What is Wrist Dislocation?
Wrist dislocations can happen in several parts of the joint and can sometimes occur due to severe trauma that affects multiple areas. There can be unusual forms of dislocation that involve certain bones in the wrist, like the lunate and perilunate dislocations, which although uncommon, are frequently overlooked. Dislocations of the joint between the wrist and the forearm often occur alongside fractures in the lower portion of the forearm bone. This type of injury, known as a Galeazzi fracture-dislocation, is more common. Wrist dislocations, in general, are quite rare, making up between 0.2% to 2.7% of all wrist injuries.
About 7% to 10% of all injuries involving the small, pea-sized bones of the wrist, known as the carpal bones, are related to instability of these bones. These bones are held together by internal ligaments, and external ligaments link them to the joints near the two long forearm bones. If these ligaments get damaged, it makes the wrist unstable. Such instability can occur in different forms – in either a single row of carpal bones (‘carpal instability dissociative’), due to instability between rows of carpal bones (less common, known as ‘carpal instability non-dissociative’), in response to other changes (maladaptive carpal instability’) and in complex combinations (‘carpal instability complex’). An example of carpal instability dissociative is an injury to the scapholunate ligament which leads to instability between wrist bones.
Most wrist instability issues mainly involve the lunate bone because it is located in the middle of the wrist. These injuries can happen progressively, depending on the severity, starting from instability in the scapholunate ligament to dislocation of the lunate bone. Such dislocations and perilunate dislocations are usually high-energy injuries, caused by events like fallings from a height, car crashes, or sports injuries. Although not very common, these injuries can lead to many complications. Despite the immense force usually required to cause these injuries, about a quarter of them are initially missed when examining or imaging the wrist. It’s also worth noting that perilunate and lunate dislocations are twice as likely to occur together with fractures than without them.
What Causes Wrist Dislocation?
Your wrist is a complicated structure made up of many bones and ligaments, which are like ropes holding everything in place. Some ligaments attach bones of the wrist to the arm and the hand, while others connect the tiny wrist bones to each other. The ligaments found on the palm side of the hand are especially strong. One such ligament is the short radiolunate ligament, which connects the lunate bone (a moon-shaped wrist bone) to the arm’s bone.
The point where the two bones of the forearm meet, right near the wrist, is called the Distal Radioulnar Joint. It’s mainly held in place by deep ligaments that are part of a structure called the triangular fibrocartilage complex. This joint can become unstable if these ligaments tear or if there’s a particular break in the forearm called a Galeazzi fracture-dislocation.
The particular bone called the lunate is crucial in the wrist setup. It’s located in the upper group of wrist bones, sitting between two other bones. There are several ligaments that stabilize this bone, but importantly, there are no muscle or tendon attachments. Since the upper group of wrist bones is less stable than the lower ones or lower forearm, this area is more prone to injuries.
Wrist injuries often happen due to trauma, such as falling on an outstretched hand or when the wrist bends too far back. The sequence of injuries often happens in a specific pattern, described by the Mayfield classification. According to this system, the ligament between two particular bones would be the first to break, followed by disruptions in the joints between various wrist bones. The lunate bone at this stage can slip out of place from its original position. If the injuries continue, in the last stage, another ligament called the dorsal radiocarpal ligament can fail, leading to further displacement of the lunate bone.
Risk Factors and Frequency for Wrist Dislocation
Wrist fracture-dislocations, which are a combination of a bone break and a joint dislocation, happen quite often. However, cases where there is only a dislocation, without a fracture, are rare.
Signs and Symptoms of Wrist Dislocation
Patients usually land at the hospital with a history of wrist injury, often from a fall onto an outstretched hand. Pain is typically focused in the middle of the wrist but can spread more widely depending on the severity of the injury. It’s crucial to ask if the patient is feeling tingling sensations or “pins and needles” in the hand, as it could be a sign of acute carpal tunnel syndrome. Information about which hand is dominant, the person’s job, hobbies, health conditions, and smoking habits will also be beneficial.
Physicians will examine patients according to Advanced Trauma Life Support principles, since these types of injuries often result from high-intensity trauma. In a typical exam, the lunate bone in the wrist is felt for near the middle finger. If a patient flexes their wrist, this bone becomes easier to detect.
Given the wide range of possible ligament damage, signs and symptoms can heavily vary. As an example, an injury to the scapholunate ligament (the most frequently hurt ligament in the wrist) can cause localized pain and swelling on the thumb side of the wrist, a popping or clicking sensation with wrist movement, and pain with overextension of the wrist.
Injuries that dislocate the lunate or disturb the area around it generally result in overall wrist pain and swelling, often worsening with movement. In such cases, no gross deformity is usually present; however, there might be a noticeable fullness of the carpal tunnel. If the lunate is pushed towards the palm, it may cause injury to the median nerve.
Identifying acute carpal tunnel syndrome quickly is critical in trauma cases and requires a detailed neurological examination of the hand. Signs of possible median nerve damage include:
- Loss of feeling in the thumb, index, middle fingers, and part of the ring finger
- Weaker ability to bend and move the thumb
- The thumb muscle (abductor pollicis brevis) doesn’t contract properly when attempting to move the thumb away from the hand
Additional injuries further up the arm can affect other nerves as well. Acute carpal tunnel syndrome might occur in up to 46% of wrist dislocations.
