Literature addressing hand injuries and rehabilitation protocols often refers to zones of the hand.Figure 4-2 diagrams the zones of the hand [Kleinert et al. 1981].Table 4-1 presents the zones’ borders. Therapists should be familiar with these zones for understanding literature, conversing with other health providers, and documenting pertinent information.

Table 4-1

Tendon Injury Zones of the Hand

Figure 4-2 Zones of the hand for (A) extensor and (B) flexor tendons. [From Kleinert HE, Schepel S, Gil1 T (1981). Flexor tendon injuries. Surgical Clinics of North America 61:267.]

Shoulder Joint

The shoulder complex comprises seven joints, including the glenohumeral, suprahumeral, acromioclavicular, scapulocostal, sternoclavicular, costosternal, and costovertebral joints [Cailliet 1981]. The suprahumeral and scapulocostal joints are pseudojoints, but they contribute to the shoulder’s function. Mobility of the shoulder is a compilation of all seven joints. Because the shoulder is extremely mobile, stability is sacrificed. This is evident when one considers that the head of the humerus articulates with approximately a third of the glenoid fossa. The shoulder complex allows motion in three planes, including flexion, extension, abduction, adduction, and internal and external rotation.

The scapula is intimately involved with movement at the shoulder. Scapulohumeral rhythm is a term used to describe the coordinated series of synchronous motions, such as shoulder abduction and elevation.

A complex of ligaments and tendons provides stability to the shoulder. Shoulder ligaments are named according to the bones they connect. The ligaments of the shoulder complex include the coracohumeral ligament and the superior, middle, and inferior glenohumeral ligaments [Kapandji 1970]. The rotator cuff muscles contribute to the dynamic stability of the shoulder by compressing the humeral head into the glenoid fossa [Wu 1996]. The rotator cuff muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis.Table 4-2 lists the muscles involved with scapular and shoulder movements.

Table 4-2

Muscles Contributing to Scapular and Shoulder Motions

Elbow Joint

The elbow joint complex consists of the humeroradial, humeroulnar, and proximal radioulnar joints. The humeroradial joint is an articulation between the humerus and the radius. The humeroradial joint has two degrees of freedom that allow for elbow flexion and extension and forearm supination and pronation. The humerus articulates with the ulna at the humeroulnar joint. Flexion and extension movements take place at the humeroulnar joint. Elbow flexion and extension are limited by the articular surfaces of the trochlea of the ulna and the capitulum of the humerus.

The medial and lateral collateral ligaments strengthen the elbow capsule. The radial collateral, lateral ulnar, accessory lateral collateral, and annular ligaments constitute the ligamentous structure of the elbow.

Muscles acting on the elbow can be categorized as functional groups: flexors, extensors, flexor-pronators, and extensor-supinators.Table 4-3 lists the muscles in these groups and their innervation.

Table 4-3

Elbow and Forearm Musculature Actions and Nerve Supply

Wrist Joint

The wrist joint is frequently incorporated into a splint’s design. A therapist must be knowledgeable of the wrist joint structure to appropriately choose and fabricate a splint that meets therapeutic objectives. The osseous structure of the wrist and hand consists of the ulna, radius, and eight carpal bones. Several joints are associated with the wrist complex, including the radiocarpal, midcarpal, and distal radioulnar joints.

The carpal bones are arranged in two rows (Figure 4-3). The proximal row of carpal bones includes the scaphoid (navicular), lunate, and triquetrum. The pisiform bone is considered a sesamoid bone [Wu 1996]. The distal row of carpal bones comprises the trapezium, trapezoid, capitate, and hamate. The distal row of carpal bones articulates with the metacarpals.

Figure 4-3 Carpal bones. Proximal row: scaphoid, lunate, pisiform, and triquetrum. Distal row: trapezium, trapezoid, capitate, and hamate. [From Pedretti LW (ed.), (1996). Occupational Therapy: Practice Skills for Physical Dysfunction, Fourth Edition. St. Louis: Mosby, p. 320.]

