The Hand

Key Practice Points

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Patients with hand injuries are treated in the supine position to prevent syncopal falls induced by pain.
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Remove all jewelry from the injured hand to prevent constriction and ischemia secondary to swelling.
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The “golden period” for repair of hand lacerations and wounds is 6 to 8 hours from the time of injury. Beyond that period, the risk of infection rises.
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Although two-point discrimination is the standard test to measure sensation following possible nerve injuries to the hand, a normal test does not rule out nerve injury if the patient has a subjective feeling of numbness.
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Innocuous-appearing wounds, such as punctures, can cause significant wounds to tendons and nerves. Careful testing is still necessary.
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Tendons can appear to function normally after wounding because of partial injury or cross-linking of extensor tendons. It is prudent to explore wounds over tendons to detect these types of injuries.
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Absorbable sutures are becoming more common in the closure of hand wounds, because they produce the same results as nonabsorbable sutures.
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If the nail is attached firmly to the nail bed, subungual hematomas (even if the subungual hematoma is >50% of the nail surface) can be treated with trephination alone without nail removal or nail bed repair.
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Fingertip avulsions, without nail bed disruption or bone exposure, heal well without surgical intervention or grafting.
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Tendon or nerve injuries can undergo delayed repair. The skin is closed at the time of injury and the patient is referred to a specialist for nerve or tendon repair of the hand.
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Infections and antibiotic prophylaxis of hand wounds have recently become more complicated because of the appearance of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).

Initial Treatment

Before a thorough and careful examination of a patient with an injured hand can take place, certain preparatory steps must be taken. Except for the most trivial injuries, the patient is best managed by placement on a stretcher on arrival at the medical care facility. Hand injuries often are painful and provoke anxiety. Placing the patient in a supine position prevents unexpected vasovagal syncope. The recumbent position allows for easy placement of the hand in an elevated position to decrease the swelling that occurs after injury.

Any rings or constricting jewelry are removed to prevent ischemia of a digit. Most rings can be removed by using a lubricant and applying gentle, persistent traction. Ring removal from swollen fingers can be accomplished by using a specially designed ring cutter and spreading the ring open with two Kelly clamps applied to the edges of the cut portion (see Fig. 2-1 ). Patients who are concerned about damaged rings can be reassured that jewelers can restore rings to their original condition. Another method for the removal of rings is shown in Figure 13-1 . Umbilical tape or O-silk suture can be wrapped firmly around the finger and passed under the ring with a small forceps. The ring is extracted as the tape or suture is unwound proximally to the ring.

Occasionally, a patient arrives with a ring or band made of hardened steel or even titanium. If routine removal procedures, including cutting, do not succeed in removing the ring, the following procedure can be tried :

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Wrap elastic tape, 1 inch in width, tightly around the finger starting from the tip of the finger and moving toward the ring. Extra wraps adjacent to the ring may be needed, because more edema accumulates in that area.
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Elevate the hand above heart level for 15 minutes. Securing the arm gently to an IV pole will help. Apply an ice pack to the finger as well.
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After 15 minutes, apply a blood pressure cuff to the upper arm and inflate it to 250 mm Hg to prevent blood refilling the arm and finger.
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Quickly remove the tape, apply a light coating of lubricant to the finger, and remove the ring.
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If this procedure does not work the first time, there may be residual edema. The procedure can be repeated.

Most patients attempt to bandage the injured hand before proceeding to a medical care facility. These hastily fashioned, unsterile dressings should be removed carefully. Until treatment can be administered, sterile sponges moistened with normal saline should be applied, followed by a 2- or 3-inch gauze wrap. Any active bleeding requires manual pressure with gauze sponges. An extremity tourniquet rarely is needed to stop excessive hemorrhage.

If the wound is grossly contaminated with soil or other debris, and if there will be a delay before treatment can be administered, the hand is cleaned gently with a wound-cleansing agent followed by irrigation with normal saline. The chance of infection increases with each passing hour from the time of injury to repair. Early cleansing and irrigation can extend this safe period.

It is a common but unsupported practice to soak hand injuries in a wound-cleansing solution before repair. Soaking is believed to loosen debris and to help kill contaminating bacteria, but there is no scientific evidence to support these beliefs. Brief extremity immersion is recommended only to help remove gross soil and debris from the area surrounding the wound before proper skin cleansing and wound irrigation is undertaken.

Terminology

Knowledge of conventional terminology is required to properly document and communicate information about injuries to the hand and fingers. All lacerations and wounds can be located accurately by the use of appropriate terms. A ½-inch laceration on the back of the index finger at the first knuckle is described accurately as “a 1-cm superficial laceration of the index finger on the dorsal surface at the proximal interphalangeal joint.” Figures 13-2 and 13-3 illustrate the various descriptive landmarks and joints. The back of the hand is the dorsal surface, whereas the palm side is the palmar or volar surface. Common landmarks of the palm are the thenar and hypothenar eminences. The digits are best remembered and recorded, when necessary, as the thumb, index, middle, ring, and little finger. Each segment of the finger is named for the underlying bony phalanx. Although the joints are descriptive of their location, it is the convention to use the abbreviations noted in Figure 13-2 .

