Ultrasound-Guided Minimal Invasive Carpal Tunnel Release: An Optimized Algorithm

Abstract

Purpose: To present a safety-optimized ultrasound-guided minimal invasive carpal tunnel release (CTR) procedure.

Materials and methods: 104 patients (67 female, 37 male; mean age 60.6 ± 14.3 years, 95% CI 57.9 to 63.4 years) with clinical and electrophysiological verified typical carpal tunnel syndrome were referred for a high-resolution ultrasound of the median nerve and were then consecutively assigned for an ultrasound-guided CTR after exclusion of possible secondary causes of carpal tunnel syndrome such as tumors, tendovaginitis, ganglia and possible contraindications (e.g., crossing collateral vessels, nerve variations). Applying a newly adapted and optimized algorithm, basing on the work proposed by Petrover et al. CTR was performed using a button tip cannula which has several safety advantages: On the one hand, the button tip cannula acts as a blunt and atraumatic guiding splint for the subsequent insertion of the hook-knife, and on the other hands, it serves as a "hydro-inflation"-tool, i.e., a fluid-based expansion of the working-space is warranted during the whole procedure whenever needed.

Results: In all patients, successful releases were confirmed by the depiction of a completely transected transverse carpal ligament during and in the postoperative ultrasound-controls two weeks after intervention. All patients reported markedly reduction of symptoms promptly after this safety-optimized ultrasound-guided minimal invasive CTR and at the follow-up examination. No complications were evident.

Conclusion: The here proposed optimized algorithm assures a reliable and safe ultrasound-guided CTR and thus should be taken into account for this minimal invasive interventional procedure.

Keywords: Carpal tunnel syndrome; Minimal invasive carpal tunnel release; Ultrasound-guidance.

Fig. 1

US-axial scan depicting the hydrodissection of the median nerve (MN) using a 21G needle (arrows) and the needle tip (arrowhead) within the “expanded” perineural space (asterisk)

Fig. 2

Longitudinal US-scan illustrating the positioning of the button tip cannula (arrows) at the distal reach of the safe zone. Superficial palmar arch (SPA)

Fig. 3

Depiction of the hook-knife (Acufex® 3.0-mm hook-knife, Smith & Nephew PLC, London, England) (left) and the button tip cannula (Keysurgical®, Lensahn, Germany) (right)

Fig. 4

A Anatomic specimen depicting the button tip cannula within the carpal tunnel. Median nerve (MN), ulnar nerve (UN), ulnar artery (UA), transverse carpal ligament (TCL), superficial palmar arch (SPA). B After insertion of the hook-knife ulnar to the button tip. C Position of the instruments within the carpal tunnel with a transected TCL. Note that the MN in this specimen shows marked enlargement typical in patients with CTS

Fig. 5

A Longitudinal US-scan demonstrating the button tip cannula within (arrows) and the hook-knife (arrowheads) entering the carpal tunnel. B Axial US-scan depicting the “Double-Dot Sign” formed by cross-section of the button tip cannula (arrow) and the hook-knife (arrowhead). Median nerve (MN), ulnar artery (UA)

Fig. 6

A Longitudinal US-scan illustrating the cutting of the TCL by retraction of the hook-knife (arrowheads). Hook (void arrowheads). The button tip cannula (arrows) which serves as a guiding tract, remains within the carpal tunnel during the whole release. B Axial US-scan depicting a successful release by “palpation” of the button tip cannula (arrow) through the transected TCL (dotted arrowheads). Median nerve (MN), ulnar artery (UA)