Proximity of carotid canal wall to tympanic membrane: a human temporal bone study

OBJECTIVE: The objective was to examine the possible risk of injury to the internal carotid artery during procedures in the middle ear, including myringotomy. STUDY DESIGN: Histopathological morphometric study of human temporal bones. METHODS: One hundred forty-two human temporal bone specimens obtained from 92 individuals without any known ear disease were prepared for light microscopic study. Using 83 bones that were available for measurement, the thickness of the carotid canal wall (CCW), which is the medial wall of the bony portion of the eustachian tube, was measured. Using 15 bones selected for three-dimensional measurement, the closest distance from CCW to the anterior tympanic annulus was measured. Using all 142 temporal bone specimens, the CCW was examined to detect the presence of partial dehiscence. In one case, the images of CCW dehiscence and its surrounding structures were reconstructed by a personal computer. RESULTS: The thickness of the CCW was 0.00 to 0.73 mm (average thickness, 0.24 mm [+/-0.12 mm]). The distance from the CCW to the anterior tympanic annulus was 1.8 to 8.1 mm (average distance, 4.9 [+/-1.7 mm]). Dehiscence of CCW was observed in 7 (4.9%) of 142 temporal bone specimens. The reconstructed image showed that the posterior half of the dehiscence of CCW could be seen from the external ear canal. CONCLUSIONS: The CCW was found to be extremely thin or even dehiscent in some cases, rendering the internal carotid artery vulnerable during transtympanic procedures. The study's findings emphasized the need for judicious care when operating in the anterior mesotympanum.     

Relationship of the facial nerve to the tympanic annulus: a direct anatomic examination.

OBJECTIVE: To examine the relation of the facial nerve to the only identifiable surgical landmark in the external auditory canal. INSTITUTION: Community-based teaching hospital. STUDY DESIGN: Examination of formalin-fixed human temporal bones. BACKGROUND: The transcanal approach is often used in tympanoplasty, canaloplasty, hypotympanotomy, and removal of tumors of the external auditory canal (EAC), such as exostoses and osteomas. Surgery of the EAC places the facial nerve at risk for injury as the nerve courses vertically in the posterior canal wall. Few articles have described the relation of the facial nerve's course to the tympanic annulus, the only identifiable landmark in the EAC. This study is the first to document the relationship of the course of the facial nerve with respect to the tympanic annulus by direct anatomic measurement of the temporal bone. METHODS: Thirty-seven formalin-fixed cadaver temporal bones were studied after skeletonization of the facial nerve and tympanic annulus. RESULTS: The facial nerve coursed lateral to the plane of the annulus in 70% of specimens, always in the posteroinferior quadrant. The nerve also coursed anterior to a plane through the most posterior point of the annulus in 73.1% of specimens, also exclusively in the posteroinferior quadrant. The course of the nerve was quite variable with respect to the annulus. CONCLUSIONS: The facial nerve is most vulnerable to injury in the posteroinferior quadrant in transcanal surgery. The annulus is not a reliable landmark for the facial nerve. Anecdotal evidence is cited and recommendations are offered.     

Assessment of visualization of structures in the middle ear via Tos modified canal wall-up mastoidectomy versus classic canal wall-up and canal wall-down mastoidectomies

