Subluxation or Dislocation of the Radial Head

Subluxation of the radial head is an injury affecting the elbow joint. The term subluxation means partial dislocation, while the radial head is the name given to the top of the radius, one of the two large bones found in the forearm. Therefore, subluxation of the radial head is an injury where the top of the radial bone becomes partially dislocated from the rest of the elbow. 1

The condition, also commonly referred to as a pulled elbow, babysitter’s elbow, nursemaid’s elbow, RHS or annular ligament displacement, can be caused by a quick pull to the forearm and is a common injury in children, particularly between the ages of one to four. 2 This is because the annular ligament that holds the radial bone in place at the elbow is much weaker in young children, leading to a greater risk of it slipping over the radial head when faced with a sudden, pulling force. ref19

People with a pulled elbow tend to hold the affected arm close to their body, often supporting it against the stomach or with the other hand, and are unwilling to use the arm. They may report pain in the arm. Usually, a subluxation of the radial head can be easily fixed by a doctor by slipping the joint back into place, and complications are uncommon. 3

Full dislocations of the radial head are much less common in children and are also rare in adults. If they do occur, they are typically the result of a high-force trauma or are a congenital condition. Symptoms may be similar to a pulled elbow, but more severe. It is usual for full radial head dislocations to appear in connection with other related injuries in the arm, such as a forearm fracture. 4 Treatment therefore focuses on all associated injuries and may involve surgery.

Types of radial head subluxation and dislocation include:

These terms are all different names for exactly the same injury: a partial dislocation of the radial head. This elbow injury is the most common form of dislocation that can happen to the head of the radius bone in the forearm, and it typically occurs in children aged between one to four years old. Toddlers aged between one to three years old account for over 80 percent of pulled elbow cases. 2

Children are much less likely to experience a full radial head dislocation than a radial head subluxation. However, full dislocations do sometimes occur in children and are still a more frequent injury than subluxations in adulthood. 4

Dislocation of the radial head is often found in people who have sustained a high-force injury, such as a significant car crash or heavy fall. It is typically associated with another injury, such as a fracture to the ulnar, the other bone in the forearm. 4

The condition can also arise due to a congenital abnormality that is present from birth. 5 It is extremely rare for a full dislocation of the radial head to occur in isolation. 4

Because subluxation of the radial head/pulled elbow occurs most frequently in toddlers and young children, it is important to look out for tell-tale symptoms that they may have suffered this injury, such as: 3 6 7

• Holding the injured arm close to the body
• Holding the injured arm in a slightly bent position, usually between 15-20 degrees
• Supporting the weight of the injured arm with the other hand
• Unwillingness to use the arm
• Unwillingness to fully stretch or flex the arm
• Wrist, arm or elbow pain that is often poorly localized, i.e. dull, vague, aching

Although a pulled elbow does typically cause some pain, especially when the injury first happens, it is not always the primary sign that an injury has occured. In some cases, a child may continue to act normally, apart from their reluctance to use the affected arm. 3

Notably, a pulled elbow does not generally cause swelling, bruising or any other type of disfigurement to the affected area. 7

Full radial head dislocations usually result in similar, but slightly more severe symptoms than a pulled elbow. For example, the affected person may still hold the injured arm in a bent position, but at a more acute 90 degree angle. They may also experience a higher degree of pain and show even more reluctance to move the arm.

One major symptomatic difference between radial head subluxations and full dislocations is that full dislocations usually result in noticeable swelling to the elbow, whereas subluxations do not. 4

Concerned you may be experiencing a radial head subluxation or dislocation? Use the free Ada app to carry out a symptom assessment.

There are two bones in the forearm: the radius and the ulna. Both of these bones meet the bone of the upper arm, the humerus, at the elbow. Together, these three bones form the elbow joint. The top, or head, of the radius is surrounded by a flexible, fibrous band of tissue known as the annular ligament, which connects the radius to the rest of the elbow joint.

Radial head subluxations are caused when a part of the annular ligament slips over the head of the radial bone, thereby causing the ligament to become trapped in the radiohumeral joint. 2 The symptoms experienced as part of a radial head subluxation are a result of the annular ligament’s displacement.

A subluxation is a partial dislocation, meaning the bone still has some contact with the ligament. 1 A full dislocation means that the radius bone has been forced fully out of position.

The radial bone can be quite easily subluxated in young children because the annular ligament, that holds the elbow bones in place, is weaker in children than in adults. 8 This injury most commonly occurs when there is a sudden tug on the child's arm, causing the bone to pop out of place.

