Anterior Elbow Dislocation

Etiology

This injury and its complications are best understood after reviewing pertinent anatomy. The elbow is a joint formed by the articulation between 3 bony structures: the humerus, ulna, and radius. The distal humerus is the most proximal aspect of the elbow. The distal humerus flares out medially and laterally, forming the medial and lateral epicondyles. The trochlea and capitellum comprise the humerus's distal joint surface, articulating with the greater sigmoid notch of the proximal ulna and the radial head, respectively.[3] 

The olecranon is the posterior portion of the proximal ulna and forms the posterosuperior part of the greater sigmoid notch.[3] The coronoid process of the proximal ulna forms the anterior portion of the notch and is where the brachialis and anterior medial collateral ligament attach. Laterally, the proximal ulna features a lesser sigmoid notch, also known as the radial notch, where the proximal radius articulates. 

The soft tissue surrounding the elbow joint contributes to the stability of this tripartite joint. The annular ligament surrounds the radial head and is an insertion site of the joint capsule. The joint capsule also inserts onto the anterior aspect of the coronoid. Posteriorly, the joint capsule attaches to the olecranon. The capsule contributes to the varus-valgus stability of the elbow when the elbow is in extension.[4] 

The medial and lateral collateral ligaments also reinforce the varus-valgus stability of the elbow. Further, the medial ulnar collateral ligament contributes to the valgus stability of the elbow and consists of the anterior, posterior, and transverse bands. The medial collateral ligament originates from the medial epicondyle and inserts at the base of the coronoid.[5]

The lateral collateral ligament contributes to the varus stability of the elbow and consists of 3 components: the lateral ulnar collateral ligament, the annular ligament, and the radial collateral ligament.[3] The lateral ulnar collateral ligament inserts on the lateral epicondyle and the supinator crest on the proximal ulna, giving the elbow posterolateral stability. The annular ligament wraps around the radial head and attaches to the radial notch on the ulna, stabilizing the radioulnar joint. The radial collateral ligament stabilizes the radial head by connecting the lateral epicondyle and the annular ligament.

Epidemiology

Anterior elbow dislocation is a rare injury, accounting for approximately 2.6% of all elbow dislocations.[6] The rarity of this condition is due to the substantial force and specific elbow positioning necessary to cause such a dislocation.

History and Physical

Anterior elbow dislocations, like all elbow dislocations, occur after a traumatic event. Patients typically have a history of some mechanism causing them to fall onto their outstretched arm or more severe trauma to the arm, like a motor vehicle accident. Patients complain of severe pain in the injured extremity and are unable to move the injured elbow. Patients may also complain of a noticeable deformity of the affected elbow, depending on body habitus and the nature of the dislocation.[7] While obtaining the history, the examiner must ask the patient if they have previously dislocated or had any history of injury to the dislocated elbow. The clinician should also ask the patient if they have any new onset of numbness, tingling, or weakness in the injured extremity, as damage to neurovascular structures can be associated with anterior elbow dislocations.

Neurovascular compromise can affect the urgency of reduction and operative fixation. The examiner should inquire whether the patient has had any head trauma, loss of consciousness, or any other areas of pain, as this influences whether further workup needs to be performed or not. Finally, each patient should be asked to provide their complete medical history, including any congenital deformities and medications that may affect their diagnosis and treatment.[8]

Evaluation

The initial evaluation should begin with an inspection of the patient and a physical exam. Clinicians should evaluate for additional injuries visually and by palpating along with other bones and joints. The injured extremity should be assessed for open fractures, swelling, skin changes, and neurovascular status. Palpation along the injured extremity should be performed to ensure that all compartments are compressible.

