What is Hamate Fractures?
Hamate fractures, which affect a triangular-shaped bone in the wrist, are often overlooked and mistaken for simple wrist sprains. A delay in diagnosis is common, as these fractures are both rare and hard to identify. The hamate bone forms part of the base of the wrist (the distal carpal row), connecting to several bones.
The unique shape and position of the hamate mean that fractures to it can generally be sorted into two groups: fractures of the ‘hook’ (a small protrusion on the bone), and fractures to the main body of the bone. In more detail, this classification includes:
- Type 1: Fracture of the hook of the hamate
- Type 2: Fracture of the main body of the hamate, which could either be:
- 2a: A front-to-back (coronal) fracture
- 2b: A side-to-side (transverse) fracture
Fractures in the hook of the hamate can cause injury to the ulnar artery and ulnar nerve, while fractures of the main body of the bone can be associated with additional fractures or dislocations involving the fourth and fifth metacarpal bones or a severe wrist injury known as greater arc perilunate fracture-dislocation.
What Causes Hamate Fractures?
A hamate hook fracture often happens in sports that require a strong grip, like tennis, baseball, and golf. Fractures in the body of the hamate are usually caused by more intense incidents like a punch. These types of fractures may also happen at the same time as other wrist and hand injuries. However, fractures in the body of the hamate are less common.
Risk Factors and Frequency for Hamate Fractures
Hamate fractures, which only make up 2 to 4% of all carpal (wrist) fractures, are not very common. They occur in the distal row of the wrist, which is less prone to fractures than the first row. These types of fractures typically happen to younger, active individuals and are rare in children.
Signs and Symptoms of Hamate Fractures
If a fracture is suspected in the hamate, which is a bone in your wrist, various tests can help verify this. While some of the symptoms can be hard to pinpoint, this type of injury should be considered, particularly for young athletes who have chronic wrist pain. The hook of the hamate fracture is often accompanied by consistent wrist pain, tenderness and sharp pain in the hand’s heel, numbness along both the ring and pinky finger, and sometimes weakened grip strength. Pain can also occur when grasping objects. You might even notice pain in the ring and pinky finger bones, which can be an indirect sign of a hamate fracture.
Symptoms to be aware of include:
- Chronic pain along the wrist
- Tenderness over the area on the palm side of your hand below your little finger
- Numbness along the ring and small finger
- Swelling and tenderness over the back of the wrist on the side of your little finger
- Weakened grip strength
- Pain when you grasp objects
- Pain in the fourth and fifth finger bones
- Active flexion of ring and small finger causes pain (Pull test)
In the case of a hamate body fracture, swelling, tenderness and pain on the wrist’s outer side are common symptoms. This injury often occurs with high energy trauma and can result in other associated injuries. Something to look out for includes potential deformation of the fourth and fifth finger bones of the hand, which could indicate an indirect sign of a hamate fracture.
Testing for Hamate Fractures
When a doctor suspects a wrist injury, they typically start with x-rays taken from straight-on (anteroposterior) and sideways (lateral) views. One thing they look for is the “ring sign,” which occurs where the hook and body of a bone called the hamate overlap. This is normal, but if it gets disrupted, it could mean the hook is fractured. Sometimes, the base of the hook loses some of its normal density, or the hook might even be missing.
Body fractures, on the other hand, usually show up on either a sideways x-ray or a CT (computed tomography) scan, which provides more detailed images. However, conventional x-rays have a high rate of providing false negatives, and only detects about 70% of injuries. As a result, doctors often supplement these with additional imaging views, such as a carpal tunnel projection or a radially deviated semi-supine oblique projection.
A CT scan is often necessary for a proper diagnosis, as it’s helpful in detecting every injury (100% sensitivity). But sometimes, particularly for chronic conditions like avascular necrosis (a disease causing bone death due to lack of blood supply), an MRI (magnetic resonance imaging) scan might be needed.
If a doctor determines that surgery is necessary, they’ll usually order routine blood tests. The need for these will depend on the patient’s history and physical exam results. It’s all part of getting a thorough understanding of how complex the surgery might be.
Treatment Options for Hamate Fractures
Surgery is typically performed for certain conditions including displaced fractures, non-healing fractures, various nerve and artery compressions, tendon rupture, and dislocation of the metacarpals (bones in the hand).
