Ossiculoplasty was the main treatment for TOD, which was traditionally performed under microscope [1, 2, 9]. In recent years, EES for tympanoplasty and ossiculoplasty has increased annually, showing some obvious advantages, such as a wider and multiangle field of view which allowed the surgeons to accurately assess and then reconstruct the ossicular chain [5-8]. However, ESS for the management of TOD have not been well studied, up to date, only Kim  reported 15 cases of TOD treated by ESS in 2019, the TOD cases with TM perforation were also included in their study, the diagnose of these cases was relatively easier, which could be observed directly using the endoscope through the perforation. As previously reported, the traumatic TM perforation of some TOD cases could be healed spontaneously in one or several weeks , which could lead to the diagnosis of TOD more difficult. To the best of our knowledge, this is the first study focused on employing totally ESS for the management of TOD with an intact TM. Our research showed the ABG closure to 20 dB or less and ABG closure to 10 dB or less were achieved in 18 cases (100%) and 14 cases (77.8%), respectively, which was well in accordance with the study of Kim , and better than those of MES, Ghonim  reported 42 cases of TOD with intact TM, which were performed MES, the postoperative PTA and ABG were significantly improved to 20.2 ± 9.8 dB and 4.2 ± 7.3 dB, respectively. However, so far, there is absent of a study on direct comparison between ESS and MES for TOD, further studies employing a larger cohort and including MES are needed for validation. Moreover, we also analyzed the postoperative hearing outcomes between incus injury reconstrued by PORP implantation and stapes injury mainly reconstructed by TORP or piston implantation, no significant differences were found, the results were different from our previous study of ossicular chain malformation , the possible reason was that the piston reconstruction was also adopted for stapes injury with footplate anomaly (P4), as many studies reported, the piston prosthesis usually obtained a better hearing result [2, 14, 15].
In this study, head trauma through fall from a height or traffic accident was the most common cause of TOD, which was well in accordance with previous studies . Incus is prone to be involved in injury as it was suspended in the tympanic cavity between the firmly anchored malleus and stapes , the injury types included isolated ISJ dislocation, isolated IMJ dislocation, and a complex of both. Isolated malleus handle and long process of incus fractures were rarely reported in previous reports [16-18], we observed a case of isolated long process necrosis (right ear of P16), and a case of stapes suprastructure fracture which was still suspended upon the stapes footplate (P14), both the ears was misdiagnosed by preoperative examination. HRCT is the preferred modality due to its ability to demonstrate the details of TOD and other associated injuries, such as TBF and FN injury. In this study, the diagnosis sensitivity of HRCT was 88.9% for TOD, which was in according with the previous reports , some TOD cases with the minor abnormalities were still missed in clinical practice. Therefore, exploratory tympanotomy is critical for the diagnosis, and could simultaneously perform ossiculoplasty to improve hearing.
TOD cases usually experienced a relatively long period of delayed diagnosis and treatment, it was still under controversy when to perform the tympanic expletory , suggestions of previous studies were from immediate exploration to 3 months, in this research the average interval between trauma onset and surgery was 2.7 months (range: 0.5 - 24). Grant  reported conservative management was effective in traumatic TM perforation and hemotympanum, however, some TOD cases showed a worsen hearing, therefore, exploratory tympanotomy should be performed for the TOD cases with definite radiologic evidences. Moreover, we found that the dislocated ossicles were usually enveloped with fibrous tissues, forming soft connection between the ossicles, which induced a relatively small average preoperative ABG of 32.4 ± 9.1 dB, compared with a larger average ABG of 63.2 ± 11.7 dB in the cases of isolated middle ear malformation in our precious study . On the other hand, the fibrous tissue may induce the ventilation blockage and provoke a dysventilation of the middle ear . Therefore, the surgery should be considered once HRCT scan suggested the disruption of ossicular with an ABG of 30 dB or more.
TOD was usually accompanied with TBF, perilymphatic fistula, or FN injury . The TOD cases accompanied with severe otologic complications should be treated timely, However, whether EES could be qualified to manage these associated anomalies at the same time is yet unknown. To the best of our knowledge, this is the first study to explore this question for TOD. According to previous reports, perilymphatic fistula commonly occurred in the stapes and round window , though after carefully examination, no occurrence of perilymphatic fistula was observed in our cases series, EES could provide a clear and magnified view for checking these areas, and reconstruction if necessary , the characteristic of endoscopic view ensured the surgical procedures being minimally invasive. TBF was found in 13 ears in this research, 4 ears were accompanied with FN injury, the perigeniculate area and tympanic segment was most commonly involved in the injury, which was in according with previous researches [4, 11]. Though the timing of treatment of traumatic FN paralysis was under controversy , the case of traumatic FN paralysis combined with TOD was a good indicator for timely surgery, especially for the cases with severe immediate-onset facial paralysis and lack of response to the corticosteroid therapy. A few approaches can be used for FN decompression depending on the injury sites, including transmastoid approach and the middle cranial fossa approach, however, it is a challenging to control these areas through traditional surgical approaches . In this research, it showed EES was effective in the management of some selected FN injury, transcanal approach could allow the surgeons to control the whole tympanic segment, geniculate ganglion and lateral aspect of the labyrinthine portion, obviating the need of excessive removal of tympanic scute, canaloplasty, or a post-auricle incision and mastoidectomy, the FN function recovered very well in 6 months after surgeries in all cases. However, when radiologic evidence suggested the injury involved mastoid segment, the transmastoid approach should be conducted, 5 cases (excluded from this research) were performed transmastoid approach under microscope at the same period in our department, carefully preoperative imaging study was critical for selecting TOD patients with FN paralysis for EES exclusively or combined with transmastoid approach.