Extensor and Flexor Tendon Injuries in the Hand, Wrist, and Foot

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Chapter 48

Extensor and Flexor Tendon Injuries in the Hand, Wrist, and Foot

Extensor Tendons

Extensor tendons are quite superficial, covered only by skin and a thin layer of fascia, and are thus highly susceptible to injury by commonly experienced trauma. Such injuries may result from lacerations, bites, or burns, but they may also be caused by closed injury with even seemingly superficial lacerations. Whereas some extensor tendon injuries must be managed by a hand surgeon, others may be treated in the emergency department (ED). The emergency clinician must understand the anatomy, principles of treatment, repair technique, and postrepair care of these injuries to ensure the best possible patient outcome.

Functional Anatomy

There are 12 extrinsic extensors of the wrist and digits, all of which are innervated by the radial nerve. The muscles that give rise to these tendons originate in the forearm and elbow (Fig. 48-1). The extrinsic extensor tendons reach the hand and digits by passing through a fibroosseous tendon sheath (retinaculum) located at the dorsal surface of the wrist. This synovium-lined sheath provides smooth gliding of the tendons and prevents bowstringing when the wrist is extended.1 The dorsal retinaculum contains six compartments or subdivisions (Fig. 48-2). These compartments are numbered from the radial to the ulnar side of the wrist.

The first compartment contains two tendons, the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB). The APL tendon is the most radial of the extensor tendons and inserts on the base of the first metacarpal. It can be palpated just distal to the radial tubercle. The APL tendon causes thumb abduction and extension and some radial wrist deviation. The EPB travels with the APL through the first compartment but inserts at the base of the proximal phalanx of the thumb. The EPB tendon can be palpated over the dorsum of the first metacarpal when the thumb is extended against resistance. Both tendons can be tested by having the patient spread the fingers apart against resistance.

The second compartment also contains two tendons: the extensor carpi radialis brevis (ECRB) and the extensor carpi radialis longus (ECRL). These two tendons arise from the lateral epicondyle of the elbow. The ECRL inserts on the base of the second metacarpal, and the ECRB inserts on the base of the third metacarpal. Both tendons are powerful wrist extensors, and the ECRL also allows some radial wrist deviation. Wrist extension plays an especially important role in the mechanics of the hand because hand grip strength is maximal only when the wrist is extended.

The third compartment contains only one extensor tendon, the extensor pollicis longus (EPL). This tendon crosses over the ECRB and ECRL and travels along the dorsum of the thumb to insert on the distal phalanx. The EPL forms the top of the anatomic “snuffbox,” and the bottom is formed by the EPB. The EPL can be visualized when the thumb is extended, and its strength can be tested by having the patient hyperextend at the interphalangeal (IP) joint against resistance. The intrinsic extensor of the thumb can provide some degree of extension at the IP joint. Therefore, if an EPL injury is suspected, it is important to compare extension at the IP joint with that of the unaffected thumb.

The fourth and fifth compartments contain the six tendons that extend the index through the little fingers. Each finger has its own extensor digitorum communis (EDC) tendon. The index and little fingers have an additional independent extensor tendon—the extensor indicis proprius (EIP) for the index finger and the extensor digiti minimi (EDM) for the little finger. The fourth compartment contains the EIP and EDC tendons, and the fifth compartment contains only the EDM tendon. These six tendons can be seen over the dorsum of the hand, where they are poorly protected and prone to injury. In this region the tendinous, ligamentous, and fascial connections between these tendons are known as the juncturae tendinum. Because of these interconnections, a patient may be able to extend a digit, albeit weakly, even when there is a complete laceration of its EDC tendon. To avoid missing a tendon injury on the dorsum of the hand, it is important that the examiner test for tendon strength and not just for active extension.

The course of the extensor tendons along the fingers is more complex, but a basic understanding of this anatomy is essential for the emergency clinician to evaluate and treat extensor tendon injuries (Fig. 48-3). The EIP tendon joins the EDC tendon at the level of the metacarpophalangeal (MCP) joint in the index finger. The EDM tendon parallels the course of the EDC tendon; the four EDC tendons eventually insert at the base of the proximal, middle, and distal phalanges. The most proximal insertion of the EDC tendon is at the level of the base of the proximal phalanx. The tendon actually inserts in two ways. First, there is a loose dorsal insertion just distal to the MCP joint. In addition, the EDC tendon inserts into the volar plate via the sagittal bands. The sagittal bands are circumferential structures at the level of the metacarpal head that serve to keep the EDC tendon centered over the metacarpal head, as well as to provide a stable connection with the volar plate located on the palmar side of the hand. After its primary insertion at the level of the MCP joint, the EDC tendon then extends dorsally along the digit. The EDC trifurcates over the proximal phalanx (Fig. 48-4). Its major central slip inserts on the base of the middle phalanx (Fig. 48-5). The lateral branches of the EDC tendon join with the lateral bands from the interossei and lumbricals to form the conjoined lateral bands. The two conjoined lateral bands then fuse together over the middle phalanx to form the terminal extensor mechanism (TEM), which inserts into the base of the distal phalanx (Fig. 48-6). The triangular ligament is a connection between the two conjoined lateral bands that assists in keeping these structures on the dorsal aspect of the digit.

The sixth dorsal compartment of the wrist contains only one tendon, the extensor carpi ulnaris (ECU). This tendon originates at the lateral epicondyle of the elbow and inserts at the base of the fifth metacarpal. The ECU functions as a wrist extensor and ulnar deviator. It can be palpated just distal to the tip of the ulna, and its strength can be tested by forced ulnar deviation of the wrist.

General Approach to Extensor Tendon Injuries

The key to detecting extensor tendon injuries in the ED is to perform a careful and thorough history and physical examination. Closed injuries may appear innocuous at first but can result in tendon injuries that may lead to severe deformities or dysfunction if undetected (Figs. 48-7 to 48-9). Closed injuries are also commonly associated with fractures. A hand radiograph is recommended for closed-hand injuries when a fracture is suspected or for open-hand injuries in which a fracture or foreign body is suspected. It is generally accepted that all open injuries that result from glass should be radiographed. Plain radiographs have a sensitivity of approximately 98% for detecting radiopaque foreign bodies (e.g., gravel, glass, metal).2

Injuries to extensor tendons from lacerations are quite common, especially on the dorsum of the hand, where they are located superficially. All dorsal wrist, hand, and digit lacerations should be assumed to have an underlying tendon laceration until proved otherwise. Digital extension, albeit weak, can still occur with partial tendon lacerations of up to 90%, so visualization of the tendon and careful strength testing are required to definitively rule out a partial injury. In some cases the specific diagnosis simply cannot be made on the first examination (see later). Complete laceration of an EDC tendon on the dorsum of a hand can also still allow digital extension through the juncturae tendinum.

After assessing the strength and neurovascular status of the injured hand it is imperative that the emergency clinician visually inspect the wound thoroughly. Inspection should include an assessment of the degree of wound contamination, as well as a search for foreign bodies and occult tendon lacerations. It is often necessary to extend the skin laceration to aid in the visualization of a possible tendon injury. Some investigators have advocated for the use of ultrasound in the diagnosis of suspected extensor (and flexor) tendon lacerations in the hand.3 This is a potentially attractive tool since it is easy to use and noninvasive and provides point-of-care analysis, but the use of sonography for detection of hand and digit tendon injuries cannot yet be advocated for routine use by emergency physicians. Because an extensor tendon is a mobile structure, it is imperative that if it is exposed, it be visualized in its entirety through a full range of motion. It is especially important to examine the tendon in the position that it occupied at the time of injury because the tendon injury frequently does not lie directly under the external skin wound (see Fig. 48-8).

