FIGURE 18-1 Anteroposterior view of the elbow illustrates the bone and ligamentous structures which contribute to elbow stability. (A, lateral collateral ligament; B, annular ligament; C, medial collateral ligament.)

Lateral ligamentous constraints include the annular ligament that is attached to proximal ulna and encircles the radial neck and the lateral collateral ligaments that originate from the lateral epicondyle and insert into the annular ligament and the lateral aspect of the proximal ulna. The primary role of the annular ligament and the lateral collateral ligament complex is to provide stability to the radiocapitellar and proximal radioulnar joints by resisting varus stress.

The medial ulnar collateral ligament is the primary ligamentous restraint to valgus stress, resisting pathologic opening of the medial aspect of the elbow. Having its origin from the inferior aspect of the medial epicondyle, the medial collateral ligament has two primary components that contribute to elbow stability, the anterior and the posterior bands. The band’s anterior portion is taut in extension and the posterior fibers are taut in flexion (Fig. 18-4). There is also a fan-shaped posterior oblique ligament that inserts on the olecranon and functions mainly in flexion and a small transverse ligament runs from the olecranon to the coronoid that is thought to have little functional importance. Woods and Tullos¹⁹¹ pointed out that the major stabilizing ligamentous structure in the elbow is the anterior band of the ulnar collateral ligament.

The medial epicondyle represents a traction apophysis because the forces across its physis are in tension rather than the compressive forces present across the other condylar physes of the distal humerus. The medial epicondylar apophysis actually arises from the posterior surface of the medial distal humeral metaphysis. Ossification begins at about 4 to 6 years of age and fuses at about 15 years of age, making it the last secondary ossification center to fuse with the distal humeral metaphysis. The ossification center starts as a small eccentric oval nucleus (Fig. 18-5A). As it matures, parallel sclerotic margins develop along both sides of the physis (Fig. 18-5B). There may be some irregularity of the ossification process, which gives the ossific nucleus a fragmented appearance. This fragmentation may be falsely interpreted as a fracture.

Superficially the flexor–pronator mass, which includes the origin of the flexor carpi radialis, flexor carpi ulnaris, flexor digitorum superficialis, palmaris longus, and part of the pronator teres, originates from the anterior aspect of the medial epicondylar apophysis (Fig. 18-6).¹⁶⁰ Part of the flexor carpi ulnaris also originates on the posterior aspect of the epicondyle. Deep to these muscular insertions, the medial ulnar collateral ligament originates from the medial epicondyle. In younger children, some of the capsule’s origin extends up to the physeal line of the epicondyle. In older children and adolescents, as the epicondyle migrates more proximally, the capsule is attached only to the medial crista of the trochlea.¹² Thus, in older children, if there is a pure muscular avulsion force on the epicondyle, the capsule and part of the medial ligamentous complex may remain attached to the trochlea’s outer border and relative elbow stability preserved. However if the medial epicondyle is avulsed via the medial ulnar collateral ligament, given the importance of this ligament in elbow stability, relative elbow instability usually results.

In general, flexion and supination are usually regarded as positions of stability, whereas extension and pronation are positions of relative instability (Fig. 18-7).

CLASSIFICATION OF ELBOW DISLOCATIONS AND MEDIAL EPICONDYLE FRACTURES

Elbow dislocations are described by the position of the proximal radioulnar joint relative to the distal humerus: Posterior, anterior, medial, or lateral. Posterior dislocations are typically further subdivided into posterolateral and posteromedial injuries. Occasionally, the proximal radioulnar joint is disrupted. When this happens, the radius and ulna can diverge from each other. Rarely, the radius and ulna translocate, with the radius medial and the ulna lateral. Isolated dislocations of the radial head must be differentiated from congenital dislocations. Isolated dislocations of the proximal ulna are exceedingly rare and have not been reported in children. Included in this chapter is a discussion of the commonly occurring subluxation of the radial head, or “nursemaid’s elbow.” This is not a true subluxation but rather a partial entrapment of the annular ligament in the radiocapitellar joint. Monteggia fracture dislocations are discussed in detail in Chapter 14.

