Orthopaedic Knowledge Update®: Musculoskeletal Infection 2 Print + Ebook (AAOS - American Academy of Orthopaedic Surgeons)

Section 6: Bone, Joint, and Soft-Tissue Infections

Early treatment of animal bite injuries that are infected is associated with better outcome, shorter hos pitalization, and reduced complications and the need for second-look surgeries. 69,70 Treatment of animal bites usually starts with thorough wound inspection to iden tify deep injuries and devitalized tissue; anesthesia is usually necessary for proper inspection and visualization of the bottom of the wound. 71 Copious irrigation with normal saline or antiseptic solutions is one of the most important means of infection prevention and the limb can be wrapped with a bandage for immobilization. 71,72 Although controversial, it is generally preferred to keep animal bite wounds open to reduce infection risk, except for facial wounds. 31,73 Tetanus and rabies prophylaxis should also be provided when indicated. 74 The first-line empiric antibiotic for infected animal bite wounds is amoxicillin/clavulanic acid (or ampicillin/ sulbactam if parenteral therapy is needed); then, antimi crobial therapy should be tailored to culture and sus ceptibility results if available. An effective antimicrobial treatment course is often 7 to 10 days. The total duration of therapy depends on the location and severity of the wound and the patient’s clinical response; it should be extended for 4 to 6 weeks in the presence of bone and joint infections. 66 Surgeon consultation is warranted for deep wound infections that involve bone, tendons, joints, or other major structures and compromised neurovascu lar structures. Surgical débridement should be considered for dirty wounds notably for edges and nonviable tissue, as it has been shown to be effective in preventing infec tion. 71,72 Animal bite wounds are usually at greater risk of aesthetic sequelae because of their longer inflammatory phase that causes multiple edges, bruising, and lacera tion. 75 However, searching for deeper infections such as flexor tenosynovitis, necrotizing fasciitis, septic arthritis, and osteomyelitis is warranted in cases of persistent signs of infection despite adequate initial wound care and anti biotics administration. 66,70 ABSCESS S aureus is the most common cause of abscesses. 31 However, abscesses can be polymicrobial in up to 40% of cases in people who inject drugs because pathogens are inoculated into the skin layers and can originate from the individual’s skin surface, contaminated drugs, or contaminated equipment. 76 In addition to S aureus , these include commensal organisms of the oral cavity (such as Streptococcus anginosus , other viridans group strepto cocci, and anaerobic organisms). In 2022, a retrospective study reported that in people who inject drugs, abscesses frequently occur at the antecubital fossa region, which is one of the most common injection sites and may use other injection sites throughout the body including the neck,

groin, legs, or feet. 77 Early point-of-care ultrasonography can be used to rule out abscesses in uncertain cases. 78 In some rare cases, these abscesses can contiguously spread to bone and joints and cause osteomyelitis and septic arthritis. Thus, incision and drainage, which is the primary therapeutic modality of abscess management, should be promptly performed. Pus directly drained from these lesions should be sent for Gram stain and culture testing. Blood cultures are not recommended by the Infectious Diseases Society of America in SSTIs because they have low yield, even in people who inject drugs who are febrile, and do not affect patient management significantly. 31 The authors of this chapter, however, disagree with this position and recommend obtaining blood cultures in this high-risk group for systemic complications of bacteremia; of note, a US population–based study from 2022 showed that 38% of S aureus bacteremia had SSTIs as a potential source. 79 According to the IDSA, the administration of empiric antimicrobial agents covering S aureus (including MRSA), in addition to incision and drainage, depends on the pres ence or absence of signs of systemic infection, especially fever, hypotension, and sustained tachycardia. 31,80 Patients with immunocompromising conditions or inadequate improvement with incision and drainage should receive empiric coverage for MRSA. 31 In addition, antimicrobial agents with broad-spectrum covering gram-positive cocci are recommended in people who inject drugs as they repre sent most isolated organisms. 31,76 Patients at risk for infec tive endocarditis should receive antibiotic coverage 1 hour before incision and drainage with agents covering MRSA and beta-hemolytic streptococci. Other numerous condi tions may warrant treatment with antimicrobial agents and these include size of single abscess (≥2 cm), multiple abscesses, surrounding cellulitis, major comorbidities, presence of an indwelling device (such as prosthetic joint, vascular graft, or permanent pacemaker), high risk for adverse outcomes with infective endocarditis (such as a his tory of infectious endocarditis, presence of prosthetic valve or prosthetic perivalvular material, unrepaired congenital heart defect, or valvular dysfunction in a transplanted heart), and high risk for community transmission of S aureus (such as military personnel and athletes).

Section 6: Bone, Joint, and Soft-Tissue Infections

SUMMARY Complicated SSTIs encompass an array of conditions, such as necrotizing infections, pyomyositis, animal bites, and abscesses. In addition to a course of targeted antimicrobial therapy, these infections usually require substantial surgical management including incision and drainage or débridement, often on a recurrent basis. Without securing source control and despite appropri ate antimicrobial administration, important outcomes, including need for critical care support, hospital length Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2023

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Orthopaedic Knowledge Update ® : Musculoskeletal Infection 2