Possible risk factors for radial head subluxation or pulled elbow include: 8 3 6

• Pulling a child forward by the arm
• Holding a child’s arm in place as they pull away
• Holding or catching a child by the arm as they fall
• Lifting or swinging a child by the arms
• Pulling a child’s arm through a sleeve

Good to know: Falls are not a common cause of a pulled elbow as they are much more likely to result in break or fracture injuries. 9

By five years of age, the annular ligament in the elbow has usually grown strong and tight enough to prevent radial head subluxations from happening with such ease. 8

Full radial head dislocations are typically the result of either an injury or a congenital condition that is present from birth. 5

If caused by an injury, it is extremely rare for the radial head to become dislocated without the presence of any other associated injuries. Disruption to the ulna, the other bone located in the forearm, is the most common associated injury. Injuries sometimes associated with a radial head dislocation, include: 4 10 11

• Ulnar fractures, such as Monteggia fractures
• Other elbow dislocations, such as posterior, anterior and divergent dislocations
• Elbow fractures, such as humeral condyle fractures
• Complex forearm injuries, such as the Essex-Lopresti injury. This injury consists of a rupture to the interosseous membrane – a ligament-like sheet of tissue that provides stability to the bones in the forearm – as well as fracture to the radial head and disruption to the joint that connects the two bones in the forearm, called the distal radioulnar joint.

In adults, dislocation of the radial head is most frequently the result of a high-force injury or trauma, such as a car crash. The dislocation is usually accompanied by other injuries to the elbow or forearm. 12

Some children may be born with a congenital radial head dislocation. This is rare, although it is the most common type of congenital elbow abnormality. 13 When it does occur, it is usually seen in conjunction with other genetic conditions or syndromes, including: 4 12 14 15

• Ehlers-Danlos syndrome, a group of disorders which all affect the body’s connective tissues and can result in joint hypermobility
• Nail-patella syndrome, a genetic disorder which can result in skeletal abnormalities
• Rubinstein-Taybi syndrome, a condition which often results in low bone density
• Radioulnar synostosis, an abnormal connection between the radius and ulna bones in the forearm
• Klinefelter syndrome, a chromosomal condition in which male babies are born with an extra X chromosome, which can result in weaker and more fragile bones
• Achondroplasia, a bone growth disorder that causes dwarfism and can affect the elbows
• Omodysplasia, a rare skeletal abnormality that causes limb shortening
• Hereditary multiple exostoses, where masses of bone develop on long bones in the lower and upper limbs, resulting in potential deformities
• Mesomelic dysplasia, a bone growth disorder that often results in underdeveloped bones in the legs and forearm
• Osteogenesis imperfecta, a genetic condition that results in brittle and easily breakable bones

Infants with a congenital radial head dislocation are often asymptomatic, which means they may display no immediate signs or symptoms of the dislocation. For this reason, diagnosis of the radial head dislocation may occur later in life when they starts using the affected limb more frequently. 13

A diagnosis of radial head subluxation or dislocation is primarily based on a clinical evaluation by a doctor. This evaluation usually includes: 3 6 7

• Physical examination of the affected arm
• Discussion of the symptoms experienced
• Discussion of medical history

Whether a partial dislocation or a full dislocation of the radial head is suspected, a doctor will first need to eliminate a number of other conditions that can present similar symptoms. Such conditions include: 6 16 17

• Radial head fracture
• Other fractures that can affect upper limb mobility, such as fractures to the ulna, clavicle, wrist, hand and other locations in the elbow
• Soft tissue hand injuries
• Other medical conditions that can restrict arm mobility, such as arthritis or a type of bone infection called osteomyelitis
• Neurological causes

When the affected person displays typical clinical signs of a subluxation or pulled elbow, an X-ray is usually not required. This is because a subluxation is only a partial dislocation, and typically does not show up on an X-ray. 3 However, an X-ray may be conducted if: 6 16

• A full radial head dislocation is suspected
• Associated injuries are suspected, such as a fracture
• Symptoms are inconclusive or unusual
• Initial attempts to reset the subluxated joint are unsuccessful

In some cases, an ultrasound test may also be conducted to further assess the injury and avoid misdiagnosis. Ultrasounds can be a useful diagnostic tool in young children who may not be able to fully communicate their symptoms. 6

MRI scans can also be used to confirm diagnosis and assess damage to the surrounding ligament. However, this would usually only be suggested to people who have experienced recurrent elbow dislocations and therefore may have significant tissue damage. 16

People who are concerned they may be experiencing a subluxation or dislocation of the radial head can use the free Ada app to carry out a symptom assessment.

The exact method chosen to treat a radial head subluxation or dislocation can depend on a number of factors, such as: 16 18

• Whether the injury is a subluxation or a full dislocation
• Whether any other associated injuries, such as fractures, are present
• Whether the affected person is a child or adult
• Whether the condition is the result of an injury or a congenital abnormality

Attempts to manually manipulate the radial head back into the joint, known as a closed reduction, is usually the first treatment method for people without associated injuries. 3 Closed reductions can often be quickly and easily performed by a doctor, particularly in pulled elbow cases.

If a pulled elbow is suspected in a baby or child, it may not even be necessary to administer sedatives or pain relief before attempting to move the bone back into place. 3 However, if the affected person is an adult, or the injury is a full dislocation, pain relief medication may be prescribed during the closed reduction process.

