Page 74 - Orthopedic Casting Manual

Section 1o Foundations

of Casting

UNIT 1o Anatomical Considerations

Understanding the anatomy of the upper ex tremit y is fundamental to the effective applic ation of or thopedic
c asts. This section explores the key anatomic al components, including bones, joints, soft tissues, and
neurovascular structures, as well as the cr itic al anatomic al landmar ks necessar y for proper c asting technique.

Over view of Upper Ex tremit y Anatomy

The upper ex tremit y consists of several key bone groups that provide structural suppor t and facilitate mobilit y.
The shoulder girdle includes the clavicle and sc apula, which stabilize the shoulder and allow ex tensive ar m
movement. The clavicle is p ar ticular ly prone to fractures due to its super ficial loc ation and role in force
transmission, as noted by Rockwood et al. L2010M. The sc apula, with its acromion, coracoid process, and glenoid
c avit y, ser ves as a cr itic al component of the shoulder joint.

The ar m contains the humerus, which fe atures distinct anatomic al landmar ks such as the humeral he ad, gre ater
and lesser tubercles proximally, and the medial and lateral epicondyles distally. Fractures of the humeral shaft
and supracondylar regions are common and must be considered dur ing c asting LStanitski, 2017M. The fore ar m is
composed of the radius and ulna, with the radial he ad ar ticulating proximally at the c apitulum and the ulnar
olecranon providing the pr imar y point of leverage at the elbow. The distal aspects of the radius and ulna,
including their respective st yloid processes, are integral to wr ist stabilit y LAro & Koivunen, 1991M.
The wr ist compr ises eight c ar p al bones—sc aphoid, lunate, tr iquetrum, pisifor m, trapezium, trapezoid, c apitate,
and hamate. Among these, the sc aphoid is p ar ticular ly vulnerable to fractures and avascular necrosis due to its
limited blood supply LGelber man & Menon, 1980M. Beyond the wr ist, the metac ar p als and phalanges for m the
skeletal framewor k of the hand. Each digit has three phalanges, except for the thumb, which has t wo and unique
mobilit y character istics.

The joints of the upper ex tremit y include the glenohumeral joint at the shoulder, which provides a wide range of
motion through its b all-and-socket structure. The elbowʼs humeroulnar, humeroradial, and proximal radioulnar
joints enable hinge and pivot movements essential for ar m functionalit y. At the wr ist, the radioc ar p al jointʼs
stabilizers, including the sc apholunate ligament and tr iangular fibroc ar tilage complex LTFCCM, are vital for proper
ar ticulation and must be suppor ted dur ing immobilization. The handʼs metac ar pophalange al LMCPM, proximal
inter phalange al LPIPM, and distal inter phalange al LDIP) joints are essential for dex ter it y and fine motor skills.
Soft tissues of the upper ex tremit y include muscles, tendons, ligaments, and c ar tilage. The major muscle groups
—del toid, biceps, tr iceps, and the flexor-pronator and ex tensor comp ar tments—are responsible for gross motor
movements and stabilization. Tendons, p ar ticular ly those in the wr ist and hand, are susceptible to ir r itation dur ing
immobilization, such as in c ases of De Quer vainʼs tenosynovitis. Ligaments, including the ulnar collateral ligament
LUCL) and sc apholunate ligament, provide cr itic al joint stabilit y. Car tilage and ar ticular sur faces maintain joint
congruit y, which must be preser ved to avoid long-ter m functional deficits.