Scalp Laceration

Etiology

Lacerations typically result from blunt trauma, causing a tear in the skin and underlying tissue. Examples of cases in which scalp laceration occurs range from injuries caused by falls, hammer blows, or bottles to severe blast-related trauma in war zones. Knowing the etiology and mechanism of the injury is vital in evaluating patients with scalp lacerations to anticipate and look for associated injuries and their possible complications.[1][2]

Epidemiology

A study conducted in US emergency departments looking at the frequency and trends of lacerations between 1992 and 2002 found that lacerations represent 8% of cases encountered in emergency departments, with 28% being in the face. Roughly two-thirds of the patients presenting with lacerations were male. Facial lacerations were more common in children. However, even though the number of patients visiting emergency departments has gradually increased, visits for lacerations have declined over the same period.[3]

Pathophysiology

The scalp consists of 5 layers, summarized by the mnemonic SCALP:

• S - Skin
• C - Subcutaneous tissue
• A - Aponeurosis and muscle (musculoaponeurotic layer ML).
• L - Loose areolar tissue and subgaleal fascia
• P - Pericranium/Periosteum

In lacerations, separation most commonly occurs at the loose areolar tissue layer. The musculoaponeurotic layer contains the superficial temporal artery, as the muscles require a copious blood supply for function. Understanding the layers of the scalp and the blood supply is essential to successfully stopping bleeding from lacerations, which can be substantial in many cases.[1][4]

History and Physical

History

Clinicians should inquire about causative trauma, the age of the wound, the presence of a foreign body, and symptoms of head trauma. They also need to assess the risk of wound contamination (eg, bite wounds are high risk). Further, the clinician should collect information on conditions and habits that may adversely affect wound healing, such as diabetes mellitus, a history of keloids, steroid use, and drug or alcohol abuse. Other important factors needed from the history include allergies to local anesthetics and tetanus immunization status. 

Examination

The wound should be assessed for length, depth, shape, contamination of foreign bodies, and skin loss.[5] Proper evaluation requires removing foreign bodies and achieving hemostasis. Sometimes, scalp hair removal is necessary. Careful examination of the head and looking for signs of associated injuries such as skull fractures and intracranial injury is essential, as they may require immediate intervention to prevent significant morbidity.

Evaluation

Diagnostic imaging is not necessary in all cases of scalp lacerations. However, there are some indications:

• Bony defects on examination or signs of traumatic brain injury warrant CT imaging to look for intracranial injury.
• Patients with clinical findings suggest foreign body presence warrants imaging (radiography for radiopaque materials such as glass, rocks, and metals, and ultrasonography for nonradiopaque materials).[6][7] 

Treatment / Management

The first thing requiring attention in scalp lacerations is removing foreign bodies, if present, and achieving hemostasis. The bleeding can usually be stopped by applying direct pressure with or without local lidocaine with epinephrine. If hemostasis is unachievable with these measures, the edges of the scalp are everted using hemostats or skin hooks before prompt wound suturing. Controlling bleeding is important, as lacerations can result in significant blood loss.[4][8] Primary closure of the laceration is preferred in most cases, as delayed closure of the wound increases the risk of infection and scarring. Lacerations older than 24 hours with an increased risk of infection (eg, vascular insufficiency, contamination, foreign bodies) may warrant delayed primary closure 4 to 5 days after wound cleansing and debriding. Primary closure of wounds that look inflamed (warm, swollen, pussy, and red) is contraindicated.[9](B3)

The closure of the laceration mustn't hinder definitive care and evaluation of more urgent injuries with which it is associated, such as intracranial injury.[10] Options for closure include surgical staples, hair apposition, and suturing. Staples are generally the preferred closure method in lacerations through the dermis, where bleeding is under control, as they are fast, cheap, and have few complications. They also achieve similar cosmetic results when compared to sutures.[11][12] Straight, small wounds (under 10cm) can be repaired using modified hair apposition if adequate bleeding is controlled and the patient has hair that is at least 1cm long. Even though this method is relatively time-consuming compared to surgical staples, it is less painful, does not necessitate staple removal, and usually results in good cosmetic results with few complications.[13][14][15] Simple interrupted sutures may be used for closure if the wound is profusely bleeding and cannot attain adequate hemorrhage control without suturing. It is also a valid option if staples are unavailable and hair apposition isn't applicable (eg, a large wound or a short-haired patient).[16](A1)

Differential Diagnosis

Differential diagnosis for scalp lacerations include the following:

• Bite wound
• Complex laceration.
• Cut wound by a sharp object
• Intracranial injury
• Retained foreign body
• Skull fracture

Prognosis

Most scalp lacerations unassociated with other traumatic injuries have a good prognosis with little to no long-lasting sequelae and excellent cosmetic results.[11] Wound infections are relatively uncommon due to the excellent blood supply to the scalp area. The risk of bleeding is significant but generally is controllable fairly easily. Factors that may cause poor outcomes include associated facial trauma, chronic conditions that may impair healing (eg, diabetes, vascular insufficiency), and contaminated wounds with retained foreign bodies.

Complications

Complications of scalp lacerations are as follows:

• Bleeding: due to the excellent blood supply to the scalp, lacerations may result in profuse bleeding that may even lead to hemorrhagic shock if not managed promptly.[1]
• Infection: contaminated wounds, bite wounds, and retained foreign bodies pose a higher risk of wound infection.
• Scarring: poor healing outcomes may be related to delayed intervention or patient-related factors such as chronic medical conditions, social habits (smoking, alcohol), and history of keloids.