Approach Considerations
Standard radiographic evaluation of the elbow includes imaging in the anteroposterior (AP) and lateral views. Other views may also be helpful. In particular, for lateral condyle fractures, the internal oblique view is often best for demonstrating the fracture and determining the degree of displacement. [5] Because supracondylar fractures may be oriented obliquely on the lateral view, coursing proximally from anterior to posterior, an AP view with cephalad angulation of the x-ray beam may help to better demonstrate such a fracture. Although infrequently used, the capitellum and radiocapitellar joint are best seen on the radiocapitellar view, which is a lateral view with the beam angulated toward the shoulder to project the radiocapitellar joint away from the trochlea and coronoid processes, which otherwise overlap these structures on a standard lateral view. [7]
A study of 62 elementary school baseball players (grades 4-6; ages 9-12 yr) for elbow injuries using MRI found positive findings in 26 (41.9%), all confined to the MCL. Screening was performed using low-magnetic-field (0.2-T) MRI. [13] In a study of 900 young baseball players (aged 7-11 yr), 35.2% reported episodes of elbow pain. [14]
According to Rabiner et al, ultrasonography is highly sensitive for elbow fractures, and a negative ultrasound may reduce the need for radiographs in children with elbow injuries. Of 130 patients (mean age, 7.5 yr), 43 (33%) had a radiograph result positive for fracture. A positive elbow ultrasound had a sensitivity of 98% and a specificity of 70%. [16]
Tokarski et al found that use of conventional radiography may be reduced in patients with a low clinical concern for fracture and normal elbow ultrasound. In the study, after clinical examination and before radiography, pediatric emergency physicians performed elbow US of the posterior fat pad and determined whether radiography was required. The overall sensitivity of elbow US was 88%. Elbow US combined with clinical suspicion for fracture had a sensitivity of 100%. In addition, elbow US took a median of 3 minutes, while elbow radiography took a median of 60 minutes. [17]
Evaluation of soft tissues and joint effusions
Evaluation of the soft tissues is important in elbow trauma. Localized soft tissue swelling over the lateral aspect of the elbow should heighten the suspicion for a possible lateral condyle fracture. Similarly, medial epicondyle avulsion fractures are often accompanied by localized soft tissue swelling in the medial aspect of the elbow.
Displacement of the elbow fat pads is an important indicator of an elbow joint effusion (see below). The radiographic posterior fat pad sign is one of the signs most frequently used for occult elbow fracture. [49]
Fat pad signs indicate an elbow joint effusion. Lateral view shows the posterior fat pad, which is always abnormal when seen with the elbow positioned in right-angle flexion. The anterior fat pad is demonstrated and is abnormally elevated. Although the anterior fat pad may be seen without an effusion, it should not be elevated to this degree.
The elbow fat pads are situated external to the synovium and within the fibrous external joint capsule; the posterior fat pad is located in the olecranon fossa and the anterior fat pad in the coronoid fossa. When the elbow is flexed, the posterior fat pad lies deep within the olecranon fossa and is hidden from view by the medial and lateral condyles. Hence, depiction of the posterior fat pad indicates outward displacement by a joint effusion. With elbow extension, the olecranon moves into the olecranon fossa, displacing the fat pad outward, and hence visualization of the posterior fat pad as a sign of effusion is valid only if the elbow is flexed. The coronoid fossa is not as deep as the olecranon fossa, and hence the anterior fat pad may be seen just anterior to the distal humeral cortex even without an effusion. However, if the anterior fat pad is angled outward, it indicates an elbow effusion.
The presence of an elbow effusion alone does not indicate a fracture. In the setting of acute trauma, the presence of an elbow effusion strongly suggests a hemarthrosis, often from a fracture. In other settings, the etiology may be different. Joint effusions resulting from septic arthritis or juvenile rheumatoid arthritis displace the fat pads, and patients with hemophilia often have an elbow hemarthrosis in the absence of fracture or trauma. In addition to circumstances in which visualization of the fat pad may be due to processes other than fracture, there are also circumstances in which the fat pads are not visualized, even though a fracture is present. If the joint capsule is torn by the fracture fragments, blood may escape from the joint, preventing joint distension and fat pad displacement. Marked edema may also obscure the fat pads, preventing their recognition even though they are displaced. Extra-articular fractures, such as those of the medial epicondyle, also do not result in hemarthrosis.