POSTERIOR ELBOW DISLOCATIONS

ASSESSMENT OF POSTERIOR ELBOW DISLOCATIONS

Mechanisms of Injury for Posterior Elbow Dislocations

O’Driscoll et al.¹²⁵ have proposed that most posterior elbow dislocations begin with disruption of the lateral ligaments and proceed along the anterior capsular structures to the medial ligaments. Although this is likely the mechanism for the more rarely seen posteromedial elbow dislocation, for the more common posterior and posterolateral elbow dislocations, this notion has been challenged. Clinical and magnetic resonance imaging (MRI)-based studies noting that medial ulnar collateral ligament injuries occur more frequently than lateral ulnar collateral injuries,^76,77,79,144 have led to the competing theory¹⁴⁴ that most posterior elbow dislocations initiate from a valgus force at the elbow leading to failure of the medial ulnar collateral ligament or the medial epicondyle apophysis, to which it is attached, creating a medial epicondyle fracture. As the proximal radius and ulna displace laterally, the coronoid disengages with the intact biceps tendon acting as the center of rotation for the displaced forearm (Fig. 18-8). Application of both an abduction and an extension force leads to forearm external rotation and, with anterior soft tissue disruption, the result is a posterior or posterolateral elbow dislocation.^125,144

Associated Injuries with Posterior Elbow Dislocations

Fractures Associated with Posterior Elbow Dislocations

Concomitant fractures occur in over one-half of posterior elbow dislocations.^{90,121,147,150} The most common fractures involve the medial epicondyle, the coronoid process, and the radial head and the neck. Fractures involving the lateral epicondyle, lateral condyle, olecranon, capitellum, and trochlea occur less frequently.²⁵ Given the significant association between fractures of the medial epicondyle, the coronoid process and the proximal radius (especially markedly displaced radial neck fractures), and posterior elbow dislocations, evaluating for elbow stability when these fractures are noted is important.

Soft Tissue Injuries Associated with Posterior Elbow Dislocations

Posterior dislocations normally produce moderate soft tissue injury and can be associated with neurovascular injuries in addition to concomitant fractures (Fig. 18-9). The anterior capsule fails in tension, opening the joint cavity. Radial head displacement strips the capsule from the posterolateral aspect of the lateral condyle with the adjacent periosteum. Because of the large amount of cartilage on the posterolateral aspect of the lateral condyle, the posterior capsule may not reattach firmly with healing. This lack of a strong reattachment is believed to be a factor in the rare recurrent elbow dislocation.¹²⁶ In a series of 62 adults and adolescents with elbow dislocations requiring surgical treatment, McKee et al.¹¹¹ reported that disruption of the lateral collateral ligament complex occurred in all 62 elbows.

Medially, the ulnar collateral ligament complex is disrupted either by an avulsion of the medial epicondyle or a direct tear of the ligament.^157,165 Cromack³⁰ found that with medial epicondylar fractures, the origins of the ulnar collateral ligaments and the medial forearm flexor muscles remain as a unit, along with most of the pronator teres, which is stripped from its humeral origin proximal to the epicondyle. These structures are then displaced posterior to the medial aspect of the distal humerus. The ulnar collateral ligaments and the muscular origins of the common flexor muscles tear if the epicondyle remains attached to the humerus. With posterolateral displacement of the forearm, the medial aspect of the distal humerus most often passes into the intermuscular space between the pronator teres posteriorly and the brachialis anteriorly. The brachialis, because it has little distal tendon, is easily ruptured. The rent in the anterior capsule usually is in this same area.

The structure most commonly torn on the lateral aspect of the elbow is the annular ligament.¹⁶⁵ On occasion, the lateral collateral ligament either avulses a small osteochondral fragment from the lateral epicondyle or tears completely within its substance.

Neurovascular Injuries Associated with Posterior Elbow Dislocations

When the elbow is dislocated, the medial aspect of the distal humerus typically protrudes between the pronator teres posteriorly and the brachialis anteriorly. The median nerve and brachial artery lie directly over the distal humerus in the subcutaneous tissues. In a cadaver and clinical study by Louis et al.,⁹⁴ there was a consistent pattern of disruption of the anastomosis between the inferior ulnar collateral artery and the anterior ulnar recurrent artery. If the main brachial arterial trunk also is compromised, the loss of this collateral system can result in the loss of circulation to the forearm and hand.

The ulnar nerve is at risk in posterior elbow dislocation because of its position posterior to the medial epicondyle. In clinical cases, the ulnar nerve is the most common neurovascular injury.

