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DCMC Emergency DepartmentRadiology Case of the MonthThese cases have been removed of identifying information and are intended for peerreview and educational purposes only.

Welcome to the DCMC Emergency Department Radiologycase of the month!

In conjunction with our pediatric radiologyspecialists from ARA we hope you enjoy these monthlyradiological highlights from the case files of the EmergencyDepartment at DCMC. These cases are meant to highlightimportant chief complaints, cases, and radiology findings thatwe all encounter every day.

If you enjoy these reviews we invite you check outPediatric Emergency Medicine Fellowship RadiologyRounds, which are currently offered quarterly and are heldwith the outstanding support of the pediatric radiologyspecialists at Austin Radiologic Association.

If you have any questions or feedback regarding the Case of the Month format, feel free to email Robert Vezzetti, MD at rmvezzetti@seton.org.

PEM Fellow Conference Schedule October 2015

6th - Faculty Development: Simulation....................................................Dr Floyed Faculty Development: Research..................................................Dr Wilkinson

7th - 8:15-10:15 Sim: Cardiology.......................Drs Wyrick and Ryan/Sim Faculty 11:15-12:15 TBD 14th - 9:15-10:15 US: Renal/Abdominal Pathology..................................Dr Boeck 11:15-12:15 Grand Rounds

16th - PEM Fellowship Applicant Interview Day

20th - Living Well in PEM.........................................................PEM Faculty

21st - 9:15-10:15 PEM Radiology Rounds: Thorax ...Drs Vezzetti/Berg/Lonergan 10:15-11:15 Research Lecture.....................................................Dr Wilkinson 12:15-1:15 PEM Fellowship Research Update

28th - 9:15-10:15 M&M..............................................................Drs Kienstra and Hill 10:15-11:15 Board Review: GI.............................................................Dr Gorn 12:00-1:15 ED Staff Meeting

30th - PEM Fellowship Applicant Interview Day

Guest Pediatric Radiologist: Dr Gael Lonergan, MD DCMC/ARA

All Lectures are at Dell Children’s Medical Center in Command Rooms 3&4, unless otherwise specified.

Simulations are held at the CEC at University Medical Center - Brackenridge. Schedule subject to change.

This Month: BOO!! Happy Halloween to All! We haven’t had an ortho case in a while, so...............A young girl who has sustained a knee injury while running at school. This is a very common complaint and which, if any, imaging tests to order can be confusing, if not scary! Additionally, what does one do when they find something they were not expecting, especially when it is not related to the reason an imaging test was obtained in the first place? We’ll also look at some common knee injuries, so read on...

“docendo discimus”

Charles Samuel "Chas" Addams (January 7, 1912 – September 29, 1988) was an American cartoonist known for his darkly humorous and macabre characters. Some of the recurring characters, became known as The Addams Family, which first appeared in the New Yorker.

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Case History: Ah, the start of school! It’s that time of year where sunburns and insect stings start to fade away and just before the dreaded RSV/Influenza/URI season. Yep, time for some athletic injuries, which are plentiful in the Pediatric Emergency Department.

You settle in to your shift as you pick up the first chart, which is a 11 year old female with right knee pain. Apparently she was running at school when she experienced a “pop” in her knee, followed by sudden pain. She was unable to continue running; the athletic trainer at the school applied ice to the knee, but swelling developed and, eventually, began to worsen. By this point she was unable to ambulate without pain, so she was brought into the Pediatric Emergency Department for an evaluation.

You note that the vital signs are all unremarkable. She has been in good health, for the most part, but did have a fracture of her left tibia earlier in the year, which was treated by Pediatric Orthopedics at Dell. On examination, you note a child who is in some discomfort, which she states is due to her knee pain. Her knee has some mild generalized edema, but no obvious deformity. The joint appears possibly lax, but this is difficult to assess secondary to pain. Her hip, femur, tibia/fibula, ankle, and foot all appear to be normal. She has strong popliteal, dorsalis pedis, and posterior tibia pulses. She is neurologically intact. She refuses to ambulate secondary to pain, but her mother states she was “limping” when picked up at school.

Motrin was given in Triage and the child states that this has “helped a little bit”. The ice pack that was applied at school also helped, but it warm now, so you replace and and begin to ponder how to work up this injury. Does this child need imaging? Is an xray sufficient? Should you proceed to a CT or an MRI? Maybe you could just ask for a Pediatric Orthopedic consult.....

