Ultrasound Guided Peripheral Nerve Stimulation of Gluteal Nerves to Enhance Strength and Power in Individuals With Chronic Knee Pain: A Randomized Controlled Pilot Study

This study delves into the comparative efficacy of two modalities of nerve stimulation for enhancing muscular strength and power: the percutaneous application of electrical current via acupuncture needles versus traditional transcutaneous electrical nerve stimulation (TENS). The overarching objective is to discern whether percutaneous peripheral nerve stimulation (pPNS), guided by ultrasound, facilitates superior gains in muscle strength and power in the gluteal muscles compared to conventional TENS.

Participants, suffering from chronic knee pain, were systematically randomized into two cohorts: the experimental group underwent ultrasound-guided pPNS targeting the superior and inferior gluteal nerves, whereas the control group received TENS. The experimental setup was meticulously designed to ensure the sole variable of distinction between groups was the method of electrical stimulation applied. pPNS was delivered using a biphasic asymmetric electric current, set to a frequency of 10 Hz, a pulse width of 240 microseconds, and an intensity tailored to achieve maximal muscle contraction without inducing pain, based on a protocol of ten 10-second stimulations interspersed with 10-second rest periods. This regimen was predicated on prior findings demonstrating its efficacy in augmenting isometric strength following femoral nerve stimulation. The control group was subjected to a parallel protocol, differing only in the application technique, wherein electrodes replaced needles, adhering to the same stimulation parameters.

The therapeutic efficacy of both interventions was assessed through a rigorous evaluation of strength and power before and after the administration of therapy. This assessment employed a linear encoder to measure peak strength and concentric power during the Hip Thrust exercise, a method chosen for its reliability in quantifying these parameters. The procedure entailed performing the exercise under three different loads (30%, 50%, and 70% of the participant's maximum capacity, 1RM), with the evaluation aimed at capturing the concentric peak power in each repetition until a noticeable decline in performance was observed.

The hypothesis posits that pPNS, by virtue of its targeted and invasive nature, will yield greater improvements in muscle strength and power than TENS, attributed to its more direct stimulation of the nerve fibers and the encompassing muscle groups. The underpinning rationale is that pPNS's ultrasound-guided approach allows for a more precise delivery of electrical current to the nerves, potentially overcoming limitations associated with the superficial and diffuse application of TENS.

For the analysis of the collected data, an initial evaluation of distribution characteristics will be performed utilizing visual tools such as Q-Q plots and density plots, complemented by statistical measures of kurtosis and skewness to understand the data's underlying structure. The Shapiro-Wilk test will be applied to assess the normality of residuals, ensuring the validity of subsequent statistical tests. Descriptive statistics, including the mean, median, mode, and standard deviation of the collected quantitative measures, will be thoroughly examined to summarize the data effectively. Additionally, the homogeneity of these variables across the dataset will be scrutinized.