Signs and Symptoms of Posterior Elbow Dislocations

Posterior elbow dislocations must be differentiated from extension-type supracondylar fractures of the distal humerus. With both injuries, the elbow is held semiflexed and swelling may be considerable. Swelling initially is usually less with a dislocation than with a type III supracondylar humeral fracture. Crepitus is usually absent in children with a dislocation and the forearm appears shortened. The prominence produced by the distal humeral articular surface is more distal and is palpable as a blunt articular surface. The tip of the olecranon is displaced posteriorly and proximally so that its triangular relationship with the epicondyles is lost. The skin may have a dimpled appearance over the olecranon fossa. If the dislocation is posterolateral, the radial head also may be prominent and easily palpable in the subcutaneous tissues.

Imaging and Other Diagnostic Studies for Posterior Elbow Dislocations

Anteroposterior (AP) and lateral x-rays usually are diagnostic of a posterior elbow dislocation. There is a greater superimposition of the distal humerus on the proximal radius and ulna in the AP view. The radial head may be proximally and laterally displaced, or it may be directly behind the middistal humerus, depending on whether the dislocation is posterolateral, posterior, or posteromedial (Fig. 18-10). The normal valgus angulation between the forearm and the arm usually is increased. On the lateral view, the coronoid process lies posterior to the condyles. Prereduction and postreduction x-rays must be examined closely for associated fractures. The medial epicondyle should be identified on the postreduction films. If it should be present based on the patient’s age and elbow ossification pattern and it is not visible, the medial epicondyle is likely fractured and may be entrapped in the joint. Additional radiographs may be necessary to further evaluate an associated medial epicondyle fracture. Postreduction radiographs should be carefully scrutinized for a congruent reduction and for subtle osteochondral fracture fragments that can become entrapped in the joint (Fig. 18-11). If anatomic, congruent reduction is in question or not feasible or if osteochondral fragments are visualized, further evaluation with computerized tomography or MRI is utilized. MRI may be used to further define the extent of soft tissue injury in complex injury patterns.

TREATMENT OPTIONS FOR POSTERIOR ELBOW DISLOCATIONS

If untreated, elbow dislocation predictably results in dramatic loss of elbow function characterized by loss of motion and eventually pain (Fig. 18-12). In comparison, reduction of the dislocated elbow usually achieves marked improvement of acute pain as well as restoration of long-term function.

Nonoperative Treatment of Posterior Elbow Dislocations

Indications/Contraindications

Progressive elbow swelling secondary to the soft tissue injury associated with an elbow dislocation makes it imperative that all acute elbow dislocations be promptly reduced under adequate sedation or anesthesia. Royle¹⁵⁰ found that dislocations reduced soon after the injury had better outcomes than those in which reduction was delayed. Immediately after reduction, the surgeon should determine and document the stability of the elbow by examination under anesthesia or sedation. Definitive nonoperative treatment following closed reduction can be considered if the elbow is stable through a functional range of motion, a concentric anatomic reduction can be obtained and maintained, and there is no evidence to suggest a vascular injury, nerve entrapment, or significant intra-articular osteochondral fragments (Table 18-1).

Techniques for Closed Reduction of Posterior Elbow Dislocations

All methods of closed reduction must overcome the deforming muscle forces so that the coronoid process and the radial head can slip past the distal end of the humerus. Adequate sedation or anesthesia is necessary to permit muscle relaxation. Before the primary reduction forces are applied, the forearm is hypersupinated to dislodge the coronoid process and radial head from their position behind the distal humerus and to reduce tension on the biceps tendon.¹²⁶ The reducing forces are applied in two major directions (Fig. 18-13). The first reducing force must be along the long axis of the humerus to overcome the contractions of the biceps and brachialis anteriorly and the triceps posteriorly. Once these forces are neutralized, the proximal ulna and radius must be passed from posterior to anterior. Combined pusher–puller techniques are also possible.^59,183

Previous authors^90,183 have strongly advised against initial hyperextension before reduction forces are applied to the elbow. Loomis⁹¹ demonstrated that when the coronoid process is locked against the posterior aspect of the humerus and the elbow is extended, the force applied to the anterior muscles is multiplied by as much as five times because of the increased leverage. This places a marked strain on the injured structures in the antecubital fossa including the anterior capsule, the brachialis muscle, and the neurovascular structures (Fig. 18-14). By contrast, when force is applied to the proximal forearm with the elbow flexed, the force exerted against the muscles across the elbow is equal to the distracting force. For patients with posterolateral dislocations, the lateral displacement of the proximal radius and ulna must first be corrected to prevent the median nerve from being entrapped or injured during reduction.^18,22 Hyperextension reduction puts the median nerve more at risk for entrapment.