Please Note: A special thanks to Dr Robert Schlecter for adding the following teaching points from one of last month’s cases:“Two points... Atresia is a complete obstruction, so presents prenatally or with first feeds.  Stenosis can present later. Also... The history was so characteristic of SMA syndrome that consideration could be given to an Ultrasound before CT... It can be dxed on US.”

Differential Diagnosis:

Knee injuries are very common complaints in Pediatrics, so it’s nice to have a good differential when evaluating these patients. Here’s an example:

Mechanism Type Of Injury

High impact trauma (MVC, etc). Knee dislocation, PCL tear

Knee “went out” after pivoting. Patellar dislocation; ? osteochondral fx

Fall with twisting/hyperextension. Tibial spine fx

Jumping. Tibial tubercle avulsion fx

Valgus stress. MCL injury or physeal fx

Varus stress. LCL injury or physeal fx

Hyperextension, twisting. ACL injury, tibial spine fx

Direct blow/fall. Patellar/osteochondral fx

“Pop”. ACL injury/patellar dislocation

Adapted from: Canty GS and Knapp JF. The Initial Assessment and Management of Peditric Knee, Ankle, and Wrist Injuries. Peditrc Emerg Med Pract. 2008;5(8).

Remember varus and valgus forces from your orthopedics rotation? neither do I. But here is a drawing to help us both keep it straight.

Valgus is a force applied to the lateral knee.

Varus is a force applied to the medial knee.

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It helps to remember, then evaluating children with skeletal injuries, that: “the more immature the patient’s skeleton, the greater the risk for fracture”.

There are a few things to remember when evaluated pediatric knee injuries. One good hint is that obtaining an imaging test is usually a good idea prior to performing more detailed examinations of the knee (for example, the various tests for joint or ligamentous injury). There are two well-established guidelines to help decide when to obtain radiographs in pediatric knee injuries:1. The Ottawa Knee Rule.2. The Pittsburgh Knee Rule.The Ottawa Knee Rule is most-validated in pediatric patients.

Ottawa Knee RulesRecommend Radiographs If:1. Age > 55 years.2. Isolated tenderness of the patella.3. Tenderness at the fibular head.

4. Inability to flex knee to 90〫.

5. Inability to bear weight immediately after injury and in the Emergency Department.

Studies have found high sensitivities (80%-100%), but low specificities.

Pittsburgh Knee RulesRecommend Radiographs If:1. Age <12 years or > 50 years.2. Age 12-50 years of age with trauma and is unable to

to walk 4 weight-bearing steps in the Emergency Department without limping.

This decision rule has not been validated in patients under 12 years of age, because a states risk factor is age >12 years. In the age range of 12-50 years, sensitivity of this rule is 99% and specificity is 60%, in most studies.

You decide to obtain a 3 view knee series, as this patient is <12 years old and, frankly, has a somewhat difficult exam. The results are below:

There is an extremely subtle irregularity of the right proximal tibia, best seen on the oblique view. There appears to be buckling of the metaphysis (red arrow). This may extend into the knee joint but it is very difficult to tell. By the way, did you notice the lesion in the femur (blue arrow). Now what?

Gomez Addams: “Husband to Morticia, if indeed they are married at all... a crafty schemer, but also a jolly man in his own way... though sometimes misguided... sentimental and often puckish - optimistic, he is in full enthusiasm for his dreadful plots... is sometimes seen in a rather formal dressing gown... the only one who smokes.”-Charles Addams

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Here’s a close up of the oblique view. Very subtle posterolateral buckling. OK, the xrays are suspicious for a fracture. This is not just any fracture, as it

may extend into the joint space, which is significant. Further imaging is warranted, especially to evaluate for any joint space involvement. The lesion appears to be a benign non-ossifying fibroma.

Standard 3 view radiographs of the knee include: AP view, Lateral view, and Oblique or Patellar views. Other plain radiograph options include:1. Tunnel/Notch view -> can find loose bodies and osteochondritis dissecans.2. Stress view -> painful to obtain, but can detect opening of the physis with valgus or varus stess

application.

