Ossicular discontinuity or fixation occurs in approximately 55% of cases of conductive hearing loss. The mechanics of sound conduction rely on various factors, including an individual patient's anatomy, which is difficult to predict and simulate in ossiculoplasty. Reconstruction of the ossicular chain is often suboptimal because it consists of 2 joints: one between the malleus and incus and another between the incus and stapes. These joints allow for freedom of movement, which helps prevent excessive footplate displacement and protects the inner ear. Modern ossiculoplasty techniques involve replacing these 2 ossicular joints with partial (PORP) or total (TORP) ossicular prostheses. These procedures effectively transform the ossicular chain into a single piston, transmitting forces from the tympanic membrane directly to the stapes superstructure or oval window. However, using PORPs and TORPs carries risks, including sensorineural hearing loss due to perilymph leakage and potential prosthetic extrusion. Most ossicular chain disorders affect the incus. The causes of ossicular chain disorders include: Cholesteatoma (80%) . Otitis media: Acute . Chronic. Trauma: Blunt. Penetrating. Congenital: Aural atresia . Congenital ossicular fixation. Malformation. Absence. Idiopathic: Otosclerosis. Neoplasms. The first attempt at ossiculoplasty was in 1901, involving a case of absent ossicles. The goal was to connect the tympanic membrane to the oval window. A classification of ossicular defects was created to distinguish between the presence or absence of the malleus handle and the stapes superstructure. Classification schemes were subsequently refined to account for factors such as ossicular chain integrity, malleus head fixation, and stapes fixation. The ideal middle ear implant remains elusive. Both autogenous and alloplastic prostheses have been used with similar hearing reconstruction results. Homographs have largely been abandoned to reduce the risk of transmitting diseases, such as HIV and Creutzfeld-Jakob disease. Most otologic surgeons use one of the following or a combination, depending on personal preference and experience: Biologic materials: Ossicles (autogenous). Cartilage. Synthetic prostheses: Hydroxyapatite. Plastipore. Titanium. Ceramics. Sound energy is created by disturbances in the density of particles in air, an elastic medium that allows sound to travel. The speed of sound is slower in air than in fluids in the inner ear. Repetitive patterns produce musical tones, whereas sound that lacks these patterns is perceived as noise. Ossicular coupling is the primary sound transmission pathway and is facilitated by the ossicular chain and, to a lesser extent, the stapedius and tensor tympani muscles. Middle ear mechanics play a crucial role in transmitting sound energy from the air to the fluid within the inner ear, addressing the impedance mismatch. Impedance refers to the resistance encountered by sound energy as it travels through different media. Without the ossicles to resolve this mismatch, sound would be largely deflected upon entering the inner ear due to the significantly higher impedance of the inner ear fluids than air. This pathway is called "acoustic coupling." The difference between ossicular and acoustic coupling represents the maximal conductive hearing loss expected with ossicular discontinuity, typically 50 to 60 dB. The key factor in the middle ear's ability to match impedance is the "area ratio" between the tympanic membrane and the stapes footplate. The surface area of the tympanic membrane (69 mm²) is about 20 times larger than that of the stapes footplate (3.4 mm²). If sound energy were transmitted directly to the stapes footplate instead of the tympanic membrane, the force per unit area would be 20 times greater, or approximately 26 dB. The other impedance-matching mechanism is the lever ratio, specifically referring to the difference in length between the malleus's manubrium and the incus's long process. This lever ratio is estimated to be 1.3:1 because the manubrium is slightly longer than the long process of the incus, which results in a gain of approximately 2 dB. The middle ear sound pressure gain is less than expected because the tympanic membrane's ability to vibrate in different areas may be affected by tympanosclerosis or middle ear disease. The biomechanics of ossiculoplasty is faced with significant challenges, including: Prosthesis biocompatibility, materials, and characteristics. Middle ear environment, including the status of middle ear mucosa, pathology, and malleus. Tension. Ossiculoplasty has evolved by utilizing various techniques, materials, and prostheses, each with advantages and limitations. The success of this procedure is influenced by factors such as the underlying disease, particularly cholesteatoma, the durability and functionality of the prosthesis, the surgical technique employed, and the surgeon's level of experience. Staging ossiculoplasty alongside tympanomastoidectomy may be preferable. Hearing outcomes have improved only slightly over the past 50 years, and achieving complete closure of the air-bone gap with ossiculoplasty is still rare.