Closed Reduction of a Posterior Elbow Dislocation by the “Puller” Technique

The puller technique can be performed in various positions including the supine position and the prone position.

Prereduction Planning. If adequate sedation to achieve full muscular relaxation cannot be achieved in the emergency department, the procedure should be performed in the operating room under general anesthesia. An assistant who can provide adequate stabilizing force is required. Use of fluoroscopy is not usually required to assess the reduction. However, if available, it can help assess elbow stability and provide a more dynamic assessment of reduction congruity that postreduction plain radiographs, especially those obtained following placement of immobilization, cannot provide (Table 18-2).

Positioning. The patient is placed on the table either in the supine or the prone position with the shoulder abducted 90 degrees and the elbow off the side of the table. An assistant is positioned on the opposite side of the patient to provide the counterforce. A sheet can be placed around the patient for stabilization purposes if desired. If this is done an additional assistant may be required to stabilize the upper arm during the reduction.

Technique. With the elbow flexed to almost 90 degrees, a traction force is applied to the anterior portion of the forearm along the longitudinal axis of the humerus with one hand while the other hand pulls distally along the forearm. If any medial or lateral displacement is present, this should be corrected before the forearm is translated distally to release soft tissue structures from the distal humerus and prevent entrapment of tissue around the distal humerus. Gently “milking” the anterior soft tissue out from around the distal humerus, by gently pinching and pulling the tissues enveloping the distal humerus forward, as the reduction is performed can also help the reduction. During the procedure, a counterforce is applied by an assistant to offset the manipulating forces and stabilize the humerus. The physician performing the procedure usually appreciates a palpable clunk of the reduction. Using fluoroscopic evaluation, if available, the reduction is assessed in multiple projections. The range of stable motion is assessed, noting stability with the forearm in full supination and in neutral rotation (Table 18-3).

Closed Reduction of a Posterior Elbow Dislocation by the “Pusher” Technique

Like the puller technique, the pusher technique can be performed in various positions.

Prereduction Planning. Again, like the pusher technique, adequate sedation is required and fluoroscopy can be helpful for postreduction evaluation (Table 18-4).

Positioning. The patient is positioned with the distal humerus over a fixed surface, either the back of a chair or the edge of the bed.

Technique. With the elbow flexed to almost 90 degrees, the thumb is used to push the olecranon distally past the humerus. The other arm then pulls distally along the axis of the forearm affecting the reduction. Again, if any medial or lateral displacement is present, this should be corrected before the forearm is translated distally. Fluoroscopic evaluation, if available, can then be performed as with the puller technique. Elbow stability should be assessed and the elbow then immobilized in a position of stability (Table 18-5).

Postreduction Care Following Closed Reduction of a Posterior Elbow Dislocation

Some type of immobilization, usually a posterior splint, is advocated by most investigators. A frequently recommended period of immobilization is 3 weeks,^{90,91,130,158} although some have advocated early motion.^149,150,191 In a recent study of 42 adult patients comparing 2 weeks of cast immobilization with the use of a simple arm sling and early motion, Maripuri et al.¹⁰⁶ demonstrated improved early and final functional outcomes in the early mobilization group compared to the group placed in a cast following reduction. O’Driscoll et al.¹²⁵ suggested that if the elbow was stable in response to valgus stress with the forearm pronated then the anterior portion of the medial collateral ligament was intact and the patient could begin early motion. Ninety degrees of elbow flexion appears to be the standard position of immobilization. Hinged elbow braces with adjustable blocks to motion are very useful for obtaining progressive, protected motion.

Posterior Elbow Dislocation Outcomes

Closed reduction of posterior elbow dislocations is successful in most cases. In the combined series of 317 dislocations,^{90,121,147,150} only two cases⁹⁰ could not be reduced by closed methods. In the Carlioz and Abols²⁵ series, two dislocations reduced spontaneously and closed reduction was successful in 50 cases, but failed in six cases (10%). Josefsson et al.⁷⁸ reported that all 25 dislocations without associated fractures were successfully reduced.

