Chapter 44: Leg and Foot Lacerations

Lower extremity injuries most frequently involve the lower leg and ankle, followed by the foot and toes, hip, and then knee.¹ Lacerations and wounds occur from sports and recreational activity,^{2,3,4,5,6,7,8} tools and equipment,^9,10,11 occupational activity,¹² and explosions.¹³

In the foot, the plantar epidermis and dermis are thick, except in the arch area. This thick skin is able to withstand the force produced by a moving body but is also quite sensitive to two-point discrimination and pressure. The heel has an 18-mm-thick modified pad of fat separated into chambers by fibrous septae. There is an additional broad internal fibrous arch, called the inner cup ligament, which helps maintain the shape of the heel. The skin of the sole readily hypertrophies and can become quite thickened, especially in people who walk barefoot. The dense fibrous fatty tissue of the ball of the foot and heel makes wound exploration and visualization difficult in the ED.

In contrast to the protective plantar surface, skin on the dorsal aspect of the foot and the entire ankle provides little protection for underlying tendons, nerves, and blood vessels. The dorsum of the foot, the ankle, and the pretibial surface are particularly vulnerable to blunt-force injuries. Most lacerations on the dorsal foot and in the ankle area are easily explored, except for posterior ankle lacerations, a limitation when partial laceration of the Achilles tendon is considered. Lacerations involving the shin, calf, and thigh usually present few problems regarding wound exploration and visualization.

Several important tendons in the leg are at risk for injury. The fibularis longus and fibularis brevis (also known as the peroneus longus and peroneus brevis) tendons, which contribute to foot plantar flexion and eversion, run behind the lateral malleolus and can be lacerated at this location (Figure 44-1). The extensor hallucis longus tendon, which extends the first toe, runs along the top of the first metatarsal and may be injured when heavy objects are dropped on the foot. The Achilles tendon, the primary contributor to foot plantar flexion, may be severed by penetrating injuries to the posterior ankle. Lacerations of the shin rarely involve vital nerves or tendons. Infrapatellar lacerations can transect the patellar tendon, resulting in inability to extend the leg. Suprapatellar lacerations may involve the quadriceps tendon, also resulting in impaired knee extension.

Sensory nerves predominate in the foot, with most motor control of the foot being performed by nerves and muscles in the lower leg (Figures 44-2 and 44-3). The exceptions to this generalization are that the posterior tibial nerve innervates the intrinsic foot musculature, and the deep peroneal nerve innervates the extensor digitorum brevis and extensor hallucis brevis muscles; injuries to these nerves may result in toe clawing.¹⁴ The common peroneal nerve can be injured in complex fractures, sharp injuries, or lacerations of the lower extremity resulting in foot drop (Figure 44-4).¹⁵

Arterial injury resulting from penetrating and blast wounds most commonly affects the superficial femoral, popliteal, crural, common femoral, and deep femoral arteries (Figure 44-5).¹⁶ Arterial injuries are at high risk for limb loss.¹⁷

HISTORY

Obtain a description of the mechanism of injury, assessing the potential for damage to underlying tissue, the risk of a retained foreign body, and degree of potential contamination. Determine the time interval from injury to evaluation, because delayed presentations can increase the incidence of infection. Inquire about foreign body sensation, paresthesias, anesthesia, weakness, or loss of function suggesting a nerve, vascular, or tendon injury.

The patient's age influences wound healing and functional status following the injury. Ask about tetanus immunization status and conditions that increase the risk for infection or delayed wound healing such as diabetes, immunosuppression, or vascular disease. Note the social history, because patients who smoke, consume alcohol, or use illicit substances may be at additional risk of poor healing secondary to vascular disease.

PHYSICAL EXAMINATION

Inspect the wound, noting its location and proximity to underlying nerves or arteries. General appearance, obvious injuries, or visible foreign bodies should be noted; more detailed wound exploration typically waits until after anesthesia and radiographs, if needed. If a nerve laceration is suspected, light touch and/or static two-point discrimination should be tested in the foot and toes and compared with the uninjured side. Two-point discrimination varies in the foot, with normal values of 1.5 cm in the hind, mid, and forefoot, and <1 cm in the big toe, but these measures are not reliable in patients with diabetes or peripheral vascular disease.¹⁸ Sensory deficits to the foot can result in significant long-term morbidity. Motor function may be easier to assess after anesthesia or reduction of an associated fracture or dislocation. Obtain prompt surgical consultation if motor nerve or major sensory nerve injury is identified because primary repair may be indicated.¹⁴ Nerve injuries caused by open blunt injuries are not typically repaired at the time of injury, in part because of the risk of infection and in part because of the possibility that a contused nerve will regain function without surgical intervention.

