Is Botulinum Toxin Type A a Valuable Adjunct During Femoral Lengthening? A Randomized Trial.

Abstract

Reduced joint ROM and distraction-induced pain are common complaints of patients who have undergone gradual femoral lengthening. Attempts to reduce the effects of lengthening on joint motion have included the use of botulinum toxin to reduce the muscle forces that restrict motion. The benefits of this approach during femoral lengthening, however, have not been conclusively established. We wished to evaluate the effects of botulinum toxin type A (BtX-A) injection in the anterior thigh muscles during femoral distraction osteogenesis on adjacent joint ROM and distraction-induced pain. We asked: (1) Does injection of BtX-A in the quadriceps muscles lead to improved knee and hip motion during femoral lengthening? (2) Does injection of BtX-A reduce pain during femoral lengthening? A single-center, double-blind, randomized placebo-controlled trial was conducted. Forty-four patients (88 femurs) undergoing bilateral femoral lengthening for familial short stature were included in the study. BtX-A (200 IU) was injected intraoperatively in the quadriceps muscles of one thigh. An equal volume of sterile normal saline was injected in the other thigh as a control. Selection of the limb receiving the toxin was randomized. Clinical evaluation included a VAS score for pain measurement, ROM evaluation of the hips and knees, and measurement of thigh circumference. Side-to-side differences were analyzed throughout the entire consolidation phase. No patients were lost to followup, leaving 44 patients (88 femurs). The mean followup was 26 months (range, 14-40 months). The distraction rate and final length of gain were similar between treated and control limbs. A priori power analysis suggested that 44 legs were required in each group to achieve statistical significance of 0.05 with 90% power to detect a 50% difference in treatment effect between treatment and control groups. There were no differences in hip ROM, knee ROM, or maximal thigh circumference between the two lower extremities at any time during the study period. VAS scores were no different between the patients who received BtX-A and those who received saline. Local injection of 200 IU BtX-A in the quadriceps muscles does not appear to reduce distraction-induced pain nor enhance ROM in the hip or knee during femoral lengthening. Additional studies are needed to evaluate the effect of larger doses or different injection methods. Based on our findings, we do not recommend routine use of botulinum injections during limb lengthening and believe any further use of this drug should only be in the context of a controlled trial. Level II, therapeutic study.