Operative Treatment of Posterior Elbow Dislocations

Indications/Contraindications

Indications for primary open reduction include an inability to obtain or maintain a concentric closed reduction, an open dislocation, a displaced osteochondral fracture with entrapment in the joint, a vascular injury, or a neurologic injury for which there is any indication that there may be entrapment of the nerve.

Primary ligament repair is not routinely indicated. Adults with posterior elbow dislocations without concomitant fracture have no better function or stability following a primary ligamentous repair than those treated nonoperatively.^76,77 All fractures preventing concentric reduction need to be repaired with an open reduction of an elbow dislocation. Beware of elbow dislocations in children less than age 10 as they often have associated osteochondral fractures blocking reduction or preventing stability postreduction (Table 18-6).

Open Posterior Elbow Dislocations. Open dislocations have a high incidence of associated arterial injury.^63,82,90,94 Operative intervention is necessary in open posterior dislocations to irrigate and debride the open wound and elbow and to evaluate the brachial artery. If there is vascular disruption, most advocate vascular repair or reconstruction with a vein graft even in the presence of adequate capillary refill. This may lessen the risk of late cold intolerance, dysesthesias, or dysvascularity.

Fractures Associated with Posterior Elbow Dislocations. Children with an elbow dislocation can have an associated fracture of the coronoid, lateral condyle, olecranon (Fig. 18-15), radial neck, or medial epicondyle (Fig. 18-16). Fractures of the anteromedial facet of the coronoid have been recognized as an important injury associated with elbow dislocations in adolescents and adults.^35,36 The presence of a concomitant displaced fracture is a common indication for surgical intervention.^25,46,185 Surgery for associated fractures produced better results than nonoperative treatment in the series of Carlioz and Abols,²⁵ and similar results were reported by Wheeler and Linscheid.¹⁸⁵ Repair of an associated medial epicondylar fracture may also improve elbow stability in throwing athletes when the injury is in the dominant arm.^157,191 Entrapment of any fracture fragments within the joint is an absolute indication for surgical treatment. Displaced medial epicondyle fractures can be entrapped within the joint after reduction and are often overlooked on the radiographs (Fig. 18-20). Because of the high association of this fracture with elbow dislocations, the location of the medial epicondyle should be confirmed in every case. Ultimately, the surgical treatment for fractures associated with an elbow dislocation is based on the circumstances surrounding each individual patient. Factors favoring operative treatment include older patient age, instability of the elbow during examination under sedation at the time of reduction, the presence of a displaced intra-articular fracture, injury to multiple elbow stabilizers, injury to the patient’s dominant arm, and anticipated high-demand sports, especially overhead sports, or activities on the elbow.

Vascular Injuries Associated with Posterior Elbow Dislocations. With initial evidence of vascular compromise, treatment should consist of urgent reduction of the elbow dislocation which usually returns the displaced brachial vessels to their normal position^64,187 followed by reassessment of the vascular status. With prompt normalization of the vascular status, serial observation is still recommended to evaluate for evolving circulatory compromise. If there is evidence of persistent vascular compromise after reduction, vascular exploration followed by operative repair of those structures that are ruptured or severely damaged should be pursued emergently. Even though collateral vessels may provide adequate vascular flow to give a warm hand with good capillary refill, if there has been a significant vascular injury, failure to repair the injury may predispose the patient to late ischemic changes such as claudication, cold sensitivity, or even late amputation.

Neurologic Injuries Associated with Posterior Elbow Dislocations. As with vascular injuries, initial evidence of neurologic compromise should prompt urgent reduction. A significant negative change in the neurologic status following closed reduction may indicate nerve entrapment and should prompt exploration.

Open Reduction of an Irreducible Posterior Elbow Reduction

Preoperative Planning. The surgical approach will be dictated by the goals of the procedure and based on an estimation of the structures that may be blocking the reduction. The most common structures preventing reduction via closed means include the distal humerus being buttonholed through the brachialis musculature, the radial head being buttonholed through the capsule and lateral collateral ligament, and entrapment of fracture fragments, especially the medial epicondyle, with their attached ligamentous or muscular structures wedging them in place. If the distal humerus or the radial head is easily palpable in the subcutaneous tissues and not able to be milked out of these tissues through closed means, an operative approach to perform this will be necessary. For the distal humerus in the brachialis a medial approach should be performed. For the radial head block, a lateral approach has been described.^55,84 If a fracture fragment, especially the medial epicondyle, can be visualized and is thought to be responsible for the block, the medial approach should be employed to facilitate fracture fixation (Table 18-7). Loose osteochondral fracture fragments can block a congruent reduction and computed tomography (CT) and/or MRI scanning may be required to visualize the fragments and determine operative approach.

