Carpal Tunnel Syndrome
Treatment of carpal tunnel syndrome is nowadays the most common type of hand surgical procedure. The carpal tunnel is a bony canal lined with soft tissue which is directly connected to the distal forearm. The concave arch of the carpal bones creates the floor and lateral walls. The flexor retinaculum creates the roof (known as the carpal roof or carpal ligament) and is fixed to the bony prominences: proximally to the scaphoid tubercle and pisiform bone, and distally to the tubercle of trapezium and the hamate hook. All the finger flexor tendons (FPL, FDS II-V and FDP II-V), the synovial tissue, and the medial nerve run through the carpal canal.
The flexible synovial tissue allows for longitudinal adjustment of the nerves. Normally, the terminal branches of the nerve spread outward after exiting the carpal canal. Anatomical variations of the median nerve and its branch are common within the carpal canal and are of high relevance for hand surgeons – and therefore also for the patient – during operations. Nerve compression damage to the median nerve in the carpal canal is the most common type of nerve compression syndrome affecting a peripheral nerve.
In Germany approx. 300,000 carpal tunnel release procedures are carried out each year, 90% on an outpatient basis. Approximately 2-5% of the population suffers from the condition, and in 50% of cases the cause in unknown (idiopathic). Possible causes for increased compression in the carpal canal include bone-related changes (hereditary or as a result of a fracture), systemic disease such as diabetes, chronic polyarthritis, renal insufficiency, or hormonal imbalances stemming, for example, from hypothyroidism and pregnancy. Very rarely, ganglia or tumours originating from the carpal bone can trigger carpal tunnel syndrome. Bilateral affliction is evident in 50% of cases, and a higher prevalence of the condition is documented in patients between 40 and 60 years of age. Women are significantly more likely to be affected than men. Nerve compression in the carpal canal leads to swelling of the nerve with thickening of the neural tissue and, finally, nerve damage.
Diagnoses and Examination
The main symptom is nocturnal paresthesia, with the majority of patients reporting a tingling sensation, but also pain in the fingertips, thumb, index finger and middle finger (no affection of the little finger) especially at night. The ring finger is numb or with tingling on the middle finger side. These symptoms can also manifest themselves during the day during activities such as riding a bike, using the telephone, or when driving. Changing position and shaking the hand can help relieve the symptoms, and cooling the hand can also be effective. Many patients suffer a reduction in sleep quality. If carpal tunnel syndrome remains untreated, in the long term, this will lead to an advanced stage with thenar muscle atrophy and a notable reduction in strength when grasping.
During the examination by the hand surgeon, the Hoffmann-Tinel sign is positive if tapping the median nerve at the entry to the carpal canal triggers paresthesia in the area supplied by the nerve. Another common examination technique is the Phalen’s wrist flexion test. By fully flexing their wrists, the patient increases pressure on the median nerve in the carpal canal and, if nerve damage is present, this triggers sensory disturbances in the fingers and thumb. If the results of both these tests are positive, then it is highly likely that the patient is suffering from carpal tunnel syndrome. To obtain additional information and to assess the severity of the nerve damage, electrophysiological testing of the median nerve by an experienced neurologist is recommended. This test determines the nerve conduction velocity, which in these cases is normally reduced.
Ultrasound has established itself as an effective diagnostic imaging tool in recent years. For example, swelling and narrowing of the nerve at the entry to the carpal tunnel can be displayed, and the inflammation-related thickening of the flexor tendon synovial tissue (synovitis) can be identified as a possible cause of nerve compression.
Conservative treatment is possible in the early stages of the disease, for example when the only symptoms are sensory disturbances. Wearing a wrist splint at night, as prescribed by a doctor, will keep the wrist joint in a neutral position (0 degrees) and can have a positive effect. Also, cortisone injection at the entry to the carpal tunnel combined with a local anaesthetic can help relieve the median nerve syndrome. However, the effects are often only temporary.
After the diagnosis has been confirmed, operative treatment is indicated, ideally by a hand surgeon. The standard operative procedure is open carpal tunnel release but there is also the option of endoscopic carpal tunnel release. The intervention is carried out either using local anaesthesia (known as plexus anaesthesia) or general anaesthesia and the use of magnifying spectacles by the surgeon. In recent years, open surgery with the administration of adrenaline to constrict the blood vessels without the use of an upper arm tourniquet has become established. The operation takes between 10 and 15 minutes and can be carried out either on an outpatient or inpatient basis (known as a Wide Awake or WALANT procedure). The practice founder, Prof. Sauerbier established the use of the procedure in Germany in 2007 and has extensive surgical experience with carpal tunnel syndrome extending well into the four-figure range.
Immobilisation of the hand following the operation is not always necessary; we recommend the use of cotton bandaging for 2 to 5 days. Finger exercises with making a fist and stretching begin early in the postoperative phase under the supervision of a hand therapist, combined with exercising of the wrist. To aid the scar healing process, the application of silicone scar gel can be beneficial following the removal of the suture material after 12 to 24 days. On average, the patient will be unable to work for 2 to 5 weeks. Full stressing of the hand should begin after 1 to 2 months, depending on the individual scar development in each case. If the operation takes place within a reasonable period of time following the development of nerve compression, then a complete restoration of hand sensitivity can be expected.