High Yield Films I: Trauma

Trauma films are where an imaging station tests judgment as much as recognition. The candidate who names the fracture but then says "I would adjust above and below it" has failed the station, while the candidate who calmly states the finding, its location and view, a one line impression, and "no manipulation of this region, immobilize and refer" has earned nearly every point. This chapter covers the trauma films that recur on practical exams and in practice, and shows how to turn each one into a spoken answer that is fast, accurate and safe.

Section 1Cervical trauma films

How a trauma film station usually runs

An imaging task usually gives a door card with a brief history and one or more films, and asks what you see and what you would do. Examiners typically score the key finding, its location and best view, the impression and a safe recommendation; missing an unstable fracture, or recommending manipulation through one, can outweigh everything else. Formats and timing change, so check the current official candidate materials.

Use a fixed spoken template for every film: the view, adequacy, the key finding with level and side, secondary findings, a one line impression and the recommendation. Ending on the recommendation every time guarantees you never forget the step that carries the most weight.

The adequate lateral cervical film and the four lines

The neutral lateral is adequate only when the top of T1 is visible; missed lower cervical injuries hide at C6 to T1 behind the shoulders. The plain film fix is a swimmer's view, but a patient with real trauma risk needs CT. Trace four smooth curves: the anterior vertebral line, the posterior vertebral line (George's line, the front wall of the canal), the spinolaminar line (the back wall of the canal; in children the posterior cervical line of Swischuk separates C2 to C3 pseudosubluxation from a hangman fracture) and the spinous process line. A step or abrupt angle localizes the injured segment; fanning of spinous processes, a widened facet or focal kyphosis point to ligament disruption even without a fracture line.

Soft tissue signs

Blood and edema widen the prevertebral soft tissue. Commonly taught adult limits are about 7 mm at C2 and 22 mm at C6 ("7 at 2, 22 at 6"; about 14 mm at C6 in children). It is a supporting sign, not a rule out: many fractures do not widen it, and crying or flexion can. Displacement of the prevertebral fat stripe is a related clue.

Upper cervical injuries: C1 and C2

The atlas is a ring with two thick lateral masses. The axis carries the dens, which is held against the anterior arch of C1 by the transverse ligament. The atlantodental interval (ADI), measured on the lateral from the posterior surface of the anterior arch of C1 to the anterior surface of the dens, is normally 3 mm or less in adults and 5 mm or less in children. A larger ADI means transverse ligament failure, whether from trauma, rheumatoid arthritis, Down syndrome or infection in the pharynx (Grisel syndrome).

Odontoid fractures (Anderson and D'Alonzo): type I avulses the tip and is rare; type II crosses the poorly perfused base and is the most common and most likely to fail to unite; type III enters the C2 body and heals better. Separate a true fracture from a Mach band (a lucency from overlapping arch or teeth that runs beyond the dens margins) and, in young children, the dentocentral synchondrosis. An os odontoideum (smooth corticated ossicle, hypertrophied anterior arch of C1) is unstable and earns the same answer: no upper cervical manipulation and referral. Lateral mass offset can come from head rotation, and children up to about 4 years show a pseudo Jefferson offset; bilateral overhang in an adult after axial load is a fracture until CT says otherwise.

Lower cervical injuries: C3 to C7

Below C2, injuries are best understood by mechanism. Flexion compresses the front and distracts the back; extension does the reverse; rotation added to flexion produces unilateral facet injury.

The two teardrops share a name and nothing else. In the flexion teardrop the small fragment signals a three column injury, with the body driven back into the canal and often an anterior cord syndrome. In the extension teardrop the anterior longitudinal ligament pulls off a corner and the posterior structures are intact. In a unilateral facet dislocation the facets superimpose above the level and sit side by side (bow tie) at and below it; a slip of half the body width or more means bilateral dislocation with torn disc and posterior ligaments.

Flexion and extension films and instability

Spasm can hide ligament injury on neutral films. Flexion and extension laterals reveal abnormal motion; widely cited lower cervical limits are more than about 3.5 mm of translation or more than about 11 degrees of angulation relative to adjacent levels, and an ADI that widens in flexion means transverse ligament insufficiency. Do not take them with a known or suspected fracture, dislocation or neurologic deficit, or in an obtunded or intoxicated patient. Early films are often falsely normal, so they are commonly repeated after 7 to 14 days, with the patient moving actively within comfort.