Positioning. Supine positioning with a hand table will usually suffice. With an associated medial epicondyle fracture, the lateral position or the prone position may be employed as well. (See the section on medial epicondyle fractures.)

Technique for Open Reduction. For a medial approach, an incision is made just anterior to the predicted mid humeral line and curved distally just anterior the medial epicondyle. With gentle spreading of the subcutaneous tissues the significant soft tissue trauma is evident. The buttonholed distal humerus, the median and ulnar nerves, and the brachial artery should be identified. Any intervening tissue or osteochondral fragments are removed from the interval between the joint surfaces. The joint is then reduced through a similar set of distraction and translational forces as described for the closed reduction techniques. Once reduced, joint stability is evaluated and a thorough assessment of the capsular and ligamentous structures is performed. Primary repair or reattachment of the medial collateral ligament complex with small suture anchors or transosseous drill holes may be performed to improve stability. The elbow is stabilized in a posterior splint or hinged elbow brace in a position of stability (Table 18-8).

Postoperative Care

Immobilization after surgery depends on the procedure performed. After open reduction, management is similar to that after satisfactory closed reduction. The length of immobilization for fractures is 5 to 10 days up to 3 to 4 weeks. Protected arc of motion with a hinged brace or intermittent splinting is utilized frequently to lessen the risk of posttraumatic contracture.

AUTHOR’S PREFERRED METHOD OF TREATMENT FOR POSTERIOR ELBOW DISLOCATIONS (FIG. 18-17)

MANAGEMENT OF EXPECTED ADVERSE OUTCOMES AND UNEXPECTED COMPLICATIONS RELATED TO POSTERIOR ELBOW DISLOCATIONS

Complications associated with posterior elbow dislocations can be divided into those occurring early and those occurring later. Early complications include neurologic and vascular injuries. Late complications include loss of motion, myositis ossificans, recurrent dislocations, radioulnar synostosis, and cubitus recurvatum. The special problems of chronic, unreduced dislocations are not considered complications of treatment (Table 18-10).

Associated Neurologic Injuries with Posterior Elbow Dislocations

Ulnar Nerve Lesions

In a combined series of 317 patients,^{90,121,147,150} the most commonly injured nerve was the ulnar nerve. Of the 32 patients (10%) who had nerve symptoms after reduction, 21 had isolated ulnar nerve injuries, seven had isolated median nerve injuries, and in four patients both the median and ulnar nerves were involved. Linscheid and Wheeler⁹⁰ recommended ulnar nerve transposition if ulnar nerve symptoms were present in a patient undergoing open reduction and internal fixation of a displaced medial epicondylar fracture. Except for the one patient described by Linscheid and Wheeler,⁹⁰ the reported ulnar nerve injuries were transient and resolved completely.

Radial Nerve Lesions

Radial nerve injury with posterior elbow dislocation is very rare. Watson-Jones¹⁸³ reported two radial nerve injuries associated with elbow dislocation; in both the symptoms rapidly resolved after reduction. Rasool¹⁴² reported a third case.

Median Nerve Lesions

The most serious neurologic injury involves the median nerve, which can be damaged directly by the dislocation or can be entrapped within the joint. Median nerve injuries occur most commonly in children 5 to 12 years of age. These injuries, either isolated median nerve (7 out of 317 total dislocations) or combined median and ulnar nerve injuries (4 out of 317 total dislocations), were present in only 3% of dislocations.^{90,121,147,150}

Types of Median Nerve Entrapment. Fourrier et al.,⁴³ in 1977, delineated three types of medial nerve entrapment (Fig. 18-21).

