Cadaveric study of the anatomical and histological relationships between the Achilles and plantaris tendons

Abstract

RationaleThe purpose of this study was to investigate whether the proximity in anatomical locations of the Achilles (AT) and plantaris (PT) tendons promotes histopathological changes common to both tendons and their shared paratenon. The Achilles and plantaris tendons (ATs and PTs, respectively) share close anatomical locations in the foreleg, which has led to a proposed association between pathological findings in these tendons. Previous studies have identified such an association in specimens with known tendinopathy. This study aimed to determine whether similar correlation could be found in a group of cadavers without any record of tendon pathology.Materials and methodsThe subjects in this study were 20 donor cadavers (11 females and nine males) fixated in formalin, provided by the Department of Anatomy at Midwestern University. The mean age was 81 (±12). Twenty left, and 19 right legs were dissected. The ATs and PTs were assessed based on their gross anatomical characteristics, then samples of the tendons were harvested from two sites, one where the ATs and PTs ran closely together and a second where the PT was unassociated with the AT. The collected specimens were fixed, processed for paraffin embedding, sectioned, and stained with hematoxylin and eosin for histological analysis. Tissues were examined for the presence of inflammatory cells and for the evidence of stress‐induced conversion of the tendons’ dense connective tissue into fibrocartilage.ResultsIn four specimens (10.2%) the ATs and PTs ran separately, in eight (20.5%) specimens they were fused, and in three specimens the plantaris muscle was absent (7.7%). In the rest of the specimens the ATs and PTs were closely associated, but not fused. Histologically, no distinct evidence of inflammation was found at either the related or unrelated AT and PT sites. A presence of fibrocartilage with chondrocytes within the AT was noted in six (15.4%) specimens.ConclusionThe results of this study did not demonstrate any significant histopathologic changes in the areas of close contact between the ATs and PTs. The presence of fibrocartilage in the Achilles but not in the plantaris tendons suggests that the AT may be more affected by compression‐induced stress than the PT. These findings suggest that within the control group, close contact between AT and PT does not result in interrelated histopathologic changes. However, it is possible that histopathology may be observed in patients with mid‐portion Achilles tendinopathy.Support or Funding InformationZachary Belford and Benjamin Ferrel were supported by the Midwestern University Research Fellowship Program. Eric Leland and Andrew Cheung were supported by the Midwestern University work‐study program.