Definitive examination of any wound must occur under the best possible conditions—with a good light source, a bloodless field, adequate local anesthesia, and a cooperative patient. It may be impossible to adequately assess some patients completely during the first ED visit. In this case, final diagnosis must be delayed until the proper circumstances permit the required conditions. Occasionally, patient noncompliance thwarts even the most carefully planned follow-up. Frequently, the patient’s pain, swelling, anxiety, or degree of intoxication or altered sensorium limits the clinician’s diagnostic ability; therefore, it would not be considered standard to diagnose the presence or the full extent of all extensor tendon injuries immediately. Whenever logistically possible, consult a specialist when an extensor tendon injury is suspected by mechanism, location of the wound, or tendon dysfunction. Under most circumstances, however, there is no value in obtaining an immediate on-site consultation with a hand or orthopedic surgeon because the intrinsic scenario would similarly limit any clinician’s diagnostic acumen.

If the examining clinician suspects but is unable to locate a tendon laceration or if a patient is uncooperative with the examination and the circumstances prohibit ideal initial care, refer the patient for follow-up in 1 to 3 days for a repeated examination. Close the skin and apply a splint for interim wound care. A delay of a few days for definitive diagnosis, surgical repair, or both does not result in any significant alteration in the final outcome. Delayed primary repair, without the need for tendon grafting or tendon transfer, is a well-accepted technique. In fact, many hand surgeons are reluctant to immediately repair even a complete extensor tendon laceration in a contused, potentially contaminated wound. The exact time frame under which such delayed repair results in an outcome similar to that of immediate repair is not well defined and depends on the clinical scenario. Usually, repair delayed for up to 7 to 10 days will still ensure an outcome similar to that of an immediate repair, but this varies depending on the injury. Clearly document the inability to rule out a tendon injury in the ED and the mandate for follow-up within a specified time frame on the medical record and discharge instructions.

Use of Antibiotics

There are no data to support or refute the use of prophylactic antibiotics as a routine adjunct after tendon injury. In general, prophylactic antibiotics have not been demonstrated to reduce infection rates after soft tissue injury in the setting of proper wound cleaning. Nor have they been proved to reduce infection rates in the absence of gross contamination, retained foreign material, extensive contusion, or a delay in cleaning. Many clinicians opt for antibiotics with gram-positive (including antistaphylococcal) coverage if the tendon has been injured or sutured, but no universally accepted standard of care exists. An individualized approach is advocated. Prophylaxis is generally used for only 3 to 5 days after injury unless there are extenuating circumstances (such as lack of immunocompetency, a human bite, an unusual source of contamination, or peripheral vascular disease). If the sterility of a wound is in doubt, do not attempt tendon repair.

Preparation for Repair

Before attempting repair of an open extensor tendon injury in the ED, be prepared and have the proper equipment available. Place the patient supine on a gurney that ideally has an arm board attached. Bright overhead lighting is important for wound exploration so that the presence of tendon injuries and foreign bodies can be adequately assessed. Instruments should include, at a minimum, a needle holder, two skin hooks and retractors, sharp (i.e., iris) and blunt-nosed scissors, several small hemostats, and one pair of small single-toothed (i.e., Adson) forceps.

The choice of suture material depends on the location of the tendon injury. For repair of complete tendon injuries on the dorsum of the hand, nonabsorbable, synthetic braided sutures are preferred.4 Polyester sutures, such as Ethibond or Mersilene, are recommended. Nylon sutures are acceptable but are less ideal because colored nylon may be visible under the skin. Chromic and plain gut should be avoided because they will dissolve before adequate tendon healing has occurred. Silk is not desirable because of its reactivity. Most extensor tendons on the dorsum of the hand will accommodate 4-0 sutures, but 5-0 suture material may be needed for smaller tendons. Small, “plastic repair” tapered needles should be used to avoid tearing the tendon. Partial tendon injuries in the digits are best repaired with fine, synthetic absorbable sutures such as polyglactin (Vicryl). Complex lacerations that involve tissue loss and fraying of the tendon margins (e.g., table saw injuries) represent a particularly challenging clinical scenario that may make an otherwise straightforward tendon repair very difficult. In these cases, Lalonde and Kozin recommend closing the lacerated skin and tendon together (i.e., dermatotenodesis). Take large, composite bites of skin and tendon together, 5 to 10 mm on either side of the wound, with 3-0 or 4-0 nylon sutures tied outside the skin. Tighten the sutures until the digit is in full extension.5

Before repairing a tendon injury, it is imperative that the clinician use adequate anesthesia so that thorough wound exploration can occur. A field block or regional nerve block can be used on the dorsum of the hand, whereas local anesthesia or a digital nerve block can be used on the fingers. The choice of anesthetic composition has been the subject of long-standing controversy. Traditional teaching admonishes the use of epinephrine in anesthetics for fear of digital ischemia; however, many clinicians readily use lidocaine with epinephrine in the hand and fingers without complications. There is ample anecdotal and clinical evidence supporting the safety profile of epinephrine in digital anesthesia. Epinephrine has the benefit of prolonging the anesthetic effect and promoting a bloodless field during wound exploration and repair.6 It is important that the digits be fully anesthetized or, in the case of more proximal wounds on the hand, that the area around the wound be liberally anesthetized because many lacerations must be extended to afford access to the surgical field. It is a common error to avoid extending a laceration and to attempt examination, cleaning, or repair through a small initial skin laceration.

Following the administration of an anesthetic, place a tourniquet on the involved limb if hemostasis is problematic. It is absolutely essential that adequate control of blood flow be obtained before attempting to repair a tendon laceration. It is very difficult to find the proximal end of a retracted tendon in a bloody field. Before applying a tourniquet, wrap the patient’s arm in several layers of cast padding as a comfort measure, and elevate the arm for at least 1 minute to allow blood to drain by gravity. Place a blood pressure cuff on the middle to upper part of the arm, wrap several more layers of cast padding around the cuff, and then inflate it to 260 to 280 mm Hg. Once inflated, clamp the tubes tightly with a hemostat. The use of cast padding during inflation helps avoid inadvertent unraveling of the cuff. Use of a hemostat to clamp the blood pressure cuff tubes helps avoid a slow leak in the cuff with resultant deflation. A blood pressure cuff tourniquet is generally well tolerated by patients for approximately 15 to 20 minutes. If tendon repair cannot be accomplished in this time, it is likely that the injury is too complex for repair in the ED. When necessary, use parenteral sedation to help the patient tolerate a longer tourniquet time.

Atraumatic technique is essential for minimizing adhesions and scar tissue formation. Tendons should be handled delicately, with crushing force or excessive punctures with forceps and needles avoided. Forceps should be used only on the exposed, cut end of the tendon whenever possible.7

Patterns of Injury and Management

Treatment of extensor tendon injury depends primarily on whether the injury is open or closed, as well as the anatomic location of the injury. The most widely accepted classification system is that developed by Verdan,8 which divides the hand and wrist into eight anatomically based zones (Fig. 48-10). It is quite useful for emergency clinicians to become familiar with this classification because in many instances the zone of injury can help determine whether tendon repair should be attempted in the ED. One must keep in mind that repair of lacerated extensor tendons within 72 hours of injury is still considered primary closure. Therefore, although emergency clinicians may repair many extensor tendon injuries immediately, some injuries are best managed with delayed repair. In these cases, initial care in the ED should consist of sterile skin preparation, copious wound irrigation and inspection for foreign bodies, skin closure, splint application, and referral to a hand specialist for further care in 1 to 5 days. A dorsal plaster or fiberglass splint in which a metal foam finger splint is incorporated is an ideal way to totally immobilize a finger (Fig. 48-11) (see Chapter 50).

