Specific issues relative to wounds and lacerations of the arm and hand include potential injury to the arteries, nerves, and tendons that lie close to the skin and the impact of these injuries on the use of the hands in daily and occupational life. Injuries may be classified as either isolated or combinations of closed crush, simple lacerations, open crush, partial amputation, and complete amputation.

HISTORY AND EXAMINATION

Specific considerations in the history include patient age, occupation, mechanism of injury, and hand dominance. Age is important because the potential for bony injury increases with decreasing bone density, and the likelihood for healing and functional recovery decrease because of loss of elasticity. Mechanism of injury identifies wounds that are more prone to infections. Note the time from injury to repair. There is no distinct threshold for infection from time from injury to closure, but wounds sutured >12 hours after injury could be more prone to infection.^1,2

Examination of arm and hand injuries begins with inspection and continues with evaluation of motor and sensory nerve function, tendon/ligament integrity, and assessment of perfusion. During inspection, observe the position and stance of the arm, hand, and digits. Identify exposed tendon or bone, and note the location of the wound relative to major arteries, nerves, and tendons. Explore the wound carefully for possible foreign body, debris, or other visible contaminants. Note significant soft tissue avulsion or loss of length of the injured part, as these findings may be indications for operative repair.

Active and Passive Movement

Examine active motion and resistance to passive movement. Patients with a painful injury may be unwilling to move the affected extremity. After checking sensory function, local anesthesia may be required to obtain an adequate motor exam. The long-held belief that a local anesthetic with epinephrine should not be used for digital nerve blocks has been disproven, and agents containing epinephrine are acceptable for digital nerve blocks.^3,4,5

Because there are several muscles with cross innervations, the most distal pure motor function of each major nerve should be tested against resistance (Table 43-1).

Individually assess each tendon in, and adjacent to, the injured area. For injuries to the hand and fingers individually examine the extensor digitorum, flexor digitorum profundus, and the flexor digitorum superficialis of each digit. The flexor digitorum superficialis, which splits and inserts at the proximal interphalangeal joint, can be examined by holding all other digits in extension and flexing the proximal interphalangeal joint against resistance. The flexor digitorum profundus, which runs below the flexor digitorum superficialis past the split to attach at the distal interphalangeal joint, can be examined by holding the proximal interphalangeal joint in extension and flexing the distal interphalangeal joint against resistance. The extensor digitorum can be assessed by sequentially flexing the digit at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints and having the patient extend the digit. Extension should be performed first against gravity and then against resistance applied by the examiner. Weak, limited, or painful movement suggests partial involvement of a tendon. Abnormality in motor nerve or tendon function testing warrants a more in-depth examination, including visual inspection and appropriate consultation.

Sensation and Two-Point Discrimination

Assess pain and touch in the median, ulnar, and radial nerve distributions (Table 43-2 and Figure 43-1). For injuries distal to the midpalm, assess the digital nerves by static two-point discrimination, testing longitudinally along the ulnar and radial aspect of the volar pad of the potentially involved digits. Static two-point discrimination is evaluated by using electrocardiogram calipers or a paper clip bent into a “V” shape with the two ends separated by approximately 5 to 6 mm. During testing, the two points should not cross the midline, and each stimulus should be timed 3 to 4 seconds apart. Normal two-point discrimination is defined as <6 mm; good is 6 to 10 mm, fair is 11 to 15 mm, and poor is >15 mm. Two-point spatial acuity of touch diminishes with age. Young (18 to 33 years) patients have a mean two-point acuity of 2 mm, whereas elderly (>66 years old) patients have a mean acuity of 5 mm.⁶ The two most important areas to maintain sensation are the ulnar side of the distal thumb and the radial side of the index volar pad to preserve pinch sensation.

Vascular Assessment

Intact radial and ulnar pulses and capillary refill are usually adequate to exclude significant vascular injury. However, an arterial injury proximal to the wrist may not be obvious as a result of collateral circulation. To better assess the integrity of the radial and ulnar arteries, perform Allen’s test. The test is performed by first instructing the patient to make a fist as tight as possible. Then, apply digital pressure to both the radial and ulnar artery at the volar aspect of the wrist. Next, while maintaining compression of the radial and ulnar artery, have the patient open the hand—a blanched palm indicates that arterial inflow is occluded. Now release the radial artery, and note the time for the hand to return to normal color. Repeat the entire process, this time releasing and assessing flow from the ulnar artery. If the patient cannot make a fist, occlusion of both arteries will still blanch the hand, but the color change will not be as evident or pronounced. Refill times >3 seconds raise suspicion for a significant vascular injury.