Section 2Thoracolumbar trauma films

The three column concept

The Denis three column model remains the simplest way to reason about thoracolumbar stability on a plain film. The anterior column is the anterior longitudinal ligament, the anterior two thirds of the vertebral body and the anterior annulus. The middle column is the posterior third of the body, the posterior annulus and the posterior longitudinal ligament. The posterior column is the pedicles, facets, laminae, spinous processes and the posterior ligament complex (supraspinous, interspinous and ligamentum flavum, plus the facet capsules). Injury to one column is usually stable; injury to two or more columns, and especially any injury involving the middle column, is potentially unstable. The more columns broken, the less stable the spine.

About half of thoracolumbar fractures occur at the thoracolumbar junction (T11 to L2), where the stiff, rib supported thoracic spine meets the mobile lumbar spine. High energy fractures here travel with other injuries: a burst fracture from a fall onto the feet often accompanies calcaneal fractures, and a Chance fracture from a lap belt often accompanies abdominal visceral injury.

Compression, burst and Chance fractures

On the lateral, judge a compression fracture by comparing anterior, middle and posterior heights. A commonly used semiquantitative grading (after Genant) calls height loss of about 20 to 25% mild, 25 to 40% moderate and more than 40% severe. Signs that a fracture is acute include a step defect or buckle in the anterior cortex, a band of increased density under the endplate (the zone of impaction, where trabeculae have been crushed together), endplate disruption and paraspinal soft tissue swelling. An old healed fracture has smooth margins and no impaction zone. When age cannot be settled on the plain film, MRI (fluid sensitive sequences show marrow edema in an acute fracture) or a bone scan answers the question.

The deciding structure is the posterior body wall: straight and intact suggests a wedge fracture; bowed, broken, with a fragment behind the posterior vertebral line or with widened pedicles on the AP means a burst fracture and CT.

Osteoporotic versus pathologic compression fracture

In older adults, the commonest compression fracture is osteoporotic (insufficiency fracture of weakened bone under normal load), but a fracture through bone already destroyed by metastasis or myeloma (pathologic fracture) looks similar at first glance and carries a very different plan. The distinction relies on the pattern of the vertebra and its neighbors.

Suspected pathologic fracture: MRI, labs (CBC, ESR or CRP, calcium, alkaline phosphatase, protein electrophoresis) and referral. Osteoporotic fracture: no thrust at or near it, low force care, DXA and bone health referral.

Thoracic and lumbar trauma mimics

Mimics: Schmorl nodes (rounded corticated endplate defects), the limbus bone (a smooth corticated anterosuperior corner fragment from disc herniation under the ring apophysis), Scheuermann disease (three or more adjacent wedged thoracic bodies with irregular endplates) and mild physiologic wedging at T12 and L1.

Section 3Pars defects and spondylolisthesis

Spondylolysis and the Scotty dog

Spondylolysis is a defect in the pars interarticularis, the narrow bridge of bone between the superior and inferior articular processes. Most defects are fatigue (stress) fractures that develop in childhood or adolescence from repeated extension and rotation, which is why they are common in gymnasts, divers, football linemen, dancers and fast bowlers. About 85 to 90% occur at L5, most of the rest at L4, and roughly three quarters are bilateral. When the defects are bilateral, the vertebral body, pedicles and superior facets can slide forward while the lamina, inferior facets and spinous process stay behind: that forward slip is isthmic spondylolisthesis.

The classic plain film sign is on the oblique lumbar view, where the posterior elements form the outline of a Scotty dog. The nose is the transverse process, the eye the pedicle, the ear the superior articular process, the neck the pars interarticularis, the body the lamina and the front leg the inferior articular process. A pars defect appears as a lucent band across the neck, the collar on the dog. On the lateral view a defect is sometimes visible as a lucent oblique line behind the pedicle, and the slip itself is measured on the lateral. Many defects are invisible on plain films; CT shows the gap, and MRI or SPECT shows an early stress reaction.

Grading the slip

The Meyerding method divides the superior endplate of the vertebra below (usually S1) into four equal parts and grades the slip by how far the posteroinferior corner of the vertebra above has moved forward: grade I up to 25%, grade II 26 to 50%, grade III 51 to 75%, grade IV 76 to 100%, and grade V (spondyloptosis) beyond the front of the sacrum. Ullmann's line (Garland's line), drawn up from the anterior margin of the sacral base perpendicular to the sacral endplate, should not be crossed by the L5 body; crossing it indicates an anterior slip. In spondyloptosis the AP film shows the inverted Napoleon hat sign, the L5 body projected end on over the sacrum.

