EM REMS

A couple days ago I asked what other imaging modality is recommended with knee dislocations.  The answer is CT angiogram of the lower extremity.  As you recall we had an image of a patient with a knee dislocation, here is his CT angiogram of the left lower extremity:

This image shows no evidence of injury to the popliteal artery with contrast reaching the distal vasculature.  Please note that the bolus timing was optimized only for the left side thus the right side is not completely imaged.  Remember this imaging modality in knee dislocations to rule out vascular injury.

I came across an article written in 2007 published in Emergency Medicine Clinics of North America which has a good review section on knee dislocation (1).  The article also discusses other important emergency medicine orthopedic injuries.  According to the article, popliteal artery injury occurs in approximately 40% of high-energy knee dislocations.  Peroneal nerve injury occurs in 14-35% of cases.  Some classic mechanisms of dislocation include when a car bumper strikes the femur above a planted leg and when the knee strikes the dashboard in a high-energy frontal MVC.  Patients with findings consistent with arterial injury need emergent vascular surgery, ideally within 6 hours.  Compartment syndrome can occur and a delay in repair can result in need for amputation.  Furthermore, delayed spasm or compartment syndrome can occur and it is recommended that all patients be observed for 24 hours with serial clinical exams.

Author:  Russell Jones, MD

References

1.  Newton EJ, Love J.  Emergency Department Management of Selected Orthopedic Injuries.  Emerg Med Clin N Am 25; 2007: 763-793.

This patient has a knee dislocation with an avulsion fragment seen in the joint space.  The tibia/fibula are both rotated facing medial with the patella displaced to the medial side as well.  Lateral projections were unable to be obtained due to the patient being very uncomfortable however clinically the tibia seemed to be posterior to the distal femur. 

MRI later showed complete tears of the anterior and posterior cruciate ligaments as well as the medial collateral and fibular collateral ligaments.  It also showed the tibial plateu fracture and a compression fracture of the distal femur.

What other imaging would you recommend for this patient in the emergent setting?

Author:  Russell Jones, MD

This is an image provided by one of our UC Davis resident physicians:

Great example of a lunate dislocation!

The key portion of the film above is the half-moon shaped bone (Lunate) which is dislocated in the palmar direction and has a “spilled teacup” appearance (it is rotated from its normal position with the concave portion of the bone facing the distal fingers).

The AP view on this patient is also interesting.  It shows a “Piece of pie” sign, also frequently found with lunate dislocation.  This is an abnormal triangular hyperdensity seen in the lunate on the AP projection (can also be seen in perilunate dislocation).

The distinguishing feature of this radiograph to differentiate between perilunate and lunate dislocation is the alignment on the lateral projection.  The capitate and distal radius are still aligned, the lunate is dislocated.  In a perilunate dislocation the lunate will not have a “spilled teacup” rotation and the capitate will be dorsally displaced off the alignment of the distal radius.  An example of a perilunate dislocation:

Tip:  on lateral wrist xrays, always draw a line through the distal radius, lunate, and capitate.  It should look like an apple sitting in a teacup on a saucer.

Author:  Russell Jones, M.D.

Image Contributor:  Dane Stevenson, M.D.

This gentleman was in a trauma and sustained an acetabular fracture.  Here is a standard AP pelvis, “Judet” view, CT with bone windows, and a CT 3-dimensional reconstruction image.  On the plain films you can see contrast in the bladder, this is residual from a urogram looking for bladder injury (no injury identified):

There are several ways to image acetabular fractures:

1.  Standard AP pelvis films:  this is a good screening imaging modality

2.  ”Judet” films:  xray images that can further delineate the extent, type of acetabular fracture.  wikiRadiography Judet Views

3.  CT pelvis with 3-dimensional reconstruction.  This is the “cadillac” of imaging that orthopedic surgeons get the most pre-operative information from.  Judet Views have largely been replaced by this imaging modality as it offers much more information for the surgeon.  On a PACS radiology system the images can be rotated, flipped to see the extent of the injury as if you were holding the pelvis in your hand.  Its pretty awesome.

Keep in mind that fractures of the acetabulum can be occult.  If you obtain plain films that look normal and the patient cannot bear weight, consider CT imaging for a better look.  MRI can also be of value much like an occult femoral neck fracture.

Here is a free, extensive discussion of imaging acetabular fractures (including a discussion about types of acetabular fractures) available online from Radiographics:

Acetabular Fractures

Author:  Russell Jones, M.D.

References

1.  Judet Views.  http://www.wikiradiography.com/page/Judet+Views

2.  Potok PS, Hopper KD, Umlauf MJ.  Fractures of the Acetabulum:  Imaging, Classification, and Understanding.  Radiographics. 1995 Jan; 15(1), 7-23.

I posted a radiograph earlier asking about Bennett’s and Rolando fractures.  This is the patient’s CT obtained later to further characterize the fracture:

This is a Bennett’s fracture pattern.  Bennett’s is a fracture of the base of the 1st Metacarpal that involves the articulation and usually has some dislocation of the CMC (carpal-metacarpal) joint.  This fracture does have slight dislocation at the 1st CMC joint.

