| Περίληψη: | Sarcopenia has been characterised as a syndrome, associated with a significant functional decline, an increased rate of falls, a higher incidence of hospitalization, a higher mortality rate, impaired ability to perform activities of daily living, and a high economic burden when untreated (1,2). Sarcopenia was recognised as a disease in 2016, receiving an ICD-10-CM code (M62.84). Sarcopenia has been included as a health condition in the “Packages for Rehabilitation Interventions” by the World Health Organization (3,4). The prevalence of sarcopenia has been reported to range between 4.3% and 73.3% (2). The prevalence depends on the screening tools, the criteria used to establish the diagnosis, and the study population. The prompt diagnosis and management considering the ageing population are of paramount importance for sarcopenia (5–8).
The diagnosis of sarcopenia is based on the assessment of muscle strength, muscle mass and physical performance. However, there is no universal consensus on the assessment methods in clinical practice, and it is technically challenging to measure muscle mass and muscle quality accurately (9). The quantitative assessment of muscle mass can be performed by magnetic resonance imaging (MRI) and computed tomography (CT), which are considered as the gold-standards (1,10). However, these tools are not commonly used in daily clinical practice, mainly due to high cost, lack of portability and, in the case of CT, exposure to ionising radiation. Dual-energy X-ray absorptiometry (DXA) is a more widely available method to determine full-body muscle mass (1). A significant disadvantage of DXA is that equipment is not portable, limiting its use as a screening or diagnostic tool in the community.
The ultrasonographic measurement of muscle thickness has been proposed as a useful tool for early detection and monitoring of sarcopenia (11). Ultrasound is a reliable & valid method for determining muscle size in older adults according to published studies (12,13). Commonly used parameters include muscle thickness, cross-sectional area, fascicle length, pennation angle, and echo-intensity (14). Measuring muscle thickness may give an estimate of the decrease in lean body mass (15). Thickness and fascicle length values of medial gastrocnemius muscle have been advocated as alternative measurements for diagnosing/quantifying sarcopenia (16). Muscle mass prediction equations based on multiple ultrasonographic measurements of muscle thickness have been reported in the literature (17,18).
The Reliability Study for US Muscle Thickness Measurements
The reliability of ultrasonography for the assessment of muscle size across a number of limb sites in healthy populations of children and adults is supported by low-level evidence. In addition, there is limited evidence on the reliability of ultrasonographically acquired muscle size measurements in clinical populations (19). A recent systematic review showed that ultrasound is a reliable and valid instrument for muscle size assessment in older adults (12). However, most published studies have either used transverse or longitudinal muscle scans without adequate scientific evidence to support their preference. In addition, studies on quantitative ultrasound muscle measurements have not considered factors that fluctuate throughout the day and may potentially affect muscle thickness, such as the hydration status and physical activity prior to ultrasound evaluation. Another concern is the comparative reliability of measurements of muscle thickness between the dominant and non-dominant sides.
Aims
• To assess the reliability of repetitive muscle thickness measurements on ultrasound scans acquired: at different times of the day (morning and afternoon) and at the same time of the day, within two consecutive days.
• To compare the reliability of repetitive muscle thickness measurements between the dominant and non-dominant sides.
• To evaluate the reliability of muscle thickness measured ultrasonographically, on transverse versus longitudinal scans.
Methods
Ultrasound Scans were performed on muscles involved in activities of daily living: geniohyoid, masseter, anterior arm muscles, rectus femoris, vastus intermedius, tibialis anterior and gastrocnemius. Measurements of the muscle thickness were performed and repeated after 1, 6 and 24 hours, on both dominant and non-dominant side, using both transverse and longitudinal scans.
Results
Thirteen healthy volunteers (8 males & 5 females, mean age = 24 years, SD = 2.86, range = 19 – 29) were included. The Intraclass Correlation Coefficient (ICC) was calculated between the baseline and the 1-, 6- and 24 - hour interval, using a two-way mixed model of absolute agreement. The ICC ranged from 0.295 for the longitudinal scan of the left masseter muscle in the 6-hour interval, to 0.991 for the longitudinal scan of the non-dominant anterior arm muscles in the 24-hour interval.
