ONC common mistakes
ONC · Understand the traps and how to avoid them.
Documents 'neurovascular status intact' after confirming a palpable pulse and pink, warm skin on a casted or splinted limb, without testing pain on passive stretch, light touch, or two-point discrimination.
Candidates memorize the 5 Ps as an equally weighted checklist, but pulselessness and pallor are late findings; the exam deliberately describes early compartment syndrome where the pulse is still present, so the candidate feels reassured for the wrong reason.
What to do instead
In every neurovascular check, test pain with passive stretch of the fingers or toes, light touch and two-point discrimination, and pain out of proportion to the injury; compare with the unaffected limb, document a trend rather than a single snapshot, and escalate a tense, firm compartment to the surgeon immediately rather than waiting for the pulse to disappear.
Attributes new restlessness, confusion, and tachypnea on the second day after a femoral shaft fracture to anxiety, pain, or atelectasis, and treats with reassurance, repositioning, or a prn anxiolytic.
Fat embolism syndrome appears 24 to 72 hours after long bone fracture with hypoxia, neurologic change, and a petechial rash, but the full classic triad is often incomplete, so the picture is mistaken for the more familiar postoperative problems.
What to do instead
Treat hypoxia plus new confusion or agitation plus petechiae over the chest, axillae, or conjunctivae after a long bone fracture as fat embolism until proven otherwise: apply oxygen, notify the provider, and monitor closely; explain that management is supportive (oxygenation, ventilation, stabilization), not anticoagulation as the primary therapy.
Lifts or removes the traction weights to slide the patient up in bed or to inspect the skin, then rehangs them and resets the knot.
Weights seem like a technicality compared with skin care and positioning, and habits from repositioning other immobilized patients carry over; the candidate does not realize that interrupting the line of pull and countertraction is what undoes the reduction.
What to do instead
State that weights must hang freely and never rest on the floor, bed, or frame, and are never removed; use a two-person technique in which one person supports or lifts the weights only momentarily while the other moves the patient along the line of pull, and obtain an order before changing weight, pulley angle, or rope position.
Elevates and ices a newly casted extremity with escalating pain, gives a prn analgesic, and defers calling the surgeon until the next scheduled rounds.
Swelling and pain are expected after fracture, so the candidate normalizes the finding; ice and elevation are remembered as the go-to interventions, and the sense that a cast 'protects' the limb lowers suspicion for compartment syndrome beneath it.
What to do instead
Treat pain that escalates despite analgesia, especially with pain on passive stretch, as a surgical emergency: notify immediately and prepare for bivalving (cutting through cast and all padding and webbing) or cast removal; never window the cast or apply tighter padding, and never wait for a repeat assessment at rounds.
Reassures and discharges a child with a swollen, point-tender ankle and a 'normal' radiograph as a sprain, with crutches and advice to see a pediatrician if it does not improve.
The physis is radiolucent and a Salter-Harris I injury often has no visible displacement on plain films; adult habit patterns make 'normal x-ray plus swelling equals sprain' feel like a complete answer, and the child may be surprisingly comfortable once splinted.
What to do instead
In a child with focal tenderness over the physis and refusal to bear weight, treat as a Salter-Harris I until proven otherwise: immobilize, keep non-weight-bearing, and arrange orthopaedic follow-up within days; teach parents the warning signs of growth arrest and deformity rather than framing the injury as a simple sprain.
Treats a negative rheumatoid factor as excluding rheumatoid arthritis and re-labels the patient's joint pain as osteoarthritis, directing education toward wear-and-tear and activity modification.
RF is the test candidates associate with RA, and early or seronegative disease with a negative result pushes the reasoning toward the more common OA diagnosis; the two conditions are then distinguished by vague impressions rather than pattern recognition.
What to do instead
Diagnose on the clinical pattern - symmetrical small-joint (MCP, PIP) involvement, morning stiffness lasting more than an hour, prolonged synovitis, systemic symptoms - supported by anti-CCP, ESR/CRP, and rheumatology referral; contrast this with OA's asymmetrical DIP and knee/hip involvement, brief stiffness, and bony nodes.
Screens for deep vein thrombosis by dorsiflexing the foot, documents a negative Homan sign, and records 'no DVT' as an assessment finding.
Homan sign persists in textbooks and older teaching even though it is neither sensitive nor specific, and a negative physical finding feels like a completed assessment that can be charted.
What to do instead
Assess unilateral calf or thigh swelling with serial tape measurement, warmth, erythema, and tenderness, and combine this with a validated tool (Wells), D-dimer, and venous ultrasound; report findings and risk level rather than documenting a negative Homan sign as a rule-out.
Sends a patient with an open tibia fracture to radiology before antibiotics are started, and irrigates or probes the wound in the emergency department.
The workup habit of 'image first' plus a strong instinct to clean a contaminated wound overrides the time-critical sequence, and the candidate does not treat antibiotics as the first intervention.
What to do instead
Cover the wound with sterile saline-soaked gauze, splint the limb, give IV antibiotics within one hour, verify tetanus status, and then obtain imaging; emphasize that only the operating room performs irrigation and debridement and that ED probing pushes contamination deeper.
Withholds a prn opioid from an older adult with dementia who is grimacing and guarding because the numeric pain rating is 0 and the vital signs are normal, then charts 'denies pain.'
The numeric scale is treated as the gold standard even when it is invalid for the patient, vital signs are mistaken for an objective pain measure, and fear of opioid adverse effects tips the decision toward withholding.
What to do instead
Use a behavioral tool such as PAINAD and reassess with the same tool after the intervention; give scheduled multimodal analgesia titrated to behavior, and treat sedation and respiratory rate as the safety endpoints rather than expecting a change in blood pressure or heart rate.
Hands every total hip replacement patient the same 'no bending past 90 degrees, no crossing legs' sheet without confirming the surgical approach, and tells a partial weight-bearing patient to 'put about half your weight' with no scale practice or crutch training.
Standardized handouts feel thorough and the hip precautions are memorable, but the candidate does not check whether the approach and the surgeon's weight-bearing prescription match the generic teaching; vague fractions seem precise enough for a family to follow.
What to do instead
Verify the surgical approach and the written weight-bearing order before teaching (posterior precautions versus anterior approach restrictions), and have physical therapy teach weight-bearing on a scale plus crutch and walker technique with a return demonstration before discharge.