The radius articulates with the lunate and scaphoid in the proximal row of carpal bones. This articulation is the radiocarpal joint, which is mobile. The radiocarpal joint (Figure 4-4) is formed by the articulation of the distal head of the radius and the scaphoid and lunate bones. The ulnar styloid is attached to the triquetrum by a complex of ligaments and fibrocartilage. The ligaments bridge the ulna and radius and separate the distal radioulnar joint and the ulna from the radiocarpal joint. Motions of the radiocarpal joint include flexion, extension, and radial and ulnar deviation. The majority of wrist extension occurs at the midcarpal joint, with less movement occurring at the radiocarpal joint [Kapandji 1970].

Figure 4-4 Radiocarpal and midcarpal joints. [From Norkin C, Levangie P (1983). Joint Structure and Function: A Comprehensive Analysis. Philadelphia: F. A. Davis, p. 217.]

F. A. Davis.

The midcarpal joint (Figure 4-4) is the articulation between the distal and proximal carpal rows. The joint exists, although there are no interosseous ligaments between the proximal and distal rows of carpals [Buck 1995]. The joint capsules remain separate. However, the radiocarpal joint capsule attaches to the edge of the articular disk, which is distal to the ulna [Pratt 1991]. The wrist motions of flexion, extension, and radial and ulnar deviation also take place at this joint. The majority of wrist flexion occurs at the radiocarpal joint. The midcarpal joint contributes less movement for wrist flexion [Kapandji 1970].

The distal radioulnar joint is an articulation between the head of the ulna and the distal radius. Forearm supination and pronation occur at the distal radioulnar joint.

Wrist stability is provided by the close-packed positions of the carpal bones and the interosseous ligaments [Wu 1996]. The intrinsic intercarpal ligaments connect carpal bone to carpal bone. The extrinsic ligaments of the carpal bones connect with the radius, ulna, and metacarpals. The ligaments on the volar aspect of the wrist are thick and strong, providing stability. The dorsal ligaments are thin and less developed [Wu 1996]. In addition, the intercarpal ligaments of the distal row form a stable fixed transverse arch [Chase 1990]. Ligaments of the wrist cover the volar, dorsal, radial, and ulnar areas. The ligaments in the wrist serve to stabilize joints, guide motion, limit motion, and transmit forces to the hand and forearm. These ligaments also assist in prevention of dislocations. The wrist contributes to the hand’s mobility and stability. Having two degrees of freedom (movements occur in two planes), the wrist is capable of flexing, extending, and deviating radially and ulnarly.

Finger and Thumb Joints

Cutaneous and Connective Coverings of the Hand

The skin is the protective covering of the body. There are unique characteristics of volar and dorsal skin, which are functionally relevant. The skin on the palmar surface of the hand is thick, immobile, and hairless. It contains sensory receptors and sweat glands. The palmar skin attaches to the underlying palmar aponeurosis, which facilitates grasp [Bowers and Tribuzi 1992]. Palmar skin is different from the skin on the dorsal surface of the hand. The dorsal skin is thin, supple, and quite mobile. Thus, it is often the site for edema accumulation. The skin on the dorsum of the hand accommodates to the extremes of the fingers’ flexion and extension movements. The hair follicles on the dorsum of the hand assist in protecting as well as activating touch receptors when the hair is moved slightly [Bowers and Tribuzi 1992].

Palmar Fascia

The superficial layer of palmar fascia in the hand is thin. Its composition is highly fibrous and is tightly bound to the deep fascia. The deep fascia thickens at the wrist and forms the palmar carpal ligament and the flexor retinaculum. The fascia thins over the thenar and hypothenar eminences but thickens over the midpalmar area and on the volar surfaces of the fingers. The fascia forms the palmar aponeurosis and the fibrous digital sheaths [Buck 1995].

