Eight Weeks of 448 kHz Radiofrequency Therapy Increases Multifidus Muscle Cross-Sectional Area and Modulates Thoracolumbar Range of Motion in Horses with Chronic Back Pain.

Overview

• This study examined the effects of an 8-week course of 448 kHz radiofrequency therapy on the size of the multifidus muscles and spinal movement in horses suffering from chronic back pain.
• The research found that the therapy increased the muscle size and influenced spinal motion, suggesting improved back stability and muscle function.

Study Purpose and Design

• Purpose:
  • To investigate how 448 kHz radiofrequency (RF) therapy affects the multifidus muscle cross-sectional area (CSA) and the range of motion (ROM) of the thoracolumbar spine in horses with chronic back pain.
• Subjects:
  • Eight Thoroughbred horseball horses diagnosed with chronic back pain were included.
• Treatment:
  • Each horse received four RF treatments focused on spinal segments between thoracic vertebra 9 (T9) and lumbar vertebra 6 (L6).
  • Treatments were administered every two weeks over a total period of 8 weeks.

Measurements and Timing

• Multifidus Muscle CSA:
  • Measurements were performed at vertebral levels T10 to L5.
  • CSA was assessed before treatment, immediately after the first session, 24 hours post first session, and 8 weeks after starting treatment (15 days after the last session).
• Thoracolumbar Range of Motion:
  • Differential spinal ROM was measured between several points: withers (W), T13, T18, L3, and sacrum (S).
  • Movements observed included axial rotation and flexion-extension.

Key Results – Multifidus Muscle

• Significant increase in multifidus CSA across all measured sites (T10-L5) after 8 weeks of RF therapy (p < 0.001).
• These increases were symmetrical on both sides of the spine, showing no significant side-to-side differences.
• Largest CSA increases seen at the mid-thoracic to lumbar vertebrae:
  • T18: +2.52 cm
  • L5: +1.90 cm
  • T16: +1.77 cm
• The increased muscle size indicates hypertrophy, suggesting improved muscle mass in response to the RF treatment.

Key Results – Spinal Range of Motion

• Axial Rotation:
  • Transient increase in axial rotation between withers and T13 vertebrae 24 hours after first treatment (+4.8°, p < 0.001).
  • This increase returned to baseline by the 8-week point.
• Caudal Thoracolumbar Motion (segments T18-L3):
  • Significant decrease at 8 weeks (-4.2°, p = 0.004), suggesting enhanced segmental stability in that region.
• Flexion-Extension:
  • Immediate post-treatment increase between withers and T13 (+2.29°, p = 0.009).
  • Reduction below baseline at 8 weeks (-2.49°, p = 0.005), indicating some modulation of spinal flexibility over time.
• Lumbosacral ROM showed minimal or no significant changes throughout the study.

Interpretation and Implications

• The therapy produced multifidus muscle hypertrophy, which likely enhances neuro-muscular dynamic stabilization of the spine.
• The initial temporary increase in mobility could reflect reduced stiffness or pain immediately after treatment session.
• The subsequent reduction in caudal thoracolumbar motion suggests improved stability through stronger muscle support.
• Overall, 448 kHz RF therapy appears to be an effective non-invasive intervention to promote muscle growth and modulate spinal movement in horses with chronic back pain.
• This might help reduce pain, improve functional mobility, and stabilize the spine in equine rehabilitation settings.

Study Strengths and Limitations

• Strengths:
  • Objective quantification of muscle size and spinal ROM using measurements at multiple timepoints.
  • Consistent results across bilateral muscle sites.
• Limitations:
  • Small sample size limited to 8 horses, which may affect generalizability.
  • Specific to Thoroughbred horseball horses; results may vary in other breeds or disciplines.
  • Longer-term effects beyond 8 weeks were not assessed.