title: Marked innervation but also signs of nerve degeneration in between the Achilles and plantaris tendons and presence of innervation within the plantaris tendon in midportion Achilles tendinopathy.
abstract: OBJECTIVE
  The plantaris tendon is increasingly recognised as an important factor in midportion Achilles tendinopathy. Its innervation pattern is completely unknown.
  
  
  METHODS
  Plantaris tendons (n=56) and associated peritendinous tissue from 46 patients with midportion Achilles tendinopathy and where the plantaris tendon was closely related to the Achilles tendon were evaluated. Morphological evaluations and stainings for nerve markers [general (PGP9.5), sensory (CGRP), sympathetic (TH)], glutamate NMDA receptor and Schwann cells (S-100β) were made.
  
  
  RESULTS
  A marked innervation, as evidenced by evaluation for PGP9.5 reactions, occurred in the peritendinous tissue located between the plantaris and Achilles tendons. It contained sensory and to some extent sympathetic and NMDAR1-positive axons. There was also an innervation in the zones of connective tissue within the plantaris tendons. Interestingly, some of the nerve fascicles showed a partial lack of axonal reactions.
  
  
  CONCLUSIONS
  New information on the innervation patterns for the plantaris tendon in situations with midportion Achilles tendinopathy has here been obtained. The peritendinous tissue was found to be markedly innervated and there was also innervation within the plantaris tendon. Furthermore, axonal degeneration is likely to occur. Both features should be further taken into account when considering the relationship between the nervous system and tendinopathy.
authors.affiliation: Department of Integrative Medical Biology (IMB), Anatomy Section, Umeå University, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Spang
authors.affiliation: Department of Integrative Medical Biology (IMB), Anatomy Section, Umeå University, Sweden.
authors.forename: V M
authors.initials: VM
authors.lastname: Harandi
authors.affiliation: Department of Community Medicine and Rehabilitation, Umeå University, Sweden.|Pure Sports Medicine Clinic, London, UK.|ISEH, UCLH, London, UK.
authors.forename: H
authors.initials: H
authors.lastname: Alfredson
authors.affiliation: Department of Integrative Medical Biology (IMB), Anatomy Section, Umeå University, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Forsgren
mesh_terms: D000125:Achilles Tendon / Q000294:innervation* / Q000473:pathology* / Q000601:surgery; D000320:Adrenergic Fibers / Q000473:pathology; D000328:Adult; D000368:Aged; D001369:Axons / Q000473:pathology; D015415:Biomarkers; D003238:Connective Tissue / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration / Q000235:genetics / Q000473:pathology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D011984:Sensory Receptor Cells / Q000473:pathology; D052256:Tendinopathy / Q000235:genetics / Q000473:pathology* / Q000601:surgery; D043222:Ubiquitin Thiolesterase / Q000235:genetics / Q000378:metabolism
chemical_list: D015415:Biomarkers; D016194:Receptors, N-Methyl-D-Aspartate; C482860:UCHL1 protein, human; D043222:Ubiquitin Thiolesterase