August 30, 2009

Parturition-Induced Pubic Diastasis

Anteroposterior view of the pelvis in a recently postpartum woman shows widening of the pubic symphysis > 1 cm (double-headed arrow).

Facts: Parturition-Induced Pubic Diastasis/Pelvic Dislocation
  • There is increased mobility of pubic symphysis and sacroiliac joints during pregnancy because of hormonal change
  • During delivery, a rapid forceful descent of fetal head against the pelvic ring can result in this injury
  • Patients experience immediate pain and audible snap during labor
  • Mostly require conservative treatment with a pelvic binder, lateral recumbency and analgesics. In few cases, surgical fixation is used.

Predisposing Factors
  • Multiparity
  • Forceps assisted delivery, shoulder dystocia
  • Maternal developmental dysplasia of the hip, prior pelvic trauma

  • Separation of pubic symphysis >1 cm
  • If separation >4 cm, usually associated with SI joint disruption
  • Patients may have sacral fractures, lumbosacral plexus injury, bladder/urethral injury

Kharrazi FD, Rodgers WB, Kennedy JG. Parturition-induced pelvic dislocation: a report of four cases. J Orthop Trauma 1997;11:277-281.

August 29, 2009

Step Lightly for Kids

"Treat kids with care:
Step lightly on the fluoroscopy pedal.
Stop and child-size the technique.
Consider ultrasound or, when applicable, MRI guidance."

On their website "", slide presentations, checklists, outlines and patient brochures are available for free download.

Above image from

August 27, 2009

Frontal Sinus Fracture

Axial CT image shows a depressed, comminuted fracture of the anterior wall of the frontal sinus. There is small hemosinus. The posterior wall is intact.
3D CT image beautifully demonstrates depression of the frontal sinus.

Facts: Frontal Sinus Fracture
  • Because of density, thickness and arched configuration of the anterior wall of frontal sinus, a fracture requires considerable force
  • Isolated frontal sinus fracture uncommon. Most fractures occur with other midface or intracranial injuries
  • Most common cause is blunt trauma
  • Late complications include aesthetic deformity, infection (sinus, intracranial), CSF leakage.
  • Anterior wall fracture
  • Posterior wall fracture
  • Combined anterior and posterior wall fracture
  • Decision for surgical exploration based on presence of displacement, depression, posterior wall involvement, CSF leakage, nasofrontal duct involvement
  • CT is the current gold standard for diagnosis
  • Look for fracture comminution, depression, involvement of posterior wall, degree of displacement and nasofrontal duct injury
  • Fracture extending to the base of frontal sinus and anterior ethmoid complex has a high likelihood of nasofrontal duct obstruction
  • Some surgeons advocate surgical management if a posterior wall fracture displaces more than one both width (higher likelihood of dural tear, CSF leak).
Thaller SR, McDonald WS. Facial trauma. Informa Health Care; 2004.
Joshi AS. Frontal sinus fracture. Emedicine, September 15, 2008.

August 24, 2009

Radiologic Miss and Malpractice

Error in Interpretation of Radiologic Studies

  1. True miss: an obvious abnormal finding is not seen
  2. True error in judgment: an abnormal (or normal) finding is not interpreted correctly
How Frequent Radiologists Make Error?
  • Radiologists are far less than perfect in interpreting radiologic studies
  • As many as 30% of abnormal findings are missed
  • Radiologists disgree (either with themselves or with their peers) as often as 50% of the time
  • However, the results shown above do not necessarily reflect the degree to which patient care is jeopardized. Some radiologic errors may translate into mismanagement of a patient or injury, many others are insignificant.
Does Radiologic Miss Constitute Malpractice?
  • "Malpractice suits are based on assumption that the doctor violated his/her duty to a patient, resulting in injury and the patient should be compensated by the offending physician"
  • In a malpractice case, it must be shown to the court that 1) the diagnosis was wrong, and 2) error was a result of 'negligence'
  • Radiologic miss may or may not involve negligence. Unfortunately, there is no guidelines yet to easily distinguish this true negligence from simple error. The way it works in courts is that negligence "no reasonable radiologist in similar circumstances would have made the error"
  • Radiologists have a duty to interpret radiologic studies reasonably but not necessarily perfectly
Berlin L. Malpractice issues in radiology. 3rd edition, 2009.

