An anatomical comparison of the fasciae of the thigh: A macroscopic, microscopic and ultrasound imaging study

Abstract

Although the number of Ultrasound (US) imaging studies investigating the fascial layers are becoming more numerous, the majority tend to use different reference points and terminology to describe their findings. The current work set out to compare macroscopic and microscopic data of specimens of the fascial layers of the thigh with US imaging findings. Specimens of the different fascial layers of various regions of the thigh were collected for macroscopic and histological analyses from three fresh cadavers and compared with in vivo US images of the thighs of 20 healthy volunteers. The specimens showed that the subcutaneous tissue of the thigh is made up of three layers: a superficial adipose layer, a membranous layer/superficial fascia, and a deep adipose layer. The deep fascia is composed of an aponeurotic fascia, which envelops all the thigh muscles and is laterally reinforced by the iliotibial tract and an epimysial fascia, which is specific for each muscle. The morphometric measurements of the thickness of the superficial fascia were different (anterior: 153.2 ± 39.3 µm; medial: 128.4 ± 24.7 µm; lateral: 154 ± 28.9 µm; and posterior: 148.8 ± 33.2 µm) as were those of the deep fascia (anterior: 556.8 ± 176.2 µm; medial: 820.4 ± 201 µm; lateral: 1112 ± 237.9 µm; and posterior: 730.4 ± 186.5 µm). The US scans showed a clear picture of the superficial adipose tissue, the superficial fascia, and the deep adipose tissue, as well as the deep fasciae. The epimysial and aponeurotic fasciae of only some topographic areas could be independently identified. The US imaging findings confirmed that the superficial and deep fascia have different thicknesses, and they showed that the US measurements were always larger with respect to those produced by histological analysis (p < 0.001) probably due to shrinkage during the processing. The posterior region (level 1) of the superficial fascia had, for example, a mean thickness of 0.56 ± 0.12 mm at US, while the histological analysis showed that it was 148.8 ± 33.2 µm. Showing a similar pattern, the thickness of the deep fascia was as follows: 1.64 ± 0.85 mm versus 730.4 ± 186.5 µm. Study results have confirmed that US can be considered a valid, non-invasive instrument to evaluate the fascial layers. In any event, there is a clear need for a set of standardised protocols since the thickness of the fascial layers of different parts of the human body varies and the data obtained using inaccurate reference points are not reproducible or comparable. Given the inconsistent terminology used to describe the fascial system, it would also be important to standardise the terminology used to define its parts. The difficulty in distinguishing between the epimysial and aponeurotic/deep fascia can also impede data interpretation.

Keywords: fascia lata; imaging; musculo-skeletal ultrasound; superficial fascia; thickness.

Figure 1

Histological images (Azan‐Mallory staining) of the anterior (a, a1, a2), medial (b, b1, b2), lateral (c, c1, c2) and posterior (d, d1, d2) regions at the Ant1, Med 1, Lat 1 and Post 1 levels. S.F., Superficial Fascia; D.F., Deep Fascia. *= Loose connective tissue. °= Epimysium

Figure 2

Ultrasound (US) images of the anterior, medial, lateral and posterior regions at the Ant 1, Med 1, Lat 1 and Post 1 level. (a) US imaging. (b) US imaging detailed

Figure 3

Histological thicknesses of the fascial layers of the thigh. D.F., Deep Fascia; S.F., Superficial Fascia; ANT, anterior; MED, medial; LAT, lateral; POST, posterior

Figure 4

US thicknesses (mm) of the superficial fascia of the thigh in various regions and levels. Ant, anterior; Med, medial, Lat, lateral; Posterior, posterior

Figure 5

US thicknesses (mm) of the fascia lata in various regions and levels. Ant, anterior; Med, medial; Lat, lateral; Posterior, posterior

Figure 6

The correlation between the mean histological (from 20 to 40 measurements) and ultrasound (40 measurements) thicknesses (mm) of the superficial and deep fascia in various regions/levels (n = 8). Pearson (r) = 0.918; p < 0.01