Botulinum toxin a does not decrease calf pain or improve ROM during limb lengthening: a randomized trial.

Abstract

During lower limb lengthening, distraction-induced muscle pain and surrounding joint contractures are frustrating complications for which few effective treatments are available. We evaluated Botulinum Toxin Type A (BtX-A) injection in the calf muscles during human tibial distraction osteogenesis. We hypothesized that it may decrease calf pain and increase ROM of the surrounding joints by reducing muscle stiffness. Between April 2010 and January 2011, we evaluated 36 patients undergoing bilateral tibia lengthening who met prespecified inclusion criteria. All patients underwent stature lengthening with lengthening over a nail or lengthening and then nailing. BtX-A (200IU) was injected at the calf muscle only in one leg for each patient and the same amount of sterile normal saline was injected into the other leg as a control. Selection of the leg receiving the toxin was randomized. Clinical evaluation included a VAS score for calf pain and measurement of ROM of the knees and ankles and calf circumference, with evaluations performed in a double-blinded manner. Side-to-side differences were analyzed until the end of consolidation phase. Minimum followup was 24months (mean, 30months; range, 24-39months). The distraction rate and the final length gain were similar in the treated and control limbs. A priori power analysis suggested that 34 legs were required to achieve statistical significance of 0.05 with 80% of power to detect a 50% difference in treatment effect between treatment and control groups. There were no differences in calf pain, knee and ankle ROM, and maximal calf circumferences between the two legs at each time point. Local injection of 200IU BtX-A at the human calf muscle does not appear to reduce calf pain or help enhance ROM of the knee and ankle during tibial lengthening. However, the small sample size provided sufficient power to detect only relatively large clinical effects; future, larger trials will be needed to determine whether smaller differences are present. Level II, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.