Hearing reconstruction surgery, as the name implies, is the surgical reconstruction of hearing loss from various causes, traditionally speaking mainly for conductive deafness. There are many causes of middle ear conduction disorders, and the incidence of purulent and non-purulent otitis media in particular is high, which is why conduction deafness is the most common of all types of deafness in clinical practice and has been an enduring topic for nearly 100 years. In recent years, several articles have been published in China on this topic, but in this paper, we will further discuss the hearing reconstruction of this type of conductive deafness. The sound-transmitting structure of the middle ear is composed of two main parts – the tympanic membrane and the auditory chain. Tympanoplasty, also known as tympanic membrane repair, was first proposed by Berthold in 1878 as a procedure to repair perforations and improve hearing through tissue grafting techniques. The hearing chain is not properly connected due to congenital, traumatic or inflammatory causes, which often requires reconstruction of the chain to correct the problem. Since then, various artificial materials such as polyethylene, Teflon, bioceramics and alloys have been used in clinical practice and achieved good results. The two are described as follows. The size and location of tympanoplasty tympanic membrane perforation not only affects the level of hearing loss, but also affects the success rate of reconstruction of the auditory chain, and is a determining factor in the reconstruction of hearing in conductive deafness. If the perforated tympanic membrane is not repaired successfully, the next step of reconstruction of the auditory chain cannot be discussed. Tympanic membrane perforation is mainly caused by middle ear infection, trauma or medical factors, and it has been reported in the literature that more than 80% of tympanic membrane perforations heal spontaneously. Tympanoplasty is the surgical repair of the perforated tympanic membrane and is classified as Wullstin tympanoplasty type I. There are three clear indications for tympanoplasty: (1) recurrent intra-ear drainage, (2) patients who wish to swim without waterproof earplugs, and (3) improvement or enhancement of conductive deafness due to tympanic membrane perforation. Tympanoplasty dates back to the 16th century, however, the first successful tympanoplasty was not performed until 1878. With the advent of the surgical microscope, antibiotics, advances in anesthesia, and the clinical use of inactive grafts, tympanoplasty has now become one of the most common methods used in otology, not only for adults but also for children. However, there is a lot of debate about the prognostic factors that affect tympanoplasty. The success rate of tympanic membrane repair varies significantly, ranging from 60% to 90% in adults and 35% to 94% in children. Several investigators have examined a variety of factors that can influence surgical outcomes. There are three accepted surgical routes for tympanoplasty: intraauricular, retroauricular, and intracanal. The intra-auricular approach is preferred for posterior basal or central perforations, while the posterior approach is preferred for anterior basal perforations by Yiqing Zheng, Zhigang Zhang, and Suijun Chen, and the intra-ear canal approach is mainly for small central perforations, which require a sufficiently spacious external auditory canal. The endoscopic technique, which has emerged in recent years, is widely used in various otologic surgeries because it can provide clear, magnified images and a multi-angle observation field, which can fully expose the tympanic membrane and perforation and even the tympanic chamber structure. It has also been shown that the surgical pathway and surgical incision do not affect the surgical outcome. The site and size of the tympanic membrane perforation is a key factor in determining the outcome of tympanoplasty. The anterior tympanic perforation has the highest incidence of repair failure because the anterior tympanic membrane is more difficult to expose, increasing the risk of graft misplacement; in addition, the anterior tympanic membrane has a poorer blood supply than other areas, making it more difficult for the graft to survive. anterosuperior anchoring of the anterior wall of the external auditory canal was recently proposed by Hung et al. to improve the healing rate of anterior perforations, with good results. The effect of perforation size on surgical outcome is controversial, but there is consensus that repair of small perforations (measured at no more than 50% of the tympanic membrane tension) has a significantly higher success rate than those with large perforations. Some consider large tympanic membrane perforations as a high risk factor for reperforation after tympanic membrane repair. The reason is that if the large perforated tympanic membrane is repaired with conventional materials such as temporalis fascia or cartilage membrane, on the one hand, the blood supply is poor and central ischemic necrosis and perforation may occur; on the other hand, even if the repair