Missed Rad Injuries Lin

Missed Radiologic Injuries

Michelle Lin, MD Associate Residency Director, UCSF-SFGH Emergency Medicine Residency

Assistant Clinical Professor of Medicine, UC San Francisco San Francisco General Hospital, Emergency Services

[email protected] MEDICOLEGAL SIGNIFICANCE 1. Missed orthopedic injuries, such as fractures and dislocations, comprise the largest source of

malpractice claims in the emergency department, according to a study conducted by the American College of Emergency Physicians during the period of 1974-1985. [44% pelvis / vertebra, 22% extremity, 14% hand]

2. Various studies corroborate that these injuries comprise a significant # of medical claims.

• Pennsylvania Hospital Insurance Company (1977-1981): 19% of 200 ED malpractice cases were due to “misinterpretation of radiographs.” (Trautlein et al.)

• Chicago (1975-1994): Retrospective study of 18860 malpractice claims showed 12% involved radiology cases, of which missed diagnoses was the #1 cause of litigation. (Berlin and Berlin)

• Massachusetts Joint Underwriters Association: Missed fractures comprised 20% (during 1980-1987) and 10% (1988-1990) of malpractice claims. (Karcz et al, 1993)

3. The majority of malpractice claims on misread radiographs are those whose radiographs were

taken during “off” hours. • 63% malpractice suits occur from incidents during 6 pm-1 am (weekends) and midnight-

7 am (weekdays) • ED radiograph interpretations during non-business hours are often provided by EP’s. • Over 80% acute care hospitals do not have 24/7 radiologist interpretation available. • Radiographic interpretation discrepancy rate between an EP and radiologist = 2-11%.

(Lufkin et al, Robinson et al, Scott et al) ERRORS IN RADIOGRAPH INTERPRETATION Commonly missed, high-risk injuries on radiographs can be

remembered by using my mnemonic “DOH.” (similar to what your response might be when a patient is recalled for your incorrect radiology interpretation…)

Ortho Radiography (Lin) 2

D islocations O ccult fracture H alf of injuries missed Wrist Scapholunate DS Scaphoid Galeazzi Perilunate DL and Lunate DL Triquetrum Distal Radius Fx + Carpal Injury Elbow Radial head DL Radial head Monteggia Pelvis/ Hip Hip DL Femoral neck Another ring fracture Sacrum Acetabulum Knee Knee DL Tibial plateau Maisonneuve Segond Patella Foot Lisfranc injury Calcaneus Thoracolumbar + Calcaneus fx Talus Abbreviations: “DL” – dislocation, “DS” – dissociation, “Fx” – fracture

WRIST

Normal Anatomy

PA View (R Wrist): 3 smooth arcs

along carpals Intercarpal

distance < 3 mm

PA View

Lateral View (Right Wrist): Alignment: Smooth

articulation of distal radius to lunate, lunate to capitate, and capitate to 3rd metacarpal

Scapholunate angle < 30-60 degrees

Lateral View


D islocation 1. SCAPHOLUNATE DISSOCIATION

Most common and significant ligamentous injury of wrist. Rotatory subluxation of scaphoid into more transverse

orientation. Mechanism: Fall on outstretched hand (FOOSH) Xray: PA view: >4 mm widening of scapholunate space

(“Terry Thomas sign”) PA view: Scaphoid has “signet ring sign” Lateral view: Scapholunate angle > 60 deg

PA View of R Wrist 2. PERILUNATE DISLOCATION

Mechanism: Hyperextension of the wrist Xray: Lateral view: Capitate is not vertically aligned with

the lunate and radius. PA view: Smooth middle arc alignment of carpal

bones is disrupted. Complications: Median nerve injury, SLAC

Lateral View of R Wrist

3. LUNATE DISLOCATION Mechanism: Fall backwards on outstretched hand Xray: Lateral view: Lunate is rotated out of alignment into

“spilled teacup” position PA view: Smooth proximal arc of carpal bones is disrupted PA view: Lunate appears triangular (rather than

quadrilateral) Complication: Median nerve injury, SLAC

Lateral View of R Wrist O ccult Fracture 1. SCAPHOID FRACTURE

2nd most common fractured bone of the wrist [#1=distal radius] At a teaching hospital ED, the “miss rate” was greatest for

scaphoid fractures (13%) (Freed and Shields) Mechanism: FOOSH Exam: Tenderness to “snuffbox” area of wrist Xray: Normal in up to 20% cases (Waeckerle) Ulnar deviated AP View Consider obtaining additional scaphoid views of R Wrist


Teaching Pearl: Apply thumb spica splint to all wrists with snuffbox tenderness regardless of normal xrays