听骨链中断或固定约占传导性听力损失病例的55%。声音传导机制依赖于多种因素，包括个体患者的解剖结构，而这在听骨成形术中难以预测和模拟。听骨链重建往往并非最佳选择，因为它由两个关节组成：一个在锤骨和砧骨之间，另一个在砧骨和镫骨之间。这些关节允许自由活动，有助于防止镫骨足板过度移位并保护内耳。现代听骨成形术技术涉及用部分（PORP）或全（TORP）听骨假体替代这两个听骨关节。这些手术有效地将听骨链转变为单个活塞，将来自鼓膜的力直接传递到镫骨上部结构或卵圆窗。然而，使用PORP和TORP存在风险，包括因外淋巴漏导致的感音神经性听力损失和假体潜在的挤出。大多数听骨链疾病影响砧骨。听骨链疾病的病因包括：胆脂瘤（80%）。中耳炎：急性。慢性。创伤：钝性。穿透性。先天性：耳道闭锁。先天性听骨固定。畸形。缺失。特发性：耳硬化症。肿瘤。首次听骨成形术尝试于1901年，涉及一例听小骨缺失病例。目标是将鼓膜与卵圆窗连接起来。创建了听骨缺损分类法，以区分锤骨柄和镫骨上部结构的有无。随后对分类方案进行了完善，以考虑听骨链完整性、锤骨头固定和镫骨固定等因素。理想的中耳植入物仍然难以实现。自体和异体假体都已使用，听力重建结果相似。为降低传播疾病（如HIV和克雅氏病）的风险，同种异体移植物已基本被摒弃。大多数耳科外科医生根据个人偏好和经验使用以下一种或多种组合：生物材料：听小骨（自体）。软骨。合成假体：羟基磷灰石。聚氯乙烯。钛。陶瓷。声能是由空气（一种弹性介质）中粒子密度的扰动产生的，空气允许声音传播。空气中声音的传播速度比内耳中的液体慢。重复模式产生音乐音调，而缺乏这些模式的声音则被视为噪音。听骨连接是主要的声音传播途径，听骨链以及在较小程度上镫骨肌和鼓膜张肌促进了这一过程。中耳力学在将声能从空气传递到内耳中的液体、解决声阻抗失配方面起着至关重要的作用。声阻抗是指声能在通过不同介质传播时遇到的阻力。如果没有听小骨来解决这种失配，由于内耳液体的声阻抗比空气高得多，声音在进入内耳时会大部分被偏转。这条途径称为“声耦合”。听骨耦合和声耦合之间的差异代表了听骨链中断预期的最大传导性听力损失，通常为50至60分贝。中耳匹配声阻抗能力的关键因素是鼓膜和镫骨足板之间的“面积比”。鼓膜的表面积（69平方毫米）大约是镫骨足板（3.4平方毫米）的20倍。如果声能直接传递到镫骨足板而不是鼓膜，单位面积上的力将大20倍，约为26分贝。另一种声阻抗匹配机制是杠杆比，具体指锤骨柄和砧骨长突之间长度的差异。这个杠杆比估计为1.3:1，因为锤骨柄比砧骨长突略长，这导致增益约为2分贝。中耳声压增益低于预期，因为鼓膜在不同区域振动的能力可能受到鼓室硬化或中耳疾病的影响。听骨成形术的生物力学面临重大挑战，包括：假体生物相容性、材料和特性。中耳环境，包括中耳黏膜状态、病理情况和锤骨。张力。听骨成形术通过利用各种技术、材料和假体不断发展，每种技术、材料和假体都有其优缺点。该手术的成功受到多种因素影响，如基础疾病，尤其是胆脂瘤、假体的耐用性和功能、所采用的手术技术以及外科医生的经验水平。与鼓室乳突切除术同时进行分期听骨成形术可能更可取。在过去50年中，听力结果仅略有改善，通过听骨成形术实现气骨导间距完全闭合的情况仍然很少见。
