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Original Article

Minimally traumatic stapes surgery for otosclerosis: Risk reduction of post-operative vertigo

Shiao, An-Sueya,b,e,*; Kuo, Chin-Lunga,b,c,d,e; Wang, Mao-Chea,b; Chu, Chia-Hueia,b

Author Information
Journal of the Chinese Medical Association: June 2018 - Volume 81 - Issue 6 - p 559-564
doi: 10.1016/j.jcma.2017.08.022

    Abstract

    1. Introduction

    Otosclerosis is a primary focal disease involving the bony labyrinth. It is among the best known and most easily manageable causes of conductive hearing loss in adult patients. Caucasians are most affected by clinical otosclerosis, with an incidence of 0.3–0.4%, which is approximately four times higher than that found in Asian populations.1–4 According to data in the Taiwan National Health Insurance Research Database, an estimated 130 to 160 stapes surgeries are conducted each year among the 2.2 billion residents of Taiwan.5

    Otosclerosis is treated exclusively using stapes surgery.6 The evolution of stapes surgery involved the development of a variety of techniques to improve surgical outcomes.1 However, most refinements to surgical techniques have been aimed at correcting hearing impairment, which has led to an overemphasis on hearing performance.2,7–12 A number of complications associated with post-operative quality of life, such as surgery-related vertigo and tinnitus, have not been comprehensively addressed.13

    The author (Dr. Shiao) modified traditional stapes surgery (TSS), the conventional approach to otosclerosis treatment, to develop novel surgical techniques which reduce the risk of subjective discomfort (i.e. vertigo and tinnitus) among otosclerosis patients following surgery. The proposed technique is referred to as minimally traumatic stapes surgery (MTSS) and involves (1) the sequential modification of surgical steps used in traditional stapes surgery (TSS) as well as (2) the application of a CO2 laser. This paper seeks to quantify the effectiveness of MTSS compared to TSS.

    2. Methods

    2.1. Patient data

    We conducted a retrospective cohort study of 56 ears (53 patients) with otosclerosis. In all cases, stapes surgery was performed by the same surgeon (Dr. Shiao) between August 2010 and March 2015 at the Taipei Veterans General Hospital, a tertiary referral center in Taiwan. The diagnosis of otosclerosis was based on a clinical history of progressive hearing loss, normal otoscopic findings, and audiograms presenting conductive or mixed hearing loss. The absence of stapes reflex and normal tympanometry were compulsory for this diagnosis. The cochlear capsule was evaluated using high-resolution computed tomography (CT) to verify the occurrence of otosclerosis, and the clinical diagnosis was confirmed surgically as well as pathologically.

    Among the 53 patients, 12 (23%) had a history of vertigo and 40 (75%) had a history of tinnitus. Nonetheless, all of the patients were free of vertigo and tinnitus preoperatively. Patients who underwent revision surgery, had insufficient audiometric data, or possessed incomplete follow-up data were not included in this evaluation. This study was approved by the Institutional Review Board of the Taipei Veterans General Hospital.

    2.2. Surgical techniques

    Fig. 1 and Video. Surgery was performed using an endaural procedure under general anesthesia. For this, the tympano-meatal flap was elevated and the chorda tympani nerve was identified and preserved. With TSS, the incudo-stapedial joint was separated with a joint knife and the stapedial tendon was cut with scissors, then the anterior and posterior crus with footplate were down-fractured with a microhook and removed. A fenestra of 0.7 mm in diameter was made at the junction of the posterior one-third and anterior two-thirds of the footplate with a microdrill. A piston was inserted into the 0.7-mm hole on the footplate.

    F1-11
    Fig. 1.:
    Surgical steps involved in minimally traumatic stapes surgery. (A) middle ear. (B) the stapes tendon and posterior crus vaporized using a CO2 laser. (C and D) laser spots directed at the lower half of the footplate. (E) a fenestra made at the footplate using a microdrill. (F and G) a piston inserted into the fenestra of the footplate. (H-J) the incudo-stapedial joint separated to facilitate the removal of the anterior crus of the stapes.

    In 2012, Dr. Shiao modified the procedures of TSS due to the high risk of instability of the footplate (e.g. footplate floating) associated with fracturing the stapes arch. Footplate floating can cause post-operative vertigo and/or sensorineural hearing loss. TSS was modified as follows: The stapes tendon and posterior crus were first vaporized using a CO2 laser (Fig. 1A and B). Specifically, single-pulse laser power of 2–3 W was applied to the stapes tendon, whereas laser power of 3–5 W was applied to the posterior crus. After the oval window was identified, a few laser spots (single pulse, 2–3 W) were directed at the lower half of the footplate (Fig. 1C and D), whereupon a fenestra (0.7 mm in diameter) was made in the same area using a microdrill (Fig. 1E). A piston was then inserted into the 0.7-mm hole on the footplate (Fig. 1F and G), and the incudo-stapedial joint was separated to facilitate the removal of the anterior crus of the stapes (Fig. 1H and I). Since 2012, all ears presenting otosclerosis at the hospital have been treated using MTSS.

