Scapholunate Advanced Collapse (SLAC-wrist)

Figure: Frontal radiograph of the wrist shows marked degenerative change (joint space narrowing and subchondral sclerosis) of the radioscaphoid joint (yellow arrowheads), widening of the scapholunate space, and proximal migration of the capitate (C) filling in this widened space. The radiolunate joint (red arrowheads) is spared by degeneration.

Scapholunate Degeneration

• Insufficiency of scapholunate and radioscapholunate ligaments, causing increased mobility of the scaphoid on the radius
• Abnormal load to the capitate upon lunate, then capitate enters the widened scapholunate joint space and approximates distal radius
• Three stages: the third stage is called "SLAC wrist", in which the capitates enters the scapholunate gap and approaches the distal radius. The radiocarpal joint at lunate is spared by degeneration.

Etiology

CPPD deposition disease, rheumatoid arthritis, trauma, neuropathy, amyloid deposition

Reference:

1. Stabler A, Heuck A, Reiser M. Imaging of the hand: degeneration, impingement and overuse. Eur J Radiol 1997;25:118-128.

Submandibular Sialadenitis with Abscess

Coronal and sagittal CT images show an enlarged left submandibular gland with two well-defined rim enhancing fluid collections in the anterior aspect of the gland, representing abscesses. There is adjacent subcutaneous fat stranding.

Sialadenitis

• Most common salivary gland abnormality is infection, either bacterial or viral
• Bacterial infection ascends from oral cavity. Most common pathogens are S. aureus, S. viridans, H. influenza
• Most common viral infection is mump
• Most common site = parotid > submandibular gland
• Predisposing factors are dehydration, radiation, immunosuppression
• Other causes of sialadenitis include inflammation (sialolithiasis, radiation), autoimmune (Sjogren, lupus), granulomatous (TB), drug, etc.

Sialadenitis vs Abscess

• Sialadenitis is treated with antibiotics, while abscess usually needs surgery
• Abscess may spread to deep neck spaces and progress to Ludwig angina
• CT can differentiate the two entities. Abscess is seen as localized low attenuation, walled-off region in contrast to dense, enhanced gland
• CT can show calcified sialolithiasis, and in some cases noncalcified sialolithiasis as a cause of duct obstruction

References:

1. Yoskovitch A. Submandibular sialadenitis/sialadenosis. emedicine Jul 23, 2008.

2. Silvers AR, Som PM. Salivary glands. Radiol Clin North Am 1998;36:941-966.

Ankle Mortise Radiographic View

Figure 1: "Inadequate mortise view of the right ankle" in a patient with lateral malleolar fracture and torn deltoid ligament. Note that the radiograph was taken without adequate internal rotation of the ankle joint. The entire tibiotalar joint space is not clearly shown, particularly the lateral clear space. On this image, the medial clear space (arrowheads) appears normal.

Figure 2: "Adequate" mortise view of the same patient shows disruption of the deltoid ligament, which is shown as widening of the medial clear space (arrowheads).

Ankle Mortise View

• Anteroposterior view with ankle internally rotated 15 to 20 degrees
• Considered adequate if - tibiotalar joint well demonstrated entirely and medial/lateral clear spaces are open
• Used to assess - tibiotalar articular surface, integrity of ankle mortise, and medial/lateral clear spaces

Normal

• Entire tibiotalar joint space is uniform in width
• Normal overlap between distal tibia and fibula about 1 mm, or a little wider than tibiotalar joint space

Our case emphasizes the importance of determining the adequacy of radiographic techniques before interpreting radiographs as normal. In our case, findings are consistent with a supination-external rotation (SER) type of ankle fracture.

Reference:

Schwartz DT, Reisdorff EJ. Emergency Radiology. McGraw-Hill Professional, 1999.

Capitellar Osteochondritis

A 10 yr old gymnast presented with right elbow pain

Timing of ossification center at elbow

CRITOE
Capitellum appears by 8 months

Radial head 3-4 yrs

Internal (medial) epicondyle 5 yrs

Trochlea 7 yrs

Olecranon 9 yrs

External (lateral) epicondyle 11 yrs

Capitellar osteochondritis

• Results from overuse of elbow causing subchondral reactive process and loosening of cartilage and bone
• Usually occurs at anterior surface of capitellum
• Imaging findings show flattening of capitellar surface, or visible lucent zone of defect and sometimes can demonstrate intrarticular fragment of loose bodies.
• Unstable lesions include large size (typically > 1 cm), cystic lesion beneath the osteochondrotic site, containing loose granulation tissue or loose fragement, fluid insinuating beneath the fragment

Reference Elbow In: Stoller DW, Tirman PFJ, Bredella MA . in Diagnostic Imaging: Orthopaedics. Amirsys.2003.