OBJECTIVE: The aim of this prospective study is to evaluate the differences in the ability to view structures in the middle ear between Tos modified canal wall-up mastoidectomy and classic canal wall-up (CWU) and canal wall-down (CWD) mastoidectomies. METHODS: Eighteen temporal bones of 10 cadaver heads were used. Six bones were randomly selected for each surgical technique (Tos' technique, CWU and CWD mastoidectomies) and fixed on an operating table. In the Tos' technique: (1) transmeatal posterior tympanotomy with drilling of the supero-posterior bony annulus, (2) transmeatal atticotomy with preservation of the bony bridge and (3) cortical mastoidectomy were performed. In the classic CWU mastoidectomy, cortical mastoidectomy and posterior atticotympanotomy (facial recess approach) were performed. Incus and posterior half of the tympanic membrane were removed from all temporal bones. An independent specialist performing otologic surgery evaluated all of the temporal bones and approved the proper extent of dissections. Two another independent observers blinded to the purpose of the study were asked to point five anatomic structures and locations (sinus tympani, anterior attic, posterior crus, lateral attic and the Eustachian tube orifice) in two different sessions. Observers were allowed to rotate the operating table as it has been done during otologic surgery, and the line of view for the observers was both transmastoid and transcanal. The ability to view these structures was recorded as "correct/visible" or "incorrect/invisible". These records were also verified after removing the posterior and superior walls of the outer ear canal in temporal bones of the Tos and CWU groups at the end of the study. RESULTS: Significant differences were found in the ability to view middle ear structures between the Tos' technique and CWU mastoidectomy as well as between CWU and CWD mastoidectomies, with the Tos' and CWD techniques almost equally showing superiority to CWU (p<.0001). Of the five locations, sinus tympani and anterior attic were observed more frequently with the Tos' technique versus CWU (p=.001). Sinus tympani (p<.005), anterior attic (p=.001) and posterior crus (p<.05) were observed more frequently with CWD versus CWU. There was no significant difference in the ability to observe lateral attic and the Eustachian tube orifice among the three techniques. In addition, there was no significant difference in the ability to visualize all the five locations between the Tos' and CWD technique. CONCLUSIONS: Statistical analysis showed good reproducibility of this randomised, blinded study. Tos' modified CWU mastoidectomy, in which most part of the canal wall is intact, showed similar advantage of the CWD in viewing structures in the middle ear. The Tos' technique and CWD mastoidectomy provided better visualization of sinus tympani and anterior attic that are the most frequent places of residual cholesteatoma in the classic CWU mastoidectomy.     

Measurements of human middle- and inner-ear mechanics with dehiscence of the superior semicircular canal.

OBJECTIVES: (1) To develop a cadaveric temporal-bone preparation to study the mechanism of hearing loss resulting from superior semicircular canal dehiscence (SCD) and (2) to assess the potential usefulness of clinical measurements of umbo velocity for the diagnosis of SCD. BACKGROUND: The syndrome of dehiscence of the superior semicircular canal is a clinical condition encompassing a variety of vestibular and auditory symptoms, including an air-bone gap at low frequencies. It has been hypothesized that the dehiscence acts as a "third window" into the inner ear that shunts acoustic energy away from the cochlea at low frequencies, causing hearing loss. METHODS: Sound-induced stapes, umbo, and round-window velocities were measured in prepared temporal bones (n = 8) using laser-Doppler vibrometry (1) with the superior semicircular canal intact, (2) after creation of a dehiscence in the superior canal, and (3) with the dehiscence patched. Clinical measurements of umbo velocity in live SCD ears (n = 29) were compared with similar data from our cadaveric temporal-bone preparations. RESULTS: An SCD caused a significant reduction in sound-induced round-window velocity at low frequencies, small but significant increases in sound-induced stapes and umbo velocities, and a measurable fluid velocity inside the dehiscence. The increase in sound-induced umbo velocity in temporal bones was also found to be similar to that measured in the 29 live ears with SCD. CONCLUSION: Findings from the cadaveric temporal-bone preparation were consistent with the third-window hypothesis. In addition, measurement of umbo velocity in live ears is helpful in distinguishing SCD from other otologic pathologies presenting with an air-bone gap (e.g., otosclerosis).     

Purulent otitis media in children and adults

This study was designed to compare tympanic membrane (TM) and middle ear (ME) pathologies of temporal bones from children and adults with purulent otitis media (POM). Thirty-four temporal bones were used from 22 subjects ages 2 days to 76 years with histopathologic evidence of POM. There were 55 age-matched controls. Histopathologic findings of the TM and ME in children and adults with POM were compared. Clinical histories and the presence of complications were recorded. The incidence of POM was more common in male children than in females. There was a significant increase in the thickness of the posterosuperior and posteroinferior quadrants in children with POM compared to non-OM children. In adults with POM, there was a significant decrease in the thickness of the posteroinferior and anteroinferior quadrants compared to non-OM adults. Children with POM showed a significant increase in the anterioinferior and posteroinferior quadrants and the umbo compared to adults with POM. Pathology of the TM and ME occurred in adults and children, but severity was greater in children. Residual mesenchyme was frequently observed in temporal bones of children. Serious complications such as labyrinthtis and meningitis were observed more frequently in children. All cases with meningitis had labyrinthitis, previous histories of otitis media and had been treated with antibiotics. Although POM occurs in both children and adults, pathologic changes of the middle ear are more severe, and complications (labyrinthitis and meningitis) occur more often in children. Our findings suggest the need to monitor children carefully under the age of 2 years who have POM. Received: 1 March 2001 / Accepted: 12 September 2001     

