Article

Orthopedic pitfalls in the ED: neurovascular injury associated with posterior elbow dislocations

Diagnostics

Orthopedic pitfalls in the ED: neuroVascular injury associated with posterior elbow dislocations

Sadie J. Carter MD a, Carl A. Germann MD b, Angelo A. Dacus MD c,

Timothy W. Sweeney MD a, Andrew D. Perron MD a,?

aDepartment of Emergency Medicine, Maine Medical Center, Portland, ME, USA

bObservational Medicine, Department of Emergency Medicine, Maine Medical Center, Portland, ME, USA

cDepartment of Orthopedic Surgery, University of Virginia Health System, Charlottesville, VA, USA

Received 19 May 2009; accepted 27 May 2009

Abstract Posterior elbow dislocations are the most common type of elbow dislocation and are usually caused by a fall on an outstretched hand. Although the incidence of elbow dislocation complications is rare, the emergency physician is responsible for evaluation and identification of concomitant neurovascular injuries. Failure to identify neurovascular compromise after elbow dislocation or reduction can potentially lead to severe morbidity with Limb ischemia, neurologic changes, compartment syndrome, and potential loss of limb. Cyanosis, pallor, pulselessness, and marked pain should suggest vascular injury or compartment syndrome, both requiring immediate intervention. Patients in whom it is not clear if there is vascular injury should undergo further imaging with angiography, considered the gold standard for evaluation of arterial damage. It is important for the emergency physician to maintain a high level of suspicion and evaluate for neurovascular compromise on every patient with elbow dislocation despite the low overall incidence of severe injury.

(C) 2010

Introduction

Posterior elbow dislocations are the most common type of elbow dislocation and are usually caused by a fall on an outstretched hand [1-3]. Although usually easily reduced with few complications or chronic disability, elbow disloca- tions can be limb-threatening emergencies, and therefore, appropriate evaluation and treatment in the emergency department (ED) are critical. One of the most important roles of the emergency physician with individuals presenting with elbow dislocations is the evaluation for concomitant neurovascular injuries. Failure to identify injuries with a thorough neurovascular examination both before and after

* Corresponding author. Tel.: +1 207 662 7015; fax: +1 207 662 7054.

E-mail address: [email protected] (A.D. Perron).

elbow dislocation reduction can potentially lead to severe morbidity with limb ischemia, neurologic changes, cold intolerance, compartment syndrome, and potential loss of limb. Therefore, it is important for the emergency physician to maintain a high level of suspicion and evaluate for neurovascular compromise on every patient with elbow dislocation despite the low incidence of severe injury.

The elbow is the second most commonly dislocated major joint after the shoulder in the adult population [4-6] and the most commonly dislocated major joint in the pediatric population [2,4]. This review will focus only on the adult population because pediatric complications have been reviewed previously [7]. Elbow dislocations constitute approximately 10% to 25% of all injuries to the elbow [1-3] among persons with a mean age of 30 years [2,8] and are slightly predominant in the male population [1,2,7]. The

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main mechanism of elbow dislocation is often a fall on an outstretched hand. motor vehicle accidents; sports such as gymnastics, wrestling, and football; and other high-energy mechanisms, such as fall from height, account for most dislocations [2,3]. The nondominant extremity has slight predominance for dislocation. This is felt to be most likely related to a protective instinct to shield the dominant arm from injury when an individual falls [2]. These injuries are most commonly closed, with open injuries occurring with higher energy mechanisms.

Because complications such as Neurovascular injury are rare, there is limited information regarding the rates and presentation. Nonetheless, missing a neurovascular injury has important consequences and, therefore, must be evaluated every time a patient presents with an elbow dislocation. It is important to rapidly identify any potential vascular injury; hard signs of vascular injury including cyanosis, pallor, pulselessness, expanding hematoma, and marked pain should immediately suggest vascular injury and need emergent consultation and likely surgery as soon as possible [9]. Remember that joint reduction should be initiated urgently, as pulses may return after reduction. Patients in whom it is not clear if there is vascular injury should undergo further imaging with angiography, con- sidered the gold standard for evaluation of arterial damage [10].

Illustrative case

A 28-year-old left-hand-dominant man fell on an outstretched right hand while playing football and felt immediate pain and swelling in his arm. Trainers on scene quickly evaluated the patient, noticed elbow deformity, placed him in a sling, and transferred him to the nearest ED for further evaluation and treatment. On arrival in the ED, he was noticed to have an obvious elbow dislocation with pain and local swelling. Neurovascular examination revealed a diminished radial pulse, good capillary refill, and some paresthesias in the distribution of the median

Fig. 1 Radiograph of posterior dislocation. The olecranon has moved posteriorly in relation to the humerus.

