12.2 Trauma
Key Takeaways
- Always assess alignment first on trauma films — malalignment (dislocation, listhesis, widened joint space) is an emergency referral before you characterize the fracture pattern
- Acute fractures show sharp, non-corticated margins, cortical breach, and soft-tissue swelling; chronic or congenital mimics show smooth corticated borders
- Compression and burst vertebral fractures in patients over 50 or with osteoporosis history raise malignancy/pathologic fracture suspicion until proven otherwise
- Salter-Harris types I and II in children may show minimal radiographic abnormality — refer when physeal tenderness exists despite normal films
- Stress fractures appear as subtle cortical lucency or periosteal reaction in high-load athletes — early referral prevents complete fracture
12.2 Trauma
Quick Answer: Trauma imaging on Part II tests whether you can run a systematic ABCS review, recognize alignment emergencies before fracture detail, and match radiographic patterns to the correct clinical impression and referral urgency. Malreduction, dislocation, unstable spine injury, and open fracture equivalents are never "watch and adjust" cases — they require immediate referral or emergency transfer.
Trauma cases within Diagnostic Imaging sit at the intersection of pattern recognition and clinical decision-making. The vignette usually gives mechanism, age, weight-bearing status, and neuro status; the film confirms or refutes your working diagnosis. Part II rewards candidates who read alignment first, because a missed facet dislocation or atlantoaxial subluxation matters more than mislabeling a fracture type.
ABCS for Trauma: Alignment Comes First
- Alignment — vertebral bodies stacked? Facet pairs congruent? Joint surfaces aligned? Listhesis grade? Atlantodental interval (ADI) <3 mm adults, <5 mm children?
- Bone — cortical break, step-off, compression, avulsion, periosteal reaction
- Cartilage/joint spaces — widened MCL/LCL stress gap, joint effusion indirectly suggested by fat-pad signs, dislocation with widened joint space
- Soft tissues — prevertebral soft-tissue swelling (>7 mm C2, >22 mm C6 suggests hematoma), joint effusion fat pads (sail sign elbow), soft-tissue gas (open injury)
If alignment is abnormal, stop and classify urgency before naming the fracture morphology.
Cervical Spine Trauma
Clinical Decision Context
Validated rules (NEXUS, Canadian C-Spine Rule) reduce unnecessary imaging, but Part II items often present films already obtained. Your job is interpretation and management implication.
Key Radiographic Patterns
| Pattern | Sign | Clinical Impression |
|---|---|---|
| Wedge/compression fracture | Anterior height loss, intact posterior wall | Stable if <25–50% height loss and no neurologic deficit; unstable if >50% or posterior involvement |
| Burst fracture | Loss of both anterior and posterior vertebral body height; retropulsion | Unstable — cord compression risk; urgent MRI/CT and spine referral |
| Facet dislocation | Bow-tie / inverted hamburger sign on lateral; >25% translation | Unstable — unilateral (25%) vs bilateral (50%+); emergency management |
| Hangman's fracture (C2 pedicle) | Fracture through C2 pars with C2-C3 subluxation | High-grade injury; urgent spine referral |
| Jefferson fracture (C1) | Overhang of C1 lateral masses beyond C2 on open-mouth view | Check transverse ligament integrity; may be unstable |
| Odontoid fracture | Fracture line at dens base; sharp margins | Type II dens fractures have high nonunion rate; urgent orthopedic/neurosurgical referral |
Prevertebral soft-tissue swelling on lateral cervical films suggests acute hemorrhage/edema even when no fracture line is visible — correlate with mechanism and consider CT if clinical suspicion remains high.
Thoracolumbar Spine Trauma
Compression vs. Burst vs. Chance
- Compression fracture: Anterior wedging, posterior elements intact; common in osteoporosis; in patients >50 with minimal trauma, consider pathologic fracture (metastasis, myeloma) and refer for workup
- Burst fracture: Biconcave or comminuted body with posterior cortex retropulsion into canal; unstable; MRI for cord/cauda equina
- Chance fracture (flexion-distraction): Horizontal fracture through vertebral body and posterior elements; often seatbelt injury; associated intra-abdominal injury — urgent comprehensive trauma evaluation
Spondylolisthesis After Trauma
Acute pars fracture (isthmic) or facet fracture can produce new listhesis. Compare to prior films if available. Neurologic deficit with listhesis = emergency referral.