    For ears treated in this study, the length of prostheses was 4.25 or 4.5 mm and the diameter of prostheses was 0.5 or 0.6 mm. The piston wire loop was either crimped manually using a McGee crimper (conventional piston) or secured to the long process of the incus by applying heat using a Gyrus SMart heat applicator (Nitinol piston). A small number of tiny connective tissue plugs were used to seal the piston–footplate interface (Fig. 1J). Sodium hyaluronate was also used to seal the stapedotomy opening and the ossicular complex area.

    2.3. Audiometric assessment and outcome variables

    All patients received pre- and post-operative pure-tone audiograms. Pre- and post-operative pure-tone thresholds as well as air-bone gap (ABG) values were compiled to determine the mean thresholds at 0.5, 1, 2, and 3 kHz. In cases where the 3 kHz threshold was unavailable, we averaged the 2 kHz and 4 kHz thresholds. ABG was calculated using air conduction (AC) and bone conduction (BC) thresholds recorded from the same audiogram. Factors available at the time of diagnosis were used as predictors of post-operative outcomes. The outcome variables included new onset of vertigo and tinnitus immediately after surgery, as well as post-operative ABG ≤20 dB (hearing success) at the last follow-up.

    2.4. Statistical analysis

    Paired sample t-tests were used to identify significant differences between pre- and post-operative ACs, BCs, and ABGs in both groups. Pearson's chi-square test or Fisher's exact test was used when analyzing categorical variables in order to compare the percentage of ears with post-operative vertigo, tinnitus, and/or ABG ≤20 dB among patients of both groups. Multivariate logistic regression analysis was used to identify key factors affecting post-operative outcomes. All statistical analyses were performed using version 22.0 of the software package SPSS (SPSS, Inc., Chicago, IL, USA). In these evaluations, a p value of <0.05 was considered statistically significant.

    3. Results

    Patient characteristics are outlined in Table 1. Twenty-three TSS surgeries and 33 MTSS surgeries were considered in this study. The study cohort consisted of 41 women and 15 men, and right and left ears were involved in 32 and 24 cases, respectively. The mean age of the patients at the time of surgery was 44 years, with a range of 21–64 years. The mean duration of follow-up was 5 months.

    T1-11
    Table 1:
    Patient demographics.

    Table 2 presents a comparison of pre- and post-operative audiometric results. Throughout the entire cohort, the means of post-operative AC and ABG were significantly better compared to the means of pre-operative AC and ABG (p < 0.001 for both AC and ABG), and mean BC did not significantly deteriorate post-operatively (p = 0.315). When considering the means of AC and ABG by surgery group (i.e. TSS and MTSS), AC and ABG means were also significantly better post-operatively than pre-operatively (p < 0.01 for all comparisons), and mean BC did not significantly degrease post-operatively in either group (p > 0.05 for both groups).

    T2-11
    Table 2:
    Comparison of pre- and post-operative audiometric results (n = 56).

    Table 3 presents a comparison of post-operative audiometric results between the two techniques. No statistically significant differences were observed between TSS and MTSS groups with regard to post-operative AC, BC, ABG or the percentage of ears with post-operative ABG ≤20 dB (p > 0.05 for all comparisons).

    T3-11
    Table 3:
    Comparison of post-operative audiometric results between the two techniques (n = 56).

    As shown in Table 4, the percentage of ears with post-operative vertigo in the MTSS group (27%) was significantly lower than in the TSS group (83%, p < 0.001). However, no statistically significant differences were observed between the two groups (p = 1.000) with regard to the percentage of ears with post-operative tinnitus. No cases of total hearing loss after surgery were recorded in this study.

    T4-11
    Table 4:
    Comparison of post-operative outcomes between TSS and MTSS (n = 56).

    Multivariate logistic regression analysis revealed a statistically significant correlation between post-operative vertigo and surgical technique (Table 5), which confirms that TSS is associated with a significantly higher probability of post-operative vertigo (odds ratio, OR, 51.80, p < 0.001). We adopted an age threshold of 44 in classifying patients as ‘older’ or ‘younger’ for logistic regression analysis, as the mean age of study participants was 44 years.4 It was observed that younger patients (63%) were more likely than older patients (35%) to suffer from new onset vertigo post-operatively (OR 12.61, p = 0.01). In the study, 25 of the younger patients (83%) enjoyed hearing success, compared with only 16 of the older patients (62%), and multivariate logistic regression analysis identified younger age as a predictor of hearing success (OR 6.42, p = 0.03). The same clinical factors did not appear to have a significant influence on post-operative tinnitus (p > 0.05).

