Intrinsic Musculature.: The intrinsic muscles of the hand include the muscles of the thenar and hypothenar eminences, the adductor pollicis, the interossei, and the lumbricals (Fig. 50-12). The thenar muscles cover the thumb metacarpal. This group includes the abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis. These muscles originate in the flexor retinaculum and on the carpal bones and insert at the base of the first metacarpal and first proximal phalanx. They act in concert with the long flexors and extensors to carry the thumb through its intricate range of motion. The muscles are evaluated by palpation of the thenar eminence for contraction as the patient brings together the tips of the thumb and little finger. They also can be tested by asking the patient to place the dorsum of the hand on a flat surface and to raise the thumb up straight to form a 90-degree angle with the palm. The thenar muscles usually are innervated by the motor branch of the median nerve. In some cases they may be partially innervated by the ulnar nerve.

The adductor pollicis arises from the index and middle finger metacarpals and inserts on the first proximal phalanx. This muscle is innervated by the ulnar nerve. Thumb adduction is tested separately by having the patient forcibly hold a piece of paper between the thumb and radial side of the index proximal phalanx. If the adductor pollicis is weak or nonfunctioning, the thumb IP joint flexes with this maneuver (Froment’s paper sign).¹⁰ In this evaluation, the two hands should be compared.

The lumbrical muscles arise from the sides of the flexor digitorum profundus (FDP) tendons; the interossei muscles lie between the metacarpal bones and originate from them. Both of these muscle groups insert in the extensor expansions of the index, middle, ring and little fingers and act on the fingers to flex the MCP joints and extend the IP joints. The radial two lumbricals are innervated by the median nerve, and the ulnar two are innervated by the ulnar nerve. The seven interossei (three palmar and four dorsal) can be considered together. They lie on either side of the finger metacarpals and are innervated by the ulnar nerve. The dorsal interossei abduct the fingers away from the midline; the volar muscles adduct the fingers. For an accurate test that isolates their function from the extrinsic muscles, the patient should place the palm flat on a table, extend the digit, and move it from side to side.

The hypothenar group of intrinsic muscles includes the opponens digiti minimi, the flexor digiti minimi, and the abductor digiti minimi. These muscles arise from the carpal bones and in the flexor retinaculum and insert on the proximal phalanx and metacarpal of the little finger. The flexor digiti minimi and abductor digiti minimi flex the proximal phalanx and abduct the little finger respectively. The three muscles are evaluated as a group by having the patient place the wrist in a neutral position and abduct the little finger (move it away from the other fingers) against resistance. This muscle mass is palpated at that time, and a dimpling of the hypothenar skin is noted. All of the intrinsic muscles of the little finger are innervated by the ulnar nerve.

Extensor Tendons.: The extensor tendons are on the dorsal side of the forearm, wrist, and hand. The nine extensor tendons cross the wrist joint dorsal to its axis of rotation, pass under the extensor retinaculum, and are separated on the dorsum of the hand by a series of six fibro-osseous canals or compartments. Figure 50-13 outlines the compartments and their contents. The fibrous roof of these compartments prevents the tendons from bowstringing dorsally during active finger extension, particularly when the wrist also is extended.

The first dorsal wrist compartment contains the tendons of the abductor pollicis longus, which inserts at the dorsal base of the thumb metacarpal, and the extensor pollicis brevis, which inserts on the proximal phalanx of the thumb. The abductor pollicis longus serves to abduct the thumb ray, or thumb digit and metacarpal bone, radially, and the extensor pollicis brevis acts primarily to extend the thumb ray at the MCP joint. These tendons are evaluated by having the patient abduct and extend the thumb with resistance applied to the thumb; they can be palpated on the radial side of the wrist during this maneuver.

Two tendons lie in the second compartment: the extensor carpi radialis longus and brevis. These tendons insert at the dorsal base of the index and middle metacarpals. They act primarily to extend and deviate the wrist radially. These tendons can be palpated by having the patient extend the wrist against resistance while making a fist.

In the third compartment, a single tendon, the extensor pollicis longus, arises from the deep muscles of the midforearm, passes around a bony prominence on the dorsum of the wrist termed Lister‘s tubercle, and inserts on the base of the distal phalanx of the thumb. This tubercle can be palpated just proximal to the wrist joint. The extensor pollicis longus forms the dorsal border of the anatomic snuffbox, and the abductor pollicis longus forms the volar border (Fig. 50-14). The floor of this area contains the radial artery and two carpal bones, the scaphoid and trapezium. The extensor pollicis longus functions to extend and adduct the entire first ray and extend and hyperextend the IP joint of the thumb. This muscle is evaluated by placing the hand flat on a table and having the patient lift only the thumb off the surface. Because the abductor pollicis brevis and the adductor pollicis add terminal extension, complete laceration of the extensor pollicis longus tendon may not eliminate the patient’s ability to extend the thumb.¹¹

The tendons that extend the fingers—the extensor indicis proprius and the extensor digitorum communis—are in the fourth compartment. The extensor digitorum muscle divides into four tendons proximal to the wrist. In the dorsum of the hand, these tendons are joined distally by fibrous interconnections called juncturae tendinum which help stabilize them to their insertions in the extensor expansions of the index, middle, ring, and little fingers. The extensor digiti minimi is contained in the fifth dorsal compartment. Both the extensor indicis proprius and the extensor digiti minimi typically lie ulnar to their respective common extensor tendons. The dual extensor system for the index and small fingers gives these two digits extension independent of the other digits. The middle finger and especially the ring finger have considerably limited independent extension. The motion restriction is because of the juncturae, which also prevents retraction of the proximal tendon end after distal transection of an extensor. Complete severance of an extensor proximal to the juncturae can be associated with normal MCP joint extension.⁷ This extension occurs through the juncturae connections. The extensor digitorum communis tendons can be evaluated by asking the patient to straighten out all of the fingers. The function of the extensor indicis proprius can be isolated from the common extensors by asking the patient to make a fist and then to point the index finger. The extensor digiti minimi is examined by having the patient straighten the little finger while the hand is closed into a fist.

The extensor mechanism of each digit is a complex interrelationship of muscle-tendon units of the long extrinsic extensor tendons and the intrinsic system (Fig. 50-15). The extensor expansion divides into a central slip that attaches to the middle phalanx and two lateral bands that join with the tendons of the lumbrical and interosseous muscles and attach to the base of each distal phalanx. The interossei and lumbrical muscles insert in the lateral aspects of the dorsal hood. Most of the power of the common extensors serves to extend the MCP joint. Distal digit extension is provided by continuation of the lateral band mechanism and the oblique retinacular ligament. Because of this complex anatomy, injuries involving the extensor mechanism require meticulous repair.

The sixth compartment contains the extensor carpi ulnaris. This tendon passes distal to the head of the ulna on the ulnar aspect of the wrist and inserts on the base of the little finger metacarpal. The extensor carpi ulnaris functions to extend and deviate the wrist ulnarly. This tendon is evaluated by having the patient extend and push the hand to the ulnar side against resistance; the tendon can be palpated distal to the ulnar styloid process.

Flexor Tendons.: The flexor tendons reside on the volar side of the forearm and cross the wrist joint volar to its axis. In general, 12 tendons function to flex the wrist and digits; three of them—the flexor carpi radialis, flexor carpi ulnaris, and palmaris longus—primarily flex the wrist and deviate the wrist radially or ulnarly (Fig. 50-16). The remaining tendons pass into the digits through the carpal tunnel. A single tendon, the flexor pollicis longus, inserts on the distal phalanx of the thumb, and two flexor tendons go to each remaining finger. The flexor digitorum superficialis (FDS) tendons bifurcate near the base of the proximal phalanges and surround the tendons of the FDP before inserting on the middle phalanges of the index, middle, ring, and little fingers (Fig. 50-17). The FDS flexes all the joints it crosses, including the wrist, PIP joints, and MCP joints. The profundus tendons lie deep to the superficialis tendons over most of their course in the forearm. At the level of the MCP joint, they perforate the superficialis tendon to emerge to a superficial position. They insert at the base of the distal phalanx and act primarily to flex the DIP joint and all joints flexed by the FDS. From the level of the MCP joint distally, the two flexor tendons become enclosed in a fibrous flexor sheath lined by synovium. Regions of thickening in this sheath form pulleys that help prevent bowstringing of the flexor tendons across the joint and assist smooth, effective flexion (Fig. 50-18).