is successful at an early stage, the lack of a central fibrous layer may lead to inversion and reperforation when upper respiratory tract infection occurs and the eustachian tube is not functioning with negative pressure in the tympanic chamber. Since 1878, when Benthold was the first to use a full skin sheet to repair the tympanic membrane, a variety of grafts have been gradually discovered and used in tympanoplasty. The most commonly used grafts are temporalis fascia, fat, periosteum, cartilage, egg membrane, dura mater, skin, and allograft. Temporalis fascia is the most commonly used because it is easy to obtain. There is no evidence that any of these grafts have the best results for all types of tympanic membrane perforations. The newer decellularized dermal tissue patch is an allograft from human skin that has been specially treated without cellular components, reducing the risk of graft rejection, and is now recommended for traumatic tympanic membrane perforations. As for patients with poor eustachian tube function, anterior tympanic membrane perforation or large perforation and recurrent perforation, ear screen cartilage repair should be chosen, and its survival rate is much higher than that of temporalis muscle fascia repairers. Some scholars believe that the best surgical results are achieved in patients with intra-auricular drainage and non-inflammatory ears, while others believe that the results are better in patients with intra-auricular drainage, but it is generally accepted that the survival of tympanoplasty in patients with intra-auricular drainage is unquestionable. In the case of intra-auricular drainage, the use of modern antibiotics has significantly improved the survival rate of the tympanic membrane. There are many factors that affect the healing of the tympanic membrane after tympanoplasty, and a comprehensive preoperative evaluation should be performed to help improve the survival rate of tympanic membrane perforation repair. Common complications of tympanoplasty include: ① postoperative infection and perforation; ② injury to the bulbar nerve leading to abnormal tongue sensation; ③ facial nerve paralysis due to inadvertent touching of the osseous canal of the horizontal segment of the facial nerve; ④ poor hearing improvement, re-perforation of the tympanic membrane, lateral displacement, adhesion and dislocation of the auditory chain; ⑤ narrowing of the external auditory canal, sensorineural deafness, vertigo and tinnitus, etc. 2. Auditory chain reconstruction Since Wullstein and Zollner proposed the basic principles of tympanoplasty in 1950, middle ear surgery has developed in the direction of hearing function restoration based on the complete removal of lesions to obtain a secretion-free ear. According to Wullstein’s classification, tympanoplasty is divided into five types. In types I, II, and III, the sound-enhancing function of the tympanic chamber is restored to varying degrees, while types IV and V, i.e., the role of the snail window is isolated and there is no sound-enhancing function; moreover, the narrow cavity of the tympanic chamber after type III and IV surgery often causes tympanic adhesions and hearing loss again. In view of the many shortcomings of this type, improved surgeries have emerged in recent decades, and the most representative one is the raised type III surgery, whose surgical method depends on the integrity and activity of the stapes. If the stapes is intact and mobile, the auditory chain is reconstructed with partial ossicularreplacement prosthesis (PORP), and the tympanic membrane is repaired depending on the presence of the hammer bone stalk. If the hammer bone stalk is absent, the perforation is repaired with cartilage, which can prevent the reconstruction of the auditory chain prolapse. If the stapes is absent with only the base plate and is mobile, reconstruction with totalossicular replacementprosthesis (TORP) and tympanic membrane perforation with temporalis fascia, periosteum or cartilage depending on the presence of the hammer bone stalk. For stapes fixation, a simple tympanic membrane repair only is performed, followed by a second-stage artificial stapes surgery. Hearing bone material. Hearing bone material has been the focus of attention and needs to have: ① durability; ② good sound transmission, no distortion; ③ light mass, less than 5 mg; ④ good biocompatibility, no rejection; ⑤ no infection. In the early stage, autologous materials were used, such as autologous residual hammered anvil bone, autologous cartilage and mastoid bone cortex. Although this material is convenient, economical, and does not have self-rejection, it has been resorbed and unstable after a longer period of time due to its lack of blood supply. Microscopic and pathological studies have shown that the surface of the residual auditory bone in patients with middle ear cholesteatoma tends to retain the cholesteatoma matrix and is prone to recurrence. Therefore, it is not recommended to use the residual auditory bone as a material for stage I hearing reconstruction in patients with cholesteatoma, but it can be temporarily placed in the mastoid