Type 1. The child has an avulsion fracture of the medial epicondyle or has a rupture of the flexor–pronator muscle origin and the ulnar collateral ligament (Fig. 18-21A). This allows the median nerve, with or without the brachial artery, to displace posteriorly, essentially wrapping posteriorly around the medial aspect of the humerus and then coursing distally around the articular surface of the distal humerus. With the deep groove of the trochlea acting like a hook for the nerve and catching it out of the anterior soft tissues, if the lateral displacement of the proximal radius and ulna is not corrected before reduction, the nerve may become entrapped in the joint, wrapped around the distal humerus alongside or even in the ulnotrochlear articulation during the process of reduction. Hallett⁵⁸ demonstrated in cadavers that pronation of the forearm while the elbow is hyperextended forces the median nerve posteriorly during the process of reduction making it vulnerable to entrapment. This type of entrapment also has been reported by other authors.^{13,18,22,43,54,138,141,169} If median nerve dysfunction is present prior to reduction, it is often difficult to identify nerve entrapment postreduction. Certainly any significant decrease in median nerve function following a closed reduction or incongruity in the reduction should prompt evaluation for this injury pattern. In some patients with an associated medial epicondyle fracture, the nerve can be so severely damaged after being entrapped that neuroma resection, nerve transposition, and direct repair or grafting is necessary.^18,54 Good recovery of nerve function has been reported after operative decompression and repair.

If the nerve has been entrapped for a considerable period, the Matev sign may be present on the x-rays. This represents a depression on the posterior surface of the medial epicondylar ridge where the nerve has been pressed against the bone.^{13,31,54,58,138,141,169} This groove is seen on x-ray as two sclerotic lines parallel to the nerve (Fig. 18-22). This sign disappears when the nerve has been decompressed.

Type 2. The nerve is entrapped between the fracture surfaces of the medial epicondyle and the distal humerus (Fig. 18-21B). The fracture heals and the nerve is surrounded by bone, forming a neuroforamen.^138,145,169 This may or may not be visible on x-ray. The medial epicondyle is osteomized to free the nerve. Again, decompression alone may be an adequate treatment, although neuroma resection and repair or reconstruction with nerve grafts may be necessary.

Type 3. The nerve is kinked and entrapped between the distal humerus and the olecranon (Fig. 18-21C). Only three injuries of this type have been reported.^13,137,140 Decompression, neuroma resection, and repair resulted in return of good function over 6 to 24 months.

Al-Qattan et al.⁶ described a fourth type of median nerve entrapment in a 14-year-old boy who had a posterior elbow dislocation with a medial epicondylar fracture. The median nerve was found entrapped in a healed medial epicondylar fracture (type 2) in an anterior to posterior direction 18 months after injury. The nerve then passed through the elbow joint in a posterior to anterior direction (type 1). The nerve was so severely damaged that it had to be resected and repaired with sural nerve grafts. A second type 4 median nerve entrapment also requiring nerve segment resection and grafting was reported by Ozkoc et al.¹²⁷

The combination of an associated fracture of the medial epicondyle and significant median nerve dysfunction was cited by Rao and Crawford¹⁴¹ as an absolute indication for surgical exploration of the nerve because of the frequency of median nerve entrapment with fractures of the medial epicondyle. MRI may be helpful in defining the course of the median nerve if entrapment is suspected.³ Electromyography and nerve conduction studies have been utilized to assist in operative decision making. Painful dysesthesias with arc of motion is usually indicative of entrapment. Once the entrapped nerve is removed from the joint, neurologic function typically improves. Resection and repair or nerve grafting may be necessary.

Associated Arterial Injuries with Posterior Elbow Dislocations

Arterial injuries are uncommon with posterior elbow dislocations in children and adolescents with only eight vascular injuries (3%) reported in the combined series of 317 patients.^{90,121,147,150} However, Carlioz and Abols²⁵ reported four patients with diminished radial pulses that resolved after reduction. Arterial injuries have been associated with open dislocations in which collateral circulation is disrupted.^63,82,94,151 In these situations, usually the brachial artery is ruptured,^{57,63,68,82,94,151} but it can also be thrombosed¹⁸⁷ as well as entrapped in the elbow joint.^64,133,187 Pearce¹³³ reported an entrapped radial artery in which there was a high bifurcation of the brachial artery. When there is a complete rupture, there usually is evidence of ischemia distally. However, the presence of good capillary circulation to the hand or a Doppler pulse at the wrist does not always mean the artery is intact.^57,68 Arteriograms usually are not necessary because the arterial injury is at the site of the dislocation. If imaging is indicated to evaluate possible arterial injury, its minimal risk and invasiveness make vascular ultrasound an attractive initial imaging choice.

For surgical treatment of vascular injuries about the elbow, simple ligation of the ends has been done in the past with adults, especially if there was good capillary circulation distally.^63,82 However, this may predispose to late ischemic changes such as claudication, cold sensitivity, or even late amputation. Most investigators recommend direct arterial repair or a vein graft.^{57,68,94,102,151} Louis et al.⁹⁴ recommended arterial repair because their cadaver studies demonstrated that a posterior elbow dislocation usually disrupted the collateral circulation necessary to maintain distal blood flow.