A Doppler probe is useful to detect a diminished pulse, detect flow in digital arteries, and to calculate an arterial pressure index. The arterial pressure index is the ratio of the systolic blood pressure between the injured and the uninjured side. It is useful to assess the vascular integrity of an injured arm or leg. To obtain the index, place a blood pressure cuff proximal to the ankle or wrist of the injured limb and distal to the wound. Then use a Doppler probe to determine the systolic pressure at the dorsalis pedis or posterior tibial artery, or the radial or ulnar artery. In the absence of a diminished pulse or an arterial pressure index ratio <1.0, the likelihood of a clinically significant occult arterial injury is exceedingly small (sensitivity 95%, specificity 97%).^7,8 Lack of obvious arterial bleeding does not rule out arterial injury because cleanly transected arteries may contract and prevent obvious bleeding. Any abnormal findings warrant consultation with a vascular surgeon as well as with a hand surgeon.

IMAGING

Obtain radiographs with anteroposterior, oblique, and lateral views if bony injuries, foreign bodies, or joint penetration are suspected. Additional oblique views of the hand and digits are useful to visualize small areas with overlapping bones. For isolated finger injuries, dedicated anteroposterior and lateral radiographs of the involved digit(s) are preferred, as the detail on hand films alone is often not adequate for complete visualization of small, subtle fractures. Plain radiography visualizes radiopaque objects as small as 1 mm. When there is suspicion for a radiolucent-retained foreign body, especially wood, other imaging modalities (US, CT, or MRI) may be necessary (see chapter 45, Soft Tissue Foreign Bodies).

WOUND VISUALIZATION AND TOURNIQUET APPLICATION

Because wounds and the affected structures are often small, patient positioning, bright lighting, and a bloodless field are necessary for wound evaluation. For some injuries, a bloodless field may require a proximal tourniquet to temporarily halt arterial inflow and allow adequate visualization of the injury. Penrose (rubber) drains are typically used to tourniquet an injured finger, and pneumatic tourniquets placed around the arm are used with forearm and wrist injuries. To tourniquet a digital injury, place a 1-in. Penrose drain around the base of the finger, stretch the drain away from the hand, and secure the drain with a clamp or hemostat. If time allows, the digit can be exsanguinated before tourniquet placement by wrapping the digit with the Penrose drain from distal to proximal, then carefully removing the drain from distal to proximal before securing it around the base of the digit. Excessively high pressures and tourniquet times >15 to 20 minutes can cause neurovascular damage and may be avoided by limiting the stretch of the drain to no more than 50% of the original length.⁹

For more proximal injuries, especially those with brisk arterial bleeding, an inflated manual blood pressure cuff is used. Esmarch’s technique is as follows: Elevate the injured extremity and apply an elastic bandage starting distally and proceeding proximally to the area where the cuff will be applied. This will help to exsanguinate the limb and prevent backflow bleeding. The cuff is applied around the upper arm and inflated to pressures above the systolic blood pressure of the patient, but not to exceed 250 mm Hg. The cuff tubing is clamped with a hemostat instead of closing the air release valve to prevent slow air leakage. The maximum cuff inflation time is limited to 30 minutes to limit ischemic damage to the distal muscles and nerves.

Once adequate visualization is obtained, examine the area for foreign bodies and tendon and joint capsule injuries. Examine the arm and hand in a variety of positions, including the position of injury and a full, passive range of motion, to avoid missing injuries that may move out of the field of view when the extremity is examined in a neutral position. Examine lacerations near a joint carefully to identify violation of the joint capsule. If the location and depth of the injury raise the question of extension into the joint capsule, joint injection for a saline load test should be done. After standard sterile preparation of the area, inject the joint with normal saline at an area away from the laceration. Inject 5 mL in the wrist and 1 to 2 mL in finger joints.¹⁰ Inject sufficient amounts of saline to adequately stress the capsule. False-negative results may be obtained if too little fluid is injected.^11,12 Fluid dripping from the joint indicates an open joint capsule and requires specialty consultation. For small joints or questionable exams, a few drops of sterile fluorescein for IV use (Ak-Flor^®) may be added to the injected saline and the joint examined with a Wood’s lamp for evidence of fluorescent effluent. Do not use methylene blue because it stains the intra-articular surfaces and may affect operative management of intra-articular injuries.

