Chapter 8 Orthopedic infections and other complications
Orthopedic Emergencies, ed. Michael C. Bond, Andrew D. Perron, and Michael K. Abraham. Published by Cambridge University Press. © Cambridge University Press 2013.
Septic arthritis
Key facts
Infection occurs primarily through hematogenous seeding of the joint (bacteremia)
Contiguous soft-tissue infection or direct inoculation of the joint (e.g., penetrating trauma, recent arthrocentesis or intra-articular injection) may also play a part, albeit to a lesser extent
Risk factors include age, diabetes mellitus, rheumatoid arthritis, joint surgery, prosthetic joint (hip or knee), skin infection, intravenous drug use, and alcoholism
Staphylococcus aureus and streptococcus are the primary infecting organisms seen in adults, although immunocompromised patients may also be at risk for Gram-negative infection
Disseminated Neisseria gonorrhoeae infection can present as septic arthritis and should be considered in sexually active adults
Clinical presentation
Joint pain that is worse with range of motion is a primary complaint, most commonly involving the knee or hip
Fever is often present
Examination of the affected joint may reveal:
Joint effusion with erythema, warmth, and tenderness
Painful or limited range of motion
Overlying cellulitis or pustules (seen with disseminated Neisseria gonorrhoeae infection[DGI])
Multiple joint involvement is occasionally seen, particularly with DGI or sepsis
Symptoms and examination findings may be minimal in the setting of immunosuppression
Diagnostic testing
Definitive diagnosis rests upon arthrocentesis of the affected joint, preferably before antibiotics are given
If the affected joint is a prosthetic joint, the arthocentesis should be done by an orthopedic surgeon, preferably under sterile conditions in order to prevent potential seeding of the joint
Synovial fluid should be sent for white blood cell (WBC) count with differential, Gram stain, and aerobic culture
Synovial WBC > 50,000 cells/mm3 is generally indicative of septic arthritis, but is not sensitive enough to rule it out
A differential with > 90% polymorphonuclear cells increases the likelihood of infection
Gram stain is only 50–60% sensitive for detection of bacteria in synovial fluid
If minimal synovial fluid is recovered, culture should take precedence over all other tests
Obtain blood cultures prior to administering antibiotics
Check CBC, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP)
Not helpful acutely but can be followed to ensure resolution of the disease
Consider plain radiographs of the affected joint to exclude joint destruction or associated osteomyelitis
Bedside ultrasound may aid in detecting a joint effusion and facilitating arthrocentesis
Treatment
Empiric coverage of Gram-positive organisms, including methicillin-resistant S. aureus (MRSA) is recommended pending culture and sensitivity
In immunocompromised patients, the addition of a third-generation cephalosporin should afford adequate empiric coverage of most Gram-negative bacteria
Coverage should always be narrowed once antibiotic sensitivities are known for any organisms cultured
Surgery
Orthopedic surgery consultation is advised as irrigation and operative debridement versus serial arthrocentesis of the infected joint may be necessary
Infections involving prosthetic joints often require hardware removal
Admit to the hospital
Prognosis
Timely diagnosis and treatment are the keys to reducing mortality and preventing poor functional outcomes
Complications of untreated septic arthritis can include joint destruction, osteomyelitis, suppurative disease, and sepsis
PEARL: Septic arthritis must be considered in the patient presenting with a swollen, painful joint, particularly in the absence of a preceding injury.
PEARL: An arthrocentesis for synovial fluid analysis and culture should always be performed if septic arthritis is suspected.
Infectious tenosynovitis
Key facts
Infection of the tendon sheath, often involving the flexor tendons of the hand and wrist
Typically associated with penetrating trauma (e.g., lacerations, bites, punctures, intravenous drug use)
May also result from contiguous spread of an adjacent soft-tissue infection or hematogenous spread (DG mycobacteria)
Staphylococcus aureus and streptococcal infections are the most common infecting organisms although Gram-negative bacilli may be seen with bites and in diabetics
PEARL: Infectious tenosynovitis is an orthopedic emergency that requires early consultation with a hand surgeon.
Clinical presentation
Kanavel’s four cardinal signs of flexor tenosynovitis include:
Pain with passive extension of the finger
Semi-flexed position of the finger at rest
Symmetric swelling of the finger (sausage digit)
Tenderness to percussion over the tendon sheath
Localized erythema, lymphangitic streaking, and fever may be present
Subcutaneous purulence (secondary to tendon sheath rupture) and digital ischemia signal advanced infection
Vesiculopustular lesions and polyarthralgias may accompany gonococcal tenosynovitis
PEARL: Pain with passive extension of the finger is often the earliest of Kanavel’s cardinal signs to appear.
