CEN: Musculoskeletal and Wound Emergencies

In depth

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Compartment syndrome in depth

Perfusion of a compartment depends on the gap between capillary pressure and tissue pressure. Normal tissue pressure is about 8-10 mm Hg. When it rises, venous outflow and capillary flow fail long before the artery does, which is why a palpable pulse and normal capillary refill sit beside dying muscle. Hypotension narrows the gap, so a shocked patient becomes ischemic at a lower compartment pressure, and correcting blood pressure is part of treatment.

Causes go beyond the obvious fracture: crush injury, reperfusion after a limb was ischemic for hours (for example after embolectomy or vascular repair), burns, snakebite, heroin or cocaine overdose, coma with prolonged pressure on a muscle, casts and tight bandages. The anterior compartment of the leg is the most common site; the forearm, thigh, buttock, hand and foot are also affected. After long immobility on a floor, a tense, painful buttock with sciatic signs such as foot drop is gluteal compartment syndrome.

Positioning: once compartment syndrome is suspected, keep the limb at heart level and do not raise it. Donaldson 2014 says it should not be elevated, so as not to lower arterial flow further; a 2022 narrative review (Sonawane) says elevation is contraindicated because it lowers arterial flow and narrows the arterial-venous pressure gradient; a 2026 emergency department review (Rossie) says to the level of the heart, not above. Merck does not address position. The BOA standard BOAST 10 (revised 2025, standard 7) says the limb is elevated after circumferential dressings are released, without naming a height; check local policy against that. Routine elevation still applies to sprains, simple fractures and a swollen cast when compartment syndrome is not suspected. Never wait for pallor or pulselessness, which mark necrosis. In a sedated patient, measure the pressure and repeat it, because one normal reading does not exclude the diagnosis. After fasciotomy, expect a second look at 48-72 h and delayed closure or grafting within 7-10 days, and watch for rhabdomyolysis and hyperkalemia.

Dislocations, open fractures and children's fractures

Shoulder dislocations are about half of major joint dislocations, and 95% or more are anterior. Axillary nerve injury can reduce sensation over the deltoid, so test and record it before any reduction. Posterior dislocations follow seizures, electric shock or ECT without paralysis; the arm is adducted and internally rotated and cannot be turned outward, and a single AP film can look nearly normal, so an axillary or Y view is needed. After reduction, a sling and swathe; patients over 40 start motion early to avoid a frozen shoulder.

Most hip dislocations are posterior, from a flexed knee driven back against a dashboard. About 70% of posterior dislocations have an acetabular fracture. Delayed reduction raises the risk of femoral head osteonecrosis, so reduction is done as soon as possible, ideally within 6 h; sciatic nerve injury is the other complication to check for.

Knee dislocations injure the popliteal artery often, sometimes only the intima, so the limb can look fine until the vessel clots later. A grossly unstable, swollen knee after high-energy trauma is a reduced dislocation until proven otherwise. An ankle-brachial index of 0.9 or less is very sensitive for vascular injury and calls for an immediate vascular surgery consultation, with CT angiography as the gold-standard study; some experts image even above 0.9. Amputation rates climb when repair waits more than 8 h. The peroneal nerve is the nerve most often hurt (foot drop).

Open fractures (Gustilo-Anderson types): type I, wound 1 cm or less and clean, infection 0-2%; type II, larger wound without extensive soft-tissue damage, 2-10%; type III, extensive soft-tissue injury, segmental fracture or traumatic amputation, 10-50% (IIIC has an arterial injury needing repair). Cefazolin 2 g IV is the base regimen (Kolinsky: consider 3 g at 120 kg or more; vancomycin if penicillin allergic), with gentamicin added for type III (Gram-negative cover is still debated) and high-dose penicillin for farmyard or fecal contamination. Merck sets the target as within 1 h of ED arrival; Kolinsky says preferably within 6 h of injury. Remove gross debris, cover with a saline-moistened sterile dressing and splint; definitive irrigation and debridement happen in the operating room. Osteomyelitis complicates up to a quarter of open fractures.

Children: greenstick fractures crack one cortex and torus fractures buckle it, sometimes visible only as a subtle irregularity. A fracture through the growth plate can cause a limb-length difference. Supracondylar humerus fractures are about 60% of all elbow fractures; the radial pulse is absent in 7-12% overall and up to 19% of displaced fractures, and distal circulation, movement and sensation are documented before and after splinting. Radial head subluxation in toddlers needs no x-ray when the pull history is clear; hyperpronation has the higher first-attempt success, the child usually uses the arm within 10-20 minutes, and 27-46% recur.

