Cochlear implant technology has been in the clinic for nearly 50 years. In these 50 years, cochlear implant designs have evolved from single-channel to multi-channel, coding strategies have evolved from n-of-m schemes to CIS envelope strategies to FS fine structure coding strategies, and electrode access has evolved from round windows to bulge open windows and back again – the cochlear implant has evolved toward miniaturization and non-invasiveness. The current clinical focus on cochlear implant technology has centered on non-invasive implantation and preservation of residual hearing. It is generally accepted that there is a relationship between residual hearing and the quality of postoperative auditory perception, and that more residual hearing preservation is beneficial for postoperative auditory and speech rehabilitation. Non-invasive implantation is a prerequisite for achieving residual hearing preservation. What factors favor the preservation of residual hearing? The current clinical consensus on the above question includes three aspects: the concept of soft surgery (soft surgery); the application of perioperative medications; and the application of micro-invasive electrodes. In this paper, the above three factors will be discussed. 1. Application of the concept of Softsurgery in cochlear implantation: Soft surgery, the definition of which has not yet been uniformly elaborated. However, it is clinically accepted that soft surgery should be performed in a way that causes the least possible trauma and disturbance to the body and preserves the original function of the body. Softsurgery involves the following aspects of cochlear surgery: (1) Insertion of electrodes using a circular window pathway. The round window is one of the natural openings of the cochlea in the middle ear, and the round window membrane is the part of the inner ear where the tympanic membrane is exposed to the tympanic chamber. The best place to place cochlear electrodes is at the tympanic level, followed by the vestibular level. With the round window pathway, only part of the lip of the round window niche needs to be ground away, and the amount of bone grinding and noise stimulation is less than that of the tympanic capsule opening. The drill bit may damage the osseous spiral plate at the opening site when the drum capsule is opened, but with the round window path, only the lip of the round window niche has to be ground out, and there is no risk of the drill bit damaging the osseous spiral plate. (2) Low-speed grinding and opening of the inner ear. Regardless of whether it is a drum capsule opening or a round window pathway, when grinding the drum capsule or niche lip, a microdrill system or a 1.0 mm grinding drill should be used and the speed of the drill should be controlled to less than 4000 rpm. Care should be taken to maintain the integrity of the endogenous bone coat layer or round window membrane when grinding only the bony part, and in principle, the membranous inner ear should not be opened until the electrode is inserted. (3) Prevent bone powder and blood from entering the inner ear. Bone dust and bleeding from intraoperative bone grinding that enters the inner ear will increase the possibility of fibrous plaques in the cochlea after surgery, which may affect the postoperative auditory outcome of the case. Intraoperative hemostatic measures should be actively taken to prevent blood from collecting at the lowest point of the operative cavity (often around the open area of the inner ear); the integrity of the membranous inner ear should be maintained when opening the tympanic capsule or grinding the round window niche to prevent bone dust and blood from entering the inner ear; after confirming that the opening window or round window membrane exposure is large enough to stop grinding, the operative cavity should be thoroughly flushed with saline. Some doctors recommend using hyaluronic acid to flush the surgical cavity because of its high specific gravity, which can make the shares and clots float and clean them thoroughly; some doctors also recommend that if the membranous inner ear has been accidentally opened during the grinding process, then a certain amount of hyaluronic acid should be slowly injected into the cochlea to clean out the bone powder and clots that have entered the inner ear before inserting the electrode. (4) Time point of opening of the membranous inner ear. The membrane inner ear should be avoided to be connected to the tympanic cavity for a long time, i.e., the endogenous bone coat or round window membrane should be cut or poked open only a moment before the electrode is inserted, and then the electrode should be implanted immediately. After the electrode is fully implanted, if the opening of the round window or tympanic capsule is too large, a small piece of temporalis muscle tissue should be taken to completely close the remaining gap of the opening window. (5) Speed of electrode implantation. When cochlear electrodes are implanted in the tympanic stage, the cochlear shaft or bone spiral plate may be damaged. These injuries are related to the type of electrode and the operator’s handling. Some doctors suggest that the rapid increase in pressure inside the membranous inner ear caused by too rapid implantation of electrodes may lead to displacement and damage to the internal structures of the cochlea. Therefore, electrodes should be inserted slowly (insertion time of three minutes or more) so that the increased pressure is released from the potential third window of the cochlea (cochlear aqueduct, vestibular aqueduct, or neurovascular sieve at the base of the internal auditory canal). 2. Application of glucocorticoids and other drugs in the perioperative period: The role of glucocorticoids in the treatment of sudden deafness cases has been clinically proven, and their role in preserving and improving hearing in cases suggests that clinicians can apply them to the preservation of residual hearing in cochlear implant cases. Glucocorticoids commonly used in the perioperative period of cochlear implant surgery include prednisone, methylprednisolone, and tretinoin. (1) Intraoperative use of glucocorticoids. One dose of prednisone (usually 10 mg in adults, based on body weight in children) is given intravenously before the round window niche or bulbar capsule is ground with a drill. After the round window membrane or endogenous bone coat is exposed, the lower tympanic chamber is soaked with a tretinoin suspension, with the hormone solution surface flooding the round window membrane or endogenous bone coat. Before the electrodes are inserted into the cochlea, the electrodes are rinsed with the hormone solution with a view to carrying the hormone into the inner ear during insertion and to inhibit the fibrotic reaction that may occur after the electrodes damage the intracochlear structures. (2) The use of glucocorticoid hormones in the postoperative period. If the case has good residual hearing in the low frequency region (e.g., in the EAS case, the patient had better than 60 dB residual hearing in the frequency band below 500 Hz), glucocorticoids and neurotrophic drugs should be used postoperatively in combination. Commonly used regimen is adult methylprednisolone 40mg QD IV for 1-3 days postoperatively, 20mg IV for 4-6 days postoperatively; and vitamin B1 and B12 drugs are also used. 3. Selection of micro-injury electrodes: At present, clinical cochlear implant electrodes can be divided into two categories: hard electrodes near the cochlear axis and soft electrodes not near the cochlear axis, in terms of implantation location. Clinically, the near-cochlear axis hard electrodes are widely used because they are designed to facilitate the surgeon’s implantation into the inner ear and reduce the difficulty of cochlear implantation surgery. Non-proximal cochlear axis soft electrodes and ultra-soft electrodes require more surgical skill because of the softness involved, but are inherently less damaging and impactful to the cochlear microstructure and model cochlea, making them somewhat safer for patients with long-term cochlear hearing assistance. The differences between these two types of electrodes and their effects on postoperative outcomes in implanted cases have not been studied in double-blind controlled trials. However, the results of cochlear implantation in cases with cochlear ossification suggest that cochlear implantation is associated with worse auditory performance and speech test results than in cases with normal cochlear ossification. These results may suggest that avoiding fibrosis and ossification after electrode friction damage to the cochlear shaft when implanting electrodes may be associated with better postoperative auditory and speech changes. The proximal cochlear axis electrodes, when implanted in the cochlea, are thought by some surgeons to cause possible damage to the cochlear axis because of their hugging effect on the cochlear axis. For this reason, minimally invasive cochlear surgery and non-invasive near-cochlear operations are now the main trends. Hundreds of patients with non-invasive implantation of soft and ultra-soft electrodes via the round window approach at our hospital have better post-operative hearing acuity and faster recovery time to achieve optimal hearing compared to traditional implantation at the head of the drum. Minimally invasive cochlear implantation is also the main feature of our cochlear implant center at present.