Lumbar multifidus muscle ultrasound imaging: Is handheld technology reliable?

Advancement in ultrasound imaging technology has led to the development of handheld devices that are more accessible to physical therapists due to decreased cost, reduced size, and improved ease of use relative to current established units. Physical therapists use ultrasound imaging of the lumbar multifidus muscle (LMM) to assist in rehabilitation of patients with lumbar pathology.

To identify the inter-device reliability of measuring the LMM thickness during a sustained contraction when comparing handheld (Butterfly iQ+) and established (SonoSite M-Turbo) ultrasound units. A secondary purpose was to determine the reliability of a student physical therapist using both devices.

A reliability measurement study METHOD: A blinded examiner identified the LMM at the L4 vertebral level and measured the thickness of the contracted muscle utilizing both the handheld and established ultrasound devices. ICC values were calculated to determine the inter-device and intra-rater reliability.

The study included 42 healthy participants, 30 females and 12 males, with a mean age of 38.5 years. The inter-device reliability during a sustained LMM contraction was excellent (ICC = 0.92, 95% CI: 0.87-0.94) and the intra-rater reliability was good for both the handheld (ICC = 0.85, 95% CI: 0.73-0.92) and established (ICC = 0.89, 95% CI: 0.82-0.93) ultrasound units.

Results support the use of handheld ultrasound by physical therapists and students to measure the LMM thickness. Future studies could investigate the reliability of handheld ultrasound in a variety of musculoskeletal and pathological structures important to PT practice.