Fat embolism, crush and rhabdomyolysis in depth

Primary-survey bleeding control, pelvic binders and trauma rhabdomyolysis targets are on Trauma: Primary and Secondary Survey; escharotomy and electrical injury are on Burns. Fat embolism syndrome follows long-bone and pelvic fractures, orthopedic surgery, bone marrow necrosis in sickle cell crisis and liposuction with fat grafting. Signs usually appear 24-48 h after injury (trauma-primary-survey gives 1-3 days): respiratory distress resembling ARDS, then confusion and a petechial rash over the head, neck, anterior chest and axillae. The Gurd and Wilson criteria (two major, or one major and four minor) are not validated. Reported incidence ranges from under 1% to 11% or more depending on how it is sought. Care is supportive: oxygen, early ventilation when needed (44% needed ventilation in one series), hemodynamic support. Early splinting and operative fixation are thought to prevent it. Corticosteroids reduced FES and hypoxia but not mortality in a 2009 meta-analysis and are not routine; no validated drug treatment exists. Mortality with supportive care is under 10%.

Crush syndrome is the systemic result of muscle crushed for hours: shock, then potassium, acid and myoglobin reaching the circulation when the pressure comes off. Start isotonic saline as early as possible, before extrication when it can be done and ideally within 6 h, at 1-1.5 L/h in adults (10-20 mL/kg/h in children), avoiding potassium-containing solutions when potassium is high. Put the patient on a monitor before release; IV calcium, bicarbonate and albuterol are the bridge for hyperkalemia. Bicarbonate and mannitol are still unproven.

Rhabdomyolysis: CK above 5 times the upper limit of normal (no formal cutoff); the classic triad of weakness, myalgia and dark urine appears in under 10%. A heme-positive dipstick with few RBCs suggests myoglobin, but a clear urine does not exclude it because myoglobin is cleared fast. AKI occurs in 15-55%, more with dehydration, sepsis or CK above 15,000. Expect high potassium, phosphate and uric acid, abnormal calcium, lactic acidosis and sometimes DIC; compartment syndrome needs early fasciotomy. IV fluids are the treatment. Merck gives no urine target; the crush-syndrome review cites above 300 mL/h and trauma-primary-survey gives 200-300 mL/h, so follow the local protocol and watch for overload.

Amputation, replantation and degloving

ILCOR's first aid task force (2024 draft) found that cooling without freezing, as soon as possible, is linked to replant survival and better function. The practical method is moist gauze around the part, a sealed watertight bag, and that bag placed in ice or ice water, with no direct ice contact and no immersion of the bare tissue, which macerates it. The part travels with the patient. Quoted ischemia limits are 12 h warm and 24 h cold for digits, and 6 h warm and 12 h cold for parts with muscle, so cooling buys the most time for parts with muscle. Case reports describe digits replanted after up to 94 h of cold storage, and the quoted limits are one author's recommendations, not task force thresholds.

Degloving strips skin and subcutaneous tissue from the deep fascia and tears the perforating vessels that feed it. Open degloving (a roller or wringer injury) is managed by controlling bleeding, replacing the tissue in its normal position under a moist sterile dressing, splinting and elevating the limb, analgesia and transfer to a reconstructive surgeon; a completely detached sheet of skin is handled like an amputated part. Closed degloving over the greater trochanter or thigh (Morel-Lavallée lesion) collects blood and lymph under skin that can necrose or become infected.

Tetanus and rabies in depth

Tetanus decisions ask about doses first, then the wound. Dirty or major wounds are punctures, wounds with soil, feces or saliva (bites), and wounds with devitalized tissue: burns, open fractures, crush injury, frostbite, necrotic or gangrenous wounds. From age 11, Tdap is preferred over Td for anyone who has never had Tdap. Any patient with an unknown history or fewer than 3 doses gets vaccine for any wound, and TIG is added only when the wound is dirty or major. CDC also gives TIG for a dirty wound in a patient with HIV or severe immunodeficiency regardless of vaccine history. Antibiotics do not prevent tetanus; watch the wound for infection instead. Prophylactic TIG is 250 IU IM (CDC); the treatment dose for established tetanus is 500 units IM with part infiltrated around the wound (Pink Book). Generalized tetanus, over 80% of cases, starts with trismus and spreads to neck stiffness, dysphagia and abdominal rigidity after an incubation of about 8 days (1-21). Because the toxin dose that causes disease is too small to immunize, a survivor starts or continues the vaccine series once stable, with one dose as Tdap (preferably the first) for anyone 7 or older who is not fully immunized.

