镫骨环韧带固定对中耳传声的影响——有限元模型研究

目的　有限元模型分析镫骨环韧带固定对中耳传声的影响。方法　依据1例成年男性颞骨标本Micro-CT扫描数据,建立正常成人中耳有限元模型。通过调整镫骨环韧带的杨氏模量,建立镫骨环韧带固定的有限元模型。计算一定声压刺激下鼓膜与镫骨底板振幅,进而反映建立镫骨环韧带固定时对中耳传声的影响。结果　有限元模型计算结果显示：镫骨环韧带固定时,镫骨底板振动显著减小达47 dB,而对鼓膜振动影响不明显。结论  有限元模型理论分析,镫骨环韧带固定对中耳传声的影响接近于临床观察结果,但需进一步与颞骨实验研究结果对照。深入认识中耳传声机制,为临床耳硬化症提供基础数据。     

Characterization of Stapes Anatomy: Investigation of Human and Guinea Pig

The accuracy of any stapes model relies on the accuracy of the anatomical information upon which it is based. In many previous models and measurements of the stapes, the shape of the stapes has been considered as symmetric with respect to the long and short axes of the footplate. Therefore, the reference frame has been built based upon this assumption. This study aimed to provide detailed anatomical information on the dimensions of the stapes, including its asymmetries. High-resolution microcomputed tomography data from 53 human stapes and 11 guinea pig stapes were collected, and their anatomical features were analyzed. Global dimensions of the stapes, such as the size of the footplate, height, and volume, were compared between human and guinea pig specimens, and asymmetric features of the stapes were quantitatively examined. Further, dependence of the stapes dimensions on demographic characteristics of the subjects was explored. The height of the stapes relative to the footplate size in the human stapes was found to be larger than the corresponding value in guinea pig. The stapes showed asymmetry of the footplate with respect to the long axis and offset of the stapes head from the centroid of the medial surface of the footplate for both humans and guinea pigs. The medial surface of the footplate was curved, and the longitudinal arches of the medial surface along the long axis of the footplate were shaped differently between humans and guinea pigs. The dimension of the footplate was gender-dependent, with the size greater in men than in women.     

Three-dimensional stapes footplate motion in human temporal bones

The literature provides conflicting information on whether the motion of the stapes footplate is piston-like or some other type of motion, such as rotational or rocking. Examination of the three-dimensional (3D) motion of the stapes footplate appears to be an excellent way to understand this complicated motion. Five microsphere reflective targets were placed on the stapes footplate in ten fresh human cadaver temporal bone preparations, and their vibration measured through an extended facial recess approach using a laser Doppler vibrometer. The five target sites on the stapes footplate were center, anterior, posterior, superior and inferior. The stimulus was a sound input of 80-120 dB SPL at the tympanic membrane over a frequency range of 0.1 to 10 kHz. The 3D motion of the stapes footplate was calculated using the velocity amplitude and phase obtained for each target. For frequencies up to 1.0 kHz the vibration of the stapes footplate was primarily piston-like; this motion became complex at higher frequencies, with rotary motion along both the long and short axis of the footplate. When the cochlea was drained, stapes footplate motion became essentially piston-like for all frequencies.     

Oversulfated mucopolysaccharides in the otosclerotic bone

Mucopolysaccharides (glucosaminoglycans, GAGs) were extracted from otosclerotic and non-otosclerotic human stapes footplate, stapes superstructure and guinea pig stapes footplate. Cellulose acetate electrophoresis revealed an unknown highly anionic band (Rf = 1.05) beside the conventional hyaluronic acid, chondroitin sulfate and heparan sulfate fractions. Chemical analysis resulted in a high sulfate/hexosamine molar ratio in the otosclerotic GAG extract (1.7 and 1.9) and a very low ratio in non-otosclerotic human stapes and normal guinea pig stapes footplate GAG extract (0.20 and 0.21, respectively). Hexuronic acid content was highest in guinea pig stapes GAG preparation. Our results serve as indirect evidence of the presence of an oversulfated GAG fraction in the otosclerotic bone, which can potentially initiate otosclerotic bone resorption.     

Possible role of peptides derived from otosclerotic bone in the mechanism of sensorineural hearing loss

Otosclerotic stapes footplates, superstructures and temporal cortical bones were extracted with 0.25 M guanidine X HCl 0.5 M EDTA (pH 7.4) solution. The extracted non-collagenous peptides/proteins were separated chromatographically on a Sephadex G-25 microcolumn. The peptide composition of the bone samples were compared by capillary analytical isotachophoresis (ITP) in the molecular mass range 0.3-5 kD. The otosclerotic stapes footplate contained 13 ITP subfractions, while the stapes superstructures and cortical bone contained only 9 and 10, respectively. An otosclerosis-specific ITP subfraction was also detected in the stapes footplate, but not in the stapes superstructure or cortical bone. This subfraction was previously demonstrated in the otosclerotic perilymph as well. Four ITP subfractions occurred common in the otosclerotic stapes footplate, the superstructure and the cortical bone. Two of these common subfractions were not found in the cortical bone peptide extract, but all of them revealed higher than normal levels in the otosclerotic perilymph.     

