Introduction
Carpal tunnel syndrome (CTS) is the most prevalent peripheral
compressive neuropathy.1Although the exact pathophysiology remains nebulous, the prevailing
theory is that progressive ischemic and strangulation of the median
nerve (MN) develop in the high pressure of the intracarpal
tunnel.2,
3
Nerve hydrodissection (HD), a method used to abridge adhesions by
dissecting the anatomic spaces with fluid
injection,4 was recently
found to facilitate ultrasound-guided nerve injection for treating
entrapment
neuropathy.5-8 The
therapeutic rationale is to detach nerve from surrounding compressive
tissue, increasing the blood flow, and allowing the nerve impulses to
re-pass.5-8 Research
published in 2019 demonstrated the efficacy of HD to treat
mild-to-moderate CTS.9Despite the positive clinical effects of HD for CTS, whether the
injection technique would influence the duration of the HD effect is
still unknown.
Currently, the two main methods of ultrasound-guided perineural
injection for CTS, short- or long-axis approaches, are broadly applied
in clinical
practice.10-13 The
method of long-axis injection may directly separate the MN from the
flexor retinaculum (FR) with more contact
area.14 In contrast to
long-axis injection in which only the FR is hydrodissected from the MN,
the operator can simultaneously hydrodissect the FR and subsynovial
connective tissue (SSCT) through the short-axis approach. Furthermore,
the short-axis approach could provide more accuracy with a lesser
incidence of nerve injury because the operator can clearly identify the
MN between the FR and SSCT with ultrasound
guidance.15 However,
due to inconsistent results from published studies, controversy
continues about the optimal strategy between short- and long-axis
injection for CTS.12,
13, 16-18In our clinical practice, both short- and long-axis injections were
effective for HD in patients with CTS. Moreover, we observed that
hydrodissecting both the FR and the SSCT seemed to enhance the
therapeutic benefits of HD, based on patients’ clinical presentations.
Thus, we hypothesized that short-axis HD may have equivalent or superior
efficacy than long-axis HD for treating CTS. Hence, this trial aimed to
compare short- and long-axis approaches in patients with
mild-to-moderate CTS.