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

Objectives: 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. Conclusion: 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.

[1]  G. Stellin,et al.  Expression and Distribution of the Adrenomedullin System in Newborn Human Thymus , 2014, PloS one.

[2]  H. Alfredson.  Where to now with Achilles tendon treatment? , 2011, British Journal of Sports Medicine.

[3]  R. Bahr,et al.  Glutamate receptors in tendinopathic patients , 2012, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[4]  M. Kvist.  Achilles Tendon Injuries in Athletes , 1994, Annales chirurgiae et gynaecologiae.

[5]  S. Forsgren,et al.  Is vasculo-neural ingrowth the cause of pain in chronic Achilles tendinosis? , 2003, Knee Surgery, Sports Traumatology, Arthroscopy.

[6]  A. Gad,et al.  Tendon pathology in long-standing achillodynia. Biopsy findings in 40 patients. , 1997, Acta orthopaedica Scandinavica.

[7]  VGluT2 and NMDAR1 Expression in Cells in the Inflammatory Infiltrates in Experimentally Induced Myositis: Evidence of Local Glutamate Signaling Suggests Autocrine/Paracrine Effects in an Overuse Injury Model , 2012, Inflammation.

[8]  J. Calder,et al.  Achilles tendinoscopy and plantaris tendon release and division in the treatment of non-insertional Achilles tendinopathy. , 2012, Foot and ankle surgery : official journal of the European Society of Foot and Ankle Surgeons.

[9]  S. Forsgren,et al.  Unilateral surgical treatment for patients with midportion Achilles tendinopathy may result in bilateral recovery , 2012, British Journal of Sports Medicine.

[10]  S. Forsgren,et al.  Distribution of general (PGP 9.5) and sensory (substance P/CGRP) innervations in the human patellar tendon , 2006, Knee Surgery, Sports Traumatology, Arthroscopy.

[11]  L. Engebretsen,et al.  Pronociceptive and Antinociceptive Neuromediators in Patellar Tendinopathy , 2006, The American journal of sports medicine.

[12]  S. Forsgren,et al.  Nerve-related characteristics of ventral paratendinous tissue in chronic Achilles tendinosis , 2007, Knee Surgery, Sports Traumatology, Arthroscopy.

[13]  M. Kjaer,et al.  What is the impact of inflammation on the critical interplay between mechanical signaling and biochemical changes in tendon matrix? , 2013, Journal of applied physiology.

[14]  H. Alfredson,et al.  Achilles tendinopathy—do plantaris tendon removal and Achilles tendon scraping improve tendon structure? A prospective study using ultrasound tissue characterisation , 2015, BMJ Open Sport & Exercise Medicine.

[15]  G. Kerkhoffs,et al.  Good outcome after stripping the plantaris tendon in patients with chronic mid-portion Achilles tendinopathy , 2011, Knee Surgery, Sports Traumatology, Arthroscopy.

[16]  R. Lorentzon,et al.  In situ microdialysis in tendon tissue: high levels of glutamate, but not prostaglandin E2 in chronic Achilles tendon pain , 1999, Knee Surgery, Sports Traumatology, Arthroscopy.

[17]  H. Alfredson.  Midportion Achilles tendinosis and the plantaris tendon , 2011, British Journal of Sports Medicine.

[18]  G. Kerkhoffs,et al.  The plantaris tendon and a potential role in mid‐portion Achilles tendinopathy: an observational anatomical study , 2011, Journal of anatomy.

[19]  M. Adams,et al.  The role of Plantaris Longus in Achilles tendinopathy: a biomechanical study. , 2011, Foot and ankle surgery : official journal of the European Society of Foot and Ankle Surgeons.

[20]  R. Lorentzon,et al.  Treatment of midportion Achilles tendinosis: similar clinical results with US and CD-guided surgery outside the tendon and sclerosing polidocanol injections , 2007, Knee Surgery, Sports Traumatology, Arthroscopy.

[21]  S. Forsgren,et al.  Immunohistochemical and in situ hybridization observations favor a local catecholamine production in the human Achilles tendon. , 2008, Histology and histopathology.

[22]  L. Arendt-Nielsen,et al.  Glutamate and capsaicin-induced pain, hyperalgesia and modulatory interactions in human tendon tissue , 2009, Experimental Brain Research.

[23]  A. Pearce,et al.  The Pain of Tendinopathy: Physiological or Pathophysiological? , 2013, Sports Medicine.

[24]  H. Alfredson,et al.  Major physical but also psychological effects after pain relief from surgical scraping in patients with Achilles tendinopathy—A 1-year follow-up study , 2014, PST 2014.

[25]  R. Straub,et al.  Achilles tendinosis is associated with sprouting of substance P positive nerve fibres , 2005, Annals of the rheumatic diseases.

[26]  Natasha Agabalyan,et al.  Tendinopathy – from basic science to treatment. , 2013, International journal of experimental pathology.

[27]  R. Lorentzon,et al.  Glutamate NMDAR1 receptors localised to nerves in human Achilles tendons. Implications for treatment? , 2001, Knee Surgery, Sports Traumatology, Arthroscopy.

[28]  L. Engebretsen,et al.  Coexistence of up‐regulated NMDA receptor 1 and glutamate on nerves, vessels and transformed tenocytes in tendinopathy , 2009, Scandinavian journal of medicine & science in sports.

[29]  J. Cook,et al.  Is compressive load a factor in the development of tendinopathy? , 2011, British Journal of Sports Medicine.

[30]  P. Kannus,et al.  Achilles tendon disorders: etiology and epidemiology. , 2005, Foot and ankle clinics.

[31]  J. Cook,et al.  The challenge of managing tendinopathy in competing athletes , 2013, British Journal of Sports Medicine.

[32]  J. Bagge,et al.  The plantaris tendon in association with mid-portion Achilles tendinosis: tendinosis-like morphological features and presence of a non-neuronal cholinergic system. , 2013, Histology and histopathology.

[33]  S. Forsgren,et al.  The innervation pattern of the human Achilles tendon: studies of the normal and tendinosis tendon with markers for general and sensory innervation , 2005, Cell and Tissue Research.