Does the Method of Open Reduction and Internal Fixation of Mandibular Angle Fracture Differentially Affect Postoperative Strength of Jaw Muscles as Assessed by Surface Electromyography? An Analytical Study.

Objective: To analyze differential postoperative strength of masticatory muscles by surface electromyography (sEMG) in mandibular angle fractures (MAFs) using two open reduction and internal fixation (ORIF) approaches.

Materials and methods: Present study evaluated the two ORIF approaches in unilateral non-comminuted central MAFs operated by intraoral ORIF (group A, n = 17) and extraoral ORIF (group B, n = 8). Root mean square (RMS) values of sEMG (μV.s) of bilateral masseter and temporalis muscles for 10 s each, i.e., rest, maximum clenching, maximum mouth opening (MMO), ipsilateral and contralateral excursion, were compared from preoperative and postoperative visits at 1, 3 and 6 months. Further, MMO, ipsilateral and contralateral excursions were measured using caliper.

Results: No significant difference (p > 0.05) in sEMG of all four muscles during all five conditions between the groups was observed from pre-op to post-op 6 months. Post-op group A showed significantly higher MMO and statistically significant difference in sEMG of ipsilateral masseter (p = 0.017) and temporalis muscles (p = 0.019) compared to contralateral muscles at 1 month. When comparing percentage sEMG change from pre-op to 6 months, muscles of both groups revealed positive changes.

Conclusion: The intraoral ORIF technique for MAFs shows early improvements in MMO and subsequent changes in sEMG of the masticatory muscles due to minimal muscle stripping, thus favoring its use in clinical practice.