Hand injuries account for up to 15% of all trauma cases seen in the emergency department (ED). Their complex anatomy, ability to perform fine movements, and importance in daily life make missing these injuries potentially devastating.
The hand has a dorsal and a volar surface and the same terms are used when discussing the digits. In addition, each digit has a radial and an ulnar border. The muscle mass at the base of the thumb is called the thenar eminence and the muscle mass along the ulnar border of the hand is the hypothenar eminence.
The motions of the wrist include radial and ulnar deviation and extension and flexion. Motions of the thumb include flexion and extension, abduction and adduction, and opposition (Fig. 11–1). The digits are named the thumb, index, long, ring, and little fingers, respectively. The thumb is the first digit and the little finger is the fifth digit.
Terms used to describe motion of the hand and the digits.
When a patient presents to the ED with a hand complaint, the physician should first ascertain if there is any history of trauma. The approach and differential diagnosis of a traumatized hand are quite different from that of a nontraumatized hand. Important historical points to be elicited in evaluating traumatic hand injuries include:
The time elapsed since the injury
The environment in which the injury occurred (contamination)
The mechanism of injury (crush, laceration, etc.)
In the nontraumatized hand, the most important historical questions are:
When did the symptoms begin?
What functional impairment has been experienced?
What activities worsen the symptoms?
The design and versatility of the human hand has impressed anatomists and authors for centuries. Anatomically, the hand is a group of highly mobile gliding bones connected by tendons and ligaments to a “fixed center.” This fixed center consists of the second and third metacarpal bones. The remainder of the hand is suspended from these two relatively immobile bones. All of the intrinsic movements of the hand are relative to and dependent on the stability and immobility of these two bones.
The skin of the volar hand and fingers is fixed to the underlying bone by fibrous septa. This helps with grip, limits movement, and does not allow significant swelling. The dorsal hand has looser, thinner skin. This allows a fairly extensive space for swelling from trauma or infection. The clinician treating hand injuries should be aware that the venous and lymphatic drainage takes place on the dorsum of the hand. Any condition that causes inflammation and swelling in the hand can lead to lymphatic congestion and nonpitting edema over the dorsal aspect of the hand.
The fingertip is defined as the structures distal to the insertion of the flexor and extensor tendons on the distal phalanx. It comprises the nail (i.e., nail plate), nail bed, pulp, and distal phalanx (Fig. 11–2). The nail complex consists of the eponychium (cuticle or dorsal roof), perionychium (nail edge), hyponychium (where the nail adheres to the nail bed at the tip of the nail), and the nail bed or matrix (under the nail plate). The nail bed comprises a germinal and sterile matrix. The germinal matrix is proximal, ending at the lunula, and accounts for approximately 90% of nail growth. The sterile matrix makes up the majority of the nail bed and helps keep the nail tightly affixed to the finger. The dorsal roof of the proximal nail fold is responsible for the nail's shine.
Fibrous septa extend from the bone to the skin and serve to stabilize fractures of the distal phalanx.
Tendon and Muscle Assessment
The muscles and tendons of the hand are divided into (1) extrinsic flexors, (2) extrinsic extensors, and (3) intrinsic muscles.
There are 12 flexor tendons contained in the volar compartment of the forearm that serve to flex the wrist, hand, and digits, as well as provide radial and ulnar deviation. They are the flexor carpi radialis, flexor carpi ulnaris, palmaris tendon, flexor pollicis longus, four flexor digitorum superficialis (FDS) tendons, and four flexor digitorum profundus (FDP) tendons.
Nine extensor tendons course over the dorsal aspect of the forearm and wrist. The extensor tendons include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, extensor digitorum communis, extensor digiti minimi, and extensor indicis proprius. The most common site of tendon injury is over the dorsum of the hand where the extensor tendons are more superficial and exposed to injury.
The intrinsics, which lie in the body of the hand, are composed of 20 individual muscles, which are responsible for fine motor movement of the hand. The intrinsics are less commonly injured than the extrinsic flexor and extensor tendons.
Tendons function best when they are at an optimal position of stretch. The extensor carpi radialis brevis is the most important of the wrist extensors, acting to stretch the flexor tendons to obtain a powerful grasp. To demonstrate this point, compare the power to grasp an object with the wrist in flexion and in approximately 15 degrees of extension.
Hand tendons are quite mobile and are held in place by pulleys that prevent the tendon from dislodging from its normal position. The flexor tendons are also ensheathed by a synovial membrane that acts as a lubricant to permit normal gliding of the tendon. The tendons are almost avascular in the ...