Rabies PEP is a medical urgency, not an emergency, but it should not be put off. Wash every wound at once with soap and water and a virucide such as povidone-iodine if available. For a never-vaccinated patient, HRIG 20 IU/kg is given once: as much as possible into and around the wound, the rest IM at a site away from the vaccine, never in the same syringe; it can still be given through day 7 if missed. Vaccine 1 mL goes in the deltoid (anterolateral thigh in small children), never the gluteal area, on days 0, 3, 7 and 14, with a day 28 dose and an antibody check for immunocompromised patients. Pregnancy is not a contraindication. A previously vaccinated patient gets vaccine on days 0 and 3 and no HRIG. ACIP treats a bat in the room with a deeply sleeping person, an unattended child or an impaired or intoxicated adult as a possible exposure; a healthy domestic dog, cat or ferret is confined and observed for 10 days instead.

Bites and wound care in depth

Clean with soap and water, then irrigate copiously under pressure (syringe and IV catheter), debride devitalized tissue and look for tendon, joint, bone, nerve and vessel injury and foreign bodies such as tooth fragments. IDSA advises against primary closure of bites except on the face, where copious irrigation, cautious debridement and preemptive antibiotics make closure reasonable; Merck adds human bites, punctures, hand, foot, perineal and genital wounds, deep or heavily contaminated wounds and wounds more than several hours old to the leave-open list. Hand bites are wrapped, splinted in a functional position and elevated.

IDSA gives preemptive antibiotics for 3-5 days for hand or face wounds, moderate to severe injuries, edema, possible joint or bone penetration, asplenia, immunocompromise or advanced liver disease. Pasteurella is common in cat and dog bite infections; amoxicillin-clavulanate 875/125 mg twice daily covers it with the mouth anaerobes, and macrolides are avoided. A clenched-fist injury looks trivial, but when the fingers straighten the skin wound slides away from the joint and tendon and traps mouth flora inside. Examine it with the fist clenched, image for fracture and tooth fragments, leave it open, and expect IV ampicillin-sulbactam or a similar agent, tetanus prophylaxis and hand or orthopedic consultation; admission is considered for infected human bites.

Sutures out: face 3-5 days, trunk and arms 7-10, hands, knees, extensor elbow and below the knee 10-12. Irrigate with at least 100-300 mL saline under pressure. Lacerations: tissue adhesive suits simple wounds without tension, needs no removal visit and sloughs in about a week; ointment is not applied over it. Delayed primary closure means loose moist packing with at least daily changes and closure at 3-5 days if there is no infection. Povidone-iodine diluted 1:10 in saline is an option for bites, old wounds and organic debris.

Soft-tissue infection in depth

IDSA separates purulent infections (abscess, carbuncle, large furuncle, inflamed cyst) from nonpurulent cellulitis. Purulent lesions are drained; an anti-MRSA antibiotic is added when SIRS is present (temperature above 38 C or below 36 C, respiratory rate above 24, heart rate above 90, WBC above 12,000 or below 400) or host defenses are markedly impaired. WSES/SIS-E advise no antibiotic after drainage of a simple abscess. Typical nonpurulent cellulitis gets an antistreptococcal agent for 5 days, longer if not improving; vancomycin or another MRSA-active drug for penetrating trauma, injection drug use or SIRS. Elevate the limb and treat edema, venous insufficiency, eczema and toe-web fissuring or maceration (often tinea) to cut recurrence.

Necrotizing soft-tissue infection spreads along the fascia under skin that can look like mild cellulitis. Clues: pain out of proportion, edema or tenderness beyond the redness, wooden-hard subcutaneous tissue, bullae, crepitus, gray or necrotic skin, anesthesia, systemic toxicity and failure of antibiotics. Diagnosis is clinical: plain x-rays cannot rule it out, LRINEC at 6 or more has only 68% sensitivity and must not be used to exclude it, and imaging must not delay surgical consultation. WSES/SIS-E want source control at least within 12 h of admission in high-suspicion cases; one cited series had 38% mortality with delayed or incomplete debridement vs 4.2% with early, adequate surgery. Plan a re-look at 12-24 h (IDSA: back to the OR at 24-36 h) and repeat until no dead tissue remains, with large fluid needs from the open wounds.