Effect of adhesion on the acoustic functioning of partial ossicular replacement prostheses in the cadaveric human ear

BACKGROUND: Adhesion formation following ossiculoplasty surgery has been implicated as a cause of the progressive deterioration of an initially good postoperative hearing result. Scar tissue between the partial ossicular reconstruction prosthesis (PORP) and adjacent middle ear structures is a common finding at revision surgery. OBJECTIVES: This study aims to investigate the effects of simulated scarring on the microacoustic transmission characteristics of a PORP in the fresh cadaveric human temporal bone. METHODS: Cortical mastoidectomy and extended posterior tympanotomy permitted access to reflective markers placed on the stapes footplate. A sound stimulus at 80 to 95 dB was presented to the closed external ear canal and displacements were measured with the laser Doppler vibrometer. PORPs were placed in cadaveric specimens, and the shaft of the prosthesis was cemented to the adjacent promontory using dental cement. Serial measurements were made from the stapes footplate as the adhesive was allowed to harden, a process that we have taken to simulate the gradual fixation of the prosthesis by scarring in the live patient. RESULTS: There was a consistent reduction in stapes footplate displacement as the cement hardened. CONCLUSION: The gradual adhesion of a PORP to the promontory produces a consistent reduction in microacoustic transfer to the stapes footplate in the fresh human cadaveric model.     

Studies on the mechanics of the normal human middle ear

The middle ear was studied in temporal bone preparations using a laser-Doppler interferometer. For measurements at a sound level of 80 dB SPL this method proved to be very reliable, as was shown by good reproducibility of results in experiments over more than 6 hours. The vibrations of the tympanic membrane and stapes footplate were studied from 200 Hz to 10 KHz and the results demonstrate a piston-like movement of the stapes footplate up to 120 dB SPL. The damping effect of the normal ear is located mainly at the footplate/cochlea level and the middle ear cavity per se does not contribute significantly to the stiffness of the middle ear system.     

Fixation of the stapes footplate in children: a clinical and temporal bone histopathologic study.

OBJECTIVE: To clarify the anatomic characteristics, cause, and surgical outcomes relating to fixation of the stapes footplate in children. STUDY DESIGN: Retrospective case review and four-center histopathologic study of temporal bones. SETTING: Tertiary referral center. PATIENTS: We reviewed charts and histologic specimens from 12 children, aged 7 to 13 years, who underwent surgery for footplate fixation. We also studied stapes footplates in 288 temporal bones from 181 children ranging from newborn (20-44 weeks of gestation) to 13 years of age. MAIN OUTCOME MEASURE: Anomalies of the stapes footplate in children. RESULTS: The average age of diagnosis of hearing loss was 6.6 years. Criteria for a diagnosis of otosclerosis were progression of a conductive hearing loss and an intraoperative finding of fixation of the anterior stapediovestibular joint in five patients. In contrast, a nonhomogeneous, thickened, fixed footplate and the absence of an annular ligament were indicators of congenital fixation in six children. In one child, there was neither new bone from the otic capsule nor any obvious otosclerotic foci. In the temporal bone study, 17 of 181 (9.4%) children had anomalies of the stapes footplates, with ankylosis in 4 (2.2%). In two subjects (1.1%), there was an otosclerotic focus not in contact with the stapes footplate. CONCLUSION: Children younger than 6 years with various congenital anomalies are more likely to have congenital footplate fixation, which will present intraoperatively as a thickened footplate with a partial or absent annular ligament. Children older than 6 years with progressive conductive hearing loss are more likely to have otosclerosis, which presents as fixation of the anterior stapediovestibular joint. The difference in surgical outcomes is probably related to different degrees of footplate abnormality.     

Pneumolabyrinth: a new radiologic sign for fracture of the stapes footplate

A case of fracture of the footplate of the stapes resulting in air in the labyrinth is reported. The pneumolabyrinth was demonstrated by CT scan of the temporal bone but not by complex motion tomography. We consider pneumolabyrinth to be a new diagnostic CT finding in stapes footplate fracture.     

The influence of the sequence of surgical steps on complications rate in stapedotomy.

