The document discusses common elbow injuries seen by orthopedic surgeons and provides details on classifying and treating these injuries. It covers traumatic injuries to the radial head/neck, coronoid process, distal humerus, and the Essex-Lopresti fracture-dislocation. Classification systems help determine appropriate treatment, which may involve conservative treatment or surgery depending on the degree of displacement and bone/soft tissue involvement. Imaging plays an important role in accurate classification to guide clinical management.

1. Traumatic Elbow Injuries:
What the Orthopedic Surgeon
Wants to Know
©RSNA, 2013 • radiographics.rsna.org

2. The elbow consists of three primary articulations that provide two degrees of freedom of
motion.
Flexion and extension movements are centered at the ulnotrochlear articulation, and pronation
and supination are centered at the radiocapitellar and radioulnar articulations.
The elbow articulations are stabilized by the medial (ulnar) and lateral (radial) collateral
ligament complexes .
The medial collateral ligament (MCL) complex is made up of anterior, posterior, and transverse
bundles. The lateral collateral ligament complex is made up of the radial collateral ligament
(RCL), the lateral ulnar collateral ligament (LUCL), and the annular ligament, as well as the
functionally irrelevant accessory collateral ligament.
The ulnohumeral articulation, the anterior bundle of the MCL, and the LUCL are the primary
stabilizing structures of the elbow.
Secondary stabilization is provided by the radiocapitellar articulation, the common flexor-
pronator tendon, the common extensor tendon, and the joint capsule
Functional Anatomy of the Elbow

3. Computer-generated lateral three-dimensional (3D) view of the elbow demonstrates the
normal anatomic configuration of the lateral collateral ligament complex, which includes the
LUCL (red), RCL (blue), and annular ligament (yellow). (b) Computer-generated medial oblique
3D view shows the normal configuration of the anterior (red), posterior (blue), and transverse
(yellow) MCL bundles

4. Common Injury Patterns
Radial Head and Neck Fractures
Radial head and neck fractures are the most common elbow
fractures in adults, comprising approximately 33%–50% of
elbow fractures, and are seen in roughly 20% of elbow trauma
cases.
Radial head and neck fractures are most often associated
with a FOOSH-type injury mechanism that results from axial
loading during forearm pronation with extension or relative
flexion of 0°–80°, which causes the radial head to forcefully
impact the capitellum of the humerus .

5. In reporting radial head fractures by using the Mason-
Johnston system, it is most helpful to describe the degree of
displacement, the amount of articular surface involved, and
the presence of comminution or associated dislocation.
The diagnosis is usually made at initial radiography, with
subtle radial head fractures indicated by the presence of
elevation of the anterior and posterior fat pads , which are
intracapsular but extrasynovial .
Cross-sectional imaging is not usually required for evaluating
isolated radial head fractures, but MR imaging has proved
effective for identifying fractures in adults with a radiographic
finding of joint effusion .

6. Mason-Johnston classification system
type I: characterized by no or only minimal (<2 mm) displacement
type II:defined by displacement of 2 mm or more and articular surface involvement of less than
30%

7. type III, defined by comminution of the radial head; and type IV, defined by associated proximal
radial dislocation. Conservative treatment is usually recommended for type I fractures (green
box) and for type II fractures with a preserved range of motion (yellow box), whereas surgery is
indicated for type II fractures with a poor range of motion and for type III and IV fractures (red
boxes

8. Oblique (a) and lateral (b) radiographs of the elbow demonstrate a nondisplaced radial neck
fracture with anterior and posterior fat pad elevation (black arrows in b), findings indicative of
a Mason-Johnston type I injury. In radial neck fractures, the normal mild concave curvature of
the anterior cortex of the base of the radial head is lost and an abrupt offset between the
radial head and neck (white arrow) is created

9. Lateral radiograph of the elbow during extension demonstrates a displaced radial head fracture
(arrow) that involves less than 30% of the articular surface, a finding indicative of a Mason-
Johnston type II fracture

10. Essex-Lopresti Fracture-Dislocation
An uncommonly seen but clinically important fracture pattern, which
involves a comminuted fracture of the radial head with dislocation of
the distal radioulnar joint and disruption of the interosseous membrane,
producing the oft-cited “floating radius”.
The mechanism is most likely a variation of that present in a FOOSH-
type injury.
Because Essex-Lopresti fractures nearly always require surgical
intervention, their detection is of paramount importance.
The diagnosis is often suspected because of reported wrist pain or
tenderness, which prompts initial radiography .

