The Elbow




Elbow Checklists



Radiographic examination





  • AP



  • External oblique



  • Lateral




Elbow joint effusions and the fat pad sign





  • Visible posterior fat pad



  • Elevation of the anterior fat pad, the sail sign




Common sites of injury in adults





  • Radial head and neck



  • Olecranon



  • Coronoid process of ulna



  • Distal humerus




Common sites of injury in children and adolescents





  • Supracondylar of the distal humerus



  • Salter-Harris type 4 of lateral condyle



  • Avulsion of the medial epicondyle



  • Olecranon




Injuries likely to be missed





  • Monteggia fracture dislocations




    • Missing radial head dislocation




  • Fine, subtle fractures of the radial head and neck



  • Radial head epiphyseal separation




Where else to look when you see something obvious



















Obvious Look for
Ex proximal ulna Dislocation proximal radius
Fx shaft of either radius or ulna Fx or dislocation of the other
Fx radial head and neck Fx olecranon



Where to look when you see nothing at all





  • Look for joint effusion – the fat pad sign.




    • If present intraarticular fracture likely




  • In adults look at




    • Radial head and neck for fine fracture line




      • Make certain you have external oblique view.




    • Check tip of coronoid process for small avulsion.




  • In children check anterior humeral line to




    • Identify subtle supracondylar fracture.






Elbow – the Primer



Radiographic examination





  • AP



  • External oblique



  • Lateral



The three views ( Figure 3-1 ) selected have been proven to disclose the majority of fractures and dislocations. Certain injuries can be inapparent on standard PA ( Figure 3-1 A ) and lateral ( Figure 3-1 B ) projections and may be seen only on the external oblique view ( Figure 3-1 C ). This is particularly true of fractures of the radial head, accounting for over one-half of all fractures (60%) of the elbow in adults.




FIGURE 3-1


Certain injuries can be unapparent on standard posteroanterior ( A ) and lateral ( B ) projections and may be seen only on the external oblique view ( C ).


Normal elbow in children


The presence and sequential appearance of multiple ossification centers in the child’s elbow ( Figures 3-2 A and B ), particularly in the distal humerus, makes for complex and potentially confusing anatomy. The capitellum is the first to appear at 3 to 5 months of age, followed by the medial epicondyle center at 4 to 6 years of age. The trochlear center appears at age 9 to 10 years. Note that the trochlear center never appears before the medial epicondylar center. The last center to appear is the lateral epicondyle at 9.4 to 11.5 years. Note the normal ossification center of the apophysis of the olecranon ( Figures 3-2 C ). This center is multipartite, a normal variant.




FIGURE 3-2


The presence and sequential appearance of multiple ossification centers in the child’s elbow ( A and B ), particularly in the distal humerus, makes for complex and potentially confusing anatomy. Normal ossification center of the apophysis of the olecranon ( C ). This center is multipartite, a normal variant.



Elbow joint effusions and the fat pad sign





  • Visible posterior fat pad



  • Elevation of the anterior fat pad, the sail sign



In the setting of trauma it is very likely that an intraarticular fracture is present if a joint effusion is identified. The presence of a joint effusion is an important clue to an otherwise obscure underlying fracture of the elbow in adults as well as children and adolescents.


Elbow joint effusions are detected on the lateral view ( Figure 3-3 ). The anterior and posterior fat pads reside in the joint capsule. On the lateral view of the normal elbow ( Figures 3-3 A and C ) without a joint effusion, the posterior fat pad is not apparent, while the anterior fat pad is visible but not elevated. In the presence of a joint effusion (hemarthrosis), the fat pads are displaced, and both the anterior and posterior fat pads become visible ( Figures 3-3 B and D ). This is known as the “fat pad sign.” The posterior fat pad is displaced posteriorly, and the anterior fat pad is elevated, often referred to as the “sail sign.” Note the subtle fracture of the radial head ( Figure 3-3 D ).




FIGURE 3-3


Elbow joint effusions. On the lateral view of the normal elbow without a joint effusion ( A and C ), the posterior fat pad is not apparent, whereas the anterior fat pad is visible but not elevated. In the presence of a joint effusion (hemarthrosis), the fat pads are displaced, and both the anterior and posterior fat pads become visible ( B and D ). Note the subtle fracture of the radial head in panel D .



Common sites of injury in adults





  • Radial head and neck



  • Olecranon



  • Coronoid process of ulna



  • Distal humerus



Pattern of search


Diagrams of the elbow ( Figures 3-4 A and B ) pinpoint the common sites of fracture in adults. The most common sites of fracture are identified by broad red lines. Less common sites are designated by fine red lines. Your pattern of search should include all sites.




FIGURE 3-5

Mar 23, 2019 | Posted by in MUSCULOSKELETAL IMAGING | Comments Off on The Elbow
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