cavity for long-term observation and judged whether it can be used during stage II surgery. Homogeneous allogeneic materials originated in the 1960s, mainly also allogeneic auditory bone and cartilage, which has been abandoned due to the possibility of cross-infection with diseases (e.g. AIDS, etc.). Due to the disadvantages of autologous materials and the risk of infection with allogeneic materials, artificial materials are now the most common materials used for audioplasty, divided into 3 types: ① biocompatible materials, such as polyethylene and Teflon; ② biologically inert materials, such as titanium, titanium alloy, pure gold and platinum, etc.; ③ bioactive materials, bioceramics, such as hydroxyapatite. Numerous studies have shown that there is no significant difference in hearing recovery after reconstruction of the auditory chain between the various materials. Since its first use in Germany in 1993, titanium artificial auditory bone is now widely used internationally because of its light weight, high hardness and the ability to be shaped to a certain extent, and its obvious advantages in terms of histocompatibility, resistance to infection, stability and conductivity. However, due to its small elasticity and poor buffering effect on pressure, when in a strong acoustic environment or under strong impact, the protection function of the inner ear is weak, which may cause dislocation of the auditory bone and even fracture of the stirrup base plate and inner ear damage in serious cases. Currently, a new generation of artificial hearing bone material is being developed to address this problem. Kartush scores the tympanic membrane perforation and the middle ear mastoid lesion to predict the outcome of the surgery, and evaluates the prognosis of the surgery in five aspects: ear leakage, perforation, cholesteatoma, auditory chain status, middle ear granulation, and history of middle ear surgery. The smaller the score, the better the hearing recovery effect after the hearing reconstruction surgery, and the hearing reconstruction surgery is meaningless when the total index score is 12, and the scale has some reference value for clinical purposes. A study of 1210 patients who underwent auditory chain reconstruction using plastic artificial auditory bone showed that the overall success rate (air-conduction bone difference less than 20 dB) was 62.9%, the poorer result was 6.2%, and the postoperative dislocation rate of the auditory bone was 4%, and there was no significant difference between the hearing status of patients at 3 months after surgery and 1 year after FEATURE199. Gardner et al. reported that the success rate of those who underwent reconstruction using titanium auditory bone Stone et al. reported that postoperative CT scans of the temporal bone were critical in evaluating the location of the artificial auditory bone and the occurrence of postoperative complications, and that CT examinations of patients with unsatisfactory postoperative hearing improvement could determine the location and depth of the auditory bone, whether there was ossification, scar adhesions, and effusion around it, and whether there was resorption of the auditory bone or The CT examination can determine the location and depth of the auditory bone, whether there is ossification, scar adhesion and effusion around it, and whether there is abnormalities such as auditory bone resorption or secondary exolymphatic leakage, and become an important indication to decide whether re-operation is needed. With the continuous breakthroughs in the field of biomedical engineering research, hearing reconstruction materials are being updated day by day. New artificial hearing bones are being developed, including various plastic hearing bones with similar biological properties to autologous bone, jointed hearing bones and artificial intelligent hearing bones with pressure receptors. These high-simulation artificial bones have the characteristics of biological hearing conduction, but also inherit many advantages of current high-quality reconstruction materials, which will bring another leap in the field of hearing reconstruction. In addition, with the gradual development of middle ear implant devices in recent years, a new way of hearing compensation with a new acoustic-electrical-mechanical transducer has been created. Especially for some special cases, such as moderate to severe mixed deafness, tympanic sclerosis, adhesive otitis media, etc., where traditional hearing reconstruction methods cannot effectively improve hearing, middle ear implantation devices such as vibrating sound bridge, cochlea window or vestibular window implantation, Envoy Esteem, etc., can also achieve or even exceed the gain effect of reconstructing the auditory chain. Although the same path is followed, it is debatable whether middle ear implants can be classified as hearing reconstruction due to the different modes of action. It is believed that in the near future, more and more patients with conductive deafness will benefit from this as a variety of new hearing reconstruction and hearing compensation methods are promoted in the clinic.