Loss of Motion Associated with Posterior Elbow Dislocations

Almost all patients with elbow dislocations lose some range of elbow motion.^{25,46,76–78,} This loss is less in children than in adults⁷⁸ and usually is no more than 10 degrees of extension. This rarely is of functional or aesthetic significance. However, the potential for loss of motion must be explained to the parents before reduction and may be an indication for a supervised rehabilitation program. If there is a displaced medial epicondylar fracture, because of the loss of isometry in the medial ligaments, the loss of major range of motion can be severe and limiting. Similarly, an incongruent elbow joint will have marked limitations of motion. In situations where the loss of motion is greater than 45 to 60 degrees, late operative release may be indicated.

Myositis Ossificans Versus Heterotopic Calcification

True myositis ossificans should be differentiated from heterotopic calcification, which is a dystrophic process. Myositis ossificans involves ossification within the muscle sheath that can lead to a significant loss of range of motion of the elbow. Disruption of the brachialis muscle is believed to be a contributory factor.⁹¹ Fortunately, myositis ossificans is rare in children.^78,176 Although heterotopic calcification in the ligaments and capsule of the elbow is common,^78,147 it rarely results in loss of elbow function (Fig. 18-23).

In Neviaser and Wickstrom’s¹²¹ series of 115 patients, 10 had x-ray evidence of myositis ossificans; all, however, were asymptomatic. Roberts¹⁴⁷ differentiated true myositis ossificans from heterotopic calcification in his series of 60 elbow dislocations, and noted that only three patients had true myositis ossificans. Linscheid and Wheeler⁹⁰ reported that the incidence of some type of heterotopic calcification was 28%, which was most common around the condyles. Only in five patients was it anterior to the capsule (which probably represented true myositis ossificans in the brachialis muscle). Four of these patients had some decrease in elbow function. Josefsson et al.⁷⁸ reported that 61% of 28 children with posterior dislocations had periarticular calcification, but this did not appear to be functionally significant.

Radioulnar Synostosis

In dislocations with an associated fracture of the radial neck, the incidence of a secondary proximal radioulnar synostosis is increased (Fig. 18-24). This can occur regardless of whether the radial neck fracture is treated operatively or nonoperatively^22,25,125 and likely occurs because of the extensive periosteal stripping that occurs along the anterior aspect of the forearm between the proximal radius and ulna. Carlioz and Abols²⁵ reported a synostosis in one of three patients with posterior elbow dislocations associated with radial neck fractures.

Cubitus Recurvatum

Occasionally, a severe elbow dislocation results in significant tearing of the anterior capsule. As a result, after reduction, when all the stiffness created by the dislocation has subsided, the patient may have some hyperextension (cubitus recurvatum) of the elbow. This is usually minimally symptomatic but if asymmetric, may be aesthetically disturbing to the parents and adolescent.

Recurrent Posterior Dislocations

Recurrent posterior elbow dislocation is rare. In the combined series of dislocations, only 2 of 317 patients (0.6%) experienced recurrent dislocations.^{90,121,147,150} Approximately 80% of recurrent dislocations are in males. Three investigators have reported bilateral cases.^81,116,143 The pathology of recurrent dislocation involves any or all of a combination of collateral ligament instability, capsular laxity, and bone and articular cartilage defects.

Pathology Contributing to Recurrent Posterior Dislocations

Osborne and Cotterill¹²⁶ suggested that articular changes are secondary and that the primary defect is a failure of the posterolateral ligamentous and capsular structures to become reattached after reduction (Fig. 18-25). Osborne and Cotterill¹²⁶ proposed that the extensive articular cartilage covering the surface of the distal humerus leaves little surface area for soft tissue reattachment and the presence of synovial fluid further inhibits soft tissue healing. With recurrent dislocations, the radial head impinges against the posterolateral margin of the capitellum, creating an osteochondral defect (Fig. 18-26). In addition to the defect in the capitellar articular surface, a similar defect develops in the anterior articular margin of the radial head. When these two defects oppose each other, recurrence of the dislocation is more likely. Subsequent studies have confirmed these findings in almost all recurrent dislocations, especially in children.^{37,62,124,172,178,190}

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