Comparative Evaluation of Hearing in Cartilage Umbrella, Boomerang and Torp in Chronic Otitis Media Cases with Absent Stapes Suprastructure: Our Experience

Abstract

Ossicular discontinuity is one of the most common causes of conductive hearing loss. Ossicular chain reconstruction improves conductive hearing loss. With no additional cost, cartilage ossiculoplasty is easy to perform, and also the cartilage is well tolerated being an autograft. In this study we compared the audiological outcome in ossiculoplasty done by cartilage umbrella, cartilage boomerang and alloplastic TORP. 75 patients of age group 10–50 years clinically diagnosed with chronic otitis media with conductive hearing loss and an air bone gap (ABG) of at least 20 dB posted for surgery were included. Ossiculoplasty was done in three groups with autologous cartilage boomerang, cartilage umbrella and alloplastic TORP. In mucosal disease hearing gain was better in umbrella technique (17.66 ± 1.1) dB than Boomerang (16.9 ± 0.8) dB and TORP (10.68 ± 0.9) dB. ABG closure was higher in Boomerang and TORP. Hearing improvement in patients with squamosal disease managed by canal wall up surgery was 25.01 ± 1.1 dB, 27.73 ± 3.1 dB and 20.12 ± 1.8 dB in Boomerang, Umbrella and TORP group respectively showing that umbrella method gave maximum improvement. ABG closure was better in TORP group. In canal wall down surgery patient’s maximum improvement was seen in Boomerang (29.51 ± 0.9) dB followed by Umbrella (26.67 ± 1.2) dB and TORP (25.27 ± 0.8) dB group. ABG closure was higher in Boomerang group. Cartilage ossiculoplasty is a reliable and effective method of ossicular chain reconstruction for both mucosal and squamosal disease. Cartilage ossiculoplasty has the added advantage of reduced chances of prosthesis extrusion as compared to TORP.

Introduction

Conduction of sound from tympanic membrane to inner ear labyrinth is mainly through the ossicular chain. Any discontinuity in the ear ossicles disrupts the conductive mechanism and results in conductive hearing loss. Ossicular discontinuity is one of the most common causes of conductive hearing loss. Without an intact ossicular chain, even the best surgical procedure for repairing of tympanic membrane will not help the patient. For this, ossicular chain repair also known as ossiculoplasty gained importance amongst the otologists. The first ossiculoplasty was performed in 1955 by Zoellner in a case of chronic otitis media (COM) where a connection was made between tympanic membrane and oval window [1]. Over the years, many classifications have been given for middle ear reconstruction depending upon the extent of ossicular chain destruction. The most commonly used and well-known classification was given by Wullstein in 1956 [2]. A good ossiculoplasty is one which keeps the transmission of sound from tympanic membrane to vestibule as much near natural as possible. Many factors affect the outcome of ossiculoplasty. Ossicular chain reconstruction results in improvement of conductive part of hearing loss.

Reconstructive tympanoplasty is a constantly improving science with new and more innovative techniques directed at creating better middle ear dynamics. This would result in an improved structural and acoustic outcome. Ossicular reconstruction methods should be relatively easy to duplicate and there should be a noticeable functional hearing gain. There are two types of factors which affect the result of ossicular reconstruction. Intrinsic factors are residual ossicular chain, functionality of eustachian tube and adhesions between ossicular chain and middle ear mucosa. Extrinsic factors include type and material of ossicular prosthesis used and the surgical technique performed. Over the years, different authors have used various graft materials for ossicular reconstruction i.e. autologous ossicles and cartilage, gold implants [3], alloplastic ossicular prosthesis like total and partial ossicular replacement prosthesis (TORP/PORP) made of teflon plastics, titanium, bio inert and bioactive ceramics implants, hydroxyapatite, bone cement, glass ionomer cement (GIC), phosphate cement and silicate cement [4].

