Elbow fractures in overhead athletes are most often caused by low energy trauma, such a fall onto an outstretched hand (FOOSH) and hyperextension or hyperflexion injuries [33]. Nontraumatic upper extremity fractures related to throwing are rare [34, 35]. However, stress fractures arising from repetitive microtrauma are not uncommon. In the following section, a description of fractures of the distal humerus, proximal ulna, and proximal radius, with associated characteristics on imaging, will be given.

The apophysis is a secondary ossification center located outside the joint surface. Injury of the medial epicondylar apophysis occurs almost exclusively in young athletes performing overhead sports and is referred to as the clinical diagnosis Little Leaguer’s elbow [86–88]. The medial epicondyle is relatively weak compared to the increasing muscle strength in adolescents. Therefore, apophysiolysis or apophyseal avulsion fractures are often the consequence of sustained valgus stress forces with traction of the common origins of the flexor muscles at the apophysis, due to repetitive overhead throwing [5, 89, 90]. Moreover, avulsion fractures can also be the consequence of an acute traumatic event such as a dislocation due to FOOSH injury [91].

AP and lateral radiographic images with comparative views of the unaffected side should be used in the initial evaluation [1]. Although these images appear normal in 85 % of cases, they may reveal a hypertrophic medial epicondyle with bony fragmentations and apophyseal widening or complete avulsion from the underlying humerus, with possible entrapment of the fragment in the joint [87, 89].

MRI is not warranted in the initial imaging workup, but can be justified to outline the surrounding structures [92]. MR images in such cases may show bone marrow edema in the apophysis (or distal in the humerus) and tendinopathy of the common flexor tendon. Contrary to previous literature, there is a growing consensus that the ulnar collateral ligament (UCL) is not involved in the pathology of the Little Leaguer’s elbow, but solely associated with valgus extension overload in adult patients (see Sect. 4.3.1) [92].

While traumatic injury may precipitate secondary degenerative arthritis in the elbow, primary degeneration is not associated with acute elbow trauma or rheumatologic disease. Primary degenerative arthritis of the elbow is a relatively rare condition, but occurs to a greater extent in overhead athletes at whom excessive stress on the elbow joint is placed [93, 94]. The pathologic changes that occur in both the radiohumeral and ulnohumeral compartments of the elbow can be divided in three stages [95]. The first stage involves loss and fragmentation of the cartilage due to repetitive impaction of the coronoid process and the tip of the olecranon against the olecranon fossa membrane. As a response to this erosion, hypertrophic bone and cartilage formation results in so-called osteophytes and loose bodies. Osteophytes or bone spurs reduce the amount of joint space needed for a full, pain-free range of motion, giving rise to symptoms as pain, locking, or reduced elbow motion. In the final stage, the impingement caused by these small protuberances (particularly in the olecranon fossa) leads to distortion and in most severe cases to contracture of the elbow joint. Arthroscopic intervention with removal of the eroded bone and its fragments is the best treatment option to prevent further degeneration of the elbow [96]. Plain radiography and computed tomography are the modalities of choice when assessing the condition of the elbow.

Two views in plain radiography are usually sufficient for the initial evaluation of primary osteoarthritis. Standard lateral radiographs allow identification of the most frequent features of the osteoarthritic elbow (i.e., osteophytes of all involved bony structures, thickening of the olecranon fossa membrane, and joint space narrowing). The anteroposterior view in addition enables the assessment of the olecranon fossa membrane [97].

In preoperative planning, computed tomography (CT) is favorable when heterotopic ossification or intra-articular loose bodies are suspected [93]. More advanced three-dimensional CT scans can specifically determine the size, location, and bony architecture of the hypertrophic bone spurs and loose bodies [97, 98].

Shot blocking of a ball with the forearm fully extended induces repeated hyperextension trauma of the elbow, mostly seen in goalkeepers of handball and soccer [99]. The injury pattern resembles elbow lesions in overhead athletes: repeated impaction of the posteromedial olecranon leads to arthritic changes with cartilage damage, osteophyte formation, and intra-articular loose bodies [100]. The presence of these pathological alterations can be confirmed by radiological evaluation. Soft tissue lesions can be visualized by US or MRI and may comprise bilateral thickening of the medial collateral ligament, flexor-pronator tendon, triceps tendon, and ulnar nerve [100].

Valgus extension overload is a spectrum of symptoms that are commonly seen in competitive overhead athletes [105]. Large valgus and extension forces in the acceleration phase of throwing lead to major tensile stress on medial structures, compressive forces on the lateral structures (see Sect. 4.2.2), and shear forces posteriorly (see Sect. 4.2.4). These chronic tensile forces lead to inflammation, microtearing, and laxity of the ligament, which may progress into disruption of the UCL. Less commonly, the UCL may be injured after traumatic elbow dislocation [105].