Empiric antibiotics: vancomycin or linezolid plus piperacillin-tazobactam or a carbapenem, or ceftriaxone plus metronidazole. For documented group A streptococci, penicillin plus clindamycin: clindamycin suppresses streptococcal toxin and cytokine production, and penicillin stays alongside it for reliable streptococcal coverage. Continue antibiotics until no further debridement is needed, the patient has improved and fever has been gone 48-72 h. Mortality with group A strep, hypotension and organ failure runs 30-70%. IDSA says IVIG efficacy is not established and recommends against hyperbaric oxygen, which may delay resuscitation and debridement.

Joints, the limping child and the back

Septic arthritis risk rises with age, diabetes, rheumatoid arthritis, immunosuppression including steroids, a prosthetic or recently injected joint, skin infection, injection drug use, hemodialysis and sickle cell disease; fever may be absent. Synovial WBC is usually above 50,000 with more than 95% neutrophils and can exceed 100,000, but lower counts occur early or after antibiotics. Gram stain shows organisms in only 50-75%, so a negative stain changes nothing; culture is definitive but blunted by prior antibiotics, so aspirate first. Crystals in the fluid do not exclude coexisting infection: treat as infection pending culture. Empiric therapy is vancomycin when gram-positive cocci or no organisms are seen, adding an antipseudomonal agent for gram-negative risk, with early drainage (arthroscopic washout preferred).

Disseminated gonococcal infection shows as petechial or pustular acral lesions, asymmetric polyarthralgia and tenosynovitis, or as a purulent septic arthritis, often with no genital symptoms. Collect NAAT and culture from every exposed urogenital and extragenital site plus blood, joint fluid or skin. Treat with ceftriaxone 1 g IM or IV every 24 h, adding doxycycline if chlamydia is not excluded; switch to an oral agent guided by susceptibility 24-48 h after clear improvement, for at least 7 days in total. Admission and infectious disease input are advised, with a check for endocarditis and meningitis.

A child with a painful hip: the Kocher predictors are inability to bear weight, fever of 38.5 C or more, ESR 40 mm/h or more and WBC above 12,000; Caird added CRP of 20 mg/L or more. The more predictors present, the more likely septic arthritis, which needs urgent orthopedic aspiration and washout. Transient synovitis often follows a viral illness: a well child who walks with mild or no discomfort on simple analgesia needs no tests, gets paracetamol and an NSAID with child-directed activity, and is reviewed within 7 days if the limp persists; a child who cannot bear weight after analgesia is reassessed. Normal temperature early does not exclude infection.

Nonspecific low back pain with no red flags: no imaging for the first 4-6 weeks, stay active (no bed rest), heat or cold, NSAIDs. Back pain red flags (Merck): neurologic deficit, fever or chills, infection risk (immunosuppression, injection drug use, recent surgery or infection), known or suspected cancer, unexplained weight loss, severe nocturnal or disabling pain, acute tearing upper or mid-back pain, an abdominal aorta over 5 cm or leg pulse deficits. Cauda equina syndrome, most often from a lumbar herniated disc, causes saddle sensory loss, urinary retention or incontinence, loss of rectal tone and bilateral leg weakness; MRI is immediate and sphincter dysfunction or weakness means immediate surgery. Spinal epidural abscess presents as local or radicular back pain with percussion tenderness and often fever, and cord compression adds weakness and bowel or bladder dysfunction; ESR or CRP is raised, S. aureus is most common (about 60% in one series), MRI is diagnostic, lumbar puncture is contraindicated, and any neurologic deficit means immediate surgical drainage plus antibiotics covering staphylococci.

Exam pearls

• Compartment syndrome: pain on passive stretch comes first; limb at heart level; delta of 30 or less means fasciotomy.
• Pulses are present in early compartment syndrome and in many knee arterial injuries; neither rules anything out.
• Check and record nerve function before any reduction or splint.
• Open fracture: the IV antibiotic comes first, ideally within 1 h of arrival; formal washout happens in the OR.
• Fat embolism: hypoxemia first, then confusion, then petechiae; supportive care.
• Tetanus: dirty wound plus 5+ years, or clean wound plus 10+ years, means a booster; TIG only for dirty wounds with an incomplete or unknown series, or HIV.
• Cat bites and punches over a knuckle stay open and get amoxicillin-clavulanate or IV equivalent.
• A bat in the room with a sleeper means rabies PEP unless the bat is tested.
• Necrotizing infection looks like cellulitis with too much pain: call the surgeon.