If a compartment is too full to compress, the examiner should be concerned about developing compartment syndrome, which is a surgical emergency. If the patient has compartment syndrome, their neurovascular status will be diminished. Vascular status can be assessed by observing the extremity's color, palpating the skin temperature, checking the radial and ulnar pulses at the wrist, and evaluating the capillary refill of the fingers.[9]

Neurological status can be evaluated by checking for sensation along the length of the extremity and having patients perform tasks to demonstrate motor function. Compartment syndrome, an open fracture, or neurovascular compromise all warrant emergent evaluation by an orthopedic surgeon. The median and ulnar nerves are the most common nerves injured during an elbow dislocation. The median nerve sensation can be evaluated by light touch to the palmar aspect of the thumb and index finger. The motor function of the median nerve can be tested by observing the strength of thumb opposition.[10]

Ulnar nerve sensation can be determined by light touch over the palmar aspect of the fourth and fifth digits. The motor function of the ulnar nerve is assessed by observing the strength of the abduction and adduction of the fingers. After the physical exam, radiographic images should be obtained. Initial radiographic evaluation of the injured extremity should begin with anteroposterior, lateral, and oblique views. However, obtaining anteroposterior and lateral forearm, wrist, and shoulder films to evaluate for any other potential injuries is also vital.

Treatment / Management

Closed Reduction

Initial management of an anterior elbow dislocation should involve closed reduction when the patient presents within three weeks of the injury. Reduction can help decrease pain and swelling and take pressure off soft tissue and neurovascular structures. Anterior elbow dislocations require modification to the typical elbow reduction maneuvers.[11]

In most cases, the patient requires intravenous sedation to relax the muscles, allowing for proper manipulation for reduction. Once adequate sedation is achieved, longitudinal traction should be applied to the affected arm. Ideally, 2 clinicians perform the maneuver—one applies traction to the forearm and the other provides counter-traction at the humerus. Reduction of anterior elbow dislocation is accomplished by gradually flexing the elbow while maintaining traction and applying a downward force to the proximal forearm.[12](B3)

After reduction, the stability of the elbow should be assessed with a range of motion and varus and valgus stress tests. An unstable elbow after reduction is more likely to need operative intervention than a stable elbow. The neurovascular status of the extremity should also be reevaluated after reduction. A posterior, long-arm splint should be applied with the elbow flexed at 90°. Postreduction radiographs should be taken after the splint is placed to ensure the elbow is adequately reduced. Closed reduction may be hazardous due to soft tissue contractures and localized osteoporosis. Fractures may occur during a reduction procedure; therefore, gentle and meticulous manipulation is crucial.[13]

Elbow instability is indicated by a widening of more than 1 mm at the ulno-humeral joint during a valgus stress test, more than 1.5 mm at the radio-capitellar joint during a varus stress test, elbow joint redislocation, and the "drop sign." The drop sign, also known as an increased ulno-humeral distance (4 mm) on an elbow radiograph taken laterally, describes instability following the reduction of elbow dislocation.[14] A trans-olecranon K-wire fixation or spanning external fixator should be used if there are features of elbow instability.

The elbow should remain splinted and reevaluated 5 to 10 days after reduction.[10] At that point, the patient's elbow should be reexamined for stability and neurovascular status. The patient requires operative intervention if the elbow remains unstable or demonstrates a fracture on an x-ray. If the elbow is stable on the exam, the patient may begin an early range of motion to prevent stiffness. Elbows tend to stiffen if they are immobilized for more than 3 weeks. After approximately 21 days of immobilization, it becomes challenging for the patient to regain the full range of motion in their elbow.[15]

Open Reduction

Elbow dislocations left untreated for more than 3 weeks typically require open reduction, as chronic cases often involve a shortened triceps muscle and contracted surrounding soft tissues that hinder closed reduction. The objectives of open reduction include V-Y or Z-plasty lengthening of the triceps, release of the medial and lateral collateral ligaments, excision of the radial-humeral horn formed by subperiosteal new bone, and decompression or transposition of the ulnar nerve. Following successful reduction of the joint, stabilization is achieved by placing K-wires across the ulnohumeral and radiocapitellar joints.[13]