Approximately 70-90% of children with an elbow joint effusion following trauma have a fracture as demonstrated on the initial or follow-up radiographs. In most cases, the fracture is identified initially. A more important question concerns the risk of an occult fracture in those patients with an elbow effusion and no fracture is seen on initial examination.
Using sclerosis or periosteal new bone to indicate a healing fracture, Morewood initially estimated the risk of occult fracture in this setting to be approximately 30%. [50] Subsequent studies have shown considerable variability in this risk. Skaggs et al found healing fractures in 76%, supporting the concept of considering the presence of an effusion to be essentially indicative of an occult fracture. [51] More recently, Donnelly et al reported that the incidence of healing fracture on follow up was only 17%, with the difference likely related to improved radiographic technique and interpretive criteria for recognizing fractures initially. [52] Using multidetector CT at the time of initial injury, Chapman et al found fractures in approximately 50% of children with a postramatic elbow effusion but no fracture seen radiographically. [53]
Hence, although the presence of a posttraumatic elbow effusion in children raises the possibility of an occult elbow fracture, this situation is not synonymous with an occult fracture, as it seems equally likely that a fracture is not present. The clinical decision as to which patients need to be treated for a presumed fracture must be made on the basis of clinical and radiographic findings and knowledge of the associated risks.
The absence of an effusion in children is strong evidence against an intra-articular fracture. Although a torn capsule or marked edema may produce a false-negative fat pad sign, in these circumstances an obvious fracture is usually present. However, in adults, a significant number of fractures are not associated with an identifiable effusion. Therefore, the negative predictability of this sign is less useful in adults than in children. [54]
Use of the anterior humeral and radiocapitellar lines
Two lines may be drawn on radiographs to help in evaluating elbow trauma: the anterior humeral line and the radiocapitellar line (see below).
Normal lines. Lateral view shows the 2 lines used for radiographic analysis in patients with elbow trauma. The solid anterior humeral line is drawn along the anterior cortex of the distal humeral metaphysis and should pass through the middle third of the capitellum. Passage of the anterior humeral line either anterior to the capitellum or through the anterior third of the capitellum demonstrates that the capitellum is positioned too far posteriorly; this finding indicates a distal humeral fracture. The dashed radiocapitellar line is drawn through the radial neck and should pass through the capitellum. This relation should be examined on a frontal view as well. Failure of the radiocapitellar line to pass through the capitellum indicates radiocapitellar dislocation.
On a true lateral view of the elbow, a line drawn along the anterior aspect of the distal humeral metaphysis should pass through the middle third of the capitellum, which is also part of the humerus. Since the anterior humeral line evaluates the relative positions of 2 parts of the same bone, malalignment is indicative of a fracture. Specifically, if the anterior humeral line passes either through the anterior third of the capitellum or anterior to the capitellum, it indicates that the capitellum is displaced posteriorly relative to the humeral metaphysis. This displacement most frequently results from an extension-type supracondylar fracture, although posterior displacement of the capitellum may also be seen in lateral condyle fractures.
Although this sign is useful in interpreting findings in most children, caution is needed in young children. When the capitellar ossification center is small, its anterior aspect may still be well within the middle third of the entire capitellum, which is still mostly cartilage. In this case, the anterior humeral line may pass anteriorly relative to the small capitellar ossification center even without a fracture. The exact stage of development at which the capitellum is sufficiently ossified for this sign to be reliable is not certain. Initially, 2.5 years had been suggested along with the indication that occasionally comparison with the position of the capitellum of contralateral elbow may be useful. [28] More recent data suggest that the anterior humeral line reliably passes through the middle third of the capitellum in children older than 4 years. [55]
The radiocapitellar line evaluates the relationship of the proximal radius to the capitellum. Because the radius usually bends in the region of the tuberosity, with the radial neck angled anteriorly and laterally relative to the orientation of the radial shaft, only the most proximal part of the radius should be used for drawing the radiocapitellar line. This line should intersect the capitellum on all views, although in young children, the capitellar ossification center may occupy an eccentric position within the largely cartilaginous capitellum. Since the radiocapitellar line compares the relative positions of 2 adjacent bones, malalignment indicates dislocation.
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Normal proximal radial metaphyseal notch. Note the normal notchlike step off of the lateral aspect of the proximal radial metaphysis.