August 21, 2009

Importance of Visualization of Normal Acetabular Landmarks

Author: Aasis Unnanantana, M.D.

Figure 1: Pelvic radiograph (AP) shows a displaced left femoral neck fracture (arrow) in an old woman who fell.

Do you see anything else?

What normal bony structures do you expect to see in the acetabulum?
  • Iliopectineal line
  • Ilioischial line (Kohler's line)
  • Acetabular roof (dome) or sourcil
  • Radiographic teardrop
  • Anterior wall
  • Posterior wall

In this case, there is bowel gas overlying the left hemipelvis - making it difficult to assess. However, normal anatomic landmarks of the left acetabulum and pelvis are not visualized.

Same figure, with an outline of "non-visualized" acetabulum and left hemipelvis due to involvement of lytic metastasis. The patient also has a history of known renal cell carcinoma. Findings were confirmed on a CT scan.

Take Home Messages
  • When normal radiographic features of acetabulum are not visualized on conventional radiographs, further imaging should be considered (e.g. additional radiographic views such as obliques, or CT) to assess the particular structures.
  • Be aware of "satisfaction of search".
Barrack RL, Booth Jr RE, Lonner JH, et al (eds). Orthopedic Knowledge Update: Hip and Knee Reconstruction 3. 2006
Line art: Rathachai Kaewlai, MD

About Guest Author: Dr. Aasis Unnanantana, MD, is a clinical fellow in orthopedics (Metabolic Bone Diseases Service) at the Hospital for Special Surgery, Cornell University, New York, NY. He is a member of orthopedic instructor at Siriraj Hospital, Mahidol University, Bangkok, Thailand.

August 18, 2009

Aortic Intramural Hematoma (IMH)

Figure 1: Contrast-enhanced CT image shows thickening of the aortic wall at the anteromedial aspect of the descending aorta (arrow). There is linear calcification, indicating atherosclerosis.

Figure 2: Axial CT without IV contrast at the same level shows the area of aortic wall thickening as a slightly hyperdense wall of the aorta (arrow). The linear calcification (arrowhead) is indeed located close to the aortic lumen (likely in the intima), therefore the wall thickening is 'subintimal' or 'intramural'. The nonenhanced CT helps in the way that if one looks only at contrast-enhanced images, one might think that the findings represent atherosclerotic change of the aorta (with calcification and intraluminal thrombus) and defers the diagnosis of IMH.

Facts: Intramural Hematoma (IMH)
  • Less common variant of aortic dissection
  • Hemorrhage occurs within aortic wall without initial intimal disruption believed to be due to medial degeneration predisposing the vasa vasorum toward hemorrhage
  • Increasingly recognized with the use of CT imaging (in the past, it is believed to be underdiagnosed on angiography because there is no intimal flap)
  • Limited data suggests a similar clinical course and mortality rate to acute aortic dissection
  • Common presentations = chest pain and interscapular back pain (similar to aortic dissection)
  • Unlike aortic dissection, IMH occurs in men equal to women, with absence of traditional risk factors for dissection (e.g. bicuspid aortic valve, Marfan syndrome, collagen vascular disease)
Imaging Features
  • Focal or diffuse, smooth thickening of the aortic wall
  • No intimal flap or any communication between aortic lumen and IMH
  • Intimal calcium (if present) is superficial (closer to lumen) to the hematoma
It May Be Confused With:
  • Aortic dissection with thrombosed false lumen
  • Penetrating atherosclerotic ulcer - usually irregular thickening of the aortic wall
  • Aortic aneurysm with intraluminal thrombus - if intimal calcium is present, it will be deeper to the hematoma. The thrombus usually is irregular and rough - not smooth.
Our case - Intramural hematoma of the descending thoracic aorta.