Plain radiographs may not provide any direct information on ligamentous injuries, but can be indirectly supportive if focal calcifications of the UCL are present [106, 107]. When compared to the normal appearance of the UCL on US, UCL sprains show thickening, decreased echogenicity, and hyperechoic areas demonstrating local calcifications [31, 107]. A completely ruptured UCL appears as a hypoechoic band surrounded by fluid.

On normal axial MR images, the anterior band of the UCL has uniform low signal intensity on T1W and T2W images. However, a completely normal UCL on MRI in a competitive throwing athlete is rarely seen [108]. Adaptations in response to forces in throwing include thickening of the anterior band of the UCL and posteromedial subchondral sclerosis of the trochlea. Therefore, MRI ought to be used to differentiate between acute versus chronic injury and to observe the degree of remodeling of the chronic ligament deformity [109]. Ruptures, sprains, laxity, or other irregularities manifest as a discontinuity with hyperintense fluid filling the hiatus on both T1W and T2W images [14, 104]. Avulsion fracture of the medial epicondyle may be present.

MR arthrography may be of particular benefit when partial-thickness tearing is suspected, since it improves the sensitivity of detecting such tears [18]. In case of a partial-thickness tear, the so-called T-sign may demonstrate increased signal intensity at the distal insertion near the sublime tubercle [14, 110].

Dislocation of the elbow is the most common dislocation in children and the second most common dislocation in adults (after dislocation of the shoulder) [111]. The elbow owes its stability to the osseous architecture of the ulnohumeral joint, which provides the most stability in the anteroposterior direction. The surrounding capsuloligamentous and musculotendinous aspects (including the collateral ligaments, joint capsule, and adjacent muscles) provide further stability. If these components are disrupted by trauma, elbow dislocation may result.

Dislocations of the elbow can either be simple or complex depending on the absence or presence of associated bony injury, respectively. Simple dislocations are described by the direction of the dislocated ulna relative to the humerus. Posterior displacement occurs in over 90 % of cases, with posterolateral dislocation as its most common subtype [112]. The injury mechanism is considered to be a combination of axial compression, supination, and valgus stress, often seen in FOOSH-type injuries [103]. Lateral and anterior displacements are rare and may result from a direct posterior blow to a flexed elbow [113]. Bony injuries of the olecranon and avulsion of the medial and lateral condyles and epicondyles can be present. Complex dislocations with combined fractures of the radial head or neck and the coronoid process are referred to as the terrible triad (see Sect. 4.2.1) [57, 102].

Accompanying ligamentous and capsular disruption can be described according to the Horii circle [103]. Stage 1 involves disruption of the LUCL with posterolateral rotatory subluxation of the ulna. In stage 2, the coronoid places on the trochlea (i.e., incomplete dislocation) and the other adjacent lateral ligaments are torn, including anterior and posterior aspects of the joint capsule. Finally in stage 3, the elbow is completely dislocated with the coronoid located posteriorly to the humerus. The MCL may be disrupted only posteriorly (stage 3A) or completely (stage 3B). Thus, elbow dislocation is the result of a posterolateral rotatory subluxation followed by a total disruption of the surrounding soft tissue from the lateral to the medial side [102].

Posterolateral dislocation can lead to permanent valgus instability that correlates with a worse overall clinical and radiographic result. All treatment options are therefore primarily aimed at restoring functional elbow stability [102]. Simple dislocations may be treated nonoperatively after reduction under adequate muscular relaxation and appropriate analgesia. To prevent joint contractures, definitive management involves limited mobilization and early active range of motion [114]. Complex fracture-dislocations require operative management with fixation of fractures and repair of damaged surrounding soft tissues. Damage to the brachial artery or median and ulnar nerve must be ruled out, although neurovascular injury is uncommon in the setting of a FOOSH injury [103].

Anteroposterior, lateral, and oblique radiographs should be obtained to determine the direction of the dislocation and the potential presence of associated fractures. An intact radiocapitellar line should be evident on all views, since this is no longer aligned in posterior elbow dislocations [8]. Post-reduction radiographs are required to ensure correct positioning of the elbow.

Concerning preoperative planning after complex elbow dislocation, CT can be used to delineate fractures, and MR imaging is helpful to visualize the extent of the soft tissue disruption [57, 115, 116].

Elbow dislocation from a FOOSH trauma poses a substantial risk for recurrent elbow instability, since the stabilizing architecture of the surrounding ligaments, the radial head, and the coronoid process can be significantly disrupted. This condition has also been reported following coronoid insufficiency, radial head excision, or steroid injections for lateral epicondylitis [18].