Inferior Vena Cava (IVC) Filter Fracture

Figure 1: Abdominal radiograph shows that one of the legs (arrows) of the IVC filter is pointed away from the expected IVC lumen.

Figure 2: Axial CT image confirms that one of the legs (arrow) of the IVC filter has migrated out of the IVC wall into an adjacent tissue.

Fracture of IVC Filter Element

If the fragment migrates to adjacent tissues

- Asymptomatic patient: no treatment necessary

- Symptomatic patient: confirm location with CT scan and consider surgical removal if feasible

If fracture results in compromise of filter function: place a second filter

Reference:

Kaufman JA. Vena Caval Filters. In: Kandarpa K and Aruny JE, eds. Handbook of interventional radiologic procedures. 3rd ed. 2002

Estimate CT Radiation Exposure

Figure 1: A screenshot of "Dose Report" showing three series of a pelvic CT scan, scan range, CT dose index (mGy), dose linear product (DLP, mGy-cm). A total exam DLP is automatically calculated (in yellow circle). From the DLP, we can calculate an effective dose by multiplying it with an E/DLP conversion coefficient. The conversion coefficients vary from one area to another.

Figure 2: A table showing E/DLP conversion coefficients of five body regions, and typical mean effective doses and dose ranges from an investigation performed in British Columbia, Canada in 2004.

In our example, the total DLP was 555.78, and it was a pelvic CT scan (conversion coefficient = 0.019).

Effective dose (mSv) = DLP x E/DLP conversion coefficient

= 555.78 x 0.019

= 10.56

Reminder: Natural effective dose of radiation received by general population = 3-4 mSv per year

Related posts:

• Radiation risk at a given effective dose range.
• Understanding what is an effective dose.

Another option to calculate an effective dose and cancer risk is to do it online, for example, a website www.XrayRisk.com

Reference:

1. Aldrich JE, Bilawich A, Mayo JR. Radiation doses to patients receiving computed tomography examinations in British Columbia. Can Assoc Radiol J 2005;57:79-85.

2. European Commission. European guidelines on quality criteria for computed tomography. EUR 16262 EN. Luxembourg: Office for Official Publication of the European Communities; 2000.

RiTradiology Celebrating 11,111 visitors

"Illumination" by Tanop Srisuwan, MD

We are celebrating our 11,111 visitors on June 12, 2009 with a certification from Health On the Net (HON) Foundation and a couple new features you may be interested in:

• "RiT ILLUMINATIONS" is a new section showcasing non-radiologic pictures. The very first picture on this section is shown above and a regular posting is on the right sidebar on the main page (upper right corner). Pictures are acquired by editor's solicitation and it is now open for submission from anyone interested.
• "ShareThis". Now you can share any post you like with friends via email, AIM, social bookmarking and networking (i.e. Facebook, MySpace, Digg, Delicious, Twitter, etc.). Simply click the link 'sharethis' on the bottom of the post.

Check them out and thanks for subscribing to RiT!

"Vertebra Plana-Like" Lesion

Figs 1&2: Sagittal MR image (T1 post contrast) and coronal-reformatted CT image of the thoracic spine of a 14-year-old boy show complete collapse (arrows) of the mid thoracic vertebral body, preserved adjacent discs and enhancing soft tissues around the affected vertebral body extending into the epidural space (arrowheads).

Vertebra Plana

• Collapse of one vertebral body
• Normal adjacent intervertebral disks
• Height of the intervertebral space increased by at least 1/3 compared to normal
• Increased density of the collapsed vertebra

Etiology

• Strict criteria above apply to the diagnosis of eosinophilic granuloma, considered the most frequent benign lesion causing vertebra plana
• Other causes include: primary tumor (e.g. Ewing sarcoma, osteosarcoma, lymphoma), and metastasis, trauma and chronic osteomyelitis

Benign or Malignant?

• Clinical and radiographic course typically allows the physician to differentiate eosinophilic granuloma from other diagnoses that require diagnostic vertebral biopsy
• Using criteria based on studies of adult with compression fractures (differentiating benign from malignant compression fractures) may be helpful. The following MR findings were shown to be suggestive of malignancy: involvement of pedicle, irregular nodular paravertebral soft tissue lesion, marked and heterogeneous enhancement pattern.

