexion-extension of the forearm, as occurs during certain assembly-line jobs. The pain is most severe during flexion of the forearm because of pressure exerted on the inflamed subtendinous olecranon bursa by the triceps tendon (Fig. 3.101).
Subtendinous olecranon bursitis
_____________ is a frequent complication of the abduction type of avulsion of the medial epicondyle of the humerus. The anatomical basis for stretching of the ulnar nerve is that it passes posterior to the medial epicondyle before entering the forearm (see Fig. 3.47A)
Traction injury of the ulnar nerve
Muscles of the deep layer attach to the anterior aspects of the radius and ulna, flex...
all (but especially the distal) joints of all five digits, and pronate the forearm.
The middle (median nerve and variable median artery and veins) and ulnar (ulnar nerve, artery, and accompanying veins) bundles course in a fascial plane between the intermediate and the deep flexor muscles. The median nerve supplies most muscles in the _______ compartment, many via its anterior interosseous branch, which courses on the interosseous membrane.
anterior
The ___________ ligament of the proximal joint, articular disc of the distal joint, and interosseous membrane not only hold the two bones together while permitting the necessary motion between them but (especially the membrane) also transmit forces received from the hand by the radius to the ulna for subsequent transmission to the humerus and pectoral girdle.
anular
Sometimes the _________ artery divides at a more proximal level than usual. In this case, the ulnar and radial arteries begin in the superior or middle part of the arm, and the median nerve passes between them. The musculocutaneous and median nerves commonly communicate as shown in Figure B3.23.
brachial High Division of Brachial Artery
The radiohumeral joint is the portion of the elbow joint between the _______________
capitulum and the head of the radius
The superficial and intermediate muscles of the anterior (flexor-pronator) compartment of the forearm are located anteromedially because they arise mainly from the....
common flexor attachment (medial epicondyle and supra-epicondylar ridge) of the humerus
Tendons passing to the medial 4 digits are involved in _________ on the dorsal aspects of the fingers.
complex extensor expansions
The ulnar nerve may be compressed (ulnar nerve entrapment) in the cubital tunnel formed by the tendinous arch joining the humeral and ulnar heads of attachment of the FCU (see Fig. 3.59; Table 3.10). The signs and symptoms of __________ are the same as an ulnar nerve lesion in the ulnar groove on the posterior aspect of the medial epicondyle of the humerus.
cubital tunnel syndrome
Synovial Cyst of Wrist Sometimes a nontender cystic swelling appears on the hand, most commonly on the _______of the wrist (Fig. B3.22). Usually the cyst is the size of a small grape, but it varies and may be as large as a plum. The thin-walled cyst contains clear mucinous fluid. The cause of the cyst is unknown, but it may result from mucoid degeneration (Salter, 1999). Flexion of the wrist makes the cyst enlarge, and it may be painful. Synovial cysts are close to and often communicate with the synovial sheaths on the dorsum of the wrist (purple in figure). The distal attachment of the ECRB tendon to the base of the 3rd metacarpal is another common site for such a cyst. A cystic swelling of the common flexor synovial sheath on the anterior aspect of the wrist can enlarge enough to produce compression of the median nerve by narrowing the carpal tunnel (carpal tunnel syndrome). This syndrome produces pain and paresthesia (partial numbness, burning, or prickling) in the sensory distribution of the median nerve and clumsiness of finger movements (see the clinical box "Carpal Tunnel Syndrome").
dorsum
Ulnar nerve injury can result in _____________________. An injury to the nerve in the distal part of the forearm denervates most intrinsic hand muscles. Power of wrist adduction is impaired, and when an attempt is made to flex the wrist joint, the hand is drawn to the lateral side by the FCR (supplied by the median nerve) in the absence of the "balance" provided by the FCU. After ulnar nerve injury, the person has difficulty making a fist because, in the absence of opposition, the metacarpophalangeal joints become hyperextended, and he or she cannot flex the 4th and 5th digits at the distal interphalangeal joints when trying to make a fist. Furthermore, the person cannot extend the interphalangeal joints when trying to straighten the fingers. This characteristic appearance of the hand, resulting from a distal lesion of the ulnar nerve, is known as claw hand (main en griffe). The deformity results from atrophy of the interosseous muscles of the hand supplied by the ulnar nerve. The claw is produced by the unopposed action of the extensors and FDP. For a description of ulnar nerve injury at the wrist, see the clinical box "Ulnar Canal Syndrome."
extensive motor and sensory loss to the hand
The only muscle of the intermediate layer (FDS) primarily....
flexes the proximal joints of 2nd-5th digits.
