Background: Botulinum toxin A (BoNT-A) is used in the treatment of muscle hypertrophy but has never been used in chronic exertional compartment syndrome (CECS). The objective diagnostic criterion in this condition is an abnormally elevated intramuscular pressure (IMP) in the compartment. In this study, the IMP was measured 1 minute (P1) and 5 minutes (P5) after the exercise was stopped before and after BoNT-A injection.
Hypothesis: Botulinum toxin A reduces the IMP (P1 and P5) and eliminates the pain associated with CECS.
Study design: Case series; Level of evidence, 4.
Methods: Botulinum toxin A was injected into the muscles of moderately trained patients with an anterior or anterolateral exertional compartment syndrome of the leg. The BoNT-A dose (mean ± SD) ranged from 76 ± 7 to 108 ± 10 U per muscle, depending on which of the 5 muscles in the 2 compartments were injected. The primary end point was IMP (P1, P5). Secondary end points were exertional pain, muscle strength, and safety. Follow-up was conducted up to 9 months.
Results: A total of 25 anterior compartments and 17 lateral compartments were injected in 16 patients. The time interval (mean ± SD) between the BoNT-A injection and after BoNT-A injection IMP measurement was 4.4 ± 1.6 months (range, 3-9 months). In the anterior compartment, P1 and P5 fell by 63% ± 17% (P < .00001) and 59% ± 24% (P < .0001), respectively; in the lateral compartment, P1 and P5 fell by 68% ± 21% (P < .001) and 63% ± 21% (P < .01), respectively. Exertional pain and muscle strength were monitored, based on the Medical Research Council score. The exertional pain was completely eliminated in 15 patients (94%). In 5 patients (31%), the strength of the injected muscles remained normal. In 11 patients (69%), strength decreased from 4.5 (out of 5) to 3.5 (P < .01), although without functional consequences. In the conditions of this study, BoNT-A showed a good safety profile in patients with CECS.
Conclusion: In this case series, BoNT-A reduced the IMP and eliminated exertional pain in anterior or anterolateral CECS of the leg for up to 9 months after the intervention. The mode of action of BoNT-A is still unclear. A randomized controlled study should be carried out to determine whether BoNT-A can be used as a medical alternative to surgical treatment.
Keywords: botulinum toxin; exertional compartment syndrome; intramuscular pressure; leg pain.