Dangerous angles and depths for middle ear and middle cranial fossa injury during arthroscopy of the temporomandibular joint

Abstract

Purpose: Several reports have suggested a risk of injury to the middle cranial fossa and middle ear during arthroscopic procedures in the superior joint space of the temporomandibular joint (TMJ). However, there has been no anatomic study of directions and distances of the TMJ from the posterior portal in relation to the risk of mandibular fossa injury. In this study, the angles and depths at which the risk is greatest for injury to the deepest point of the mandibular fossa (DP) and to the middle ear during arthroscopy were analyzed. Materials and Methods: Three-dimensional measurements of 96 mandibular fossae in 48 dry skulls were made. Results: It was found that the distance from the lateral rim of the fossa to DP and Hugier's canal was 9.50 ± 2.07 mm and 17.04 ± 3.09 mm, respectively. The most dangerous angle for DP injury in the Frankfort horizontal plane (FH plane) was an inclination of the instrument base of −8° dorsad and 17 and 19° caudad in the frontal plane. The most dangerous angle for Hugier's canal injury was a tilting of the instrument base of 15° ventrad in the FH plane and −2° craniad in the frontal plane. However, these values showed a wide range. Conclusion: It was concluded that great care must be exercised in manipulation of instruments near the DP and Hugier's canal to avoid injury to the middle ear or penetration into the middle cranial fossa.