Symposium on tympanoplasty. 3. Tympanoplasty: ossicular chain reconstruction

Permanent restoration of hearing with neither conductive nor sensorineural impairment is the goal of functional reconstruction in tympanoplasty. Many changes and modifications of technique have occurred to accomplish these ends in the past 10 years.^1,2 The purpose of this paper is to present the technique used by members of the Otologic Medical Group and to comment on the use of homograft ossicles in over 700 cases.     

Reconstruction of the ossicular chain with hydroxyapatite prostheses

To achieve a lasting result in reconstruction of the ossicular chain, strict material and surgical criteria must be combined. The best biomaterial, apart from bone, is hydroxyapatite, the mineral matrix of living bone tissue. For the reconstruction, the assembly technique is used instead of a columella. Direct contact with the drum membrane is not reliable if a columella is used, and extrusion or lateralization may influence postoperative results. In the case of a missing incus, an assembly prosthesis of dense hydroxyapatite is placed on top of the stapes head and the handle of the malleus, in a pocket between drum membrane and the neck of the malleus. Long postoperative follow-up of 120 patients showed an air-bone gap closure within 20 dB for 83.3% of the patients, no extrusion was observed, and the hearing gain stayed constant. Reconstruction of a tympanic membrane perforation and posterior canal wall was performed in the same stage in sixty patients. In the case of a missing incus and stapes superstructure, an incus/stapes prosthesis of dense hydroxyapatite, as assembly between footplate and handle of the malleus, was used. Long postoperative follow-up of twenty-five patients showed an air-bone gap closure within 20 dB for 68% of the patients. Reconstruction of a tympanic membrane perforation and posterior canal wall was performed in sixteen patients. No extrusion was observed and the hearing gain stayed constant. Hydroxyapatite prostheses have proven to be a good alternative for autologous and homologous ossicles.     

Reconstruction of the ossicular chain (author's transl)

197 consecutive tympanoplasties involving reconstruction of the ossicular chain were analyzed. After a one-year followup, the interposition of a homologous ossicle between the mobile stapes and the long process of the malleus with intact anterior half of the drum has given a satisfactory result in 93% of the patients. Unsatisfactory results were obtained in 50% of those patients presenting with only the stapes or its footplate intact. Reasons for the failures were: graft lateralisation, fixation, atrophy or displacement of the homologous ossicle used. The twostage tympanoplasty with utilisation of John Shea's TORP prosthesis has considerably improved the hearing result achieved in the second category of patients. One has to await, however, long-term results in order to assess whether or not the TORP Plastipore prosthesis should be recommended in middle ear surgery.     

人工钛质听骨重建听骨链的疗效观察

目的观察用人工钛质听骨重建听骨链的疗效.方法用钛质听骨重建听骨链60例、65耳,并随访10～24月.结果听力提高＞10dB HL者58耳(89.2%),气骨导闭合＜20dB HL者37耳(56.9%),听力达应用水平45耳(69.2%).结论听骨链重建应用人工钛质听骨,生物相容性和组织亲合性好,无毒性,耐腐蚀,重量轻,与镫骨连接牢固,不易脱位,术后听力提高幅度大,疗效显著.     

Reconstruction of the ossicular chain with titanium implants. Results of a multicenter study

BACKGROUND: For decades, oto-surgeons have been trying to find suitable alloplastic materials for replacing ossicles in the case of morphological and functional disorders in the middle ear. The focus of attention has been on tissue tolerance and functionality. PATIENTS: A retrospective analysis of the implantation of titanium prostheses is presented (Type "Duesseldorf", Heinz Kurz GmbH, Dusslingen, Germany) in 528 patients operated in 14 ENT hospitals. The hospitals involved are ENT hospitals with different fields of specialization presenting a representative cross-section of surgical ENT treatment. Evaluated were healing results, hearing gain and surgical handling of the implants. RESULTS: Despite pathological middle ear conditions, the tissue-implant healing rate was very high. In 4.4% of the patients the implants were rejected. In the case of partial ossicular reconstruction, an average hearing gain between 10 and 20 dB was achieved. Total reconstruction of the ossicular chain showed even better audiological results (15 to 20 dB on average). CONCLUSION: Due to the good morphological and functional results achieved, titanium implants have proven their worth for middle ear micro-surgery. Their advantages are their light weight and delicate structure, facilitating very good micro-surgical handling. It is advisable to place a thin layer of cartilage between the prosthesis headplate and the tympanic membrane. In this manner, the number of material extrusions can be safely reduced, however, extrusions cannot completely be avoided.     