A soft click might be heard as the radial head slips back into its correct position. Once reset, it is usual for the affected person to regain normal function and movement of their arm within half an hour. 6 When function has returned, there is usually no further treatment required. A sling or cast may be offered to help support or immobilize the arm during recovery. 16

If a closed reduction is unsuccessful, pain continues, or the affected person is still not able to fully use their arm after a couple of days, further tests such as X-rays may be required, and surgical intervention might become necessary. 16

Surgical treatment to put the radial head back into place, known as an open reduction, may be recommended for people who have other injuries, or people for whom closed reduction attempts were unsuccessful. 6 18 Adults are more likely to be recommended for surgical treatment than children because their joints are less flexible and may not be as easily restored as those in children.

Surgery may target the radial head itself or, when there are associated injuries, may target the associated injury instead. For example, when the forearm bone known as the ulna is fractured, fixing the ulna usually results in the radial head moving back into place of its own accord. Plates and screws may be used to fix the ulna in place, ensuring normal length and alignment of the bone following a fracture. This reduces the chance of radial head dislocation occuring again in the future. 18

Because radial head subluxations and dislocations are complex injuries that can present similar symptoms to other injuries, they have the potential to be missed or misdiagnosed by medical professionals, leading to a chronic condition. If left undiagnosed for more than three years, deformities to the radial head can develop. 18. For this reason, previously undiagnosed radial head subluxations or dislocations are often treated surgically.

When a radial head dislocation is due to a congenital abnormality, initial treatment is usually non-surgical. 15 If surgery is required, it is often conducted in adulthood to correct restricted movement, pain or cosmetic concerns. 14

Pulled elbow injuries can often be prevented by providing carers of young children with a better understanding of how the injury occurs and what scenarios are most likely to cause it, e.g. swinging a child by the arms or pulling a child firmly by the arm. 16

Full radial head dislocations are most often the result of high-force injuries such as car accidents or significant falls. Therefore, avoiding high-risk scenarios such as contact sports or motorsports may help prevent injury from occurring.

• Pulled elbow
• Babysitter’s elbow
• Nursemaid’s elbow
• Partial dislocation of the radial head
• Annular ligament displacement
• RHS
• Pronatio dolorosa

Good to know: While subluxation of the radial head has a variety of different names, full dislocation of the radial head is most often referred to simply as dislocation of the radial head.

Q: Are radial head subluxation and dislocation the same thing?
A: No, they are two different types of a similar injury. A person with a radial head subluxation has a partial dislocation, where the annular ligament that holds the radial bone in place at the elbow has slipped over the top of the bone. A dislocation is where the affected bone is forced completely out of position.

Worried you or a loved one may have a subluxation or dislocation of the radial head? Use the Ada app to carry out a free symptom assessment.

Q: Does radial head subluxation or dislocation occur in adults?
A: Yes, although both conditions are more common in childhood. Subluxations of the radial head/pulled elbows most commonly occur in children under the age of five and are rare in people older than this. 16 It is such a common injury in this age group, because the annular ligament that connects the radial bone to the rest of the elbow joint is much weaker in young children. By five years of age, the annular ligament is usually sufficiently strong to hold the radial head in place when a pulling force is placed on the arm.

Adults are more likely to experience a radial head dislocation than a subluxation. Usually, the injury is the result of a trauma or high-force injury, such as a car accident or heavy fall.

Q: Is it possible to experience bilateral elbow dislocation?
A: Bilateral elbow dislocation, meaning the dislocation of both elbows at the same time, is extremely rare. A 2012 study commented that only 12 cases of bilateral elbow dislocation had ever been reported in medical literature. 19

Q: Will subluxation or dislocation of the radial head require an X-ray?
A: An X-ray is usually not required when treating a radial head subluxation. This is because the injury typically does not not show-up on an X-ray, and also because, in some cases, the injury can be easily reset after a clinical evaluation, without the need for any further diagnostic tests.

If attempts to reset the joint are unsuccessful, a doctor may then recommend an X-ray to see if there are any underlying issues preventing manual treatment. An X-ray is also more likely to be suggested to people who are suspected to have a full radial head dislocation, other associated injuries, or who are displaying inconclusive symptoms.

Q: What is a congenital radial head dislocation?
A: A congenital radial head dislocation is when the condition occurs due to a genetic abnormality or syndrome that is present from birth, rather than acquired through force or trauma. Often, this condition is initially asymptomatic and only presents when the child is slightly older and begins using their arm with more frequency. Congenital radial head dislocations can usually be treated without the need for surgical intervention.

Q: What is a chronic radial head dislocation?
A: A chronic radial head dislocation is a dislocation that has been previously neglected, either through omission or misdiagnosis. Undiagnosed radial head dislocations can lead to elbow stiffness, limited function, deformity and pain. Once detected, chronic radial head dislocations are usually corrected through surgery.