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Figure 48-10 Dorsum of the left hand. The injury classification system recommended by Verdan8 includes eight anatomically based zones. (Adapted from Blair WF, Steyers CM. Extensor tendon injuries. Orthop Clin North Am. 1992;23:142.)

Zone 7 and 8 Injuries1

Zones 7 and 8 consist of the area over the wrist and the dorsal aspect of the forearm, respectively. Extensor tendon lacerations in these regions can be quite complex and are therefore not repaired in the ED. Because of the close proximity of extensor tendons in the distal part of the forearm, lacerations such as stab wounds may appear innocuous but often result in multiple tendon lacerations. At the wrist level, the extensor tendons are covered by a retinaculum that is lined with synovium. Although this tissue allows smooth gliding of tendons during normal activity, the presence of synovium increases the risk for adhesions after tendon repair. In addition, lacerated tendons in the wrist and distal part of the forearm may retract away from the site of initial injury. This may make tendon retrieval and repair quite difficult and necessitate incision of the retinaculum and exploration of one or more compartments.

As a result of the potential complexity of these injuries, all tendon lacerations in zones 7 and 8 require formal surgical exploration and repair. ED management of these patients includes local wound care with primary repair of the skin and placement of a volar splint in 35 degrees of extension at the wrist and 10 to 15 degrees of flexion at the MCP joints. Promptly refer these patients to a hand surgeon so that repair may be undertaken within 1 week of injury.

Zone 6 Injuries1,4,9

Zone 6 consists of the area over the dorsum of the hand. Extensor tendon injuries in this region are frequently caused by lacerations from broken glass or another sharp object. Common pitfalls in ED management of these injuries are usually related to failure to recognize that the tendon has been injured. It is important to remember that these tendons are superficially located, partial tendon lacerations may occur, and weak extension of a digit is possible with a complete tendon laceration because of transfer of extensor function through the juncturae tendinum. Lacerations of the EIP or EDM tendons are evidenced by an inability to independently extend the index or little finger, respectively. In most cases, missing zone 6 injuries can be avoided if a careful physical examination is performed, including thorough wound exploration under sterile conditions using a tourniquet, adequate local anesthesia, and good lighting.

Extensor tendon injuries in zone 6 are generally appropriate for repair in the ED. Because of the juncturae tendinum, extensor tendons in zone 6 are less likely to retract than those in zone 7 or 8; however, the severed tendon may retract when the injury is more proximal. The distal end of a severed tendon is usually easy to find by passively extending the patient’s affected digit to bring the end into view. Retrieval of the proximal portion of a severed tendon is sometimes required and can usually be accomplished in the ED. Before searching for the proximal end of the tendon, the clinician should have a 4-0 nylon suture loaded onto a needle holder. When the proximal end is located, place this suture as a holding suture as far proximal as possible so that the tendon is not lost again. It is often necessary to use a scalpel to extend the wound proximally in a direction parallel to the course of the injured tendon to obtain adequate exposure. One should then begin to search for the tendon by lifting up this overlying skin with forceps and inspecting the proximal portion of the wound. Sometimes, the blood-stained end of a tunnel can be seen; this may contain the proximal end of the tendon. By gently placing a small hemostat or toothed forceps up this tunnel, the tendon stump can often be pulled into view.

Once both ends of the injured tendon have been located, the technique used for repair depends on the size and shape of the tendon. Whereas larger, round tendons can accommodate sutures that pass through the core of the tendon, smaller or flat tendons are difficult to repair with this technique. Most of the tendons in zone 6 can be repaired with either a modified Kessler or a modified Bunnell core suture technique using 3-0 or 4-0 nonabsorbable suture (Fig. 48-12). Both these techniques involve first placing a single suture in half of the cut tendon. Place the suture in the tendon core by inserting the suture needle into the exposed, cut end and then weaving the suture through the lateral tendon margins. Next, place the same suture through the core of the opposite half of the cut tendon. Tie the suture ends in a square knot in between the cut ends of the tendon to bring the two halves together.

Smaller tendons may be repaired with a figure-of-eight or horizontal mattress suture (see Fig. 48-12). Small, tapered needles should be used to avoid tearing the tendon. In a cadaver study comparing these multiple suture techniques, it was found that the modified Bunnell technique provided the strongest extensor tendon repair.10 In addition, this technique produced no gapping between the repaired tendon ends and minimized the postrepair restriction of flexion at the MCP and proximal interphalangeal (PIP) joints. It is important to passively test the degree of flexion at the MCP joint after a zone 6 tendon repair to be certain that the tendon has not been excessively shortened.

To improve the tensile strength of the repair, a number of other suture techniques may be used.4 One option is to increase the number of suture strands that cross the repair site (e.g., four strands rather than two). A cadaver study that compared various four-strand tendon repair techniques concluded that the Massachusetts General Hospital technique was more resistant to gap formation than either the Krackow-Thomas or the four-strand modified Bunnell technique.11 However, this cadaver model could not assess tendon shortening or subsequent range of motion.12 Another way to improve tensile strength is to place a peripheral suture in addition to the core suture. Place a running cross-stitch suture of synthetic, absorbable material (e.g., 5-0 polyglycolic acid, polyglactin, polydioxanone) circumferentially around the repair site or just on the dorsal surface of the tendon across the laceration site. Alternatively, place sutures laterally along both sides of the tendon, starting at about 1 cm on either side of the repair site. The ultimate choice of repair technique will depend largely on the treating clinician’s familiarity with extensor tendon repair, as well as the size of the tendon.

The approach to partial extensor tendon lacerations is not well defined, and no definitive standard of care exists. One evidence-based analysis identified 141 papers in its literature search, but none were relevant to the question of repair of partial extensor tendon injuries.13 The authors concluded that there is no direct evidence to assist in answering this question. Given the lack of literature on the subject, a reasonable approach may be to extrapolate from data on flexor tendon injuries. It has been demonstrated that many partial flexor tendon lacerations do well without repair,14 but hand surgeons still disagree on the need for repair of these injuries. In a survey of hand surgeons, 30% of respondents repaired all partial flexor tendon lacerations and 45% repaired only lacerations with greater than 50% involvement of the cross-sectional area.15 Except at the wrist level, extensor tendons are not covered with synovium and are less likely than flexor tendons to form adhesions after repair. This encourages some authors to recommend repair of most partial extensor tendon lacerations. Although the ideal approach to these injuries is not known, it is reasonable to consider repair of partial extensor tendon lacerations to be optional if less than 50% of the cross-sectional area is involved. However, if not repaired, such injuries must be splinted for 3 to 4 weeks to ensure that a partial laceration is not converted into a complete injury. Skin closure, splinting, and referral for follow-up is a standard approach to unsutured partial extensor tendon lacerations.

