Hegemann Disease

Hegemann disease is osteochondrosis of the humeral trochlea, similar to Panner disease, but much less common. Patients are typically between the ages of 7–13 years, and present with swelling and restricted range of motion

Radiographs reveal rarefaction of the ossification center of the trochlea with condensation and collapse. Because the trochlea has a multicentric, irregular, and granular ossification center compared to the capitulum, comparison views and radiographic follow-up should be used to distinguish normal variants of ossification from Hegemann disease.

The main differential consideration is osteochondritis dissecans, which tends to affect older patients (12-15 years, around the time of epiphyseal plate ossification), does not affect the entire ossification center (only the subchondral bone), and is not a self-limited process. Chondroblastoma is also a consideration, as it tends to affect the epiphysis.

References

Patel N, Weiner SD. Osteochondritis dissecans involving the trochlea: report of two patients (three elbows) and review of the literature. J Pediatr Orthop. 2002 Jan-Feb;22(1):48-51.

Panner Disease

[image coming soon]
Osteochondrosis refers to injuries to the epiphyses, physes, and apophyses of children that occur because of a disturbance of epiphyseal growth during childhood. This results in necrosis in the subchondral bone and adjacent epiphyseal cartilage. Most osteochondroses are self-limiting.

Panner disease is an osteochondrosis characterized by necrosis of the capitular ossification center and is a cause of lateral elbow pain in children. It is thought to be due to compromise of the blood supply to the capitular ossification center due to valgus stress, and is a self-limiting process, with restoration of the normal morphology of the capitulum.

It usually occurs in the dominant elbow in children, usually boys, between the ages of 7 and 12 years. Patients present with insidious-onset dull ache and swelling over the lateral elbow. The pain is typically aggravated by activity and relieved by rest. Treatment is usually conservative and includes avoidance of activities that stress the radiocapitular joint.

Radiography reveals areas of demineralization or sclerosis, usually involving the entire ossific nucleus of the capitulum. Fragmentation of the ossification center may or may not be present.

MRI is used to assess the integrity of the overlying cartilage and to look for intra-articular fragments, but is generally not needed for diagnosis. However, MRI can reveal radiographically occult abnormalities early in the course of disease. The typical appearance is signal abnormality in the capitulum with intact overlying cartilage.

The main differential consideration is osteochondritis dissecans of the elbow, which tends to affect older patients (12-15 years, around the time of epiphyseal plate ossification), does not affect the entire ossific nucleus of the capitulum, and is not a self-limited process. Chondroblastoma is also a consideration, as it tends to affect the epiphysis.

Panner disease and osteochondritis dissecans are now thought to represent a continuum of abnormal endochondral ossification, with presentation and prognosis depending on the age of onset.

References

• Doyle SM, Monahan A. Osteochondroses: a clinical review for the pediatrician. Curr Opin Pediatr. 2010 Feb;22(1):41-6.
• Kotnis NA, Chiavaras MM, Harish S. Lateral epicondylitis and beyond: imaging of lateral elbow pain with clinical-radiologic correlation. Skeletal Radiol. 2012 Apr;41(4):369-86. Epub 2011 Dec 30.

Coracoid Fractures

Fractures of the coracoid process are uncommon injuries that can be caused by direct trauma or avulsion. Avulsion fractures can be at the attachment of the coracoclavicular ligaments in the setting of acromioclavicular dislocation or at the muscular attachments in the setting of violent contraction. They can also occur in association with clavicular fractures and shoulder dislocation and can impede reduction in the latter.

Complications of coracoid fractures include hemorrhage into the muscles of the rotator cuff and damage to the suprascapular nerve.

Coracoid fractures have been classified into 5 types based on the location of the fracture plane:

• Type 1: Involve the tip (epiphyseal fracture)
• Type 2: Through the midportion.
• Type 3: Through the base (basal fracture). Most common.
• Type 4: Extend to the superior body of the scapula.
• Type 5: Extend into the glenoid fossa.

Each can be further subdivided into A and B classifications based on the absence or presence of damage to the clavicle or its ligamentous connections to the scapula.

Management is usually conservative for types 1-3. Internal fixation is often recommended for types 4 and 5.

A simpler classification divides them into two types based on the relationship of the fracture to the coracoclavicular ligaments: Type-I fractures are proximal to this attachment and can disrupt the scapuloclavicular connection. Type-II fractures are distal to the coracoclavicular ligaments. Type I fractures often require internal fixation, while type II fractures can be managed conservatively.

The image above shows a type 2 fracture. The anteroposterior view reveals a double contour of the coracoid process (pink arrow), suggestive of displacement and early callus formation. The axillary view shows the fracture plane (white arrows) through the midportion of the coracoid process.

References

• Eyres KS, Brooks A, Stanley D. Fractures of the coracoid process. J Bone Joint Surg Br. 1995 May;77(3):425-8.
• Ogawa K, Yoshida A, Takahashi M, Ui M. Fractures of the coracoid process. J Bone Joint Surg Br. 1997 Jan;79(1):17-9.

