# Effects of Neuromuscular Electrical Stimulation and Therapeutic Ultrasound on Quadriceps Contracture of Immobilized Rats

## TL;DR

This study shows that combining therapeutic ultrasound and neuromuscular electrical stimulation helps treat quadriceps contracture in rats more effectively than either method alone.

## Contribution

The study introduces a novel combination therapy using ultrasound and NMES for treating quadriceps contracture in an animal model.

## Key findings

- The combination of therapeutic ultrasound and NMES reduced muscle atrophy and fibrosis in rats with quadriceps contracture.
- The combined therapy significantly decreased pro-fibrotic markers and increased anti-fibrotic gene expression.
- The combination therapy improved joint range of motion and sarcomere length compared to other treatments.

## Abstract

Quadriceps contracture is a condition that can be observed in young dogs, such as a congenital disability or complication following a hindlimb fracture. Although surgical treatments have been reported, it is difficult to restore normal limb function when the disease is advanced in stage. Rehabilitation early in the course of the disease may effectively improve progress. Using a rat model, we investigated the effectiveness of therapeutic ultrasound and neuromuscular electrical stimulation (NMES) for quadriceps contracture treatment. Quadriceps contracture was induced by immobilizing both hindlimbs for 14 days. Then, we compared the effectiveness of four rehabilitation programs, including spontaneous recovery, therapeutic ultrasound, NMES, and a therapeutic ultrasound and NMES combination on quadriceps contracture for 28 days. After completing 28 days of rehabilitation, the range of joint motion (ROM), muscle histopathology, and levels of fibrosis and anti-fibrosis-associated mRNA expression were measured. The results showed that the therapeutic ultrasound and NMES combination inhibited sarcomere length shortening, muscle atrophy, and muscle fibrosis in quadriceps contracture.

Quadriceps contracture is a condition where the muscle–tendon unit is abnormally shortened. The treatment prognosis is guarded to poor depending on the progress of the disease. To improve the prognosis, we investigated the effectiveness of therapeutic ultrasound and NMES in treating quadriceps contracture in an immobilized rat model. Thirty-six Wistar rats were randomized into control, immobilization alone, immobilization and spontaneous recovery, immobilization and therapeutic ultrasound, immobilization and NMES, and immobilization and therapeutic ultrasound and NMES combination groups. The continuous therapeutic ultrasound (frequency, 3 MHz, intensity 1 W/cm2) and NMES (TENS mode, frequency 50 Hz; intensity 5.0 ± 0.8 mA) were performed on the quadriceps muscle. On Day 15, immobilization-induced quadriceps contracture resulted in a decreased ROM of the stifle joint, reduction in the sarcomere length, muscle atrophy, and muscle fibrosis. On Day 43, therapeutic ultrasound, NMES, and combining both methods improved muscle atrophy and shortening and decreased collagen type I and III and α-SMA protein. The combination of therapeutic ultrasound and NMES significantly reduced the mRNA expression of IL-1β, TGF-β1, and HIF-1α and increased TGF-β3. Therefore, the combination of therapeutic ultrasound and NMES is the most potent rehabilitation program for treating quadriceps contracture.