After observation, each muscle-tendon unit is tested with a functional examination. The flexor carpi radialis, palmaris longus, and flexor carpi ulnaris are tested together by having the patient flex the wrist against resistance while the examiner palpates the individual tendons. The tendon of the flexor pollicis longus attaches to the base of the distal phalanx of the thumb and flexes the thumb MCP and IP joints. This tendon is tested by having the patient bend the tip of the thumb against resistance. FDP function can be tested by having the patient flex the distal phalanx of each finger while the PIP is stabilized in extension by the examiner (Fig. 50-19). The FDS is tested individually by asking the patient to flex the PIP joint while the other fingers are held in extension to block the flexion produced by the profundus tendons (Fig. 50-20). This is a subtle but important distinction, because lacerations of the digital creases can easily damage one or more of the tendons or adjacent neurovascular bundles. The FDP is more commonly lacerated in the finger because of its paradoxically superficial position.

If movement against resistance is intact but accompanied by pain or diminished strength, the involved tendon may be partially disrupted. Pathologic nodular swelling of one of the long flexor tendons may result in intermittent catching, or “triggering,” on a thickened flexor sheath anterior to the MCP joint. In this condition, known as trigger finger, a palpable and sometimes audible snapping can be appreciated when the patient is asked to flex and extend the fingers. On occasion, the patient may need to break the triggering effect by directly palpating the affected joint with the opposite hand.

Synovial Spaces.: Bursae are synovial sheaths that cover tendons as they pass through osseofibrous tunnels. They contain synovial fluid and serve two essential functions: They decrease friction during tendon movement, and they help supply nutrients to the relatively avascular tendons (Fig. 50-21). These sheaths also can provide pathways for spread of infection. Extensor tendons do not lie within definite sheaths and are afforded a greater resistance to infections. The synovial sheaths of the flexors in the index, middle, and ring fingers are enclosed from their insertion to approximately the level of the distal palmar crease. The sheath of the flexor pollicis longus extends from the tip of the thumb to the proximal volar wrist crease, where it communicates with the radial bursa in the palm and carpal tunnel. Similarly, the synovial sheath of the little finger communicates with the ulnar bursa. Clinical features of flexor tenosynovitis are caused by inflammation and distention of these synovial sheaths. Kanavel¹² described the classic signs: a semiflexed posture of the digit, pain on passive extension of the digit, fusiform swelling, and tenderness of the synovial sheath.

Arterial System.: The hands and the digits have a dual blood supply (Fig. 50-22). The major blood supply to the hand is from the radial and ulnar arteries. The radial artery lies on the anterior aspect of the radius in the distal part of the forearm. It continues around the lateral side of the wrist onto the dorsum of the hand by passing deep to the tendons of the abductor pollicis longus and the extensor pollicis brevis. On entering the palm, the radial artery terminates as the deep palmar arch. The ulnar artery enters the hand anterior to the flexor retinaculum on the radial side of the ulnar nerve and pisiform bone. The artery gives off a deep branch and then continues into the palm as the superficial palmar arch. This complex arterial arch system anastomoses and sends branches to the individual digits and the deep palmar spaces. Because of extensive collateralization, the hand usually survives even if both vessels are transected at the wrist.¹³ The circulation of the hand is evaluated by palpation of the radial and ulnar arteries on the volar aspect of the wrist, by assessment of the color and warmth of the skin, and by testing of capillary refill. Because “normal” findings vary among patients, the injured hand should be compared with the unaffected side.

Although Allen’s test is an imperfect predictor of vascular compromise, it is commonly used to determine the patency of the arteries supplying the hand and the contributions to the circulation of the hand derived from each of the major vessels. The radial and ulnar arteries are compressed by the examiner at the wrist (Fig. 50-23). The patient opens and closes the hand repeatedly to exsanguinate it and then maintains a relaxed position. The radial artery is released. If the palm and fingers fill immediately with blood, the radial artery is patent, with good collateral flow into the ulnar artery system. To evaluate the ulnar artery, the same steps are repeated, but the ulnar artery is released. This method also can be used on a single digit to help evaluate the patency of each digital artery to that finger. Unilateral digital artery injuries may be well tolerated owing to adequate collateral circulation from the uninjured side. Bilateral digital artery injuries, although rare, tend to have poor outcomes.^13,13a,13b

Venous and Lymphatic Systems.: The veins generally follow the arterial pattern in the deep system. The abundant dorsal, superficial veins are more extensive than the deep system and drain most of the blood from this region. The lymphatic vessels essentially follow the veins, with most lymph flowing into channels in the dorsal subcutaneous space. This vascular anatomy and the laxity of the dorsal skin account for palmar infections causing swelling on the dorsum rather than on the palmar surface of the hand.

Motor Innervation.: The radial nerve (formed from nerve roots C6 through C8) passes through the supinator muscle and enters the dorsal aspect of the wrist between the radial styloid and Lister’s tubercle. At this level, the nerve has a purely sensory function. Its important motor function is to innervate the dorsal extrinsic muscles in the forearm, which extend the wrist and MCP joints and abduct and extend the thumb. No intrinsic muscles in the hand are innervated by the radial nerve. Motor function in this nerve is tested by having the patient extend the wrist against resistance. Proximal injury to the radial nerve causes a condition known as wristdrop: The fingers are held in flexion at the MCP joints, and the thumb is adducted (Fig. 50-24A).

The ulnar nerve (C7, C8, and T1) passes through the flexor carpi ulnaris muscle in the forearm and lies ulnar to the artery and superficial to the flexor retinaculum. It enters the hand at the wrist through the ulnar tunnel, or Guyon’s canal. The ulnar nerve innervates the hypothenar muscles, the seven interosseous muscles, the lumbrical muscles to the ring and little fingers, and the adductor pollicis. Innervation of the flexor pollicis brevis is variable. In the forearm, the flexor carpi ulnaris and the ulnar half of the FDP also are innervated by the ulnar nerve. Loss of motor function of the ulnar nerve results in inability to pinch a piece of paper tightly between the thumb and the index finger. A late characteristic of distal ulnar damage is Duchenne’s sign, manifested by clawing of the ring and little fingers (see Fig. 50-24B). The ring and little fingers are hyperextended at the MCP joints by the extensor digitorum communis (radial nerve) and flexed at the IP joints by the FDP (intact proximal ulnar nerve). In addition, the interosseous and hypothenar muscles are atrophied.

The median nerve enters the forearm through the pronator teres muscle. At that level, it innervates that muscle, the flexor carpi radialis, the FDS, the radial part of the FDP, the flexor pollicis longus, and the pronator quadratus. The branch of the median nerve that innervates the last three muscles is called the anterior interosseous nerve. The median nerve enters the hand through the carpal tunnel accompanied by the nine extrinsic flexor tendons of the digits. The thenar motor branch (recurrent median nerve) innervates the abductor pollicis brevis, the opponens pollicis variably, and the flexor pollicis brevis. Common digital branches innervate the lumbrical muscles to the index and long fingers. Injury to this nerve occurs most commonly at the level of the wrist, by laceration or by compression in the carpal tunnel. Motor function is tested by having the patient appose the thumb to the index digit. Injury to the median nerve in the upper forearm or at the elbow usually results in weakness or absence of flexion of the index finger distal phalanx, the middle phalanx, and the thumb and weakness of thumb abduction and opposition. With passage of time, the muscles of the thenar eminence atrophy, leaving the hand with a flattened and “apelike” appearance (see Fig. 50-24C).

