Hand Injuries, Part 1:

More than 30% of industrial accidents and approximately 75% of industrial injuries leading to partial disability involve the hand or hands.¹ Each year, more than 16 million people in the United States injure their hand(s) so severely that they seek emergency care.¹ Successful treatment of these patients requires a knowledge of hand anatomy and an understanding of the various types of possible injuries.

In this 3-part series, we review the evaluation and management of the most common hand injuries. Here we describe the essentials of the history and general evaluation. We then detail the specifics of the neurologic, vascular, and musculoskeletal examinations. Finally, we discuss how to cleanse, anesthetize, and close wounds in order to minimize the risk of infection and potential complications.

In coming issues of CONSULTANT, we will focus on the clinical presentation and management of a range of common nerve, vascular, tendon and ligament, fracture, dislocation, nail bed, and bite injuries to the hand.

PRIMARY EVALUATION

As with any injured patient, first consider airway, breathing, and cardiovascular stability and search for associated injuries. Do not be distracted by the bloodied and deformed hand of a patient who suffers from a more serious-albeit less obvious-injury.

Every trauma victim merits a rapid but systematic and complete primary evaluation. Once you have determined that the patient is stable and has no superseding injuries, proceed with a detailed history and hand examination. Begin by removing any rings (see page 202).

History. A thorough, guided history is essential. The mnemonic "AMPLE" can help you remember the important components of a complete history:

•Allergies. Is the patient allergic to medication or other physical substances (eg, antibiotics, anesthetics, latex gloves) that may be used during treatment?

•Medications. Does the patient take any licit or illicit medications (including alcohol)?

•Medical history and prior injuries. In particular, document any previous injuries to the affected hand. (This information may influence the diagnosis, treatment, and outcome of the present injury.) Also, ask the patient which is his or her dominant hand.

•Last meal. When did the patient last eat? This is important if immediate surgery is necessary.

•Events. What happened before and after the trauma? Did the patient lose consciousness? What measures have been taken by the paramedics or referring physician since the injury?

Documentation. Meticulous record keeping is, of course, a requisite to good medical care. Proper documentation provides follow-up physicians with crucial information. Thoroughly charting your findings before any radiologic or therapeutic manipulations also documents an initial, accurate assessment of the hand. Consequently, any future complications will be recognized as signs of progressive dysfunction rather than an initial oversight.

GENERAL HAND EXAMINATION

Be sure that the patient is comfortable and the overhead lighting is strong. Having the patient lie supine facilitates cooperation and prevents vasovagal syncope.

The skin.Begin by observing the general appearance of the hand and fingers. What color is the skin? Is cyanosis, pallor, erythema, ecchymosis, or blistering present? Is there edema? Is there evidence of chemical exposure?

The fingers.Note the "attitude," which describes the curvature and symmetry of the injured hand and fingers, and compare it with that of the opposite hand. Are any fingers held in extension? (This indicates flexor tendon injury.) When the fingers are held in flexion, is there any overlap? (This suggests a possible displaced fracture.)

Observe the fingertips "end on" to note any rotational deformity. When the fingers are held in a resting position, is the normal "cascade" (staggered position of each fingertip) disrupted? (This indicates injury to the extensor tendons.²)

The wound. Are there any lacerations or abrasions? Hemostasis is critical to wound visibility; to reduce bleeding, be sure that the open wound initially has a sterile compression dressing (wet with sterile saline) in place and consider elevating the arm. When you are ready to examine the open wound, gently remove the dressing and determine whether hemostasis is adequate.

If bleeding continues despite a sterile compression dressing, you can usually improve wound exposure by judiciously applying a blood pressure cuff to the upper arm and inflating it to 100 to 150 mm Hg above the systolic blood pressure. To minimize patient discomfort and the risk of ischemic injury when using the cuff, only rarely should the inflation time exceed 30 minutes. These measures will stop most bleeding.

In the rare event that bleeding persists, suture ligature may be necessary. However, be aware of the high risk of simultaneously ligating a nearby nerve and causing permanent damage. Although you may be tempted to clamp a bleeding vessel to achieve hemostasis, do not do so under any circumstances: the risk of potential complications, such as nerve, tendon, and/or vascular injury, is too great.

NEUROLOGIC EVALUATION

Next, assess the motor and sensory functions of the injured hand. Two peripheral nerves, the ulnar and median, enter the hand at the volar aspect; the radial nerve crosses the radial styloid from the volar to the dorsal surface at the level of the wrist (Figure 1). Although anatomic variations are prevalent, a general understanding of the muscle innervations of each nerve is paramount to a successful neurologic examination.