11. The radiographic features of distal radioulnar joint dislocation can be
subtle, but a radioulnar distance discrepancy of more than 5 mm on
lateral radiographs of the injured wrist relative to the contralateral
uninjured wrist is considered diagnostic.
Radiographically occult injuries of the distal radioulnar joint are not
uncommon, and in ambiguous cases, CT or MR imaging can be helpful in
depicting dynamic instability or soft-tissue injury.
Although CT and MR images showing Essex-Lopresti injuries often
demonstrate comminution of the radial head, which is a surgical
indication, patients with borderline injuries to the radial head may
erroneously receive only conservative therapy if the distal radioulnar
joint injury is not detected.

12. Essex-Lopresti Fracture-Dislocation
Computer-generated 3D view of a
left forearm shows a common Essex-
Lopresti injury mechanism:
a FOOSH produces axial loading
along the forearm (long yellow
arrow), with resultant distraction
forces at the distal radioulnar joint
(short yellow arrows).
Forces are transmitted primarily
through the radial head (red
“starburst”) and interosseous
membrane (red polygon).

13. Frontal radiograph of the elbow depicts a comminuted radial head fracture (arrow).
Lateral radiograph of the wrist shows dorsal subluxation of the distal ulna with widening of
the radioulnar distance (arrow), findings suggestive of distal radioulnar joint dislocation in the
setting of wrist pain

14. Distal Humerus Fracture
Computer-generated 3D view of the
humerus shows the two bone columns
that provide primary load-bearing
support to the arm:
the lateral column, which extends
distally to the capitellum articulation,
And
the medial column, which extends to
the medial epicondyle. Column
disruption compromises structural
stability.

15. With distal humerus fractures, it is most critical to report the salient
radiographic findings that guide treatment: column involvement, the
direction and degree of displacement of epicondylar avulsion fractures
and single-column fractures, and the presence of comminution or two-
column injury.
Radiography generally is sufficient for the initial identification and
classification of distal humerus fractures . However, after a fracture of
the distal humerus is identified at radiography, CT is usually performed
to ensure accurate fracture classification because of the high incidence
of severe injuries that ultimately require surgery.
MR imaging is not usually indicated, because the incidence of
postoperative instability has been shown to be low in most cases of
uncomplicated fracture fixation with adequate bone union, as the
collateral ligament complexes often remain intact at their proximal
attachments on the fractured humerus .

16. Jupiter and Mehne classification system

18. Treatment options for the various types of humeral fracture:
Epicondylar avulsion fractures (type A1 fractures; green box) with
minimal (<1 cm) displacement can be treated conservatively
single-column fractures without comminution (fracture types B1–B3;
yellow boxes) can be treated conservatively at first but will likely
require surgery
comminuted or two-column fractures (types A2, A3, and C1–C3; red
boxes) require surgery

19. (a) Frontal radiograph shows a mildly displaced medial epicondylar fracture (arrowhead) with
soft-tissue swelling, findings of an AO-ASIF type A1 fracture. An associated anteromedial
coronoid facet fracture (black arrow) and a depressed intraarticular radial head fracture (white
arrow), as well as the degree of medial epicondylar fragment displacement, are indications for
surgical repair. (b) Frontal radiograph shows a transverse metaphyseal fracture (arrowhead)
and a minimally displaced intraarticular fracture of the distal humerus (arrow), findings of AO-
ASIF type C1 injury. (c) Frontal radiograph depicts a comminuted intraarticular fracture of the
distal humerus (arrow), an AO-ASIF type C3 fracture

20. The coronoid process makes up the anterior margin of the ulnohumeral
articulation and serves to resist varus stress and prevent posterior
elbow subluxation .
The coronoid process also serves as the site of anterior attachment of
the joint capsule, insertion of the MCL, and insertion of the brachialis
muscle at its anterior aspect .
The coronoid process, which provides static axial stability to the
extended elbow, has been shown to fracture in isolation with axial
loading over the range of 0°–35° of elbow flexion; it also may fracture in
conjunction with the radial head over 0°–80° of flexion .
Coronoid Process Fracture

