Los fisioterapeutas utilizan la ecografía de rehabilitación (RUSI) como una herramienta de retroalimentación para medir los cambios en la morfología muscular durante intervenciones terapéuticas como los ejercicios de control motor (MCE). Sin embargo, falta una descripción estructurada de su eficacia.
1. Introduction
Motor control exercise (MCE) consists of an exercise-based intervention focused on the activation of deep muscles to improve the control and coordination of these muscles
[1]. MCE is widely used since evidence suggests improvements in pain, function, self-perceived recovery and quality of life up to 12 weeks
[1]. Several mechanisms, including the lack of stability of the spine, impaired motor control and/or muscle activity patterns, or disturbed proprioception and restricted range of motion, have been proposed for explaining non-specific spine pain
[2]. Motor control exercises aim to restore muscular coordination, control and capacity by training isolated contractions of deep trunk muscles while maintaining a normal breathing and progressing to pre-activate and maintain the contraction during dynamic and functional tasks
[3]. Given the difficulty that some patients can perceive during MCE, these exercises are usually performed in supervised sessions providing biofeedback on the activation of trunk muscles for facilitating the awareness and control of these deep muscles’ isolated contractions
[4].
According to the definition provided by Blumenstein et al.
[5], biofeedback refers to external psychological, physical, or augmented proprioceptive feedback that is used to increase an individual’s cognition of what is occurring physiologically in the body. Although several modalities are described in the literature (e.g., electroencephalography, skin resistance, electrocardiography, sphygmomanometry, strain-gauge devices, thermal feedback), the most used biofeedback modalities include ultrasound imaging, pressure biofeedback units and electromyography.
Ultrasound imaging (US) is a fast, easy, safe, noninvasive and low-cost real-time method frequently used for assessing muscle morphology (e.g., thickness, cross-sectional area and volume)
[6], quality (e.g., echo-intensity and fatty infiltration)
[7] and function
[8]. This method allows both patients and clinicians to see in real time muscle morphology changes, since this is sensitive to positive and negative changes and therefore is valid for measuring trunk muscle activation during isometric submaximal contractions
[9].
Surface electromyography, which consists of placing surface electrodes to detect changes in skeletal muscle activity for providing to the patient a visual or auditory signal for either increasing or reducing muscle activity, is also used as a biofeedback method in rehabilitation
[10][11]. However, surface EMG cannot be used for assessing deep muscles and needle electrodes are needed
[12].
Finally, pressure biofeedback units are also commonly used since they are economic and easy to apply in a clinical setting. This instrument consists of an inflatable cushion which is connected to a pressure gage, which displays feedback on muscle activity
[13].
Since the last systematic review assessing the efficacy of Rehabilitative Ultrasound Imaging (RUSI) for enhancing the performance and contraction endurance of skeletal muscles during MCE was published more than 10 years ago and new evidence is available
[14], an updated systematic review is needed.
2. Study Selection
The results of the search and selection process (identification, screening, eligibility and analyzed) from the 1084 studies identified in the search to the 11 studies included in the review
[15][16][17][18][19][20][21][22][23][24][25] are described in the flow diagram shown in
Figure 1.
Figure 1. Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) flowchart.
3. Methodological Quality and Risk of Bias
The methodological quality scores ranged from 4 to 9 (mean: 6.4, SD: 1.4) out of a maximum of 10 points (Table 1). The most consistent flaws were lack of participants (all studies) and therapist blinding (ten studies), concealed allocation (just five studies considered a concealed allocation) and providing point measures and measures of variability (eight studies).
Table 1. Methodological quality assessment of the included studies.
RCT: Randomized Clinical Trial; CT: Clinical Trial. 1: selection criteria; 2: random allocation; 3: concealed allocation; 4: similarity at baseline; 5: subject blinding; 6: therapist blinding; 7: assessor blinding; 8: >85% measures for initial participants; 9: intention to treat; 10: between-group statistical comparisons; 11: point and variability measures. None of the selected articles had a conflict of interest; −: No; +: Yes.
The risk of bias analysis is described in
Figure 2. Seven studies showed an overall low risk of bias
[15][16][17][20][21][23][24]. However, four studies presented some concerns regarding the measurement of the outcomes and the reported results which should be considered on data interpretation
[18][19][22][25].
Figure 2. Risk of bias traffic-light plot.
4. Data Analysis
Table 2 summarizes the studies included in this systematic review investigating the efficacy of RUSI as biofeedback tool during MCE. The included studies compared RUSI visual feedback against verbal (
n = 8)
[15][16][18][19][20][22][24][25], tactile (
n = 5)
[16][18][21][23][24] and pressure unit (
n = 2)
[18][23] feedback. Further, one study evaluated different modalities of RUSI visual feedback (constant versus variable)
[17].
Table 2. Data of the studies investigating RUSI as the biofeedback method for MCE.
ADIM: Abdominal Draw-In Maneuver; AHE: Abdominal Hollowing Exercise; EO: External Oblique; IO: Internal Oblique; LM: Lumbar Multifidus; TrA: Transversus Abdominis.
Most studies assessed the deep abdominal wall musculature (including Transversus Abdominis -TrA-
[15][16][18][19][20][22][24], Internal Oblique -IO-
[16][18][19][22][24] and External Oblique -EO-
[16][18][19][22][24]). Although procedures were not consistent (e.g., postures, measurement timing, resting between series, number of series, etc.), all studies assessing the abdominal wall muscles used the Abdominal Hollowing Exercise -AHE-
[15][16][18][19][20][21][24]. In addition, pelvic floor muscles
[23], serratus anterior
[21] and lumbar multifidus -LM-
[17][20][24] were also analyzed.
The included studies reported different outcomes since seven assessed changes in muscle thickness and/or pressure between MCE and rest
[15][18][19][20][22][23][24][25], number of repetitions needed to correctly perform the MCE
[15][16], ability to retain the correct MCE performance
[16][17][24], muscle electromyographic activity
[15][18][19][20][22][23][25], and clinical outcomes
[23].
Regarding the populations included in the studies, most of them included healthy subjects
[15][16][17][18][19][20][22][25] and just three studies included clinical populations, one study included patients with mild-to-moderate fecal incontinence
[23], one study included patients with unilateral subacromial pain
[21], and one study included patients with chronic low back pain
. En general, la retroalimentación visual de RUSI fue una herramienta de retroalimentación más efectiva que la retroalimentación verbal o la facilitación manual única para la mayoría de los resultados evaluados (por ejemplo, número de repeticiones necesarias para realizar correctamente el MCE, el grosor muscular o la actividad electromiográfica) considerando que los procedimientos no fueron consistente entre estudios. Sin embargo, parece igualmente eficaz como unidades de biorretroalimentación a presión.