Once veins have penetrated the deep fascia, cutaneous nerves run independently of the veins in the subcutaneous tissue, where they remain constant in location and size, with lateral, medial, and posterior cutaneous nerves of the forearm supplying the aspects of the _______ described by their names.
forearm
Proximally, the larger medial ulna forms the primary articulation with the humerus, whereas distally, the shorter lateral radius forms the primary articulation with the hand via the wrist. Because the ulna does not reach the wrist, forces received by the hand are transmitted from the radius to the ulna via the ___________
interosseous membrane
The long shaft of the humerus enables reaching and makes it an effective ________ for power in lifting, as well as providing surface area for attachment of muscles that act primarily at the elbow.
lever
Sudden severe tension on a long extensor tendon may avulse part of its attachment to the phalanx. The most common result of this injury is a _____________ (Fig. B3.20A). This deformity results from the distal interphalangeal joint suddenly being forced into extreme flexion (hyperflexion) when, for example, a baseball is miscaught or a finger is jammed into the base pad (Fig. B3.20B). These actions avulse (tear away) the attachment of the tendon to the base of the distal phalanx. As a result, the person cannot extend the distal interphalangeal joint. The resultant deformity bears some resemblance to a mallet.
mallet or baseball finger
The long, strong humerus is a mobile strut—the first in a series of two—used to position the hand at a height (level) and distance from the trunk to ___________
maximize its efficiency
Occasionally, communications occur between the____________ nerves in the forearm. These branches are usually represented by slender nerves, but the communications are important clinically because even with a complete lesion of the median nerve, some muscles may not be paralyzed. This may lead to an erroneous conclusion that the median nerve has not been damaged.
median and ulnar
The muscles of the anterior compartment are innervated mostly by the ________ nerve, but one and a half muscles (the FCU and ulnar half of the FDP) are innervated by the _______ nerve.
median, ulnar
The ulna and radius together make up the second unit of a two-unit articulated strut (the first unit being the humerus), projecting from a mobile base (shoulder) that serves to position the hand. Because the forearm unit is formed by two parallel bones, and the radius is able to _______ about the ulna, supination and pronation of the hand are possible during elbow flexion.
pivot
Flexion of the wrist and hand is used for grasping, gripping, and drawing things toward one self. Pronation is used for _________________. Both movements are basic protective (defensive) movements.
positioning the hand to manipulate or pick things up
The deep radial nerve penetrates the supinator to join the posterior interosseous artery in the plane between the superficial and the deep extensors. This nerve supplies all the muscles arising in the _______ compartment.
posterior
Well-developed _________ veins course in the subcutaneous tissue of the forearm. These veins are subject to great variation.
subcutaneous
The subcutaneous olecranon bursa (Figs. 3.97C and 3.101) is exposed to injury during falls on the elbow and infection from abrasions of skin covering the olecranon. Repeated excessive pressure and friction, as occurs in wrestling, for example, may cause this bursa to become inflamed, producing a friction ____________________ (Fig. B3.37). This type of bursitis is also known as "dart thrower's elbow" and "miner's elbow." Occasionally, the bursa becomes infected and the area over the bursa becomes inflamed.
subcutaneous olecranon bursitis (e.g., "student's elbow")
Muscles in the _________ layer "bend" the wrist to position the hand (i.e., flex the wrist when acting exclusively and abduct or adduct the wrist when working with their extensor counterparts) and assist pronation.
superficial
The origin of the radial artery may be more proximal than usual; it may be a branch of the axillary or brachial arteries (Fig. B3.23). Sometimes the radial artery is __________ to the deep fascia instead of deep to it. When a superficial vessel is pulsating near the wrist, it is probably a superficial radial artery. The aberrant vessel is vulnerable to laceration.
superficial
In approximately 3% of people, the ulnar artery descends _______ to the flexor muscles (Fig. B3.24). Pulsations of a superficial ulnar artery can be felt and may be visible. This variation must be kept in mind when performing venesections for withdrawing blood or making intravenous injections. If an aberrant ulnar artery is mistaken for a vein, it may be damaged and produce bleeding. If certain drugs are injected into the aberrant artery, the result could be fatal.
