Abstract
Aims The aim of this study is to assess the relationship between the prosthesis length and the outcome of the primary stapes surgery in patients with otosclerosis. Material and Methods This was a retrospective cohort study. We reviewed medical records of 218 patients between January 2015 and August 2020 in two different referral centers. It was conducted in two hospitals by two different well experienced otologic surgeons that one of them believes in fixed length (4.75 mm) of stapes prosthesis (group A) and, the other one believes in measuring the distance between the footplate and incus long process to choose the proper length of prosthesis (group B). The surgery success rates and complications between these two groups were compared 3 months postoperatively. Results Mean age, preoperative bone conduction (BC) audiometric threshold and air-bone gap, postoperative BC and air-bone gap were similar in both groups (All p > 0.05). Vertigo frequency was not significantly different between the two groups (p = 0.303). There were no significant differences regarding the number of favorable postoperative outcomes between group A and B (70 (97.2%) vs. 142(97.3%) respectively) (p = 0.632). Conclusion This study found no significant difference regarding the hearing outcomes between fixed length vs measured length of stapes prosthesis.
Keywords: Stapes surgery, Otosclerosis, Prosthesis fitting, Stapes prosthesis
Introduction
Otosclerosis is a common adult-onset hearing impairment, characterized by bone remodeling in the otic capsule leading to hearing loss and tinnitus [1, 2]. It has a chronic process and an incidence of 1–2% in the white population [3].
In most cases stapediovestibular interface is involved and the surgical choices are stapedectomy or stapedotomy [1]. One of the well-established surgeries is primary stapes surgery, which is considered to have a satisfactory outcome [4, 5]. Based on techniques, instruments, and materials, physicians have the choice to perform surgery [6, 7].
One of the important factors in the surgical outcome is the length of prosthesis [8]. Using proper prosthesis would inhibit further revision or additional surgeries. A too-long prosthesis will result in vertigo and sensorineural hearing loss [9–11]. Furthermore, a too-short prosthesis will result in conductive hearing loss and ineffective surgery.
Treatment success depends on different factors such as the surgical technique, type of the tissue used for covering the fenestra, and the width and length of the prosthesis [8, 12–14].
As there are a small number of studies regarding the relationship between the prosthesis length and the outcome of the surgery, we designed this study to assess this relationship between the prosthesis length and the outcome of the primary stapes surgery in patients with otosclerosis.
Methods
This was a retrospective cohort study. It was conducted in two hospitals by two different well experienced otologic surgeons that one of them believes in fixed length of stapes prosthesis (4.75 mm) and, the other one believes in measuring the distance between the footplate and incus long process to choose the proper length of prosthesis.
The study was done between January 2015 and August 2020 and approved by the university ethics committee and the institutional review board.
Patients with conductive hearing loss and audiometric characteristics of otosclerosis that were confirmed during surgery were included in this study. Patients with revision stapes surgery were excluded from the study.
Pre- and post-operative audiometry results, laterality, characteristics of the prosthesis, stapes surgery success, and complications were extracted from each patient’s records. If both ears of a patient were eligible for inclusion, each ear was separately entered into the analysis.
Stapes surgeries were performed under general anesthesia in all cases. During the stapes surgery, the bony overhang of the posterosuperior part of the canal was curetted, and the base of the pyramidal eminence, stapes bone, oval window, and facial nerve were exposed. Then the stapedial tendon and posterior crura of the stapes were cut with scissors, and the anterior crus was sharply fractured, and the stapes superstructure was removed. The piston length was 4.75 mm for all patients in group A, and in group B, it was calculated to be 0.25 mm longer than the distance from the outer aspect of the incus to the footplate.
All patients underwent stapedotomy. In this procedure, the fenestration was created manually. We used the 0.6 mm diameter original Shea Teflon piston in all cases. The loop of the piston was first opened out using a Rosen needle. The piston was then positioned in the footplate fenestration, encircled around the long process of incus, and crimped. Fat from the auricular lobule was used for sealing the fenestration.
For all patients, follow-up continued for at least 3 months. The patients’ hearing level and pure-tone audiometry were performed at the last follow-up visit that was considered as the postoperative hearing outcome. The mean air-conduction threshold at 0.5, 1, 2, and 4 kHz was used at the pure-tone average (PTA). A postoperative air-bone gap closure of less than or equal to 10 dB was considered a success in the stapes surgery (favorable outcome).
We used SPSS software version 22 (SPSS Inc., Chicago, IL, USA) for data analysis. Data is presented as Mean ± SD for continuous or as frequencies for categorical variables. Independent sample t-test and Fisher exact test were used for the comparison between quantitative and qualitative variables.
Logistic regression analysis is used to consider predictors of favorable postoperative gap and variables such as sex, age at the time of surgery, side of the affected ear, and preoperative audiologic characteristics were considered as the possible predictors. A p-value of less than 0.05 was considered significant.
Results
Mean age, preoperative bone conduction (BC) audiometric threshold and air-bone gap, postoperative BC and air-bone gap were similar in both groups (All p > 0.05). Frequency of vertigo was not significantly different between the two groups (p = 0.303) (Table 1).