Crimp Sleeve

Crimp sleeves (white arrows) are devices for connecting wires or cables. They are used in fishing, manufacturing, and orthopedics. Surgical cable and crimp systems are used to secure bone fragments under pressure, providing better fixation than simple twisting of cerclage wires. The wire ends pass through the crimp sleeve and are deformed by a crimping device to secure the wires in place.

Patterns of Vertebral Ossification in Paralyzed Patients

Four patterns of vertebral ossification abnormalities can be seen in paraplegic and quadriplegic patients. These resemble osteophytes, syndesmophytes, irregular paraspinal ossifications, and flowing ossifications.

• Osteophytes: Originate near the superior and inferior margins of the vertebral bodies.
• Paraspinal ossifications: Irregular, asymmetric ossification affecting paravertebral soft tissues with an appearance similar to that of psoriasis.
• Syndesmophytes: Thin areas of ossification with a symmetric vertical orientation in the outer portions of the annulus fibrosus, mimicking ankylosing spondylitis.
• Flowing ossifications: Similar to those seen with diffuse idiopathic skeletal hyperostosis (DISH). Seen in 3% of quadriplegic and 1% of paraplegic patients (may not be significantly higher than that found in the general population).

The frequency of vertebral ossification seems to be depend on age and duration of paralysis in both quadriplegic and paraplegic patients. The image above is from a patient with spinal cord injury. We see paravertebral ossifications at T3-T4 and T4-T5 with preserved disc spaces. The appearance at T3-T4 is more akin to an osteophyte, while the appearance at T4-T5 is closer to a syndesmophyte.

References

• Park YH, Huang GS, Taylor JA, Marcelis S, Kramer J, Pathria MN, Clopton P, Resnick D. Patterns of vertebral ossification and pelvic abnormalities in paralysis: a study of 200 patients. Radiology. 1993 Aug;188(2):561-5.
• Killebrew K, Gold RH, Sholkoff SD. Psoriatic spondylitis. Radiology. 1973 Jul;108(1):9-16.

Agility Total Ankle Arthroplasty

Continuing an earlier discussion on the INBONE ankle arthroplasty, we'll talk briefly about the Agility total ankle arthroplasty, the oldest and most commonly used system in the United States. It has undergone several modifications since initial FDA approval in 1992, but the essential design is a semiconstrained two-component device with a polyethylene disc.

It is important to evaluate follow-up radiographs for periprosthetic lucency, lysis, and component migration or subsidence. Subsidence at the talus is especially important to detect early. The case above is from a bone survey, so we don't have a lateral view, but there is suggestion of talar subsidence on the frontal view.

Because it is the oldest system in use, long term follow-up data are available for the Agility, and the majority don't seem to be good. A recent study of 41 patients with the Agility, for example, found that almost 40% needed revision surgery at some point (follow-up period of 6 months to 11 years), with an average time to revision surgery of 4 years. In addition, the authors found that patients without revisions reported only moderate pain relief and function.

A systematic review of all ankle arthroplasties found that revision rates published in clinical studies were about half the value found in registries, possibly because of the over-representation of publications by implant developers (almost 50% of the published content), who tended to report better results.

References

• Criswell BJ, Douglas K, Naik R, Thomson AB. High Revision and Reoperation Rates Using the Agility(TM) Total Ankle System. Clin Orthop Relat Res. 2012 Jan 24.
• Kopp FJ, Patel MM, Deland JT, O'Malley MJ. Total ankle arthroplasty with the Agility prosthesis: clinical and radiographic evaluation. Foot Ankle Int. 2006 Feb;27(2):97-103.
• Labek G, Klaus H, Schlichtherle R, Williams A, Agreiter M. Revision rates after total ankle arthroplasty in sample-based clinical studies and national registries. Foot Ankle Int. 2011 Aug;32(8):740-5.

Foreign Body

Telephone handset in rectum
Cocaine bags in colon

Foreign bodies are uncommon, but they are important and interesting. Foreign bodies may be ingested, inserted into a body cavity, or deposited into the body by a traumatic or iatrogenic injury.

Foreign body ingestions or insertions are seen in four broad categories of patients:

• Children
• Mentally handicapped persons. May present multiple times for unusual injuries and foreign body insertions and ingestions.
• Adults with unusual sexual behaviors
• "Normal" adults or children with predisposing factors or injurious situational problems. This group includes individuals who may abuse drugs or alcohol, engage in criminal activities, engage in extreme sporting activities, or may be subject to child or spousal abuse.

The rectum, vagina, urethra, nose, and ear are favorite sites for insertion of foreign objects.

References

• Hunter TB, Taljanovic MS. Foreign bodies. Radiographics. 2003 May-Jun;23(3):731-57.
• Rolando Reyna, mypacs.net

Laparotomy Sponge on Radiographs

Laparotomy sponges (lap pads) typically have an attached radiopaque strip (seen above) to aid in radiographic detection. However, retained sponges can be missed due to a number of factors: Poor image quality, inadequate field of view, distracting radiopaque operative densities, and inadequate history.

