Achilles Tendon

Sonography has been used frequently in the investigation of the Achilles tendon pathology, including diagnosis of tendinopathy, partial tears, complete tears, and post-treatment follow-up [41-47]. The Achilles is the most frequent ankle tendon injured, and its evaluation was one of the earliest applications of musculoskeletal sonography [41].

The sonographic findings of tendinopathy are focal or diffuse thickening, with focal hypoechoic areas within the normally echogenic Achilles tendon (Fig. 16) [42,43]. The tendon thickness may range from 7 mm to 16 mm in patients who have the clinical diagnosis of tendinopathy [47]. Neovascularization of the Achilles tendon is seen with color and power Doppler imaging in areas with tendinopathy (Fig. 17) [48,49]. Although neovascularization has a strong correlation with pain, it does not indicate an unfavorable outcome [50].

Fig. 15. Organizing hematoma. (A) Longitudinal extended field of view image of the medial calf show a heterogeneous hypoechoic fluid collection in the superficial soft tissues (arrows). (B) Transverse color Doppler image shows this hematoma without associated flow.

Fig. 15. Organizing hematoma. (A) Longitudinal extended field of view image of the medial calf show a heterogeneous hypoechoic fluid collection in the superficial soft tissues (arrows). (B) Transverse color Doppler image shows this hematoma without associated flow.

Organized Hematoma Soft Tissues

Fig. 16. Achilles tendinopathy. (A) Longitudinal extended field of view and (B) longitudinal sonographic images of the Achilles tendon show a thickened hypoechoic tendon (large arrows). Small arrow (A), calcaneus. (C) Transverse image better defines the loss of the normal echogenic appearance of the tendon with heterogeneity and thickening (arrow).

Fig. 16. Achilles tendinopathy. (A) Longitudinal extended field of view and (B) longitudinal sonographic images of the Achilles tendon show a thickened hypoechoic tendon (large arrows). Small arrow (A), calcaneus. (C) Transverse image better defines the loss of the normal echogenic appearance of the tendon with heterogeneity and thickening (arrow).

Comparison of sonography and MRI in 27 histologically verified cases of chronic Achilles tendinopathy found similar accuracy for both modalities [43].

The sonographic and MRI findings of a partial-thickness tear may overlap with the findings of tendinopathy, and can make differentiation between the two entities difficult with both modalities. The authors have found that the best sonographic sign of a partial-thickness tear is a hypoechoic line extending from the periphery into the tendon substance (Fig. 18). Paavola and colleagues [51] found that they could preoperatively diagnose 8 of 11 partial-thickness tears. In another study, an accuracy of 95% [52] was reported in the use of sonography for the diagnosis of partial-thickness tears.

Longitudinal Tear The Achilles
Fig. 17. Increased Doppler flow in Achilles tendinopathy. Transverse image of the Achilles tendon show a thickened tendon with areas of increased hypervascularity. This patient did not have an associated tear.
Stress Fracture Achilles Tendon

Fig. 18. Partial tear of the Achilles. (A) Longitudinal sonographic image of the distal Achilles tendon demonstrates a thickened tendon with hypoechoic areas with associated hypervascu-larity (arrows). (B,C,D). Transverse images show a heterogeneously appearing tendon with a focal hypoechoic cleft (C,D, arrows) which extends to the surface with associated color flow, representing a partial tear of the Achilles tendon with underlying tendinopathy.

Fig. 18. Partial tear of the Achilles. (A) Longitudinal sonographic image of the distal Achilles tendon demonstrates a thickened tendon with hypoechoic areas with associated hypervascu-larity (arrows). (B,C,D). Transverse images show a heterogeneously appearing tendon with a focal hypoechoic cleft (C,D, arrows) which extends to the surface with associated color flow, representing a partial tear of the Achilles tendon with underlying tendinopathy.

The sonographic findings of a complete tear include marked distortion of the normal fibrillar tendon architecture, a gap between the torn tendon ends, and hematoma or fluid collection in and around the rupture site (Fig. 19) [45,53]. The degree of retraction of a torn Achilles tendon is best assessed on longitudinal images. Color Doppler can demonstrate focal hyperemia in acutely torn tendon's ends [45]. The value of sonography was documented in 26 surgical

Stress Fracture Achilles Tendon

Fig. 19. Complete Achilles tendon tear. (A,B) Longitudinal sonographic images of the Achilles tendon show a complete tear. Large arrows (A,B), proximal tendon end; notched arrows (A,B), distal tendon end; thin arrow (A), gap filled with hematoma. Note the tendon ends closely opposed during plantar flexion (B).

Fig. 19. Complete Achilles tendon tear. (A,B) Longitudinal sonographic images of the Achilles tendon show a complete tear. Large arrows (A,B), proximal tendon end; notched arrows (A,B), distal tendon end; thin arrow (A), gap filled with hematoma. Note the tendon ends closely opposed during plantar flexion (B).

cases with comparison of the sonographic findings of full-thickness versus partial-thickness tears [46]. In another study, sonography differentiated a full-thickness tear from a partial-thickness tear or tendinopathy of the Achilles tendon with 92% accuracy [46]. Nonsurgically and surgically treated Achilles tendon rupture can also be followed for the extent of healing using sonography [44,45].

Calcification within the Achilles can be documented with sonography, along with the extent of adjacent tendinopathy. Calcification is echogenic, and may demonstrate posterior acoustic shadowing (Fig. 20). MRI often underestimates tendon calcification, because the low signal intensity of calcium may not be detectable within the low signal intensity of the tendon [54].

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