Table 1.
Basic characteristics and audiometry findings in two groups
| Group A (N = 72) | Group B (N = 146) | p value | ||
|---|---|---|---|---|
| Age (mean ± SD) (year) | 36.6 ± 9.8 | 36.4 ± 9.8 | 0.743 | |
| Side | Right | 37 (51.4%) | 54 (37%) | 0.085 |
| Left | 35 (48.6%) | 92 (63%) | ||
| Preoperative BC | 7.7 ± 7.7 | 6.3 ± 12.7 | 0.312 | |
| Preoperative gap | 33.7 ± 4.7 | 35.6 ± 5.5 | 0.104 | |
| Postoperative BC | 6.3 ± 7 | 5.5 ± 11.3 | 0.539 | |
| Postoperative gap | 1.4 ± 4 | 1.2 ± 4.3 | 0.721 | |
| BC difference | − 1.3 ± 4.5 | − 0.7 ± 4.2 | 0.368 | |
| Vertigo | 3 (4%) | 3 (2%) | 0.303 | |
In group B with the measured length of the stapes prosthesis, the most common prosthesis length was 4.5 mm which was used for 91 patients (62.3%). 4.75 mm prosthesis used for 46 patients (31.5%), 4.25 mm prosthesis used for 5 patients (3.4%), and 5 mm prosthesis used for 4 patients (2.7%).
There was no significant difference regarding the number favorable postoperative outcomes between the group A and B (70 (97.2%) vs. 142(97.3%) respectively) (p = 0.632).
Considering the post-operative gap as the dependent variable and sex, age, side of the affected ear, and preoperative audiologic characteristics as independent variables, logistic regression analysis showed sex and age as independent predictors (Table 2).
Table 2.
Logistic regression analysis by considering favorable postoperative gap as dependent variable and independent variables
| OR | 95%CI | p value | |
|---|---|---|---|
| Sex | 0.07 | 0.007–0.8 | 0.031 |
| Age | 1.1 | 1.006–1.2 | 0.031 |
| Preoperative gap | 1.1 | 0.9–1.3 | 0.082 |
| Preoperative BC | 0.9 | 0.9–1.08 | 0.859 |
| Side of affected ear | 0.8 | 0.1–5.7 | 0.821 |
| Type of surgery | 0.7 | 0.1–4.7 | 0.792 |
OR Odds ratio; CI Confidence interval
Discussion
Our study demonstrated that there was no significant difference between the hearing outcomes of stapes surgeries with fixed length versus measured length of stapes prosthesis. To our knowledge, this is the first study evaluating the effect of the fixed length versus measured length of prosthesis on the surgery outcome in patients with otosclerosis.
Most patients with otosclerosis undergo primary stapes surgery. Factors such as surgical technique, type of the tissue for covering fenestra, and the width and length of the prosthesis play a role in treatment success [8, 12–14].
Our results show no significant difference between the two groups (regarding the length of the prosthesis). Husain et al. evaluated medical records of 227 patients who underwent stapedotomy with the prosthesis length ranging from 3.75 to 4.75 mm. According to their results, the best outcomes were in the 4.25 mm prosthesis group[8], and the worst was in the smallest prosthesis length group (3.75 mm).
Schimanski G et al. reviewed the medical records of 12,000 operations of the middle ear for 26 years and reported revisions in 343 cases [15]. Different factors like malfunction, displacement, and length of prosthesis, as well as incus erosion, and fibrous adhesions are among reasons for failure in primary stapedotomy, leading to revisions [4, 9, 16, 17]. The only preventable factor is the length of the prosthesis. Studies showed that revision due to inappropriate length of the prosthesis could occur in 4.6–24.6% of the cases [5, 16]. Marchica et al. assessed 72 cases who were candidates for revision and found that 73% needed changes in the prosthesis length, and the average length change of the prostheses was 0.55 mm [18]. Peterson et al. found that 21 out of 186 cases who had the stapes surgery needed revision, 80% of which was due to short prosthesis [19].
Portman et al. used prosthesis with various lengths, ranging from 3.5 to 5 mm, based on the distance between the incus and the footplate. In most cases, the length of the prosthesis was 4.75 mm, followed by 4.5 and 5 [20].
Husain et al. reported a non-significant positive correlation between height and length of the prosthesis [8], while we did not have data regarding the height of our patients.
Our study had some limitations. First, it was conducted in two hospitals by two different surgeons that may affect the results. Second, this was a retrospective study. Further, blinded clinical trials may be needed for achieving a more reliable comparison.
Conclusion
This study found no significant difference regarding hearing outcomes and complications between the two groups in relation to different lengths of the prosthesis. Furthermore, stapes prosthesis with the fixed length of 4.75 mm has the same hearing outcome as measured length prosthesis.
Acknowledgements
The research was fully sponsored by Otorhinolaryngology Research Center of the Tehran University of Medical Sciences.
Funding
None.
Declaration
Conflict of Interest
To the best of our knowledge, no conflict of interest, financial or other, exists.
Footnotes
Publisher's Note
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