Evaluate for tendon injuries by assessing motor function, palpating the tendon, and observing the tendon through its entire range of motion. A partially injured tendon may be noted to "catch" on the synovial sheath during range of motion. Lacerations of the Achilles tendon may be easily visualized with simple exploration through the open wound, by palpating a defect in the tendon, or by US. Sometimes, the tendon laceration may not be visible or palpable, and presence of active plantar flexion of the foot cannot be used to exclude the injury. The Achilles tendon is not the only structure responsible for plantar flexion of the foot—the tibialis posterior muscle flexes the foot at the ankle. The Thompson test can assist in detecting an Achilles tendon rupture. The patient lies prone on the examination cart with the feet hanging over the edge of the bed, and the examiner places one hand on each mid-calf (Figure 44-6). If the Achilles tendon is intact, the foot plantar flexes when the calf is squeezed, and comparison with the unaffected side is helpful to detect subtle movement. A positive Thompson test is when the affected foot does not flex, indicative of an Achilles tendon rupture.¹⁹

Document the location, length, estimated depth, and general shape of the wound. Provide anesthesia, cleanse the wound, and carefully inspect the full extent of the wound for foreign bodies. The loose, thin skin over the dorsum of the foot allows for adequate visual, digital, and instrument exploration for tendon lacerations, as well as for foreign body discovery. The dense tissue of the plantar surface of the foot limits wound visualization, and the risk of creating further injury limits exploration. An exception to this general rule of limited exploration on the weight-bearing plantar surface is in an infected wound with suspected foreign body. With significant injury to the leg, like a crush injury, consider compartment syndrome and evaluate accordingly.

Obtain radiographs when a fracture, radiopaque foreign body, or joint penetration is suspected.^20,21 Foregoing radiographs and using wound exploration alone to exclude a foreign body is a reasonable approach, but carries a small risk of missing a retained object.^22,23,24 CT or MRI can detect retained organic material. Bedside US may identify retained foreign bodies and detect tendon lacerations and fractures (see chapter 45, "Soft Tissue Foreign Bodies"). Fluoroscopy is a useful dynamic imaging modality that may assist in identifying and removing foreign bodies. No single imaging modality or wound exploration will identify every foreign body; emphasize close follow-up if the mechanism of injury suggests a potential for a foreign body but none was identified on imaging or wound exploration.

Lacerations in proximity to joint spaces may penetrate the articular space. Detecting joint penetration by physical examination alone is often difficult. Intra-articular gas on plain radiograph is a sign of joint penetration. If the radiograph does not display intra-articular gas, use the saline load test to determine joint integrity, especially in the knee and ankle.^25,26 Inject sufficient amounts of saline to adequately stress the capsule, because false-negative results may be obtained if too little fluid is injected.^27,28 Volumes injected into the knee may vary based on the location of the approach; mean volumes of injected fluid needed for a positive result are approximately 65 mL and 95 mL, respectively, at the inferomedial and superomedial locations.^26,27,28 Fluid leaking from the wound indicates joint penetration. Do not add methylene blue to the injected saline to aid in visualization of fluid existing in the wound because it does not increase diagnostic accuracy compared to saline alone and the resultant staining of the articular surfaces may affect operative management of intra-articular injuries.²⁹

ANESTHESIA

Anesthesia can be administered by topical, local, or regional routes. The toes can be anesthetized using standard digital blocks. Epinephrine-containing local anesthetics can be safely used for digital blocks in toes (see chapter 36, "Local and Regional Anesthesia").

Lacerations to the dorsum of the foot can be sufficiently anesthetized by infiltration of local anesthetic. The plantar surface of the foot is sensitive to the infiltration of a local anesthetic, so regional nerve blocks may be helpful. The sural nerve block and the posterior tibial nerve block (see chapter 36) are the two most commonly used nerve blocks for the foot. Topical local anesthetic preparations can achieve adequate anesthesia on the dorsum of the foot and leg, but may be ineffective on the dense epidermis of the plantar surface of the foot. In children, distraction techniques, use of child-life specialists, anxiolytics, and conscious sedation may help alleviate anxiety and pain response (see chapter 113, "Pain Management and Procedural Sedation in Infants and Children").

