Carpal tunnel – Ultrasound-Assisted treatment

Definition of carpal tunnel syndrome

Carpal tunnel syndrome is pain in the median nerve area the wrist caused by increased pressure in the carpal tunnel. The carpal tunnel is the anatomical area around the anterior section of the wrist located between the forearm and the hand. All the fingers' tendons course through this cavity closed by the anterior annular ligament (also named flexor retinaculum). Excess pressure in this area results in predominant pain in the nerve with tingling (dysesthesia) in the fingers, often at night.

Video of ultrasound-assisted treatment for carpal tunnel syndrome :  :

Ultrasound-assisted hand surgery video showing an operation on the carpal tunnel / Toulouse Specialist

 

Ultrasound diagnosis of carpal tunnel syndrome

The diagnosis for carpal tunnel syndrome is primarily clinical, and will allow the hand surgeon, who is very familiar with this pathology, to orient the diagnosis.

The test required is usually an electromyogram. However,  an ultrasound of the median nerve, performed by the hand surgeon, will help diagnosis.

The ultrasound of the carpal tunnel can reveal poor or non-existent nerve mobility; which, although useful ; is difficult to quantify. Indeed, transverse ultrasound imaging of the carpal tunnel shows that the median nerve is usually highly mobile when the patient moves his or her fingers. But this mobility of the median nerve diminishes or even disappears in carpal tunnel syndrome.

The median nerve can also lose its normal echogenicity, becoming more hypoechogenic and oedematiated (swollen).

On longitudinal sonograms, the median nerve may also have an hourglass-shaped aspect with a squashed section located next to the annular ligament corresponding to a reduced caliber.

The best sonographic sign is swelling of the median nerve in the carpal tunnel that can be analyzed by measuring its cross-sectional area. As a reference, it is possible to compare the area of the nerve inside the carpal tunnel with its area outside the carpal tunnel, next to the pronator quadratus. Comparing these two areas makes it possible to have a quantifiable diagnostic parameter that helps diagnosis.

Longitudinal view of median nerve at carpal tunnel just before surgeryTransverse view of carpal tunnel

 

Ultrasound-guided carpal tunnel surgery

In early forms of carpal tunnel, an ultrasound-guided injection in the median nerve at the carpal tunnel is possible, which can significantly relieve the discomfort.

In more severe or injection-resistant forms, ultrasound-assisted carpal tunnel surgery may be considered.

The ultrasound-assisted carpal tunnel release procedure is performed under  under local anaesthesia, without tourniquet. The patient is in the beach chair position, with the base of the hand numbed.

Sectioning of annular ligament under ultrasound monitoring

The sonogram makes it possible to evaluate the specificities of each patient's anatomy and mark the important anatomical elements. A diagnostic ultrasound thus becomes systematic before carpal tunnel surgery.

A 4-mm surgical incision is carried out at the wrist's flexion crease. A specific blade is introduced and advanced to the proximal part of the carpal tunnel at the Nakamichi area.

Under continuous in-plane sonographic monitoring, the flexor retinaculum is entirely sectioned from proximal to distal, the palmar arch is easily identified and preserved. In addition to ultrasound monitoring, a distinctive squeaking noise can be heard when sectioning the retinaculum. The wound is minimal, and no stitch ne  and no stitch will be required. A simple dressing is applied to the wrist.

Ultrasound-guided carpal tunnel surgery, pre-sectioning evaluationUltrasound-guided carpal tunnel surgery, sectioning the retinaculum

 

Recovery after ultrasound-assisted carpal tunnel surgery

In recovery from ultrasound-guided carpal tunnel surgery, a dressing is applied to the wrist and will be kept for 5 days. The hand can be used immediately after surgery for all daily activities, but more demanding activities will remain painful and difficult until the anterior annular ligament has healed.

It usually takes from 2 to 3 weeks to be able to drive again.

The wrist's dressing will be removed after 2 days and the patient can use his or her hand normally for all gentle activities, including self-care.

A few weeks will be needed for full range of motion to be restored. For several months, pain will be felt in the heel of the hand when making more demanding movements. The hand's full strength is restored from 3 to 4 months after ultrasound-assisted surgery.

Ultrasound-guided carpal tunnel surgery, skin incision

 

In some instances, this ultrasound-assisted carpal tunnel surgery can be associated with ultrasound-assisted trigger finger surgery..

Find out more about complications after ultrasound-assisted surgery on De Quervain's  tenosynovitis