Experimental and clinical studies of malleus fixation

OBJECTIVES/HYPOTHESIS: Preoperative clinical diagnosis of malleus fixation can be difficult. "Fixation" of the malleus can be caused by various disorders or diseases: fibrous tissue, bony spurs, and neo-osteogenesis around the malleus head or stiffening of the anterior malleal ligament. The conductive hearing loss produced by these disorders or diseases has not been well characterized. The study goals were 1) to determine the effects of various types of malleus fixation using a cadaveric temporal bone preparation and 2) to assess the clinical utility of umbo velocity measurements in preoperative differential diagnosis of malleus fixation and stapes fixation. METHODS: Umbo and stapes velocity were measured in 18 fresh cadaveric human temporal bones with laser vibrometry before and after controlled application of adhesives to the malleus, stapes, or both ossicles. RESULTS: Each simulated pathological condition produced a specific degree of loss in stapes velocity: stiffening of anterior malleal ligament, 0 to 8 dB; fibrous tissue around malleus head, less than 10 dB; bony bar to malleus head, 10 to 30 dB; and extensive neo-osteogenesis around malleus head, greater than 35 dB. Simulated malleus fixations generally produced similar reductions in both umbo and stapes velocity. Stapes fixation reduced stapes velocity with little change in umbo velocity. Because the change in stapes velocity would be similar to conductive hearing loss, experimental results were directly compared with clinical measurements of umbo velocity in surgically confirmed cases of malleus or stapes fixation. The effects of malleus and stapes fixations between the clinical and experimental data were similar. CONCLUSION: The study showed that measurements of umbo velocity and air-bone gap can enable one to diagnose malleus fixation and specifies how to differentiate malleus from stapes fixation.     

Temporal bone histopathologic findings in Alagille's syndrome

Six temporal bones obtained from four individuals with Alagille's syndrome, aged 4 months and 3, 6, and 7 years, were studied histopathologically. The external auditory canals and tympanic membranes were normal. Although the stapes, the interossicular joints, and the subarcuate fossae were slightly underdeveloped in the majority of cases, the other structures in the middle ear were almost normal. However, severe anomalies were observed in structures in the inner ear. In all cases, both the bony and membranous structures of the posterior semicircular canal were partially or totally absent, and, in three ears, those of the anterior semicircular canal were also partially absent; the lateral semicircular canal, however, was normal in all cases. The cochlea was observed to be shortened in only one case.     

Microfractures of the otic capsule. The possible role of masticatory stress

Microfractures of the temporal bone have been recognized for more than seventy years and occur in certain well-defined areas of the otic capsule. The etiology and significance of these microfractures has been debated since their discovery. The most commonly held theory is that they result from stresses within the otic capsule that develop with growth. An alternative explanation might be that they result from masticatory stress placed upon the temporal bone. Fifty serially-sectioned temporal bones from the Ontario Temporal Bone Bank were examined in this study for the presence of microfractures. Our findings as to the most common sites of microfractures agree with previous studies. It is proposed that the constant stress placed upon the petrous temporal bone by the act of mastication is directed by the anatomy of the external, middle and inner ear through certain definite pathways, including the Fallopian canal, the bony semicircular canals and the cochlea. The most common sites of these fractures represent sites of weakness in the path of these directed forces within the otic capsule, and the statistically significant increase in the number of fractures with age lends support to the masticatory stress theory.     

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。     

Effect of middle ear components on eardrum quasi-static deformation

Eardrum deformation induced by quasi-static middle ear pressure was studied at progressive stages of dissection of gerbil temporal bones. With our high resolution moiré interferometer we recorded the shape and deformation of the eardrum along a line perpendicular to the manubrium and through the umbo, at different middle ear pressures. The deformation was measured from the medial side, after serially removing the cochlea, removing the stapes, cutting the tensor tympani, exposing the incudo-mallear joint, and cutting the anterior bony process which connects the malleus to the tympanic bone. The mean displacement as a function of pressure was also determined at all stages of dissection. Removing the cochlea and stapes, and cutting tensor tympani has no effect on static eardrum deformation. Exposing the incudo-mallear joint increases eardrum movement, and cutting the anterior bony connection between malleus and temporal bone strongly changes eardrum rest position and further increases its displacement.     