Sawhney NS, DeMaria AN, Blanchard DG. Aortic intramural hematoma. Chest 2001;120:1340-1346.

August 15, 2009

Mitral Annulus Calcification

PA and lateral chest radiographs of an 80-year-old woman show an inverted "C"-shaped calcification over the heart in a characteristic location of the mitral valve.

Facts: Mitral Annulus Calcification
  • Noninflammatory chronic degenerative process
  • Mitral valve ring (annulus) may calcify in older individuals (>60 years)
  • Women more common than men
Pattern on Imaging
  • Small calcium forms in or below mitral annulus at junction between ventricular myocardium and posterior mitral leaflet
  • Severe disease resembles the letter J, O, or reversed C
Clinical Significance
  • Little clinical significance in most cases
  • May grow into ventricular myocardium to produce heart block, into mitral leaflets to cause mitral regurgitation and stenosis, through endocardium to cause small systemic emboli
  • Mitral annulus calcification in the elderly is an independent risk factor of developing stroke

Miller SW, Boxt LM, Abbara S. Cardiac Imaging the Requisites. 2009.

August 12, 2009

Solitary Vertebral Metastasis Involving the Spinous Process

Figure 1: Chest radiograph (cropped to the thoraco-lumbar junction) shows absence of a spinous process of the T11 vertebra (arrow) in a patient with known hepatocellular carcinoma.
Figure 2: Sagittal-reformatted CT image shows an enhancing soft tissue mass (arrows) involving the spinous process of T11 with epidural extension, causing narrowing of the central spinal canal.

Facts: Spinal Metastasis
  • Spine is the most common site of bone metastasis
  • 10% - 30% of patients with cancer develop symptomatic spinal metastasis
  • 12% - 20% of malignancies present with spinal metastasis
  • Most spinal metastases are extradural lesions that initially start as osseous lesions in a portion of the vertebra
  • Breast, lung, prostate, hemopoietic (lymphoma, multiple myeloma), and renal tumors are common ones metastasizing to the spine
Diagnosis of Solitary Spinal Metastasis
  • Biopsy is mandatory if the isolated spinal lesion is unknown, even in the face of a distant history of a primary malignancy (because it may represent a new primary)
  • Biopsy may be deferred if there is a known history of metastatic disease with multiple lesions -- new spinal lesion may be treated without the need for further histologic evaluation
  • Imaging-guided (fluoroscopy or CT) biopsy is preferable. Better yield for lytic lesion versus sclerotic lesion.
Treatment Plan
  • To help planning the management, detailed imaging study and description is needed. Isolated spinal tumor may be resected by intralesional excision (piecemeal removal of the tumor), or en bloc resection (removal of tumor mass including a cuff of healthy tissue encasing the tumor).
  • In this regards, it is important to describe lesions as "intracomparmental" (i.e. involving vertebral body only, body with pedicle extension, body with pedicle and lamina extension), "extracompartmental" (i.e. with epidural extension, paravertebral extension, 2-3 vertebrae), or "multiple skip lesions"
Our case - isolated metastatic hepatocellular carcinoma to the posterior element of the thoracic spine.

Donthineni R. Diagnosis and staging of spine tumors. Orthop Clin N Am 2009;40:1-7.

August 9, 2009

Azygos Fissure

Azygos Fissure
  • Normal variant, found in 1% of anatomic specimen and about 0.4% of chest radiographs
  • Right posterior cardinal vein (precursor of azygos vein) fails to migrate over lung apex, instead penetrating the lung and carrying pleural layers with it.
  • Two folds of parietal and visceral pleural layers create a "fissure"
  • Enclosed lung is a part of apical or posterior segment of the right upper lobe

  • Fine, convex line crosses the apex of the right lung.
  • Azygos vein visible in the lowermost portion of the fissure "teardrop" shape.
  • Absence of azygos vein at the right tracheobronchial angle.