Our case: metastatic round cell tumor to the spine causing "vertebra plana-like" appearance

References:
1. Baghaie M, Gillet P, Dondelinger RF, et al. Vertebra plana: benign or malignant lesion? Pediatr Radiol 1996;26:431-433.
2. Ippolito E, Farsetti P, Tudisco C. Vertebra plana. Long-term follow-up in five patients. J Bone Joint Surg Am 1984;66:1364-1368.
3. Shih TT, Huang K, Li Y. Solitary vertebral collapse: distinction between benign and malignant causes using MR patterns. J Magn Reson Imaging 1999;9:635-642.

Persistent Left Superior Vena Cava (SVC)

Fig. 1: Portable chest radiograph shows a right PICC line coursing from the right arm to the left side of the mediastinum (arrows).
Fig. 2: Coronal chest CT image performed with injection of the right antecubital vein shows dense contrast in the right axillary, subclavian, left brachiocephalic vein to the left SVC (arrowheads). There is no right SVC.

Persistent Left SVC

• Persistence of left anterior cardinal vein
• 0.3% of normal population; 4.4% in patients with congenital heart disease
• In most cases, the right SVC is also present (82% - 90%) (i.e. double SVC)
• Left SVC courses lateral to the aortic arch, main pulmonary artery, anterior to the left hilum and typically enters the coronary sinus that drains into the right atrium
• In some cases, left SVC enters the left atrium. Left SVC draining into the left atrium is highly associated with intracardiac defects (commonly ASD)

Significance of left SVC

• Need to know before performing SVC-pulmonary artery anastomosis
• Need to know before performing open heart operation

Reference:

1. Shumacker HB, King H, Waldhausen JA. The persistent left superior vena cava. Surgical implications, with special reference to caval drainage into the left atrium. Ann Surg 1967;165:797-805.

2. Webb WR, Gamsu G, Speckman JM, et al. Computed tomographic demonstration of mediastinal venous anomalies. AJR 1982;139:157-161.

Paraaortic Nodal Metastasis from Testicular Cancer

Fig. 1: Axial CT image of the abdomen at the level below the left renal vein shows large matted left paraaortic lymph nodes (arrowheads) in a 32-year-old man.
Fig.2: Testicular ultrasound was performed to search for a primary tumor. Sagittal ultrasound image of the left testis shows a small hypoechoic mass in the testis.

Paraaortic Nodal Group

• Can be divided into subgroups based on relationship with aorta and IVC: right lateroaortic (aortocaval, laterocaval, precaval, retrocaval), left lateral aortic, preaortic, retroaortic.
• Paraaortic pathway spread of tumor bypasses lymph nodes in pelvis, most common in ovarian and testicular carcinoma
• From ovaries and testicles, lymphatic vessels follow gonadal vessels to paraaortic or paracaval lymph nodes at the renal hila.
• Search for testicular/ovarian tumors if you see isolated paraaortic lymphadenopathy below the renal hila!

Lymphatic Drainage of Testes

• Two sets of lymph drainage, superficial and deep
• Superficial vessels drain surface of tunica vaginalis
• Deep vessels drain epididymis and testis
• Right testicular tumor can spread across midline, whereas left testicular tumors usually do not
• Occasionally, external iliac nodes drain the testis

Our case: left testicular seminoma with paraaortic nodal metastasis.

Reference:

Park JM, Charnsangavej C, Yoshimitsu K, et al. Pathways of nodal metastasis from pelvic tumors: CT demonstration. Radiographics 1994;14:1309-1321.

Spontaneous Osteonecrosis of the Knee (SPONK)

Author: Aasis Unnanantana, M.D.


Figure 1 and 2: AP and lateral radiographs of the left knee show subchondral sclerosis and lucency at the medial femoral condyle with narrowing of the joint space and osteophytes. Note that the lateral and patellofemoral compartments are normal.

SPontaneous OsteoNecrosis of the Knee (SPONK)

• Well-recognized cause of spontaneous, sudden onset of knee pain
• Common in woman during their 50s and 60s
• Pain typically locates around medial joint line
• Almost all cases are unilateral, one condylar involvement and epiphyseal to subchondral surface

Differential Diagnosis and Diagnosis

• Once SPONK is suspected, other DDx should be considered including osteochondritis dissecans (OCD), secondary osteonecrosis, meniscal tears, etc.
• Diagnosis made in patients with typical clinical symptoms and radiographic findings (as in this case, subchondral lucency in the medial femoral condyle, flattening of the condyle, narrow zone of increased sclerosis adjacent to the depressed osseous surface).

Reference:

Barrack RL, Booth Jr RE, Lonner JH, et al (eds). Orthopedic Knowledge Update: Hip and Knee Reconstruction 3. 2006

About Guest Author:

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