A subtle secondary sign of a retained sponge is mottled radiolucencies representing trapped air. When in doubt, cross sectional imaging can be helpful.

References

• Kaiser CW, Friedman S, Spurling KP, Slowick T, Kaiser HA. The retained surgical sponge. Ann Surg. 1996 Jul;224(1):79-84.
• O'Connor AR, Coakley FV, Meng MV, Eberhardt SC. Imaging of retained surgical sponges in the abdomen and pelvis. AJR Am J Roentgenol. 2003 Feb;180(2):481-9.

INBONE Total Ankle Arthroplasty

The INBONE^® total ankle system is a recently (11/2005) FDA-cleared prosthesis for ankle arthroplasty. The modular design of the system addresses the difficulty in placement of long tibial stems at the ankle. While flexion and disarticulation can be used at the knee and hip joints, respectively, to allow placement of long stems, neither technique is possible at the ankle joint.

The INBONE system addresses this issue through a modular design and a transcalcaneal approach. A guidance hole is drilled through the bottom of the calcaneus. When properly aligned, this small hole should be anterior and medial to the posterior facet of the subtalar joint and should not involve the subtalar joint.

The tibiotalar joint is accessed, and the talar dome is resected. The tibial reamer is then assembled within the joint space, allowing the tibia to be reamed through the small calcaneal hole. After the tibia is reamed, the modular components of the tibial stem are introduced through the tibiotalar joint and assembled.

The tibial stem consists of a top stem segment, zero or more mid-stem segments, a stem base segment, and a tibial base segment. The talar portion is also modular, consisting of talar stem and talar dome components.

Bone cement is applied to the tibial base and talar stem segments.

References

Wright corporate web site with surgical technique and videos.

Asymmetry in Rheumatoid Arthritis

While the common teaching is of rheumatoid arthritis as a symmetric process, asymmetric involvement can be seen in about 15% of cases. The tendency is toward symmetrization with time, and seropositive patients are more than twice as likely to eventually have symmetric involvement compared to seronegative patients.

Asymmetric involvement is more commonly seen at the metacarpophalangeal joints and at the wrist. The case above is a somewhat extreme example in a patient with positive rheumatoid factor. There are advanced findings of rheumatoid arthritis centered at the right wrist without significant abnormality in the other joints or on the left side.

References

• Clarke GS, Buckland-Wright JC, Grahame R. Symmetry of radiological features in the wrist and hands of patients with early to moderate rheumatoid arthritis: a quantitative microfocal radiographic study. Br J Rheumatol. 1994 Mar;33(3):249-54.
• Zangger P, Keystone EC, Bogoch ER. Asymmetry of small joint involvement in rheumatoid arthritis: prevalence and tendency towards symmetry over time. Joint Bone Spine. 2005 May;72(3):241-7.

Afghan Turban Sign

The Afghan turban sign refers to alternating bands of bony density and lucency at the metaphyses of long bones. The dense bands correspond to successive mineralization of cartilaginous zones of provisional calcification, while the lucent bands represent demineralization during repeated episodes of rickets.

The reference is to the lungee, the type of compact turban worn in Afghanistan. The lungee is tied with relatively straight side margins, which looks like the straight margins of the pattern of alternating healing and recurring rickets

The example above isn't the best, but shows two dense bands with an intervening lucent zone.

References

• Biegański T, Oestreich AE, Nowak S, Rudecka M. Ebb and flow rickets in a premature infant: the Afghan turban sign. Skeletal Radiol. 1999 Nov;28(11):651-4.

Anatomy of the Volar Branch of the Ulnar Nerve at the Wrist

Approximately 5 cm proximal to the wrist, the ulnar nerve divides into its terminal branches: The dorsal and volar branches.

The volar branch crosses the flexor retinaculum on the lateral side of the pisiform and terminates into superficial and a deep branches.

The superficial branch supplies the palmaris brevis and the skin on the ulnar side of the hand.

The deep branch passes between the abductor digiti minimi and flexor digiti minimi brevis muscles, perforates the opponens digiti minimi, and travels deep to the flexor tendons.

The sequence of axial MRIs above shows the terminal branches of the ulnar nerve in the hand and wrist.

References

Gray's anatomy.

Combination Locking Plate/Screw Systems

Locking plate/screw system offer several advantages over conventional plate/screw systems. Conventional plate/screw systems require precise adaptation of the plate to the contour of the underlying bone in order to avoid drawing the bone segments toward the plate with tightening of the screws. Locking plate/screw systems, on the other hand, do not need to intimately contact the underlying bone in all areas, because the screws lock to the plate as they are tightened and stabilize the fracture fragments.

Because locking plate/screw systems do not need to intimately contact bone, they do not disrupt the underlying cortical bone perfusion as much as conventional plates that require intimate contact of the undersurface of the plate to the cortical bone.

Locking screws are also unlikely to loosen from the plate, which is important in cases where the screw is inserted into a fracture gap or into unincorporated bone graft.

