Functional and Morphological Changes in the Deep Lumbar Multifidus Using Electromyography and Ultrasound

Area of Science:

• Biomedical Engineering
• Neuroscience
• Musculoskeletal Research

Background:

• Chronic low back pain (cLBP) is associated with changes in lumbar multifidus (LM) muscle function.
• Previous research primarily focused on superficial LM, limiting understanding of deep multifidus (DM) involvement.
• Accurate assessment of DM neuromuscular activity in cLBP has been challenging due to technical limitations.

Purpose of the Study:

• To develop and validate a novel method for recording intramuscular EMG signals from the deep multifidus (DM).
• To investigate neuromuscular activation patterns and morphological changes in the DM of individuals with cLBP.
• To explore the relationship between DM EMG activity and structural alterations in cLBP.

Main Methods:

• Development of a novel intramuscular EMG recording technique using fine-wire electrodes integrated with an sEMG system.
• Measurement of DM EMG signals in 24 cLBP patients and 26 healthy controls.
• Ultrasound imaging to assess DM muscle thickness, cross-sectional area, and contractile activity.

Main Results:

• cLBP patients exhibited decreased average EMG and root mean square (RMS) values in the DM.
• Increased median frequency and mean power frequency were observed in the DM of cLBP patients.
• A positive correlation was found between average EMG and DM contractile activity, but not with noncontractile anatomical abnormalities.

Conclusions:

• The novel intramuscular EMG method effectively captures DM neuromuscular activity.
• cLBP is characterized by altered neuromuscular activation patterns and morphological changes in the DM's contractile properties.
• Findings provide new insights into the pathophysiology of cLBP, particularly concerning deep muscle involvement.