Complication: Avascular necrosis (AVN) Nonunion rate increases 5-45% when treatment is delayed > 4 weeks (Langhoff and

Andersen) SLAC (Scapholunate Advanced Collapse) – Scaphoid and/or lunate undergoes AVN and

collapses 2. TRIQUETRUM FRACTURE

Accounts for 10% of carpal bone fractures Mechanism: FOOSH Exam: Tenderness to ulnar aspect of dorsal wrist Xray: Most easily seen on lateral since triquetrum is most

dorsal carpal bone

Oblique View of R Wrist

Oblique View of R Wrist H alf of Injuries Missed 1. GALEAZZI FRACTURE

Distal-third fracture of the radius AND disruption of distal radioulnar joint (DRUJ) Mechanism: FOOSH with forearm hyperpronated Signs of DRUJ: Lateral view: Ulna does not overlie radius Lateral view: Ulnar styloid is not aligned with dorsal triquetrum PA view: Ulnar styloid fracture PA view: Widening of DRUJ Complication: Chronic disability when DRUJ disruption is

missed > 10 wks

Lateral view of R forearm

2. DISTAL RADIUS FX + CARPAL INJURY Because of the same FOOSH mechanism of injury, scapholunate dissociation may also be

present. In a small retrospective study of 52 patients, 69% of distal radius fractures were associated with scapholunate dissociation (Lee et al.)

Radial styloid fractures are associated with scaphoid / lunate fractures & ligamentous injury.


ELBOW Normal Anatomy Capitellum: Portion of distal humerus which articulates with the radial head

LATERAL VIEW Fat pads: Collections of fat tissue

adjacent to elbow joint capsule (appears black on xrays)

Anterior fat pad Can be normal If displaced and elevated, is

pathologic (sail sign) Posterior fat pad Always abnormal if visualized

AP VIEW Lines: Misalignment of normal

structures can be a subtle indicator of a fracture or dislocation

Radiocapitellate line: On both the AP and lateral views, a longitudinal line drawn

through the midshaft radius should bisect the capitellum. An abnormal alignment suggests a radial head dislocation.

Anterior humeral line: On the lateral view, a longitudinal line drawn along the anterior

aspect of the humerus should bisect the capitellum. An abnormal alignment suggests a supracondylar fracture.


D islocation RADIAL HEAD DISLOCATION

When identified, must look for a proximal ulnar fracture (see “Monteggia Fracture”)

O ccult Fracture RADIAL HEAD FRACTURE

At a teaching hospital ED, the “miss rate” was 2nd greatest for elbow fractures at 10.8%. In adults, these fractures were primarily missed radial head fractures. (Freed and Shields)

Mechanism: FOOSH Lateral view of R elbow

Xray: Cortical break in the radial head may be very subtle or even absent in a nondisplaced fx Large anterior fat pad (“Sail sign”) Any posterior fat pad In the study by Freed and Shields: >80% had an associated fat pad and >40% had ONLY

a fat pad sign as indicator of a fracture. Pearl: Sling patients with elbow pain and abnormal fat pads despite no obvious fracture.

H alf of Injuries Missed MONTEGGIA FRACTURE

Proximal ulna fracture AND radial head dislocation Missed in 50% pediatric population – importance of

alignment of radiocapitellate line (Gleeson and Beattie)

Mechanism: FOOSH with rotational forces Xray: Obvious proximal ulna fracture Lateral view of R elbow Misalignment of radiocapitellate line Pearl: Beware of diagnosis of isolated proximal ulna fx!


PELVIS / HIP Normal anatomy AP View D islocation HIP DISLOCATION

Most commonly posterior from dashboard injuries in MVA’s. Posterior: Affected leg is shortened and internally rotated Anterior: Aftected leg is shortened and externally rotated Since hip dislocations are associated with femoral head /

acetabular fx’s, consider a CT for unsuccessful reduction to assess for intraarticular bone fragments.

AP view of L Hip

O ccult Fracture 1. FEMORAL NECK FRACTURE

Most commonly missed hip fracture Sometimes elderly patients can weight-bear despite a fx. Mechanism: From direct blunt trauma (fall) Xray:

Can be very subtle Cortical disruption or impacted hyperlucency Loss of smooth cortical transition from femoral

neck to head. Trabecular disruption AP view of R hip

Delay in Diagnosis: Radiographically occult hip fx’s occur in 2-9%. One study had 16/825 missed hip fractures. 15/16 were initially nondisplaced but

became displaced secondary to the delayed diagnosis. (Parker) Additional Imaging: Consider MRI (CT is ok alterative, but less sensitive) if still clinically

suspicious because of the risk of missing a nondisplaced fracture and having the patient return with a displaced fracture. MRI sensitivity and specificity = 100%.


