Effect of Preoperative Botulinum Toxin A on Pain and Opioid Consumption After Bilateral Sagittal Split Osteotomy

Postoperative pain management due to muscular tension and spasm following mandibular advancement surgery can be clinically challenging. Botulinum toxin type A (BoNT-A) has demonstrated analgesic and muscle-relaxant properties in various medical applications, but its role in acute postoperative pain control in orthognathic procedures remains unclear.

The purpose of this study was to evaluate whether preoperative BoNT-A injections into the temporalis and masseter muscles reduce postoperative pain intensity and muscle spasms in patients undergoing bilateral sagittal split osteotomy (BSSO) for mandibular advancements.

This study was a prospective, randomized, double-blinded, placebo-controlled clinical trial conducted at Kingsway Oral and Maxillofacial Surgery (Edmonton, Canada). The sample was composed of adult subjects presenting for the evaluation and management of mandibular advancement via BSSO between 2021 and 2024. Subjects were excluded if they had prior orthognathic surgery, chronic pain disorders, neuromuscular disease, pregnancy, prior exposure to BoNT-A, or required concomitant orthognathic procedures.

The predictor variable was preoperative intramuscular injection of BoNT-A, and subjects were randomized to receive either BoNT-A or saline placebo.

The primary outcome was postoperative pain intensity measured on a numerical rating scale (0 = no pain, 10 = worst imaginable pain) over 14 days. Secondary outcomes included frequency of self-reported muscle spasms, postoperative opioid and nonopioid analgesic consumption, and patient satisfaction. Preanalgesic pain scores were recorded immediately prior to taking any analgesic medication, and postanalgesic pain scores were recorded 1 hour after as needed (PRN) analgesic administration.

Covariates included age, sex, and operative duration.

Between-group comparisons were performed using independent t tests. Daily pain and medication-use trajectories across 14 postoperative days were evaluated using a linear mixed-effects model with fixed effects for group and time. Statistical significance was set at P < .05.

Forty subjects met inclusion criteria (mean age 26.7 years; 55% female). Preanalgesic pain scores were lower in the BoNT-A group (1.72 [SD 0.9]) than in the saline group (2.81 [SD 1.1]; P < .05). Postanalgesic pain did not differ significantly between groups. Opioid consumption over 14 days was significantly lower with BoNT-A (4.9 vs 8.9 doses; P = .046). Mixed-effects modeling demonstrated lower pain and opioid use in the BoNT-A group. No significant differences were observed in nonopioid use or muscle spasm frequency.

Preoperative BoNT-A was associated with reduced preanalgesic pain and lower postoperative opioid use following mandibular advancement via BSSO. Although temporal trends favored BoNT-A, differences in daily trajectories of pain, muscle spasms, and nonopioid use were not statistically significant. These findings provide preliminary support for BoNT-A as a potential adjunct in postoperative pain management, warranting further evaluation in larger, adequately powered trials.