WOUND PREPARATION

Wound irrigation with copious amounts of saline is recommended due to the increased risk of infection with lower extremity lacerations (see chapter 40, "Wound Preparation").^30,31,32 Debridement to remove devitalized tissue is an important aspect of wound care to reduce the risk of wound complications, but debridement should be limited on the plantar surface of the foot or on the shin because skin in those areas is not pliable enough to be stretched and cover a defect. Any opening resulting from debridement would then require repair under tension across the laceration.

A "golden period" of 6 hours for laceration repair with the lowest risk of infection is not substantiated by published evidence.^32,33,34 Repair of clean-appearing wounds without visible contamination presenting after 6 hours is acceptable if primary closure is felt beneficial. Otherwise, consider delayed primary closure in cases of delayed presentation or heavy contamination (see chapter 41 "Wound Closure").

WOUND CLOSURE

Wound location, size, and shape guide the decision to close with adhesive strips, sutures, or staples. Staples are acceptable for linear lacerations through the dermis as long as the wound is sharp with straight and accurately aligned wound edges, minimizing the potential for scar formation. Most foot and leg lacerations do not have these characteristics, so using staples will often result in less aesthetic wound healing.³¹ Staples should not be used on the foot because they are uncomfortable when attempting to walk during recovery. Lacerations of the lower extremity can be under increased wound tension compared with other anatomic sites, so these lacerations are frequently repaired using techniques such as multiple-layered closure or horizontal mattress closure.

DIGITAL LACERATIONS

Digital lacerations frequently require special attention. Nail bed injuries often accompany digital fractures. Clinical signs such as bleeding from the eponychium and a laceration proximal to the nail bed suggest a possible open fracture.³⁵ Nail bed lacerations place the underlying bone at risk for bacterial contamination because the skin is directly attached to the periosteum with no intervening layer of subcutaneous tissue. Missed open fractures have resulted in osteomyelitis and growth delay of the digit in children. Consider removal of the nail to evaluate for nail bed laceration if a subungual hematoma occupies a large portion of the nail plate or if there is disruption of the nail or nail folds.³⁶ Repair the nail bed with either absorbable sutures or tissue adhesives.³⁷ Nail bed lacerations are considered to be open fractures of the distal phalanx, so prophylactic antibiotics are recommended.³⁵ Conversely, simple nail trephination is adequate for drainage of subungual hematomas without nail or nail fold deformities.

Tendon injuries of the digits may require consultation, especially when the extensor hallucis longus is involved, because injury to this tendon impairs functionality during the swing phase of the gait cycle. Surgery is often recommended for patients with extensor hallucis longus tendon lacerations, and grafting may be needed.^38,39

INTERDIGITAL LACERATIONS

Lacerations between the toes are difficult to repair because the confined interdigital space is difficult to access for suturing. An assistant gently separating the toes enhances the exploration and repair of interdigital lacerations. Simple interrupted sutures often lead to skin inversion and risk of failure of the initial wound repair with interdigital lacerations. The more effective closure technique, albeit somewhat more difficult to perform, is to place horizontal or vertical mattress sutures. Use 5-0 monofilament nonabsorbable sutures on a small cutting needle. Use monofilament absorbable sutures in young children, thus avoiding suture removal. When a web space laceration involves the neurovascular bundle, the skin is usually closed without attempting to repair the neurovascular injury, followed by subsequent referral to a specialist.

HAIR-THREAD TOURNIQUET SYNDROME

Hair-thread tourniquet syndrome, also referred to as acquired constriction ring syndrome, is an unusual type of toe injury usually seen during infancy⁴⁰ and rarely seen in older children.⁴¹ A long strand of hair or thread becomes wrapped around a toe, often producing strangulation and digital ischemia. This can be an occult source of irritability for infants.⁴⁰ Complete removal is required to restore perfusion and allow skin healing. Two standard approaches to salvage the compromised digit are to either unwind the hair or thread if possible or, otherwise, make a midline longitudinal incision along the extensor surface of the toe to cut the hair or thread.⁴² To cut the hair, it will often be necessary to split the fibers of the extensor ligament, but avoid transecting the fibers. The multiple strands of hair or thread are then removed using fine forceps without teeth. The toe often retains the initial appearance, making the physician uncertain whether all of the strands have been removed or cut. A novel but unvalidated method is to apply hair-dissolving compounds.⁴³ Hair-thread tourniquet syndrome can cause deep cutaneous lacerations that result in tendon lacerations requiring operative repair.⁴⁴ Hair-thread tourniquet syndrome is not the result of intentional injury and does not warrant reporting as suspected child abuse.⁴⁵

PLANTAR FOOT LACERATIONS

Repairing a laceration on the plantar surface is best done with the patient placed in a prone position, with the foot overhanging the cart or elevated by placing a pillow beneath the ankle. A large suture needle with thick thread is required to penetrate the hypertrophied epidermis and dermis of the sole of the foot. If there is tissue loss or the site is under tension, vertical mattress sutures may be required. In the arch area, achieving tissue eversion can be difficult. Do not use adhesive tapes, tissue adhesives, and staples on the plantar surface. Small or superficial wounds to the plantar surface typically heal rapidly without sutures. Repair small plantar lacerations if the wound gapes open or there is a risk for infection.