OBJECTIVE: To assess whether the incidence of complications of stapes surgery depended on the sequence of surgical steps and CO2 laser use in stapes surgery. STUDY DESIGN AND SETTING: Retrospective and prospective analysis of 420 consecutive stapedotomies was set in tertiary referral University Hospital. PATIENTS: 376 patients with otosclerosis in whom 420 primary stapedotomies were performed. INTERVENTION: Stapedotomy under local anesthesia using manual perforators and CO2 laser. MAIN OUTCOME MEASURE: The incidence of incus subluxation, floating footplate during stapedotomy. RESULTS: Comparison of the incidence of incus luxation in groups with the piston inserted after removal of the stapes arch, and groups with the piston inserted on the intact ossicular chain showed statistical significance. In the group where perforation of the footplate was performed after removal of the stapes arch floating footplate occurred more often than in groups with reversed sequence of steps. CONCLUSION: Perforation of the footplate before removal of stapes arch reduces the risk of floating footplate, and placing the prosthesis on the incus before removal of stapes arch reduces the risk of subluxation of the incus. CO2 laser stapedotomy with reversed sequence of steps was the safest method of stapes surgery.     

Complications of three methods of stapedectomy

In a group of 270 partial stapedectomies performed by one surgeon using teflon-piston prosthesis it was assessed whether incidence of complications depended on sequence of surgical steps. In group I of 50 ears classical stapedectomy was performed: 1. removal of stapes superstructure, 2. making a hole in the footplate, 3. placing the prosthesis on the incus. In group II of 167 ears the hole in the footplate was made before removal of stapes arch. In group III of 53 ears: 1. the hole in the footplate, 2. placing the prosthesis on the incus, 3. removal of stapes arch, was performed. Total deafness had one patient of the whole group. No patient had perilymphatic fistula and facial nerve palsy. Floating footplate developed in 4 patients of group I, in one patient of group II and in none patient of group III. Subluxation of incus developed in 3 patients of group I, in 12 patients of group II and in none patient of group III. Comparison of three stapedectomy methods showed that making the hole in the footplate before removal of stapes arch prevents floating footplate and placing the prosthesis on the incus before removal of stapes arch prevents subluxation of the incus.     

Sudden sensorineural hearing loss with fracture of the stapes footplate following sneezing and parturition

Three rare cases of sudden high frequency sensorineural hearing loss with longitudinal fracture of the stapes footplate are presented. In two patients it occurred after they suppressed a sneeze. In the third patient after the exertion of parturition. At exploratory tympanotomy all were found to have longitudinal fractures of the stapes footplate and two had a perilymph fistula at that site. The history and audiometric profiles in such patients should raise a high index of suspicion regarding the possibility of a stapes footplate fracture.     

Sudden sensorineural hearing loss with fracture of the stapes footplate following sneezing and parturition.

Three rare cases of sudden high frequency sensorineural hearing loss with longitudinal fracture of the stapes footplate are presented. In two patients it occurred after they suppressed a sneeze. In the third patient after the exertion of parturition. At exploratory tympanotomy all were found to have longitudinal fractures of the stapes footplate and two had a perilymph fistula at that site. The history and audiometric profiles in such patients should raise a high index of suspicion regarding the possibility of a stapes footplate fracture.     

Mechanics of the TORP/stapes interface

The gain in hearing as a result of ossicular prosthesis (TORP) placement on the stapes footplate was evaluated in 10 patients during actual middle ear reconstructive surgery. The patients with radical mastoidectomy cavities were operated on under local anaesthesia and intra-operative hearing was tested with the TORP shaft in three positions with regard to the stapes footplate: anterior, central and posterior. The anterior position of the shaft provided greater hearing improvement than the posterior position, with the central position falling approximately midway.     

不同材料修补不同面积中央性鼓膜穿孔的有限元模型分析

目的利用有限元模型研究不同移植材料修补不同面积中央性鼓膜穿孔对术后听力的影响。方法建立人正常中耳有限元模型,在鼓膜表面施加90 dB SPL声压得到镫骨底板位移的频率-幅度曲线(基准曲线,为正常中耳有限元镫骨底板位移曲线),通过与相关实验数据对比,验证模型可靠性,再建立3.10、10.66、22.25、42.0 mm²中央性鼓膜穿孔有限元模型,分别用0.25、0.5、1 mm厚度耳屏软骨以及0.4、0.8 mm厚度颞肌筋膜修补上述不同面积中央性鼓膜穿孔,获得术后镫骨底板位移频率-幅度曲线,并与基准曲线对比,分析术后听力情况。结果鼓膜穿孔面积3.10 mm²时,不同厚度的耳屏软骨和颞肌筋膜获得的镫骨底板位移均能基本符合基准曲线;穿孔面积10.66 mm²时,不同厚度的耳屏软骨或颞肌筋膜修补获得的镫骨底板位移曲线也基本贴近基准曲线,但0.25、0.5 mm厚度耳屏软骨的位移曲线更符合基准曲线;穿孔面积22.25 mm²时,在低频区域,耳屏软骨比颞肌筋膜获得的镫骨位移曲线与基准曲线的差异更小,在高频区域,0.25、0.5 mm厚度耳屏软骨和0.4 mm厚度颞肌筋膜获得的镫骨位移曲线更贴近于基准曲线;穿孔面积42.0 mm²时,颞肌筋膜和1 mm厚耳屏软骨获得的镫骨底板位移曲线与基准曲线的差异较大,而0.25 mm或0.5 mm厚耳屏软骨差异较小,0.25 mm厚耳屏软骨效果最佳。结论使用耳屏软骨或颞肌筋膜作为移植材料修补较小中央性鼓膜穿孔后镫骨底板位移没有显著差异;随着穿孔面积增大,以较薄的耳屏软骨作为移植材料得到的镫骨底板位移曲线与基准曲线差异最小。     