Sensory Innervation.: The typical distribution of the sensory nerves to the hand is shown in Figure 50-25. Because some overlap occurs between various sensory nerves, it is preferable to test sensation in the areas least likely to have dual innervation. The anatomic area of least ulnar variation and overlap is the volar tip of the little finger. The median nerve exclusively innervates the volar tip of the index finger. The dorsal first web space is entirely within the radial nerve distribution.

Several methods exist to assess sensation. Two-point discrimination is one such method, although both the accuracy and objectivity of this test have been called into question.¹⁴ An uninjured hand is able to distinguish two points that are 2 to 5 mm apart at the fingertips and 7 to 10 mm apart at the base of the palm. The dorsum of the hand is the least sensitive region, with a normal threshold at 7 to 12 mm. Two-point threshold distances wider than these ranges indicate impaired sensory function.¹⁴ The threshold and two-point discrimination tests may be of limited value in children, patients with heavily calloused fingertips, uncooperative patients, comatose patients, patients in severe pain, or suspected malingerers. In such patients, submerging the hand in water and observing the skin for the development of wrinkles has been offered as a way to diagnose nerve impairment because denervated skin will not wrinkle.¹⁵

Pathophysiology.: Fractures of the metacarpal head are rare. They usually occur as a result of direct trauma or crush injury and typically are comminuted.²¹ These fractures occur distal to the attachment of the collateral ligaments. Physical examination reveals tenderness and swelling over the involved MCP joint. Pain is increased if axial compression is applied along the extended digit. The presence of lacerations over the metacarpal heads is significant and suggests the possibility of an open fracture potentially caused by human bite injury.

Diagnostic Strategies: Radiology.: Although routine radiographic imaging of the injured hand reveals most fractures, the metacarpal heads can be difficult to assess because of overlap on the lateral view. In such cases in which clinical suspicion of a fracture exists and the initial radiographic appearance is normal, the Brewerton “ball-catcher’s” view may be helpful.²⁶ This view is obtained with the digits in 65 degrees of flexion at the MCP joints and the x-ray beam angled 15 degrees radially, projecting the metacarpal heads in profile. Occasionally, computed tomography also may be required to evaluate accurately the degree of displacement of intra-articular fractures at the MCP level.

Management.: Emergency management of closed metacarpal head fractures consists of elevation, ice for comfort, analgesics, and immobilization of the hand in the “safe” or functional position, which balances the forces of the intrinsic muscles. In this position, shown in Figure 50-36, the wrist is extended 20 degrees, the MCP joints are flexed to 90 degrees, and the PIP and the DIP joints are extended. Referral to a hand surgeon for management and follow-up evaluation is required in all cases. Because these are intra-articular fractures, displacement by more than 1 to 2 mm predisposes the patient to a poor result; however, little consensus has been reached regarding optimal definitive treatment.²⁷

Lacerations or puncture wounds over the dorsum of the MCP joint associated with a metacarpal head fracture should be considered open until proven otherwise. Such injuries often are caused by a clenched-fist injury and are highly contaminated wounds. Emergent consultation with a hand surgeon for operative débridement and irrigation is recommended. Prophylactic coverage with a cephalosporin is routinely recommended, although patients with highly contaminated wounds should receive penicillin with a β-lactamase inhibitor and an aminoglycoside.²⁸ Several studies have found preoperative wound cultures to be of no value in predicting the risk of infection or identifying the likely pathogen, and some clinicians have abandoned their use.^29,30

Complications.: Metacarpal head fractures may be associated with debilitating hand complications, including avascular necrosis, rotational malalignment, interosseous muscle fibrosis, extensor tendon injury or fibrosis, and chronic stiffness of the MCP joint. Many of these fractures also may require late arthroplasty.²¹

Pathophysiology.: Fractures of the metacarpal neck are among the most common fractures in the hand. The mechanism of injury is a direct impaction force (e.g., a punch with a closed fist). A boxer‘s fracture is a fracture of the neck of the little finger metacarpal (Fig. 50-37). Most metacarpal neck fractures have a typical apex dorsal angulation. They are inherently unstable because of the deforming muscle forces and frequent comminution of the volar cortex. Management generally is difficult because of this instability and the difficulty in maintaining reduction.

Management.: For treatment purposes, metacarpal neck fractures are divided into two groups: fractures involving the ring and little finger metacarpals and fractures involving the index and long finger metacarpals. There is considerably more mobility of the metacarpals of the ring and little fingers compared with the index and long fingers. This greater mobility makes them more prone to fracture, and the relative immobility of the index and long finger metacarpals increases the need for accurate alignment after reduction. In general, less than 15 degrees is allowed in the index and long finger metacarpals; in the ring and little finger metacarpals, 35 degrees and 45 degrees of angulation, respectively, are allowed. Any rotational malalignment should be completely corrected.

Nondisplaced ring and little finger metacarpal fractures without angulation deformity can be treated initially with ice, limb elevation, analgesia, and immobilization in a gutter splint. Nondisplaced, nonangulated metacarpal fractures of the index and long finger metacarpals are treated similarly. The splint should be in standard position of function and extend from below the elbow up to, but not including, the PIP joint. In general, it is recommended to begin PIP and DIP motion without delay. Protected MCP motion can begin in 3 to 4 weeks.²¹ For isolated fractures of the little finger metacarpal neck, some clinicians advocate immediate mobilization of fractures regardless of the degree of angulation. Results with this approach include excellent function, with only minor cosmetic deformity, and early return to work. Early follow-up evaluation is advised to exclude residual angulation, rotational deformity, and delayed displacement.³¹

Reduction of ring and little finger metacarpal neck fractures with significant angulation or deformity may be attempted in the ED. After appropriate anesthesia is obtained, usually with a hematoma block or an ulnar nerve block, traction is applied on the metacarpal to disimpact the fracture. The MCP joints and IP joints are flexed at 90 degrees, and simultaneous pressure is applied in a volar direction over the metacarpal shaft and in a dorsal direction over the flexed PIP joint (Fig. 50-38). This maneuver is termed the 90-90 method and should complete reduction. A gutter splint in position of function should be applied. Postreduction radiographs should be obtained immediately and after 1 week to ensure that reduction has not been lost. If closed reduction cannot be achieved or maintained, pin fixation by a hand surgeon is necessary, and early referral is indicated.

Displaced or angulated index or long finger metacarpal neck fractures commonly require anatomic reduction and surgical fixation. ED management consists of ice, limb elevation, and the application of a volar splint. Prompt referral to a hand surgeon is necessary.

Complications.: Metacarpal neck fractures may have an associated rotational component that can impair function and result in overlapping of the affected finger over an adjacent finger. If excessive angulation is not corrected, the patient may experience forced hyperextension of the MCP joint and flexion of the PIP joint when extending the finger and pain when tightly grasping objects. Other complications include extensor tendon injury and collateral ligament damage. Nonunion is rare after closed metacarpal fractures.

Pathophysiology.: There are three types of metacarpal shaft fractures: transverse, oblique or spiral, and comminuted. Transverse and comminuted fractures usually result from a direct blow and commonly exhibit dorsal angulation (Fig. 50-39). Indirect trauma or rotational torque applied to the finger may result in a spiral shaft fracture. These fracture fragments tend to shorten and rotate rather than angulate.