Use of autologous ossicles especially reshaped incus for ossiculoplasty is popular citing similar physical properties. Some authors have raised one concern about it is in the fact that in cases of squamosal pathology, sometimes the ossicle is covered or invaded with granulations or is eroded by cholesteatoma and therefore even after all precautions are taken, there is always a theoretical risk of some microscopic disease being left behind in the middle ear which may cause recurrence of disease and hamper the long-term result of such ossicular reconstruction. Cartilage ossiculoplasty is free of such a possibility, is easy to perform with no additional cost to the patient and also the cartilage is well tolerated as it is an autograft. In the past years, authors have tried to shape autologous cartilage in the form of TORP or PORP without compromising the auditory outcome which is provided by commercially available prosthesis.

In our study we have compared the audiological outcome in ossiculoplasty done by cartilage umbrella, cartilage boomerang and allopathic TORP.

Materials and Methods

This prospective study was carried out in the Department of Otorhinolaryngology and Head Neck Surgery of a tertiary health care hospital in India after taking due permission from Institutional ethical clearance committee. This study was carried out from October 2018 to March 2020. Eighty patients from age group of, 10–50 years clinically diagnosed as chronic otitis media with conductive hearing loss and a minimum 20 dB air bone gap (ABG) posted for surgery were included in the study. A written, informed consent was obtained after explaining the patients about the study. Patients with complicated COM, acute otitis media, otosclerosis and cases with hearing loss not related to COM like presbycusis, trauma and patients on ototoxic medications were excluded. Five patients were lost to follow up who were then excluded from the final analysis.

In form of a preformed proforma, detailed history, examination and complete follow up of the patients were recorded. Ear examination was done with the help of Welch Allyn Otoscope and Oto- endoscope. Condition of the tympanic membrane and site of tympanic membrane perforation was noted, middle ear mucosa and ossicles were examined. 39 patients were diagnosed with mucosal type of COM whereas 36 were diagnosed with squamosal type of COM. The audiometric analysis was performed in patients using a clinical audiometer—Primus Audidata calibrated according to ISO standard in sound treated room. Frequencies selected for the purpose were 250–8000 Hz. Air and bone conduction threshold were determined with appropriate masking technique whenever indicated. Hearing level was defined as mean air conduction threshold at 500, 1000, 2000 and 4000 Hz and an average of these frequencies was calculated to measure the hearing level. Air bone gap was also calculated for the same frequencies. Hearing loss was classified according to WHO grading system. Examination under microscope/oto-endoscopic and radiological examination in form of HRCT temporal bone was done when needed and those patients having evidence of ossicular erosion in the form of absent stapes suprastructure were included in the study. Randomization of patients was done by a card lottery which divided the patients equally into three groups. In the first group (Group BC) ossiculoplasty was done with cartilage Boomerang whereas in the second group (Group UC), hearing was surgically reconstructed by using a cartilage umbrella. In the third group (Group TO), reconstruction was done with titanium TORP.

Technique

Autologous conchal or tragal cartilage with perichondrium preserved on one side was harvested intra-operatively according to the need. Tragal cartilage was harvested by giving an incision 5 mm below the tragal tip on medial surface to preserve its tip for cosmetic reasons. Soft tissue dissection was done carefully and a block of tragal cartilage leaving the inferior part was harvested and perichondrium was peeled away from one side [5]. For harvesting the conchal cartilage, after giving a post auricular incision, soft tissue dissection was done after infiltrating local anesthesia. As conchal cartilage thickness is variable in thickness in different parts, we harvest relatively straighter and thinner cartilage from cymba area [6].

Umbrella: In Group UC, where umbrella ossiculoplasty was performed, the harvested cartilage was reshaped as a disc of 3–4 mm size diameter and a small hole was made in its center with help of tip of a micro suction. A small bar of cartilage about 4 × 1 × 1 mm was cut and this was fitted in the hole to give it a shape like umbrella. The foot of this umbrella was fitted over stapes footplate and the disc was supported at the bony annulus. The other end of disc may rest over the handle of malleus, if it was present. Temporalis fascia graft is then placed laterally over this assembly as usual [5] (Fig. 1).

Fig. 1.