Modern plates have two connected holes. One accepts conventional screws (including lag screws), and the other has threads and accepts locking screws. The image above shows a combination plate used with conventional screws (note that the screw heads aren't flush with the plate).

References

• Rüedi TP, Buckley R, Moran CG. LCP (locking compression plate). AO Principles of Fracture Management.
• Mandible - AO Surgery Reference.

Pivot Shift Injury

A pivot shift injury occurs when a valgus force is applied to the knee in combination with external rotation of the tibia or internal rotation of the femur. Pivot shift injuries are most commonly seen in skiers and American football players.

The injury occurs when there is rapid deceleration with simultaneous direction change, which loads the anterior cruciate ligament (ACL), sometimes to the point of rupture (red arrow). With rupture of the anterior cruciate ligament, there is anterior subluxation of the tibia relative to the femur, which causes impaction of the lateral femoral condyle against the posterolateral margin of the lateral tibial plateau.

MRI will show marrow signal abnormality with or without osteochondral injuries in the posterior aspect of the lateral tibial plateau (green arrows) and the midportion of the lateral femoral condyle (blue arrows) near the lateral condylopatellar sulcus (lateral femoral notch). The posterior lip of the medial tibial plateau can also be involved, likely from contrecoup forces at resolution of the valgus load.

The location of the lateral femoral condyle injury depends on the degree of flexion of the knee at the time of injury: More flexed positions during injury result in more posteriorly located bone contusions, while Less flexed positions during injury result in more anteriorly located contusions.

Soft tissue injuries seen on MRI include disruption of the anterior cruciate ligament, most commonly in its midsubstance followed by near the femoral attachment site; tears of the posterior capsule and arcuate ligament; tears of the posterior horns of the lateral or medial menisci; and a tear of the medial collateral ligament (MCL).

References

Sanders TG, Medynski MA, Feller JF, Lawhorn KW. Bone contusion patterns of the knee at MR imaging: footprint of the mechanism of injury. Radiographics. 2000 Oct;20 Spec No:S135-51.

Spontaneous Intracerebral Hemorrhage (Volume Determination by CT)

Figure 1. CT depicts a large intracerebral hemorrhage on the left. The calipers show how to measure the size of the blood clot.


Figure 2. Number of slices on which the hemorrhage is seen. Thickness 1 cm and interval of 1 cm (4 images = 4 cm in this example).

Spontaneous intracerebral hemorrhage (SICH) is a hematoma that arises in the brain parenchyma in the absence of trauma or surgery. This entity accounts for 10% to 15% of all strokes and is associated with a higher mortality rate than either ischemic stroke or subarachnoid hemorrhage.

Common causes include hypertension, amyloid angiopathy, coagulopathy, vascular anomalies, tumors, and various drugs. Hypertension, however, remains the single greatest modifiable risk factor for SICH.

Many modern CT scanners are able to calculate hematoma volume directly by using special software. If direct volume measurements are not possible, a rapid, simplified method of determining hematoma volume has been described and validated.

The "abc method" uses the formula (a x b x c)/2, in which a is the largest diameter (in cm) of the hematoma in the CT slice with the largest area of ICH, b is the largest diameter (in cm) of the hemorrhage perpendicular to line a; and c is number of slices with hematoma multiplied by the slice thickness in cm. This formula yields hematoma volume in cm³ (cc).

4.65 x 2.51 x 4/2 = 23.3 cc in this case.

References

• Fewel ME, Thompson BG Jr, Hoff JT.Spontaneous intracerebral hemorrhage: a review. Neurosurg Focus. 2003 Oct 15;15(4):E1.
• Kothari RU, Brott T, Broderick JP, Barsan WG, Sauerbeck LR, Zuccarello M, Khoury J. The ABCs of measuring intracerebral hemorrhage volumes. Stroke. 1996 Aug;27(8):1304-5.
• Mohr JP, Choi DW, Grotta JC, Weir B, Wolf PA. Mohr: Stroke: Pathophysiology, Diagnosis, and Management, 4th ed. Churchill Livingstone (2004); page 327.
• Rolando Reyna, mypacs.net

Cardiac Conduction Device Lead Fixation

The leads of cardiac conduction devices can be secured in the heart by passive or active fixation. Passively fixed leads have tines, fins, helices, or conical structures at their tip that lodge in the cardiac trabeculae to maintain lead stability. Actively fixed leads (shown above) have a corkscrew helix at their tips that screws into the myocardium to maintain stability in wide range of intracardiac locations.

After about a month or so, scar tissue will stabilize the leads regardless of the mechanism of initial fixation.

Refernces

Aguilera AL, Volokhina YV, Fisher KL. Radiography of cardiac conduction devices: a comprehensive review. Radiographics. 2011 Oct;31(6):1669-82.