After repair of a lacerated EDC tendon in zone 6, apply a plaster or fiberglass volar splint so that the wrist is in 30 to 45 degrees of extension, the affected MCP joint is in neutral (0 degrees of flexion), and the unaffected MCP joints are in 15 degrees of flexion. The PIP and distal interphalangeal (DIP) joints should be allowed full range of motion. After 10 days, the MCP joints are allowed 20 to 30 degrees of flexion. If there is an isolated EIP or EDM tendon injury, only the index or little finger must be included in this splint. Dynamic extension splinting may be used as early as 2 days after tendon repair, so close follow-up is recommended.16

Zone 5 Injuries17,18

Zone 5 consists of the area over the MCP joint. Open injuries in this region should be considered secondary to a human tooth bite until proved otherwise (Fig. 48-13), especially if the injury occurs over the first or second MCP joint because this is frequently the location of a clenched-fist (“fight-bite”) injury. ED evaluation must begin with a careful and persistent history and physical examination, although patients’ reluctance to admit to punching someone in the mouth is notorious. The wound should be inspected through its full range of motion because the position of the EDC tendon changes with hand position. It is generally recommended that radiographs be obtained for all these injuries to evaluate for metacarpal head fractures, air in the joint space, or the presence of a foreign body such as a tooth fragment (Fig. 48-14).16

If after a thorough evaluation it is determined that a human bite in this region has resulted in a superficial skin laceration only, without injury to the underlying tendon or joint, outpatient management is appropriate. The wound should be copiously irrigated and left open. A volar splint is applied with the wrist in 45 degrees of extension, the MCP joints in the neutral position (0 degrees of flexion), and the hand dressed with a bulky dressing. The use of prophylactic antibiotics for these “low-risk” human bites on the hand is controversial, and clinical trials have yielded mixed results.19,20 Despite the lack of compelling clinical evidence for either approach, many authors recommend that 3 to 5 days of prophylactic antibiotics be given to these patients. Regardless of whether antibiotics are prescribed, patients should be seen in 24 to 36 hours for a repeated examination to evaluate for wound infection.

If a human bite results in tendon damage, including partial or complete laceration, some clinicians opt for admission and intravenous antibiotics. However, no specific standard of care exists. Outpatient therapy is acceptable in a reliable patient who has access to follow-up. Delayed closure with evaluation and repair of the tendon should be undertaken by a hand surgeon after 7 to 10 days of antibiotic therapy.4,16 Primary closure of even seemingly clean and well-irrigated human bites in this region is not advisable because of the increased risk for wound infection, as well as the potential for septic destruction of the MCP joint if it is violated. If an open joint is noted on physical examination, a more aggressive approach is warranted. Such patients are generally admitted for intravenous antibiotics after copious irrigation.4,16

If a patient suffers a zone 5 tendon injury and it can be determined with complete certainty that it was caused by a relatively clean, sharp object rather than by a human bite, primary closure is appropriate. Referral of these injuries to a hand surgeon is common practice given the complexities of the injury and possible sequelae. Careful repair of lacerations involving both the EDC tendon and the sagittal bands is necessary to prevent subluxation of the EDC tendon away from the center of the metacarpal head. Initial ED management of non–human bite injuries is often limited to skin closure, splinting as described earlier, and referral to a hand surgeon within 1 to 5 days.

Closed extensor tendon injuries in zone 5 usually result from the acute or recurrent application of compressive force to the MCP joint capsule. Closed injuries in this region are sometimes referred to as a boxer’s knuckle. Repetitive closed injury to the MCP joint region can produce small tears in the EDC tendon, the sagittal bands, or the joint capsule. These patients tend to have chronic and recurrent pain and swelling in the MCP joint region but usually have normal radiographic findings. Acute trauma may result in the same injuries or cause more severe damage to the extensor hood. Such patients may have complete disruption of the extensor mechanism, including damage to the central tendon and the sagittal bands. The MCP joint is swollen, has decreased mobility, and may exhibit an extensor lag. Traumatic subluxation of an EDC tendon may be present and usually involves the middle finger with subluxation to the ulnar side (Fig. 48-15). Dislocation to the radial side is less common, probably because of the juncturae tendinum on the ulnar side, which can compensate for injuries to the ulnar sagittal band.21 The subluxation becomes more prominent with flexion at the MCP joint. Controversy exists regarding the initial management of closed injuries in this region. Whereas some authors prefer initial surgical repair,18 others use an initial trial of extension splinting in some or all cases.4,16,17,21 Splinting the MCP joint in neutral or slight flexion for 6 weeks has been recommended for dislocations initially seen within 3 weeks of injury, with operative repair being reserved for more delayed manifestations or patients who fail splint therapy.16

Zone 4 Injuries17

Zone 4 consists of the area over the dorsal aspect of the proximal phalanx between the MCP and PIP joints. The extensor tendon is a broad, flat structure in this region and is relatively easy to repair. Because the extensor tendon is flat and conforms to the roundness of the proximal phalanx, tendon injuries in this area generally result from a laceration and are almost always incomplete. As a result, extension at the PIP joint is not usually impaired. It is therefore imperative that all these wounds be explored carefully while remembering that the extensor tendon lies immediately beneath the thin overlying skin. Tendons tend to not retract in this area, so close inspection will usually result in location of the injured tendon.

A hand surgeon generally repairs central slip lacerations or any laceration that results in an extension lag at the PIP joint. The decision whether to repair a partial tendon laceration in zone 4 and whether it should be repaired by the emergency clinician is best discussed with the consulting hand surgeon. In general, because of the duality of the extensor system in this region, lacerations of a single lateral slip can either be repaired with 5-0 nonabsorbable suture or be left unrepaired and splinted. Placement of a running suture or simple interrupted sutures with buried knots is appropriate for this area. Postrepair splinting depends on the presence of tension at the repair site. Minor lacerations in zone 4 that do not result in tension on the repair site can be treated with a finger guard for 7 to 10 days and early range of motion. Treat larger lacerations or those that result in tension at the repair site with a splint that extends from the forearm to the digit for 3 to 6 weeks. The splint should be applied so that the wrist is in 30 degrees of extension, the MCP joint is at 30 degrees of flexion, and the PIP joint is in neutral position. Group the fingers so that either digits 2 and 3 or digits 3 through 5 are immobilized.

It is important to recognize that complex partial tendon lacerations (e.g., laceration of a lateral slip with a saw) in zone 4 may result in damage to the gliding layer located between the tendon and the bone. If the patient is still able to actively extend the digit at the PIP joint, these complex partial tendon lacerations are best managed by débriding the frayed tendon ends and splinting the digit in extension rather than attempting to suture the damaged tendon. The splint should be worn for 10 days, followed by active range of motion.

Zone 3 Injuries1,16,18

Zone 3, the area over the PIP joint, is a common site of both closed and open injuries. An open injury usually results from laceration with a sharp object. It is imperative that these wounds be carefully explored in the ED to rule out penetration of the joint capsule. Patients with wounds that are suspected of penetrating the joint are generally taken to the operating room for surgical exploration, irrigation, and treatment with intravenous antibiotics, but protocols vary.

Zone 3 tendon lacerations can result in long-term deformity if not carefully repaired, and patients with such injuries are commonly referred to a hand surgeon. Partial lacerations of the central slip or lateral bands are managed variably, and it is advisable to discuss these injuries with the consulting hand surgeon. Lacerations in this area may sometimes result in a complete central slip injury. This may manifested as an acute boutonnière (“buttonhole”) deformity in which the PIP joint rests in 60 degrees of flexion. The signs may be subtler, however, and may be noticeable only by weakened extension at the PIP joint or incomplete extension by only a few degrees.

A boutonnière deformity develops when the central slip is ruptured by an open or closed mechanism that leads to unopposed action of the flexor digitorum superficialis tendon (Fig. 48-16). This results in flexion at the PIP joint, protrusion of the head of the proximal phalanx between the two lateral bands, and disruption of the triangular ligament. When this occurs, the lateral bands are displaced volar to the axis of motion of the PIP joint. The lateral bands then paradoxically become flexors of the PIP joint. In addition, the extensor hood mechanism is pulled more proximally, which results in increased tension on the TEM and hyperextension at the DIP joint. Thus, a boutonnière deformity consists of flexion of the PIP joint with hyperextension at the DIP joint.

Open central slip injuries are usually managed operatively, and complex injuries may require direct attachment of the tendon to bone or tendon reconstruction. If the consulting hand surgeon chooses not to repair the tendon injury immediately, close the skin and apply a splint in the same fashion as described for zone 4 injuries. Thermoplastic splints allow splinting of the hand without involvement of the wrist but are generally not available in the ED setting. Promptly refer these patients to a hand surgeon so that repair may be undertaken within 1 week of injury.