Instead of using terms such as inside and outside or medial and lateral, the sides of the hands and fingers are referred to as radial and ulnar . This convention eliminates the confusion elicited by the other terms. Any injury to any surface on the side of the hand or finger corresponding to the radius is so described. A laceration of the side of the little finger is either radial or ulnar depending on whether it is on the side of the ulna or on the side of the radius (see Fig. 13-3 ).

Patient History

Certain key historical facts help determine the timing and choice of repair and other supportive treatment. As previously discussed, the amount of time that has elapsed from the time of injury influences the decision of when to repair the wound. Clean wounds that are caused by shearing forces probably can be safely repaired 6 to 8 hours after the injury. Wounds caused by tension and compression mechanisms are more vulnerable and should be considered for closure sooner. Severely contaminated wounds, or wounds caused by mutilating forces, are best left for consultation and possible delayed closure. This decision is made on a case-by-case basis.

A seemingly innocuous mechanism of injury is the puncture wound of the hand. Although the entry point is quite small and appears innocent, special care has to be taken not to miss a transected nerve or tendon. In addition, the possibility of a foreign body being retained in a puncture wound has to be considered, and a radiographic examination should be performed when the suspicion is raised.

Other historical points of importance are the patient’s hand dominance, history of previous hand deformities, profession, and hobbies. Although these considerations are seemingly not very important for patients with emergency lacerations and wounds, a simple matter of a mismanaged fingertip injury can significantly affect an activity such as playing the guitar. For a guitar player, every step is taken to preserve the nail matrix. Preservation attempts might not be as crucial for an individual who does not require this anatomic part for either a job function or for a hobby.

Any allergies the patient may have should be verified when taking the history. Many drugs, including tetanus toxoid, local anesthetics, pain medications, and a variety of antibiotics, are administered to patients with hand injuries.

Examination of The Hand

The actual examination of the injured hand consists of careful inspection of the wound and thorough functional testing. Nerve function is evaluated by assessment of motor and sensory components. The integrity of tendons most often can be determined by specific functional maneuvers. Because tendons often are only partially severed, and function is preserved, direct visualization by exploration may be necessary. For wounds in emergency situations, circulation is so profuse that severed, bleeding vessels, which travel in neurovascular bundles, often are better indicators of nerve injury than actual threats to perfusion of the hand or finger. When necessary, radiographs are obtained to assist in the examination to rule out fractures or foreign bodies. Finally, there is no substitute for exploration and direct visualization to discover if there is structural damage of any type.

Nerve Testing

Motor Function

Three major nerves are responsible for motor and sensory function of the hand. The radial nerve innervates the extrinsic muscles of the forearm that are responsible for extension of the wrist and fingers. This nerve does not innervate any muscle within the confines of the hand itself. The motor function of this nerve is tested by having the patient dorsiflex his or her wrist and fingers against a resisting force, such as the examiner’s hand ( Fig. 13-4 ). Intact motor strength, as provided for by an intact radial nerve, should prevent the examiner from overcoming the dorsiflexed wrist when a good deal of counterforce is applied.

In addition to the flexor carpi ulnaris and part of the flexor digitorum profundus, the ulnar nerve innervates most of the intrinsic muscles of the hand itself, including all of the interossei muscles and the little and ring finger lumbricals. The motor portion of this nerve is responsible for the ability of the fingers to spread and close in a fanlike manner. A specific test for ulnar motor function is to have the patient adduct (close) the fingers against an object, such as a pen ( Fig. 13-5 ). With an intact nerve, the examiner cannot easily remove the object. Each finger can be tested in this manner.

The median nerve provides motor innervation to wrist flexors, the flexor digitorum superficialis, part of the flexor digitorum profundus (shared with the ulnar nerve), and the remaining intrinsic muscles of the hand, most notably the muscles of the thumb that are responsible for opposition. To some degree, opposition also is mediated by the adduction component of the interossei as supplied to the ulnar nerve. The testing maneuver is completed by having the patient oppose his or her thumb with the tip of the little finger. A properly made “ring,” consisting of the thumb and little finger, should be difficult to break by the examiner if the median nerve is intact ( Fig. 13-6 ).

Sensory Function

A variety of stimuli can be delivered to the skin of the hand to test sensory function. Gross touch with a blunt object is the easiest but is the least specific. Gross touch can be useful, however, for rapid screening to assess the possibility of nerve damage, especially when comparison testing of the injured and noninjured hands is done. If there is a nerve injury, the patient often is able to report a difference in feeling. Pinprick stimulus is the most commonly used modality for testing. Pinprick is useful when alternated with blunt stimulus. In a complete nerve transection, the patient cannot tell the difference between a blunt and a sharp stimulus. Pinprick testing nevertheless is difficult to assess on the fingertips, especially in a manual laborer whose fingerpads are covered with thick calluses.

