Linear hypertrophic scar is a common surgical problem that can be difficult to manage, especially for the median sternotomy scar. Despite high demand for the early intervention to prevent and treat surgical scars, there is yet no universal consensus on satisfactory treatment. Botulinum toxin type A is a neurotoxin that has been widely and safely used in medicine for more than 30 years. It induces chemodenervation through acting on the presynaptic neuron to prevent release of acetylcholine, which leads to functional denervation of striated muscle for about 6 months after injection. The aim of this randomized controlled trial is to evaluate the efficacy of Botulinum toxin type A as a prophylactic treatment in the early postoperative of median sternotomy for the purpose of preventing excess scar formation.

The goal of this study is to conduct a randomized controlled trial about using Botulinum toxin type A ( BTA) to prevent hypertrophic scar in median sternotomy wound. The entire median sternotomy wound was divided into the upper half and the lower half. Both halves of the wound were randomized to receive treatment with either BTA or 0.9% normal saline. The patient and the surgeon will be blinded to the treatment arm. The primary end point was the evaluation of upper and lower half scar using the Vancouver Scar Scale (VSS). At 6 months follow-up, two blinded dermatologists examined the patients and took photographs of the scar in the outpatient clinic of XiJing Hospital. Scars were assessed using the VSS and assigned the mean score of the two observers. At 6-month follow-up, ultrasonography to measure the scar width will be performed. At the same time, patients were asked to evaluate their overall satisfaction, using a four-point grading scale for each half the scar(1= very satisfied, 2= satisfied,3= slightly satisfied, 4= unsatisfied ).Paired t-test was used to compare the VSS scores, scar width and the overall satisfaction between the BTA-treated group and normal saline group.

Inclusion Criteria:

• Patients included are older than 18 years with a median sternotomy less than 14 days.
• Patients are willing and able to participate in the study as an outpatient, making several visits to the study center during the treatment and follow-up periods.
• Patients can comply with all study requirements including concomitant medication and other treatment restrictions.
• Patients have good wound healing condition, without infection sign.

Exclusion Criteria:

• The exclusion criteria applied is current pregnancy or breast feeding, allergy to botulinum toxin type A, previous injection of botulinum toxin within 6 months prior to enrollment, Myasthenia gravis or other neuromuscular disorder,and refusal to participate in this trial.