Diagnostic testing
Check CBC
Definitive diagnosis requires Gram stain and culture of tendon sheath fluid by aspiration or during surgical intervention by a hand surgeon
Plain radiographs may be helpful in identifying associated fractures and foreign bodies
Treatment
Empiric coverage of Staphylococcus aureus (including MRSA), streptococcus, and Gram-negative bacilli can be achieved with:
In combination with one of the following:
If a human or animal bite is involved and MRSA is not a primary concern, consider:
Coverage should always be narrowed once antibiotic sensitivities are known for any organisms cultured
Early and mild cases may occasionally be managed with antibiotics, splinting, elevation, and close observation
Surgery
Hand surgery consultation should always be sought to determine if operative drainage and debridement is warranted
In severe cases, amputation may be required
Administer tetanus prophylaxis if indicated
Admit to hospital
Clenched fist injuries
Key facts
Commonly referred to as a “fight bite”
Associated with wounds over the dorsum of a metacarpophalangeal (MCP) or proximal interphalangeal (PIP) joint sustained after striking an opponent’s teeth with a clenched fist
Classically involves the third or fourth MCP joint of the dominant hand
May result in damage to and contamination of the extensor tendon, tendon sheath, and/or joint capsule with human oral flora
Bacteria inoculated into the wound may travel proximally into the dorsal hand upon relaxation of the extensor tendon and unclenching of the fist
Infection can range from cellulitis to septic arthritis and soft tissue infections involving the deep spaces of the hand
Common infecting organisms include Staphylococcus aureus, streptococcus, corynebacterium, Eikenella corrodens, and anaerobic bacteria
Clinical presentation
Examination of the affected MCP or PIP joint shortly after the injury may reveal deceivingly small lacerations
Erythema, swelling, purulent wound discharge, and decreased range of motion developing several days after a clenched fist injury signal infection
Diagnostic testing
Gram stain and culture (aerobic and anaerobic) should be obtained from infected wounds along with blood cultures prior to administering antibiotics
Plain radiographs of the hand may reveal concomitant fractures or foreign bodies (e.g., tooth fragments) after the initial injury, or osteomyelitis in delayed presentations with infection
Treatment
Initial care of the uninfected fight bite
Extensor tendon injury and joint capsule involvement may require hand surgery consultation and should be carefully investigated by examining the wound with fingers flexed in a closed fist
If surgical consultation is not indicated, the wound should be thoroughly irrigated and allowed to heal by secondary intention
Antibiotic prophylaxis should consist of amoxicillin–clavulanate for 3 to 5 days
Administer tetanus prophylaxis if indicated
The wound should be re-evaluated by a healthcare provider within 24–48 hours
PEARL: Antibiotic prophylaxis is always indicated after a clenched fist injury given the high risk of infection.
Management of the infected fight bite
Empiric regimens include:
Ampicillin–sulbactam 3 g IV every 6 hours
Ceftriaxone 2 g IV once daily + metronidazole 500 mg IV/PO every 8 hours
Coverage should always be narrowed once antibiotic sensitivities are known for any organisms cultured
Surgery
Administer tetanus prophylaxis if indicated
Admit to the hospital
Osteomyelitis
Key facts
Infection of bone can result from hematogenous seeding (bacteremia), contiguous spread of an adjacent infection (e.g., cellulitis, abscess, infected ulcer), or direct inoculation (e.g., open fracture, orthopedic surgery)
Risk factors include diabetes mellitus, peripheral vascular disease, sickle cell disease, chronic corticosteroid use, immunosuppressed states (including HIV), joint disease, history of open fracture or orthopedic hardware, intravenous drug use, and alcoholism
Staphylococcus aureus, coagulase-negative staphylococci, and Gram-negative bacilli (including Pseudomonas aeruginosa) are commonly implicated organisms
Clinical presentation
Acute osteomyelitis is marked by localized pain, erythema, and swelling for several days with or without fever or malaise
Chronic osteomyelitis develops over a longer period of time and is more likely to present solely with non-specific symptoms
Examination of the affected site may reveal:
Erythema, warmth, swelling, and tenderness to palpation
Limited or painful range of motion of an adjacent joint
Draining sinus tract (chronic osteomyelitis)
Non-healing ulcer (chronic osteomyelitis)
Ulcer area > 2 cm2 and probing to bone within a diabetic foot ulcer are highly predictive of osteomyelitis
PEARL: Normal plain radiographs do not rule out osteomyelitis.
Diagnostic testing
Check CBC, ESR, and C-reactive protein
Obtain blood cultures prior to administering antibiotics
Superficial wound or sinus tract cultures are of limited use as they may not accurately reflect the organisms responsible for infection of the bone
Definitive diagnosis rests upon bone biopsy and culture
Consider discussing with orthopedics or admitting service on holding off on antibiotics until a bone biopsy or culture can be obtained
If septic, antibiotics should be started immediately after blood cultures are obtained
Plain radiography of the affected bone may reveal periosteal elevation or cortical bone destruction
Radiographic changes may not be evident within the first few days to weeks after onset of symptoms
MRI is highly sensitive and specific for detecting bone marrow edema, cortical destruction, soft-tissue infection (cellulitis, abscess), and sinus tracts, even in early disease
CT can be helpful in identifying cortical destruction when MRI is not possible
PEARL: MRI can be extremely useful in making the early diagnosis of osteomyelitis.
Treatment
In the absence of sepsis, neutropenia, or other critical illness, it is reasonable to briefly delay antibiotics in order to improve yield and better guide therapy if a bone biopsy and culture can be obtained in a timely manner
Empiric coverage of Gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA) is recommended pending culture and sensitivity:
Gram-negative coverage is also warranted with the addition of one of the following:
Coverage should always be narrowed once antibiotic sensitivities are known for any organisms cultured
Infectious disease consultation is recommended as prolonged antibiotic therapy (typically 6 weeks) is needed
Surgery
Orthopedic surgery consultation is advised as operative debridement of infected or necrotic bone and removal of infected prosthetic hardware may be necessary
Admit to hospital
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