Botulinum toxin effects on gasatrocnemius strength and plantar pressure in diabetics with peripheral neuropathy and forefoot ulceration.
BACKGROUND
High forefoot plantar pressure is associated with plantar ulcers in people with diabetes and peripheral neuropathy. The purpose of this pilot study was to determine the safety and efficacy of botulinum toxin A injected into the gastrocnemius-soleus muscles to reduce muscle strength and plantar pressure.


METHODS
This double blind, randomized clinical trial studied 17 people with diabetes mellitus, peripheral neuropathy and a forefoot plantar ulcer. Subjects were randomized into one of three groups receiving gastrocnemius-soleus muscle injections on the involved side with; 1) Saline (n = 5, weight =99± 21 kg), 2) 200-units of Botox® (n = 7, weight = 101± 5 kg), or 3) 300-units of Botox® (n = 5, weight = 129± 22 kg). Botox® dose was converted to units/kg, the majority received between 1.9 and 2.4 units/kg (n = 11) and one 3.2 units/kg. Plantarflexor peak torque and forefoot peak plantar pressure were quantified prior and 2 weeks post-injection.


RESULTS
There were no complications from the injections. Plantarflexor peak torque on the involved side increased in the placebo and 300 groups (3± 4 Nm and 6± 10 Nm, respectively) and decreased -8± 11 Nm in the 200 group. There was no relationship between units/kg of Botox® for each subject and change in plantarflexor peak torque. Forefoot peak plantar pressure did not change in the placebo and 300 groups (0± 11 and 0± 5 N/cm(2), respectively) and decreased -4± 16 N/cm2 (4%) for the 200 group.


CONCLUSIONS
There were no adverse events associated with the Botox® injections. This study was unable to determine the dose to consistently reduce plantarflexor strength and forefoot plantar pressure. Additional research is needed to investigate diabetes mellitus specific physiological changes and their impact of BoNT-A effectiveness in order to guide appropriate dosing.
Washington University School of Medicine, St. Louis, MO 63108-2212, USA. hastingsmk@wustl.edu
Mary K
MK
Hastings
Michael J
MJ
Mueller
David R
DR
Sinacore
Michael J
MJ
Strube
Beth E
BE
Crowner
Jeffrey E
JE
Johnson
Brad R
BR
Racette
D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D017719:Diabetic Foot / Q000503:physiopathology / Q000517:prevention & control*; D003929:Diabetic Neuropathies / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005545:Forefoot, Human / Q000503:physiopathology; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D010865:Pilot Projects; D011312:Pressure; D011446:Prospective Studies
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A