Fig. 2 Angiography showing disruption of the Brachial artery with retained distal flow secondary to collateral circulation.

nerve. Radiographs revealed a posterior elbow dislocation without Associated fractures (Fig. 1). The patient underwent procedural sedation, and closed reduction of the elbow was performed using traction and countertraction. Postreduction radiographs showed appropriate reduction of the disloca- tion, but the patient continued to have a diminished radial pulse and paresthesias. Orthopedic surgery was consulted, and the patient was sent for angiography to evaluate for vascular injury. Angiography revealed brachial artery disruption with some preserved collateral circulation, which was felt to account for the diminished but present pulse (Fig. 2). The patient was taken to the operating room for arterial repair and had return of full pulse. He was placed in a posterior splint and 90? sling and was admitted to the hospital for continued observation and neurovascular examinations to monitor compartment pressure. He was discharged with orthopedic follow-up and had good long- term outcome.

Pathophysiology

Elbow dislocations can be classified as posterior, anterior, or divergent, with posterior dislocation further classified based on the final relationship between the humerus and the olecranon as true posterior, posterolateral, or pure lateral, with the position of the ulna dictating the direction. Approximately 90% of elbow dislocations are posterior or posterolateral [3,7]. Anterior elbow dislocations are uncom- mon, accounting for only 1% to 2% of dislocations [2], and will not be reviewed here. Because posterior elbow dislocations are the most common, they are the type of

dislocation injury most likely to be seen in the ED and most likely to require thorough evaluation and management by the emergency physician.

The most common mechanism of injury for elbow dislocation is a fall on an outstretched arm [1-5]. As an individual is falling, the arm hyperextends and abducts. Compressive forces are directed on the outstretched hand and transferred to the radius and ulna, resulting in posterior dislocation. The mechanism begins medially and progresses laterally with progressive subluxation. These disruptive forces in posterior elbow dislocations can also lead to fractures of the radial head and the coronoid process of ulna [3].

The elbow is divided into 2 compartments: anterior and posterior. The anterior compartment contains the brachial artery, median nerve, and ulnar nerve. During dislocation, the distal humerus can cause direct injury to the brachial artery and the nerves within the anterior compartment of the elbow [5]. Emergent reduction is indicated if there is any suspicion of diminished distal vascular perfusion or neurologic compromise. Even with acute reduction, there can be complications with Ischemic injury or direct damage to the brachial artery or median nerve.

Although vascular injury is rare, it is the most important potential complication to evaluate for and rule out in the ED. There is no clear consensus on the incidence, but arterial injuries are estimated to occur in approximately 5% to 13% of elbow dislocations, most frequently in cases of open or Penetrating injuries [2,11-14]. closed dislocations are rarely associated with vascular injury, especially in the absence of accompanying fracture [11,12,14,15]. Since 1913, only a small number of cases of closed posterior elbow dislocations have been associated with arterial rupture [9,16]. None- theless, Ischemic time can cause high morbidity with potential loss of limb, and therefore, any suspicion for vascular injury requires immediate diagnosis and treatment. As previously noted, dislocation can result in compression of the arterial supply without anatomic disruption and may thus improve with reduction of the joint.

The brachial artery is anatomically protected proximally by its more medial position but becomes more vulnerable at its distal end, where it assumes a more anterior position [11,15,17]. Rapid posterior movement of the rigid bicipital aponeurosis (inserted on the distal part of the humerus and proximal part of the radius) occurs with posterior dislocation, and this can disrupt the artery, especially if it becomes trapped between the bicipital aponeurosis and the dislocated bony structures, particularly the distal part of humerus [11]. The artery may also become trapped behind the medial epicondyle of the humerus in the olecranon fossa if the dislocation causes the medial epicondyle to slide out of the olecranon fossa and leave an empty space. The artery may be displaced into this space and then subsequently occluded with reduction [15], a reason it is important to document both a thorough prereduction and a thorough postreduction vascular examination.

Initial diagnosis of brachial artery disruption may not be clinically evident because collateral circulation around the elbow involves 7 vessels (Fig. 3) and can provide residual flow [11,17]. In fact, it is estimated that palpable pulses distal to the trauma may be felt in this situation approximately 10% of the time [10]. This may be protective but can also complicate matters by masking findings and delaying diagnosis of arterial injury [18]. One study examined cadavers after experimentally created posterior dislocations and discovered that 13 of 14 cadavers had disruption of collateral blood flow [19]. In addition to anatomic disruption, elbow swelling after dislocation may compress and compro- mise this collateral circulation and further impair blood flow. Thus, although the absence of a radial pulse should suggest vascular involvement [12,16], the presence of a pulse does not reliably exclude arterial injury [16].

