wrist dislocation

Tuesday, September 12, 2017

One would think that some injuries are easier to diagnose than others. Broken bones and dislocated joints seem like prime examples of no-brainer injuries. There should be some major deformity or at least the x-rays would show the damage. One would think, wouldn’t one. But some parts of the body hide damage well and that brings us to the sad injury of David Johnson, running back for the Arizona Cardinals.

In the third quarter of the season opener, Mr. Johnson was tackled and landed on an outstretched hand. He immediately grabbed his wrist and went to the sideline. Initial exam by the medical staff allowed him to return to the game, but on the next play, he had trouble hanging onto the ball, fumbled it and was done for the day. X-rays were done and the diagnosis was a sprained wrist. Only hours later was the final diagnosis made of a dislocated wrist. Welcome to the world of medical uncertainty.

The wrist is a complicated joint. It is made up of the radius and ulna, (the bones of the forearm) and eight carpal bones aligned in two rows. Most doctors aside from orthopedic surgeons cannot name these bones without looking up an anatomy diagram.

Bones of the Wrist

They are held in place by a complex system of ligaments: interosseous (between the bones), volar (palm) side and the dorsal (back). The dorsal ligaments are weaker than the volar, so falling on an outstretched hand can potentially cause the backside of the wrist to collapse, sometimes fracturing the scaphoid bone and sometimes dislocating either the lunate by itself or the capitate bone from where it rests on the lunate. The specific type of dislocation isn’t as important as appreciating that even with bones out of place, the diagnosis can be easily missed on physical exam and sometimes on plain x-ray.

Scaphoid Fracture

 

Wrist Dislocations

People fall on their hands all the time and most often, there is little damage done, except for a skinned palm and bruised pride. But if there is greater force applied like in football or a fall from height, major damage can occur. However, the initial exam can be pretty unexciting. There may perhaps be a little swelling and tenderness on the back of the wrist and perhaps a little tingling of the index and middle fingers if the median nerve is irritated. Otherwise, people may ignore the injury and seek medical care only after developing chronic wrist pain and weakness.

The problem arises when plain x-rays are normal or perhaps misinterpreted, since evidence for a scaphoid fracture or dislocation may be very subtle or not there at all. Based on mechanism of injury, physical exam and care provider gestalt, the diagnosis may be suspected and then confirmed by CT scan or MRI.

If the diagnosis is made in the acute phase, attempts at reducing the dislocation can be made at the bedside, but often these fail and the patient is taken to the operating room where an open reduction and pinning of the bones occurs. Fortunately, there is a pretty big window of a couple of weeks to make the diagnosis and treat the injury. For many, return to play occurs relatively quickly, once all is healed, but that time frame is measured in months. However, there are complications to this injury and they include, decreased wrist range of motion, decreased power in the hand, carpal tunnel syndrome from medical nerve inflammation and failure of the scaphoid or capitate bone to heal (avascular necrosis).

From media reports, it’s not quite clear what happened to Mr. Johnson. A wrist dislocation is a non-specific term and may refer to a combination of many injuries or just an isolated one. It is reasonable for him to seek second opinions regarding treatment, but this is bread and butter work for most orthopedic surgeons, especially those who specialize in hand injuries. The big deal is getting the diagnosis made in the first place.

 

Images: learningradiography.com

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carpal bones get no respect

Monday, September 9, 2013

When it comes to anatomy, the carpal bones are the Rodney Dangerfield of the skeleton. The two rows of bones that connect the wrist to the hand increase the ability of the wrist to move and rotate but are so forgotten that most doctors can’t remember their names or identify the individual bones on x-ray.  So it comes as no surprise that the injury sustained by New England Patriot running back Shane Vereen was described only as a broken small bone in his wrist, even though the unnamed culprit required surgery.

 

carpal

 

Fractures of the carpal bones are relatively frequent, but since the scaphoid bone (sometimes called the navicluar) accounts for 70% of fractures and the triquetrum another 14%, the other bones get forgotten. However, damage to the lunate and hamate can have significant complications and the diagnosis is often missed immediately after injury. However, the diagnosis can be hinted at based upon the mechanism of injury and even if x-rays are negative, a high index of suspicion for fracture is often maintained by the doctor.

The mechanism of injury for a scaphoid fracture is a fall on an outstretched hand. The scaphoid is located at the base of the thumb. Extend the thumb like an aggressive hitch hiker and two tendons frame the snuffbox, a sunken area so named because English gentlemen would use it to hold the snuff they sniffed. If broken, the area swells and is painful to palpate or feel. X-rays may miss a fracture of this bone (remember that fracture, break and crack all mean the same thing) and if clinically indicated, the doctor may place the wrist in a splint and re x-ray it in a week to look for changes associated with a healing fracture. Sometimes a CT scan needs to be done to find the fracture. Scaphoid fractures tend not to heal well, a design flaw provides the bone poor blood supply and surgery is sometimes required.

The reverse mechanism, falling on a curled up wrist will cause the triquetrum to break. This causes swelling on the back of the hand and x-rays usually show a small fleck of bone in the swollen area. These chip fractures heal well with a little rest. If the body of the triquetrum is damaged, surgery may be required to pin the bone and stabilize it.

The hamate gets no love. It is located between the little finger of the hand and the ulna of the forearm. Fractures occur because of a fall or direct blow or crush injury, causing immediate pain but occasionally patients ignore the initial injury and present late because of decreased grip strength. The initial complication is ulnar nerve damage because of its close location to the hamate. The nerve can stop working, causing the ring and little fingers to become numb, because bone fragments touch it or because swelling associated with the broken bone causes irritation. The later complication is non-union, the same as with scaphoid fractures, meaning that the bone fragments fail to heal….poor design, poor blood flow to the bone. Historically, a hamate fracture was treated by casting and time, but more than half would fail to heal. Now, surgery is often a first consideration.

The lunate is the bone that butts up against the radius and is an integral part of the wrist joint. It can be broken by one direct blow or by repetitive small blows that cause microfractures and eventually, collapse of the bone. This can lead to significant arthritis and may need surgery to repair, replace or fuse the joint. A tear of the ligament that holds together the scaphoid and the lunate in their relationship to the wrist can be torn with a direct blow and can be suspected by subtle changes in an x-ray only if the doctor has that index of suspicion. CT and MRI can help sort out the anatomy and injury.

If this were a game of Clue, we could take an educated guess about Mr. Verren’s wrist injury: a small bone, some nerve involvement, return to play in many weeks. The answer: The hook of the hamate fracture with ulnar nerve impingement, surgery to remove the fragment of broken bone, and 6-8 weeks of physical therapy and rehab to regain range of motion, power and endurance in the hand. Unfortunately, for Mr. Vereen, the game is real and his commitment to rehabilitation is real, even if the bone he broke gets no respect.

 

 

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