Management.: Metacarpal shaft fractures are treated differently than fractures involving the neck because rotational deformity and shortening are more likely and less angular deformity is acceptable. In general, any rotational deformity should be corrected. Angulation deformities are unacceptable in the index and long finger metacarpals, whereas a small amount of angulation may be compensated for in the ring and little finger metacarpals. Acceptable reduction is less than 10 degrees of angulation in the former and less than 20 degrees in the latter, with less than 3 mm of shortening and normal rotational alignment.²¹

Most metacarpal shaft fractures can be managed initially with ice, limb elevation, analgesia, and immobilization in a gutter splint. The splint should include the wrist and the entire metacarpal shaft, but not the MCP joint if the fracture is proximal to the neck. Repeat radiographic examination and referral to a hand surgeon are recommended. If manipulative reduction is necessary, operative fixation usually is indicated. Multiple displaced metacarpal shaft fractures, oblique or spiral fractures with rotational deformity, irreducible transverse fractures, and displaced open fractures require internal fixation.³¹

Clinical Features.: Fractures of the metacarpal base generally are stable and occur infrequently. They may result from either a direct blow over the base of the metacarpal or an axial force or torque applied along the digit. Examination reveals tenderness and swelling at the base of the involved metacarpal, and a significant degree of rotational deformity may be evident. Fractures at the base of the ring or little finger metacarpals may cause injury to the motor branch of the ulnar nerve, resulting in paralysis of the intrinsic hand muscles. In addition, they may be associated with a carpal bone fracture.

Management.: Initial management in the ED consists of ice, limb elevation, analgesia, and immobilization in a bulky compressive dressing or volar splint with referral to a hand surgeon for definitive management.

Complications.: Metacarpal base fractures may be associated with extensor or flexor tendon damage and significant rotational malalignment. Chronic CMC joint stiffness often is associated with intra-articular fractures and may necessitate arthrodesis or arthroplasty.

Extra-articular Fractures.: Extra-articular fractures are seen more commonly than intra-articular fractures and usually result from direct trauma or impaction. The three types of extra-articular fractures are transverse, oblique, and, in children, epiphyseal. Examination reveals localized pain and swelling over the fracture site.

Mobility of the thumb metacarpal allows 20 to 30 degrees of angular deformity without functional impairment. Patients with extra-articular fractures with a greater degree of angulation should undergo closed reduction, postreduction radiographic evaluation, and immobilization of the thumb in abduction with its IP joint extended with a thumb spica cast for 4 weeks. Transverse fractures usually are stable and can be managed with closed reduction and immobilization. If the fracture is oblique, it may require Kirschner wire fixation because of instability and a propensity for rotational deformity.²¹

Intra-articular Fractures:

Distal Interphalangeal Joint.: The DIP joint structure is analogous to that of the PIP joint. Additional stability is provided by the adjacent insertions of the flexor and extensor tendons, and dislocations are uncommon. Most dislocations are dorsal and usually are associated with an open wound (Fig. 50-42). The distal phalanx is said to be “bayonet-apposed”—the shafts of distal and middle phalanges lie adjacent to each other, but no bony contact occurs end-to-end at the articular surfaces. Routine radiographs are used more often to rule out associated fractures than to confirm a suspected diagnosis. Treatment consists of closed reduction performed under digital or wrist block anesthesia, followed by active and passive stability testing. Reduction usually is accomplished easily by longitudinal traction and hyperextension to distract the bayonet-apposed distal phalanx followed by direct application of dorsal pressure to the base of the distal phalanx. Irreducible fractures require surgery for open reduction. The irreducibility may be a result of interposition of an avulsed fracture fragment in the joint, entrapment of the profundus tendon, or buttonhole tear through the volar plate.⁴⁴

If the dislocation is open, the joint is contaminated, and treatment should include débridement and copious wound irrigation. The skin should be sutured and the joint splinted in slight flexion with a dorsal splint for 3 weeks. Most authorities recommend prophylactic antibiotics.⁴⁴

Proximal Interphalangeal Joint.: Dislocations of the PIP joint are the most common ligament injuries in the hand. Stability is derived from the strong conjoined attachments of the paired collateral ligaments and the volar plate. Three types of displacement of the PIP joint may occur: dorsal, lateral, and volar. The mechanism of injury usually is sports related, with a high-velocity blow to the end of the finger, which causes an axial load and hyperextension. Simple dorsal dislocations result when the volar plate ruptures and the middle phalanx assumes the position of bayonet apposition. Alternatively, a lateral dislocation may result from a radially or ulnarly directed force on the joint that leads to rupture of one collateral ligament and at least partial avulsion of the volar plate from the middle phalanx. In lateral dislocations, the ratio of radial-to-ulnar collateral ligament (UCL) rupture is 6 : 1, and the digit usually is ulnarly deviated. Volar dislocation of the PIP joint is rare. The most common mechanism of injury is a rotary longitudinal compression force on a semiflexed middle phalanx that results in unilateral disruption of a collateral ligament and partial avulsion of the volar plate. Physical examination reveals swelling and tenderness over the PIP joint and inability to extend the joint. Routine radiographs of the injured digit reveal the type of dislocation and any associated avulsion fractures.

Management.: Small bone fragments at attachment sites seen on radiographs are associated with avulsions of minor ligamentous attachment points and do not indicate the need for open repair. Avulsion fractures involving 33% or more of the articular surface usually are unstable and require surgery.⁴⁵

Most closed dorsal and lateral PIP dislocations are treated nonoperatively.⁴⁴ Reduction is facilitated by digital nerve block and usually can be accomplished by longitudinal traction and mild hyperextension followed by firm dorsal pressure on the proximal aspect of the middle phalanx. When reduction has been achieved, active motion is tested. Reduction is stable if no displacement occurs during active range of motion and passive stressing of the joint. More than 20 degrees of deformity and instability with lateral testing indicate a complete ligamentous injury.⁴⁶ If stability is maintained during active range of motion, treatment consists of 3 weeks of immobilization in 20 to 30 degrees of flexion, followed by active exercises. Although stiffness, pain, and swelling are likely to persist for months, the long-term prognosis is good, and subluxation usually does not recur unless the finger is hyperextended again.⁴⁴ If the dislocation is irreducible or there is evidence of complete ligamentous disruption with dislocation on active range of motion, operative repair is required.

The management of volar dislocations of the PIP joint is controversial. The dislocation has been described as irreducible and requiring open reduction; however, some authorities state that most volar dislocations can be reduced by a closed technique of applying gentle traction with MCP and PIP joints flexed.⁴⁴ A stable reduction with repair of the soft tissue structures and transarticular pinning in the fully extended position also has been recommended.⁴⁴

Pathophysiology.: MCP dislocations are considerably less common than dislocations of the PIP joint. The MCP joints of the fingers are resistant to ligamentous injury and dislocation because of their inherent ligamentous structure, their surrounding supporting structures, and their protected position at the base of the fingers. Like the DIP and PIP joints, each MCP joint has two collateral ligaments and a volar fibrocartilaginous plate; however, the MCP joints are condyloid joints and permit, in addition to flexion and extension, 30 degrees of lateral motion while the joint is extended. Because of the shape of this articulation, the joint is more stable in flexion when the collateral ligaments are stretched than when they are in extension. They are most vulnerable to injury from forces directed ulnarly and dorsally.

Isolated injury to the collateral ligaments and volar plate of the MCP joint is rare. These injuries usually occur with hyperextension stress applied to the MCP joint with the finger extended. The patient has ecchymosis and swelling of the joint. Examination reveals tenderness along the joint and varying degrees of instability. The radiographic appearance usually is normal on routine views, but some clinicians recommend a Brewerton view to show any evidence of avulsed bone fragments.⁴⁷ Treatment for most of these injuries consists of application of a gentle compression dressing with light plaster reinforcement and early orthopedic referral.

