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clinmed/1999120011v1 (December 19, 1999)
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Audit of Stapedectomy in the N.W of England for 1996 and analysis of criteria used to describe success.

Author: Mr. C.H.Bulman. FRCS.
ENT Department. Royal Lancaster Infirmary, Lancaster LA1 4RP.

Summary. A questionaire was used to collect information from all the NHS Trusts in the NW. Region. The data collected included the identity and rank of the surgeon, the age and sex of the patients, the side of the operation, the audiometric values of the air conduction audiogram pre-operatively and post operatively, and an account of any complications. The results were analysed and compared to national and international standards. The criteria for analysis of success in surgery for conductive hearing loss were reviewed.

Key words: stapedectomy; audit; N.W.England. evaluation of results in surgery for conductive hearing loss.

Introduction.
The project was part of the work of the Regional Audit Committee of the N.W. of England. The purpose of the audit was to discover the number of operations being performed, the number of surgeons undertaking the surgery, and to analyse the results by comparison with national and international standards. Different authors have used different criteria to measure outcomes and an attempt has been made to analyse the effect this variation might have on reporting. The information given to a patient during the process of consent to treatment should be related to the local circumstances.

Method.
A questionaire was sent to all ENT surgeons in the North West and it is believed that all stapedectomies done in the Region, both in the NHS and in private, during the twelve month period from January to December inclusive were captured. Details collected included name (subsequently anonymised), age, grade of operating surgeon, the type of piston used, and complications (both immediate and delayed). Audiometric data was collected for 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 Khz. for air conduction only. Bone conduction data were not collected (see below). Data were collected for the preoperative audiogram (operated ear and opposite ear), and any postoperative audiogram. The date of the postoperative audiogram was not specified but would vary between 6 and 18 months. These data were analysed and compared to published results.

Results.
Sixty six cases of stapedectomy were recorded. Ages of the patients ranged from 24 to 71 with the greatest number being between 40 and 49 years of age. The side of operation was evenly distributed and there was no significant sex difference. It is not known whether the opposite ear was operated or not except in 2 cases where it is known that the surgery was ‘second ear’ surgery. Nor is it recorded whether the surgery was primary or revision surgery although there was no suggestion that any of the procedures were revisions. It is believed that all procedures were performed with a pick and there is no record of laser or drill technique being used to perforate the stapes footplate. Twenty two surgeons undertook stapedectomy and all the operating surgeons were consultants except one who was a trainee. This individual carried out four operations. The maximum number of cases done by one surgeon was eleven and the least number was one. Most surgeons did between two and five operations during the year. In 42 cases a Shea all-teflon piston was used and in 18 cases a teflon-wire piston was used. In 6 cases a stainless steel piston was used. In six cases it was recorded that fat was used to close the oval window after insertion of the piston.

Success was measured according to two criteria, namely:

1. EITHER - that the average post operative air conduction audiometric threshold was better than 30 decibels. This average was taken from 500 Hz, 1.0 Khz , 2.0 Khz and 4.0 Khz.

2. OR - that the operated ear was better than the non operated ear postoperatively.

According to these criteria the success rates were as follows:

Criterion No. 1. 48/64 = 75%

Criterion No.2. 31/64 = 48%

It is also customary to give a figure for decibels gained or lost and these data are given in Figure 1.

Click on the figure for a larger version.

As well as subdividing the criteria for success it is equally possible to subdivide the criteria for failure and there were several cases not falling into the category of success where the threshold improved significantly postoperatively, sometimes by as much as 35db. It is not known whether these cases might have been regarded as a success using the air-bone gap method of determination as the bone conduction data was not collected. Only in two cases was the post operative threshold actually worse. If this is used as a criterion for failure the failure rate would be less than 4%. Other complications (apart from increased deafness) included tinnitus and vertigo but in no case were these disabling.

Literature Search.
A search of the literature on stapedectomy was performed using Medline and 20 articles published since 1996 were identified. Of these 10 articles were selected for further study. The objective was to discover the general picture for stapedectomy surgery in Europe and N.America with respect to the number of cases being operated, the method used (pick, drill or laser), and the results.

Han et al 1997 1 reported results of 74 revision stapedectomies from the Massachusets Eye and Ear Infirmary done over a period of ten years by three surgeons. Using closure of the air bone gap to within 10 decibels as their criterion for success they found a success rate of 51% by the old AAO (American Academy of Otology) method and 45% by the new AAO method. They compared the results of pick, laser and microdrill and found no difference.

Somers et al. 1997 2 reviewed a series of 2521 stapedectomies done by Professor Marquet over an unspecified period but presumably encompassing his working lifetime. His series included 10% revision operations. 20% were second ears. In assessing the results he used the air-bone gap to within 10 db method, with the modification that only three frequencies were used at 0.5; 1.0 and 2.0 Khz. He reported an average preoperative air conduction threshold of 55-60 decibels and a mean gain of 30 decibels. The success rate was 81% for primary surgery.