    T5-11
    Table 5:
    Multivariate logistic prognostic analyses.

    4. Discussion

    This study compared the effectiveness of MTSS and TSS in terms of their ability to minimize subjective post-operative complications and improve hearing outcomes. We observed that the risk of post-operative vertigo was significantly lower among ears treated using MTSS than among those treated using TSS. The risk of post-operative tinnitus as well as audiometric outcomes were equivalent between TSS and MTSS.

    4.1. Post-operative vertigo

    Surgical techniques and prostheses have undergone profound evolution since Shea first described stapedectomy for otosclerosis in 1956, such that stapes surgery is now an effective treatment option for patients with otosclerosis.1,4 Advances in surgical technology can help surgeons making the transition to minimally invasive techniques. For example, numerous modifications to surgical techniques have been proposed to close the ABG in order to facilitate the movement of sound energy into the inner ear.2,7–12 Indeed, in improving surgical techniques, the primary focus has been on post-operative hearing performance.13 Nonetheless, one cannot discount the risk of post-operative adverse events or the discomfort faced by patients, such as that caused by surgery-related vertigo and tinnitus.

    Vertigo may occur prior to stapes surgery. In this study, 12 of the 53 (23%) patients had a history of vertigo. This is consistent with previous research which found that 17–24% of patients experienced preoperative vertigo.4,13–15 Vertigo can also occur as a complication after stapes surgery, and has an incidence ranging from 37% to 73%.16,17 Birch and Elbrond reported that, of 347 patients, 17% (58) presented abnormal caloric test results at an average follow-up of 15 years after stapes surgery. Among these patients, 21 experienced complete canal paresis.16 Moreover, in a study by Plaza Mayor et al., 2.6% (3/115) of patients experienced vertigo lasting 12 months or more.18 These observations suggest a trend of permanent post-operative vestibular hypofunction. Several etiological factors have been proposed to explain post-operative vertigo, including utricular trauma, proteolytic enzymes, antigen-antibody reaction, disturbed labyrinth fluid pressure, and diminished blood supply to the labyrinth.19,20 These factors may be associated with instability of the footplate during surgical procedures, e.g. footplate floating.

    Footplate floating is a serious complication induced by surgical manipulation, wherein the footplate is pushed into the vestibule and causes damage to structures in the inner ear.10 In 1994, Fisch proposed reversing the steps of classic stapedectomy in order to stabilize the footplate during surgery and thereby avoid such complications. Specifically, Fisch suggested that the piston be placed on the footplate before separating the incudo-stapedial joint and fracturing the cruses of the stapes.8 However, the efficacy of using Fisch's step reversal stapedotomy to prevent incus luxation/sub-luxation and complications associated with the footplate remains an issue of contention.9–11 In our clinical practice, we encountered surgical limitations when treating Asian patients with Fisch's step reversal stapedotomy. One reason for these limitations is that Asians and Caucasians possess an inherent anatomical difference. Specifically, Asians typically possess a smaller ear canal, which can obstruct the surgical view past the posterior crus, thereby causing difficulties when the surgeon performs fenestration on the footplate prior to removing the stapes arch.1

    MTSS is an attempt to improve the surgical view by first removing the posterior crus to facilitate fenestration on the footplate, while leaving the incudo-stapedial joint and anterior crus intact. We did not observe incus luxation/sub-luxation or footplate complications in either the TSS or MTSS group. Nonetheless, the MTSS group faced a significantly lower risk of new onset of vertigo immediately following surgery (27%), compared with TSS group (83%). Despite the fact that 23% of the patients in this study had a history of vertigo, all patients were vertigo-free preoperatively.

    Vilhena et al. recently reported that 72% (92/128) of patients who were free from dizziness preoperatively developed dizziness four months after undergoing traditional surgery involving incudo-stapedial joint disarticulation, fracturing of the stapes superstructure, and stapedotomy or stapedectomy. In the current study, the probability of post-operative vestibular dysfunction in the TSS group was in agreement with that reported by Vilhena et al. (83% versus 72%). Nevertheless, the occurrence of dizziness four months after surgery is not necessarily associated with surgical complications. Thus, it may be difficult to conclude that stapes surgery is responsible for new onset vestibular dysfunction after a period of 4 months. In the current study, the development of vertigo immediately after surgery was adopted as a definitive measure for the assessment of traumatic complications.

