Clostridium tetani - Tetanus in Orthopaedic Infection

Etiology

• Spores are ubiquitous in soil, animal feces, and environmental surfaces - they can survive for years
• Enters the body through wounds (puncture wounds, open fractures, lacerations, abrasions, burns, frostbite, bite injuries)
• In agricultural areas, spores can be found on skin or in contaminated heroin
• No wound is identified in up to 10% of tetanus cases - it can also occur after surgical procedures, otitis media, or abortion
• Once inside the body, spores germinate into the toxin-producing vegetative form when tissue oxygen tension is reduced (anaerobic conditions)

• Wound >6 hours old
• Stellate, avulsion, or crush injury
• Abrasion, bite, or needle wound
• Depth >1 cm
• Missile injury
• Burn or frostbite
• Foreign body under the skin
• Infected, devitalized, denervated, or ischemic tissue
• Contaminants (dirt, feces, soil, saliva) present in the wound

Pathology / Pathophysiology

1. Tetanolysin - facilitates growth of the bacterial population by lysing red blood cells and disrupting surrounding tissue
2. Tetanospasmin - a powerful neurotoxin responsible for ALL clinical manifestations of tetanus

• Reaches the nervous system via hematogenous spread to peripheral nerves, then retrograde intraneuronal transport to the CNS
• Does NOT cross the blood-brain barrier directly - retrograde intraneuronal transport gives it CNS access
• Binds to neuromuscular junctions of CNS neurons, rendering them incapable of neurotransmitter release
• Prevents release of inhibitory neurotransmitters glycine and GABA from presynaptic nerve terminals
• This releases the nervous system from its normal inhibitory control, leading to failure of inhibition of motor reflex responses to sensory stimulation
• Agonist and antagonist muscles contract simultaneously, producing tetanic spasms
• Loss of inhibition also affects preganglionic sympathetic neurons, producing sympathetic overactivity and high circulating catecholamines

Signs and Symptoms

Three Clinical Forms

• Most common presenting complaints: pain and stiffness in the masseter muscles ("lockjaw"/trismus)
• Progression is descending: facial muscles first (short axons), then neck, trunk, and extremities
• Risus sardonicus (sardonic smile) - the classic fixed grimace from facial muscle spasm:

• Opisthotonus - arching of the whole body from spasm of paravertebral and extensor limb muscles
• Reflex convulsive spasms and tonic contractions cause dysphagia, arm flexion, fist clenching, lower limb extension
• Laryngeal spasm leads to apnoea, asphyxia, and respiratory arrest
• Spasms triggered by the slightest sensory stimulus
• Spasms last 3-4 weeks; recovery may take months
• Mental status remains NORMAL (important differentiating feature) unless respiratory compromise occurs
• Autonomic dysfunction: tachycardia, labile hypertension, diaphoresis, arrhythmias
• Complications: rhabdomyolysis, long bone fractures from violent muscle contractions, aspiration pneumonia (present in 50-70% of autopsied cases)

• Follows head injuries or otitis media
• Cranial nerve dysfunction, most commonly CN VII (facial nerve)
• Poor prognosis

• Muscle rigidity confined to the site of injury
• Usually resolves after weeks to months
• May progress to generalized form
• ~1% fatality rate

Investigation

• Serum antitoxin titers >0.01 IU/mL are usually protective, but tetanus can still occur even with protective levels
• An immunochromatographic dipstick test allows rapid assessment of immunity (88% sensitivity, 98% specificity) - useful in high-incidence regions
• Wound culture has limited value: C. tetani may be cultured from wounds without clinical disease, and may NOT be recovered in confirmed tetanus cases
• In the USA, 96% of cases occur in patients with unknown or inadequate immunization history
• The elderly, those on hemodialysis, and immunocompromised patients often have inadequate immunity

Treatment

1. Prevention (most important)

• 0.5 mL tetanus toxoid IM for wounds contaminated with soil or at risk
• Booster dose for patients previously immunized
• A full active immunization series must be started in unimmunized patients

• Human anti-tetanus globulin (ATG) / Human Tetanus Immunoglobulin (HTIG): 250-500 U IM for patients with tetanus-prone wounds or those not previously immunized
• Can be given simultaneously with toxoid - separate syringes and separate injection sites must be used
• ATG provides longer-lasting protection than equine antitoxin
• Wound debridement should be performed a few hours after ATG to minimize tetanospasmin release

2. Local Wound Care

• Thorough wound debridement to eliminate the anaerobic environment, remove spores, and prevent further toxin production
• Remove all devitalized and ischemic tissue
• Wound closed using delayed primary or secondary closure techniques
• IV Penicillin G 10-24 million units/day for 10-14 days (metronidazole is an effective alternative)

3. Supportive Care for Established Disease

• ICU admission mandatory - free from strong sensory stimuli (minimize light, noise, touch)
• Immediate neuromuscular blockade and intubation for respiratory compromise
• Diazepam to prevent onset of spasms; if spasms become sustained, the patient is paralysed, intubated, and placed on a ventilator
• Gradual ventilator weaning under anticonvulsant cover
• Intrathecal antitoxin has been used for spasm control to avoid ventilatory support
• Provide tetanus immunization: the disease does NOT confer immunity

• Neutralizes circulating toxin (cannot reverse toxin already bound to nerve terminals)
• 500 U IM is the recommended dose for active tetanus

• Overall mortality ~45% in full-blown disease (Bailey & Love); 7% in developed countries with modern ICU care (CDC 2009-2017 data)
• Prognosis determined by incubation period and the interval from first symptom to first tetanic spasm - shorter intervals = worse prognosis
• Survivors may require several weeks of hospitalization
• Without access to mechanical ventilation, mortality remains very high

• Campbell's Operative Orthopaedics 15th Ed 2026, eBOX 58.1 / eTable 58.1
• Bailey and Love's Short Practice of Surgery 28th Ed, Ch. 33
• Tintinalli's Emergency Medicine: A Comprehensive Study Guide, Ch. 157