What About CT Scanning?CT is very sensitive for fractures and very good at detecting tibial plateau fractures and is often obtained in patients with complex fractures. In cases of significant trauma, CT angiography is used to look for vascular injury.“The advantage of CT is that it shows cortical bone detail well, is easier to obtain if a CT scanner is near the emergency department, has a shorter total scan time (important in severely injured patients), and has a lower cost.” -Amer Rad Assn.

Ultrasound is good at detecting ligamentous injuries, but should only be performed by personnel very experienced in it use.

In light of the physical examination findings and what might be an intra-articular fracture on plain film, Pediatric Orthopedics is consulted. They recommend and MRI, since there is no evidence of a displaced fracture and there is a concern about ligamentous injury, given the “pop” the patient experienced. Outpatient study?

Morticia Addams: “The real head of the family... low-voiced, incisive and subtle, smiles are rare... ruined beauty... contemptuous and original and with fierce family loyalty... even in disposition, muted, witty, sometimes deadly... given to low-keyed rhapsodies about her garden of deadly nightshade, henbane and dwarf's hair...” -Charles Addams

Thing was originally depicted as a figure with long black hair that often watched the family from the top of the stairs or from inside a closet. However, a cartoon published on March 20th, 1954, depicted a pair of hands reaching out from inside a table, closer to the subsequent television version.

Here are some common tests used during physical examination of the knee.

Anterior Drawer Test: Patient supine with the hip flexed to 45〫. Push/pull the proximal portion of the leg while sitting on the foot. This should be done at neutral, 30〫externally rotated, and 30〫 internally rotated. A positive test is laxity more than 6-8 mm.Lachman Test: Patient is supine with the leg slightly externally rotated and flexed (no more than 30〫). While stabilizing the femur, apply pressure to the back of the knee with your other hand.A positive result is knee movement with a soft end point.Pivot Test: With the knee fully extended, rotate the foot internally; apply a valgus stress while flexing the knee.McMurray: While flexing the hip and knee, apply a valgus force to the knee while externally rotating the foot and extending the knee (medial meniscus); apply a varus force while internally rotating the knee (lateral meniscus).

from: Jackson JL, O’Malley PG, Kroenke K. Evaluation of acute knee pain in primary care. Ann Intern Med. 2003;139:580.

ACL TestACL Test

Most common ligament injury of the knee is the anterior cruciate (ACL).

Most common collateral ligament injury is the medial collateral ligament (MCL).

Meniscal tearACL Test

MRI is always an option and the study of choice to evaluate suspected ACL tears and ligamentous injuries. It is NOT a routine study, though, and is usually ordered after consultation with Pediatric Orthopedics. It is also not always readily available. “MRI is considered the optimal imaging modality for identifying meniscal, ligament, chondral, and nondisplaced bone injuries around the knee. Numerous studies have shown that MRI has a high diagnostic accuracy in identifying traumatic intra-articular knee lesions. The advantage of MRI is that it can demonstrate soft tissue and bone marrow injuries while adequately demonstrating many cortical bone fractures”. -Amer Rad Assn.

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“Uncle Fester is incorrigible and except for the good nature of the family and the ignorance of the police, would ordinarily be under lock and key... the eyes are pig-like and deeply embedded... he likes to fish, but usually employs dynamite... he keeps falcons on the roof which he uses for hunting... his one costume, summer and winter is a black great coat with an enormous collar... he is fat with pudgy little hands and feet.” -Charles Addams

Wednesday: “Child of woe is wan and delicate...sensitive and on the quiet side, she loves the picnics and outings to the underground caverns...a solemn child, prim in dress and, on the whole, pretty lost...secretive and imaginative, poetic, seems underprivileged and given to occasional tantrums...has six toes on one foot...” -Charles Addams

Patellar Dislocation: This is seen with some frequency in the Pediatric Emergency Department, but arguably one of the scariest injuries for patients. I mean, look at the patella! These are generally very easy to relocate. Typically these injuries are laterally dislocated, although medical dislocation does occur. Once the patella is relocated, it’s a good idea to obtain plain xrays, as fractures are present in roughly up to 30% of patients.

Apply median pressure Extend the leg24% of patients whose patellas have dislocated have relatives who have experienced patellar dislocations. Most common sports involved: basketball, soccer, football, gymnastics.