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Normal radial tuberosity. (A) On the lateral view, the radial tuberosity is seen en face and appears as a lytic defect. (B) On the frontal view, radial tuberosity is clearly recognizable. This view also demonstrates the normal angulation between the radial neck and shaft.
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Fat pad signs indicate an elbow joint effusion. Lateral view shows the posterior fat pad, which is always abnormal when seen with the elbow positioned in right-angle flexion. The anterior fat pad is demonstrated and is abnormally elevated. Although the anterior fat pad may be seen without an effusion, it should not be elevated to this degree.
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Normal lines. Lateral view shows the 2 lines used for radiographic analysis in patients with elbow trauma. The solid anterior humeral line is drawn along the anterior cortex of the distal humeral metaphysis and should pass through the middle third of the capitellum. Passage of the anterior humeral line either anterior to the capitellum or through the anterior third of the capitellum demonstrates that the capitellum is positioned too far posteriorly; this finding indicates a distal humeral fracture. The dashed radiocapitellar line is drawn through the radial neck and should pass through the capitellum. This relation should be examined on a frontal view as well. Failure of the radiocapitellar line to pass through the capitellum indicates radiocapitellar dislocation.
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Typical supracondylar fracture. Fracture is obvious on both the anteroposterior (A) and lateral (B) views. Lateral view demonstrates an abnormal relation of the capitellum to the anterior humeral line, which passes along the anterior margin of the capitellum. Compare these images with the lateral view of the contralateral elbow (C), which shows the anterior humeral line passing normally through the middle third of the capitellum.
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Typical supracondylar fracture. Anteroposterior (A) and lateral (B) views. Note the abnormal relation of anterior humeral line on the lateral view.
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Supracondylar fracture, type 3. Anteroposterior (A) and lateral (B) views show significant lateral and posterior displacement of a distal fragment.
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Supracondylar fracture. Anteroposterior view shows disruption of the medial cortex.
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Supracondylar fracture. Initial lateral view (A) shows an abnormal anterior humeral line indicative of a fracture. On the initial anteroposterior view (B), the fracture is subtle and is seen only medially. Follow-up anteroposterior (C) and lateral (D) views demonstrate the fracture better. On the anteroposterior view (C), the fracture may clearly be seen to extend all of the way across the metaphysis.
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Supracondylar fracture. Cubitus varus. (A) Anteroposterior view shows a varus deformity of the distal humerus from a prior supracondylar fracture that has fully healed. (B) On the lateral view, the capitellum remains posteriorly positioned, a finding typical of a previous supracondylar fracture.
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Baumann angle. A 5-year-old boy with previous left distal humeral supracondylar fracture. (A) Anteroposterior view of the left elbow. (B) Comparison anteroposterior view of right elbow. Although the Baumann angle usually is defined as the angle between the growth plate for the capitellum and a line drawn perpendicular to the humeral shaft, the need to draw the perpendicular line can be avoided by using the complement of the angle between the capitellar growth plate and the humeral shaft. In this patient, the uninjured right elbow has a Baumann angle of 12°, and the previously injured left elbow has a Baumann angle of only 2°, suggesting 10° of varus deformity of the left distal humerus.
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A 5-year-old child with type III supracondylar fracture and brachial artery injury. (A) Lateral view of initial radiographs shows type III supracondylar fracture with marked posterior and proximal displacement of the distal fragment. (B) Lateral intraoperative image shows reduction and pinning of the fracture, which is well aligned. However, distal pulses remained absent. At surgical exploration, the brachial artery was transected at the level of the fracture. (C) Arteriogram shows abrupt termination of contrast in the brachial artery proximal to the level of transection, suggesting spasm and thrombosis. More distally (D and E), there is reconstitution of the radial and ulnar arteries from collaterals that supply the palmar arch.
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An 18-month-old child with buckle-type distal humeral supracondylar fracture and an associated distal radial metaphyseal buckle fracture.
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Lateral condyle fracture. Initial anteroposterior (A) and lateral (B) views show a nondisplaced lateral condyle fracture. A subsequent anteroposterior view (C) shows lateral displacement of a distal fragment. An anteroposterior tomogram (D) obtained at that time shows both the displacement and the course of the fracture line through the epiphysis to the articular surface of the trochlea. Most patients with lateral condyle fractures are younger, and the epiphyseal extension of the fracture is within the growth cartilage and thus not identifiable on plain radiographs.