Artificial Urinary Sphincter

The artificial urinary sphincter is an implantable device for management of urinary incontinence. It consists of a pressure-regulating balloon that is implanted in the abdomen, a pump that is implanted in the scrotum or labia (as shown above), and a cuff implanted around the urethra. The pump is manipulated by the patient to increase or decrease the pressure in the periurethral cuff.

Special thanks to Dr. Hansel Otero for the case.

References

Inflatable artificial sphincter. MedlinePlus.

High Origin of the Anterior Band of the Inferior Glenohumeral Ligament

The anterior band of the inferior glenohumeral ligament (aIGHL) usually arises from anteroinferior labrum (below ~4 o’clock), but origins as high as 1 o’clock and from the middle glenohumeral ligament have also been described. These higher origins can mimic labral tears, variants (e.g., sublabral foramen and recess), or normal structures (e.g., spiral glenohumeral ligament) on MR imaging or MR arthrography to the uninitiated.

There may also be a relationship between the sites of attachment of the long head of the biceps tendon and the aIGHL. A study of ~100 cadavers suggested that a long head of the biceps attachment to the posterior labrum was associated with an aIGHL origin below the 4 o’clock position, while a biceps tendon attachment elsewhere was associated with a higher origin of the aIGHL. More recent work (10 cadavers) has not supported these results, however.

References

• Merila M, Leibecke T, Gehl HB, Busch LC, Russlies M, Eller A, Haviko T, Kolts I. The anterior glenohumeral joint capsule: macroscopic and MRI anatomy of the fasciculus obliquus or so-called ligamentum glenohumerale spirale. Eur Radiol. 2004 Aug;14(8):1421-6.
• Ramirez Ruiz FA, Baranski Kaniak BC, Haghighi P, Trudell D, Resnick DL. High origin of the anterior band of the inferior glenohumeral ligament: MR arthrography with anatomic and histologic correlation in cadavers. Skeletal Radiol. 2011 May 22.
• Tuoheti Y, Itoi E, Minagawa H, Yamamoto N, Saito H, Seki N, Okada K, Shimada Y, Abe H. Attachment types of the long head of the biceps tendon to the glenoid labrum and their relationships with the glenohumeral ligaments. Arthroscopy. 2005 Oct;21(10):1242-9.

MRI Staging of Avascular Necrosis

A staging system has been developed for avascular necrosis based on signal characteristics at the center of the lesion.

Class	T1	T2	Comment
A	High	Intermediate	Fat
B	High	High	Blood
C	Low	High	Fluid
D	Low	Low	Fibrosis

Class A signal intensity is typically seen in early disease, while class D signal intensity is typically seen in late disease. However, more than one class of signal intensity can be found in a single lesion.

References

Mitchell DG, Rao VM, Dalinka MK, Spritzer CE, Alavi A, Steinberg ME, Fallon M, Kressel HY. Femoral head avascular necrosis: correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings. Radiology. 1987 Mar;162(3):709-15.

Diffuse Idiopathic Skeletal Hyperostosis: Pelvis

We're all familiar with the spinal findings of diffuse idiopathic skeletal hyperostosis (DISH). Radiographic manifestations in the pelvis are usually symmetrical and include:

• Enthesophytes (yellow arrows): Irregular outgrowths or whiskering seen most commonly at the iliac crests, ischial tuberosities, and the trochanters.
• Para-articular osteophytes (red arrows): Broad and well-defined. Seen at the acetabular margins, sacroiliac joints, and pubic symphysis. Sacroiliac osteophytes tend to affect the inferior margins.
• Ligamentous ossification: Iliolumbar (black arrows) and sacrotuberous ligaments.

References

• Resnick D, Shaul SR, Robins JM. Diffuse idiopathic skeletal hyperostosis (DISH): Forestier's disease with extraspinal manifestations. Radiology. 1975 Jun;115(3):513-24.

KLS Talon Sternal Closure

The KLS Sternal Talon is a new sternal closure device. The device has two halves that are placed on opposite sides of the sternotomy and snapped together. Each half can can have either one or two legs (or hooks). The single-legged design is shown above.

The device is said to distribute force across a larger area of bone, which can be helpful in patients with morbid obesity, diabetes, chronic obstructive pulmonary disease (forceful coughing), or osteoporosis. The design also allows for rapid opening in case of post-operative complications.

Videos and pictures can be found at the links below.

References

• Levin LS, Miller AS, Gajjar AH, Bremer KD, Spann J, Milano CA, Erdmann D. An innovative approach for sternal closure. Ann Thorac Surg. 2010 Jun;89(6):1995-9.
• Publicity web site with videos.
• Corporate web site with videos.

The Dunn View

The Dunn view, originally described in 1952 for measuring the anterversion of the femoral neck in children, is now commonly used for assessment of femoral head sphericity in young adults suspected of having cam-type femoroacetabular impingement (FAI).

As originally described (sometimes called the 90° Dunn view), it is an anteroposterior view of the hip with the patient supine and with the hips and knees flexed at 90°, the legs abducted 15°-20° from the midline, and the femur in neutral rotation. The beam is centered at the midway point between the anterior superior iliac spine and the pubic symphysis, and the tube-to-film distance is ~40 in (102 cm). Imagine a patient lying flat on an examination table with the legs in stirrups.

