Sometimes the transverse carpal ligament grows back together with less space than before surgery, due to the formation of scar tissue. In this case, CTS symptoms get much worse after surgery than they were before the procedure.
All in all, patients surveys suggest that surgery is successful 50% to 60% of the time. The symptoms actually get worse for about 5% to 8% of people after Carpal Tunnel Surgery than they were before surgery.
This is one of the reasons why surgery is considered a last resort for treating Carpal Tunnel Syndrome.
Also, even when surgery is successful, the symptoms come back for over two thirds of patients within 2 to 7 years. Repeat Surgical procedures have even a lower success rate due to increased scar tissue and damage to the structures around the Carpal Tunnel in the first surgery.