Electromyographic Study of Facial Nerve Function Using Two Different Surgical Approaches in Low Condylar Fractures of the Mandible: A Randomized Controlled Clinical Trial.

BACKGROUND

Facial nerve (FN) dysfunction is a potential complication during open reduction of mandibular condylar fractures.

PURPOSE

The purpose of this study was to measure and compare the postoperative FN function following transparotid (TP) and transmasseteric anterior parotid (TMAP) operative approaches in open reduction and internal fixation of condylar fractures using electromyogram.

STUDY DESIGN, SETTING, SAMPLE: A randomized controlled clinical trial was designed. The study was conducted in a single tertiary-care hospital in the inpatient setting. Patients aged above 18 years with unilateral condylar fracture of the jaw or bilateral condylar fractures undergoing surgery on only 1 side were included. Patients were excluded if they had fractures of the head, bilateral condylar fractures with surgery planned on both sides, a previous history of surgery in the retromandibular area, existing lacerations to approach condyle, preoperative signs of FN weakness, or a history of parotid surgery.

PREDICTOR VARIABLE

The predictor variable was the operative approach and the subjects were allocated randomly to TMAP and TP.

MAIN OUTCOME VARIABLE(S): The primary outcome variable was postoperative FN function in the surgical approach employed using the House-Brackmann scale and electromyography (EMG) to record any subtle weakness in nerve function. The FN function is recorded at 3 time intervals postoperatively 1 week (T1), 1 month (T2), and 3 months (T3). The secondary outcomes studied were operating time and any other complications recorded.

COVARIATES

Age, sex, fracture pattern with classification of condylar fractures into condylar neck or base fractures according to Loukata et al. Any associated fracture of mandible describing the anatomical location viz symphysis and parasymphysis (anterior mandible), body, contralateral condyle or greater than 1 associated fracture were recorded. Similarly, the presence or absence of any associated midface fracture was also recorded to suggest that the study participants were homogenous in all aspects.

ANALYSES

Analytical statistics included χ test, t-test, and repeated measures ANOVA followed by post hoc test to compare EMG data (mean power and mean amplitude) between 2 operative approaches (TP vs TMAP) for facial muscles including frontalis, oculi, and buccinator at different time intervals (T0, T1, T2, T3). Patients within each group were also analyzed to check for nerve recovery occurring during the follow-up period. The level of significance was set at P < .05.

RESULTS

The study sample was composed of 22 patients with a mean age of 32.82 ± 11.21 years in TMAP and 27.82 ± 8.54 years in the TP group respectively (P = .26); male predominance of 81.8 and 90.9% in TMAP and TP group respectively (P = .53) was noted. The FN deficit as assessed by the House-Brackmann scale clinically, was at 54% (T1), 36.4% (T2), and 9.1% (T3) for the TP group and 27% (T1),9% (T2), and 0% (T3) for TMAP group; however, the results were statistically insignificant (P = .31). In surface EMG evaluation, the mean power for the frontalis muscle was significantly higher in the TMAP approach at the T3 time (105.03 ± 9.7 vs 89.56 ± 10; 95% confidence interval -24.28 to -6.65 with P value = .002). TP approach was faster with a mean exposure time of 9.9 minutes.

CONCLUSION AND RELEVANCE

The results show that both approaches give comparable long-term results with the TMAP group showing better frontalis muscle activity.