superficial Superficial Ulnar Artery
The extensor muscles become __________ in the distal forearm and pass deep to the extensor retinaculum in osseofibrous tunnels.
tendinous
The sudden pulling of the upper limb tears the distal attachment of the anular ligament, where it is loosely attached to the neck of the radius. The radial head then moves distally, partially out of the "socket" formed by the anular ligament (Fig. B3.41B). The proximal part of the torn ligament may become trapped between __________________. The source of pain is the pinched anular ligament. Treatment of the subluxation consists of supination of the child's forearm while the elbow is flexed (Salter, 1999). The tear in the anular ligament heals when the limb is placed in a sling for 2 weeks.
the head of the radius and the capitulum of the humerus
Preschool children, particularly girls, are vulnerable to__________________. The history of these dislocations is typical. The child is suddenly lifted (jerked) by the upper limb while the forearm is pronated (e.g., lifting a child) (Fig. B3.41A). The child may cry out, refuse to use the limb, and protect their limb by holding it with the elbow flexed and the forearm pronated.
transient subluxation (incomplete dislocation) of the head of the radius (also called "nursemaid's elbow" or "pulled elbow")
The spherical head of the humerus enables a great range of motion on the mobile scapular base; the _________________ at its distal end facilitate the hinge movements of the elbow and, at the same time, the pivoting of the radius.
trochlea and capitulum
The flexor muscles of the anterior compartment have approximately ______ the bulk and strength of the extensor muscles of the posterior compartment. This, and the fact that the flexor aspect of the limb is the more protected aspect, accounts for the major neurovascular structures being located in the anterior compartment, with only the relatively small posterior interosseous vessels and nerve in the posterior compartment.
twice
The middle (median nerve and variable median artery and veins) and ulnar (ulnar nerve, artery, and accompanying veins) bundles course in a fascial plane between the intermediate and the deep flexor muscles. The median nerve supplies most muscles in the anterior compartment, many via its anterior interosseous branch, which courses on the interosseous membrane. The ________ nerve supplies the one and a half exceptions (FCU and ulnar half of the FDP).
ulnar
Rupture, tearing, and stretching of the __________ are increasingly common injuries related to athletic throwing—primarily baseball pitching (Fig. B3.39A), but this injury may also result from football passing, javelin throwing, and playing water polo. Reconstruction of the UCL, known as a "Tommy John procedure" (after the first pitcher to undergo the surgery), involves an autologous transplant of a long tendon from the contralateral forearm or leg (e.g., the palmaris longus or plantaris tendon; Fig. B3.39B). A 10- to 15-cm length of tendon is passed through holes drilled through the medial epicondyle of the humerus and the lateral aspect of the coronoid process of the ulna (Fig. B3.39C-E).
ulnar collateral ligament (UCL; Fig. 3.107B)
The radial nerve is usually injured in the arm by a fracture of the humeral shaft. This injury is proximal to the motor branches to the long and short extensors of the wrist from the (common) radial nerve, and so ________ is the primary clinical manifestation of an injury at this level (see the clinical box "Injury to the Radial Nerve in Arm"). Injury to the deep branch of the radial nerve may occur when wounds of the posterior forearm are deep (penetrating). Severance of the deep branch results in an inability to extend the thumb and the metacarpophalangeal (MP) joints of the other digits. Thus, the integrity of the deep branch may be tested by asking the person to extend the MP joints while the examiner provides resistance (Fig. B3.29). If the nerve is intact, the long extensor tendons should appear prominently on the dorsum of the hand, confirming that the extension is occurring at the MP joints rather than at the interphalangeal joints (movements under the control of other nerves). Loss of sensation does not occur because the deep branch of the radial nerve is entirely muscular and articular in distribution. See Table 3.13 to determine the muscles that are paralyzed (e.g., extensor digitorum) when this nerve is severed. When the superficial branch of the radial nerve, a cutaneous nerve, is severed, sensory loss is usually minimal. Commonly, a coin-shaped area of anesthesia occurs distal to the bases of the 1st and 2nd metacarpals. The reason the area of sensory loss is less than expected, given the areas highlighted in Figure 3.69D, is the result of the considerable overlap from cutaneous branches of the median and ulnar nerves.
wrist-drop