The modified (45°) Dunn view is the same, except that the hip is flexed to 45°. Imagine a patient lying flat on a table with the knee bent and the foot flat on the table. The paper by Clohisy et al has nice pictures of these views.

The Dunn views (45° or 90°) are best at demonstrating femoral head asphericity. A cross-table view in internal rotation can also be used, but anteroposterior or externally rotated cross-table views are likely to miss asphericity.

Using MRI as the standard, and a cut-off alpha angle of 50.5° for diagnosis of cam-type FAI, the 90° Dunn view was found to be 91% sensitive and 88% specific, with a positive predictive value of 93%, negative predictive value of 84%, and accuracy of 90%. There was also strong correlation between alpha angles on the Dunn view and on MRI (Pearson correlation of 0.7).

References

• Barton C, Salineros MJ, Rakhra KS, Beaulé PE. Validity of the alpha angle measurement on plain radiographs in the evaluation of cam-type femoroacetabular impingement. Clin Orthop Relat Res. 2011 Feb;469(2):464-9.
• Clohisy JC, Carlisle JC, Beaulé PE, Kim YJ, Trousdale RT, Sierra RJ, Leunig M, Schoenecker PL, Millis MB. A systematic approach to the plain radiographic evaluation of the young adult hip. J Bone Joint Surg Am. 2008 Nov;90 Suppl 4:47-66.
• Dunn DM. Anteversion of the neck of the femur; a method of measurement. J Bone Joint Surg Br. 1952 May;34-B(2):181-6.
• Meyer DC, Beck M, Ellis T, Ganz R, Leunig M. Comparison of six radiographic projections to assess femoral head/neck asphericity. Clin Orthop Relat Res. 2006 Apr;445:181-5.

The Pelvic Digit

Bony protuberance at the left anterior inferior iliac spine

A pelvic digit is a rare congenital anomaly in which bone develops in soft tissues adjacent to normal skeletal structures. On radiographs it typically appears as a rib- or a phalanx-like bone with a clear cortex and medulla related to the pelvis, often with a characteristic pseudoarticulation at the base. It has been previously reported as an iliac rib or pelvic rib.

It is important to distinguish a pelvic digit from acquired anomalies such as myositis ossificans and avulsion injuries of the pelvis.

This anatomic variant can originate from a displaced costal process, a displaced sternal center, or the ossification center at the anterior superior iliac spine. These explanations, however, do not take into account the varied sites of attachment in the pelvis. As a pelvic digit can be found at the coccyx, the pelvic walls, and the inferior abdominal wall, it must arise from an embryonic mesoderm with rib-forming capacity that is disposed to these regions.

At the end of the third week of embryogenesis, embryonic mesoderm cells, with the potential to form ribs, migrate from the primitive streak and pass around the cloacal membrane, from the region of the future coccyx, through the region of the future pelvic walls, to the region of the lower abdominal wall.

References

• Casey MC, Phancao JP, Pressacco J. Answer to case of the month #106. Pelvic Digit. Can Assoc Radiol J. 2006 Feb;57(1):51-3.
• Rolando Reyna. MyPacs.net

Diffuse Idiopathic Skeletal Hyperostosis: Hands

We're all familiar with the spinal manifestations of diffuse idiopathic skeletal hyperostosis (DISH). Findings in the appendicular skeleton are not as well known:

• Sites of tendon and ligament attachment: Periosteal enthesophytes and dystrophic calcification can be seen.
• Joints: Para-articular osteophytes that can bridge the articulation. The bone underlying the osteophyte can be sclerotic. The involved joint can be radiographically normal, but will usually have degenerative cartilage and bony changes histologically.
• Ligaments: Ligamentous mineralization is analogous to the familiar ribbon-like calcifications seen along the anterior aspect of the vertebral bodies. Ranges from minimal involvement to involvement of the entire ligament.

In the hand, DISH can manifest as:

• Broadening and arrowheading of the distal phalangeal tufts: Can also be seen in acromegaly. Typically less marked in DISH.
• Increased cortical width of tubular bones: Can also be seen in acromegaly.
• Enlarged sesamoid bones: Can also be seen in acromegaly. Typically less marked in DISH.
• Exostoses: Metacarpal and phalangeal (orange arrow) heads, distal end of the radius (pink arrow). Here we see also one in the left scaphoid(yellow arrow). Can also be seen in acromegaly, but is typically more marked in that condition.
• Enthesopathy: At the proximal phalanges (blue arrows). Can also be seen in acromegaly, but is typically mild in that condition.
• Joint capsule bone formation: Can also be seen in acromegaly, but is typically more marked in that condition.
• Osteoarthritis and osteophyte formation: Interphalangeal joints (green arrow).

Although some of the findings can resemble those of acromegaly, patients with DISH do not have the soft tissue and cartilage hypertrophy that can be seen in acromegaly.