Sclerotic changes in ossicular ligaments in human temporal bone pathology

When tympanoplasty is performed for conductive hearing loss due to otitis media, hearing recovery may not be as good as anticipated preoperatively. Sclerotic changes may therefore exist in the conduction system of the middle ear. To clarify the relationship between middle ear inflammation and sclerotic changes of middle ear sound conduction, particularly of the ossicular ligaments, specimens of human temporal bones were studied. Histology of the anterior malleal ligament, posterior incudal ligament, and stapediovestibular ligament was examined in 636 ears from 367 individuals (postmortem) ranging from infancy to 90 years old and without blood disease, neoplasm, anomaly, or cholesteatoma. Only small numbers of acute and subacute inflammatory were identified, but sclerotic changes in ligaments were compared between normal and chronically inflamed ears. In anterior malleal and posterior incudal ligaments, the severity of sclerotic hyalinization and calcification increased with age in normal ears, but sclerotic changes in chronically inflamed ears were more severe than in normal ears and displayed a reduced association with age. Conversely, sclerosis of the stapediovestibular ligament was less severe than that of the anterior malleal and posterior incudal ligaments in both normal and chronically inflamed ears, and displayed a reduced relationship with age. The sclerotic changes apparent in the anterior malleal and posterior incudal ligaments therefore seem to be more readily influenced by inflammation than by age. Sclerotic changes of the stapediovestibular ligament are not as severe as those of anterior malleal and posterior incudal ligaments. For cases in which tympanoplasty of inflamed ears is planned, mobility of the anterior malleal and posterior incudal ligaments should be tested independent of testing of the stapediovestibular ligament. When mobility of anterior malleal and posterior incudal ligaments is not as good as mobility of the stapediovestibular ligament, surgical modification of the anterior malleal and posterior incudal ligaments may be advisable.     

Incisions in tympanoplasty: anatomic considerations and indications

The endaural, postauricular and transmeatal incisions are the most commonly used surgical approaches for tympanoplasty. Each incision used in tympanoplasty has its own advantages and limitations so that no single approach is the best approach for all tympanic membrane perforations. The incision selected for tympanoplasty should be determined by the location and extent of disease. Forty adult temporal bones were studied to understand the limiting factors for each surgical approach used in tympanoplasty. The external endaural incision has been modified to permit easier visualization of the crescentic endomeatal canal incisions. The anterior external endaural incision allows direct exposure of temporalis fascia, the external meatus, bony canal and perforation involving the posterior tympanic membrane and ossicular chain. The postauricular incision gives direct exposure of the anterior tympanic membrane with preservation of the anterior canal wall skin. The transmeatal approach should be reserved for smaller central perforations with limited risk for squamous ingrowth into the middle ear. In the transmeatal tympanoplasty, the ear canal should permit the use of a speculum large enough to expose the entire perforation.     

Combined effect of fluid and pressure on middle ear function

In our previous studies, the effects of effusion and pressure on sound transmission were investigated separately. The aim of this study is to investigate the combined effect of fluid and pressure on middle ear function. An otitis media with effusion model was created by injecting saline solution and air pressure simultaneously into the middle ear of human temporal bones. Tympanic membrane displacement in response to 90 dB SPL sound input was measured by a laser vibrometer and the compliance of the middle ear was measured by a tympanometer. The movement of the tympanic membrane at the umbo was reduced up to 17 dB by the combination of fluid and pressure in the middle ear over the auditory frequency range. The fluid and pressure effects on the umbo movement in the fluid-pressure combination are not additive. The combined effect of fluid and pressure on the umbo movement is different compared with that of only fluid or pressure change in the middle ear. Negative pressure in fluid-pressure combination had more effect on middle ear function than positive pressure. Tympanometry can detect the middle ear pressure of the fluid-pressure combination. This study provides quantitative information for analysis of the combined effect of fluid and pressure on tympanic membrane movement.     