Patients with closed injuries in zone 3 are commonly encountered in the ED. They may complain of a direct blow to the dorsal PIP joint or a “jammed” finger. This injury occurs when an object such as a ball delivers a sudden axial loading force with forced flexion of the PIP joint while it is extended. These patients commonly complain of a painful, swollen PIP joint, which often makes the examination difficult. Some of these injuries may represent PIP joint dislocations that were spontaneously or manually reduced before arrival of the patient at the ED. The tendon injury that is important to recognize in this setting is an occult isolated central slip rupture. Patients may have decreased extension at the PIP joint, but extension is generally normal because the lateral bands are the primary extenders of this joint. With forced extension against resistance, patients usually have pain and may have decreased strength. To eliminate pain as the cause of the decreased mobility, it may be helpful to test PIP extension against resistance after performing a digital block. With acute central slip rupture, PIP joint extension may be particularly weak when the MCP and wrist joints are held in maximal flexion. In this position, a 15-degree or greater loss of active extension is highly suggestive of a central slip injury.18 The Elson test may also help identify this injury (Fig. 48-17).22

A boutonnière deformity does not usually develop in patients with closed zone 3 injuries until 10 to 21 days after injury. The only way to prevent this deformity is to have a high index of suspicion for its presence and treat these patients conservatively. It is advisable that all patients with a swollen, tender PIP joint and pain with flexion or extension be splinted and referred for close follow-up. Apply a dorsal splint overlying the PIP joint while keeping it in full extension. This can be accomplished with an aluminum foam-backed splint or a Bunnell (“safety pin”) splint, although the latter may not be available in the ED.16 The MCP and DIP joints should be left free to have full, active range of motion (Fig. 48-18). If a central slip attachment fracture is present, orthopedic consultation is recommended because these patients may require surgical internal fixation.23

Zone 1 and 2 Injuries1,4,16,18

Zones 1 and 2 consist of the area over the DIP joint and the middle phalanx, respectively. In zone 2 the conjoined lateral bands come together to form the TEM and are held together, in part, by the triangular ligament. The TEM inserts on the base of the distal phalanx and allows extension at the DIP joint. Complete disruption of the TEM results in an inability to extend at the DIP joint. Because of the unopposed action of the flexor digitorum profundus (FDP) tendon, the DIP joint rests in the flexed position. This is known as a mallet deformity of the finger (Fig. 48-19A). When evaluating DIP motion, it is important to isolate the function of the extensor tendon by holding the PIP joint in full extension (Fig. 48-19B and C). Normally, full active extension is possible.

Tendon lacerations in zones 1 or 2 that result in a partial or complete mallet deformity generally warrant discussion with a hand surgeon (Fig. 48-20). Management consists of repair of the lacerated tendon and postrepair immobilization. Some surgeons will use only an external splint; others prefer placement of a Kirschner wire (K-wire) through the distal phalanx into the middle phalanx to help stabilize the joint. One technique for tendon repair involves placement of a roll-type suture (dermatotenodesis) that incorporates the tendon and overlying skin into a single suture (Fig. 48-21).1,16 The DIP joint is then splinted in full extension for at least 6 weeks. Occult partial tendon lacerations are important to recognize to prevent the development of a mallet deformity. If there is a partial tendon laceration in zone 1 or 2 that does not result in any extension lag, the approach to repair is variable, and it is advisable to discuss the repair with the consulting hand surgeon. In general, partial tendon lacerations involving less than 50% of the tendon area that do not result in an extension lag may be splinted in extension for 7 to 10 days with or without repair of the tendon itself.16 Partial tendon lacerations involving more than 50% that do not result in an extension lag may be repaired by a hand surgeon or an emergency clinician who is experienced in the repair of these injuries. In either case it is advisable to discuss with the consultant hand surgeon whether the tendon will be repaired in the ED or the operating room.

If a zone 1 or 2 partial tendon laceration is repaired in the ED, it can be approximated by using a combination of running and cross-stitch sutures16 with 5-0 nonabsorbable (e.g., Prolene) suture material. In general, given the diminutive size of the extensor tendon in this region, placement of core sutures is not possible. It is important that the tendon ends be approximated but not pulled too tightly; otherwise, joint stiffness and limitation of flexion will occur. After repair of a partial tendon laceration, splint the DIP joint in extension for 6 to 8 weeks, followed by 2 to 4 weeks of night splinting and active range-of-motion exercises. Patients should be warned after tendon repair that there is likely to be some residual loss of flexion at the DIP joint, even in the best case.

Closed injuries in zones 1 and 2 may result in a partial or complete mallet deformity, depending on the injury pattern. These injuries are usually caused by an axial loading force with forced flexion of the DIP joint while it is being held in extension. A common ED scenario involving this injury is a patient who complains of pain and swelling at the DIP joint after a ball strikes the fingertip.

Closed tendon injuries in this region can generally be classified into three types. The first type of injury consists of closed rupture of the TEM. The second type of injury is an avulsion fracture of the dorsal lip of the distal phalanx. This fracture is intraarticular, but there is no volar displacement of the remaining portion of the distal phalanx. Avoid attempting to reduce displaced fractures before splinting because any reduction is unlikely to be maintained without surgery; mallet fingers with associated fractures are best splinted and referred.

Treat both type 1 and type 2 injuries with splinting in full extension for 6 to 8 weeks. Either a dorsal or palmar splint should hold the DIP joint in extension or slight hyperextension (5 to 10 degrees) while allowing free range of motion of the PIP joint (Fig. 48-22). With a properly fitted splint, no flexion of the DIP joint should occur. The splint can be constructed from an aluminum, foam-backed splint or from a prefabricated Stack splint. A Cochrane review of treatment of mallet finger injuries found inadequate data to establish the most effective type of splint, but the Stack splint is the editor’s preference for ease of application and patient comfort.24 Be careful to avoid excessive sustained pressure from the splint on the DIP joint area because skin necrosis may occur. Strictly maintain the DIP joint in full extension for 6 to 8 weeks, including during sleep and splint changes. Adherence to this instruction is essential since patients have a tendency to test its function on their own, thus tearing the healing tendon fibers. The most common reason for failure of treatment is patient noncompliance with prolonged splinting. Whenever the splint is removed, support the distal fingertip in full extension at all times. Should DIP joint extension be lost at any point during the initial treatment period, reset the treatment clock for an additional 6 weeks.

The third type of closed injury is an intraarticular avulsion fracture of the dorsal lip of the distal phalanx with volar displacement of the remaining portion of the distal phalanx (Fig. 48-23). Such injuries are best referred for definitive treatment consisting of either surgery or more complex splinting. Normally, the DIP collateral ligaments hold the distal phalanx in place; however, if there is a large enough fracture fragment (usually >50% of the articular surface), the remaining distal phalanx fragment displaces in the volar direction secondary to unopposed action of the FDP tendon. When volar displacement of the distal phalanx occurs, this injury may require more aggressive treatment to achieve an optimal outcome.18 Unfortunately, there are no adequate published randomized, controlled trials comparing operative versus conservative treatment of these injuries.24 Operative repair usually involves open reduction and internal fixation of the fracture with placement of a K-wire for additional stabilization. It is important to remember that it is the presence of volar subluxation, not the size of the avulsion fracture, that is most often considered when determining the need for operative management.

Any injuries, whether open or closed, that result in complete disruption of the TEM may result in a swan neck deformity (Figs. 48-24 and 48-25). This deformity consists of flexion at the DIP joint (a mallet finger) and hyperextension at the PIP joint. It results from increased extension force on the middle phalanx caused by dorsal and proximal displacement of the lateral bands. This complication can often be avoided if disruption of the TEM is diagnosed and treated correctly in the ED.