References

• Littlejohn GO, Urowitz MB, Smythe HA, Keystone EC. Radiographic features of the hand in diffuse idiopathic skeletal hyperostosis (DISH): comparison with normal subjects and acromegalic patients. Radiology. 1981 Sep;140(3):623-9.
• Resnick D, Shaul SR, Robins JM. Diffuse idiopathic skeletal hyperostosis (DISH): Forestier's disease with extraspinal manifestations. Radiology. 1975 Jun;115(3):513-24.
• Schlapbach P, Beyeler C, Gerber NJ, van der Linden S, Bürgi U, Fuchs WA, Ehrengruber H. The prevalence of palpable finger joint nodules in diffuse idiopathic skeletal hyperostosis (DISH). A controlled study. Br J Rheumatol. 1992 Aug;31(8):531-4.

Mesenteric Trauma

CT manifestations of mesenteric trauma can include:

• Internal hernia: Secondary sign of a mesenteric tear (difficult to detect on CT). Closed loop bowel obstruction, volvulus, and strangulation can occur.
• Increased mesenteric attenuation: Can be a manifestation of isolated mesenteric injury.
• Mesenteric hematoma: When seen in the portal venous-phase, should be evaluated on delayed images: Enlargement or increased attenuation is a sign of active bleeding (see below). Small isolated mesenteric hematomas can be managed conservatively with observation. Large hematomas indicated injury to major mesenteric vessels, and are managed surgically to avoid the risk of delayed bowel ischemia.
• Beading or abrupt termination of mesenteric vessels: In the setting of trauma, these are signs of significant venous or arterial injury.
• Active extravasation: Uncommon, but ~100% specific for a significant vascular injury. Requires operative repair. Endovascular coil embolization is sometimes attempted with injury to smaller vessels; however, patients should be closely monitored for signs of bowel ischemia.

Specific signs of mesenteric trauma include mesenteric hematoma, intraperitoneal extravasation of intravenous contrast, and abrupt termination or unequivocal irregularity of the wall of mesenteric vessels.

When specific signs of mesenteric trauma are encountered, a careful search for associated bowel injury should be initiated.

The image above is from a trauma patient. There is active extravasation of contrast in the right lower quadrant (blue arrows) from injury to iliocolic branch of the superior mesenteric artery (pink arrows). Delayed images show expansion of the extravasated pool of contrast (green arrows). The patient also had a jejunal hematoma (not shown).

References

LeBedis CA, Anderson SW, Soto JA. CT imaging of blunt traumatic bowel and mesenteric injuries. Radiol Clin North Am. 2012 Jan;50(1):123-36.

Anterior Column Acetabular Fracture

Anterior column fractures make up to 5% of acetabular fractures. These fractures separate the anterior border of the innominate bone from the remaining ilium.

Several types of anterior column fractures have been described based on the location where the fracture plane exits the anterior aspect of the bone. However, all types cross the pelvic brim and result in a fracture of the inferior pubic ramus.

• Very low: Exit through the iliopectineal eminence. Can be distinguished from anterior wall fractures by the presence of an inferior pubic ramus fracture and a single break in the iliopectineal line.
• Low: Exit just below the anterior inferior iliac spine.
• Intermediate: Exit through the anterior superior iliac spine.
• High (shown above): Exit through the iliac crest.

Radiographs reveal disruption of the iliopectineal line where the anterior column fracture plane crosses the pelvic brim. This is best seen on the frontal and obturator oblique views. The femoral head moves medially and superiorly with the anterior column fragment.

The images above are from a patient with a high anterior column fracture. The radiograph reveals disruption of the iliopectineal line and a lucency through the iliac wing extending to the iliac crest. The CT images delineate the path of the fracture plane through the iliac crest and inferior pubic ramus.

References

• Rockwood and Green's Fractures in Adults (7th ed), pp 1478-1479.
• Mack LA, Harley JD, Winquist RA. CT of acetabular fractures: analysis of fracture patterns. AJR Am J Roentgenol. 1982 Mar;138(3):407-12.

Chagas Disease (Chagasic Esophagopathy)

Chest radiograph: A wide mediastinum with normal heart size.

Contrast series: a dilated esophagus is seen in the AP projection.

CT: The esophagus is seen dilated with fluid in the lumen.

Chagas disease is found only in Latin America. It is named after Carlos Chagas, a Brazilian doctor who first described the disease in 1909. He also described the life-cycle of the parasite, identified the insects that transmit the parasite, identified small mammals that act as reservoir hosts, and suggested means to help prevent its transmission.

Usually a person experiences no immediate symptoms following infection. Ten to 20 years later, however, Chagas disease can appear and bring with it several serious heart disorders.

Chagas disease is a protozoosis caused by the flagellate protozoa Trypanosoma cruzi. The infection is usually transmitted via the feces of blood-sucking insect vectors (reduviid bugs). The infection is mostly found in small mammals (sylvatic cycle), and human disease results from the colonization of the human habitat by some vector species (domestic cycle). Vectorial transmission (via the feces of Triatominae) is responsible for 80% of human infections. The entry of metacyclic trypomastigotes via the mucosal route (oral or ocular) is easy. Direct skin penetration seems more difficult, and generally, the parasite enters via the site of the bite or the microlesions associated with scratching.

