The Twist of the Achilles Tendon – Associations of Torsions in the Lower Extremity

Abstract

Achilles tendinopathy and rupture of the Achilles tendon (AT) are frequent pathologies. Even though they may be associated with the twisted morphology of the AT, quantitative data on the extent of the twist of the entire AT are not available. The aim of this study was to investigate the torsion of the AT based on its individual parts and to evaluate a possible correlation with the torsion of the long bones of the lower extremity. Forty embalmed lower extremities were included in this study. The lateral deviation of the AT and its torsional angle as well as the angles of the individual parts in trans-section were measured. Thereafter, the torsions of femur and tibia were evaluated. Measuring the lateral deviation of the fibers resulted in an average torsion of the AT of 34.59° (SD 16.8°). The angles of the different parts of the AT in trans-section resulted in a median AT torsion of 15.73°, showing various patterns of rotations of the individual muscles. A statistically significant correlation between the torsions of the lower extremity and the AT (P =0.0242, r = 0.40) as well as a correlation between the femoral torsion and the AT torsion (P = 0.0127, r = 0.44) were found. This study adds to the morphological understanding of the torsion of the AT and its correlation with the torsions of the long bones of the lower extremity. Especially, the torsion of the femur seems to be connected to the torsion of the tendon. Clin. Anat. 31:1085-1091, 2018. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Distribution of the subtendons in the midportion of the Achilles tendon revealed in vivo on MRI

“…On the other hand, counting only superficial fibers orientation may lead to misinterpretation of the tendon rotation. The results of our study are comparable only with the work published Prosenz et al 21 , where the internal structure of the subtendons was examined. A solution could be the use of ultra-thin MRI sections of the Achilles tendon, which is not routinely used clinically.…”

“…Most of the previous studies assessing the internal structure of the Achilles tenon were conducted on cadavers 4 , 5 , 16 – 20 and very few in ultrasound 8 . We think that our study is necessary due to the fact that MRI is a modern method of imaging the musculoskeletal and an excellent tool for assessing the Achilles tendon anatomy 4 , 5 , 21 . We noticed that the possibility of identifying the subtendons on MRI is not as clear as during an anatomical dissection and classical anatomy of the Achilles tendon is significantly different from then radiological anatomy.…”

“…This difference may be due to the fact that the MRI examination showed poor fiber rotation within the subtendon, whereas the configuration of superficial fibers is clearly visible on gross anatomy specimens. This is probably also the reason for the inability to compare with the results of previous anatomical studies [19][20][21] . Several anatomical studies have shown different degrees of the Achilles tendon twist structure, but there are no studies assessing the tendon twist on MRI.…”

“…We noticed that the possibility of identifying the subtendons on MRI is not as clear as during an anatomical dissection and classical anatomy of the Achilles tendon is significantly different from then radiological anatomy. Identification of the subtendons of the Achilles tendon on MRI depends on the presence of narrow high-signal septations between the subtendons 21 and the ability to identify is partly dependent on the reviewer. No large-scale MRI studies such as this have been previously reported.…”

“…In occasional anatomical studies, variability in the degree of tendon torsion was observed, separating the types of torsion variability 19,21 . In our material we did not find cases where only one subtendon formed the anterior outline of the Achilles tendon, which was revealed by some authors 17 .…”