9.4 Common Traps in Musculoskeletal and Wound Disorders

The Elevation and Pulse Traps

Two distractors recur in compartment-syndrome items. First, elevation: it is correct for ordinary post-injury swelling but wrong in suspected compartment syndrome, where raising the limb above the heart lowers arterial inflow and worsens ischemia-keep the limb at heart level. Second, the palpable pulse: large arteries can remain patent while capillary perfusion has already failed, so the presence of distal pulses does not exclude compartment syndrome. Pulselessness and paralysis are late findings. The findings you actually trust are pain out of proportion, pain on passive stretch, and paresthesia.

A third trap: applying cold packs to the involved compartment. Cold causes vasoconstriction and further reduces an already compromised perfusion.

A fourth, subtler trap is the rising opioid requirement itself. When a stem notes that a patient now needs far more analgesia than the injury should cause, that escalating, unrelieved pain is a flag for compartment syndrome rather than a cue simply to give another dose. The correct response is to reassess and escalate-remove constriction, examine for pain on passive stretch, and notify the provider-not to keep medicating around a developing emergency.

Missing the Septic Joint

Septic arthritis is an orthopedic emergency that distractors disguise as gout or a simple effusion. The classic picture is a single hot, swollen, exquisitely painful joint the patient refuses to move, often with fever. Untreated, pus destroys cartilage within days. The action is urgent arthrocentesis for synovial analysis and culture, then antibiotics.

In children with a painful hip, the Kocher criteria estimate septic-arthritis likelihood: non-weight-bearing, fever >38.5 C, ESR >40 mm/hr, and WBC >12,000/mm3-meeting all four predicts >99% probability. The trap is treating a febrile child's refusal to bear weight as a minor strain.

Benign-Looking Pain That Isn't

Costochondritis (inflammation of the costochondral junctions) produces reproducible, palpable chest-wall tenderness and is benign-but it is a diagnosis of exclusion. The trap is anchoring on it before ruling out acute coronary syndrome, pulmonary embolism, and aortic dissection, which can coexist with chest-wall tenderness.

Low back pain is usually mechanical, but the CEN tests the red flags that turn it into an emergency:

• Cauda equina syndrome - saddle anesthesia, urinary retention (most common sign) or incontinence, bowel incontinence, and bilateral lower-extremity weakness. This is a surgical emergency needing emergent MRI and decompression.
• Other red flags: fever (spinal infection/abscess), history of cancer (metastasis), significant trauma, IV drug use, and progressive neurologic deficit.

The distractor is discharging a back-pain patient with new urinary retention and saddle numbness as "muscle strain."

Rhabdomyolysis: The Hidden Crush Complication

After crush injury, prolonged immobilization, or compartment syndrome, watch for rhabdomyolysis-skeletal-muscle breakdown releasing myoglobin, potassium, and creatine kinase. The classic triad is muscle pain, weakness, and dark (tea/cola-colored) urine. Labs: markedly elevated creatine kinase (CK)-typically >5 times the upper limit of normal, with >5,000 U/L an indication for aggressive hydration-plus myoglobinuria (urine dipstick positive for blood with no red cells on microscopy).

The two life threats are hyperkalemia (cardiac arrest) and acute kidney injury from pigment nephropathy. Treatment is aggressive IV isotonic fluids (20 mL/kg boluses) to flush myoglobin and protect the kidneys, with continuous cardiac monitoring and electrolyte management of hyperkalemia. The trap is overlooking rhabdomyolysis in a crush or down-for-hours patient who looks stable but has cola-colored urine.

The Open-Fracture and Tetanus Shortcut Traps

Two more distractors recur. With an open fracture, the wrong answers are "push the exposed bone back under the skin" and "delay antibiotics until the surgeon evaluates." Both are unsafe: never reduce protruding bone (it drives contaminants deeper), and early IV antibiotics are a core, time-sensitive intervention, not an optional later step. The correct nursing answer covers the wound with a sterile saline-moistened dressing, controls bleeding, gives antibiotics, addresses tetanus, and prepares the patient for the OR.

With tetanus, the classic trap mixes up the two intervals. Test-writers offer "give a booster only if it has been more than 10 years" for a dirty wound-but dirty wounds use the 5-year rule. Another trap offers TIG for a clean minor wound, where TIG is never indicated. Anchor on three numbers: 10 years (clean), 5 years (dirty), and 3 prior doses as the line below which a dirty wound also earns TIG 250 units IM.

Distinguishing Look-Alikes

The single best habit is to ask, for every "benign" musculoskeletal stem, what dangerous condition could this be hiding?