2. SACRAL FRACTURE In one study: 72% of sacral alar fractures were missed

initially. (Jackson et al.) Xray: Subtle break in smooth sacral alar lines Additional Imaging: Pelvic “outlet views” improve visualization of the

sacrum and rami. CT required to assess severity of sacral fracture and

additional fx’s.

AP view of sacrum 3. ACETABULAR FRACTURE

Anterior acetabular fracture: Detected by break in iliopubic line Posterior acetabular fracture: Detected by a break in the

ilioischial line; look specifically “behind” superimposed femoral head

Additional Imaging: Can get additional Judet views to assess for clinically

suspicious cases Requires CT assessment to assess severity and because 40% of associated intraarticular bone fragments and 50% of femoral head fractures are missed initially. (Lipman) AP View of R hip

H alf of Injuries Missed PELVIC RING DISRUPTION

Because of the inflexible, ring-like structure of the pelvis, pelvic bone injuries are often found in multiples. In addition to the already mentioned injuries, also beware of subtle rami fractures and sacroiliac dissociation.


KNEE Normal Anatomy AP View

Lateral View


D islocation KNEE DISLOCATION

Not a subtle clinical or radiographic finding 40% have associated popliteal artery injury

regardless of pedal pulses and reducibility. Requires angiography Lateral view of

R knee O ccult Fracture 1. TIBIAL PLATEAU FRACTURE

32% of all knee fractures Mechanism: Valgus force with axial load (knee vs. car bumper) Sensitivity of radiographs: 79% for 2-view, 85% for 4-view

(Gray et al.) Pearl: When a patient with knee pain from blunt trauma can not

walk, be sure that oblique views are obtained to assess for a tibial plateau fracture. Consider CT despite radiographically negative findings in a patient.

Additional Imaging: AP view of R knee Oblique views (plain radiographs), CT to assess for severity

2. SEGOND FRACTURE

Small proximal lateral tibial avulsion fx Often associated with an ACL tear

AP View of L knee

3. PATELLA FRACTURE

40% of all knee fractures Additional Imaging: “Sunrise” view

Lateral View of R knee

H alf of Injuries Missed MAISONNEUVE FRACTURE

Proximal fibula fracture AND medial malleolus (or deltoid ligament) fracture Mechanism: Abduction and external rotation of ankle

PLUS

AP View of R Knee AP View of R Ankle


FOOT Normal Anatomy

Lateral View

PA View PA View: The medial edges of the 2nd

metatarsal and 2nd cuneiform should align. Lateral View:

Bohler’s angle (generated by a line bordering the superior aspect of the posterior calcaneal tuberosity and a line connecting the superior subtalar articular surface and superior aspect of the anterior calcaneal process) normally is 20-40 degrees.

A Bohler’s angle < 20 degrees implies an occult calcaneal fracture.

Oblique View Oblique View: The medial edges of the 3rd

metatarsal and 3rd cuneiform should align.


D islocation LISFRANC INJURY

Tarsal-metatarsal (MT) fracture/dislocation pattern 20% are initially missed (Goossens and DeStoop) LisFranc ligament: Attaches 2nd MT base to 1st cuneiform. Xray: Fracture of 2nd metatarsal base or Lisfranc

ligament and subsequent dislocation of MT #2-5 from the midfoot

Pearl: An avulsion fracture of the 2nd metatarsal base alone is a LisFranc fracture DESPITE a normal alignment of the metacarpals with the tarsal bones, because the AP view of R foot LisFranc ligament inserts at its base.

Complications: Compartment syndrome

O ccult Fracture 1. CALCANEUS FRACTURE

At a teaching hospital ED, the “miss rate” was 3rd greatest for calcaneal fractures at 10%. (Freed and Shields)

Most commonly fractured tarsal bone Mechanism: Often from fall on heels from a height Xray: A Bohler’s angle < 20 degrees suggests a fracture. Additional Imaging: Consider obtaining a “calcaneal view” Often requires CT imaging to assess fragments Lateral View of L foot Complication: Compartment syndrome

2. TALUS FRACTURE

Second most commonly fracture tarsal bone The neck is the most common location of a talar fracture. Mechanism: Excessive dorsiflexion of ankle Xray: Can be subtle cortical break on lateral view Complications of neck fracture: Avascular necrosis,

subchondral collapse, and degenerative arthritis Lateral View of R foot

H alf of Injuries Missed CALCANEUS FRACTURES:

10% associated with THORACOLUMBAR FRACTURE because of load on axial skeleton when landing on the heels

Lateral View of Lumbar Spine


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Missed Rad Injuries Lin