Traumatic elbow injuries are commonly encountered in the emergency department setting ~ complexity & clinical significance often go unrecognized at the initial evaluation

15% of emergency department visits for upper-extremity musculoskeletal injuries annually

Orthopedic surgeons frequently use a classification system different from those used by their colleagues in radiology : miscommunication or delay in communication of the most clinically relevant findings

Awareness and detection of these injuries may be improved by a better-developed and more intuitive understanding of the mechanisms that underlie the most common injury patterns

Elbow : 3 primary articulations that provide two degrees of freedom of motion Flexion and extension movements are centered at

the ulnotrochlear articulation pronation and supination are centered at the

radiocapitellar and radioulnar articulations The elbow articulations are stabilized by the

Medial Collateral Ligament (MCL) complex anterior, posterior, and transverse bundles

Lateral Collateral Ligament complexes radial collateral ligament (RCL) lateral ulnar collateral ligament (LUCL) annular ligament

CT 3D lateral view LCL Complex LUCL (red) RCL (blue) Annular ligament

(yellow)

• CT 3D oblique view MCL Bundles•Anterior (red)•Posterior (blue)•Transverse (yellow)

ELBOW INSTABILITY

• VALGUS INSTABILITY MOST COMMONLY RESULTS FROM INJURIES TO THE ANTERIOR BUNDLE OF THE MCL

• WHEN THE ANTERIOR MCL IS INJURED, SECONDARY STABILIZATION IS PROVIDED BY THE FLEXOR-PRONATOR MUSCLES AND RADIOCAPITELLAR ARTICULATION

• NORMAL FUNCTIONAL STRESSES ON THE ANTERIOR MCL ARE THOUGHT TO BE HIGHEST WHEN VALGUS LOADING OCCURS WHILE THE FOREARM IS SUPINATED AND EXTENDED OR FLEXED AT AN ANGLE BETWEEN 0° AND 90°

Injury mechanism involves valgus and pronation stresses after a fall onto an outstretched hand (FOOSH)

Ligament damage is best depicted at computed tomographic (CT) arthrography, magnetic resonance (MR) arthrography, or MR imaging

Elbow trauma Early identification of injuries that can lead to elbow

instability is critical to guide decision making about appropriate treatment

An understanding of the most common injury mechanisms will help direct attention toward the most critical injuries

RADIAL HEAD & NECK INJURY ESSEX LOPRESTI FRACTURE

DISLOCATION DISTAL HUMERUS FRACTURE CORONOID PROCESS FRACTURE OLECRANON FRACTURE ELBOW DISLOCATION TERRIBLE TRIAD MONTEGGIA FRACTURE &

DISLOCATION

Most common elbow fractures in adults approximately 33%–50% of elbow fractures 20% of elbow trauma cases

Most often associated with a FOOSH-type injury mechanism results from axial loading during forearm pronation with

extension or relative flexion of 0°–80° causes the radial head to forcefully impact the

capitellum of the humerus

Mason-Johnston system, radial head and neck fractures morphologic characteristics of the fracture presence or absence of associated dislocation

Mason - Johnston type I injury

Mason-Johnston type II fracture

Uncommonly seen but clinically important 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 The radiographic features of distal radioulnar joint dislocation

can be subtle but a radioulnar distance discrepancy of >5 mm

on lateral radiographs of the injured wrist relative to the contralateral uninjured wrist

axial loading along the forearm

distraction forces at the distal radioulnar joint

comminuted radial head fracture

dorsal subluxation of the distal ulna with widening of the radioulnar distance

medial and lateral structural columns that provide primary axial load-bearing stability to the humerus

Potential injury mechanisms include a direct impact on the elbow with resultant axial loading of the humerus during flexion of various degrees, as well as a FOOSH

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

2 bone columns that provide primary load-bearing support to the arm

AO-ASIF type A1 fracture

mildly displaced medial epicondylar fracture

transverse metaphyseal fracture

AO-ASIF type C1 injury

comminuted intraarticular fracture of the distal humerus

AO-ASIF type C3 fracture

Makes up the anterior margin of the ulnohumeral articulation and serves to resist varus stress and prevent posterior elbow subluxation

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 mechanism of fracture is thought to relate to axial loading translating to shear stress on the coronoid process ~ commonly seen in FOOSH-type injuries

Fractures of the anteromedial facet are a commonly seen coronoid process fracture pattern, often with associated injuries of the MCL (which inserts on the sublime tubercle of the medial coronoid base) that lead to the development of varus and posteromedial rotatory instability or PLRI (

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

comminuted fracture (arrow) extending through the anteromedial facet of the coronoid process, a finding of an

O’Driscoll type II fracture

fracture of the anteromedial facet of the ulnar coronoid process

Olecranon, which forms the posteroinferior margin of the ulnohumeral articulation, functions as a buttress preventing anterior dislocation of the elbow

Mechanism : Axial loading of the humerus by an impact on the elbow

during flexion of 90° >>>> Complex forced hyperextension injuries Simultaneously opposing contraction of the brachialis and

triceps, or a fall onto a partially flexed elbow, can cause olecranon fractures and triceps avulsion injuries

Patients with nondisplaced fractures that are les 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.

comminuted fracture of the olecranon avulsion fracture of the olecranon at the site of triceps tendon insertion

Second most common type of joint dislocation in adults, after shoulder dislocation

Classified according to the direction of movement and described as either simple or complex, depending on the absence or presence of an associated fracture

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

simple posterior elbow dislocations complex posterior elbow dislocations

Computer-generated images of the elbow show the stages of posterior elbow subluxation and

instability

MR arthrography demonstrates disruption of the RCL and LUCL after reduction for posterior dislocation

lateral capitellum and lateral epicondyle, an injury produced by impact of the radial head.

Full-thickness tears of the MCL and LUCL complex

combination of posterior elbow dislocation with radial head fracture coronoid process fractures

associated with extensive ligament damage

chronic instability and severe arthritis

coronoid process fracture fragment (arrowhead).

TERRIBLE TRIAD

comminuted radial head fracture (arrow)

Monteggia injuries are classified within the Bado system Direction of dislocation Angulation of the ulnar fracture fragment Presence or absence of an associated fracture of

the radius

fracture of the proximal ulna in association with anterior dislocation at the radial head

any ulnar fracture with radiocapitellar dislocation

Bado type I Monteggia fracture

transverse fracture of the ulnar diaphysis (arrowhead) with anterior angulation of the apex and predominantly anterior dislocation of the radial head (arrow),

Evaluation of traumatic elbow injuries Radiographic detection of bone abnormalities Inference of potential associated secondary occult bone and soft-

tissue injuries

Understanding of the most common injury mechanisms

Radiologist’s

direct the early imaging evaluation as appropriate to facilitate detection of the most clinically

relevant associated injuries

adopting the clinically most relevant classification systems used by their colleagues in orthopedic

surgery, radiologists can minimize the potential for inappropriate or delayed treatment