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Lateral condyle fracture passing through the ossified portion of the capitellum. Anteroposterior view shows the lateral condyle with a fracture line passing through the metaphysis and capitellum, crossing the growth plate.
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Displaced lateral condyle fracture. Anteroposterior view shows an obvious lateral condyle fracture with lateral displacement of the fragment, rotation, and downward displacement caused by muscular traction.
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Subtle lateral condyle fracture. Anteroposterior (A) and lateral (B) views. In this patient, the only sign of the fracture is the thin metaphyseal flake on the anteroposterior view.
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Lateral condyle fracture. Anteroposterior (A) and lateral (B) views. On the lateral view, cortical disruption is usually seen posteriorly rather than anteriorly as in supracondylar fractures.
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Fat-suppressed T2-weighted coronal MRI shows that the fracture extends through the metaphysis into the epiphysis, although the articular surface remains intact.
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Lateral condyle fracture with instability. Initial anteroposterior (A) and lateral (B) views show a nondisplaced lateral condyle fracture. Subsequent views (C and D) show lateral and posterior displacement of a distal fragment.
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A 13-year-old youth with nonunion of lateral condyle fracture and subsequent ulnar neuropathy. (A) Anteroposterior radiograph shows the displaced lateral condyle and cubitus valgus. (B and C). T1-weighted MRi showx lack of osseous union. (D) Postoperative anteroposterior radiograph shows improved alignment and healing.
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Milch II lateral condyle fracture with elbow dislocation, frontal (A) and lateral (B) views. The distal fracture fragment is displaced laterally and posteriorly. Displacement of the lateral trochlear ridge has also resulted in elbow joint instability with dislocation of the olecranon laterally and posteriorly. Radiocapitellar alignment remains normal.
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Lateral condyle and olecranon fractures. Anteroposterior (A) and lateral (B) views show combined fractures of the distal humeral lateral condyle and olecranon process of the ulna.
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Medial epicondyle avulsion fracture in an 11-year-old girl with an avulsion of part of the left medial epicondyle (A). Compare the simultaneous view of the uninjured right elbow (B) and a previous view of the left elbow obtained when the patient was 10 years of age (C).
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Medial epicondyle fracture with distal displacement of a fracture fragment. Anteroposterior views of the injured left elbow (A) compared with the uninjured right elbow (B).
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Medial epicondyle fracture with entrapment in an 8-year-old boy. Anteroposterior (A) and lateral (B) views of the injured right elbow compared with anteroposterior (C) and lateral (D) views of the uninjured left elbow. Note the normal position of the medial epicondyle in left elbow, which is not seen in the right elbow.
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Medial epicondyle avulsion fracture with entrapment in an older patient. (A) Anteroposterior view. (B) Anteroposterior contralateral comparison. Note the presence of the normal trochlear ossification center in this patient, which was not present in the younger patient. For the injured elbow (A), the entrapped medial epicondyle is distal to the trochlea and is absent from its normal position. For the normal elbow (B), note the normal position of the medial epicondyle along the medial aspect of the distal humeral metaphysis.
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A 4-year-old child with medial epicondyle fracture. (A) Anteroposterior radiograph shows avulsion and distal displacement of a portion of the left medial epicondyle ossific nucleus. MRI coronal T2* gradient echo (B) and axial fat suppressed T2-weighted (C) images better show the extent of the fracture through the cartilaginous aspect of the medial epicondyle.
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Medial condyle fracture. Anteroposterior (A) and lateral (B) views. Vertically oriented fracture begins along the medial aspect of the distal humeral metaphysis and extends to the growth plate. Similar to lateral condyle fractures, the fracture continues through the epiphysis, but it cannot be seen in this patient because the entire trochlea is still cartilage and has not yet become ossified.
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Medial condyle fracture with markedly rotated distal fragment in a 7-year-old boy. (A) Anteroposterior, (B) oblique, and (C) lateral views show markedly rotated distal fracture fragment of this medial condyle fracture. Note associated proximal radial metaphyseal fracture.
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Transphyseal fracture. Anteroposterior (A) and lateral (B) views of the injured left elbow with anteroposterior (C) and lateral (D) views of the right elbow for comparison. The capitellum (along with the remainder of the cartilaginous epiphysis) is medially and posteriorly displaced relative to the metaphysis. Radiocapitellar alignment remains normal.