Diagnosing patellar dislocations does not require initial use of radiographs because the condition is usually clinically obvious, but here is a radiograph demonstrating a lateral patellar dislocation. After reduction, a knee immobilizer is placed, crutches are used, and followup with pediatric orthopedics arranged.

THISShould be HERE

Other Scary Knee Injuries:

Here’s the bone cyst on the MRI.

Here is the MRI. On the extreme left you can see the benign bone cyst. A selected MRI image from the series is seen below. The ligaments and menisci are all intact. There is no obvious fracture. There is some mild overall edema of the soft tissues and bone marrow (yellow arrow), but otherwise this is a fairly unremarkable MRI of the knee.NOTE: MRI studies are not easy

to come by in general, and are

typically done on an outpatient basis.

Medial meniscus

Lateral meniscus

Femur

TibiaNormal Anatomy Example

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Pugsley: “An energetic monster of a boy... blond red hair, popped blue eyes and a dedicated troublemaker, in other words the kid next door... genius in his own way, he makes toy guillotines, full-size racks, threatens to poison his sister, can turn himself into a Mr. Hyde with an ordinary chemical set... his voice is hoarse... is sometimes allowed an occasional cigar.”-Charles Addams

Lurch: "This towering creature has been shambling around the house forever... He is not a very good butler but a faithful one... One eye is opaque, the scanty hair is damply clinging to his narrow flat head...” -Charles Addams

Knee Dislocation: Here is an example of a knee dislocation--very different from a patellar dislocation. In this case, the tibia is displaced laterally and posteriorly (blue arrow) compared to the femur (red arrow). The patella (yellow arrow) is also displaced laterally. Knee dislocations are very rare in pediatrics. Anterior dislocations are most common and are usually the result of severe hyperextension. Posterior dislocations occur with anterior-posterior forces to the proximal tibia. Medial, lateral, rotary dislocations are the result of varus/valgus forces. These are high impact, high force injuries and may also be seen in high speed motor vehicle crashes.

Courtesy: Learningradiology.comCourtesy: Learningradiology.com

Knee dislocations are high risk injuries; they are frequently accompanied by vascular injury. The specific artery of concern is the popliteal artery. Patients with knee dislocations should undergo angiography to assess to arterial damage. A very low threshold should be maintained to consult pediatric orthopedics and vascular surgery in these patients.

These images to the left show severe fractures of the femur, tibia, and patella. The arteriogram demonstrates occlusion of the popliteal artery, concerning for arterial injury.

From: Kang ST, Hwang CH, Kim BH, and Sung BY.Loss of Distal Femur Combined with Popliteal Artery Occlusion: Reconstructive Arthroplasty Using Modular Segmental Endoprosthesis: A Case Report.J Korean Med Sci. 2009;24(2):350-353.

Popliteal artery

Occlusion

Distal Femur Fracture: This child was jumping on a trampoline a fell off. She immediately felt pain, and here we see on the xray why; she has a distal femur fracture. It’s a buckle, specifically, and should heal fine.

Treatment of distal femur fracture depends on the degree of the fracture. In this case, a splint, then a cast. Complicated femur distal femur fractures often have a CT scan to assess for knee join involvement.

Significant femur fractures (mid shaft angulated fractures, for example) often require surgical correction.

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I thought we should show this by now. Here are some normal view of the knee, so we can get a good idea of what the normal knee looks like. The views we seen here are an AP, Lateral, Sunrise (or Skyline) view, and an Intracondylar View.

FROM: Wikiradiography.com

Online Radiography Encyclopedia

Position of the knee in the process of obtaining common images. (FROM: ORIF.com)1. Sunrise View.

a. Helpful for: Tibial Plateau Fracture, Distal Femur Fracture

2. Lateral View.

a. Helpful for: Tibial Plateau Fracture, Distal Femur Fracture.

3. AP View.

a. Helpful for: Tibial Plateau Fracture, Distal Femur Fracture

1.

2. 3

Nice sunrise view of a patellar fracture!

By the way...

Cool 3D reformat of a CT showing a tibial plateau fracture. This is topic unto itself, but there are 6 types and often require surgical correction. Tibial plateau fractures were originally termed a bumper or fender fractures, since they were typically seen with pedestrians being struck by cars. In reality, less than 1/4 of these fractures are caused by this.