Motor testing. The mnemonic "RUM" (radial, ulnar, median) can help you remember to test each of these nerves. The results of 3 simple motor tests provide an accurate assessment (Figure 2):

•If the patient can extend the wrist and fingers and extend or abduct the thumb, you may be confident that the motor function of the radial nerve is intact.

•If the patient can abduct the little finger, then the motor function of the ulnar nerve is preserved.

•If the patient can maintain a strong thumb and index finger "pinch," or touch the tip of the thumb to the tip of each finger, be assured that the median nerve motor function is undamaged.

Sensory testing. Three key locations to examine are illustrated in Figure 3:

•The dorsal web space between the thumb and index finger (radial nerve).

•The volar surface of the finger pad of the fifth digit (ulnar nerve).

•The distal radial aspect of the volar surface of the index finger (median nerve).³

Determine and document the sensation to light touch and pain. With the patient's eyes closed, use the ends of a straightened paper clip like calipers to test 2-point discrimination on each digital pulp region and on the dorsal metacarpal thumb region. Generally, a patient should be able to discriminate between 1 and 2 points that are 5 mm apart, although there might be slight individual variations. By comparing these results with those of the opposite hand, you can detect sensory dysfunction most accurately.

A patient who detects only 1 point when 2 should be detected may have sustained some nerve injury. Conversely, a patient who repeatedly detects 2 points when there is only 1 may be guessing or deliberately trying to mislead you, since there is no pathophysiologic explanation for this result.

Sweat production testing. In addition, assess the sweat production of the palmar skin surface, because injury to a nerve also disrupts the sympathetic nerve fibers responsible for sweat production. The palm and web spaces are dry in an injured hand but may feel moist if no nerve injury has occurred.

Skin-wrinkle testing. You can also easily evaluate the functional integrity of the nerves by soaking the injured hand in a basin of sterile water for several minutes. If a particular region has sustained nerve damage, the overlying skin will remain smooth, whereas the surrounding skin will become wrinkled. Both sweat production testing and skin-wrinkling testing assess the same underlying nerve mechanism.

VASCULAR EXAMINATION

The vasculature of the hand is complex and replete with normal variants. Following certain basic principles ensures a quick and thorough vascular examination.

The ulnar and radial arteries supply the hand; each enters from the volar aspect of the wrist, where you can usually palpate them. Anastomosis of branches from each artery produces superficial and deep palmar arches. The digital arteries branch directly from these arches (see Figure 1).

History. The history of the injury is of great importance in determining the presence of a vascular injury. A deep penetrating injury with subsequent pulsatile bleeding obviously suggests arterial disruption. Such bleeding may be the only clue to arterial injury, since the flow may stop or slow greatly after spontaneous vessel retraction and constriction. Finally, previous injury to the hand may raise the specter of preexisting vascular compromise or a predisposition to certain vascular compromise.

Physical examination. Inspect the hand for disrupted vascular integrity or inadequate collateral blood flow between the two arterial systems in every patient with a hand injury. Initially, observe the wound for active bleeding and for visible blood vessels.

The rule of the 5 P's-pulses, pallor, pain, paresthesia, and paralysis-will remind you of all the components of a thorough vascular examination. As mentioned, be sure to first control any active bleeding.

Begin by palpating the arterial pulses as they cross the volar aspect of the wrist. However, you cannot fully rely on palpable pulses because vessel contraction and hemostasis can maintain a pulse, even in the presence of significant injury to the ulnar or radial artery.

Check the capillary refill time of each nail bed. Rather than attempting to compare the findings with a standard filling time, simply compare them with those of the opposite hand (if uninjured). If this is not possible, remember that a capillary refill time of less than 2 seconds is usually considered normal.

Pain distal to the injury that is out of proportion to the wound itself may indicate ischemia. Any paresthesia or paralysis of distal muscle groups may indicate vascular compromise, although these signs are not very specific.

You can use the Allen test to demonstrate adequate collateral blood flow between the ulnar and radial arteries. With your thumbs, apply sufficient pressure to occlude both arteries at your patient's wrist while he repeatedly opens and closes the hand until you note blanching. At that point, release the pressure on the radial artery and watch for a red flush of normal color in the palms and fingers as arterial flow returns. Then repeat this for the ulnar artery.