Cathepsin-B activity in otosclerosis

Cathepsin-B activity was determined fluorimetrically in the otosclerotic stapes footplate, the stapes superstructure, normal temporal cortical bone, and os frontale osteoma. Measurements with a synthetic substrate made determinations in individual samples possible. The cathepsin-B activity in the otosclerotic stapes footplate was one order of magnitude higher than that of the superstructure, which was not affected by the disease. The cortical bone and the superstructure displayed similar activities, as did os frontale osteoma and otosclerosis. The high lysosomal proteinase activity appears to be closely connected to the otosclerotic bone resorption process.     

Cathepsin-B activity in otosclerosis

Summary Cathepsin-B activity was determined fluorimetrically in the otosclerotic stapes footplate, the stapes superstructure, normal temporal cortical bone, and os frontale osteoma. Measurements with a synthetic substrate made determinations in individual samples possible. The cathepsin-B activity in the otosclerotic stapes footplate was one order of magnitude higher than that of the superstructure, which was not affected by the disease. The cortical bone and the superstructure displayed similar activities, as did os frontale osteoma and otosclerosis. The high lysosomal proteinase activity appears to be closely connected to the otosclerotic bone resorption process.     

Vibration characteristics and function of atelectatic segments in the tympanic membrane in fresh human cadaveric temporal bones

Dimeric segments are commonly encountered in otological practice. They may be associated with a mild conductive hearing loss and often coexist with other tympanic membrane and middle ear abnormalities. Some otologists have advocated surgical management but the consequences of dimeric segment stiffening, shielding or excision and grafting on acoustic transfer to the stapes footplate has been poorly explored. In this study, laser Doppler vibrometry was used to measure vibrations at the tympanic membrane and the stapes footplate in the fresh cadaveric human temporal bone. The dimeric segment vibrates more than the adjacent, thicker normal tympanic membrane. Shielding or excision and grafting of the dimeric segment with thicker and stiffer materials has little effect on displacement at the stapes footplate.     

Reconstruction of the superstructure of the stapes in guinea pigs with biovitro ceramic and silicone foil

BACKGROUND: The reconstruction of the stapes superstructure is still a problem.Efforts for the fixation of implants on the footplate did not show satisfying results yet. METHODS: In 6 guinea pigs a biovitro ceramic (Bioverit) was placed on the stapes footplate after removal of the superstructure.The exclusive bony fixation of the implants on the footplate should be achieved by the use of silicone foils.For control purposes replantation of autologous ossicles was done in one group of 3 animals and a sham operation was performed without any use of implants in the other group of 6 guinea pigs. RESULTS: After 21 weeks not only bony fixation of the implant with the footplate was observed, but furthermore with the wall of the middle ear.Bone formation was detected along the silicone foils. In the first control group of animals we found bony fixation of the replanted ossicles and even a bow-shaped reconstruction of the stapes superstructure in the second. CONCLUSIONS: The guinea pig was not an ideal model for questions of middle ear reconstructions due to its enormous potential for bone formation. In this animal model bony fixation of glass-ceramic with the stapes-footplate could be induced.     

Relationship of the utriculus and sacculus to the stapes footplate: anatomic implications for sound-and/or pressure-induced otolith activation.

One hundred thirty human temporal bones that were sectioned in the vertical plane were examined to evaluate the relationship between the stapes footplate and the otolith organs. The shortest distance between the footplate and the utriculus was 0.58+/-0.10 mm in the posterior third of the oval window, 1.04+/-0.20 mm in the middle third, and 1.51+/-0.20 mm in the anterior third. The distance from the sacculus to the footplate was 1.33+/-0.20 mm in the middle third of the oval window and 1.31+/-0.18 mm in the anterior third. Membranous connections extending between the utriculus and the footplate were found in 26% of temporal bones. These membranous connections in coexistence with additional anatomic factors such as stapes hypermobility and/or dehiscence of bone within labyrinthine structures may predispose patients to sound- and/or pressure-induced otolith activation. The findings may have implications for different causes of the Tullio phenomenon.