The superficial palmar aponeurosis consists of longitudinal fibers that are continuous with the flexor retinaculum and palmaris longus tendon. The flexor tendons course under the flexor retinaculum. With absence of the flexor retinaculum, as in carpal tunnel release, bowstringing (Figure 4-5) of the tendons may occur at the wrist level. The distal borders of the superficial palmar aponeurosis fuse with the fibrous digital sheaths. The deep layer of the aponeurosis consists of transverse fibers, which are continuous with the thenar and hypothenar fascias. Distally, the deep layer forms the superficial transverse metacarpal ligament [Buck 1995]. The extensor retinaculum is a fibrous band that bridges over the extensor tendons. The deep and superficial layers of the aponeurosis form this retinaculum.

Figure 4-5 Bowstringing of the flexor tendons. [From Stewart-Pettengill KM, van Strien G (2002). Postoperative management of flexor tendon injuries. In EJ Mackin, AD Callahan, TM Skirven, LH Schneider, AL Osterman (eds.), Rehabilitation of the Hand: Surgery and Therapy, Fifth Edition. St. Louis: Mosby, p. 434.]

Functionally, the fascial structure of the hand protects, cushions, restrains, conforms, and maintains the hand’s arches [Bowers and Tribuzi 1992]. Therapists may splint persons with Dupuytren’s disease, in which the palmar fascia thickens and shortens.

Joint Structure

Splints often immobilize or mobilize joints of the fingers and thumb. Therefore, a therapist must have knowledge of these joints. The hand skeleton comprises five polyarticulated rays (Figure 4-6). The radial ray or first ray (thumb) is the shortest and includes three bones: a metacarpal and two phalanges. Joints of the thumb include the carpometacarpal (CMC) joint, the metacarpophalangeal (MCP) joint, and the interphalangeal (IP) joint (Figure 4-6). Functionally, the thumb is the most mobile of the digits. The thumb significantly enhances functional ability by its ability to oppose the pads of the fingers, which is needed for prehension and grasp. The thumb has three degrees of freedom, allowing for flexion, extension, abduction, adduction, and opposition. The second through fifth rays comprise four bones: a metacarpal and three phalanges. Joints of the fingers include the MCP joint, proximal interphalangeal (PIP) joint, and the distal interphalangeal (DIP) joint. The digits are unequal in length. However, their respective lengths contribute to the hand’s functional capabilities.

Figure 4-6 Joints of the fingers and thumb.

The thumb’s metacarpotrapezial or CMC joint is saddle shaped and has two degrees of freedom, allowing for flexion, extension, abduction, and adduction movements. The CMC joints of the fingers have one degree of freedom to allow for small amounts of flexion and extension.

The fingers’ and thumb’s MCP joints have two degrees of freedom: flexion, extension, abduction, and adduction. The convex metacarpal heads articulate with shallow concave bases of the proximal phalanges. Fibrocartilaginous volar plates extend the articular surfaces on the base of the phalanges. As the finger’s MCP joint is flexed, the volar plate slides proximally under the metacarpal. This mechanism allows for significant range of motion. The volar plate movement is controlled by accessory collateral ligaments and the metacarpal pulley for the long flexor tendons to blend with these structures.

During extension, the MCP joint is able to move medially and laterally. During MCP extension, collateral ligaments are slack. When digits II through V are extended at the MCP joints, finger abduction movement is free. Conversely, when the MCP joints of digits II through V are flexed abduction is extremely limited. The medial and lateral collateral ligaments of the metacarpal heads become taut and limit the distance by which the heads can be separated for abduction to occur. Mechanically, this provides stability during grasp.

Digits II through V have two interphalangeal joints: a PIP joint and a DIP joint. The thumb has only one IP joint. The IP joints have one degree of freedom, contributing to flexion and extension motions. IP joints have a volar plate mechanism similar to the MCP joints, with the addition of check reign ligaments. The check reign ligaments limit hyperextension.

Table 4-4 provides a review of muscle actions and nerve supply of the wrist and hand [Clarkson and Gilewich 1989]. Muscles originating in the forearm are referred to as extrinsic muscles. Intrinsic muscles originate within the hand. Each group contributes to upper extremity function.