Types of spondylolisthesis

Isthmic versus degenerative: what the film and the hands show

The two common types behave in opposite ways in the canal. In isthmic spondylolisthesis, the posterior arch stays behind as the body slides forward, so the canal at that level actually widens, and symptoms are usually low back pain with or without radicular pain from the nerve root caught in the fibrocartilaginous tissue of the defect (the L5 root at an L5 slip). In degenerative spondylolisthesis, the whole vertebra slides forward, arch and all, so the canal is pinched between the posterior arch above and the body below, causing central and lateral recess stenosis and neurogenic claudication (leg pain with walking or standing that is relieved by sitting or flexing).

The palpable step follows the same logic. With an isthmic L5 slip the L5 spinous process stays back with the arch while L4 and everything above move forward with the L5 body, so the step is felt between the L4 and L5 spinous processes, at the level above the slipped vertebra. With a degenerative L4 slip the L4 spinous process travels forward with its body, so the step is felt at the slipped level itself.

What to recommend

Most adults with a stable grade I or II isthmic slip do well with conservative care, and spondylolisthesis by itself is not an absolute contraindication to chiropractic care. Sensible modifications include avoiding a forceful posterior to anterior thrust directly on the anteriorly displaced segment, favoring adjacent level adjustments, flexion distraction and core stabilization, and avoiding repetitive end range extension. Flexion and extension laterals show whether the slip moves; translation of more than about 4 mm, or a slip that changes grade between flexion and extension, suggests instability.

Section 4Pelvis, hip and extremity trauma films

General rules for extremity trauma films

Follow the rule of two: two views at right angles, the joints above and below a long bone fracture, and comparison views in children when needed. After the first fracture keep looking (satisfaction of search); a broken forearm bone usually has a partner injury. The Ottawa rules tell you when films are needed.

Pelvis and hip

Hip fractures in older adults follow low energy falls and present with a shortened, externally rotated leg and inability to bear weight. They are divided by their relation to the joint capsule. Intracapsular fractures (subcapital, transcervical and basicervical femoral neck fractures) can tear the retinacular vessels that supply the femoral head, so they carry a high risk of avascular necrosis and nonunion, especially when displaced. The Garden classification grades femoral neck fractures from I (incomplete or valgus impacted) and II (complete, undisplaced) to III (partially displaced) and IV (fully displaced); III and IV are the high AVN risk group. Extracapsular fractures (intertrochanteric and subtrochanteric) bleed more but rarely cause AVN. On the AP pelvis, look for disruption of Shenton's line (the smooth arc from the inferior femoral neck to the superior border of the obturator foramen), a change in the neck shaft angle, a sclerotic band of impaction, and a break in the cortex of the neck.

Up to about 10% of hip fractures are invisible on the initial films. A patient who cannot bear weight after a fall, with pain on axial loading or log roll, needs MRI (or CT if MRI is unavailable) the same day, not reassurance. A femoral neck stress fracture in a runner or military recruit is a separate trap: compression side fractures on the inferomedial neck are usually managed with rest, but tension side fractures on the superolateral neck can displace and need urgent orthopedic referral.

Slipped capital femoral epiphysis (SCFE) is a Salter Harris type I injury through the proximal femoral physis in an adolescent (typically 10 to 16 years, often overweight, boys more than girls), presenting with hip, thigh or knee pain and a limp. The epiphysis slips posteriorly and medially. On the AP, Klein's line along the superolateral neck fails to intersect the epiphysis, and the physis looks widened and blurred; the frog leg lateral shows the slip best. About a fifth to a quarter are bilateral. The patient must stop weight bearing and be referred the same day for surgical pinning, because further slip risks AVN. Legg Calve Perthes disease (idiopathic AVN of the femoral head, ages about 4 to 8) shows a small, dense, flattened and later fragmented epiphysis, often with a subchondral lucent crescent sign.

Also recognize adolescent apophyseal avulsions (ASIS by sartorius, AIIS by rectus femoris, ischial tuberosity by hamstrings), pelvic ring fractures (one break usually means a second), sacral insufficiency fractures in osteoporotic women, and posterior hip dislocation (dashboard injury, adducted and internally rotated limb, sciatic nerve risk), an emergency.

Wrist and hand

The scaphoid is the most commonly fractured carpal bone, usually from a fall on the outstretched hand in a young adult. About 70 to 80% occur at the waist. Tenderness in the anatomical snuffbox, pain on axial loading of the thumb and tenderness of the scaphoid tubercle are the clinical clues. The dedicated scaphoid view (PA in ulnar deviation) elongates the bone. A significant fraction of scaphoid fractures are not visible on the first films, so the standard plan for a suspected fracture with negative films is thumb spica immobilization and either repeat films in about 10 to 14 days or early MRI. Because the main blood supply enters the distal pole and flows back toward the proximal pole, waist and proximal fractures risk avascular necrosis of the proximal pole (dense, sclerotic fragment) and nonunion.