Dislocations of the MCP joints of the fingers are relatively rare injuries and usually are dorsal. The most common digit involved is the index finger, followed by the little finger. These dislocations result from hyperextension forces that rupture the proximal volar plate and are divided into simple and complex types. In the simple dislocation (subluxation), the joint appears to be hyperextended to 60 to 90 degrees, and the articular surfaces are in contact without interposed soft tissue. With complex (complete) dislocations, the MCP joint is in moderate hyperextension and angulated, the metacarpal head is prominent in the palm, and the distended palmar skin is dimpled. Complex dislocations have a less striking presentation but represent a more severe injury; the volar plate is interposed in the MCP joint space, and closed reduction is not possible (Fig. 50-43). Radiographic examination shows an obvious dislocation on the lateral view. Posteroanterior views reveal widening of the joint space in complex dislocations. In addition, sesamoid bones may be seen in the joint; this finding is pathognomonic for this injury (Fig. 50-44).

Management.: After appropriate anesthesia is obtained, simple dorsal dislocations should be reduced in a way that prevents entrapment of the volar plate in the joint. Reduction is accomplished by flexing the wrist to relax the flexor tendons and applying firm pressure over the dorsum of the proximal phalanx in a distal and volar direction. Excessive hyperextension or longitudinal traction should be avoided. The MCP joints should be splinted in flexion, and referral to a hand surgeon is necessary. Complex dorsal dislocations do not reduce with closed methods and require operative reduction. Volar dislocations are rare and generally require operative reduction.

Pathophysiology.: The CMC joints of the digit form the base of the transverse metacarpal arch of the hand. The metacarpal bases articulate with one another and with the distal carpal row in a complex interlocking structural arrangement. The joints are supported by strong dorsal, volar, and interosseous ligaments and are reinforced by the broad insertions of the wrist flexors and extensors (Fig. 50-45). Dislocations of the CMC joints are uncommon and often are missed.⁴⁸ Overall, the most commonly injured CMC joint is the little finger, and most of these injuries are dorsal fracture-dislocations.⁴⁹ The injury occurs as a result of motor vehicle collisions, falls, crushes, and closed-fist trauma.

Clinical Features and Diagnostic Strategies.: Clinically, the patient has swelling on the dorsum of the hand and tenderness over the involved CMC joints. Routine radiographs should be viewed carefully because fracture lines may be subtle, and the metacarpals may be obscured by superimposition. Other radiographic views that may be helpful include multiple oblique, forearm in 30-degree pronation, and Brewerton views.⁴⁹

Management.: Initial treatment consists of ice for comfort, limb elevation, and analgesia. Closed reduction of the dorsal fracture-dislocation may be attempted after adequate regional anesthesia has been obtained. Traction and flexion with simultaneous longitudinal pressure on the metacarpal base, followed by extension of the metacarpal head when length has been restored, generally result in reduction. Even in cases in which reduction is achieved by closed means, early referral to a hand surgeon is needed because Kirschner wire fixation is advisable to ensure adequate stability. The late sequelae of fracture-dislocations include pain and weakness from traumatic arthritis secondary to imprecise alignment or chronic dislocation of the CMC joints.

Management.: Closed reduction may be attempted after radial and median nerve wrist block anesthesia has been achieved. Pressure is directed distally on the base of the proximal phalanx, with the metacarpal flexed and adducted. If reduction is difficult, the IP joint and wrist can be flexed to relax the entrapped flexor pollicis longus tendon. When restoration of anatomic position has been accomplished, the collateral ligaments should be tested, and reduction should be confirmed by radiographic assessment. Stability to active range of motion and stress testing suggests that immobilization in a thumb spica splint with the MCP joint in 20 degrees of flexion for 4 weeks constitutes adequate treatment. Nonreducible (complex) dislocations or dislocations with significant lateral instability require open reduction and operative repair. Hyperextension, instability, and chronic pain on pinching may occur after these injuries.

Pathophysiology.: Injury to the UCL was first described as an occupational hazard of Scottish gamekeepers, who damaged their thumbs by a repeated maneuver involving twisting the necks of hares.⁵⁰ Skiing is now the most common cause of acute and chronic injury to the UCL.⁵¹ Skier‘s thumb is the most common upper extremity injury in skiing and results from interference with release of the pole at the moment of impact during a fall. UCL rupture occurs 10 times more often than radial collateral ligament injury.⁵² The mechanism of injury is forced radial deviation (abduction), and the subsequent tear usually occurs at the insertion into the proximal phalanx. Stener⁵³ showed that in nearly two thirds of cases of complete UCL rupture, the adductor pollicis becomes interposed between the superficial proximal portion and the deep distal portion of the ligament (see Fig. 50-45). Besides the collateral ligament injury, associated injuries of the dorsal capsule and volar plate are common.

Clinical Features.: Physical examination reveals swelling and localized tenderness over the ulnar border of the joint and weakness of pinch. Complete and partial ruptures usually can be differentiated by clinical examination. Valgus stress testing of the UCLs is required and should be performed with the joint in full extension and in 30 degrees of flexion to avoid the stabilizing effect of the volar plate. If the examination elicits pain and guarding, the test should be done after median and radial nerve block at the wrist or with use of local infiltration anesthesia. More than 35 degrees of joint laxity or 15 degrees of laxity beyond that present in the uninjured thumb is consistent with complete UCL rupture.⁵⁴ Routine radiographs should be obtained before the joint is stressed and may reveal a bony avulsion from the insertion of the UCL into the proximal phalanx or an associated condylar fracture. Radiographic findings of proximal phalanx volar subluxation and radial deviation may indicate complete UCL rupture.⁵⁵ Because of the difficulty in diagnosing complete rupture, it is commonly misdiagnosed as a simple sprain in the ED, potentially resulting in chronic disability.⁵⁶

Management.: Acute partial ruptures of the UCL can be treated effectively with a 4-week period of immobilization in a thumb spica cast; full recovery is the rule. Complete ligament tears require surgical repair because a high percentage are associated with soft tissue interposition from the adductor aponeurosis (Stener’s lesion), with limited predicted healing potential. Anatomic repair within 3 weeks of injury achieves good or excellent results in 90% of affected patients.⁵⁷ Long-term complications include chronic pain and instability with the loss of pinch strength, which may necessitate arthrodesis.

Zone I Injuries:

Zone II Injuries.: Zone II is the area over the middle phalanx. As the lateral bands blend dorsally to form the conjoint tendon, they are thin and oriented around the dorsal half of the middle phalanx. Injuries here usually are the result of a simple laceration, which seldom transects all of the dorsal apparatus. Examination reveals a typical mallet deformity. The treatment is identical to that for open zone I injuries.

Zone III Injuries:

Zone IV Injuries.: Zone IV includes the area over the proximal phalanx. The clinical findings are similar to those with zone III injury but are less severe because the PIP joint and lateral bands are intact. The resulting injury usually is partial, and the tendon ends usually do not retract appreciably. These injuries are treated with primary or delayed primary repair and appropriate splinting for 3 to 6 weeks. Simple injuries in this zone can be well approximated with 5-0 nonabsorbable sutures with buried knots. Immobilization should be done with maintenance of the wrist in extension and the MCP joints in approximately 15 degrees of flexion. Tendon adhesions are common in this zone because of associated damage to the periosteum.

Zone V Injuries.: Zone V injuries involve the areas over the MCP joint and should be presumed to be the result of a human bite until proven otherwise. These injuries occur most commonly over the MCP joints of the long and ring fingers. Radiographs are mandatory and may include Brewerton views to assess the metacarpal head closely for injury. The clinical findings with injuries to the extensor tendon at this level are flexion of the MCP joint and inability to extend the joint fully.

In an open joint injury caused by a human bite, the potential for mixed aerobic and anaerobic infections is high. Operative exploration, débridement, and irrigation are necessary. A combination of a β-lactam and a β-lactamase inhibitor drug is recommended empirically for infections related to human bites.²⁸ In penicillin-allergic patients, clindamycin in combination with a fluoroquinolone may be given.²⁸ The wound is left open and may be closed at 4 to 5 days if free from infection. The resultant tendon injury usually is only a partial laceration, which may be managed with primary or delayed primary repair.