John Shea junior 1998 3 1998 reported a series of 14,449 stapedectomies done over a forty year period, an average of 360 cases per year. The criteria for success were defined as closure of the air-bone gap to within 10 db. at three frequencies, (0.5, 1.0 and 2.0 Khz) and no decline in speech discrimination greater than 10%. 95.1% success rate was found after 1 year and 62.5 % after 30 years.

Sedwick 4 1997 reported a series of 550 patients undergoing stapedectomy at the House Clinic in Los Angeles. Criteria used were defined as closure of the air bone gap at four frequencies,(0.5, 1.0, 2.0, & 3.0). The results were divided between small fenestrum and large fenestrum cases in order to compare the surgical method of fenestrating the footplate. The large fenestrum cases were done with a pick and the small fenestrum cases were done with the laser. No significant difference in results was found. The average result was a 78% success rate. It is understood that three surgeons operated on this series but the period is not given. If a period of 20 years is assumed, an average operation rate of 9 cases per year would be calculated.

Laitakari 5 1997 compared two series from 1989-90 and 1993-94 done by the same author but using a posterior crus stapedectomy technique in the first period and a conventional stapedectomy and Causse piston prosthesis technique in the second. 74 operations were included in the first period and 95 in the second. The definition of success was closure of the air-bone gap to within 10db. The success rate in the first group was 68% at six months and 89% in the second group at the same interval.

Ramsay 6 1997 reported a series of 270 stapedectomies and defined success as being closure of the air-bone gap to within 10db. His success rate was 79%. Three surgeons were involved over a period of five years giving an average annual experience of 18 cases per surgeon.

Persson 7 1997 reported results from 437 cases over a 22 year period. Three surgeons were involved giving an average annual operation rate of 6 cases per year. These authors used the air-bone gap method of assessment of success and the result showed a 94% sucess rate with total stapedectomy, 84% with partial stapedectomy and 83% with stapedotomy.

Harkness et al 8 reported the result of an audit of stapedectomy conducted under the auspices of the Royal College of Surgeons of England. During a two year period a total of 185 stapedectomes was carried out by 28 surgeons, an average of three cases per year. Using the air-bone gap method the result showed a 74% success rate.

Huang 9 reported 26 cases of primary stapedectomy from Singapore over a two year period. Two surgeons were involved giving an average operative experience of 6 cases per annum. Using the AAO method of reporting they found a success rate of 65%. They also found that on average the gain in threshold was 28 db. They mentioned the Glasgow Benefit plot but had not sought to apply it to their results.

Puls 10 reviewed a series of 40 stapedectomies. This author performs an average of ten stapedectomies per year. The method used for assessment of success was the air-bone gap. Frequencies were restricted to 0.5, 1.0 and 2.0 Khz.. Although there were postoperative alterations in the bone conduction thresholds the mean bone conduction threshold was unchanged. Using the definition of less than 10 db. ABG the success rate was 62%; if a definition of less than 20db were used the success rate rises to 90%.

Discussion.
In general it is probably safe to assume that a procedure which is done often is done better than a procedure which is done rarely. However there may be other considerations such as accessibility which play a part in deciding where and by whom any operation or other treatment should be given. Surgeons such as Shea and Marquet did many hundreds of stapedectomies and their published results have doubtless been used by many occasional stapedectomists to give preoperative information to patients seeking treatment for otosclerosis. The criterion of success used by these masters was the air-bone gap method which relied on the closure of the preoperative air-bone gap to within 10 decibels. In the best hands this method gives results which show a success rate of above 90%. However a more patient oriented method as suggested by Smyth and Patterson 12 and Browning et al.13 might take account of both ears and this has not yet been generally accepted. Both Shea and Marquet’s results were given on the basis of the three lowest frequencies and not using the conventional four frequencies. This is likely to improve the figures.

Stapedectomy must be the easiest of all operative procedures to audit as the auditory thresholds can easily be recorded both before and after surgery. The difference between the two values gives a result which can be quantified numerically.

In spite of this there is as yet no general agreement on how best to present results. Difficulties arise because normal hearing is binaural and measurements which take account of only one ear are therefore inherently incomplete. In the recommendations of the American Academy of Otolaryngology (AAO) 11 the concept of the air bone gap is paramount. This method measures success in terms of the operated ear only with no consideration given to the non operated ear. Even the air-bone gap method (ABG) contains inconsistencies however as some reports are confined to the three frequencies 0.5, 1.0 and 2.0 Khz, whereas others use four frequencies. The old AAO method uses an average taken from the four pure tone threshold values at 0.5; 1.0; 2.0 and 4.0 Khz both by air conduction and by bone conduction and this has been changed in the new AAO recommendations to replace the 4.0 Khz frequency with the 3.0 Khz frequency. In the old AAO method the air-bone gap was measured using pre- and post operative air conduction but using only the preoperative bone conduction. This was to eliminate cases where the bone conduction values actually deteriorate as a result of surgical damage to the cochlea. In the new method 14 this has changed and the ABG is measured postoperatively using the post operative bone conduction. The authors of the paper do not explain why this change was introduced nor do they state how in this method it will be possible to take account of cases where the bone conduction goes down postoperatively. This seems to be a serious drawback.