SKELETAL EXAMINATION

Fractures.Always check for anatomic deformities of the hand and compare the injured with the uninjured side. Certain hand fractures are associated with characteristic features, such as the direction and degree of angulation and displacement. For instance, a proximal phalanx fracture usually angulates to the volar aspect, while a metacarpal shaft fracture typically angulates in the dorsal direction.³ These features are determined by the mechanism of injury and the sum of the forces exerted on the bones by the various musculotendinous units.

Discrete point tenderness characterizes the site of a fracture in almost all circumstances. Careful palpation aids in identifying the radiographic views that will best delineate the fracture. Conversely, a previous bony injury will not be tender to palpation despite radiologic evidence of fracture.

Have the patient fully flex the digits while holding the metacarpophalangeal joints at about 45 degrees of flexion. Observe the axes of these flexed fingers: they should not overlap, and they should all point down toward the scaphoid bone in the wrist (Figure 4). In addition, palpate the carpal bones; any obvious defects or tenderness may indicate a possible fracture.

Radiography is an essential part of the skeletal examination; however, bear in mind that some acute fractures may not be visualized initially. (This is because osteolysis, the first phase of fracture healing, causes the fracture line to appear more radiolucent at 7 to 10 days, before callus formation begins.) Therefore, it is often wise to splint patients presumptively based on the history and examination, even if skeletal x-ray films appear normal.

Collateral ligament injuries. Rule out collateral ligament injuries of the interphalangeal and metacarpophalangeal joints. While the patient holds the finger in extension, test the joint space on the radial or ulnar side of the joint; do this by directing stress laterally toward the radial and ulnar sides of the joint.

Joint effusion and tenderness over the collateral ligaments are nonspecific indicators of collateral ligament tear, whereas joint opening in response to stress testing is the sine qua non of the diagnosis. It helps to compare the results with those of the uninvolved hand.

MUSCLE AND TENDON EXAMINATION

Aside from direct visualization, functional testing is the most reliable way to detect injuries to a muscle or tendon. Flexion and extension, although weakened, can still be accomplished with partially severed tendons. For this reason, it is important to test these functions against mild resistance.

Do not be surprised if a partially torn ligament or tendon snaps completely when you add resistance. This simply justifies your suspicion of a significant tear. The structure can then be appropriately repaired. Pain along the course of a tendon during motion is another indication of injury.

Thumb opposition.Our ability to oppose the thumb is one of our greatest physical assets. By testing this function in the patient with a hand injury, you are testing several intrinsic hand muscles.

Have the patient form a ring by touching the tips of each finger in turn with the tip of the thumb. To test the strength of the muscles innervated by the median nerve, try to force one of your fingers through each ring. The patient should be able to maintain a pinch strong enough to prevent you from breaking the ring.

Abduction and adduction. Use abduction and adduction of the fingers to test, respectively, the dorsal and palmar interossei. Have the patient perform extended-finger spreading and closing against mild resistance placed by your fingers.

Also, have the patient abduct and adduct the fingers while in extension and then make a fist. This provides a nonspecific test of the multiple intrinsic muscles in the hand.

Extension. When testing extensor function of the fingers, have the patient place the hand palm down on a table and extend each finger off the table, one at a time, against mild resistance. Inability to perform this exercise may indicate extensor tendon injury.

If you suspect an extensor tendon laceration but one is not readily apparent, place the hand in the position it was in when the injury occurred. Within the wound, the extensor tendon should be readily visible (Figure 5). Passive movement of the digit improves the likelihood of visualizing the injured tendon as it moves to and fro.

Flexion. To test the flexor digitorum profundus, ask the patient to place his hand palm up on a table. While restraining the proximal interphalangeal joint, have the patient attempt to flex the distal interphalangeal joint. Success indicates an intact flexor digitorum profundus in that digit.

Next, with the patient's hand in the same position, gently restrain 3 fingers while the patient attempts to flex the remaining fingers at the proximal interphalangeal joint. If this maneuver is successfully completed, the flexor digitorum superficialis in that digit is functional.

Then, have the patient flex the thumb so that it touches the hypothenar eminence and then try to pull the thumb out of flexion. This tests the flexor pollicis brevis and flexor pollicis longus. To test the function- al integrity of the extensor pollicis longus, have the patient place the thumb in the hitchhiker's position against resistance.

ANESTHESIA

Various types of anesthesia are available to assist you when evaluating and caring for hand injuries. Of course, a complete neurologic examination must be performed before you proceed with anesthesia.