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Transphyseal fracture. Anteroposterior (A) and lateral (B) views. The position of the tiny ossification center for the capitellum suggests that it is displaced posteriorly; this is confirmed on the arthrogram (C).
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Transphyseal fracture. Anteroposterior (A) and lateral (B) views. Transcondylar fracture with typical posterior and medial displacement of the distal fragment. On the lateral view, a thin metaphyseal flake is present posteriorly and indicates a Salter-Harris type II injury rather than the usual Salter-Harris type I injury.
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Transphyseal fracture. (A) Initial anteroposterior view shows typical medial displacement of the capitellum and forearm bones. (B) Subsequent radiograph shows abnormality of the medial condyle and varus deformity from a growth plate injury.
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T-condylar fracture in 15-year-old youth. (A) Anteroposterior view shows vertically oriented fracture separating the medial and lateral condyles. The fracture extends to the central groove of the trochlea, medially to the lateral crista. The medial and lateral columns are more separated proximally than distally. In addition to the major distal fragments, small comminuted fragments are noted proximally. (B) The lateral view shows posterior displacement and angulation of the distal fragments, appearing similar to a type III supracondylar fracture.
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Radial neck fracture. Anteroposterior view shows a mildly abnormal angular configuration of the lateral aspect of the proximal radial metaphysis. This finding is indicative of a nondisplaced fracture.
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Displaced proximal radial fracture. Anteroposterior view shows a Salter-Harris type II fracture of the proximal radius with lateral and distal displacement of the radial head, which is positioned along the lateral aspect of the proximal radial metaphysis.
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Olecranon avulsion fracture. Lateral view in a patient with osteogenesis imperfecta who has had bilateral recurrent fractures in the same region. The lucent cleft in the fracture fragment is the normal olecranon growth plate. The avulsed proximal fracture fragment is proximally retracted by the triceps muscle.
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Olecranon fracture. (A) On the anteroposterior view, the fracture is seen as a longitudinal lucent line through the medial aspect of the proximal ulna. (B) On the lateral view, a small fracture line is present at the tip of the proximal ulna, and subtle discontinuity of the posterior cortex is seen.
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Subtle olecranon fracture. Anteroposterior (A) and lateral (B) views. Fracture is at the tip of the ossified portion of the olecranon process.
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Posterolateral elbow dislocation. (A) Note the avulsion of the medial epicondyle, which projects just distal to the trochlea on the anteroposterior view. (B) Lateral view.
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Posterolateral elbow dislocation, lateral view. In addition to the elbow dislocation, avulsion of the medial epicondyle is noted projecting posterior to the capitellum. Note the small fragment of metaphysis attached to the medial epicondyle; this finding indicates a Salter-Harris type II injury.
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In a Monteggia fracture type 3, the radial head is dislocated, primarily laterally and slightly anteriorly. (A) Anteroposterior view. (B) The ulnar fracture has apex lateral angulation and is well aligned on the lateral view.
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Monteggia fracture type I. Lateral view of injured forearm (A) shows anterior dislocation of the radial head and convex anterior bowing of the ulna, which is most apparent when compared with the contralateral uninjured forearm (B).
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Monteggia variant. Anteroposterior (A) and lateral (B) views. An ulna fracture with apex anterior angulation is present. Apparent anterior dislocation of the proximal radius, as seen on the lateral view, is actually a proximal radial fracture with anterior displacement of the neck and shaft relative to the poorly visualized radial head that still articulates normally with the capitellum.
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Pseudo-Galeazzi fracture. Anteroposterior (A) and lateral (B) views. A radial fracture with apex anterior angulation is present. Anterior displacement of most of the distal ulna relative to the wrist is due to a distal ulnar growth plate fracture, with anterior displacement of the metaphysis relative to the epiphysis, which still articulates normally with the wrist. The distal ulnar epiphysis is best depicted on the anteroposterior view, on which it is seen to overlap the ulnar metaphysis. On the lateral view, the distal ulnar epiphysis is largely obscured by the distal radius. The smooth end of the ulna is the metaphysis ending at the physial fracture.
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Combined lateral condyle and olecranon fractures. Initial anteroposterior (A) and lateral (B) views show an obvious lateral condyle fracture and a relatively subtle olecranon fracture. On an anteroposterior view obtained after reduction of the lateral condyle fracture (C), the olecranon fracture is more obvious.