WOUND DRESSING AND POSTREPAIR CARE

After the injury is repaired, apply antibiotic ointment to the repaired incision/sutures and cover the wound with a nonadherent dressing. Wrap the area loosely with a soft dressing to allow for adequate circulation. A small portion of the fingernail or volar pad should remain visible to allow serial assessment of capillary refill in patients with digital injuries. Certain injuries, especially large lacerations in close proximity to a joint and those with tendon involvement, may be splinted for protection and limitation of pain. A padded aluminum splint is satisfactory for isolated digital lacerations. Provide adequate analgesia and remind the patient to keep the injured extremity elevated above the level of the heart to reduce edema. A follow-up wound check is recommended within 48 to 72 hours. Sutures are usually removed 8 to 10 days after the injury.

Prophylactic antibiotics are not needed for uncomplicated hand lacerations.² The definition of an uncomplicated hand laceration is as follows: (1) not caused by a human or animal bite; (2) not associated with a burn; (3) not complicated by a fracture through bone or a joint; (4) not involving tendons, bones, large vessels or nerves; (5) no severe soft tissue damage or maceration.² Antibiotics are generally given for complicated hand lacerations, mammalian bite wounds, injuries >12 hours old, contaminated wounds, injuries with exposed bone, or injuries occurring in patients with concurrent medical problems that may affect wound healing (i.e., diabetes, renal or peripheral vascular disease, immunocompromise).^13,14,15 Antibiotics should be chosen to cover suspected contaminants and pathogens and should be given early in the ED by a route that quickly achieves high blood and tissue concentrations.

Provide tetanus immunization or booster as needed.

Indications for admission to the hospital include injuries that require repair in the operating room, those that require a course of IV antibiotics, or the presence of social issues such as abuse cases, homelessness, or other factors affecting the patient’s ability to follow basic aftercare instructions.

INJURIES IN CHILDREN

Because of the presence of an open epiphysis in children, a fracture can be difficult to identify using plain radiographs. It is often necessary to obtain radiographs of the unaffected side for comparison. If a complicated repair is indicated and the child is unable to tolerate the procedure after local anesthesia alone, procedural sedation may be required. The continuous high activity level of children makes keeping dressings intact a problem, rendering routine hand dressings and protective finger splints ineffective. If the dressing and immobilization is essential to wound healing, the child should be placed in a bi-valved long arm cast.

The forearm has six extensor compartments located dorsally, all of which are innervated by the radial nerve (Table 43-3). Tendons and nerves distal to the wound should be individually examined.

The skin on the dorsum of the forearm and hand is thin and lacks underlying tissue, which allows skin avulsion to occur easily and makes wound edge approximation sometimes difficult.¹⁶ For most lacerations, simple 5-0 nonabsorbable percutaneous sutures should be adequate for closure. To provide better cosmesis for injuries to the dorsum of the hand, we recommend subcuticular stitches with 5-0 absorbable material. A pull-through subcuticular closure with nonabsorbable suture is preferred for linear lacerations (Figure 43-2).¹⁶ For deep wounds that penetrate through the muscle fascia and lacerate the muscle belly, closure of the fascial defect with 4-0 absorbable suture is generally recommended. However, deep sutures increase the potential for infection in a contaminated wound.

Patients with lacerations to the dorsum of the hand should be questioned about the possibility of a clenched fist injury or “fight bite,” wounds created by the patient throwing a punch and impacting the front teeth of the intended target and producing a small laceration (3 to 5 mm) over the dorsal metacarpophalangeal joint.¹⁷ Extension of the hand after the fight deeply inoculates oral bacteria into the wound. Staphylococcus aureus is the most common bacterial species isolated from human bite wounds, followed by Streptococcus spp., Corynebacterium spp., and Eikenella corrodens. In clenched fist injury infections, polymicrobial involvement is the rule. Human bites can also transmit herpes, actinomycosis, syphilis, tetanus, and hepatitis B and C.¹⁷ Bites are not the only way to inoculate the hand with human oral flora; significant hand and finger infections have been reported after toothpick injuries. Patients sustaining such puncture wounds should receive antibiotics to protect against the above-mentioned bacteria.¹⁸