For simple lacerations at this level caused by a sharp, clean object, primary repair is indicated. The involved tendon ends do not retract and can be approximated with 4-0 nonabsorbable sutures. Sagittal bands also should be repaired if injured to prevent loss of extension or subluxation. The wrist and MCP joints should be immobilized. Early referral to a hand surgeon is advised.

Zone VI Injuries.: Zone VI includes the area of the dorsum of the hand. Although these injuries may be similar in clinical appearance to zone V injuries, the joint is not involved, and these injuries generally are not as severe. Because the extensor tendons are superficial at this level, a relatively trivial-appearing skin laceration may be associated with one or more tendon lacerations. If the injury is proximal to the juncturae tendinum, the patient may be able to extend the involved MCP joint because weak extensor forces are transmitted to the junctura from adjacent extensor tendons.

The tendons in this area are round or oval and easily exposed. Primary repair with a modified Kessler stitch with a 4-0 nonabsorbable material or a figure-of-eight stitch with a buried knot on the deep, palmar surface of the tendon suffices. This repair is followed by immobilization of the wrist at 30 degrees of extension and the MCP joint in neutral position. Referral to a hand surgeon for delayed primary repair also is appropriate.

Zone VII and VIII Injuries.: Zone VII and VIII injuries involve the wrist and forearm. Management follows basic principles for tendon injuries.

Pathophysiology.: Flexor tendon injuries are not as common as injuries to the extensor complex and often have a subtle clinical presentation. The most common mechanism of injury is laceration, but closed traumatic disruption also may occur. FDP avulsion is the third most common tendon rupture in the hand in athletes.⁶¹ This injury usually is sports-related and involves a hyperextension force applied to an actively flexing digit; the classic example is that of an injured digit in a football player who grabs the clothing of an opponent who is breaking free from a tackle. Most of these injuries involve the ring finger, possibly because the ring finger becomes the most prominent finger with the fingers held in a partially flexed position.⁶⁶ Because of the closed nature of these injuries, the patient may not seek immediate care, or the condition initially may be misdiagnosed.

Clinical Features.: Careful assessment is necessary to diagnose flexor tendon disruption and associated neurovascular injury. With the normal hand at rest, there is a cascade of flexion of the digits, beginning with less flexion at the index finger and progressing to more flexion toward the little finger. An injury to a flexor tendon may be evident if the involved finger does not assume a naturally flexed position. Complete disruption of the profundus tendon results in an extended position of the DIP joint as a result of unopposed extensor forces. If the FDS is completely severed, or a partial tendon injury has occurred, the digit rests in less flexion than normal. An abnormal posture of the injured digit may suggest a flexor tendon injury; this usually is confirmed by a functional examination. The FDP and the FDS should be tested separately as previously described. This examination requires careful observation: The patient may flex the distal tip with an intact profundus, but an injury to the FDS precludes flexion at the PIP joint. Disruption of the FDP tendon leads to loss of flexion at the DIP joint, instability in pinch, and loss of grip strength. FDP avulsions can be classified into three types. Type I injuries involve retraction of the avulsed FDP tendon into the palm, damaging the blood supply to the tendon and causing hematoma formation in the process. Because of the damaged vasculature, these injuries should be repaired urgently to prevent ischemic tendon damage.⁶⁷ Types II and III injuries cause lesser degrees of retraction of the FDP tendon. Accordingly, these injuries result in less compromise of the tendon’s blood supply and have more favorable outcomes.⁶⁷ FDP injuries may be present if the patient complains of subjective weakness or if an abnormal position of the hand is observed at rest. Clinically, injuries are associated with pain and weakness with flexion against resistance. Despite these findings, it may not be possible to arrive at a complete and accurate diagnosis until the wound is surgically explored. The palmaris longus, which is not present in approximately 15% of people, is not a functionally significant wrist flexor. Palmaris longus lacerations have tremendous diagnostic significance, however, because most of these injuries (80 to 90%) are associated with concomitant partial or complete median nerve lacerations. For this reason, all patients with palmaris longus lacerations should be assumed to have median nerve laceration until such injury has been ruled out clinically or by direct examination.⁶⁸

Management.: Flexor tendon repairs require the expertise of a hand surgeon and generally are not repaired by emergency physicians. Immediate or delayed primary repair is now advocated for most acute flexor tendon injuries, including avulsions of the FDP and injuries involving the so-called “no man’s land,” which extends from the distal palmar crease to the midportion of the middle phalanx. The term “no man’s land” refers to the high frequency of tendon adhesion after injury in this area. The advantages of primary repair with surgical reapproximation over secondary grafting for treatment of acute injuries have been well described in the literature.⁶⁹ Emergent repair of lacerated flexor tendons is indicated in the setting of diminished circulation to the digit requiring vascular repair. Otherwise, early definitive repair can be undertaken within days of the injury.⁶⁹ Secondary repair of flexor tendons may be performed 4 weeks after injury, but repair is considered late after that. In general, the results of primary, delayed primary, and early secondary repair are approximately equal. Treatment of partial flexor tendon lacerations is controversial, but referral to a hand surgeon for further exploration and possible repair is prudent.

If a hand surgeon is not immediately available, open wounds should be copiously irrigated and closed with 5-0 nylon and the hand splinted with the wrist in 30 degrees of flexion—the MCP joints flexed approximately 70 degrees and the IP joint flexed 10 to 15 degrees. This flexion ensures that no further damage occurs to the tendon and that the tendon will not contract further on movement. The patient also should receive tetanus immunization as indicated, and most authorities recommend empirical use of broad-spectrum antibiotics. Most closed tendon injuries require referral to a hand surgeon because of the risk of long-term disability.

Complications.: With optimal management, most patients with flexor tendon injuries have good to excellent outcomes.⁷⁰ With injuries involving the no man’s land, results may be poor, and tendon grafting occasionally is required. Overall, adhesions remain the most significant problem after operative repair. Other complications include triggering, bowstringing, and intratendinous epidermoid cyst formation.⁷¹

Classification.: Fingertip amputations are the most common type of amputation of the upper extremity. In zone I injuries (Fig. 50-53), the proximal two thirds of the nail bed is preserved. In zone II injuries, bone is exposed, and in zone III injuries, the entire nail bed is lost. Radiographic studies are indicated if bony avulsion injury or fracture cannot be excluded. Most of these fingertip injuries can be managed on an outpatient basis.

Management.: Treatment of distal fingertip injuries is controversial; consequently, management should be individualized, and few guidelines are available. In general, most hand surgeons try to maintain length of the thumb by whatever means possible.⁷⁷ The index finger is considered next before the other fingers. An intact pulp-to-pulp pinch mechanism is the principal goal. Other factors to consider include the patient’s age, health, occupation, and handedness.

In most fingertip amputations distal to the DIP joint, adequate care can be provided with conservative wound management. The simplest and often best method for managing a fingertip amputation is allowing the wound to heal by secondary intention. This method generally is effective and produces good results if the wound is less than 1 cm. Large dorsal wounds also heal well by this method. It is the treatment of choice in childhood fingertip amputations, particularly when no bone is exposed. In cases in which a small protuberance of phalangeal bone (extending no more than 0.5 cm) is exposed, it may be trimmed back with a rongeur to just below skin level and the wound allowed to heal by secondary intention; if the bone is left exposed without soft tissue coverage, the patient will need an operative procedure. In most cases the wound heals through a process of granulation, wound contracture, and reepithelialization within a few weeks. Initial management should include careful and meticulous wound cleansing, a nonadherent dressing, appropriate tetanus prophylaxis, and splinting to protect the tip. Amputations that involve the distal phalanx usually are treated as contaminated open fractures with an initial intravenous dose of a cephalosporin followed by an oral course. Patients should have appropriate follow-up care to ensure adequate healing and recovery.