Complications

All extensor tendon repairs are subject to the usual complications of wound infection and skin breakdown secondary to prolonged splinting. Tendon rupture is a rare complication after tendon repair and may result from inadequate suture technique or premature motion against resistance. It is important when extensor tendons are repaired that at least five throws be used and a square knot be tied. All extensor tendon repairs require some period of complete immobilization during tendon healing, and the emergency clinician must stress the necessity for patient compliance.

Extensor tendon injuries in zone 7 tend to have the worst prognosis. Because of the presence of a synovial lining, postrepair adhesions may develop. Adhesions may lead to decreased excursion of the extensor tendons with resultant decreased mobility at the wrist. There may also be limitation of finger flexion when the wrist is flexed, as well as limitation of finger extension when the wrist is extended. Because of the lack of synovium, the low risk for adhesions, greater tendon excursion, the relatively simple anatomy, and the usual lack of associated injuries, zone 6 tendon injuries tend to have fewer complications than other areas of the hand. The tendons in zone 6, however, do have a tendency to shorten if the ends are approximated too tightly. This may result in restriction of PIP and MCP joint flexion. In addition, worse outcomes may occur with complex zone 6 tendon injuries when additional soft tissue or bony injuries are present.16,25

Zone 5 injuries are particularly prone to infection because injuries in this region commonly occur from a human bite. In addition, if the extensor hood covering the MCP joint is not repaired carefully, subluxation of the EDC tendon may occur.9 If complex partial tendon lacerations in zone 4 are managed too aggressively, tendon shortening and stiffness may result. As discussed previously, these injuries are often best managed by splinting alone. A common complication of zone 3 extensor tendon injury is the development of a boutonnière deformity, which usually results from failure to diagnose or adequately immobilize a central slip injury. Similarly, undiagnosed or improperly treated extensor tendon injuries in zones 1 and 2 may lead to either a swan neck or a chronic mallet deformity of the digit. DIP joint splinting itself may result in skin ulceration or tape allergy, often occurring in the second week of treatment.16 Skin breakdown may ensue if the DIP joint is splinted in hyperextension because of decreased skin perfusion.

Postrepair Care and Rehabilitation

Proper care after diagnosis and repair of an extensor tendon injury is extremely important for optimal patient outcome. Even the best initial tendon repair can have a poor result if subsequently treated improperly. Rehabilitation of tendon injuries has evolved since 1980 to include dynamic splinting and active range-of-motion exercises to achieve maximal motion of the affected digit.

Zone 1 and 2 injuries are usually treated with static splinting, as described previously. After 6 weeks, active range-of-motion exercises should begin. Night splinting is recommended for an additional 2 to 6 weeks.1,16,18 Some authors also recommend wearing the splint during the day when performing heavy tasks.16 It is advisable to give the patient a number of extra splints so that the patient (or family) can change the splint frequently to avoid pressure injury. During splint changes it is important that the DIP joint be held in full extension either by using the other hand or by placing the finger against a table. If an extension lag develops at any time, continuous splinting must be repeated. Closed injuries of the central slip (zone 3) are often treated with a boutonnière splint for 4 to 6 weeks, followed by 2 to 6 weeks of gradual flexion exercises and night splinting. During the initial period of immobilization, the patient should be instructed to passively flex the DIP joint every hour to maintain gliding and proper position of the lateral bands.

Lacerations in zones 3 and 4 have traditionally been treated with static splinting from the forearm to the digits. An alternative approach is to splint only the DIP and PIP joints in extension and begin a “short-arc-motion” protocol within 1 to 2 days of repair.26 This consists of active motion at the PIP joint progressing from 0 to 30 degrees the first 2 weeks to 0 to 50 degrees in the fourth week. When compared with static splinting, this protocol may lead to better PIP and DIP joint flexion without resulting in tendon rupture or a boutonnière deformity. Dynamic extension splints are also proving to be useful for rehabilitation of zone 3 and 4 tendon injuries.16,26,27

Early motion after extensor tendon repair has been found to be most useful in zones 5 through 7. A dynamic extension splint in which the wrist is extended 45 degrees and all finger joints rest in the neutral position is commonly used. A volar block allows 30 to 40 degrees of MCP joint flexion, whereas a dynamic traction mechanism passively extends the digits. Dynamic splinting is started 1 to 3 days after repair. Active motion is added at 3 to 4 weeks, and resistance is added at 7 weeks. A randomized, controlled trial of zone 5 and 6 extensor tendon repairs found total active motion with dynamic splinting to be superior to static splinting at 4 to 8 weeks, but not at 6 months. However, grip strength in the affected hand was improved at 6 months with dynamic splinting.28 A short-arc-motion protocol with controlled active motion at the MCP joint has also been shown to be safe and effective when started 24 to 48 hours after repair.9 One comparative trial reported that dynamic extension splinting and controlled active mobilization worked equally well for zone 5 and 6 tendon injuries.29 All early range-of-motion protocols are most beneficial when managed closely by a skilled hand therapist. Patient age, associated injuries, suture type, and repair technique all affect the choice of rehabilitation protocol.9 Most importantly, patients must be reliable and motivated to take advantage of early range-of-motion techniques. It is best to refer patients to a hand surgeon or hand therapist as soon as possible after repair so that rehabilitation can begin in a timely manner.

Extensor Tendon Injuries of the Foot

The extensor tendons of the foot are less commonly injured than the extensor tendons of the hand and wrist. The most important extensors of the foot and ankle that may be injured and encountered in the ED are the tibialis anterior, extensor hallucis longus (EHL), and extensor digitorum longus (EDL) tendons.

The tibialis anterior muscle originates on the shaft of the tibia and interosseous membrane and inserts on the medial cuneiform and the base of the first metatarsal. The tibialis anterior extends the foot at the ankle joint and inverts the foot at the subtalar and transverse tarsal joints. Spontaneous rupture of the tibialis anterior tendon may be seen in both elderly and young patients who have been injured during athletic activity. Injury to this tendon commonly results from forceful attempted dorsiflexion of the ankle while it is held fixed in the plantar-flexed position.28 Patients generally have decreased strength of foot dorsiflexion because the toe extensors are used to accomplish this motion. Rupture or laceration of the tibialis anterior tendon should be promptly referred to an orthopedic surgeon for consideration of formal operative repair. In some cases, closed injuries of the tibialis anterior tendon may be managed nonoperatively, depending on the extent of the patient’s symptoms and functional impairment.30

The EDL and EHL tendons both originate from the shaft of the fibula and interosseous membrane. The EHL tendon inserts into the base of the distal phalanx of the great toe, and the EDL tendon divides into four branches that insert on toes 2 through 5 (Fig. 48-26). Both the EHL and the EDL tendons primarily result in extension of the toes and dorsiflexion at the ankle. The extensor digitorum brevis (EDB) and extensor hallucis brevis (EHB) muscles originate from the upper part of the calcaneus. The EHB tendon joins the lateral aspect of the EHL tendon before inserting on the great toe. The EDB muscle gives rise to three tendons that join the lateral side of the EDL tendons going to toes 2 through 4 (see Fig. 48-26).

