Delgado-Diaz DC1, Herrera Villabona E1
1Universidad Industrial de Santander, Bucaramanga, Colombia
Background: Therapeutic ultrasound (TUS) is one of the most commonly used modality in soft-tissue injuries in order to reduce edema and pain, and accelerate tissue repair/regeneration, however the mechanisms of action of TUS are not clear yet. It is claimed that due to its thermal effects, TUS could potentially modulate pain perception by modifying the velocity of nerve conduction. Despite its use in pain modulation, there is little clinical evidence from to support that TUS increases tissue temperature to a physiological level that could potentially trigger neural effects.
Purpose: To examine the immediate effect of continuous TUS on motor and sensory nerve conduction parameters on the lower limb.
Methods: We conducted a randomized single-blinded experimental study. 15 healthy, physically active males (n=5) and females (n=10) (age: 20.9±1.2y/o; BMI: 21.6±1.5kg/cm2) volunteered to participate. Calf skin fold was 16.5±1.2mm, used to correct adjust nerve conduction parameters. Measurements of skin temperature and sensory (sural nerve) and motor (posterior tibial) nerve conduction studies were conducted on the dominant leg immediatly before and after TUS treatment. Infrared thermometer (Raytek STTM PRO®) was used to determine the skin temperature in the midpoint of the treatment area; Nicolet Compass Meridian® equipment was used to determine conduction velocity, latency and duration of the motor and sensorial compound action potential, following standardized protocols (bandwidth setting of 20Hz to 3 kHz, a gain of 10mV/div, 2µV/div and sweep speed 2ms/div). TUS treatment was delivered in a 50cm2 area of the calf muscles, including the distal myotendinous junction, delivered in a continuous mode during 8m, at a frequency of 1MHz, and SATA of 1.5W/cm2; a previously calibrated Mettler Sonicator 730® was used (ERA de 8.5 cm2, BNR 5:1). Statistical analysis included normality tests, and comparisons of each nerve function parameter pre vs. pos were performed by paired t-test.
Results: No change in skin temperature in response to the treatment was determined (Δ=0.5±1.1°, 95%CI=-1.6 to 0.5; p=0,07). Sensory nerve action potential parameters showed no change in response to TUS; Δamplitude 3.9±12.3µV (p=0.5); duration 0.04±0.8ms (p=0.8); latency -0.05±0.7ms (p=0.4); and conduction velocity -0.8±1.3m/s (p=0.9). Motor action potential latency, amplitude and duration were affected by TUS (data reported by site of stimulation, proximal (P) and distal (D)), no further change was detected; D-latency 0.2±0.2ms (p=0.002); D-amplitude -1,1±1,8mV (p=0.03); D-duration 0.2±0.3ms (p=0.99); P-latency 0.2±0.2ms (p=0.001); P-amplitude 0.2±0.7mV (p=0.8); P-duration 0.3±0.3ms (p=0.06); velocity 0.1±1.1m/s (p=0.06).
Conclusion(s): TUS does not immediately affect sensorial nerve function, but alters parameter related to the synchrony of the conduction of the motor nerves. Despite the thermal effects are the main physiology response to continuous TUS, our results show no effect of the likely rise in temperature on the muscle function. Therefore, the modulation of pain attributed to TUS might not be due to changes in the velocity of sensorial conduction. However, the findings on the motor nerves should be further studied.
Implications: Our results show that TUS can be safely applied over superficial nerves (no changes in its function), thought the mechanism through which this modality helps in the pain modulation needs to be further investigated.
Keywords: Therapeutic Ultrasound, Nerve Function, Nerve Conduction Studies
Funding acknowledgements: Universidad Industrial de Santander
Purpose: To examine the immediate effect of continuous TUS on motor and sensory nerve conduction parameters on the lower limb.
Methods: We conducted a randomized single-blinded experimental study. 15 healthy, physically active males (n=5) and females (n=10) (age: 20.9±1.2y/o; BMI: 21.6±1.5kg/cm2) volunteered to participate. Calf skin fold was 16.5±1.2mm, used to correct adjust nerve conduction parameters. Measurements of skin temperature and sensory (sural nerve) and motor (posterior tibial) nerve conduction studies were conducted on the dominant leg immediatly before and after TUS treatment. Infrared thermometer (Raytek STTM PRO®) was used to determine the skin temperature in the midpoint of the treatment area; Nicolet Compass Meridian® equipment was used to determine conduction velocity, latency and duration of the motor and sensorial compound action potential, following standardized protocols (bandwidth setting of 20Hz to 3 kHz, a gain of 10mV/div, 2µV/div and sweep speed 2ms/div). TUS treatment was delivered in a 50cm2 area of the calf muscles, including the distal myotendinous junction, delivered in a continuous mode during 8m, at a frequency of 1MHz, and SATA of 1.5W/cm2; a previously calibrated Mettler Sonicator 730® was used (ERA de 8.5 cm2, BNR 5:1). Statistical analysis included normality tests, and comparisons of each nerve function parameter pre vs. pos were performed by paired t-test.
Results: No change in skin temperature in response to the treatment was determined (Δ=0.5±1.1°, 95%CI=-1.6 to 0.5; p=0,07). Sensory nerve action potential parameters showed no change in response to TUS; Δamplitude 3.9±12.3µV (p=0.5); duration 0.04±0.8ms (p=0.8); latency -0.05±0.7ms (p=0.4); and conduction velocity -0.8±1.3m/s (p=0.9). Motor action potential latency, amplitude and duration were affected by TUS (data reported by site of stimulation, proximal (P) and distal (D)), no further change was detected; D-latency 0.2±0.2ms (p=0.002); D-amplitude -1,1±1,8mV (p=0.03); D-duration 0.2±0.3ms (p=0.99); P-latency 0.2±0.2ms (p=0.001); P-amplitude 0.2±0.7mV (p=0.8); P-duration 0.3±0.3ms (p=0.06); velocity 0.1±1.1m/s (p=0.06).
Conclusion(s): TUS does not immediately affect sensorial nerve function, but alters parameter related to the synchrony of the conduction of the motor nerves. Despite the thermal effects are the main physiology response to continuous TUS, our results show no effect of the likely rise in temperature on the muscle function. Therefore, the modulation of pain attributed to TUS might not be due to changes in the velocity of sensorial conduction. However, the findings on the motor nerves should be further studied.
Implications: Our results show that TUS can be safely applied over superficial nerves (no changes in its function), thought the mechanism through which this modality helps in the pain modulation needs to be further investigated.
Keywords: Therapeutic Ultrasound, Nerve Function, Nerve Conduction Studies
Funding acknowledgements: Universidad Industrial de Santander
Topic: Sport & sports injuries; Musculoskeletal; Sport & sports injuries
Ethics approval required: Yes
Institution: Universidad Industrial de Santander
Ethics committee: Comité de Etica de Investigación Científica
Ethics number: 5695
All authors, affiliations and abstracts have been published as submitted.
