Tag Archive | musculoskeletal

CRITOE – the important mnemonic used to remember the names and…

CRITOE – the important mnemonic used to remember the names and order of appearance of the six elbow ossification centers. Elbow trauma is common in childhood and knowing CRITOE can be critical to detecting important pathology. This video tutorial includes two abnormal teaching cases which start at 3:31.

C – capitellum : 1 year

R – radial head : 3 years

I – internal (medial) epicondyle : 5 years

T – trochlea : 7 years

O – olecranon : 9 years

E – external (lateral) epicondyle : 11 years

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QUIZ: 8 month old boy with 10 day history of wrist swelling….

QUIZ: 8 month old boy with 10 day history of wrist swelling. What is the ‘not-to-be-missed’ diagnosis? Click for ANSWER

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Arcuate sign – a subtle but important avulsion fracture of the…

Arcuate sign – a subtle but important avulsion fracture of the proximal fibula at the site of arcuate ligament complex insertion. It is associated with cruciate ligament injury in around 90% of cases and represents an unstable posterolateral corner injury. When detected, the arcuate sign should prompt further evaluation with MRI and referral to an orthopaedic surgeon. 

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Shepherd’s crook deformity – refers to a distinctive…

Shepherd’s crook deformity – refers to a distinctive abnormal contour of the proximal femur in the setting of fibrous dysplasia.  As the bone deforms the angle made between the neck of the femur and the femoral shaft decreases (coxa vara) and the bone becomes rounded simulating the appearance of a shepherd’s crook, a stick with a C-shaped end carried by shepherd’s particularly common in biblical times.

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Absent bow tie sign – a sagittal MRI knee sign of a displaced…

Absent bow tie sign – a sagittal MRI knee sign of a displaced meniscal tear (often bucket handle type). Normally the second (or even third) image through a meniscus ressembles the appearance of a bow tie with the central portion thinning out towards the inner free edge (left image, third slice of meniscus). When a bow tie is not seen on the second image then the absent bow tie sign is positive (right image) and a search for a displaced meniscus should ensue – by looking for a fragment-in-notch sign or double PCL sign.   

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Celery stalk sign – describes the appearance of an anterior…

Celery stalk sign – describes the appearance of an anterior cruciate ligament that has undergone mucoid degeneration (a common phenomenon). Its low signal longitudinal fibers are separated from each other by higher signal mucinous material simulating the appearance of celery. It is important to differentiate mucoid degeneration from ACL tear where there will be high signal but absent or disrupted low signal fibres.   

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Lightbulb sign – refers to the abnormal AP radiograph appearance…

Lightbulb sign – refers to the abnormal AP radiograph appearance of the humeral head in posterior shoulder dislocation. When the humerus dislocates it also internally rotates such that the head contour projects like a lightbulb. Because the sign is subtle it is often missed by the untrained observer. Axillary view (bottom right) demonstrates the posterior dislocation much more obviously. 

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Protrusio acetabuli – the cool way of saying acetabular…

Protrusio acetabuli – the cool way of saying acetabular protrusion. Refers to the inward bulging of the acetabulum into the pelvis usually with resultant over-covering of the femoral head. The deformity may be due to trauma but in many cases it is a sign of an underlying disease such as rheumatoid arthritisankylosing spondylitisricketsPaget’s disease and osteogenesis imperfecta. The above patient had Marfan syndrome.

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Lipohaemarthrosis – literally means fat and blood within a…

Lipohaemarthrosis – literally means fat and blood within a joint. Its presence implies an intra-articular fracture with marrow fat having leaked out into the joint. Because fat is less dense than blood it separates on top creating a perfectly straight line known as the FBI sign (Fat-Blood Interface). The sign is best seen on lateral horizontal beam images of the knee within the suprapatellar pouch. The above patient has a tibial plateau fracture

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Throckmorton sign – when the penis points in the direction of…

Throckmorton sign – when the penis points in the direction of unilateral disease on a pelvic radiograph. Also known as the John Thomas sign, when present it is very important for radiologists to report it so as to improve overall morale amongst medical staff. A variant of this sign is the Mark Morton sign when the penis is unusually small (poor Mark). Neck of femur fracture is one on the most common pathologies indicated by the Throckmorton sign, however many rarer entities have been found including the above example of a femoral enchondroma in a patient with Muffucci syndrome.

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