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Extracorporeal shockwave therapy diminishes axonal regeneration following repair of the rat median nerve with muscle-in-vein conduits but not after autologous nerve grafting
Johannes C. Heinzel, Dr. med.1,2,3; Viola Oberhauser, medical student2,4; Claudia Keibl, Dr. med. vet.2,4; Barbara Schädl, Mag.2,4,5; Nicole Swiadek, M. Sc.2,6; Gregor Längle, Dr. med. univ.2,6; Helen Frick, medical student2,6; Cyrill Slezak, PhD2,6,7; Cosima Prahm,. PhD1; Johannes Grillari, Prof. Dr.2,6,8; Jonas Kolbenschlag, Prof. Dr. med.1; David Hercher, Ph. D.2,6
1University of Tübingen, Tübingen, Germany; 2Austrian Cluster for Tissue Regeneration, Vienna, Austria; 3Ludwig Boltzmann Institut for Traumatology - The research center in cooperation with AUVA, Vienna, Austria; 4Ludwig Boltzmann Institute for Traumatology - The research center in cooperation with AUVA, Vienna, Austria; 5Medical University of Vienna, Vienna, Austria; 6Ludwig Boltzmann Institut for Traumatology The research center in cooperation with AUVA, Vienna, Austria; 7Utah Valley University, Orem, UT; 8BOKU – University of Natural Re- Resources and Life Sciences Vienna, Vienna, Austria

Background: Investigations reporting positive effects of Extracorporeal Shock Wave Therapy (ESWT) on nerve regeneration are limited to the rat sciatic nerve model. The effects of ESWT on muscle-in-vein conduits (MVCs) have also not been investigated yet. This study aimed to evaluate the effects of ESWT after repair of the rat median nerve with either autografts (ANGs) or MVCs.
Methods: In 56 male Lewis rats, a 7-mm segment of the right median nerve was reconstructed either with an ANG or MVC. For each reconstructive technique, one group of animals received one application of ESWT (OP 155 connected to Orthogold 100, MTS Medical, Konstanz, Germany) while the other rats served as controls. Focused application of ESWT was facilitated by use of a 3D-printed customized device. Animals were observed for 12 weeks and nerve regeneration was assessed via computerized gait analysis, the grasping test, electrophysiological evaluations and histological quantification of axons, blood vessels and lymphatic vasculature.
Results: Functional recovery as assessed by the grasping test occurred fastest in the ANG and ANG+ESWT group but the test’s validity was hampered because the animals lacked motivation to participate in the procedure. Eight weeks postoperatively, rats of the ANG+ESWT group had a significantly (p<0.05) higher Paw Print Width than those in the MVC group. Compound muscle action potential amplitudes of the flexor digitorum superficialis muscle were significantly (p<0.05) higher in the ANG+ESWT group when compared to the MVC+ESWT group. Proximal nerve segments in the MVC+ESWT group contained statistically significant (p<0.05) lower axon numbers (1184 ± 321) as compared to MVCs which received no additional treatment (4683 ± 624). The number of blood vessels at the mid-graft level in the ANG group (101 ±21) was significantly higher (p<0.05) than in the MVC+ESWT group (17 ±5). Statistically significant (p<0.05) differences in lymphatic vessel counts could be identified between the distal nerve segments of ANG+ESWT (0) and MVC-treated (5.00 ±1.60) animals.
Conclusion: Here we provide for the first time a comprehensive analysis of ESWT effects on nerve regeneration in a rat model of median nerve injury. Furthermore, this study is among the first reporting the quantification of lymphatic vessels following peripheral nerve injury and reconstruction in vivo. We found no significant direct positive effects of ESWT on autografts but instead detected significant negative effects on nerve regeneration through MVCs. Additionally, results following nerve repair with MVCs were significantly inferior to those after ANG repair in general.


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