Injury to the EHL and EDL tendons may result from a sharp object lacerating the dorsum of the foot. Patients may have weakness of or an inability to extend the involved toe. The examiner may be unable to palpate the injured tendon. Whether one should repair EHL or EDL tendon lacerations is controversial. However, many authors favor repair because failure to repair EDL tendons may result in a claw deformity of the adjacent toes.31 Lacerations of the EHL and EDL tendons at the level of the ankle are usually repaired, whereas lacerations on the dorsum of the foot and the toe are managed variably. If the patient has significant pain or any flexion deformity of the involved toe, one should probably repair the lacerated tendon. Repair is also favored when both ends of the tendon are easily visualized in the wound and the patient is willing to undergo prolonged immobilization after repair.32 Because management of these injuries is controversial, it is advisable to discuss the care of these patients with the consulting orthopedic surgeon. Extensor tendon repair of the foot is not usually performed in the ED setting. Superficial cutaneous nerves are easily injured on the dorsum of the foot during wound exploration, which can lead to the formation of a chronic, painful neuroma. If the injury is repaired in the ED, the technique for repair is similar to that used for the dorsum of the hand (zone 6). A posterior splint that includes the toes should be applied after tendon repair. Splint the ankle in 90 degrees with the toes in the neutral position.

Flexor Tendon Injuries

Flexor tendon injuries are more difficult to diagnose and more challenging to treat than extensor tendon injuries. In general, repair of flexor tendons is not performed by emergency clinicians. Anatomic and biomechanic issues, the physiology of flexor tendons and tendon healing, and follow-up rehabilitation and physical therapy are complex and formidable. A satisfactory outcome is more difficult to achieve with an injured flexor tendon than with a similar degree of injury to an extensor tendon. Unlike extensor tendons, flexor tendons are influenced by a number of pulley mechanisms. The tendon must glide through delicate tendon sheaths, so even a minor defect in tendon integrity is physiologically magnified (Fig. 48-27). In addition, flexor tendon injuries are often associated with nerve and vascular injuries.

The main clinical mandates for emergency clinicians are to diagnose or consider flexor tendon injuries, provide initial proper wound care, and expedite appropriate consultation and follow-up. Unlike the more superficial extensor tendons, flexor tendons are often buried deep within the hand and forearm, and it is frequently not readily possible to visualize the tendon in the recesses of a wound. Puncture wounds of the palm often injure flexor tendons, but deep puncture wounds prohibit visualization of the injured structures (Fig. 48-28). Therefore, a partial flexor tendon injury may be clinically silent until rupture occurs days or weeks later. Delayed repair of undiagnosed flexor tendons may be complicated by tendon retraction or scar formation, and tendon transfer and grafting may be necessary.

image

Figure 48-28 Deep puncture wounds of the palm may injure the flexor tendons. A, The depth of this wound precludes extensive exploration to visualize the tendon. Partial tendon lacerations may still initially allow full function. Clues to a partial flexor tendon laceration include weakness of flexion or pain with attempts at flexion against resistance, but many partial lacerations are clinically silent. Despite full function, this wound’s location and depth suggest the possibility of at least a partial tendon injury. The prudent course would include meticulous wound care, splinting, skin closure, and contact with a hand specialist to arrange reexamination in a few days while cautioning the patient that a flexor tendon injury may be present and delayed repair for up to 1 to 3 weeks yields results comparable to immediate repair. Immediate repair is often eschewed because of swelling and wound contamination. Further care may be required. B, This palm laceration from the sharp top of a metal can seemed superficial. Function was normal. C, When examined with the fingers in extension, the tendon was readily visualized, a surprise to the clinician given the benign and superficial appearance of the laceration. The visualized tendon was intact. D, When the fingers were flexed (arrow), the position of the hand when the injury occurred, a 20% to 30% laceration of the tendon was demonstrated. E, This injury will do well with 3 weeks of splinting and no tendon repair. Follow-up with a hand surgeon in a few days is prudent. Note the outrigger aluminum splint incorporated into a short-arm plaster splint (arrow; see Fig. 48-11).

It may not be possible on the initial visit for the emergency clinician to diagnose the presence of all flexor tendon injuries, nor the full extent of such injuries. Help may be obtained from a specialist if logistically possible, but generally, there is no mandate for such immediate on-site examination when questions about tendon integrity exist. Even though consultation is advised before definitive disposition, the same limitations in the examination would similarly confront a specialist. Individual scenarios and local protocols will guide the timing and degree of consultation in the ED.

Notwithstanding the previous discussion, complete flexor tendon injuries are often apparent on physical examination, either by testing individual tendons or by the resting posture of the injured hand. In contrast, partial tendon lacerations are commonly clinically unappreciated because no functional deficit is evident. Clinical clues to a potential flexor tendon injury are weakness of flexor tendon function (difficult to evaluate in an acutely injured extremity), pain at the site of injury when performing active range of motion against resistance, and an abnormal resting posture of the hand (Fig. 48-29A and B), which can be determined by careful examination but is always difficult in a child or uncooperative patient (see Fig. 48-29C and D). However, the emergency clinician may not be able to arrive at a complete or accurate diagnosis without surgical exploration. Moreover, it is counterproductive and potentially harmful to attempt extensive exploration of the deep recesses of the hand or forearm in the ED merely to visualize a suspected flexor tendon injury.

Completely transected flexor tendons are surgically repaired by a consultant, usually on an elective basis. Most hand surgeons are reluctant to perform primary repair of a flexor tendon injury on ED patients and prefer to have the wound cleaned, the skin closed, and the patient scheduled for subsequent definitive repair. The final outcome of flexor tendon surgery depends on multiple factors; however, surgical repair of most flexor tendons accomplished within 10 to 21 days of injury (delayed primary repair) generally produces final outcomes similar to those with immediate repair.33–35 Therefore, if a partial tendon laceration is not diagnosed at the initial visit and rupture is noted at the time of removal of the skin sutures or inspection of the wound, immediate referral to a hand surgeon would be expected to provide a similar result as that expected had the injury been diagnosed at the time of the initial ED visit.

Partial flexor tendon lacerations, if appreciated, are usually treated by careful wound cleaning, skin closure, splinting, and referral for reevaluation in 1 to 5 days. Definitive treatment of partial lacerations remains quite controversial. Some surgeons will repair all partial tendon lacerations, whereas others take a more conservative approach. The conservative approach is supported by experimental evidence suggesting that surgical repair of partially lacerated tendons results in weaker tendons than if the tendons were not surgically repaired.36 Wray and colleagues suggest forgoing suturing in favor of splinting, followed by early mobilization of tendons with lacerations involving 25% to 95% of the cross-sectional area.37 Without conclusive evidence either way, a reasonable approach would be to suture tendon lacerations involving greater than 50% of the cross-sectional area with special surgical techniques, suture tendon lacerations involving 25% to 50% of the cross-sectional area with simple or special suture techniques, and simply trim injuries that affect less than 25% of the cross-sectional area to promote normal gliding function.35 All decisions concerning the type and timing of repair should be made in concert with a consultant while keeping in mind that some decisions regarding surgical repair of partial injuries cannot be made for weeks or months.

Following evaluation of a known or suspected flexor tendon injury, suture the skin and splint the hand to protect the tendon and minimize retraction. Techniques vary, and the initial splinting positions are probably inconsequential to the final outcome if the duration of splinting does not exceed 7 to 14 days. As a guideline, splinting with the wrist in 30 degrees of flexion, the MCP joints in 70 degrees of flexion, and the IP joints in 10% to 15% of flexion has been recommended.38 There are no data to support or refute the value of prophylactic antibiotics for any soft tissue injury that has been properly cleaned. Although no definitive standard of care has been promulgated, many clinicians prescribe 3 to 5 days of antibiotics effective against gram-positive organisms (including Staphylococcus aureus) if the tendon is injured. Antibiotics are recommended if the degree of contamination is significant, cleaning has been delayed, there are unusual sources of injury, or the patient is immunocompromised. Specific written instructions with a definite follow-up time frame outlined and assistance in patient referral will probably improve the final outcome, but flexor tendon injuries often produce lifelong disability despite even ideal care in the ED.

