Background: Differential motion between the plantaris and Achilles tendons has been hypothesized to contribute to pain in some patients presenting with Achilles tendinopathy. However, objective evidence of differential Achilles-plantaris motion is currently lacking from the literature.
Objective: To determine whether differential, multidirectional motion exists between the plantaris tendon (PT) and Achilles tendon (AT) as documented by dynamic ultrasound (US) and postdissection examination in an unembalmed cadaveric model.
Design: Prospective, cadaveric laboratory investigation.
Setting: Procedural skills laboratory in a tertiary medical center.
Subjects: Twenty unembalmed knee-ankle-foot specimens (9 right, 11 left) obtained from 6 male and 10 female donors ages 55-96 years (mean 80 years) with body mass indices of 14.1-33.2 kg/m2 (mean 22.5 kg/m2).
Methods: A single, experienced operator used high-resolution dynamic US to qualitatively document differential PT-AT motion during passive ankle dorsiflexion-plantarflexion. Specimens were then dissected and passive dorsiflexion-plantarflexion was repeated while differential PT-AT motion was visualized directly.
Main outcome measurements: Presence or absence of multidirectional differential PT-AT motion.
Results: All 20 specimens exhibited smooth but variable amplitude multidirectional differential PT-AT motion. Whereas US readily demonstrated medial-lateral and anterior-posterior PT motion relative to the AT, differential longitudinal motion was only appreciated on dissection and direct inspection. Many specimens exhibited partial or complete encasement of the PT between the gastrocnemius portion of the AT and the soleus aponeurosis.
Conclusion: Some degree of multidirectional differential PT-AT motion appears to be a normal phenomenon, and PT motion can be evaluated sonographically in both the medial-lateral and anterior-posterior directions. The existence of normal differential PT-AT motion suggests that alterations in PT motion or repetitive stress within the PT-AT interval may produce symptoms in some patients presenting with Achilles region pain syndromes. The PT should be evaluated in all patients presenting with Achilles, plantaris, or calf pain syndromes. Future research would benefit from the development of a sonographic classification system for PT anatomy and motion with the goal of differentiating normal versus pathologic states and identifying risk factors for symptom development.
Level of evidence: IV.
Copyright © 2017 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.