Table 4-4

Wrist and Hand Musculature Actions and Nerve Supply

Extrinsic Muscles of the Hand

Extrinsic muscles acting on the wrist and hand can be further categorized as extensor and flexor groups. Extrinsic muscles of the wrist and hand are listed in Box 4-1. Extrinsic flexor muscles are most prominent on the medial side of the upper forearm. The function of extrinsic flexor muscles includes flexion of joints between the muscles’ respective origin and insertion. Extrinsic muscles of the hand and forearm accomplish flexion and extension of the wrist and the phalanges (fingers). For example, the flexor digitorum superficialis flexes the PIP joints of digits II through V, whereas the flexor digitorum profundus primarily flexes the DIP joints of digits II through V.

Because these tendons pass on the palmar side of the MCP joints, they tend to produce flexion of these joints. During grasp, flexion of the MCPs is necessary to obtain the proper shape of the hand. However, flexion of the wrist is undesirable because it decreases the grip force. The synergic contraction of the wrist extensors during finger flexion prevents wrist flexion during grasp.

The force of the extensor contraction is proportionate to the strength of the grip. The stronger the grip the stronger the contraction of the wrist extensors [Smith et al. 1996]. Digit extension and flexion are a combined effort from extrinsic and intrinsic muscles.

At the level of the wrist, the extensor tendons organize into six compartments [Fess et al. 2005]. The first compartment consists of tendons from the abductor pollicis longus (APL) and extensor pollicis brevis (EPB). When the radial side of the wrist is palpated, it is possible to feel the taut tendons of the APL and EPB.

The second compartment contains tendons of the extensor carpi radialis longus (ECRL) and brevis (ECRB). A therapist can palpate the tendons on the dorsoradial aspect of the wrist by applying resistance to an extended wrist.

The third compartment houses the tendon of the extensor pollicis longus (EPL). This tendon passes around Lister’s tubercle of the radius and inserts on the dorsal base of the distal phalanx of the thumb.

The fourth compartment includes the four communis extensor (EDC) tendons and the extensor indicis proprius (EIP) tendon, which are the MCP joint extensors of the fingers.

The fifth compartment includes the extensor digiti minimi (EDM), which extends the little finger’s MCP joint. The EDM acts alone to extend the little finger.

The sixth compartment consists of the extensor carpi ulnaris (ECU), which inserts at the dorsal base of the fifth metacarpal. A taut tendon can be palpated over the ulnar side of the wrist just distal to the ulnar head.

Unlike the other fingers, the index and little fingers have dual extensor systems comprising the EIP and the EDM in conjunction with the extensor digitorum communis. The EIP and EDM tendons lie on the ulnar side of the extensor digitorum communis tendons. Each finger has a flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendon. Five annular (or A) pulleys and four cruciate (or C) pulleys prevent the flexor tendons from bowstringing (Figure 4-7).

Figure 4-7 Annular (A) and cruciate (C) pulley system of the hand. The digital flexor sheath is formed by five annular (A) pulleys and three cruciate (C) bands. The second and fourth annular pulleys are the most important for function. [From Tubiana R, Thomine JM, Mackin E (1996). Examination of the Hand and Wrist. St. Louis: Mosby, p. 81.]

In relationship to splinting, when pathology affects extrinsic musculature the splint design often incorporates the wrist and hand. This wrist-hand splint design is necessary because the extrinsic muscles cross the wrist and hand joints.

Intrinsic Muscles of the Hand and Wrist

The intrinsic muscles of the thumb and fingers are listed in Box 4-2. The intrinsic muscles are the muscles of the thenar and hypothenar eminences, the lumbricals, and the interossei. Intrinsic muscles can be grouped according to those of the thenar eminence, the hypothenar eminence, and the central muscles between the thenar and hypothenar eminences. The function of these intrinsic hand muscles produces flexion of the proximal phalanx and extension of the middle and distal phalanges, which contribute to the precise finger movements required for coordination.

Box 4-2 Intrinsic Muscles of the Hand