Reconstruction of the ossicular chain using a multistrand wire spring prosthesis

A multistrand wire spring prosthesis is presented for ossicular reconstruction. This device offers a workable solution not only to the ossiculoplasty problems associated with lateralization of the tympanic graft and displacement of the prosthesis, but also to other problems such as fixation to middle ear wall, tissue reaction, resorption, degeneration, biodegradation, or poor sound conduction, which are obviated using a stainless steel wire for the ossicular prosthesis. The spring also protects the inner ear from external trauma. Long-term reconstruction results of 14 cases using first generation coil spring prosthesis are presented. A freely mobile prosthesis head composed of cartilage with perichondrium on a wire-mesh platform distributes pressure evenly to the undersurface of the tympanic membrane and further ensures the prevention of pressure necrosis and extrusion. When the handle of the malleus is present, the head-loop assembly of the spring prosthesis is designed to securely capture the handle. There is no practical loss of sound energy passing through the spring. Over a period of 14 years none of the wire prosthesis was found to have eroded through the stapedial footplate.     

Reconstruction of the ossicular chain in the middle ear with glass ionomer cement

OBJECTIVES: The aim of this study is to describe a method to repair small defects (1 to 2 mm) of the ossicular chain by means of glass ionomer cement (GIC) alone. Larger defects can be repaired with a combination of GIC and a platinum wire prosthesis. GIC is a two-component hybrid material consisting of inorganic glass particles surrounded by an insoluble hydrogel matrix. GIC has been used by dentists for many years, but only a few reports describe the use of GIC in human middle ear surgery. Many investigators have proved that most GICs are biocompatible, biostable, and well tolerated by bone and soft tissue. STUDY DESIGN: From 1994 to 1996 GIC was used in 97 middle ear operations. In 44 cases small defects of the ossicular chain were reconstructed with GIC alone. The observation period ranged from 1 to 4 years. METHODS: Nearly all operations were performed with the patient under local analgesia. RESULTS: The postoperative air-bone gap was less than 20 dB in 83.3%. Compared with results from comparable operations, the GIC results are significantly better. One patient had reoperation because the cement had loosened from the bone as a result of faulty GIC operation technique. CONCLUSIONS: Repair of defects of the ossicular chain with GIC is an easy, efficient, quick, and inexpensive method, which ought to be kept in mind for future middle ear surgery. No complications in the middle ear were related to GIC.     

原位组织工程构建兔听小骨的研究

目的将猪小柱状脱细胞松质骨与骨形态发生蛋白2（bone morphogenetic proteins 2，BMP-2）复合制成听骨赝复物，植入兔听泡内，观察其原位成骨状况。方法制备猪小柱状脱细胞松质骨，与BMP-2复合作为听骨赝复物。选择5只新西兰大耳白兔，采用耳后进路，听泡后外侧骨壁钻孔，清除听泡内部分黏膜组织，一侧植入复合BMP-2听骨赝复物，对侧耳植入单纯脱细胞骨小柱作为对照。术后3个月，通过大体及病理切片观察听骨赝复物成骨情况。结果术后5只兔健康状况良好。术后3个月，植入的复合BMP-2脱细胞松质骨与听泡骨壁接触部位结合紧密，表面被再生黏膜覆盖，病理学检查发现有新骨形成，而对照耳仅有黏膜覆盖，无新骨形成。结论复合BMP-2的猪脱细胞松质骨可于兔听泡内形成新生骨组织，有可能用于听骨链缺损重建。     

Osteoradionecrosis of the ossicular chain

Osteoradionecrosis of the temporal bone is a well-known sequela of radiotherapy for neoplasms at the base of the skull. Presenting symptoms include otalgia, chronic aural drainage, and hearing loss, which can be conductive, sensorineural, or mixed. The conductive component has been hypothesized to be caused by radionecrosis of the ossicular chain. This case report documents the existence of osteoradionecrosis of the ossicular chain in a 10-year-old boy operated on for resection of extensive osteoradionecrosis of the temporal bone.     

Three-dimensional CT-imaging of the ossicular chain

In eight patients, with a known air-conduction hearing loss, three-dimensional images of the ossicular chain were constructed based on heavily overlapping high resolution CT-slices, obtained from a spiral CT data set. High quality three-dimensional images could be obtained in all eight patients. Supplementary information was derived from these three-dimensional images in three patients; in one, this supplementary information had therapeutic importance. The slight image quality loss in spiral-CT of the temporal bone, compared with conventional CT, is in some cases largely compensated by the possibility of rendering high quality secondary reconstructions.