In addition to vascular compromise, elbow dislocations have the potential to cause nerve injury (Fig. 3). Neurapraxia occurs in approximately 20% of cases, with the ulnar nerve or anterior interosseous branch of the median nerve most commonly involved. The ulnar nerve is involved as it crosses the elbow posteriorly and medially in the cubital tunnel of the humerus, and neuropathy results from a stretch mechanism [3,4,20]. In fact, transient ulnar neuropathies with altered

Fig. 3 Illustration showing the nerves of the elbow on the left panel (r, radial nerve; dr, deep radial nerve; u, ulnar nerve; m, median nerve) and the extensive collateral circulation of the elbow on the right panel (b, brachial artery; r, Radial artery; u, ulnar artery; pb, profunda brachii [deep brachial]; suc, superior ulnar collateral; iuc, inferior ulnar collateral; ri, recurrent interosseous; rr, radial recurrent; aur, anterior ulnar recurrent; pur, posterior ulnar recurrent. Some collateral arterial branches have been omitted to simplify the illustration). Note how the ulnar nerve wraps beneath the lateral epicondyle, making it more vulnerable to stretch injuries, and how there can be collateral arterial flow to the radial and ulnar arteries despite interruption of the brachial artery.

sensation over the lateral Fingers and hand can occur in up to 10% to 14% of elbow dislocations [21]. Dysfunction of the ulnar nerve is usually temporary and resolves with conservative management, but prereduction and postreduc- tion examinations should be documented.

Because the median nerve runs with the brachial artery, compromise of this nerve is often associated with con- comitant vascular injury [3,4]. The anterior interosseous branch is most commonly injured. This branch supplies the flexor pollicis longus, flexor digitorum profundus to the index digit and the pronator quadratus. Median nerve entrapment has also been reported with relocation of a dislocated elbow [1,3,4,22]. The median nerve, however, is not involved as frequently as the ulnar nerve. One study showed that of 97 elbow dislocations, only 16 nerve injuries were reported, with 13 involving the ulnar nerve and only 1 involving the median nerve [23]. Another study showed that of 24 nerve injuries in 110 dislocations, 16 were ulnar injuries, 3 were median nerve injuries, 4 were combined ulnar and median nerve injuries, and 1 was a brachial plexopathy [24].

Another important complication to be aware of in elbow dislocations is increased compartment pressures secondary to extensive soft tissue swelling. It is therefore necessary to watch for pain on the passive finger and Wrist extension or extension as well as pain that is out of proportion to the injury [4,20]. If there is doubt about the injury, admission for observation and compartment pressure monitoring may be warranted. If left untreated, ischemia can lead to muscle necrosis, and Volkmann Ischemic contracture may result.

Clinical and radiographic evaluation

When a patient presents with an acute elbow dislocation, it is important to determine the mechanism of injury, time of injury, previous attempts at reduction or any manipulation, and symptoms including any paresthesias. The clinician

should note any deformities, bearing in mind that posterior dislocations often have a prominent olecranon and a forearm that appears foreshortened with arm held in 45? of flexion

[25]; anterior dislocations have a more elongated forearm and the arm is held in extension. It is important to feel for radial and ulnar pulses, remembering, as noted above, that collateral circulation can often mask disruption of the brachial artery so Repeat examinations are necessary [18]. The median and ulnar nerves can be quickly assessed for touch sensation by testing the distal palmar aspect of the first through fifth digits (Fig. 4). Motor function of the median and ulnar nerves can be assessed through the evaluation of abduction and adduction strength of the digits (ulnar nerve), flexion of the thumb interphalangeal joint (anterior inteross- eous nerve), and opposability of the thumb (median nerve). Before and after reduction, it will be important to obtain anterior-posterior and lateral radiographs of the elbow. An anterior-posterior view shows the epicondyles (medial and lateral) and articular surfaces (radiocapitellar and ulnotro- chlear). Lateral views show the relationship between the bones of the distal humerus and the proximal forearm. When evaluating lateral radiographs, it is important to pay attention to a few points (Fig. 5): (1) the line along the anterior humerus should intersect the middle one third of the capitellum (anterior humeral line); (2) the line of the long axis of the radius should extend through the middle of the capitellum (radiocapitellar line); (3) the line drawn along the top of the coronoid process should barely cross the top of the capitellum and trochlea (coronoid line); and (4) the fat pad of the elbow usually sits along the anterior border of the coronoid fossa and is concave shaped. The fat pad is displaced superiorly and ventrally and appears convex if a

fracture (sail sign) is present.

