title: Botulinum Neurotoxin A injections influence stretching of the gastrocnemius muscle-tendon unit in an animal model.
abstract: Botulinum Neurotoxin A (BoNT-A) injections have been used for the treatment of muscle contractures and spasticity. This study assessed the influence of (BoNT-A) injections on passive biomechanical properties of the muscle-tendon unit. Mousegastrocnemius muscle (GC) was injected with BoNT-A (n = 18) or normal saline (n = 18) and passive, non-destructive, in vivo load relaxation experimentation was performed to examine how the muscle-tendon unit behaves after chemical denervation with BoNT-A. Injection of BoNT-A impaired passive muscle recovery (15% vs. 35% recovery to pre-stretching baseline, p < 0.05) and decreased GC stiffness (0.531 ± 0.061 N/mm vs. 0.780 ± 0.037 N/mm, p < 0.05) compared to saline controls. The successful use of BoNT-A injections as an adjunct to physical therapy may be in part attributed to the disruption of the stretch reflex; thereby modulating in vivo passive muscle properties. However, it is also possible that BoNT-A injection may alter the structure of skeletal muscle; thus modulating the in vivo passive biomechanical properties of the muscle-tendon unit.
authors.affiliation: UniversitätsKlinikum Heidelberg, Stiftung Orthopädische Universitätsklinik, Schlierbacher Landstrasse 200a, Heidelberg 69118, Germany. p.haubruck@gmx.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Haubruck
authors.forename: Sandeep
authors.initials: S
authors.lastname: Mannava
authors.forename: Johannes F
authors.initials: JF
authors.lastname: Plate
authors.forename: Michael F
authors.initials: MF
authors.lastname: Callahan
authors.forename: Walter F
authors.initials: WF
authors.lastname: Wiggins
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schmidmaier
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Tuohy
authors.forename: Katherine R
authors.initials: KR
authors.lastname: Saul
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Smith
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D004558:Electric Stimulation; D007273:Injections, Intramuscular; D008297:Male; D051379:Mice; D023421:Models, Animal; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D009465:Neuromuscular Agents / Q000494:pharmacology*; D012026:Reflex, Stretch / Q000187:drug effects*; D013710:Tendons / Q000187:drug effects* / Q000502:physiology
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A