21. Tiny coronoid process tip fractures most commonly occur as a complication of
subluxation or dislocation, predominantly during axial and posteromedial rotatory
loading, and they may herald additional occult damage to bone or soft tissue (eg,
lateral collateral ligament complex injuries) .
The severity and extent of small coronoid tip fractures therefore cannot be
adequately evaluated with radiography alone , and a radiographic finding of a
seemingly tiny coronoid tip fracture should prompt additional imaging .
Adequate evaluation of coronoid process fractures requires characterization of the
fracture fragment size and the degree of anteromedial facet and potential coronoid
base involvement. CT evaluation of coronoid process fractures is recommended, and
early evaluation with with 3D reconstructions often obtained for full evaluation of
the morphologic characteristics of fractures.
MR imaging can be used to detect bone edema in cases with ambiguous
radiographic or CT findings and to evaluate for soft-tissue injuries relating to isolated
coronoid process fracture, prior elbow subluxation, or frank dislocation .

22. O’Driscoll system
Computer-generated en face 3D view of the coronoid process shows the O’Driscoll fracture
classification system, which comprises three fracture types (I, II, and III) defined on the basis of
their location in the 3D anatomy. Type I injuries involve the coronoid tip and affect
approximately one-third of the coronoid process. Type II injuries are characterized by
anteromedial facet involvement to a varying degree, with more medial involvement
representing a more severe injury subtype. Type III injuries are the most severe, with the
fracture involving at least half of the coronoid process

23. Lateral radiograph of the elbow demonstrates an apparently tiny fracture of the coronoid tip
(arrow).

24. Sagittal (b) and 3D volume-rendered (c) images from subsequent CT depict extension of the
coronoid tip fracture through the anteromedial facet (arrow), a finding that indicates an
increased risk for elbow instability

25. Coronal (a) and axial (b) CT images demonstrate a comminuted fracture (arrow) extending
through the anteromedial facet of the coronoid process, a finding of an O’Driscoll type II
fracture requiring surgical repair to prevent joint instability.

26. Coronal (a) and axial (b) T2-weighted fat-saturated MR images show a fracture of the
anteromedial facet of the ulnar coronoid process (arrow), with high signal intensity
representing edema in the bone and in soft tissue surrounding the distal MCL.

27. Classification of olecranon fractures is based on the presence or absence of
comminution, displacement, and involvement of other osseous structures (eg, the
coronoid process).
Patients with nondisplaced fractures that are less than 2 mm wide, with no increase in
displacement over 90° of flexion or during active extension, can usually undergo a trial
of conservative therapy . Displacement of fracture fragments (with a gap of >2 mm),
increased displacement during elbow flexion or extension, and the presence of
comminution are surgical indications.
The presence of comminution should be specifically emphasized, because it is an
indication for the use of a plate instead of a tension band–wire construct for fixation .
Radiography is generally sufficient for initial and postreduction evaluations , but CT is
often performed in cases in which surgical repair is indicated. MR imaging is
occasionally used in ambiguous cases or when the presence of stress fractures is
suspected.
MR imaging allows excellent evaluation of the triceps tendon and is often indicated in
cases of avulsion-type fracture .
Olecranon Fracture

28. Transverse fractures can be treated with tension banding and Kirschner wires

29. comminuted (b) and oblique (c) fractures are often best managed with plate fixation and
bicortical screw fixation, respectively

30. Coronoid process involvement usually requires medial plate fixation to prevent chronic
instability.

31. Lateral radiograph of the elbow demonstrates a comminuted fracture of the olecranon
(arrow). Comminution and fragment displacement qualify this injury for surgical
treatment.

32. Lateral radiograph (a) and sagittal intermediate-weighted MR image (b) depict an avulsion
fracture of the olecranon at the site of triceps tendon insertion (arrow). The degree of
displacement qualifies this injury for surgical treatment

33. Elbow Dislocation
Elbow dislocation is the second most common type of joint dislocation in adults, after shoulder
dislocation .
Adult elbow dislocations are most commonly posterior in direction. Anterior dislocations of the
elbow are rare and are most often seen in children, in whom they are usually the result of
rebound after posterior dislocation .
Divergent dislocations involve interposition of the distal humerus between the proximal radius
and ulna, with the proximal radius and ulna dislocated in divergent directions .
Posterior dislocations are often associated with radial head fractures because of axial
compression on the capitellum . Coronoid process fractures are also commonly seen and likely
are due to a shearing mechanism where the trochlea impacts the coronoid process tip during
dislocation . Flexor-pronator and brachialis muscle injuries are commonly seen and can
contribute to instability.

