Carpal tunnel syndrome (CTS) is a common condition caused by pressure from a ligament on a nerve in the wrist, leading to pain, numbness, and weakness in the hand. Surgery to cut the ligament is often recommended when non-surgical treatments do not provide sufficient symptom relief, but it is unclear how much of the improvement is due to the surgery itself versus natural recovery or placebo effects.

The FINCATS study will compare standard carpal tunnel surgery with a placebo procedure in which the ligament is not cut. Participants and the healthcare staff caring for them after the procedure will not know which procedure was performed. The study's main question is whether cutting the ligament provides greater symptom relief than a placebo procedure. In addition, eligible patients who are not willing to participate in randomized setting are invited to join a parallel observational group. Participants in this observational group are treated within usual care pathway.

Participants in both the randomized and observational group will be followed for five years to assess symptom improvement, hand function, pain, quality of life, and any side effects. The goal is to provide reliable evidence to help patients and doctors make informed decisions about treatment.

Inclusion Criteria:

• Age 18-75 years
• Clinical manifestations of carpal tunnel syndrome: paresthesia and /or hypoesthesia in the distribution of the median nerve, possibly pain
• Electrodiagnostically (ENMG or ENEG) verified compression of the median nerve at the carpal tunnel in the wrist, performed no more than a year before recruitment.
• Duration of symptoms 3 months or longer
• Patient living independently
• Patient has not responded to the use of a resting splint supporting the wrist, nor to other possible conservative forms of treatment
• Patient able and willing to give consent
• The patient is willing to undergo surgical treatment for carpal tunnel syndrome.
• The patient has access to a device that can be used to complete electronic symptom questionnaires.

Exclusion Criteria:

• Work disability
• Clinical findings of Abductor Pollicis Brevis atrophy
• Symptoms and Electrodiagnostic findings of some other peripheral neural entrapment than carpal tunnel syndrome
• Rheumatoid arthritis or other forms of systemic inflammatory disease
• Diagnosed dementia
• Neurologic disorders affecting the function of the hand
• Other untreated systemic disorders or diseases with poor therapeutic balance: hypertension, epilepsy, pulmonary or cardiac disease, liver or renal insufficiency, diabetes mellitus, hypothyroidism, psychiatric disease
• Other causes of pain and paresthesia in the hand
• Previous trauma of the hand or wrist (e.g. distal radius fracture), which has resulted in compromised hand function
• Previous carpal tunnel release in either hand
• Previous nerve injury to the upper limb or cervical spine

All collected IPD provided that current legislation permits it.

After publication of main results, to be specified later

To be determined

Participants, healthcare professionals other than the treating surgical team, outcome assessors, and investigators will be blinded to treatment allocation.