A more accurate method of assessing sensory function is two-point discrimination. A paper clip can be fashioned so that two ends can be opened or closed to varying distances from each other ( Fig. 13-7 ). Because the ulnar and radial side of each finger has separate innervation, testing each side of the finger is necessary. A patient with a normally innervated finger should be able to distinguish two simultaneously delivered stimuli that are 6 mm or more distant from each other. Most patients can tell a difference down to 3 mm. When identification of separate stimuli is reported by the patient at 8 mm apart or more, the examination is clearly abnormal.

Of the major nerves, the radial nerve provides the least important sensory innervation to the hand. This nerve supplies sensation to the radial portion of the dorsum of the hand, the dorsum of the thumb, and the proximal portion of the dorsal side of the second and third digits and half of the ring finger ( Fig. 13-8 ). To test gross radial sensory function rapidly, a stimulus is supplied to the first web space, which is an area of pure radial distribution.

Sensory distribution of the ulnar nerve includes the dorsal and volar surfaces of the ulnar side of the hand, the entire fifth digit, and the ulnar half of the fourth digit. To test an intact sensory component of the ulnar nerve, an appropriate stimulus is delivered to the area of purest ulnar distribution: the tip of the fifth digit.

The remainder of the hand is innervated by the median nerve. The area of sensory distribution comprises the radial side of the palm; volar surfaces of the thumb, index, and middle fingers; and the radial half of the ring finger. As depicted in Figure 13-8 , median nerve innervation extends to the fingertips of the thumb, index, and middle fingers, including the dorsal portion of the distal phalanges. Pure median sensation can be found at the tip of the index finger.

More common than injuries to the major nerves are injuries and lacerations to the digital nerves that lie within the hand itself. There are four digital nerves for each digit. The two palmar nerves ( Fig. 13-9 ) are the largest and most important. (The others are the dorsal digital nerves.) Sensation is carried through these two nerves to the palmar surface and the nail bed area of the fingertip. A laceration or puncture wound to the palmar or dorsal surface of the hand or to any individual digit requires careful sensory testing of the digits distal to the injury.

As previously described, a variety of stimuli can be used for sensory testing. The most accurate method of detecting a nerve injury in this setting is the two-point discrimination test. Objective documentation of digital nerve injuries is not always possible at the time of the first examination immediately after injury. Patient pain, anxiety, and factors such as the presence of callused hands can interfere with two-point testing. Even though stimulus testing is inconsistent and does not clearly document nerve injury, any subjective “numbness” reported by the patient has to be taken seriously, and consultation with a hand specialist should be considered. Under these circumstances, it is common to close the skin and to refer the patient for evaluation within a few days after the initial care.

Tendon Function

Extensor Function

Extensor tendon function can be tested simply by having the patient extend his or her fingers against the force of the examiner ( Fig. 13-10 ). Although this maneuver appears to be easy enough, there are complexities of the tendon anatomy that can cause confusion when results of the examination are interpreted. The wrist itself has three main extensor tendons that are responsible for proper extension at the wrist. If these tendons are cut, the wrist can be extended by the finger extensors but with far less force, and that force can be overcome easily by the examiner. The thumb is served by an abductor and two extensor tendons. If one extensor is cut, the second still can function. Each finger has one main extensor tendon responsible for extension with power. The second and fifth digits, however, have small accessory tendons that can extend these fingers weakly if the main extensors are knocked out of action.

Another anatomic point that can possibly cause misinterpretation in the examination for extension of the digits is the fact that as extensor tendons cross the wrist, they flatten out and interconnect with other extensors over the dorsum of the hand ( Fig. 13-11 ). Weak extension of a severed tendon can occur by the action of the adjacent interconnecting tendon. These interconnections also can prevent severed extensor tendons from slipping back into the forearm after they are cut. This anatomic property of extensors makes anastomosis easier for extensors than for flexor tendons, because the two severed ends can be readily retrieved during repair.

When there is doubt about extensor tendon function, careful exploration has to be performed through the laceration itself. Extensor tendons are superficial and can be identified easily with proper and gentle exposure. A key factor to remember is that the position of the hand at the time of examination and exploration may be different from the position of the hand during injury. If that should be the case, the actual laceration to the tendon may be at a location away from the laceration on the skin ( Fig. 13-12 ). Active flexion/extension of the finger to cause the tendon to slide back and forth is encouraged during the exploration.

Flexor Function

The thumb has only one flexor tendon, but the index, middle, ring, and little fingers have two main flexor tendons. The volar surface of the wrist is a complex and vulnerable area, replete with important structures. As illustrated in Figure 13-13 , the median nerve lies just deep and radial to the palmaris longus, the most superficial tendon. Even lacerations to the wrist that appear trivial can cause serious tendon and nerve damage.

The flexor tendons to each finger are paired. The flexor digitorum profundus tendons are responsible for power and mass action, such as is needed for gripping. These tendons run deep to the flexor digitorum superficialis tendons, but at the level of the middle phalanx, the profundus splits through the superficialis and goes on to attach to the distal phalanx ( Fig. 13-14 ). To test profundus function, the action of the sublimis tendon has to be blocked by holding each digit, one at a time, in extension at the middle phalanx ( Fig. 13-15 ). The patient is asked to flex the distal phalanx, which now can be accomplished only through the action of the profundus. During this maneuver, 60 degrees of flexion is normal.