Management of fingertip injuries involving significant soft tissue (especially volar) or bone loss usually requires the expertise of a hand surgeon. Surgical management may include primary closure, full-thickness or partial-thickness skin grafts, composite grafts, adjacent flaps, regional flaps from the hand, distant flaps, and reimplantation. With most of these operative techniques, repair is best performed as a primary procedure under ideal circumstances or as a delayed procedure when necessary. A flap may be used to cover exposed bone or soft tissue avulsion and to add bulk to the tip. The nail bed tissues should be preserved because the presence of a nail affects the cosmetic result. At least 5 mm of healthy nail bed distal to the lunula is needed for nail adherence. Skin grafting is a common method for treating fingertip amputations with significant avulsed tissue and can provide a functional and an esthetic reconstruction.

Complications.: These injuries commonly leave the patient with a painful, cold-intolerant fingertip; this complication has been described after primary closure, coverage with grafts or flaps, and healing by secondary intention. Skin grafting may result in induration, fissuring, and diminished sensibility. Nail deformity is common, particularly with considerable volar loss of tissue.⁷⁸

Subungual Hematoma.: Subungual hematomas result from crush injury or blunt trauma to the nail bed with bleeding from the rich vascular bed. The nail bed is predisposed to injury because it is interposed between the firm nail and the distal phalanx. The injury is manifested by pain and dark red to black discoloration of the nail bed and is classified by the percentage of area beneath the nail that is involved. When the fingertip is unstable or the mechanism of injury suggests a significant distal phalanx fracture, a radiograph should be obtained to identify associated fracture.

Nail Bed Lacerations.: Lacerations of the nail bed should be repaired to minimize esthetic deformity and the duration of functional impairment. These injuries generally do well after primary repair, but late reconstruction of the nail bed is unpredictable, and usually little improvement is obtained.

Simple and crushing lacerations should be repaired accurately with 5-0 or 6-0 absorbable suture, ideally under loupe magnification. The results with both injuries should be satisfactory in the majority of cases.⁷⁹ After the nail bed is accurately approximated, a hole is burned through the nail to allow drainage of blood from the subungual area after the nail is reinserted into the nail fold. The avulsed nail may be sutured in place or secured with tape. A single thickness of nail-shaped Adaptic or other nonadherent gauze may be placed in the nail fold if the nail is unavailable. The replaced nail or gauze is used as a temporary splint to help protect the integrity of the underlying nail bed and maintain the fold for new nail growth and to help prevent synechiae and subsequent nail deformity. Complete nail growth takes 70 to 160 days, but after the injury the growth pattern often is changed.

Nail bed avulsion commonly leaves fragments of nail bed attached to the undersurface of the avulsed nail.⁸⁴ In these cases it is advisable to replace the nail as accurately as possible onto the avulsion site. Repair should be done with mattress sutures without attempting to separate the nail from the nail bed. If the tissue is not available and the defect is small, effective healing occurs by secondary intention.

Pathophysiology.: A paronychia is a localized superficial infection or abscess involving the lateral nail fold. It is the most common infection in the hand and is thought to be caused by frequent trauma to the delicate skin around the fingernail and cuticle. Clinically, swelling and tenderness of the soft tissue along one or both sides of the lateral nail fold are evident. A paronychia begins as a cellulitis, but a frank abscess may form, and occasional extension to the overlying proximal nail (termed an eponychia) may be seen. S. aureus is the most common isolate, followed by streptococci.⁹⁸ Paronychias in children often are caused by anaerobes, presumably because of finger sucking and nail biting common in this age group.⁹⁹ Atypical mycobacteria, Candida albicans, and other fungi should be considered as causative agents in chronic cases unresponsive to standard treatment.¹⁰⁰

Management.: In the early cellulitis phase, management consists of frequent warm soaks, elevation of the affected limb, and administration of an oral antistaphylococcal antibiotic, such as dicloxacillin or cephalexin. When the area becomes fluctuant, drainage is necessary and usually is curative. Adequate drainage often can be obtained by lifting the skin edge off the nail to allow the pus to drain (Fig. 50-55). This can be accomplished without anesthesia in selected patients, but drainage for more extensive lesions is best carried out under digital block anesthesia. After the eponychium has been softened by soaking, a No. 11 blade scalpel or an 18-gauge needle may be advanced parallel to the nail and under the eponychium at the site of maximal swelling.⁹⁸ If the infection is more extensive, the lateral one fourth of the nail may be bluntly dissected from the underlying nail bed and germinal matrix, and the lateral nail plate excised. After the cavity is irrigated, a small piece of packing gauze may be slipped under the eponychium for 24 hours to provide continual drainage. Cultures are not indicated. Antibiotics are commonly prescribed, although this is not necessary if drainage is complete or if the surrounding area of cellulitis is minimal. Most paronychias resolve in 5 to 10 days, and patients are advised to obtain primary care follow-up evaluation. A well-known complication of even a properly drained paronychia is osteomyelitis of the distal phalanx. Patients with a chronic, indolent infection of the perionychium seldom respond to ED intervention. These patients should be referred to a dermatologist or hand surgeon because of the prolonged treatment required.

Pathophysiology.: A felon is an infection of the pulp of the distal finger or thumb. It differs from other types of subcutaneous abscesses because of the presence of multiple vertical septa that divide the pulp into small fascial compartments. The usual cause is penetrating trauma with secondary bacterial invasion. The most common pathogen is S. aureus, although gram-negative organisms and polymicrobial infections also have been described.¹⁰⁰ Although the septa may facilitate an infection in the pulp and inhibit drainage after incomplete surgical decompression, they provide a barrier that protects the joint space and the tendon sheath by limiting the proximal spread of infection. Clinically, a felon begins as an area of cellulitis and inflammation that progresses rapidly to severe throbbing, pain, swelling, and increased pressure in the distal pulp space.

Management.: Traditional management of felons emphasizes the need for early and complete incision through the septa to provide adequate drainage and to relieve pressure in septal compartments. Most felons can be drained by a single lateral incision.¹⁰⁰ The incision should be made along the ulnar aspect of the index, middle, and ring fingers and the radial aspects of the thumb and little finger, avoiding pincher surfaces. The incision is begun approximately 0.5 cm distal to the DIP joint crease and dorsal to the neurovascular bundle of the fingertip. The incision is extended to the free edge of the nail (Fig. 50-56). The wound should be irrigated and loosely packed with gauze, and the affected finger splinted. The packing is removed in 48 to 72 hours, and the wound is left to close secondarily. Most felons are treated empirically with an antistaphylococcal oral antibiotic for at least 5 days pending culture results. Some authorities recommend draining this abscess where it “points,” with use of a volar midline incision that does not cross the distal flexion crease.¹⁰¹

Complications.: If untreated, the expanding abscess can extend toward the phalanx, producing an osteitis or osteomyelitis, or toward the skin, resulting in necrosis and formation of a sinus tract on the palmar surface of the digital pulp. Other complications include soft tissue and bony tuft necrosis, osteomyelitis, septic arthritis of the DIP joint, and flexor tenosynovitis from proximal extension. The lateral incision used to drain felons commonly leaves unstable finger pads or may result in painful neuromas or anesthetic fingertips. “Fishmouth” incisions may destroy the blood supply to the fingertip.¹⁰⁰ Longitudinal midline incisions on the volar surface may leave scars over an important area for sensation but do not have the other disadvantages of lateral incisions. Any incision that is made too deeply and proximally can injure the flexor tendon sheath, initiating a tenosynovitis.

Epidemiology and Pathophysiology.: Herpetic whitlow is a self-limited herpes simplex viral infection of the distal finger. It is the most common viral infection of the hand. Infection by human herpes simplex virus type 1 or 2 is clinically indistinguishable.¹⁰² Direct inoculation of the virus into an open wound or broken skin is the usual mechanism of primary infection. Herpetic whitlow commonly is reported in adult women with genital herpes and children with coexistent herpetic gingivostomatitis. Health care workers are at increased risk for development of this infection as an occupational hazard secondary to exposure to orotracheal secretions; however, a review of herpes infection in the hand found that only 14% of adult cases occur in health care workers.¹⁰³ The overall incidence has decreased, probably as a result of heightened awareness of the condition and strict infection control precautions.