Conclusions
According to the results of this study, the reliability of the ultrasonographically measured thickness of head and limb muscles varies. The reliability is influenced by the type of section and side of the body. Further research and an international consensus are needed to determine a universally accepted examination protocol for musculoskeletal ultrasound measurement. Evidence-based guidelines are required for standardised image acquisition and measurement techniques.
The Ultrasonographic Measurement of Muscle Thickness in Sarcopenia
Ultrasound is a cost-effective, fast, non-invasive and widely available imaging method that does not expose the person to ionising radiation (20), whereas minimal staff training is needed to obtain images for basic measurements such as muscle thickness. Besides the extremity muscles, the tongue, the masseter and the diaphragm can also be conveniently evaluated with ultrasound (5). In addition, due to high image resolution and features such as dynamic imaging and simultaneous comparability, ultrasound is considered superior to other imaging modalities for many musculoskeletal system pathologies (21). The utility of quantitative ultrasonography for the assessment of muscle mass loss and identification of structural abnormalities is still under study.
Aims
This study aims to investigate which muscles of the head, neck, upper and lower limbs present ultrasonographically detectable thickness changes in sarcopenic patients. More precisely, the objectives were to define which side (dominant versus non-dominant) and ultrasound section (transverse versus longitudinal) presented the most significant thickness changes in each of the studied muscle groups of the sarcopenic patients and to evaluate the muscle thickness measurement, as a potential predictory tool in sarcopenia.
Methods
The participants were assessed according to the EWGSOP2 criteria for the diagnosis of sarcopenia. The handgrip strength was measured by a hand-held dynamometer and the appendicular skeletal muscle mass by DXA. The muscle thickness was measured utilising transverse and longitudinal ultrasound scans bilaterally.
Results
Ninety-four individuals (27 men and 67 women) with a mean age of 75.6 years (SD=6.6), referred for sarcopenia screening to the Outpatient Sarcopenia Clinic of the Rehabilitation Department of the University Hospital of Patras, participated in this study. The geniohyoid and medial head of gastrocnemius thickness in all ultrasound sections, and the thickness of the rectus femoris and vastus intermedius, in specific sections, was significantly decreased in sarcopenic patients (p<0.05). The ROC analysis of the ultrasound muscle thickness measurements resulted in a significant association with sarcopenia.
Conclusions
The results of this study have shown that the ultrasonographically measured thickness of the neck and lower limb muscles can be used for predicting sarcopenia with high sensitivity and specificity. Further research, based on larger-scale studies, is required to thoroughly investigate the role of ultrasonography as a diagnostic tool for sarcopenia and to validate cut-off values in the assessment of muscle mass quantity and quality. Multicentre studies will be needed to standardise the measuring methodology and investigate in which extend it can be used in different ethnic groups, specific population subgroups and on various types of equipment.
Final Remarks and Future Perspectives
According to previous studies, ultrasonography is a valid and reliable method in the assessment of muscle mass (12,13,22). The muscle thickness measured ultrasonographically seems to be an easy, fast and reliable method for the estimation of muscle mass loss in sarcopenia with a potential role in the evaluation of the effectiveness of preventive and therapeutic interventions. Specifically, the geniohyoid and rectus femoris (transverse section – non-dominant side) seems to be the most advantageous ones.
To the best of our knowledge, there is no consensus or guidelines concerning which side of the body should be preferred for the assessment of sarcopenia using ultrasound muscle measurements. The results of this study indicate statistically significant differences in muscle thickness between the dominant versus non-dominant sides, for specific muscles and sections. Moreover, the type of section (transverse versus longitudinal) seems to influence the measurements in some muscles. Further research is required to define which muscle or combination of muscles, type of scan and body side should be used preferentially, in terms of accuracy, utilised for the assessment of muscle mass loss in sarcopenia.
The integration of machine learning techniques in musculoskeletal ultrasonography is challenging but promising field (23–25). Computer-aided diagnostic systems could help in reducing examination time; while increasing the accuracy of the measurements significantly. Moreover, computer-aided diagnostic systems could be used to objectivate the measurements, allowing for a cost-efficient and large-scale screening of the population. The early detection of sarcopenia in the elderly, particularly in the most vulnerable groups, is of paramount importance. Artificial intelligence could become extremely helpful in this regard.
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