Radiologic anatomy of the round window relevant to cochlear implantation and inner ear drug delivery

ObjectiveTo determine anatomic relationships and variation of the round window membrane to bony surgical landmarks on computed tomography.Study designRetrospective imaging review.Methods100 temporal bone images were evaluated. Direct measurements were obtained for membrane position. Vector distances and angulation from umbo and bony annulus were calculated from image viewer software coordinates.ResultsThe angle of round window membrane at junction with cochlear basal turn was (42.1 ± 8.6)°. The membrane''s position relative to plane of the facial nerve through facial recess was (14.7 ± 5.2)° posterior from a reference line drawn through facial recess to carotid canal. Regarding transtympanic drug delivery, the round window membrane was directed 4.1 mm superiorly from the inferior annulus and 5.4 mm anteriorly from the posterior annulus. The round window membrane on average was angled superiorly from the inferior annulus (77.1 ± 27.9)° and slightly anteriorly from the posterior annulus (19.1 ± 11.1°). The mean distance of round window membrane from umbo was 4 mm and posteriorly rotated 30° clockwise from a perpendicular drawn from umbo to inferior annulus towards posterior annulus. Together, these measurements approximate the round window membrane in the tympanic membrane''s posteroinferior quadrant.ConclusionsThese radiologic measurements demonstrate normal variations seen in round window anatomy relative to facial recess approach and bony tympanic annulus, providing a baseline to assess round window insertion for cochlear implantation and outlines anatomic factors affecting transtympanic drug delivery.     

Epithelial migration of the postmyringoplasty tympanic membrane.

OBJECTIVE: To determine whether the postmyringoplasty tympanic membrane (TM) behaves in a similar way compared with a healthy nonoperated eardrum by calculating and comparing the epithelial migration rate and pattern. STUDY DESIGN: Prospective, nonrandomized case-control study. Each subject who has undergone a myringoplasty and with healthy contralateral TM as control is included in this study. SETTING: Otolaryngology outpatient clinic. PATIENTS: A total of 23 subjects with 46 ears have been selected from otolaryngology outpatient clinic of the University Malaya Medical Center after excluding two subjects from this study. The study was conducted from June 2003 to September 2004. INTERVENTION: All the selected subjects' ears were examined under a microscope. Methylene blue ink dot was applied to the epithelium of the TM at the immediate vicinity of the umbo; then, weekly follow-up was performed until the migratory pattern and the rate of epithelial migration was noted. MAIN OUTCOME MEASURE: Direction and rate of epithelial migration in both study and control group were measured and compared. RESULTS: Epithelial migration did occur in postgrafted TM, from the umbo region toward the ear canal wall in a lateral radiating manner. Most of the patients (19 of 23 patients [82.6%]) showed nearly similar migratory pattern (same direction) in both the control and the study ear. None of the 46 ears showed any evidence of epithelial migration in the anteroinferior direction of TM. The rate of migration was slower in the beginning, especially near the umbo region (almost no movement at the first 1 or 2 weeks after ink dot application). For both groups, the rate of migration increased when approaching the periphery or annulus region. There was not much difference in the mean daily migratory rate between the control and the study ear (93.4 microm/d and 91.7 microm/d, respectively). The mean migratory rate was highest in subtotal perforation (97.2 microm/d) and lowest in small perforations (< 20%; 83.6 microm/d). CONCLUSION: There was no difference in epithelial migration rate and pattern between the postmyringoplasty TM and the healthy TM.     

Effects of middle ear pressure changes on umbo vibration

Effects of middle ear pressure changes on umbo vibration were studied in 5 fresh human temporal bones taken from cadavers. Umbo vibration to a constant sound pressure of 120 dB SPL at the tympanic membrane was measured with an MTI 1000 Fotonic Sensor. The results showed that there was a loss of umbo vibration at lower frequencies below 2 kHz; 5.0 +/- 1.0 dB loss at -100 mmH2O, 9.2 +/- 1.3 dB loss at -200 mmH2O, and 13.1 +/- 1.8 dB loss at -300 mmH2O. In contrast, there was a slight increase in umbo vibration at around 2-3 kHz. The effect was considered to be mainly due to increased stiffness of the tympanic membrane and decreased air volume in the middle ear cavity.     

Experimental and Modeling Study of Human Tympanic Membrane Motion in the Presence of Middle Ear Liquid

Vibration of the tympanic membrane (TM) has been measured at the umbo using laser Doppler vibrometry and analyzed with finite element (FE) models of the human ear. Recently, full-field TM surface motion has been reported using scanning laser Doppler vibrometry, holographic interferometry, and optical coherence tomography. Technologies for imaging human TM motion have the potential to lead to using a dedicated clinical diagnosis tool for identification of middle ear diseases. However, the effect of middle ear fluid (liquid) on TM surface motion is still not clear. In this study, a scanning laser Doppler vibrometer was used to measure the full-field surface motion of the TM from four human temporal bones. TM displacements were measured under normal and disease-mimicking conditions with different middle ear liquid levels over frequencies ranging from 0.2 to 8 kHz. An FE model of the human ear, including the ear canal, middle ear, and spiral cochlea was used to simulate the motion of the TM in normal and disease-mimicking conditions. The results from both experiments and FE model show that a simple deflection shape with one or two major displacement peak regions of the TM in normal ear was observed at low frequencies (1 kHz and below) while complicated ring-like pattern of the deflection shapes appeared at higher frequencies (4 kHz and above). The liquid in middle ear mainly affected TM deflection shapes at the frequencies higher than 1 kHz.     