Chagas disease results in 45,000-50,000 deaths per year. Mortality is mainly due to chronic chagasic cardiomyopathy. Sudden death, usually due to ventricular fibrillation, is the principal cause of death in 60% of cases. Bradyarrhythmia, thromboembolic phenomena, and, rarely, a ruptured aneurysm, are other causes of sudden death. Congestive heart failure (25-30% of cases), cerebral or pulmonary embolism (10-15% of cases. Symptomatic acute phases mainly occur in newborns (congenital infection) or young children. Chagasic esophagopathy is observed more frequently in the second decade of life, and chronic chagasic cardiomyopathy and colopathy are generally detected later, in the third, fourth, or fifth decade of life.

Radiographic contrast study of the esophagus: Serial radiographs of the esophagus at different times after contrast ingestion allow classification of patients into 1 of 4 evolutive stages of the chagasic esophagopathy.

With stage I, the diameter of the esophagus is normal; emptying is delayed. The organ is sometimes hyperkinetic.

With stage II, the organ is dilated (megaesophagus) and displays irregular motile activity. The gastroesophageal sphincter is hypertonic.

With stage III, dilatation and retention are important, and the motile activity is clearly reduced.

With stage IV, the esophagus is clearly dilated and elongated (dolichomegaesophagus) and atonic.

References

• Franquet T, Erasmus JJ, Giménez A, Rossi S, Prats R. The retrotracheal space: normal anatomic and pathologic appearances. Radiographics. 2002 Oct;22 Spec No:S231-46.
• Martínez S, Restrepo CS, Carrillo JA, Betancourt SL, Franquet T, Varón C, Ojeda P, Giménez A. Thoracic manifestations of tropical parasitic infections: a pictorial review. Radiographics. 2005 Jan-Feb;25(1):135-55.
• Rolando Reyna, mypacs.net.

The Long Plantar Ligament Enthesophyte

Enthesophytes can arise from several places on the plantar surfaces of the calcaneous. One of these is at the origin of the long plantar ligament, which originates from the plantar aspect of the calcaneus between the posterior and anterior tubercles and inserts into the cuboid, with some fibers continuing on to the second to fourth metatarsal bases. Enthesophytes can also arise from the site of origin of the short plantar (calcaneocuboid) ligament (calcaneocuboid ligament) on the anterior tubercle.

The image above shows two plantar calcaneal enthesophytes, one arising just above the origin of the plantar fascia, and the other arising from the origin of the long plantar ligament (pink arrow).

References

• Abreu MR, Chung CB, Mendes L, Mohana-Borges A, Trudell D, Resnick D. Plantar calcaneal enthesophytes: new observations regarding sites of origin based on radiographic, MR imaging, anatomic, and paleopathologic analysis. Skeletal Radiol. 2003 Jan;32(1):13-21.
• Ward KA, Soames RW. Morphology of the plantar calcaneocuboid ligaments. Foot Ankle Int. 1997 Oct;18(10):649-53.

Traumatic Pneumatocele

CT shows two pneumatoceles near the pleural surface with fluid (Traumatic pneumatocele Type I)

A laceration is defined as an abnormal intraparenchymal collection of air resulting from traumatic disruption of the lung architecture.

Types of laceration:

• Type 1 is an air-filled cavity with or without an air-fluid level, resulting from sudden compression of a pliable chest wall wherein the air-containing lung ruptures.
• Type 2 is an air-containing cavity in a paravertebral location, resulting from severe compression of the more pliable lower chest wall and sudden shifting of the lower lobe across the vertebral body causing a shearing type of injury.
• Type 3 is a small peripheral cavity or peripheral linear radiolucency that is always close to the chest wall where a rib has been fractured, resulting from a fractured rib that has punctured the lung.
• Type 4 is a result of previously formed, firm pleuropulmonary adhesions causing the lung to tear when the overlying chest wall is violently moved inward or fractures, diagnosed only at surgery or autopsy.

The intraparenchymal collections of air described are also termed pneumatoceles. When traumatic cavities fill with blood, a hematoma forms. Radiographically, traumatic pneumatoceles and hematomas are not usually seen until a few hours or even several days after trauma, initially obscured by surrounding contusion. The size, shape,thickness of the wall, and number of pneumatoceles varies widely from patient to patient.

Unlike a simple contusion, which resolves fairly quickly and completely, a laceration generally takes weeks to months to resolve and may result in residual scarring.

Occasionally, pneumatoceles can become secondarily infected, resembling formation of a hematoma.

References

• Collins J and Primack SL. CT of nonpenetrating chest trauma. Applied Radiology. 2001 Feb;30(2):11-21.
• Rolando Reyna. Traumatic Pneumatocele. mypacs.net