The Rolando’s fracture pattern is more comminuted, usually T or Y shaped comminution.  It carries a worse prognosis although the Bennett’s also has high incidence of arthritis even with optimal management.

Author:  Russell Jones, MD

This is a patient with pain in the thumb after punching another person:

Fractures of the base of the 1st (thumb) metacarpal are highly morbid injuries.  Most of these should be operative but many end up with severe arthritis of the MCP joint despite optimal therapy.  The thumb is a very important functional joint especially on the dominant hand, as in this patient.

Radiographically there are several eponym fractures for the base of the 1st metacarpal:  Rolando and Bennett are the most widely discussed eponym fractures.

Which one is this (if either)?

Answer to follow.

Author:  Russell Jones, MD

I can think of only a couple worse places for an Epipen® to accidently be stuck:

This is a pediatric patient that one of my colleagues saw.  Fortunately as you can see from the xray the tip of the needle went right through the bone and exited out the other side and the digit was not ischemic.

Accidental injection of epinephrine into a digit actually occurs somewhat frequently.  There are case reports and articles written on management if the digit is ischemic.  I’ll refer you to one that was published in the UK in 2004:

Velissariou I, Cottrell S, Berry K, Wilson B: Management of adrenaline (epinephrine) induced digital ischaemia in children after accidental injection from an EpiPen. Emerg Med J 2004, 21:387-388.

The article was a summary of three case reports out of the United Kingdom.  They used warm water immersion, topical nitroglycerin, and in one case local injection of 1.5 mg of phentolamine in 1ml of Lidocaine 2% was used with good effect.  Phentolamine is a short acting α blocker and can counteract the α mediated vasoconstriction epinephrine provides.  If you are practicing in the U.S., keep in mind that local Poison Control Centers can be good references if you have questions on management.

Author:  Russell Jones, MD

Image Contributor:  Mary Bing, MD

Another eponym fracture, courtesy of John Neuffer, MD at WVU.  Dr. Neuffer saw a patient with a fall on an outstretched hand (FOOSH) and this was the result:

This is an example of a Colles Fracture.  Colles fracture is a distal radius fracture with dorsal displacement of the distal fracture fragment and wrist.  FOOSH is a popular mechanism of this injury as well as any other mechanism that causes an axial load on the distal wrist with extension of the hand.

There are two other interesting parts of this image:  1.  There is an ulnar styloid fracture  2.  The pisiform is dislocated.

Ulnar styloid fractures are very common with FOOSH mechanism and in conjunction with distal radius fractures.  Common xray findings with a Colles fracture include (1):

• Transverse radius fracture
• Dorsal displacement and angulation
• Radial angulation of the wrist
• Location 1 inch proximal to the radiocarpal joint
• Radial shortening
• Ulnar styloid fracture
• Salter-Harris fractures in children

Pisiform dislocation is rare.  On the lateral view above you can see the pisiform is displaced off the triquetral bone (its only articulation).

This is what it should look like:

Pnormalpisform.png

(Above is a link to Wikipedia.  James Heilman, MD has a post about the pisiform with a great lateral radiograph demonstrating a normal positioned pisiform.  Go check it out!)

Author:  Russell Jones, MD

Image Contributor:  John Neuffer, MD

Thanks to Dr. Neuffer at WVU for the image as well as pointing out a good EM blog for me to follow:  EMchatter.com.  Keep up the good work and send me more good images!

References

1.  Broder JS.  ”Imaging the Extremities.” In: Broder JS.  Diagnostic Imaging for the Emergency Physician.  Elsevier Saunders, 2011.

A little while back I discussed Lisfranc fractures of the foot.  Here is an image depicting a fracture-dislocation through the Lisfranc joint:

This one is not subtle!  You can see that the bases of metatarsals 1-5 are laterally dislocated.  Remember, the Lisfranc joint involves articulation between metatarsals and tarsus (navicular, cuboid, and three cuneiform bones).  A Lisfranc fracture occurs when one or more of the metatarsals are dislocated from the tarsus.

As a reminder of the Lisfranc radiology findings here is a Word® document reminding us of the “Radiology Rules.”  It is in 3X5 card format you can print front and back and have a convenient reminder if you want to carry it with you on your clinical shifts.  That way hopefully we won’t miss the subtle ones…

Radiology Rule Lisfranc

Author:  Russell Jones, MD

I was working peds last night and an 8-year-old male came in with elbow pain after falling on an outstretched hand while playing football.  Another player fell on his elbow at the same time.  He had an obvious deformity and his elbow film is classic for an eponym fracture:

This is a Monteggia fracture-dislocation.  It involves a fracture of the proximal ulna and dislocation of the radial head.

Giovanni Monteggia (1814) originally described this fracture pattern.  It is usually associated with a direct blow or a hyperpronation, extension mechanism.  In this radiograph the radial head dislocation is obvious, however sometimes it can be subtle and missed.  Always draw a line through the radial head and make sure it intersects the capitellum on both the AP and lateral views (radiocapitellar line).  Here is an example of a normal radiocapitellar line:

Author:  Russell Jones, MD