Alternatively, a hinged external fixator is applied without collateral ligament reconstruction. In neglected elbow dislocations, Ivo et al demonstrated good functional outcomes using hinge fixators without the requirement for collateral ligament restoration.[16] Ligament reconstruction is indicated for cases of acute injury in athletes, high-grade tears, and chronic instability of the elbow joint. Ligament reconstruction is protected by applying a hinged external fixator for 8 weeks. After the range of motion is recovered, supporters of ligament restoration assert that failure to reconstruct the collateral ligaments may result in elbow instability. However, opponents of ligament restoration claim that non-anatomic ligament restoration may limit the range of motion and contribute to the development of arthritis.[17]

Elbow Arthroplasty

Neglected elbow dislocations lasting more than 6 months may require interposition arthroplasty with fascia lata, arthrodesis, or total elbow joint replacement.[18][19](B2)

Differential Diagnosis

Anterior elbow dislocations are uncommon and typically diagnosed through clinical evaluation supported by radiographic imaging. However, when a patient presents with acute elbow pain following trauma, it is essential to consider a broad differential diagnosis to ensure accurate and timely management.

Potential Differential Diagnoses 

Posterior elbow dislocation (the most common type of elbow dislocation)

Fractures:

• Radial head or neck fracture
• Olecranon fracture
• Distal humerus fracture (supracondylar or intercondylar)
• Coronoid process fracture

Ligamentous injuries:

• Medial or lateral collateral ligament sprain or rupture
• Elbow instability without dislocation

 Tendon injuries: 

• Distal biceps tendon rupture
• Triceps tendon avulsion 

Neurovascular injuries:

• Brachial artery injury
• Median, ulnar, or radial nerve injury

 Soft tissue conditions: 

• Elbow joint effusion or hemarthrosis
• Muscle contusion or strain

Clinicians should employ a comprehensive approach that integrates the mechanism of injury, a detailed physical examination, neurovascular assessment, and appropriate imaging—starting with plain radiographs and progressing to computed tomography or magnetic resonance imaging, as necessary. This structured evaluation ensures an accurate diagnosis and guides appropriate treatment, particularly in distinguishing between simple dislocations, complex fracture-dislocations, and isolated soft tissue injuries.

Prognosis

The most common lifelong negative outcome after an anterior elbow dislocation is the loss of terminal extension. Patients with a simple anterior elbow dislocation have a strong chance of regaining a full range of motion after recovery. However, patients with injuries requiring more than 3 weeks of immobilization, such as complex anterior elbow dislocations or those with neurovascular injuries, tend to lose terminal extension. Unfortunately, loss of 10° to 15° of terminal extension range of motion after an elbow dislocation is common.[20]

Complications

Common complications associated with anterior elbow dislocations are generally the same as those associated with all elbow dislocations. Heterotrophic ossification and stiffness with a limited range of motion, specifically loss of terminal extension, are the most common complications after complex elbow dislocation.[21] This occurs with prolonged immobilization, typically over 3 weeks, and can be improved by physical therapy focusing on a range of motion.

Persistent elbow instability is another complication that can occur after an elbow dislocation. Varus instability is the most common due to insufficiency of the lateral collateral ligament. Lateral collateral ligament insufficiency can be treated by splinting in pronation but may require surgical repair.[20]

Neurovascular injury can be a complication of an anterior elbow dislocation. The 3 neurovascular structures of the elbow most commonly injured are the ulnar nerve, median nerve, and brachial artery. Due to the nerve's stretching during the dislocation, ulnar nerve neuropraxia is the most frequent damage, with median nerve neuropraxia following second in frequency.

Neuropraxias are initially managed by observation and typically resolve over time. Median nerve entrapment can occur when there is a fracture, which warrants surgical exploration of the nerve.[1] Finally, injury to the brachial artery is a rare occurrence usually associated with severe, open fracture-dislocations. Pulses typically return after reduction; further workup and surgical intervention are required if they do not.[22]