Definition
An elbow dislocation of occurs when the bone of the upper arm (humerus) is separated from the bones of the forearm (radio and ulna), creating a displacement of the elbow joint.
Pathology
A dislocation of the elbow is mainly caused by trauma when an excessive force is applied to the elbow disrupting the joint capsule. This injury represents the second most common joint dislocation following the shoulder. The elbow is a complex joint being both a hinge as well as a ball and socket joint. The first joint allows the bending while the second the rotation of the elbow. When subjected to high energy forces, any of these movements can cause a dislocation of the elbow, resulting in a tear of the ligaments and tendons. In more complex cases a joint dislocation is associated with the fracture of the bones forming the joint.
Classification
Elbow dislocations are defined based on the direction in which the bones dislocate and their displacement relative to the humerus: posterior, postero-lateral, postero-medial, lateral, medial, or divergent. Below the description of the most frequent types:
Posterior dislocations comprise 90% of all elbow dislocations
Anterior dislocations are rare and involve the slide of the forearm bones forwards
Divergent dislocations consist in the reciprocal dislocation of the ulna and radius but are the rarest type of dislocation
Radial head subluxation is the most common in children when the radial head slides below the annular ligament.
In addition elbow dislocations are divided according to their complexity:
Simple Elbow Dislocation - implies the absence of any bone fractures to the bones forming the joint. This has a less complicated prognosis with no surgery required.
Complex Elbow Dislocation - involves the rupture of the ligaments and bone fractures mostly to the forearm. In this case surgery is often required to realign the elbow joint into a normal position.
Severe elbow dislocation - a severe dislocation of the elbow is accompanied by damage to other structures including bones, blood vessels and nerves that travel across the elbow.
Associated injuries
Intra-articular complex elbow dislocations are associated with rupture of the elbow capsule, and ligaments as well as fractures to the radial head, olecranon, coronoid process. Damage may also ensue to the arteries and the ulnar, radial and median nerves. Neurovascular injury can compromise blood perfusion and neurological function up to paralysis thus posing risk to lose the forearm. For this reason an elbow dislocation requires immediate medical attention and possibly surgical treatment. As a result of trauma the patient may develop compartment syndrome. This consists in substantial swelling of the soft tissues around the elbow and forearm. The increased pressure may compromise local blood perfusion leading to ischaemic injuries to muscles and nerves.
Causes
Elbow dislocations are caused by direct trauma to the arm or elbow and by axial loading transmitted through the elbow during a fall on the outstretched arm. It is most frequent in males and children. Approximately half of all elbow dislocations observed in teenagers and young adults arise from sport accidents. Generally the most common causes of this pathology are:
Pulling/swinging young children by the hands/wrists (radial head subluxation) with extended arms also called nursemaid's elbow
Fall onto the outstretched hand or arm
Direct impact in contact sports
Motor vehicle accidents
Risk factors
The risk factors for an elbow dislocation include:
Tendency to fall
Sport in teenagers
Weakness of elbow ligaments in children
Epilepsy
History of a previous elbow dislocation or elbow instability
Inadequate rehabilitation following an elbow dislocation
Inappropriate sport training technique
Congenital joint laxity
Congenital malformation of the ulna (flat groove)
Symptoms
The symptoms of a dislocated elbow comprise:Sudden severe pain at time of injury
Deformed elbow (complex dislocation)
Protruding olecranon and shorter forearm (posterior dislocation) Longer forearm (anterior dislocation)
Swelling
Bruising
Tenderness at touch
Changes in sensation of the areas innervated by the radial and median nerves
Changes in motor function of the thumbs and fingers controlled by the radial and median nerves
Diagnosis
Physical examination begins with the medical history including the mechanisms that have caused an elbow dislocation. A closed reduction may need to take place immediately after the diagnosis. During the examination the physician will:
Assess the presence of deformities and bruises around the elbow
Perform tests to determine the level of pain when the elbow is moved passively in extension and supination
Check pulses to exclude associated vascular compromise to the brachial artery
X-ray is the standard method to identify an elbow dislocation and the possibility of associated bone fractures. A CT scan may be taken after the X-rays to achieve a more detailed image of the bones whereas ultrasound and MRI provide images of soft tissue damage mostly to the ligaments. Following a closed reduction a second set of X-rays is taken to confirm the correct repositioning of the elbow. Angiography is used when vascular damage is suspected.
Assessment of the radial nerve
The radial nerve innervates the dorsal extrinsic muscles in the forearm and is the nerve that may be most likely damaged with an elbow dislocation. Severe injury of this nerve causes hand drop. Rarely, the median or ulnar nerves are affected. Specific functional tests of the radial nerve will look for changes in motor and sensory function:
Extension of the wrist and metacarpo-phalangeal (MCP) joints with abduction and extension of the thumb
Flexion of the fingers at the MCP joints and adduction of the thumb
Dysesthesia or anaesthesia on the dorsum of the thumb.
Treatment
Nonoperative treatment
Following a dislocation, the elbow may reposition spontaneously but only if subluxated. In case of simple dislocation it is advised to immediately perform a manual reposition the elbow (closed reduction) by a trained medical staff by applying a quick motion to the forearm. This procedure is usually done under anaesthesia or analgesia at the Emergency Department. An early reduction of the elbow prevents any detrimental consequences if vessels and nerves are torn. The reposition of the elbow is followed by:
Rest
Application of ice pads
Administration of NSAIDs
Pain killers
Early physiotherapy to prevent reduction of range of movement
Surgical treatment
In complex elbow dislocations involving bone fractures and tear of the ligaments (approximately 1-2%) surgery is needed to restore alignment, function and repair the ligaments. The approach to surgery depends on the extent of the damage. This includes:
Internal or external fixation to stabilise the elbow and/or the fracture (e.g. using plates and screws)Repair of the damaged ligaments and vessels
Complications arising from an elbow dislocation include:
Elbow stiffness (15%)Compartment syndrome
Persistent pain
Ectopic calcification (calcium deposits in the ligaments)
Arthritis of the elbow
Rehabilitation
Initially after either conservative or surgical treatment a splint/brace is applied for a short period in most patients with elbow dislocation to prevent a second dislocation. During convalescence the patient will keep on the following regimen:
Avoid strenuous arm movements and weight lifting
Begin early mobilisation exercises to prevent stiffness and weakness of the elbow
Massage
Joint mobilisation
Stretches
Electrotherapy
Activity modification advice
Return to sport/work plan
Postural taping
Prevention
Although half of the patients have a full recovery, a joint dislocation frequently reoccurs. Therefore it is critical to adopt simple preventative rules to protect the elbow such as:
Avoid to pull young children by the hands/arms/wrists
Use of taping and bracing to protect the elbow during sport or other physical activities
Physical exercise to strengthen the muscles of the arm and maintain elbow flexibility
Return to sport with guided training by a physiotherapist only when symptoms have subsided
Possible necessity to quit contact sports such as football and rugby