A scoping review of methods used in musculoskeletal soft tissue and nerve shear wave elastography studies

Abstract

This scoping review of shear wave elastography (SWE) articles in musculoskeletal soft tissue and nerve research demonstrates methodological heterogeneity resulting from a lack of standardized data collection and reporting requirements. Seven literature databases were searched for original articles published in English from 2004-2020 that examine human skeletal muscles, tendons, and nerves in vivo. Although 5,868 records were initially identified, only 375 reports met inclusion criteria. Of the 375 articles, 260 examined 89 unique muscles, 94 examined 14 unique tendons, and 43 examined 8 unique nerves. Cohorts were often small (n = 11-20) and young (mean = 20-29 years), and participants were typically tested in the prone position. Regarding equipment, a variety of ultrasound systems (n = 11), ultrasound models (n = 18), and transducers (n = 19) were identified. Only 11% of articles contained information on the use of electromyography to confirm absence of muscle activity, and only 8% reported measurement depth. Since musculoskeletal soft tissue and nerve stiffness can vary significantly based on data collection methods, it is essential to standardize SWE collection and reporting procedures. This will allow SWE to serve as a valid and reproducible tool for assessing tissue pathology, disease progression, and response to intervention within a variety of musculoskeletal and nerve-related disorders.

Keywords: Elastic modulus; Elastogram; Musculoskeletal ultrasound; Neuromuscular ultrasound; Shear wave elastography; Sonoelastography.

Figure 1.

Flow Diagram of Study Selection Process. This diagram portrays the flow of information through the various phases of the scoping review by indicating the number of records identified from various databases, excluded at each stage of review, and included in the final analysis.

Figure 2.

Percentage of Articles by Soft Tissue Category. The vertical bar graph depicts the percentage of articles (n=375) that included muscles, tendons, nerves, and ligaments for shear wave elastography examination. Note: Some articles examined multiple soft tissue categories, accounting for overlap in the category percentages (i.e., exceeding 100%).

Figure 3a.

Percentage of Specific Tissues for Articles Examining Muscles. This horizontal bar graph depicts the percentage of muscle articles (n=260) that involved lower body muscles, upper body muscles, trunk muscles, or non-limb/trunk muscles. The *Other category contained in each bar graph consists of specific tissues that were only examined in 2 articles or less and are listed below:

1. Lower Body Muscles: Adductor Magnus, Biceps Femoris (Short Head), Extensor Digitorum Longus, Flexor Digitorum Brevis, Gluteus Medius, Gracilis, Iliacus, Iliopsoas, Psoas Major, Quadricep (Unspecified), Quadriceps Femoris, Sartorius, Tensor Fasciae Latae, Triceps Surae

2. Upper Body Muscles: Abductor Hallucis, Brachioradialis, Extensor Carpi Radialis Brevis, Extensor Carpi Ulnaris, Flexor Carpi Radialis, Flexor Digitorum Profundus, Flexor Digitorum Superficialis, Forearm Flexor, Hypothenar, Latissimus Dorsi, Pronator Quadratus, Teres Major, Thenar, Triceps Brachii (Head Not Specified)

3. Trunk Muscles: Multifidus (Sacral), Serratus Anterior

4. Non-Limb/Trunk Muscles: Anterior Scalene, Diaphragm, Digastric (Anterior Belly), Geniohyoid, Lateral Rectus, Levator Ani, Medial Rectus, Musculus Rectus Inferior, Musculus Rectus Medialis, Musculus Rectus Superior, Musculus Rectus Temporalis, Spinalis Capitis, Urethral Rhabdosphincter

Note: Some muscle articles examined multiple specific tissues, accounting for overlap in the category percentages (i.e., exceeding 100%).

Figure 3b.

Percentage of Specific Tissues for Articles Examining Tendons, Nerves, and Ligaments. These horizontal bar graphs depict the percentage of specific tissues examined for articles on tendons (n=94), nerves (n=43), and ligaments (n=19). Note: Some tendon, nerve, and ligament articles examined multiple specific tissues, accounting for overlap in the category percentages (i.e., exceeding 100%).