Mimics of Azygos Fissure
  • Scars
  • Walls of bullae
  • Displaced fissures
  • Supernumerary fissures

Mata J, Caceres J, Alegret X, Coscojuela P, De Marcos JA. Imaging of the azygos lobe: normal anatomy and variations. AJR 1991;156:931-937.

August 6, 2009

Autoimmune Pancreatitis

Fig. 1: Axial CT image of a 61-year-old man with abdominal pain shows mild diffuse enlargement of the pancreas, loss of pancreatic lobulation and minimal peripancreatic fat stranding (arrows).

Fig. 2: An ERCP image (injection of pancreatic duct) shows irregular narrowing of the pancreatic duct (arrowheads).

  • Relatively new, rare disease first described in 1995 by Yoshida et al.
  • Chronic pancreatitis characterized by autoimmune inflammatory process (lymphocytic infiltrates) with associated fibrosis of pancreas
  • Associated with immunologic abnormalities: hypergammaglobulinemia, elevated serum IgG4 levels and autoantibodies against carbonic anhydrase and lactoferrin
  • Pathology shows diffusely indurated and firm pancreas, with periductal lymphocytic and plasma cell infiltrates
  • Involvement of the gallbladder, bile ducts, kidney, lung and salivary glands has been described

  • 5-6% of all patients with chronic pancreatitis
  • Men > women, most are > 50 years
  • Mostly associated with other autoimmune disease e.g. rheumatoid arthritis, Sjogren's syndrome, inflammatory bowel disease
  • Responsive to steroid

  • On CT, diffuse pancreatic enlargement, enhanced peripheral rim of hypoattenuation "halo", low attenuation "mass" in pancreatic head, homogeneous attenuation and loss of lobularity
  • Minimal peripancreatic fat stranding
  • Involution of pancreatic tail in long-standing disease
  • On ERCP, focal, diffuse or segmental pancreatic ductal narrowing, disappearance of right-angled branches
Finkelberg DL, Sahani D, Deshpande V, et al. Autoimmune pancreatitis. N Eng J Med 2006;355:2670-2676.

August 3, 2009

CT Angiography "Spot Sign"

An above image panel shows an intracerebral hemorrhage (blue arrows) in the right frontal lobe on an unenhanced image; a spot sign (yellow arrow) on a CTA source image; puddling of contrast extravasation (red arrowheads and yellow arrow) on an enhanced image. Unenhanced follow-up CT 6 hours later shows hematoma expansion (blue arrows). The patient underwent hematoma evacuation. Also noted on these images is subdural and subarachnoid hemorrhage.

Intracerebral Hemorrhage: Facts
  • 10% - 30% of all stroke
  • Outcome worse than ischemic stroke, up to 50% mortality at 30 days
  • Causes: hypertension, amyloid angiopathy and anticoagulation
  • Pathomechanism - believed to be due to parenchymal microaneurysm with rupture
Outcome Predictors
  • Hematoma size
  • Hematoma expansion (definition: increase of 33-50% or absolute change in volume between 12.5 to 20 mL of hematoma). Known risks of expansion include antecedent warfarin use and ultra-early presentation
CT Angiography "Spot Sign"
  • Definition: one or more 1- to 2-mm foci of enhancement within the hematoma on CT angiography source images
  • On a routine enhanced CT scan, if there is an enlargement of contrast density - this is called "contrast extravasation"
  • The sign has been described in primary intracerebral hemorrhage; but it could be seen - and termed "spot sign mimics" in cases of secondary intracerebral hemorrhage (i.e. aneurysm, calcification, etc.)
  • Independent predictor of hematoma expansion
1. Goldstein JN, Fazen LE, Snider R, et al. Contrast extravasation on CT angiography predicts hematoma expansion in intracerebral hemorrhage. Neurology 2007;68:889-894.

2. Wada R, Aviv RI, Fox AJ, et al. CT angiography "spot sign" predicts hematoma expansion in acute intracerebral hemorrhage. Stroke 2007;38:1257-1262.