Local anesthesia.You can adequately anesthetize most hand lacerations using local infiltration. Local anesthesia is usually sufficient for smaller and more superficial lacerations of the palm and dorsum of the hand. Be aware that injection may distort the wound and possibly cause the loss of valuable skin landmarks before closure, thereby making it difficult to repair the wound accurately.

Nerve blocks.These are also commonly used in the hand. Begin by inserting a 27-gauge needle approximately 5 mm deep in a perpendicular direction. Attempt to aspirate first to ensure that you have not entered a vessel. Gentle pressure on the plunger of the syringe makes this injection procedure more comfortable for the patient. While gently withdrawing the needle, slowly inject the anesthetic into the region surrounding the nerve.

Larger needles cause more pain and are more likely to cause nerve injury. Do not use lidocaine with epinephrine in the hand; doing so may cause vascular spasm and fingertip necrosis if injected directly into an artery. Usually, no more than 2 or 3 mL of lidocaine is required for a single nerve block in the hand. Inadvertent injection of larger amounts directly into the nerve is likely to cause nerve injury.

The objective of nerve block is not to inject directly into the nerve (this may cause injury) but rather to infiltrate the surrounding tissue so that the anesthetic can diffuse into the perineurium. If the patient complains of paresthesias when you insert the needle, withdraw the needle 2 or 3 mm before injecting the lidocaine.

Complete anesthesia may require 15 to 20 minutes to develop. Patience is thus imperative so that you avoid the common mistake of beginning to manipulate the patient before the full benefits of the nerve block are realized.

A valuable nerve block technique is the digital block, which provides anesthesia to either or both sides of an individual digit. Be sure that the needle penetrates the skin at the midline of the finger and is directed at a 45-degree angle to each side of the finger. Employing the aforementioned technique, inject the anesthetic from the dorsal surface of the finger into the radial and/or ulnar aspect of the proximal digit (Figure 6).

Alternatively, you can use an entry site on the palmar surface; inject the anesthetic at a depth of about 3 mm at the level of the distal palmar crease, where the flexor tendon crosses it. To anesthetize the thumb, make the injection at the volar aspect of the metacarpophalangeal joint bracketing the flexor tendon apparatus.

Interdigital web-space injections can also provide anesthesia to either or both sides of a single digit; some experts believe they are less painful. Such injections may be of greater benefit when adjacent sides of 2 fingers are injured. When making these injections, hold the needle parallel to the long axis of the fingers and direct it toward the wrist.

Although only rarely necessary, radial, ulnar, and median nerve blocks are generally effective and easy to perform. These blocks are recommended when a large area of the hand must be anesthetized.

Ulnar nerve block is achieved by injecting the anesthetic approximately 5 mm deep into the region just lateral to the ulnar pulse and beneath the flexor carpi ulnaris at the level of the proximal skin crease of the transverse carpal ligament. You may also need to inject the superficial ulnar styloid to effect a complete block.

Injecting anesthetic deep into the region between the radial pulse and the flexor carpi radialis at the level of the proximal skin crease blocks the discrete trunk of the radial nerve. A second and more commonly used procedure is local infiltration at the dorsal aspect of the metacarpophalangeal joint of the digit, where the minor branches of the radial nerve enter; this anesthetizes the individual digits. Extend the anesthetic wheal to include the distance from the radial to the ulnar border of the metacarpal head (approximately 2 to 3 cm) to block all the sensory branches.

The median nerve lies deep in the region between the flexor carpi radialis and the palmaris longus tendons. To anesthetize this nerve, inject between those two tendons at the level of the transverse carpal ligament.

EXAMINING AND CLEANSING WOUNDS

Now attend to any skin wounds in the injured hand. Do not overlook small disruptions in the skin, since they may accompany more serious underlying injuries and harbor foreign bodies.

After you have established adequate hemostasis, irrigate and cleanse the wound of any debris. High-pressure irrigation with normal saline is the most efficient way to clean an open wound, and it significantly reduces wound infection rates.

Begin by connecting a 19-gauge needle or intravenous catheter to a 30- to 35-mL syringe filled with the normal saline. After you don personal protective garb, depress the plunger as rapidly as possible while aiming the stream perpendicularly into the wound. This generates the 7 to 8 psi of pressure required to efficiently irrigate debris and bacteria from the wound. Although a bulb syringe provides a larger stream of water, it does not produce the requisite pressure.

The necessity of removing debris from heavily contaminated wounds outweighs the risk of slight subcutaneous tissue injury. Since high-pressure irrigation may be painful, we suggest anesthetizing the wound beforehand.