Normal volar tilt of the distal radius is about 11 degrees and radial inclination about 22 degrees; a Colles fracture reverses the tilt and shortens the radius.

Elbow and shoulder

At the elbow, a visible posterior fat pad or raised anterior fat pad (sail sign) after trauma means an occult fracture: radial head in adults, supracondylar humerus in children. The anterior humeral line should cross the middle third of the capitellum and the radiocapitellar line should hit the capitellum on every view. Pair forearm injuries: Monteggia (proximal ulna fracture, radial head dislocation) and Galeazzi (distal radius fracture, DRUJ dislocation). Know the pediatric ossification order (CRITOE) so a normal center is not called a fragment.

At the shoulder, anterior dislocation dominates (head below the coracoid), with the Hill Sachs (posterolateral head impaction) and Bankart (anteroinferior glenoid) lesions. Posterior dislocation follows seizure or electric shock and shows the lightbulb sign; the axillary or Y view proves it.

Knee, ankle and foot

On the mortise view a medial clear space over about 4 mm means deltoid disruption and an unstable ankle. In a child the fifth metatarsal apophysis runs parallel to the shaft; a fracture runs across it.

Pediatric fractures and the growth plate

Children's bones are more pliable and their physes are weaker than their ligaments, so they bend, buckle and slip at the growth plate instead of spraining. The Salter Harris classification (mnemonic SALTR) describes physeal fractures: type I straight through the physis (Slipped), type II through the physis and a corner of the metaphysis (Above, the most common), type III through the physis and the epiphysis (Lower, intra articular), type IV through metaphysis, physis and epiphysis (Through), and type V a crush of the physis (Ruined, often recognized only later by growth arrest). The higher the number, the greater the risk of growth disturbance. Also know the torus (buckle), greenstick and toddler's (spiral distal tibia) fractures. Metaphyseal corner fractures, posterior rib fractures, fractures of different ages and fractures in a nonwalking child suggest nonaccidental trauma: document objectively and make the mandated report.

Section 5Trauma decision making in a station

The decision the examiner is really scoring

A trauma film station is a safety station dressed as an imaging station. Exams of this type generally reward a candidate who recognizes when the area must not be manipulated, protects the patient now, refers at the right speed and orders the right follow up imaging, all said aloud: an examiner cannot score a silent decision.

Who needs imaging after trauma

Before you can act on a film you must know when one is needed. For the neck, two validated decision rules are widely taught. The NEXUS criteria say that an alert patient can be cleared without imaging when all five are absent: posterior midline cervical tenderness, focal neurologic deficit, altered alertness, intoxication and a painful distracting injury. The Canadian C spine rule images any high risk patient (age 65 or older, dangerous mechanism such as a fall from about 1 m or five stairs, axial load, high speed or rollover collision, or extremity paresthesias); otherwise, if a low risk factor allows assessment (simple rear end collision, ambulatory, delayed onset, no midline tenderness) and the patient can actively rotate 45 degrees each way, no imaging is needed. Real risk calls for CT.

For the lower back, image after significant trauma, minor trauma in an older or osteoporotic patient, long term steroid use, or with neurologic deficit.

When a film must not be adjusted through

These findings are absolute contraindications to manipulating the involved region:

Relative situations call for modification rather than refusal: a healed, stable old compression fracture (low force methods, adjust other regions), a stable grade I slip (no thrust into the slipped segment), or a long healed extremity fracture. In each case say why the modification is safe and what you would watch for.

Immobilization and referral

For a suspected unstable cervical injury, keep the patient still with the head in neutral, apply a rigid collar if trained, do not let them walk out or drive, and call EMS; a neurologic deficit makes this a 911 call. A stable acute fracture without deficit gets protection and same day orthopedic or emergency evaluation. For limb fractures, document pulses, capillary refill, sensation and motor function before and after splinting; a pulseless limb or open fracture is an emergency.

Follow up imaging

• Suspected ligament injury, normal neutral films: flexion and extension laterals at 7 to 14 days if no fracture or deficit; MRI with neurologic signs.
• Occult fracture (scaphoid, femoral neck, stress): immobilize; MRI or repeat films in 10 to 14 days.
• Compression fracture of uncertain age or cause: MRI and DXA.
• Burst fracture: CT for canal compromise.
• Spondylolisthesis in a growing child: periodic standing laterals.

When the patient reports a problem

If the standardized patient reports new numbness or feels faint, stop, keep them still, reassess ABCs and neurologic status, call for help and say so aloud. Continuing the scripted task costs safety credit.

Words worth knowing