    4.2. Post-operative tinnitus

    Stapes surgery can be beneficial for patients with a history of tinnitus by reducing the frequency or severity of tinnitus; however, this technique can also induce or exacerbate tinnitus by damaging the inner ear.21 Of the 53 patients considered by this study, 40 (75%) had a history of tinnitus. This is consistent with literature reporting that the prevalence of tinnitus in otosclerosis patients ranges from 40% to 85%.4,22,23 It should be noted that none of the patients included in this study presented signs of tinnitus at the time of surgery. The risk of new onset surgery-related tinnitus between two groups did not reach statistical significance (TSS 4.3% versus MTSS 3.0%, p = 1.000). This is a clear indication that the risk of damage to the inner ear can be minimized by experienced surgeons, regardless of the techniques they employ.

    4.3. Post-operative hearing outcomes

    In this study, none of the patients in the MTSS or TSS group suffered from post-operative hearing deafness. Furthermore, no significant differences in post-operative BCs were observed before or after surgery in either of the two groups. This is an indication that surgical trauma induced little or no damage in hair cells.20 It should be noted that MTSS did not provide significant advantages over TSS with regard to post-operative hearing benefits.

    4.4. Age-related differences in surgical outcomes

    Multivariate logistic regression analysis revealed age-related differences in post-operative vertigo as well as hearing success. We observed that younger patients (aged 44 years or less) had a significantly higher probability of suffering from post-operative vertigo than did older patients. The likely mechanism may be that the younger patients are prone to the intraoperative ruptures in the membranous labyrinth that cause intralabyrinthine pressure changes and subsequent vertigo. However, given the nature of retrospective study, the underlying explanation for the linkage between age and vertigo has yet to be fully elucidated. Further research will be required to identify the mechanisms underlying these observations.

    Despite younger patients being more likely to develop post-operative vertigo, they were more likely to enjoy hearing success. We observed that younger patients (aged 44 years or less) had a higher probability of success in hearing performance, compared to their older counterparts. There were no differences in the pre-operative mean ABG between the younger (27.1 ± 7.9 dB) and older groups (29.4 ± 8.3 dB, p = 0.537). The percentages of ears with pre-operative ABG less than 20 dB were not significantly different in both groups (30% in the young group and 12% in the older group, p = 0.093), either. Our results are consistent with those reported by aWengen et al.,24 Marchese et al.,25 and Bittermann et al.26 In the study on the influence of age on the results of stapedectomy, aWengen et al. found the youngest group (≦30 years) had the highest probability of postoperative ABG ≦10 dB.24 Marchese et al. also found patients with age <50 years has a higher probability of hearing success than those with 50 years or more.25 A similar observation was obtained in patients with age more than 40 years in the study by Bittermann et al.26 These studies indicated that there is a clear correlation between patient age and hearing outcomes.

    Nonetheless, the fact that younger age was a predictor of hearing success does not necessarily preclude the application of stapes surgery among older adults with otosclerosis, who could still benefit by having disease progression halted or delayed.4 Moreover, hearing gain can improve the performance of hearing aids, with important discriminatory enhancements.4,27

    4.5. Sodium hyaluronate

    We used sodium hyaluronate to seal the stapedotomy opening and the ossicular complex area. Sodium hyaluronate has also been used in cochlear implantation surgery. Hyaluronic acid, a polysaccharide with a molecular weight of 2–4 million daltons, is a component of the extracellular matrix of connective tissues. Hyaluronic acid gels can avoid inflammatory reactions.28 Hyaluronic acid can bind water and act as a viscoelastic cushion. The unique physical properties have made sodium hyaluronate suitable for otologic surgery by acting as a sealant of the opened labyrinth, preventing blood from entering and perilymph from escaping the labyrinth.28,29

    4.6. Study limitations

    A number of possible research limitations should be mentioned. First, this study was limited by a small number of patients and the inherent bias associated with a retrospective review. However, the uniformity and consistency provided by having a single surgeon perform all otosclerosis surgeries at the same medical center is a great strength of this study, as it reduces the influence that individual surgeons have on surgical outcomes. Nonetheless, our findings are not necessarily applicable to other clinics, considering the fact that surgeons differ in their techniques, methodologies, and/or prostheses. This makes it difficult to compare our observations directly with those in the literature.

    In conclusion, in this study, we observed that patients treated using the proposed minimally traumatic technique were less likely to develop vertigo after surgery, compared with patients treated using traditional techniques. MTSS helped avoid footplate damage and thereby reduced the subsequent risk of footplate instability or floating. MTSS was also able to overcome some of the limitations associated with a narrow surgical field among patients of Asian descent.

    Acknowledgments

    This study was sponsored by grants from Taoyuan Armed Forces General Hospital (No.10507 and No. 10626).

    References

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    FAU1-11
    Figure
    Keywords:

    Footplate floating; Minimally traumatic; Otosclerosis; Stapes surgery; Vertigo

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