A clinical study was conducted in a tertiary hospital in Beijing, China, on 34 hands of 20 patients to verify the feasibility of the TCTR surgical procedure. The cases are summarized in Table 1. All patients of TCTR were asked at 3 months of follow-up to fill in the Levine-Katz questionnaire for assessing symptom severity and functional status of the outcomes.
The tools consisted of a musculoskeletal ultrasound machine; an 18-gauge, 90-mm-long spinal needle; a piece of dividing thread; a powered hand tool; and a protective tube. The dividing thread is GuoPercutaneousWire™ (Ridge & Crest Company, Monterey Park, CA), a medical grade thread, with friction coefficient of 0.22, made from non-bonded PET with surface modified by a softening process. Each end of the thread was stiffened by covering it with a PTFE tube, 0.5 mm in diameter and 95 mm in length. GuoPercutaneousWire™ can be used manually in the same way as Gigli saw, and it takes longer time than with the help of a hand tool. The powered hand tool, TWP II (Ridge & Crest Company, Monterey Park, CA), has the function to simulate the manual back-and-forth motion that occurs when alternately pulling on the ends of the thread. The thread was passed through a protective tube made of PTFE with 2 mm ID and 20 mm length. The tube was held at the point of thread entry to preclude the opening in the skin from enlarging during the dividing process. TWP II has a simple structure, and its cost is about one third of an oscillating saw. One of the authors, a tribologist who developed the thread and tool for TCTR, had financial interest in the devices.
TCTR procedure included a preoperative ultrasound evaluation of volar wrist anatomy, local anesthesia, hydro-dissecting, and thread routing guided by ultrasound, confirmation of the looping, and transection of the TCL. Thread looping and transecting are shown graphically in Figs. 1, 2, and 3.
Diagnosis and Procedure
All patients were Asian, and the average age was 52.7 years old (range 22 to 94). Twelve patients were female, and eight were male. Eight patients were employed prior to the procedure, and four patients were farmers. None of them had prior CTR surgery. Most patients had suffered from typical CTS for at least 12 months, and the conservative treatments for them failed. The symptoms included numbness and tingling in the median nerve sensory distribution, nocturnal worsening of numbness and tingling, and worsening of pain while holding or gripping. Their discomfort and pain scores varied between 8 and 10. Two of them also suffered from numbness and tingling in the little finger and in the hypothenar area. Most patients had thenar atrophy and abductor pollicis brevis weakness, and all of them were positive for Tinel’s sign and Phalen’s test. There were 15 patients with decreased two-point discrimination.
To confirm the diagnosis of CTS and to exclude other pathologic conditions, ultrasound evaluation of volar wrists was performed. It revealed that, in all cases, the cross-sectional area of the median nerve at the distal crease of the volar wrist was over 10 mm2, and the closest distance between the median nerve and the ulnar artery was 3 to 6 mm.
The procedures were performed under local anesthesia without conscious sedation for all the patients except the first two cases and case 5. The first two cases were under general anesthesia because of a conservative concern for patient safety and comfort, and case 5 requested general anesthesia because of the patient’s anxiety. When local anesthesia was employed, anesthetic was injected around the TCL during the process of hydro-dissecting, and patients were awake throughout the procedure.
The surgical field was prepared in standard fashion, and the patient’s hand was draped on a support pillow. A 12-MHz ultrasound transducer was utilized to evaluate the carpal tunnel and to locate the safe zone for dividing the TCL and to identify the median nerve, flexor tendons, proximal and distal margins of the TCL, bony marks of pisiform, tubercle of scaphoid, hook of hamate, trapezium, and superficial palmar arterial arch (SPA) (Fig. 4). Skin marks were made to identify the locations of the median nerve and the margins of the TCL, ulnar nerve, ulnar artery, and SPA. The needle entry point was marked 2 cm proximal to the distal crease of the volar wrist and between the median nerve and the ulnar artery. The exit point was marked at the intersection of Kaplan’s line and the radial aspect of the ring finger ray.
Each patient under local anesthesia was conscious during the procedure and cooperated with the surgeon to allow evaluation of the function of the hand, superficialis and profundus tendons, flexor pollicis longus, and thenar muscles. The three patients under general anesthesia were marked while awake prior to the administration of the anesthetic.
Hydro-Dissecting with Anesthetics Injection and Thread Looping
After injecting 1 % lidocaine beneath the dermis at the entry and exit points, the needle was inserted into the subcutaneous layer and was advanced distally into the carpal tunnel within the safe zone between the median nerve and the ulnar artery. The needle was then advanced to the exit point. Simultaneously, the lidocaine solution was injected under real-time ultrasound observation to hydro-dissect the TCL from the median nerve (Fig. 5). Residual adhesion within the carpal tunnel, if any, was identified through active or passive motion of the fingers, allowing further release, if required, by additional hydro-dissecting. A total of 10 ml of 1 % lidocaine was used for each procedure.
To ensure that the surgical needle exited the hand at the desired location, either dorsal extension of the hand or a prebent needle or both were employed. Once the needle had exited the hand, a dividing thread was inserted into and through the needle (Fig. 6). The needle was then removed from the hand, leaving the dividing thread in place (Fig. 7).
The same needle was then inserted the second time into the same entry point at the proximal volar wrist and was advanced over the superficial surface of the TCL with hydro-dissecting to separate the interthenar fascia layer from the superficial surface of the TCL. The needle was guided to the same exit point at the palm. The thread emerging from the hand was then passed through the needle (Fig. 8). The needle was removed from the hand, leaving the dividing thread looped around the ligament.
The two ends of dividing thread were then placed through the protective tube and were linked to the motorized hand tool.
Confirming the Loop and Dividing the Ligament
The desired location of the inserted dividing thread along a looping path surrounding the TCL was verified by gently pulling on the thread and by using ultrasound to image the thread relative to the median nerve, SPA, and ulnar nerve (Fig. 9). After the correct looping was confirmed, the ligament transection was performed using the hand tool for 20 to 30 s. The thread was then removed from the hand through the initial entrance point at the wrist (Fig. 10). Finally, ultrasonic evaluation was employed to confirm that the TCL had been completely divided, and the median nerve, SPA, and flexor tendons remained intact.
We also manually performed dividing processes in recent cases, in the way same as operating a Gigli saw. Manual dividing with the help of two ring handles is controllable and effective, though it takes more than 1 min to complete transection of TCL. So, the hand tool is not necessary, but optional. We found that it was easier to manually perform dividing process through the exit point at the palm, instead of the point at the wrist, if manual dividing is selected.