The median nerve passes through the carpal tunnel in the wrist. The wrist bones (carpals) on one side and the flexor retinaculum on the other form the carpal tunnel. The flexor retinaculum is a thick ligament that crosses over the front of the wrist bones. Pressure on the median nerve can cause carpal tunnel syndrome (CTS). Doctors aren’t always sure what causes the pressure on the median nerve as it passes through the tunnel.
Symptoms of hand and finger pain or numbness and tingling can be treated with surgery. The doctor inserts a thin tube-like tool into the palm side of the wrist. This device is called an endoscope. It’s inserted under the skin and into the carpal tunnel.
Using this tool, the doctor is able to cut the thick ligament where it crosses over the median nerve. Cutting this ligament takes the pressure off the median nerve. Some doctors are concerned that putting the endoscope into the carpal tunnel adds even more pressure against the nerve.
A doctor in Belgium studied 20 middle-aged women with CTS. Measurements of the pressure inside the carpal tunnel were taken before and after the operation. The wrist was placed in several different positions while the pressure was recorded. Pressures were highest with the wrist in extreme positions. The pressure went down after the ligament was cut.
Carpal tunnel release can be done using an endoscope without causing more nerve compression. The pressure of the scope against the nerve isn’t much and it doesn’t last long. Releasing the ligament across the carpal tunnel takes the pressure off the nerve. Most patients get relief from their painful symptoms.
According to the author of this study, measuring the pressure before, during, and after surgery can help doctors. If the pressure is less than 30 mm Hg, then the ligament has been cut. Incomplete release of the ligament may cause symptoms to persist.