DORSAL FOOT AND ANKLE LACERATIONS

Dorsal surface lacerations are repaired almost exclusively with nonabsorbable, monofilament suture material, most commonly 4-0 or 5-0 for small lacerations. Use careful technique suturing the skin to avoid vessels, nerves, and tendons that lie just under the surface. Deep sutures are not recommended for the same reason. Running sutures are acceptable on the dorsal surface, and smaller lacerations may be closed with adhesive tapes or tissue adhesives. For lacerations under tension, consider applying a splint to restrict movement, allowing for healing during the first 5 to 7 days.

The decision to repair tendon lacerations in the foot depends on the functional impairment caused by the injury compared with the benefits of repair. Many extensor tendon lacerations involving the mid-foot and forefoot can go unrepaired without compromising foot function. The skin is closed and the foot splinted, leaving the injured tendon alone. Lacerations of the extensor hallucis longus or tibialis anterior require consultation with an orthopedist or podiatrist because dorsiflexion of the great toe and foot are important in walking and running.^39,46 Closure without tendon suturing and with immediate mobilization is acceptable in patients with partial lacerations of the extensor hallucis longus tendon.³⁹

Flexor tendon lacerations across the toes (excluding the great toe) can usually be left unrepaired without significant functional sequelae, but occasionally a hammer toe or claw toe deformity develops. Lacerations of the flexor hallucis longus are frequently repaired, although long-term benefit is unproven, even in athletes.⁴⁶

PRETIBIAL LACERATIONS

Managing pretibial skin lacerations, especially in the elderly patient with comorbidities, is challenging. These wounds often occur on the distal third of the pretibial region, which is poorly vascularized and slow to heal. Pretibial wounds are approached according to the type and severity (Table 44-1).^47,48

Wounds where the edges can be approximated without tension can be closed with adhesive tapes or simple sutures. Wounds with tension can be closed using horizontal mattress sutures with 4-0 nonabsorbable sutures. Occasionally, the 4-0 suture is too fine and cuts through the skin, so use 3-0 sutures. The natural contraction of the thin skin makes closure more difficult because sutures often cut through the fragile skin when attempting to approximate the wound edges. A technique to overcome this problem is to re-enforce the wound edges with adhesive tape applied along the edges before closure with placement of percutaneous sutures penetrating through the adhesive tape.^49,50,51 Additionally, to minimize tension across the wound, tincture of benzoin can be applied over the sutures, and then broad adhesive tape strips (1/2 in.) can be placed over the sutures to minimize tension across the wound. Alternatively, the wound edges can be held in place by adhesive strips perpendicular to the wound, with sutures placed through the strips, thereby removing the shear force of the strip on the skin.

Flap lacerations with significant skin loss are best repaired with primary excision and skin grafting.^48,52 Apply a foam adhesive dressing (such as 3M^™ Tegaderm^™; 3M, St. Paul, MN) to absorb exudate and reduce healing time.⁵³ Patients should remain ambulatory during the healing of pretibial injuries, even after skin grafting.⁵⁴ Protecting the repair from the tension created by foot plantarflexion is useful; consider using a lightweight plastic ankle-foot orthosis.⁵⁵

KNEE LACERATIONS

Close simple lacerations in the knee area with 4-0 nonabsorbable sutures, using interrupted or horizontal mattress sutures because of the marked active skin tension in this area. As already noted, assess for joint capsule penetration and laceration of the patellar and quadriceps tendons. The common peroneal nerve is prone to injury as it runs over the head of the fibula laterally, so distal limb motor function should be assessed (foot eversion and dorsiflexion). Deep popliteal wounds can injure the popliteal artery and tibial nerve. Popliteal artery injuries typically require emergent repair because, in most individuals, there is minimal collateral circulation at the level of the knee (Figure 44-5).

The knee should be splinted or placed in a knee immobilizer to decrease active tension and promote better wound healing. Knee area lacerations in children can be closed with tissue adhesives and splints to restrict movement.