Testing for Wrist Dislocation
If you hurt your wrist and your doctor suspects it might be dislocated, they’ll likely use x-ray images — taken from several angles — to figure it out. This usually includes an anteroposterior (front to back), lateral (side to side), and oblique (angled) view. These simple x-ray images can often help to diagnose major wrist injuries that may otherwise be overlooked.
There’s also a method developed by a doctor named Gilula that uses three imaginary lines drawn on a front-to-back x-ray of the wrist. These lines trace around certain wrist bones. If these lines look interrupted or ‘off’ in any way, your doctor might suspect a specific type of wrist injury called a perilunate injury.
Speaking of which, the space between certain wrist bones can also tell doctors a lot. For instance, the gap between the ‘scaphoid’ and ‘lunate’ should be less than 3 millimeters. If x-rays show that this gap is wider, it may suggest an injury known as ‘scapholunate dissociation’. This condition can sometimes be confirmed by viewing the wrist from a special angle, called the grip compression view. It can cause the scaphoid bone to turn and show a denser, ring-like image around its edge on x-rays, known as the ‘signet-ring sign’.
If your doctor suspects perilunate dislocations, they’ll look at the side view x-ray. Here, they’ll see the lunate bone is in its normal place, but the ‘capitate’ bone is oddly positioned. Other wrist bones may also show fractures that otherwise go unnoticed.
In case of a lunate dislocation, an x-ray shows the lunate bone has moved from its original spot, although the rest of the bones in your wrist and hand are still well-aligned. This is also referred to as the “spilled teacup” sign. In a different view of the x-ray, doctors may see a triangular appearance, due to the rotation of the lunate. This unique sign is known as the “piece of pie sign.”
Treatment Options for Wrist Dislocation
If a person is suspected to have a condition known as scapholunate dissociation, it means that the two bones in their wrist – the scaphoid and lunate – have moved apart. When this happens, they should have their thumb placed in a specialized type of supportive device known as a “thumb spica”, a “radial gutter”, or a “short arm volar splint”. This helps to secure the thumb in place and prevent further damage.
This condition really needs to be seen by an orthopedist or hand surgeon. That’s because the usual treatment involves pinning the bones back together, either by going in through the skin (“percutaneous pinning”) or by opening up the wrist (“open reduction”). Afterwards, the patient’s wrist is put in a short cast, and the pins are taken out after 8 to 10 weeks. During the recovery, which may last 4 to 6 months, they’ll need to avoid doing any heavy lifting with the affected wrist.
In cases where the lunate bone has moved from its original place, or if surrounding parts of the wrist are at risk, it’s really important to put everything back where it belongs as soon as possible. This helps to take pressure off a major nerve in the wrist (the median nerve) and stops further damage to the cartilage. Assigning one of the orthopedic or hand surgeon specialists as soon as possible is beneficial for a quick recovery.
Often, this type of injury will need what’s called an arthroscopically guided reduction. This is where the surgeon uses a camera to help guide them. The procedure is done by pulling the hand gently upward with a tool called finger traps, while the elbow is bent at a 90-degree angle. The dislocated parts are then moved back into place by extending the wrist, applying some more pulling force, and then finally flexing the wrist. This is followed by applying a “sugar tong splint”, which is a type of support that wraps around the affected arm. Lastly, the affected ligaments around the wrist, which often gets injured during these types of situations, would require surgery to stabilize them; otherwise, more instability could eventually occur. And just like the previous procedure, the patient would need to wear a short arm cast for at least 6 weeks post-surgery.
What else can Wrist Dislocation be?
When a patient comes in with sudden wrist pain, there could be many causes. One potential issue could be a problem with the stability of the small bones in the wrist, often paired with a fracture in one of these bones. The most frequently fractured bone here is the scaphoid bone. Other types of fractures should also be considered, including the most common wrist fracture which affects the radius bone near the wrist. Apart from fractures, wrist sprains – usually involving the external ligaments – should not be ruled out. It is crucial, however, to first rule out any more serious injuries before settling on a diagnosis of a sprain.
What to expect with Wrist Dislocation
The outcome of a wrist dislocation largely depends on several factors. If the dislocation is detected and treated quickly, the patient can expect a generally favorable result. However, if the patient has recurring instability and irregular wrist movement, they run a higher risk of developing arthritis due to injury. Also, those with a chronic condition known as scapholunate dissociation may further develop a more severe condition called scapholunate advanced collapse.
Possible Complications When Diagnosed with Wrist Dislocation
Scapholunate dissociation is the most frequent reason for arthritis in the wrist. If it’s not spotted and treated early, the large bone near the middle of the hand (capitate) can move up and wedge itself between the scaphoid and lunate bones of the wrist. This results in a condition called SLAC wrist, a degenerative disease.
Long-term arthritis in the wrist is a typical complication after serious injuries to the lunate or area around the lunate. Other complications could happen as well such as:
- Constant instability of the wrist bones
- Tendon rupture
- Delayed bone healing
- Insufficient or improper bone healing
- Compression of the median nerve
- Complex regional pain syndrome
- A condition where the lunate bone loses blood supply and dies (avascular necrosis).
Preventing Wrist Dislocation
Wrist dislocations refer to various types of injuries. If the dislocation comes with a broken bone, doctors often treat it immediately with surgery. However, damage to the wrist’s ligaments – the tissues that connect bones – may not always heal completely. This can lead to chronic instability, making your wrist less reliable and increasing your chances of developing arthritis later on. It’s a good idea to see your doctor if your wrist continues to hurt, collapses under pressure, makes a popping or clicking noise, or gets stuck in one position.
