The plantaris tendon in association with mid-portion Achilles tendinosis Tendinosis-like morphological features and presence of a non-neuronal cholinergic system
Christoph Spang1, Håkan Alfredson2, Mark Ferguson3, Beverley Roos3, Johan Bagge1 and Sture Forsgren1
1Department of Integrative Medical Biology, Anatomy Section, Umeå University, 2Department of Surgical and Perioperative Sciences, Sports Medicine, Umeå University and 3Centre for Sports Medicine and Orthopaedics, Rosebank Johannesburg, South Africa.
Offprint requests to: S. Forsgren M.D, Ph.D., Department of Integrative Medical Biology, Anatomy Section, Umeå University, SE-901 87 Umeå , Sweden. e-mail: Sture.Forsgren@Anatomy.umu.se
Summary. The plantaris tendon is often neglected in morphological/clinical studies on the lower extremity. There is, however, clinical evidence that the plantaris tendon is involved in cases with Achilles midportion tendinopathy/tendinosis. It is nevertheless unclear if the plantaris tendon exhibits tendinosis-like features in this situation. We therefore investigated the plantaris tendon of patients with midportion Achilles tendinosis when the plantaris tendon was found to be located very close to or invaginated into the Achilles tendon, a situation which very often has been found to be the case. There was a very large number of tenocytes in the tendon tissue and the tenocytes showed abnormal and irregular appearances, exhibiting widened/rounded and wavy appearances, and were frequently lined up in rows. These features are characteristic features in Achilles tendinosis tendons. The tendon cells showed a distinct immunoreaction for the acetylcholine (ACh) -producing enzyme choline acetyltransferase (ChAT). Frequent fibroblasts were found in the loose connective tissue and these cells also showed a marked ChAT immuno-reaction. The study shows that the plantaris tendon is morphologically affected in a similar way to the Achilles tendon in cases with midportion Achilles tendinosis and medial pain. The plantaris tendon may accordingly be a co-factor in these cases. The results also favour that there is a local ACh production both within the tendon tissue of the plantaris tendon and in the loose connective tissue. In conclusion, it is evident that plantaris tendons lying invaginated into or very close to the Achilles tendon in cases with midportion Achilles tendinosis show similar tendinosis features as previously shown for the Achilles tendon itself in these cases. Histol Histopathol 28, 623-632 (2013)
Key words: Plantaris tendon, Achilles tendon, Tendinopathy, Tenocyte morphology, Cholinergic, Choline acetyltransferase