Do not apply scrubs and cleansers, including those containing iodine and hexachlorophene, directly to the wound. The current consensus is that these substances are toxic to wounds and that they delay healing by decreasing the migration ability and the life span of polymorphonuclear cells. Nevertheless, these topical anti-infective agents still have a role in cleaning the surrounding epidermis to produce a "sterile" field around which wound repair can occur.

CLOSING SKIN WOUNDS

There are 3 basic techniques for repairing skin injuries: primary, secondary, and delayed closure. Of course, effective anesthesia, cleansing, and irrigation must always precede closure.

Primary closure. Use this technique for wounds that are not heavily contaminated and that are less than 8 hours old. Primary closure involves taping or suturing the wound edges in approximation without causing inversion or overlap. Be sure to avoid any blanching at the wound edge; this indicates tissue ischemia at the margins and will compromise healing.

Secondary closure. This method is appropriate for wounds that are heavily contaminated or inaccessible to high-pressure irriga- tion, such as puncture wounds. Leave shallow wounds open and deep wounds packed open. Packing keeps the skin from closing over the wound, thus preventing abscess formation.

With secondary closure, the intent is to facilitate the formation of granulation tissue from within the wound. The obvious disadvantage is increased scarring.

Ideally, change and repack the dressing daily. Although you can easily teach patients how to perform these activities, be sure to consider the level of discomfort (physical and emotional) and the patient's pain tolerance and reliability to carry out the packing procedure before deciding on the appropriate degree of self-management.

Delayed closure. Apply this technique to repair wounds that are large, gaping, and heavily contaminated. Clean and (if necessary) debride the wound and pack it open, as you would for secondary closure. If no signs of infection are present after 3 to 5 days, remove the packing, debride the wound, and suture to close the wound.

Suturing. Use standard suturing methods when closing hand wounds. Usually, 4-0 and 5-0 prolene or nylon monofilament sutures are preferred. Given the paucity of subcutaneous tissue in the hand, avoid subcutaneous or layered closure techniques for the most part. Of note, deep sutures in the hand predispose to deep-space infections.

However, since circumstances do occasionally require a layered closure, use chromic catgut or synthetic absorbable sutures. Palmar epidermis is relatively thick, and the epidermis itself frequently desiccates and peels off. Deeper sutures, often involving a horizontal mattress technique, are thus required. Repair of web-space lacerations poses a technical challenge but can be facilitated by a vertical mattress technique.

Because so many joints exert tension in the hand, the skin tension is much greater than in most other parts of the body. To prevent wound dehiscence, sutures need to stay in place longer in the hand than in other areas of the body. Remove sutures after 7 to 14 days, depending on the proximity to a joint and the relative skin tension involved.

Splinting and taping.Stabilize a joint with a splint when there is concern that undue tension may cause wound dehiscence. Use sterile skin tape on very superficial lacerations when the patient seems reliable and compliant.

PREVENTING INFECTION

One of the most important goals of managing hand injuries is preventing wound infection. To this end, we invariably use high-pressure irrigation with normal saline on all skin wounds.

Infection-prone wounds require special attention. Although we rarely employ antibiotic prophylaxis in outpatients, we will do so when treating crush, grossly contaminated, and bite injuries (Figure 7). Special case-by-case consideration is required for patients who have diabetes or who are immunocompromised. If the patient's wounds are numerous, severe, from a crush mechanism, and/or grossly contaminated, we often initiate parenteral antibiotics in the emergency department before closure of the wound.

When you discharge a patient with an infection-prone wound, ask him to return for a wound check in 24 to 48 hours. Provide all your injured patients with clear and concise wound care instructions, and be sure to familiarize them with the signs and symptoms of infection.

References:

REFERENCES:1. Markovick VJ, Pons PT, Wolfe RE. Emergency Medicine Secrets. Philadelphia: Hanley & Belfus, Inc; 1993.
2. Hoppenfield S. Physical Exam of the Spine and Extremities. Norwalk, Conn: Appleton & Lange; 1976.
3. Lammers RL, Freemyer BC. Hand. In: Rosen P, ed. Emergency Medicine: Concepts and Clinical Practice. 3rd ed. St Louis: Mosby-Year Book Inc; 1992:544-588.
FOR MORE INFORMATION:

• Stone S, Carter WA. Wound preparation. In: Tintinalli JE, Kelen GD, Stapezynski JS, eds. Emergency Medicine-A Comprehensive Study Guide. 5th ed. New York: McGraw-Hill; 1999:284-286.