After a dislocation has been identified clinically and radiographically evaluated, it is important to frequently reevaluate for neurovascular injury bearing in mind that, in most cases, soft signs of vascular impairment will be reversed with reduction of the joint [26]. Factors associated

Fig. 4 Sensation distribution of the median (thumb, medial 2.5 fingers), ulnar (lateral 1.5 fingers), and radial (posterior thumb, hand) nerves.

Fig. 5 Radiograph demonstrating normal elbow anatomy with the anterior humeral line (line along the anterior humerus should intersect the middle one third of the capitellum) and the radio- capitellar line (line of the long axis of the radius should extend through the middle of the capitellum).

with a higher incidence of arterial injury include a complete absence of a radial pulse, an open dislocation, and other systemic traumatic injury [25]. If pulses remain diminished after prompt reduction, further imaging is indicated. Angiography remains the gold standard for evaluation of vascular injury [15] and may confirm arterial injury and vascular compromise [10]. Although arterial spasms can decrease pulses after an injury, spasm is not a clinical diagnosis, and an anatomic study [6] is required to rule out acute injury. However, as angiography is invasive with Potential complications, many advocate its use only when there is a high suspicion of injury; if hard signs of vascular injury are present, including complete pulse deficit, obvious arterial bleeding, or rapidly expanding hematoma, many would forego angiography in preference for operative exploration [15].

Treatment

The goal of treatment is prompt atraumatic reduction. If present, an experienced clinician may attempt reduction of a simple dislocation before transport to the hospital because immediate reduction can be easier given there is less time for the patient to develop swelling and spasm [26]. Most patients, however, should be transported for full evaluation in the ED. When a patient is evaluated in the ED, after thorough examination and radiographic evaluation, proce- dural sedation is often needed for reduction to assist with Muscle relaxation and patient comfort.

The most common means of reduction is traction and countertraction. Adequate analgesia and sedation are impor- tant to ensure muscle relaxation before attempts at reduction. Closed reduction is performed with gentle longitudinal traction on the wrist and forearm with countertraction on the upper arm. Downward pressure on the proximal forearm helps to disengage the coronoid process from the olecranon

fossa. A palpable “clunk” during reduction is a favorable sign of joint stability [2,3,25].

After Successful reduction is completed based on clinical evaluation, postreduction imaging should be obtained and a postreduction neurovascular examination performed. Poster- ior splinting will help prevent repeat dislocation in cases of significant instability. As previously mentioned, if there is suspicion for neurovascular compromise, further consultation and imaging should be obtained. Orthopedic consultation should be obtained immediately for any open dislocations, irreducible dislocations, hard signs of neurovascular com- promise, or associated significant fractures [25].

When there is no evidence of neurovascular compromise after reduction, the emergency physician should evaluate elbow stability by examining the joint through a range of motion [3]. If there is any concern for possible neurovascular compromise or compartment syndrome, the patient should be admitted for continued observation [25]. Otherwise, the patient should have the elbow splinted from the axilla to the base of the fingers in 90? for approximately 3 to 10 days [2,3]; longer splint times can be associated with contracture and greater postreduction complications [1]. The patient should be advised to follow up with an Orthopedic surgeon for repeat evaluation and follow-up radiographies. It is important to have a repeat neurovascular examination the following day [25] by the surgeon or emergency provider. Early range of motion exercises and rehabilitation will help to decrease any long-term chronic disability, including stiffness or instability [27,28]. It is rare for a patient to have chronic dislocations given the inherent stability of the elbow [25].

Summary

Although rare, neurovascular complications of elbow dislocations can occur, and a thorough evaluation of pulses and nerve function is necessary both before and after reduction. If there is concern for a neurovascular injury, further imaging and orthopedic consultation are immediately warranted. If there are obvious hard signs of vascular injury, immediate Surgical repair is necessary and further imaging may be deferred. It is important to remember that although absence of a radial pulse should suggest vascular involve- ment, the presence of a pulse does not reliably exclude arterial injury and repeat neurovascular examinations should be performed. Complete absence of a radial pulse before reduction, an open dislocation, and other systemic injury in cases of trauma are more often associated with arterial injury.

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