Posterior Elbow Dislocation

Definition/Description

Posterior elbow dislocation (PED) occurs when the radius and ulna are forcefully driven posteriorly to the humerus.

Specifically, the olecranon process of the ulna moves into the olecranon fossa of the humerus and the trochlea of the humerus is displaced over the coronoid process of the ulna. PED is classified as simple or complex and staged according to severity.

Epidemiology /Etiology

In children under 10 years, PEDs are the most common type of joint dislocation. 

In adults, they are the second most commonly dislocated joint proceeded by shoulder dislocations.

Elbow dislocations annually affect between 6 and 7 people per 100,000. Approximately 90% of all elbow dislocations are directionally classified as posterior or posterolateral and are more commonly seen in the non-dominant upper limb. 

Typically, elbow dislocation is caused by a traumatic fall onto an outstretched hand resulting in an hyper-extension injury. However, more recent research has suggested that axial compression, elbow flexion, valgus stress, and forearm supination lead to a rotational displacement of the ulna on the distal humerus. 

Most commonly, the dislocation is associated with a damaged or torn anterior capsule.

Classification

PED can be classified as simple or complex.

1. A simple dislocation is classified as a dislocation without the presence of a fracture.
2. A complex dislocation has related fractures. 
   • Fractures may exist on the radial head, coronoid process, olecranon, humeral condyles, or capitellum. 
   • These fractures may lead to disruption of the medial collateral ligament (MCL), lateral collateral ligament (LCL), or interosseous membrane. 
   • 'Terrible triad' is a term used to describe a severe complex dislocation with intra-articular fractures of the radial head and coronoid process. Elbow dislocations are staged depending on the disruption of the following stabilizers: the ulnohumeral articulation, MCL, and LCL.

Characteristics/Clinical Presentation

The clinical presentation may include:

• Instability
• Popping sensation on immediate injury
• Pain
• Weakness
• Reduced AROM
• Swelling - the olecranon may be prominent creating a divot over distal triceps
• Joint line tenderness on palpation
• Recurrent dislocations can occur if a ligament injury is also sustained

Differential Diagnosis

To diagnose PED, radiographs in the anterior, posterior, and lateral views with valgus stress are obtained.

Table 1: below depicts other injuries that should be considered when suspecting PED.

Diagnosis	Cause	Examination Findings
Posterolateral Rotary Instability	Insufficiency of the ulnar LCL	Valgus instability Positive lateral pivot-shift test Recurrent dislocations
Associated Fracture	Traumatic forces through radial head, humeral condyles, coronoid process, olecranon, or capitellum	Radiographic diagnostics Tenderness over fracture sight. Positive Elbow Extension Sign
Compartment Syndrome	Fractures, swelling, casting, trauma	Pain out of proportion to the injury Absent pulse Pallor Paresthesia Paralysis
Complex Regional Pain Syndrome (CRPS)	Unknown	Persistent pain after injury, Swelling Hypersensitivity Change in skin colour/texture, Reduced ROM Weakness

Examination

Physiotherapy Examination

Physical therapy examination should include:

• Observation - specifically deformities
• Vascular screen - palpation of brachial, radial and ulnar arteries
• Neuromuscular screen - dermatomes, myotomes and reflexes including upper limb neuro-tension tests (if tolerated by patient)
• Palpation - It is essential to palpate for associated fractures in the elbow complex. The elbow extension sign can be used to rule out a fracture.
• ROM
• Muscle testing
• Ligament integrity tests - varus and valgus stress test, the lateral pivot-shift test/ apprehension test (Posterolateral Rotational Instability Test).

Medical Management

Before surgery is considered, research indicates reduction under local or general anaesthetic as the primary treatment for PED. 

Radiographs are indicated when there is no response to care after four weeks of conservative treatment, significant activity restriction for more than four weeks, or non-mechanical pain is present. 

Prior to the decision to surgically manage these factors are considered:

• Pain
• Irreducible dislocation
• Instability (recurrent instability may indicate a ligamentus repair
• Elbow stiffness
• Fractures
• Neuro-vascular injury

The most common surgical options include an open procedure, and excision or closed arthroplasty.
An open procedure, more likely when fractures are involved, can include:

• Ulnar nerve release,
• Humeroulnar reduction
• Humeroradial reduction,
• Triceps lengthening using Speed's procedure
• Wires and/or screws placed in the olecranon for stabilising the joint.
• Ligamentus repairs with sutures

Once surgery is complete, the patient is immobilised with time frames varying based on the individual and the surgeon's protocol. 

Hinged braces, fixators, plaster casts, and slings are utilised to keep the elbow in a position of approximately 70-80^o of flexion and slight pronation.

Physiotherapy Management

While conservative treatment approaches to PED can vary depending on the level of tissue involvement, there are key elements to consider throughout the clinical decision-making process. PED can occur on a continuum of severity; therefore, the treatment must be diverse as well.

Treatment can vary from aggressive immediate AROM to traditional plaster immobilisation for several days depending on orthopaedic intervention. If a fracture occurs secondary to dislocation, intra-articular bone fragments and fracture position may dictate treatment.  

Following a typical reduction with no fracture:

1. Immobilisation: typically involves the use of a posterior splint at 45-90^o of elbow flexion for three days to three weeks.Throughout the immobilisation phase, wrist and shoulder function should be maintained through ROM and strengthening exercises. Inflammation is a common following PED and can be addressed using PRICE protocols. 
2. After the immobilisation phase physiotherapy begins with gentle AROM and PROM exercises in a pain-free range targeting the entire upper limb.
3. When pain is no longer a barrier to treatment, functional progressive resistance exercises should be implemented to improve total upper limb muscle strength and endurance. 
4. Therapeutic goals in the later phase of rehabilitation include attaining full ROM and strength capabilities of the entire affected arm, suppression of pain, and restoration of functional abilities to pre-injury level.
5. A patient is able to return to functional activities around twelve weeks and sports around six months. 

Complications post reduction

There can be detrimental effects of prolonged immobilisation including flexion contractures, enhanced perception of pain, and increased duration of disability, all of which prolong the rehabilitation process. 

When treating a post-surgical PED patient, physical therapists should be cautious of pin site infection. 

Although full extension should be a goal of rehabilitation, care must be taken to protect the vulnerable elbow and avoid hyperextension. It is important to be cautious during passive mobilisation and ROM.

Resources

American Academy of Orthopedic Surgeons

eMedicine

Clinical Bottom Line

Since the elbow joint is one of the more commonly dislocated joints, it is imperative that physiotherapist are aware of its complications and the best evidence for treatment.

It is important to explore the level of severity and degree of complication associated with each PED since this dictates the patients' prognoses. Patients who have had simple PED with early reduction usually have good outcomes.

In most cases, there is potential for developing instability and degenerative joint disease. 

Overall the best treatment for PED is initial short term restricted ROM (usually two weeks or less) followed by early mobilisation including PROM, progressing to AROM and functional strengthening.