PROXIMAL LOWER EXTREMITY LACERATIONS

Proximal lower extremity lacerations are usually straightforward, and thickness of the soft tissue layers helps to prevent injury to vital structures. Lacerations to the proximal lower extremity also have less tension on them, allowing for easier exploration, debridement, and repair. Assess lacerations to the proximal femoral area for injuries to the femoral artery, vein, and nerve. Although acute traumatic femoral artery injuries are uncommon, they are associated with a high incidence of limb loss and morbidity.¹⁷

Most patients with lower extremity lacerations will be able to go home after ED evaluation and treatment. Patients at high risk for compartment syndrome, those with limited mobility and inadequate home assistance, and patients requiring operative repair should be admitted. Patients may require ancillary devices such as crutches, walkers, and wheelchairs. Elevation of the extremity decreases swelling and infection risk. Sutures are typically removed in 10 to 14 days.

Significant tendon lacerations of the lower extremity are usually repaired a few days to weeks after the initial injury. Treatment in the ED consists of skin closure; splinting of the foot, ankle, and leg; initiation of prophylactic antibiotics; instruction for non–weight-bearing crutch use; and arrangement for the patient to follow up with an orthopedist or podiatrist.

AGE CONSIDERATIONS

The preverbal child may have particular difficulty limiting movement of the injured extremity and is more likely to contaminate the wound. Generous dressings aid in protecting any lower extremity laceration; the general rule is "the smaller the child, the larger the dressing."

Elderly patients tend to have thin skin and decreased subcutaneous fat, especially over the pretibial surface, making wound edges more difficult to appose, resulting in closure under tension. Additionally, fragile skin in elderly patients predisposes sutures to tear through the skin. Adhesive tapes may be needed to reinforce the closure. Elderly patients are more likely to have medical conditions that can delay wound healing and are less likely to be adequately immunized against tetanus. Assess for fall risk and the ability to perform daily tasks after repair and immobilization of the injured leg.

AMPUTATION

Reimplantation of a severed toe is not typically performed. Reattachment of an amputated great toe, forefoot, or entire foot is occasionally done, although it is extremely complex. Immediate consultation with a reimplantation surgeon is essential in such circumstances. Any severed part should be gently washed (not scrubbed) with sterile saline to remove gross debris, wrapped in saline-soaked gauze, and placed in a plastic bag that is then closed and placed in an ice water bath.

RETAINED FOREIGN BODIES

Retained (nonreactive) foreign bodies, such as glass, can pose a problem. Chronic pain, especially during walking, can occur if the material is not removed. In the absence of chronic discomfort, inert foreign bodies can remain in the foot, where they typically become encapsulated without causing injury or infection. Conversely, reactive organic material does not become encapsulated and does promote infection. Therefore, reactive organic material should be aggressively identified and removed. Fluoroscopy may be useful to help locate and remove radiopaque foreign bodies. Deep foreign bodies in the foot can be extremely difficult to remove in the ED, and such cases are best referred to the surgeon for location and removal in the operating room.

PROPHYLACTIC ANTIBIOTICS

Although infection occurs in 3% to 8% of lower extremity lacerations, and up to 34% of plantar lacerations, there is no evidence to support routine antibiotic prophylaxis in uncomplicated lacerations (see chapter 47, "Postrepair Wound Care"). However, use prophylactic antibiotics for complicated lacerations in the setting of bites, open fractures, tendon or joint involvement, presence of foreign debris, and obvious infections.⁵⁶ Diabetes and other predisposing medical conditions, wound contamination, and laceration length greater than 5 cm are factors that predispose to wound infection.³²

Similar to wound infections in other parts of the body, most lower extremity wound infections are due to either Staphylococcus and/or Streptococcus species. Animal bites to the leg and foot require coverage against Staphylococcus, Streptococcus, and Pasteurella. Asplenic or immunocompromised patients who sustain a dog bite should receive coverage against Capnocytophaga canimorsus. Amoxicillin-clavulanate will cover all four organisms

The most common organisms causing soft tissue infections in plantar puncture wounds are Staphylococcus and Streptococcus. Pseudomonas aeruginosa is a frequent cause of osteomyelitis and osteochondritis when the puncture occurs through the sole of a shoe.⁵⁷ Open fractures should receive antibiotic prophylaxis. Consensus practice guidelines typically recommend coverage for gram-positive organisms for grade I and II open fractures, with added coverage for grade III injuries.⁵⁸

Acknowledgment: The authors gratefully acknowledge the contributions of Timothy F. Platts-Mills and the authors of this chapter in the previous editions.