C h a p t e r 4 3
Disorders of the Skeletal System: Trauma, Infections, Neoplasms, and Childhood Disorders
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are among the most common fractures of childhood.
10
The typical mechanism of fracture is a fall on the lateral
shoulder, or less commonly by a direct blow or by fall-
ing on an outstretched arm. Most clavicle fractures are
treated nonoperatively, with either a simple arm sling or
figure-of-eight clavicle strap.
5,8
Three articulations form the shoulder joint—the
acromioclavicular joint, which joins the clavicle to the
acromion of the scapula; the glenohumeral joint, which
connects the head of the humerus to the relatively shal-
low glenoid cavity in the scapula; and the sternoclavicu-
lar joint, which joins the sternum to the clavicle.
10
The
stability of these joints is provided by a series of muscles
and tendons. The acromioclavicular joint is a common
site of sprains in athletes and physically active persons.
The classic cause of an acromioclavicular joint injury
is a direct blow to the acromion with the humerus in
an adducted position. This force drives the acromion
medially and inferiorly. Acromioclavicular joint injuries
also may be caused by indirect trauma, such as falling
on an outstretched arm or elbow. The glenohumeral
joint is one of the most commonly dislocated joints. It
is also the joint most likely to develop problems with
instability. Most acute dislocations involve anterior dis-
placement of the humeral head with respect to the gle-
noid cavity, the result of the shoulder being abducted
and forcefully extended and rotated. Other mechanisms
include a fall on an outstretched arm or a blow to the
posterior shoulder.
Movement of the shoulder results from the coordi-
nated efforts of the muscles of the rotator cuff: the supra-
spinous, teres minor, infraspinatus, and subscapularis.
5,8
These muscles and their musculotendinous attachments
form a cover around the head of the humerus and
function to rotate the arm and stabilize the humoral
head against the glenoid. The rotator cuff muscles are
separated from the overlying “coracoacromial arch” by
the subdeltoid and subcoracoid bursae.
Disorders of the rotator cuff, such as tendinitis,
subacromial bursitis, and partial and complete tears,
account for a substantial majority of shoulder prob-
lems (see Fig. 43-2). Rotator cuff injuries can result
from excessive use, a direct blow, or stretch injury, usu-
ally involving throwing or swinging, as with baseball
pitchers or tennis players.
5,8
While rotator cuff injuries
sometimes occur with acute injury, most result from a
combination of factors, including altered blood supply
to the tendons, repeated mechanical insult as the tendon
passes under the coracoacromial arch, and age-related
degeneration. Repetitive overhead throwing, which
produces significant stress on the glenohumeral com-
plex of the rotator cuff, is a common cause of rotator
cuff tendinitis. Full-thickness tears are more common in
persons older than 40 years of age, although they can
occur in athletes.
5,9,11
Tears generally originate in the
supraspinous tendon and may progress posteriorly and
anteriorly.
The major clinical features of rotator cuff disorders
are pain (especially at night), tenderness, and occasion-
ally muscle atrophy. Pain and impingement may be
noted when motions of the arm squeeze and pinch cuff
tendons between the humerus and the overlying arch.
With rotator cuff tears, there may be difficulty abducting
and rotating the arm.
Several physical examination maneuvers, including
assessment of active and passive range of motion, are used
to define shoulder pathology. The history and mechanism
of injury are important. In addition to standard radio-
graphs, an arthrogram or magnetic resonance imaging
(MRI) scan may be obtained. Arthroscopic examination
under anesthesia may be done for diagnostic purposes.
Conservative treatment with anti-inflammatory agents,
corticosteroid injections, and physical therapy often is
used. A period of rest is followed by a customized exercise
and rehabilitation program to improve strength, flexibil-
ity, and endurance. Surgical repair may be considered for
persons with an acute traumatic rotator cuff tear or those
with significant symptoms and failed rehabilitation.
Knee Injuries
The knee is a common site of injury, particularly sports-
related injuries in which the knee is subjected to abnor-
mal twisting and compression forces.
8,12,13
These forces
can result in injury to the ligaments and menisci, patel-
lar subluxation and dislocation, and the patellofemoral
pain syndrome. Many knee injuries can predispose to
osteoarthritis in later life.
The knee joint consists of lateral and medial femoral
condyles, the lateral and medial femotibial condyles, and
the patella
10
(Fig. 43-3). It is essentially a round bone
(femoral condyles) sitting on a flat bone (tibial condyles)
with no intrinsic bony stability and depends on its liga-
ments and menisci for support.
8
The most important
ligaments are the medial and lateral collateral ligaments
along with their associated posterior capsular structures
Clavicle
Coracoid
Scapula
Glenoid
cavity
Supraspinatus
muscle
Rupture of
supraspinatus tendon
Acromion
Humerus
Subacromial bursa
(distended with
fluid due to
inflammation)
FIGURE 43-2.
Structures of the glenohumeral shoulder joint,
showing the location of common rotator cuff injuries.The
supraspinatus muscle is the most commonly injured part of
the rotator cuff. (Adapted from Moore KL, Dalley AF. Clinically
Oriented Anatomy. 5th ed. Philadelphia, PA: Lippincott Williams
&Wilkins; 2006:763.)
