Does the surgical approach for treating mandibular condylar fractures affect the rate of seventh cranial nerve injuries? A systematic review and meta-analysis based on a new classification for surgical approaches

Purpose: The purpose of this study was to determine the rate of facial nerve injury (FNI) when performing (ORIF) of mandibular condylar fractures by different surgical approaches. Materials and methods: A systematic review and meta-analysis were performed that included several databases with specific keywords, a reference search, and a manual search for suitable articles. The inclusion criteria were all clinical trials, with the aim of assessing the rate of facial nerve injuries when (ORIF) of mandibular condylar fractures was performed using different surgical approaches. The main outcome variable was transient facial nerve injury (TFNI) and permanent facial nerve injury (PFNI) according to the fracture levels, namely: condylar head fractures (CHFs), condylar neck fractures (CNFs), and condylar base fractures (CBFs). For studies where there was no delineation between CNFs and CBFs, the fractures were defined as CNFs/CBFs. The dependent variables were the surgical approaches. Results: A total of 3873 patients enrolled in 96 studies were included in this analysis. TFNI rates reported in the literature were as follows: A) For the transoral approach: a) for strictly intraoral 0.72% (1.3 in CNFs and 0% for CBFs); b) for the transbuccal trocar instrumentation 2.7% (4.2% in CNFs and 0% for CBFs); and c) for endoscopically assisted ORIF 4.2% (5% in CNFs, and 4% in CBFs). B) For low submandibular approach 15.3% (26.1% for CNFs, 11.8% for CBFs, and 13.7% for CNFs/CBFs). C) For the high submandibular/angular subparotid approach with masseter transection 0% in CBFs. D) For the high submandibular/angular transmassetric anteroparotid approach 0% (CNFs and CBFs). E) For the transparotid retromandibular approach a) with nerve facial preparation 14.4% (23.9% in CNFs, 11.8% in CBFs and 13.7% for CNFs/CBFs); b) without facial nerve preparation 19% (24.3% for CNFs and 10.5% for CBFs). F) For retromandibular transmassetric anteroparotid approach 3.4% in CNFs/CBFs. G) For retromandibular transmassetric anteroparotid approach with preauricular extension 2.3% for CNFs/CBFs. H) For preauricular approach a) deep subfascial dissection plane 0% in CHFs b) for subfascial approach using traditional preauricular incision 10% (8.5% in CHFs and 11.5% in CNFs). I) For retroauricular approach 3% for CHFs. PFNI rates reported in the literature were as follows: A) for low submandibular approach 2.2%, B) for retromandibular transparotid approach 1.4%; C) for preauricular approach 0.33%; D) for high submandibular approach 0.3%; E) for deep retroparotid approach 1.5%. Conclusion: According to published data for CHFs, a retroauricular approach or deep subfascial preauricular approach was the safest to protect the facial nerve. For CNFs, a transmassetric anteroparotid approach with retromandibular and preauricular extension was the safest approach to decrease risk of FNI. For CBFs, high submandibular incisions with either transmassetric anteroparotid approach with retromandibular or transmassetric subparotid approach, followed by intraoral (with or without endoscopic/transbuccal trocar) were the safest approaches with respect to decreased risk of FNI.