Clinical Features.: The infection usually involves a single finger and begins with localized pain, pruritus, and swelling, followed by the appearance of clear vesicles. Systemic symptoms usually are absent; however, secondary infection of the vesicles can occur.¹⁰² More typically, the vesicles coalesce over 2 weeks to form an ulcer, which may develop a hemorrhagic base. At this stage, it may be difficult to distinguish herpes simplex infection of the hand from more common bacterial infections, such as felon or paronychia. The distinction is important because drainage of the herpetic lesions is contraindicated and may lead to viral dissemination and secondary bacterial infection. A careful history is important to determine risk of a possible herpetic cause. On examination, tenderness is present but is noticeably less than that typical for bacterial infections. In addition, the pulp space remains soft and does not become tense, as it does in a bacterial felon.¹⁰⁴

Diagnostic Strategies.: The diagnosis usually is made clinically on the basis of the appearance of the lesion and the history of recurrence or potential sources of inoculation. The diagnosis may be confirmed by polymerase chain reaction (PCR), viral culture, or a Tzanck smear showing multinucleated giant cells in a scraping taken from the base of an unroofed vesicle.102,105

Management.: Herpetic whitlow usually resolves spontaneously in 3 to 4 weeks, although recurrence is common, occurring in up to 20% of cases. The main goals of treatment are to prevent oral inoculation or transmission of the infection and to provide symptomatic relief. The involved digit should be kept covered with a dry dressing. Oral acyclovir has a role in treatment for immunocompromised patients and patients with frequently recurring infections, but its role in immunocompetent patients is less clear.¹⁰⁵ Topical acyclovir has not been shown to be effective in either the treatment of or the prophylaxis for this disorder.

Pathophysiology.: Acute synovial space infections in the hand usually involve the flexor tendon sheaths and the radial and ulnar bursae. The tendon sheaths are double-walled, with a visceral layer adherent to the tendon and a parietal layer extending from the midpalmar crease to just proximal to the DIP joint. The flexor tendon sheath of the thumb is continuous with the radial bursa of the palm, and the small finger sheath is continuous with the ulnar palmar bursae. The ulnar bursa surrounds the superficial and deep flexor tendons, and the radial bursa surrounds the flexor pollicis longus. These two bursae communicate in 80% of persons; in most instances, however, the tenosynovial coverings of the index, middle, and ring fingers do not communicate. Infections in the synovial spaces in the hand tend to spread along the course of the flexor tendon sheaths and may spread to the midpalmar, thenar, and lumbrical compartments. Infections usually are caused by penetrating trauma to the sheath, but they occasionally result from hematogenous spread. The most commonly isolated organisms are S. aureus and streptococci, followed by gram-negative organisms and enterococci.¹⁰⁶

Clinical Features.: Four cardinal signs of acute flexor tenosynovitis usually are present and help differentiate tenosynovitis from other soft tissue infections in the hand: (1) tenderness along the course of the flexor tendon, (2) symmetrical swelling of the finger, (3) pain on passive extension, and (4) a flexed posture of the finger.⁶⁰ All four signs may not be present early in the course of infection. The third sign may be the most important. Early recognition and treatment are essential because elevated pressure within the enclosure of the flexor tendon sheath can occlude the already tenuous circulation to the tendon, resulting in necrosis and proximal spread.

Management.: All patients with flexor tenosynovitis require hospital admission and prompt consultation with a hand surgeon to determine whether open drainage or closed tendon sheath irrigation is indicated. In early cases or uncertain diagnoses, the hand should be splinted in a bulky dressing and elevated, and intravenous antibiotics should be initiated. Infections secondary to penetrating trauma should be treated with a penicillinase-resistant antistaphylococcal penicillin or first-generation cephalosporin. Disseminated gonorrhea should be considered in all sexually active persons, especially if a traumatic cause for the infection is not apparent. In such cases, some authorities recommend empirical treatment with ceftriaxone until results of final cultures (including mucosal sites) are available.106,107 Surgical treatment is indicated for established cases or when improvement is not evident within 24 hours.

Anatomy and Pathophysiology.: The deep fascial or palmar spaces of the hand include the midpalmar space, the hypothenar space, and the thenar space. Three additional, more superficial spaces of the hand are the dorsal subcutaneous space, the dorsal subaponeurotic space, and the interdigital web space¹⁰⁸ (Fig. 50-57). Although anatomically distinct from the deep spaces owing to their lack of well-defined anatomic borders, superficial spaces can harbor infections that manifest similarly to deep space infections.¹⁰⁸ The fascial spaces are potential rather than actual spaces in a normal hand.¹⁰⁹ These closed compartments are susceptible to infection from direct penetrating trauma, infection in contiguous compartments, or hematogenous seeding. The most commonly isolated pathogens are S. aureus, streptococci, and coliforms.

Clinical Features.: The unique anatomic features of the deep fascial spaces lead to characteristic clinical findings when these regions are involved with pyogenic infection. The dorsal subaponeurotic abscess causes swelling and erythema on the dorsum of the hand. Pain with passive movement of the extensor tendons often is present, but it may be difficult to distinguish clinically from simple cellulitis on the dorsum of the hand. Subfascial web space infections commonly result when palmar blisters become secondarily infected. The infection tends to spread dorsally into the interdigital space and produce a characteristic hourglass configuration, or the so-called “collar-button abscess” (Fig. 50-58). Thenar space infections are characterized by pain and swelling of the thenar eminence and the first web space; the thumb is held in abducted and flexed position.¹⁰⁹ In midpalmar infections, clinical features include loss of the normal hand concavity and tenderness of the central palm; movement of the middle and ring fingers is painful. Suppurative tenosynovitis of the second digit can rupture proximally into the thenar space, with subsequent abscess formation. Tenosynovitis of digits III, IV, and V may be responsible for a midpalmar space infection.

Management.: Treatment of all deep fascial space infections involves intravenous antibiotics and operative exploration and drainage by experienced surgeons. The most common practice is to use broad-spectrum empirical coverage with a β-lactamase–resistant penicillin or a first-generation cephalosporin. Based on local bacteriologic data, it may be necessary to begin empirical coverage against methicillin-resistant S. aureus (MRSA).¹¹⁰

Pathophysiology.: Septic arthritis in the hand may involve the IP, MCP, CMC, or radiocarpal joints. These joints usually are infected by direct inoculation of bacteria from penetrating trauma or by spread from a contiguous infective process, such as a felon or tenosynovitis. Hematogenous spread may occur but is less common than in other joints of the body. S. aureus is the most common cause; streptococci, Haemophilus influenzae, Pseudomonas aeruginosa, and coliforms are involved much less commonly.¹¹¹ A survey at a large county hospital found that the most commonly isolated organisms were staphylococci and streptococci in nearly equal numbers, with enterococci, corynebacteria, and anaerobes encountered rarely.¹¹² Monarticular nontraumatic septic arthritis also may be caused by Neisseria gonorrhoeae.

Clinical Features.: Clinically the involved joint appears red and swollen and is extremely tender; an overlying puncture wound may be visible. The joint is held in a position that maximizes its volume (slight flexion for MCP and IP joints), and passive motion of the joint, however slight, is painful. In contrast with flexor tenosynovitis, tenderness is localized to the involved joint.¹⁰⁸ Pain also may be elicited by axial compression of the joint. The diagnosis is made by arthrocentesis.

Management.: Treatment includes parenteral antibiotics with a semisynthetic antistaphylococcal penicillin and emergent drainage of the joint. Most infected joints require open drainage, but some hand surgeons may choose to manage certain cases with closed joint catheter irrigation and repeated aspiration.