Trigger Finger - An Ergonomic Approach

Trigger Finger - An Ergonomic Approach
Trigger Finger (Stenosing Tenosynovitis)

Trigger Finger is named after the position a finger is in when a trigger is pulled – Bent. It can affect all joints in the fingers, and can affect all fingers, including the thumb. Trigger Finger interferes with straightening the finger joint after it is bent.

The joint ‘catches’ in the bent position, and then releases with a snap. In mild cases, the finger may be able to un-catch itself and you may be aware only of the ‘snap’. In most cases, the other hand will have to provide a little force to release the joint. In some cases, the release is painful. In other cases, it isn’t.

Tenosynovitis: An inflammation of the sheath surrounding the tendon.

Stenosing: Narrowing of an anatomical tunnel.

Hand Anatomy

The hand is composed of a complex system of pulleys and levers. Each muscle has to carefully gauge how much tension it’s creates when it contracts, do that just the right amount of bend is achieved at each joint. Finger flexion is controlled by a deep muscle group in the forearm.

Tendons connect the muscles to the different bones. What the muscle moves depends on where the tendon attaches. Since fingers have 3 flexion points, each finger has 6 attachment points for flexion (a right and a left on each joint). Each tendon is wrapped in a slippery coating called the synovium that lets it glide smoothly as it does its job.

Tendons are kept from slipping around the hand when muscle tension changes, by tendon sheaths that act as pulleys, guiding the tendon to its attachment. As the muscle tightens and relaxes the tendon slides through the sheaths. Each tendon has 5 sheath attachments. The first one is in the palm of the hand.

What Causes the Catch?

There are two things that can contribute to Trigger Finger.
1. The tendon can develop a ‘bump’ or nodule that is larger than the sheath can easily accommodate. The tendon to glide is impeded..
2. The Tendon Sheath may thicken, narrowing the canal. There is less room for the tendon and little imperfections can cause snags.
It is unclear to me why the ‘catch’ would happen only when the finger tries to straighten, but this seems to be the case.

Etiology (Why did this happen?)

There are different theories of causation, none of which are strongly supported by research, but ALL of which have research that supports them.

• Be Female
More women than men get trigger finger.
• Be at least 40 years old
Trigger finger usually appears between the ages of 40 and 60, but can be as late as 90.
• Repetitive Activity
Some studies relate trigger finger to repetitive activities – not necessarily a long history of repetitive activities, but it appears after an intense period of such activity.
• Genetics
There is frequently a family history of trigger finger.
• Have Diabetes or Rheumatoid Arthritis
Trigger finger is more common among those that have rheumatoid arthritis or diabetes than among the population as a whole.

Recent research (2009, 2010) shows some indication that there is a bio-chemical component to trigger finger. Treatments are being developed addressing this, but it may be years before they are available.

If there’s no Pain, Why Worry?

By itself, trigger finger is not dangerous.

There are some safety issues with trigger finger. Essentially, with trigger finger you may grab something and then NOT be able to let go of it. If what you grab is sharp or hot or too heavy, or you are holding the trigger of an electrical device, or your other hand is involved and can’t help the finger let go, this may be a problem.
• Catching or popping sensation in your finger or thumb joints when you try to straighten your digit
• A lump or swelling in you palm near the finger that catches (this may be tender to the touch)
• Pain when bending or straightening your finger.
• Generally, symptoms are worse in the morning.
• When the tendon releases, the sensation may be mild or may be so bad it feels like the finger is dislocating.
In very severe cases, the finger cannot be straightened. It is not unusual to have more than one finger affected, or to have the same symptoms in each hand.

If you think you have trigger finger, it’s best to get a medical diagnosis. There are other conditions that may mimic trigger finger in the mild stage.

Examination by a doctor will generally consist of a few questions and examining your hand. Once you have a diagnosis, you can discuss treatment options. For mild cases, resting your fingers and taking mild analgesics will help.

What YOU can do
• Use a wireless ergonomic mouse that fits your hand (see articles on mouses)
• Relax your hands on the mouse and keyboard. Change your mouse grip.
• Use wide handled tools – this takes some getting used to. It forces more relaxation in the fingers. These should include tools in the kitchen, garage, garden, everywhere. You have the same hands wherever you go.
• Pad the handles on the tools you have (see the foam adapters below).
• Use wider grip pens and pencils (see articles on handwriting)
• Use a textured Steering Wheel pad in your car. These allow a looser grip on the wheel, even in turning and emergency situation.

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Mousing Tips for Common Mouse Injuries
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