Scala tympani cochleostomy II: topography and histology

OBJECTIVE: To assess intracochlear trauma using two different round window-related cochleostomy techniques in human temporal bones. METHODS: Twenty-eight human temporal bones were included in this study. In 21 specimens, cochleostomies were initiated inferior to the round window (RW) annulus. In seven bones, cochleostomies were drilled anterior-inferior to the RW annulus. Limited cochlear implant electrode insertions were performed in 19 bones. In each specimen, promontory anatomy and cochleostomy drilling were photographically documented. Basal cochlear damage was assessed histologically and electrode insertion properties were documented in implanted bones. RESULTS: All implanted specimens showed clear scala tympani electrode placements regardless of cochleostomy technique. All 21 inferior cochleostomies were atraumatic. Anterior-inferior cochleostomies resulted in various degrees of intracochlear trauma in all seven bones. CONCLUSION: For atraumatic opening of the scala tympani using a cochleostomy approach, initiation of drilling should proceed from inferior to the round window annulus, with gradual progression toward the undersurface of the lumen. While cochleostomies initiated anterior-inferior to the round window annulus resulted in scala tympani opening, many of these bones displayed varying degrees of intracochlear trauma that may result in hearing loss. When intracochlear drilling is avoided, the anterior bony margin of the cochleostomy remains a significant intracochlear impediment to in-line electrode insertion.     

Fixation and detachment of superior and anterior malleolar ligaments in human middle ear: experiment and modeling

The aim of this study is to investigate the function of the superior malleolar ligament (SML) and the anterior malleolar ligament (AML) in human middle ear for sound transmission through simulations of fixation and detachment of these ligaments in human temporal bones and a finite element (FE) ear model. Two laser vibrometers were used to measure the vibrations of the tympanic membrane (TM) and stapes footplate. A 3-D FE ear model was used to predict the transfer function of the middle ear with ligament fixation and detachment. The results demonstrate that fixations and detachments of the SML and AML had different effects on TM and stapes footplate movements. Fixation of the SML resulted in a reduction of displacement of the TM (umbo) and the footplate at low frequencies (f < 1000 Hz), but also caused a shift of displacement peak to higher frequencies. Fixation of both SML and AML caused a reduction of 15 dB at umbo or stapes at low frequencies. Detachment of the SML had almost no effect on TM and footplate mobility, but AML detachment had a minor effect on TM and footplate movement. The FE model was able to predict the effects of SML and AML fixation and detachment.     

中耳内窥镜解剖

目的 :探讨经不同途径的中耳内窥镜解剖所见。方法 :采用 0°,30°,90°的硬质内窥镜 ,对 17个颞骨标本进行了观察 (其中干标本 6个 ,湿标本 11个 ) ,内窥镜插入途径有 :外耳道 ;耳后切口 (包括乳突腔 鼓窦和乳突腔 后鼓室两条亚途径 ) ;中颅窝。结果 :外耳道途径 :采用 0°,30° ,90°的硬质内窥镜 ,所有鼓室结构都可看见 ,包括鼓室窦、面隐窝、上鼓室前隐窝等隐蔽处 ;乳突腔 鼓窦途径 :可以看见乳突腔、鼓窦、上中鼓室等结构 ;乳突腔 后鼓室途径 :可观察到乳突及中下鼓室结构 ;中颅窝途径 :可以观察到上鼓室、鼓窦、乳突腔及鼓室外侧壁的结构 ,中鼓室的大部分结构亦可观察到。结论 :经不同的途径行内窥镜术能清楚地观察到中耳各个结构 ,因此能减少胆脂瘤的复发率及评价术后中耳腔的状态 ,其中 30°的内窥镜提供的视野较好 ;但如经外耳道途径观察后上鼓室及经乳突腔 鼓窦途径观察后鼓室 ,则 90°内窥镜较适合