Septic arthritis in orthopaedics

1. Septic Arthritis

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Introduction:
• Septic arthritis is inflammation of a
synovial membrane with purulent
effusion into the joint capsule, usually
due to bacterial infection.
• This disease entity also is referred to
as
• bacterial,
• suppurative,
• purulent, or
• infectious arthritis.

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• Septic arthritis is a rather rare but
important disease
• typically affects monoarticular joints
• The age range affected is broad
– from the neonatal period to advanced age

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• Septic arthritis usually is divided into
– Gonococcal
– Nongonococcal
• as clinical and treatment regimens differ.
• In adults, septic arthritis most
commonly affects the knee
• in children, infection into the hip joint
predominates.

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• Despite advances in diagnostic studies,
powerful antibiotics, and early drainage,
significant joint destruction commonly
occurs.

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• Barriers to successful management include
– lack of clinical suspicion in the early phase of
presentation
– delay in definitive diagnostic needle aspiration
– failure to provide adequate drainage of the
joint.
• septic arthritis in neonates and infants can
be especially treacherous due to:
– blunted inflammatory signals
– confounding infection at a distant site (eg, ear,
umbilical catheter site).

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• Frequency:
– Of all the forms of arthritis, septic arthritis is
the most aggressive at destroying joints.
– The frequency of septic arthritis is
approximately 2-10 cases per 100,000 in the
general population.
• In patients with immunologic disorders (eg,
rheumatoid arthritis, systemic lupus erythematosus),
– Occurrence is approximately 30-70 cases per
100,000.
• The incidence in patients with joint
prosthesis is similar to that of patients with
immunologic disorders

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• Women are approximately 3x as likely as
men to develop gonococcal arthritis
• The knee accounts for approximately 40-
50% of infections, and the hip accounts for
20-25% of infections.
– in infants and very young children, hip
involvement is the most common
• Shoulders, ankles, and elbows account for
approximately 10-15% of infections.
• Septic arthritis of the wrist occurs in 10%
of cases.

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• Etiology:
–Most septic arthritis cases are caused
by Staphylococcus aureus and
streptococci.
–In all age groups, 80% of cases are
caused by gram-positive aerobes (60%
S aureus; 15% beta-hemolytic
streptococci; 5% Streptococcus
pneumoniae)
–Approximately 20% of cases are caused
by gram-negative anaerobes.

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• Neonates and infants younger than 6
months
– S aureus and gram-negative anaerobes
comprise the majority of infections.
– The incidence of Haemophilus influenzae has
dramatically decreased due to widespread
use of the vaccine.
• Children aged 6 months to 2 years major
organisms of infection are:
– S aureus
– H influenzae

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• In patients older than 2 years, S aureus
becomes the principle culprit.
• During the teen years, Neisseria
gonorrhoeae should be suspected as
sexual activities begin

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Pathophysiology:
• Bacteria may reach the joint
– Directly as with trauma.
– Hematogenously (eg, intravenous injections).
– Osteomyelitis occuring adjacent to the joint
capsule.
– Extension from soft tissue infections eg
• Cellulitis
• Abscess
• Bursitis
• Tenosynovitis

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Clinical presentation:
• Typically, the patient presents with:
– Fever
– An inflammed joint (hot, red, painful,
distended)
– markedly decreased in joint rom.
• Active and passive movements are restricted.
• In young sexually active patients
presenting with fever, tenosynovitis,
migratory polyarthralgia, and dermatitis -
suspect a gonoccocal infection.

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Diagnosis in neonates and children can be
difficult!
– Symptoms like fever, loss of appetite, and irritability without
obvious joint involvement can lead to an incorrect diagnosis
• Inflammatory signs may be blunted
children
– Searching for distant infections is very
important
– Pseudo-paralysis may be the presenting sign
in children

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• Distinguish transient synovitis from septic
arthritis:
– Use of 4 independent variables found useful
as clinical predictors for septic arthritis:
• History of fever
• Non-weight bearing
• Erythrocyte sedimentation higher than 40 mm/h
• WBC count higher than 12,000/L

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Investigations:
• CBC with differential –
– Often reveals leukocytosis
• Erythrocyte sedimentation rate
• C-reactive protein –
– Helpful in monitoring treatment course
• Blood cultures
– May be positive in up to 50% of S aureus
infections
– Very poor in detecting N gonorrhoeae
(Approximately 10% of cases prove positive.)

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• Urethral, cervical, pharyngeal, and
rectal cultures
–Much higher yield for N gonorrhoeae
than in blood cultures
• Synovial fluid analysis
• Gram stain
• Culture
• Cell counts
• Crystal analysis

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• Synovial fluid culture results:
– positive in 85-95% of non-gonococcal
arthritis cases
– Approximately 25% in gonococcal arthritis
cases.
• Plain radiography:
– Findings are often normal.

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• Radiography helpful in hip involvement
in young children.
– Soft tissue swelling around the joint
– widening of the joint space
– displacement of tissue planes.
– Bony erosions and narrowing of joint
space in later stages of progression.
• Ultrasonography
– Very sensitive in detecting joint effusions
generated by septic arthritis

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TREATMENT
• Medical therapy:
– IV antibiotics - appropriate dose, route and
duration
– Drainage of the septic joint
• Surgical therapy:
– Adequate drainage of a septic joint is the
cornerstone of successful treatment
– Arthroscopic drainage and lavage
– Arthrotomy

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Postoperative:
• Nonweightbearing
• Splinting in a position of function
• Frequent passive range of motion exercises when
signs of inflammation subside
Follow-up:
– When infection clears
• Patients should gradually start isometric muscle
strengthening
• Active range of motion exercises

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Irreversible destruction of the joint occurs in
a large percentage of patients despite
proper treatment.
Major complications:
• Degenerative joint disease
• Soft tissue injury
• Osteomyelitis
• Fibrous plus bony ankylosis
• Sepsis
• Death.

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• Septic arthritis can:
– destroy a joint
– cause many complications:
• Osteomyelitis
• bony erosions
• fibrous ankylosis
• Sepsis
• even death.