# Ultrasound Elastography in the Evaluations of Tendon-Related Disorders--A Systematic Review
## 4 Discussion
### Discussion
Similar findings can be found in the analysis of the long-head biceps tendon (LHBT): [PERSON] [27] found that chronically pathological long-head biceps tendon (identified with pain and MRI examination) becomes stiffer compared to the same tendons in a control group using both shear wave elastography and strain elastography evaluations. In this case, we must consider that some artifacts may be involved [67]. In fact, it is known that during a pathological process, while tendons become softer, joint capsules and ligaments become stiffer [68]. The LHBT takes part in shoulder stability; it is included in the rotator cuff and has an extra-synovial part and an intra-synovial part that runs under the shoulder capsule. When the LHBT is analyzed, it is nearly impossible to isolate the tendon from the capsule tissue. Therefore, in the US elastography analysis of the LHBT, the stiffness of the shoulder capsule must be considered to properly understand the results [69]. However, by comparing the diagnostic utility of US, shear wave elastography, and strain elastography to MRI, it was concluded that US elastography is a useful diagnostic tool for LHBT tendinopathy when considering usability, cost-effectiveness, and patient preference compared to MRI. Among the included studies, biceps tendonopathy is also considered by [PERSON] [35]. They did not specify any strain elastography results data about tendon stiffness but concluded that US elastography has a positive correlation with US images. Other frequently analyzed tendons in the review are the Achilles tendon, supraspinatus tendon, common extensor, and common flexor tendons. The Achilles tendon has been taken into consideration by [PERSON] [22; 29; 32; 33; 37; 50; 54; 56; 59; 60]. Most of these studies [22; 29; 34; 37; 54; 56; 60] found that symptomatic Achilles tendon is softer than healthy tendons and asymptomatic tendons. They also reported good to excellent sensitivity and specificity in the diagnosis of Achilles tendinopathy using both strain elastography and shear wave elastography techniques. [PERSON] [37] did not provide SE results data but found out that it could identify tendinopathy features in 27/35 patients with suspected pathologic tendons with negative US examination [37]. [PERSON] et al. [32] divided the Achilles tendon into insertional and mid-parts. Even if the tendon thickness was greater in symptomatic patients than in controls, in both mid- and insertional Achilles, the shear wave elastography analysis revealed that stiffness was very similar at the midportion and slightly greater in symptomatic tendons at the insertional area. The paper of [PERSON] et al. [50] is in agreement with the previous one, supporting that in insertional Achilles tendinopathy (IAT), tendons' compressive modulus increases compared with healthy controls, indicating an intrinsically more rigid tissue. This outcome is due to the fact that at the Achilles tendon insertion, in patients with IAT, increased cartilage matrix proteins (type 2 collagen and aggrecan) and rounder tendon cells can be found, suggesting a metaplastic phenomenon. It is worth mentioning that this paper is the only one analyzing the Achilles tendon with the patient actively moving (active dorsiflexion, standing, and partial squat) [50]. The other paper in contrast with expectations is the one from [PERSON] and colleagues [59], which found the painful Achilles tendon to be harder with respect to pain-free controls. Findings related to the insertional part of the tendon are controversial since other papers discovered that symptomatic tendons are globally softer than healthy controls [61]. This fact can also be due to the overlapping of muscle and tendon tissues in the explored region. Further studies in this field are needed since there is no unambiguous judgment about sensitivity and specificity and on whether maturation, aging, or chronic load underlies these findings. We assume that the limitations of ultrasound imaging play a primary role in generating this variety of results.