Extremity Fracture Recognition
Upper Extremity High-Yield Patterns
- Colles fracture: Distal radius fracture with dorsal angulation/displacement ("dinner fork" deformity clinically)
- Smith fracture: Reverse Colles — volar angulation
- Scaphoid fracture: Waist fracture may be radiographically occult initially; snuffbox tenderness with normal film → thumb spica and repeat imaging or MRI at 10–14 days
- Monteggia: Proximal ulna fracture + radial head dislocation — check alignment on every forearm film
- Galeazzi: Distal radius fracture + distal radioulnar joint disruption
- Elbow effusion: Anterior and posterior fat pad sign on lateral elbow — occult fracture until proven otherwise in trauma
Lower Extremity High-Yield Patterns
- Fibular fracture at ankle (Weber classification) — correlates with syndesmotic injury and stability; Weber C (proximal fibula) suggests syndesmosis disruption
- Tibial plateau fracture — depression/split; assess for compartment syndrome clinically
- Calcaneal fracture — comminuted intra-articular; check for associated lumbar burst fracture (10% association from axial load)
- Fifth metatarsal: Distinguish Jones fracture (metaphyseal-diaphyseal junction, poor healing) from avulsion at styloid (pseudo-Jones, more favorable) and stress fracture (proximal diaphysis in athletes)
- Hip: Femoral neck fracture in elderly — surgical emergency; posterior hip dislocation — femoral head posterior/superior on lateral, shortened internally rotated limb
Pediatric Trauma: Salter-Harris and Greenstick
Physeal injuries are growth-plate emergencies.
| Type | Description | Prognosis/Referral |
|---|---|---|
| I | Slipped physis, no visible fracture line | May be radiographically occult; refer if tenderness |
| II | Fracture through physis + metaphysis (Thurston-Holland fragment) | Most common; generally good if reduced |
| III | Fracture through physis into epiphysis | Intra-articular — orthopedic referral |
| IV | Through epiphysis, physis, and metaphysis | Growth arrest risk — urgent orthopedic referral |
| V | Crush injury to physis | Worst prognosis; may be occult on film |
Greenstick/torus/buckle fractures in children show incomplete cortical break on one side — still require immobilization and appropriate referral per severity.
Stress and Insufficiency Fractures
- Stress fracture: Repetitive loading in athletes (tibia, metatarsals, femoral neck, pars interarticularis); early film may show only periosteal reaction or subtle cortical lucency; MRI/bone scan if clinical suspicion high
- Insufficiency fracture: Normal stress on weakened bone (osteoporosis, long-term steroids); sacral ala, pubic rami, vertebral bodies
- Femoral neck stress fracture on tension side — urgent orthopedic referral (complete fracture risk, avascular necrosis)
Avulsion vs. Accessory Ossicle (Trauma Pitfall)
After an acute mechanism, a small bone fragment near a tendon insertion may be avulsion fracture or an incidental accessory ossicle.
| Feature | Avulsion Fracture | Accessory Ossicle |
|---|---|---|
| Margins | Sharp, matches donor site | Smooth, corticated all around |
| Laterality | Usually unilateral | Often bilateral |
| Soft tissues | Swelling common | Normal |
| Mechanism | Forced contraction/trauma | May be none |
When in doubt with a high-demand athlete and clinical tenderness at a synchondrosis (bipartite patella, os acromiale), treat as injury and refer — MRI clarifies.
Referral Urgency Framework
Emergency (same-day ED/transfer): Cauda equina or progressive deficit, open fracture, vascular compromise, irreducible dislocation, unstable spine (burst, bilateral facet dislocation, high-grade listhesis with deficit), compartment syndrome signs
Urgent (24–72 hours): Unstable or displaced fractures needing reduction (hip, many ankle patterns), odontoid Type II, scaphoid with high suspicion, femoral neck stress fracture, Monteggia/Galeazzi pattern
Routine orthopedic referral: Most closed, reduced, stable fractures; stress fractures without high-risk location
Office management with follow-up imaging: Minimally displaced distal phalanx, some stable distal radius patterns in low-demand patients — still know when your state scope ends and referral is mandatory
Part II Exam Strategy for Trauma Films
- Read mechanism and neuro status in the stem first
- ABCS — if alignment is off, name the dislocation/listhesis before the fracture
- Look for second injuries (calcaneus + spine, forearm + DRUJ, elbow fat pad + occult fracture)
- Age matters: >50 + compression fracture = pathologic until proven otherwise
- Choose the answer that matches referral urgency, not just the anatomic label
Trauma imaging is not about cataloging every eponym — it is about protecting patients from missed unstable injuries and matching radiographic severity to the correct next step in care.
A lateral cervical radiograph after a diving accident shows approximately 50% anterior translation of C4 on C5 with bilateral facet dislocation appearance. The patient has new upper extremity weakness. What is the priority clinical impression?
A 72-year-old woman reports sudden back pain after lifting a grocery bag. Thoracic radiographs show a wedge compression fracture of T11 with approximately 30% anterior height loss and intact posterior cortex. She has no neurologic deficits. What additional consideration is most important for the clinical impression?
A lateral elbow radiograph after a fall on an outstretched hand shows elevation of both anterior and posterior fat pads. No fracture line is visible. What is the most appropriate next step in clinical impression?
A 14-year-old soccer player has medial knee pain after a valgus injury. Radiographs show widening of the medial joint space with a Salter-Harris Type IV fracture of the distal femur involving the epiphysis, physis, and metaphysis. What is the appropriate referral urgency?