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REFERENCES1. Tuite MJ, Kransdorf MJ, Beaman FD, Adler RS, et al. Acute Trauma to the Knee. From: Expert Panel on Musculoskeletal Imaging. ACR Appropriatenes Criteria. 2014.2. Mustonen AO, Koskinen SK, Kiuru MJ. Acute knee trauma: Analysis of Multidetector Computed Tomography Findings and Comparison With Conventional Radiography.

Acta Radiol. 2005;46(8):866-874.3. Markhardt BK, Gross JM, Monu JU. Schatzker Classification of Tibial Plateau Fractures: Use of CT and MR Imaging Improves Assessment. Radiographics. 2009;29(2):

585-597. 4. Ebell MH. A Tool for Evaluating Patients With Knee Injury. Fa, Pract Manag. 2005;12(3):67-70.5. Canty GS and Knapp JF. The Initial Assessment and Management of Peditric Knee, Ankle, and Wrist Injuries. Peditric Emerg Med Pract. 2008;5(8).6. Knipe H and Galliard F. Unicameral Bone Cyst. Radiopedia.org.7. Brautigan B, Johnson D: The Epidemiology of Knee Dislocations. Clin Sports Med. 2000;19:387-397. 8. Moore BR, Hampers LC, Clark KD. Performance of a Decision Rule for Radiographs of Pediatric Knee Injuries. J Emerg Med. 2005;28:257-261.

Teaching Points:1. Knee injuries are very common in Pediatrics and one of the most frequently encountered injuries in the Pediatric Emergency

Department.2. History can be helpful in deliniating where an injury in a knee can be, whether it is ligamentous, meniscal, or boney.3. Become familiar with some of the common physical exam tests that you can do to determine the site of injury when examining

a knee. These tests are qucik, easy, and reliable. Pay particular attention to the neurovascular examination!4. The Ottawa and Pittsburg rules certainly are helpful in trying to decide if an imaging test is needed, BUT they apply to

specific populations and therefore are not universally applicable.5. Plain radiographs of the knee (usually 3 view) are sufficient. When there is concern for a Patellar fracture, obtain a

Sunrise View.6. Ct scannning is useful if there is a complicated fracture. CT angiography is required when there is historical or clinical

evidence of vascular injury. MRI is useful to assess ligamentous and meniscal injuries and is usually obtained as an outpatient.7. Questions? Ask your friendly Pediatric Orthopedist or Pediatric Radiologist...they can help!

Grandmama: “The mother of Gomez... she willingly helps with the dishes, cheats at solitaire and is roughly dishonest... the complexion is dark, the hair is white and frizzy and uncombed... she has a light beard and a large mole... foolishly good-natured... fumbling, weak character... is easily fooled.” -Charles Addams

Case Conclusion: Well, this patient turned out to have a knee contusion and not an intra-articular fracture or a ligamentous or meniscal injury, as was the initial concern. The patient was placed in a velcro knee immobilizer, given crutches, instructions for Ibuprofen therapy, and told to followup with Pediatric Orthopedics. As of this writing, the patient did not show up to the office yet, so I hope she is doing well, which is likely, because most injuries like these tend to improve with time and rest. What is really amazing about this case is the fact that an MRI was obtained in the Emergency Department...this is often not the case but since there was concern about knee stability, an appropriate test to get. This does go to show, though, that sometimes initial radiographic interpretation can be tricky and further imaging may be needed in selected cases.

Remember the bone cyst from our case? Bone cysts (green arrow) are not uncommon are are typically incidental findings. The appearance of a lesion on the xray can give you an idea if it is benign or not. Benign cysts are exactly that, but in some cases, such as the film seen here, they can serve as points for fracture development (yellow arrow).

Bone cysts are easily detected on plain films and further imaging, such as CT scan or MRI are not needed. These cysts are thought to arise due to bone growing defects and can be filled with fluid. They are well-defined, lucent lesions and have no periosteal reaction. Treatment is not needed for asymptomatic lesions, although large lesions or lesions that look prone to fracture can be treated with steroids injection.

Some cysts that have a fracture will have a dependent bone fragment; this is called a “Fallen Fragment Sign.” (Black arrow).

Other lesions can mimic cysts...more on that in a future issue!