In order to address these problems Smyth and Patterson introduced the Belfast Rule of Thumb (1985) 12 which stated that there is ‘significant benefit only if the patient has a post operative threshold better than 30 db over the four middle frequencies. (0.5 - 4.0 Khz).’ This rule also states that there should be less than 15 db. interaural difference postoperatively. The rule was further elaborated in 1991 by the Glasgow Benefit plot13. This created three categories of preoperative patients and four categories of post operative ‘results’, and it is therefore extremely difficult to apply.

The participants in the NW Regional audit considered the AAO method and came to the conclusion that from the patients’ point of view the main criterion for success lies in whether the operated ear is as good as or better than the non operated ear and this also has the merit of being very easy to measure. The following criteria for success were therefore adopted;

-either the operated ear was converted from the worse ear to the better ear;

-or the operated ear average threshold finished at better than 30 decibels.

Using the first criterion the results in the North West audit showed a success rate of 72%. 28% failed to meet this standard although only two cases were actually worse. (see figure 1). If the second, stricter, criterion is used the figure falls to 48%. In spite of the fact that both Smyth and Patterson, and Browning have argued that the criterion for success should be amended to take account of both ears their proposals have not so far been adopted. The present audit makes a case for a new criterion to be used which incorporates the opposite unoperated ear into the equation but which remains quite easy to use and for patients to understand.

The confidential audit done by the Royal College of surgeons

(Harkness et al. 1994) 8 demonstrated that in the UK the average number of operations done annually is three. The results showed 74% reaching the standard set by the definition of closure of the air-bone gap to within 10 db. In 87% the hearing was better by more than 10db. 8% of ears were worse by 10db or more and 5% were unchanged. Only 2% suffered dead ears. While these results cannot match the standards set by Shea and Marquet, nevertheless they appear to represent a very significant net benefit to the patients. In this series we were unable to produce a figure for success measured in terms of closure of the air-bone gap as the bone conduction thresholds were not included in the questionnaire and a direct comparison is therefore not possible.

References.

1. American Academy of Otology. (1995) Committee on Hearing and Equilibrium. Guidelines for the evaluation of results of treatment of conductive hearing loss. Otolaryngology , Head and Neck Surgery. 113; 186-7.

2. Browning. GG; Gatehouse S; Swan IRC. (1991) The Glasgow Benefit Plot; a new method for reporting benfits from middle ear surgery. Laryngoscope 101; 180-5.

3. Han WW, Incesulu A, McKenna MJ. Rauch SD, Nadol JB, Glynn RJ. (1997) Revision stapedectomy; intraoperative findings, results and review of the literature. Laryngoscope 107;9. 1185-92.

4. Harkness P; Brown P. Fowler S; Topham J; (1995) A confidential comparative audit of stapedectomies; results of a Royal College of Surgeons of England comparative audit of ENT surgery in 1994. Journal of Laryngology and Otology 109; 317-319

5. Huang SC; Stanley RE. (1995). Stapedectomy at the Singapore General Hospital; use of functional hearing analysis.. Singapore Medical Journal. 36:2 158-162.

6. Laitakeri K; Laitakeri E. (1997) From posterior crus surgery to 0.6 mm stapedotomy --towards reliability in otosclerosis surgery. Acta Otolaryngologica. Suppl. (Stockholm) 529; 50-52.

7. Persson P. Harder H; Magnuson B. (1997) Hearing results in otosclerosis surgery after partial stapedectomy, total stapedectomy and stapedotomy. Acta Otolaryngologica (Stockholm) 117;1 94-9.

8. Puls T. (1997) Stapes surgery; results when performing a moderate number of stapedectomies. Acta Otorhinologica Belgica 51;1 23-5.

9. Ramsay H.; Karkainen J; Palva T. (1997) Success in surgery for otoscerosis; hearing improvement and other indicators. American Journal of Otolaryngology 18;1. 23-8.

10. Sedwick JD; Louden CL, Shelton C. (1997). Stapedectomy vs. stapedotomy; do you really need a laser?. Archives of Otolaryngology and Head and Neck Surgery. 123;2. 177-80.

11. Shea JJ Jr. (1998) Forty years of stapes surgery. American Journal of Otology. 19;1. 52-55.

12. Smyth GDL; Patterson CC; (1985) Results of middle ear reconstruction; do patients and surgeons agree?. American Journal of Otolaryngology 6. 276-9

13. Somers T, Govaerts P. de Varebeke SJ, Offeciers E. (1997) Revision stapes surgery. Journal of Laryngology and Otology 111;3. 233-9.

Correspondance to: Mr. C.H.Bulman FRCS.
ENT Dept., Royal Lancaster Infirmary,
Ashton Rd., Lancaster LA1 4EZ. UK
Email: cb{at}bulmanc.Freeserve.co.uk

Competing interests: none declared

 





This Article
Right arrow Abstract Freely available
Services
Right arrow Similar articles in this netprints
Right arrow Download to citation manager
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Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bulman, C.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Bulman, C.
Related Collections
Right arrow Surgery:
Otolaryngology/ENT


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