Several criteria are used to classify the degree of the instability: the articulation(s) involved, the direction of the displacement (valgus, varus, anterior or posterolateral), the degree of displacement (subluxation or dislocation), the timing of displacement (acute, chronic or recurrent), and the presence or absence of associated fractures [103]. The most common type of chronic elbow instability is posterolateral rotatory instability (PLRI) [117]. PLRI implies a dislocation by which external rotation of the radius and the ulna relative to the distal humerus results in posterior displacement of the radial head relative to the capitellum. Contrary to isolated dislocation of the radial head, the radioulnar joint does not dislocate because the annular ligament is not affected [118].

The lateral ligament complex limits external rotation of the radius and ulna relative to the humerus and is therefore considered the weakest link in the pathogenesis of PLRI [102]. However, the medial collateral ligament may contribute as well [119, 120].

The diagnosis is made clinically based on the patient’s history and physical examination. Patients with PLRI often have a history of ulnohumeral dislocation; recurrent symptoms of lateral pain, locking, clicking, snapping, or popping can be present. The feeling of instability mostly occurs when the elbow is actively brought from flexion into extension with the forearm in supination. Several specific apprehension tests are available to provoke these symptoms [118, 121]. During the lateral pivot-shift maneuver, the elbow is in supine position and mild valgus stress is applied while the elbow is flexed. The test is positive if apprehension or frank subluxation of the radius and the ulna (rotating away from the humerus) occurs [122]. The posterolateral rotatory drawer test involves overhead placement of the elbow in 40° of flexion. Subsequent application of an anteroposterior force on the ulna and the radius (with the forearm in external rotation) will subluxate the forearm away from the humerus on the lateral side, pivoting on the intact medial ligaments [122]. A more adequate evaluation of instability by these tests may be performed with the patient under anesthesia. The radial head then visibly subluxates posteriorly, whereas apprehension occurs when the patient is awake.

The primary treatment goal in patients with PLRI is to restore elbow stability. Nonoperative measures are applied in the first days after reduction. These measures include both splinting of the arm as well as rehabilitation to strengthen the surrounding musculature [123]. If unsatisfactory results are yielded by conservative management, surgical treatment may be considered. The majority of surgically treated patients encounter satisfactory outcomes regarding elbow stability [118]. Surgical management aimed at the reconstruction of ligaments can be performed either open or arthroscopically [123]. Deficiency of the radial head or coronoid may require bony reconstructions. In that case, computed tomography is of particular use to delineate complex fracture patterns and to assist in surgical planning [115].

Plain radiographs are used to demonstrate changes in the alignment of the elbow by reviewing the integrity of the radial head, coronoid process, and capitellum. The drop sign, indicative for PRLI, represents ulnohumeral separation on lateral radiographs [124]. Posterior displacement of the radial head in relation to the capitellum may be visible as well.

Although MRI has been well established as an effective method for the assessment of ligamentous injury to the LCL, the role of MRI in the diagnosis of PLRI remains questionable [121, 125]. However, examination through MR arthrography is advantageous if uncertainty about the diagnosis remains even though PLRI is suspected [123]. Arthrography reveals laxity of the LCL, widening of the lateral joint space, and osteochondral lesions at the radiocapitellar joint [18, 118].

The ulna and the radius act as a single functional unit through binding via the interosseous membrane and ligaments in the forearm. As a consequence, hyper-pronation injury with fracture of the ulna is often accompanied by a dislocation of the proximal radioulnar joint. This combination of injuries was first described by Monteggia in 1814 and further classified by Bado [126]. Depending on the location of displacement of the radial head, four types can be distinguished (see Table 4.7).

Since the long-term range of motion of the elbow is seriously threatened in Monteggia injury, early recognition is important [127]. Pediatric patients may sustain injuries slightly different to Monteggia injury, including plastic deformation, incomplete or greenstick fractures, and ulnar metaphyseal fractures [127]. Although conservative management can be successful in the younger population, operative treatment is warranted for the majority of adults [127, 128]. The treatment goal is to restore the cooperative functioning of the radius, ulna, and their associated articulations.

Radiographic examination should comprise AP, lateral, and oblique views of both the forearm and the wrist. The distal forearm should be evaluated for displacement of the ulna relative to the radius. The radiocapitellar line must accurately be assessed in the proximal forearm, since it may seem normal due to concurrent displacement of the ulnar shaft [5].

Isolated dislocation of the proximal radius, also termed nursemaid’s elbow or pulled elbow, is the result of a sudden pull on the arm. This longitudinal traction force with the forearm in pronation and extension pulls the radial head trough the annular ligament. Due to relative laxity of the annular ligament, this injury is common in children aged 0–5 years [129]. After the age of 5 years, the annular ligament is stronger and less likely to tear or be displaced. Generally, the diagnosis is based on the clinical presentation. The injured child is likely to not use the affected arm and holds it in pronation, mild flexion, and abduction against the body. Radiography (AP view) should be considered if the diagnosis is equivocal, if the mechanism of injury other than a pull is suspected, or if reduction attempts are unsuccessful [130].