Achilles Tendon Rupture

An Achilles tendon rupture can lead to serious morbidity. Although definitive care of such injuries is not performed in the ED, it is important to make the correct diagnosis and institute proper and prompt referral. This injury is easy to miss, and it is not always diagnosed on the first visit. In a recent case series the diagnosis was missed in more than 20% of cases.39 It is usually initially considered a minor ankle sprain by both the patient and clinician. Rupture often occurs with steroid use, with degenerative conditions, and in the elderly, but Achilles tendon rupture can also occur in healthy athletic patients with no history of heel pain and often with seemingly minor trauma. Fluoroquinolone antibiotics have been implicated in Achilles tendon rupture, especially in the elderly. This led the Food and Drug Administration to issue a “black box” warning on the use of all fluoroquinolones for this condition in 2008. Mechanisms for rupture include sudden overload of the tendon by forceful plantar flexion of the foot, as in recreational sports involving jumping (basketball), pushing a heavy object, or stepping up. The injury is usually a complete as opposed to a partial tear, and rupture occurs in a region 2 to 6 cm proximal to the tendon’s insertion on the calcaneus. Occasionally, a snap or pop may be appreciated by the patient. Pain may not be perceived in the tendon itself; instead, heel or diffuse ankle pain may be experienced. Because multiple structures plantar-flex the foot, the initial result is weakness of the ankle, and importantly, complete loss of motion of the foot does not occur. Characteristic ecchymosis may be evident in 48 to 72 hours after injury.

The diagnosis may be suggested by a palpable defect in the tendon, but this can be subtle or absent (Fig. 48-30). The calf squeeze test (Thompson’s test) is a physical finding that is 96% to 100% sensitive. To perform this test, have the lie patient prone on a stretcher with the feet overhanging the edge. Squeeze the calf and observe for strong passive plantar flexion of the foot. If the foot does not move, a complete tear is diagnosed (Fig. 48-31). When the diagnosis is not clinically certain or when the possibility of other injuries exists, emergency imaging should be performed. With isolated Achilles tendon rupture, standard radiographs will be normal. Magnetic resonance imaging (MRI) is diagnostic but not usually indicated in the ED. Some practitioners have recently advocated using ultrasound to diagnose both complete and partial tendon ruptures.40 Sonography is an appealing diagnostic tool given its relatively low cost, portability, safety profile, and the ability to perform static and dynamic evaluations and compare the contralateral side. A sonographic Thompson test can also be performed by directly visualizing the tendon with a high-frequency, linear ultrasound probe while the calf muscle of the prone patient is gently squeezed. The Achilles tendon is assessed, proximally to distally, for synchronous movement. Complete tears are recognized by retraction of the proximal tendon end; echogenic adipose tissue (Kager’s fat) may be seen to herniate between the torn ends of the tendon (Fig. 48-32). No studies have evaluated the diagnostic accuracy of ultrasound performed by emergency physicians for Achilles tendon rupture.39 Treatment varies from conservative splinting to surgery and is controversial. Splinting the foot in mild plantar flexion (gravity equinus) can protect the tendon for follow-up in 1 to 5 days.

Knee Extensor Tendon Rupture41

The extensor mechanism of the knee is composed of the four strong quadriceps muscles, the femoral quadriceps tendon, the patella, the patellofemoral and patellotibial ligaments, the medial and lateral retinacula, the patellar tendon, and the tibial tubercle. Both the quadriceps and patellar tendons are subject to rupture. Quadriceps tendon rupture is more common in the elderly and in those with systemic degenerative disease, arthritis, and steroid use and is associated with significant morbidity regardless of treatment. It may also be seen in younger patients, such as occurs after taking a basketball jump shot. Performance-enhancing steroid use is likewise a risk factor in these patients. Patella tendon rupture is also a serious injury but occurs more commonly in healthy patients younger than 40 years participating in sporting events.

As with Achilles tendon rupture, rupture of the knee extensor mechanism is not always initially suspected or diagnosed; it is missed by primary care providers in 20% to 30% of cases. The mechanism of quadriceps tendon rupture is usually a deceleration injury with the knee partially flexed, coupled with a strong quadriceps muscle contraction when the foot is fixed. The trauma may be seemingly minor, such as missing a step or jumping from a low height. A common history is an elderly patient who is descending steps or walking off a curb, misses a step, and attempts to keep from falling. A popping or tearing sensation may be elicited. The pain may be deceptively minor. The rupture may be partial but is more often complete. Quadriceps tendon rupture usually occurs transversely just proximal to the patellar insertion, with or without an avulsion fracture of the superior pole of the patella. A suprapatellar gap may be palpated. The mechanism of patella tendon rupture is usually an excessive load on the flexed knee during athletic activities. The patient complains of pain and inability to extend the knee or ambulate. Patella tendon ruptures generally occur at the inferior patella pole. Athletic patients may continue to play with a partial tear, but a complete rupture does not allow ambulation. Bilateral complete rupture has been described, but the condition is generally unilateral.

With either type of rupture, a large hemarthrosis is usually produced and often prompts the incorrect diagnosis of a ligamentous injury (such as an anterior cruciate ligament rupture). A palpable defect superior or inferior to the patella may be appreciated, but diffuse swelling can hide this finding (Fig. 48-33). Lack of the expected defect can be misleading in the presence of a large hemarthrosis. In cases in which the history consists of only minor trauma and the findings on physical examination are subtle, malingering or noncooperation with the examination may be incorrectly contemplated by the clinician. With complete rupture, a supine patient is unable to actively extend the knee or lift a straightened leg off the stretcher, and the knee flexes when posterior thigh support is removed from the raised leg. Weak extension, especially in the sitting position, may be possible if portions of the medial and lateral retinacula are intact, even with a complete rupture of the central rectus femoris. With complete rupture the patient cannot walk, and the knee gives way immediately. As one would intuit, however, a knee immobilizer allows the patient to apparently walk normally. Partial tears may allow the patient to walk with a peculiar forward-leaning gait that helps support the knee in extension.

Plain radiographs have normal findings except for the occasional patellar avulsion fracture. With quadriceps tendon ruptures, a low-riding patella (patella baja) may be present as the patella falls inferiorly. Conversely, a high-riding patella (patella alta) is often seen with patella tendon ruptures as the quadriceps tendon and patella retract superiorly. MRI is definitive in identifying nuances of the process. As with Achilles tendon rupture, sonography is an emerging diagnostic imaging tool used by some ED providers to assess for ruptures of the quadriceps and patella tendons.40 Partial tears of either tendon may be treated conservatively; complete tears require surgical repair, usually as soon as the diagnosis is made. Although definitive treatment is not undertaken in the ED, early diagnosis may improve the long-term outcome. A 2- to 3-week delay in diagnosis makes recovery less complete and repair more problematic. The postoperative period of recovery for the elderly is prolonged and difficult. Acute injuries diagnosed in the ED may be treated with a knee immobilizer and crutches with 1- to 2-day follow-up, but admission is often warranted to expedite definitive intervention.36

References

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3. Blaivas, M, Lyon, M, Brannam, L, et al. Water bath evaluation technique for emergency ultrasound of painful superficial structures. Am J Emerg Med. 2004;22:589.

4. Thompson, JS, Peimer, CA. Extensor tendon injuries: acute repair and late reconstruction. In: Chapman MW, ed. Chapman’s Orthopaedic Surgery. 3rd ed. Philadelphia: Lippincott, Williams & Wilkins; 2001:1485.

5. Lalonde, DH, Kozin, S. Tendon disorders of the hand. Plast Reconstr Surg. 2011;128:1e.

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