Morphologic change of nerve and symptom relief are similar after mini-incision and endoscopic carpal tunnel release: a randomized trial

Abstract

Background: The symptoms in carpal tunnel syndrome (CTS) can be ameliorated by open and endoscopic release of the transverse carpal ligament. It is unknown whether a mini-incision or endoscopic carpal tunnel release more effectively reverses the pathological changes that are observed in the median nerve in patients with CTS and these morphologic changes correlates with the subjective outcomes after carpal tunnel release. We hypothesized that (1) at 24 weeks after surgery, the subjective outcomes of mini-incision release and endoscopic release would not differ in patients with CTS; and (2) the ultrasonographic (US) morphology of the median nerve reverses similarly after mini-incision and endoscopic release; (3) the subjective outcomes correlates with these morphologic changes.

Methods: Between November 2011 and January 2013, 67 patients with CTS in their dominant wrist were randomized to either mini-incision (n = 32) or endoscopic (n = 35) release. Each patient was assessed by both the Boston Carpal Tunnel Questionnaire (BCTQ) and the Disabilities of the Arm, Shoulder, and Hand (DASH) pre-operatively and 24 weeks' post-operation. An US examination was conducted at both time points to measure the cross-sectional area (CSA) at the inlet, middle, and outlet (CSA-I, CSA-M and CSA-O) and the flattening ratio (FR) at the middle and outlet (FR-M and FR-O) of the median nerve.

Results: The post-operative mean BCTQ and DASH scores were improved significantly from the pre-operative scores in both groups (p < 0.001). The mean CSA-I decreased and CSA-M and CSA-O increased similarly in both groups (by 3.3, 3.0, and 3.8 mm2 in the mini-incision group and 2.9, 3.1. and 2.7 mm2 in the endoscopic group. The mean FR-M/FR-O decreased similarly from 3.6/4.2 to 3.2/3.0 in the mini-incision group and 3.8/4.3 to 3.2/2.9 in the endoscopic group. There were no significant differences in the subjective outcome scores or median nerve measures between the two groups. Improvement in the BCTQ-S only was significantly correlated with changes in the CSA at the inlet.

Conclusions: Mini-incision and endoscopic release both similarly relieved subjective symptoms and functions along with the pathological changes in the median nerve morphology along the carpal tunnel in patients with idiopathic CTS. Symptom relief after surgical decompression seems to correlate with reduced nerve swelling at carpal inlet and reversed nerve flattening inside carpal tunnel.

Trial registration: This study was retrospectively registered in "ClinicalTrials.gov" at Oct 18th, 2013, and the registration number was NCT01972165 .

Keywords: Carpal tunnel syndrome; Endoscopic carpal tunnel release; Mini-incision; Ultrasonography.

Figures

Fig. 1

The randomization scheme for the study as demonstrated in the CONSORT flowchart

Fig. 2

a A transverse US scan to measure the cross-sectional area (CSA) of the median nerve at the tunnel inlet, which was at the level of the distal wrist crease. The CSAs of the nerve at the middle of the tunnel at the level of the pisiform and the tunnel outlet at the level of the hamate hook were also measured. b The flattening ratio (FR) of the median nerve, calculated by dividing the transverse diameter of the nerve by the anteroposterior diameter

Fig. 3

Pairwise scatter plot of difference values for the clinical outcomes and the sonographic outcomes. Positive values indicate improvement of outcomes. Improvement in BCTQ-S score was significantly correlated with improvement in CSA-I (p = 0.005), while other values were not. BCTQ = Boston Carpal Tunnel Questionnaire; DASH = Disabilities of Arm, Shoulder and Hand; CSA-I = Cross-Sectional Area - Inlet; CSA-M = Cross-Sectional Area - Middle; CSA-O = Cross-Sectional Area - Outlet; FR-M = Flattening Ratio - Middle; FR-O = Flattening Ratio – Outlet