34. Elbow Dislocation
Lateral radiographs show simple (a) and complex (b) posterior elbow dislocations. Simple
dislocations may be treated conservatively, but the presence of an associated comminuted
radial head (Mason-Johnston type IV) fracture in complex dislocations (arrow in b)
necessitates surgical repair.

35. Computer-generated images of the elbow show the stages of posterior elbow subluxation and
instability. (a) Stage 0 injuries are characterized by baseline anatomic alignment with no
instability. (b) Stage I injuries involve damage to lateral ligamentous structures such as the
LUCL and RCL, with resultant PLRI. (c) Stage II injuries involve capsular and lateral soft-tissue
damage that leaves the trochlea perched on the coronoid process. (d) Stage III injuries are
defined by varying degrees of damage to medial structures, especially the anterior bundle of
the MCL, with frank posterior elbow dislocation

36. Coronal intermediate-weighted fat-saturated image from MR arthrography demonstrates
disruption of the RCL and LUCL, with marked contrast material accumulation around the
lateral humeral condyle (arrow). Disruption of the LUCL has been associated with PLRI

37. Coronal short inversion time inversion-recovery (a) and gradient-echo (b) MR images obtained
after reduction for posterior dislocation depict a bone marrow contusion (arrow in a) in the
lateral capitellum and lateral epicondyle, an injury produced by impact of the radial head. Full-
thickness tears of the MCL (arrow in b) and LUCL complex (arrowhead in b) also are seen

38. Postreduction lateral radiograph of the elbow demonstrates the drop sign (arrow), an
appearance created by an ulnohumeral distance of 4 mm or more. This finding may be
predictive of the development of PLRI.

39. Postreduction lateral radiograph shows a comminuted radial head fracture (arrow) and coronoid
process fracture fragment (arrowhead) in the setting of severe complex posterior elbow
dislocation, injuries known as the Terrible Triad .
The combination has been described as the “terrible triad” because it is associated with
extensive ligament damage that could result in chronic instability and severe arthritis if
inadequately treated .

40. Monteggia fracture-dislocation was initially described as a fracture of
the proximal ulna in association with anterior dislocation at the radial
head but was later redefined as any ulnar fracture with radiocapitellar
dislocation .
Monteggia injuries are classified within the Bado system on the basis of
the direction of dislocation, angulation of the ulnar fracture fragment,
and the presence or absence of an associated fracture of the radius .
Monteggia Fracture and Dislocation

41. Bado classification of Monteggia fractures
type I, fracture of the proximal or middle third of the ulna with anterior angulation of the apex
and associated anterior dislocation of the radial head (a); type II, fracture of the proximal or
middle third of the ulna with posterior angulation of the apex and associated posterior
dislocation of the radial head

42. type III, fracture of the proximal ulna with lateral dislocation of the radial head (c); and type
IV, fracture of the proximal or middle third of the ulna and radius with anterior dislocation
of the radial head

43. Oblique frontal radiographic view of the forearm shows a transverse fracture of the ulnar
diaphysis (arrowhead) with anterior angulation of the apex and predominantly anterior
dislocation of the radial head (arrow), findings of a Bado type I Monteggia fracture

44. Conclusion
The evaluation of traumatic elbow injuries requires not only the radiographic
detection of bone abnormalities but also the inference of potential associated
secondary occult bone and soft-tissue injuries that could place the patient at risk for
chronic joint instability.
An intuitive understanding of the most common injury mechanisms will help direct
the early imaging evaluation as appropriate to facilitate detection of the most
clinically relevant associated injuries.
The radiologist’s role as a consultant also necessitates that imaging findings be
communicated in the most clinically relevant way to ensure effective early
evaluation and intervention.
By adopting the clinically most relevant classification systems used by their
colleagues in orthopedic surgery, radiologists can minimize the potential for
inappropriate or delayed treatment