Carpal tunnel syndrome (CTS) is a phenomenon that occurs due to impingement of the median nerve at the wrist. It usually presents as numbness, tingling, and/or pain in the hand involving the thumb, index, and middle fingers. It commonly starts as nighttime numbness and tingling that awakens the patient and it can progress to being painful throughout the day. As it worsens in severity, it can produce weakness of the hand and loss of dexterity as well as radicular pain up the arm proximally toward the shoulder. There are several risk factors including repetitive use of the hands, such as with manual labor jobs, as well as obesity and rheumatologic conditions.
CTS is the most common compression neuropathy affecting 1.8–3.6% of the general population and up to 7% of manual laborers in the United States. Over 500,000 carpal tunnel releases (CTRs) are performed annually in the United States for definitive treatment of severe or refractory CTS. Multiple CTR techniques exist with one common goal—cut (ie, release) the transverse carpal ligament (TCL). Releasing the TCL reduces pressure within the carpal tunnel and, thereby, resolves the compression of the median nerve allowing improvement in associated symptoms.
For many years, the gold standard technique was open CTR (OCTR). OCTR is safe and effective but involves a relatively large incision measuring ~2 inches at the base of the palm. The skin of the palm is thick and takes weeks to months to heal, so patients are often out of work and activity for up to 6–8 weeks post-OCTR. Therefore, the mini-open (m-OCTR) technique has become very popular because the incision size is reduced to ~1 inch. This reduces the size of the scar and healing times slightly, but patients are still restricted in activity for at least 4–6 weeks. Endoscopic CTR (ECTR) is an alternative option that involves two smaller ~0.5-inch incisions but has been associated with a higher risk of transient postoperative nerve symptoms and intraoperative neurovascular injury.
Advances in ultrasound (US) technology and training over the past 20 years have catapulted US-guided procedures into realms most never believed possible. Many current US machines provide extremely high-resolution imaging, allowing providers to confidently perform advanced US-guided procedures in a safe and effective manner. Amongst the procedures being successfully implemented into clinical practices across the country is CTR with US guidance.
CTR with US guidance involves making a very small, ~4 mm, incision in the distal forearm as opposed to incising the skin of the palm. The distal forearm skin is relatively thin and heals rapidly, enabling patients to return to full activity within 1 week. Prior to performing CTR with US guidance, the patient is scanned to ensure adequate visualization of major anatomic structures including the:
- Median nerve
- Palmar cutaneous branch
- Thenar motor branch
- 3rd common palmar digital nerve
- Osseous boundaries of the carpal tunnel (scaphoid, pisiform, trapezium, hook of hamate)
- Ulnar vessels within Guyon’s canal
- Transverse safe zone (TSZ) between the ulnar aspect of the median nerve and the radial aspect of the ulnar vessels or hook of the hamate, whichever lies more radial
- Distal transverse carpal ligament (TCL)
- Superficial palmar arterial arch (including Doppler)
If there are no contraindications to undergoing CTR with US guidance, then the procedure may be performed in either an outpatient clinic or an ambulatory surgical center.
CTR with US guidance is usually performed under local anesthetic. The patient is positioned supine with the arm abducted 90 degrees and the wrist slightly extended. Using a #15 blade scalpel, a ~4-mm incision is made at the level of the proximal wrist crease, penetrating the antebrachial fascia. The surgical device is then advanced under direct US visualization into the carpal tunnel, passing it between the hamate and median nerve within the TSZ, similar to ECTR. The distal tip is advanced such that the blade, when activated, will engage the distal TCL. The position of the device relative to the TSZ and surrounding neurovascular structures is confirmed with US. Using the lever handle, balloons are inflated to increase the TSZ. Next, the cutting knife is deployed and advanced in a retrograde fashion using the thumb slide. The TCL is cut distal to proximal using continuous US visualization. Following TCL transection, the device is removed and a sterile dressing is applied.
Following the procedure, Tylenol and/or NSAIDs is sufficient for pain control. No splinting, occupational therapy, or opioids are required. Patients may begin immediate wrist and hand motion and resume normal activities as tolerated. The only restriction is no lifting, pushing, or pulling greater than 10 pounds with the surgical hand for 1 week. This means that those with desk jobs may return to work the next day; manual laborers may return in 1 week.
In summary, various CTR techniques exist. Although all techniques have good outcomes at 3 months and beyond, the immediate post-op recovery timeline favors the US-guidance technique. The early success of CTR with US guidance being implemented in clinics across the country is exciting for the field of interventional musculoskeletal ultrasound. The sky is the limit!
Brett J. Kindle, MD, CAQSM, RMSK, is a sports medicine specialist at Andrews Institute for Orthopaedics and Sports Medicine, as well as the Medical Director of EXOS-Florida, the Associate Program Director for Andrews Institute Primary Care Sports Medicine Fellowship, and a Team Physician for Pensacola Blue Wahoos.