Carpal Tunnel Decompression Information Sheet
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Definition
Carpal tunnel syndrome is where the nerve that runs through the wrist to the hand is compressed. The nerve is called the median nerve and this supplies the muscles of the thumb and finger grip. The nerve also supplies sensation to the outside or lateral part of the palm. The nerve runs under a ligament called the flexor retinaculum.
The flexor retinaculum forms the roof of the tunnel and when this becomes thickened, this causes pressure on the underlying nerve, causing pain, tingling, numbness and weakness in the hand.
A thickened flexor retinaculum causing a narrowed carpal tunnel are commonly seen in people who use their hands for heavy manual work, especially builders, and people using hands for hobby craft such as knitting. Other causes are hormone disorders, such as acromegaly and diabetes. Carpal tunnel syndrome may also occur during pregnancy, and can infrequently occur after trauma to the wrist or hand.
Indications
When the median nerve becomes compressed in the carpal tunnel, the patient experiences weakness of the thumb and finger grip muscles. There is numbness and pain in the fingers, worse at night. The patient has problems holding objects and frequently drops writing instruments, cups and other objects.
If the pain and numbness in the hand is worsening and has not responded to a hand splint or local steroid injection, operative intervention is indicated.
Carpal tunnel syndrome is diagnosed by special electrophysiological tests, called nerve conduction studies. A nerve impulse is measured across the nerve running from the shoulder to the fingers. The impulses are slowed and reduced as they cross through a narrowed carpal tunnel.
Often patients have symptoms in both hands, with the dominant hand giving the worse symptoms.
A Neurologist performs the nerve conduction studies, and will inform the Neurosurgeon of your test results.
Success of the operation
80 - 90% success rate for significant improvement in strength, sensation and pain are achieved following carpal tunnel decompression. No change in symptoms (no better or worse) occurs in 10% of patients.
Risks of the operation
The total risk of the carpal tunnel decompression is approximately 2% or 1: 50. This comprises of:
- Infection, which is usually superficial skin infection requiring oral antibiotics
- Bleeding with bruising in the palm
- Damage to the median nerve with weakness of the thumb muscle
- Ongoing pain along the site of the incision
- Failure to improve the symptoms of pain, weakness, numbness and tingling.
If your symptoms do not improve following the operation, you will be carefully reviewed for approximately three months after the operation. You may require repeat nerve conduction studies to assess if the nerve has any residual compression.
It is rare for patients to require repeat decompression to satisfactorily relieve pressure on the underlying median nerve to improve symptoms.
Before surgery
Inform Dr Cochrane about any medical conditions or previous operations.
If you have a medical condition such as diabetes, heart problems, high blood pressure or asthma, Dr Cochrane may arrange for a specialist physician to see you for pre operative assessment and look after you following the operation.
Inform Dr Cochrane of medication that you are taking and/or allergies to medications.
Stop Warfarin 5 days prior to surgery, and stop Aspirin/Plavix 10 days prior to surgery as these medications thin the blood.
Operation
Carpal tunnel decompression or release of the nerve can be performed under local or general anesthetic. You will be admitted on the day of the operation and go home on the same day. This is known as a day procedure.
You must not drink or eat for six hours before the operation. You can eat and drink after the operation.
You will be lying on your back on the operating table, with your hand outstretched and resting on a special arm table.
Local anesthetic will be injected into the palm, along where the skin incision will be made. Your hand and arm will then be washed with antiseptic solution and the arm covered with drapes.
Dr Cochrane will then make an incision in the midline of the palm of your hand from the wrist crease for 2.5cms. The fat below the skin is separated and then the thickened flexor retinaculum is carefully opened. The flexor retinaculum is fully decompressed along its entire length to totally free the compressed median nerve.
All small bleeding points are carefully coagulated.
The wound is washed and the skin carefully sutured with fine interrupted nylon sutures. A wound dressing then covers the sutured wound. A cottonwool pad then covers the wound and palm and a crepe bandage is wrapped around the wrist and hand.
You will then be taken to the recovery room.
After surgery
Your hand will be elevated on a pillow in the recovery room. The nurses will check your finger sensation and movements along with your breathing, blood pressure and heart rate.
You will only require tablets by mouth for pain, usually Panadeine Forte.
You will be provided with a small arm sling (called a "collar and cuff") to keep your hand elevated.
You will be able to go home later in the day after having a drink and light food.
It is essential that a relative or friend collect you from the hospital and drive you home.
Keep your hand elevated above your heart for 24 hours following the operation to reduce the risk of any bleeding or bruising. The crepe bandage can be removed three days after the operation. Keep your hand clean and avoid any pressure or blows to the palm. Leave the skin dressing on until the sutures are removed 10 days after the operation, either by the District Nurse or your GP.
Dr Cochrane will review you post operatively at his rooms 2 - 3 weeks after the operation to assess your progress.
Return to work timing can then be discussed.