The following actions often need to be taken if you have a hook fracture (a specific kind of hand fracture):
- For minor, non-displaced fractures: The usual treatment is to immobilize the hand using an ulnar gutter cast (a specific type of cast that immobilizes the wrist and the fourth and fifth fingers) for about six weeks. However, there’s an ongoing debate about whether immediate surgery could be more beneficial in these instances. Athletes, for example, might prefer to undergo surgery right away because it could allow them to return to their sports activities in about three months.
- For major, displaced fractures: Getting rid of the broken bone fragment is the most commonly recommended procedure. Another accepted treatment is open reduction and internal fixation, a method that typically involves using screws or thin wires to secure the bone fragments. Both procedures have shown to be similarly effective.
- For unhealed fractures causing chronic pain: This condition usually requires an operation to secure the fracture with a pin and a bone graft (a procedure where surgeons place new bone around the area of the fracture to help it heal).
For body fractures (fractures across the main part of the hand):
- For minor, non-displaced fractures: Immobilizing the hand with a cast for about six weeks is usually recommended.
- For major, displaced fractures: Open reduction and internal fixation are typically done, where orthopedic surgeons use specific devices like fine wires, a grid plate, or compression screws without heads to fix the fracture.
Surgeons should also be aware of the following considerations when operating:
- The motor branch of the ulnar nerve, important for hand movements, should be carefully identified and moved aside before any excision (removal) or drilling.
- After removing the fracture fragment, the protective layer covering the bone (known as the periosteum) should be carefully closed over the remaining base of the bone. This step is essential for protecting the ulnar nerve and tendons (tissues that connect muscles to bones).
What else can Hamate Fractures be?
When a person experiences pain or discomfort in their wrist, it could be a result of different conditions. Tendinitis in the ulna (one of the main bones in the forearm) and injuries to the triangular fibrocartilage complex, a small structure in the wrist that contributes to hand and wrist stability, are frequently mistaken for other conditions.
Only a small number of people (1 to 2%) with a broken radius (a bone in the forearm) also have a fractured hamate. The hamate is one of the small bones in the wrist.
The following conditions also need to be considered when diagnosing wrist pain:
- A bipartite hamate, where the hamate bone is made up of two parts instead of one
- A scaphoid fracture, which is a break in one of the small bones of the wrist
- A capitate fracture, another kind of break in a small wrist bone
- A triquetrum fracture, yet another type of break in a small wrist bone
- A pisiform fracture, a break in the small, pea-shaped bone in the wrist
- Soft tissue injuries, such as damage to the ligaments – these hold the bones together and may be injured without any broken bones
- Dislocations of the small bones in the wrist known as the carpal bones
It’s crucial for medical professionals to properly diagnose these conditions in order to provide the most effective treatment.
What to expect with Hamate Fractures
When treated non-surgically, fractures usually take about 8 weeks to heal. However, for non-displaced hook fractures, the treatment isn’t always successful, with a 50% chance that the bone doesn’t heal properly. If the bone doesn’t heal and causes symptoms, then further surgery may be necessary.
Surgical treatments, whether it involves removing a bone fragment or using a procedure to fix broken bones (ORIF), offer the benefit of a faster recovery. This means that patients can return to their daily routine and sporting activities more quickly.
Possible Complications When Diagnosed with Hamate Fractures
- Nonunion (failure of broken bone to heal)
- Posttraumatic arthritis (arthritis caused by injury)
- Avascular necrosis in proximal pole (death of bone tissue due to lack of blood supply)
- Ulnar nerve compression (pressure on the nerve in Guyon’s canal)
- Carpal tunnel syndrome (pressure on the nerve in the wrist)
- Flexor digitorum profundus tendon rupture (tendon tear in fingers)
- Ulnar artery thrombosis (blood clot in the ulnar artery, referred to as hypothenar hammer syndrome)
- Ulnar artery compression (pressure on the ulnar artery)
- Residual instability of fourth and/or fifth metacarpals (lingering instability in the long bones of the hand)
Recovery from Hamate Fractures
Physical therapy is vital. For non-surgical treatments, occupational therapy should start immediately once the cast is removed. However, if the treatment involves a surgery known as ORIF (Open Reduction and Internal Fixation), therapy should only begin after immobilizing the area for 3 weeks. Those who undergo hook excisions can start therapy earlier. The entire rehabilitation process should typically last between 4 to 6 weeks.
Preventing Hamate Fractures
Patients should know that hamate fractures, or breaks in a small bone in the wrist, often lead to long-term pain and a condition called osteoarthritis, which causes joint discomfort and stiffness. It’s also recommended for patients who smoke to quit, as this can help the bone heal more effectively.