A, B Preparing umbrella from cartilage. C, E Intraoperative placement of Umbrella

Boomerang: In group BC, to prepare a boomerang, a 10 × 2 × 1 mm strip of conchal/tragal cartilage is taken. A cut only through 2/3 width of cartilage thickness approximately 3 mm from one end is made using a measuring grid [7, 8] with perichondrium still intact on uncut surface. This shorter end is kept over stapes footplate and the other end is fitted into hypo tympanum just medial to annulus. Temporalis fascia graft is placed laterally over this perichondrium cartilage assembly. (Figs. 2 and 3).

Fig. 2.

A–C Preparing boomerang from cartilage

Fig. 3.

A–C Intraoperative boomerang placement

TORP: Commercially available Teflon TORP was used in cases which were assigned to group TO. (Fig. 4).

Fig. 4.

Alloplastic TORP in place

Post operatively, patients were followed up and otoscopic examination was performed to check for any graft failure or extrusion at the end of 4 weeks, 12 weeks and then at 24 weeks. Audiometry was performed at 24 weeks to see the result of ossicular reconstruction in the groups. The results were then compiled, tabulated and statistically assessed with help of software (version 23; SPSS USA). Descriptive statistical analysis was done using statistical tests like ANOVA. A p value of < 0.05 was considered significant.

Observations and Results

In our study, 42.67% patients were in the age group of 21–30 years followed by 25.33% patients in 31–40 years of age. Sex ratio in our study was 1: 1.08 in favor of males (Table 1).

Table 1.

Relation of age and sex with type of disease

Age in years	Male		Total	Female		Total	Grand total
	Mucosal disease	Squamosal disease		Mucosal disease	Squamosal disease
11–20	03	04	07	02	03	05	12 (16.00%)
21–30	07	08	15	10	07	17	32 (42.67%)
31–40	06	04	10	05	04	09	19 (25.33%)
41–50	04	03	07	02	03	05	12 (16.00%)
Total	20 (26.67%)	19 (25.33%)	39 (52.00%)	19 (25.33%)	17 (22.67%)	36 (48.00%)	75 (100.00%)

In preoperative assessment of participants with mucosal disease, mean hearing loss was 44.23 ± 3.6 dB among participants planned for Boomerang, 44.41 ± 4.5 dB among those planned for Umbrella and 47.44 ± 5.9 dB among patients planned for TORP. All participants were statistically similar in hearing loss (p value 0.17, > 0.05 ANOVA). Similarly, air bone gap was 28.42 ± 4.7 dB among participants planned for Boomerang, 27.23 ± 5.6 dB among participants planned for Umbrella and 26.78 ± 4.2 dB among participants planned for TORP. Air bone gap was statistically similar among participants (p value 0.67, > 0.05 ANOVA). Postoperatively it was observed that hearing gain was more in umbrella group (17.66 ± 1.1) dB followed by boomerang group (16.90 ± 0.8) dB whereas ABG was reduced maximum in Boomerang (15.31 ± 1.2) dB followed by TORP group (14.68 ± 0.9) dB whereas it was only 12.52 ± 0.5 in Umbrella group (p value < 0.05, ANOVA).

In preoperative assessment of participants with squamosal disease, mean hearing loss was 51.38 ± 5.2 dB, 52.43 ± 5.5 dB, 50.12 ± 3.7 dB and mean air bone gap was 29.10 ± 3.8 dB, 27.11 ± 3.3 dB, 28.61 ± 3.2 dB among participants planned for Boomerang, Umbrella and TORP respectively (p value 0.72 and 0.59, > 0.05 ANOVA). After surgery, it was noted that hearing loss was reduced maximum in Umbrella group (28.23 ± 2.1) dB followed by boomerang group (27.00 ± 1.9) dB. These two groups showed similar results, but they had statistically significant results with TORP group which only showed a mean hearing gain of 22.34 ± 1.6 dB. Air bone gap was reduced comparably, i.e., 15.31 ± 12 dB and 14.68 ± 0.9 dB in Boomerang and TORP group which was statistically significant than Umbrella group (12.52 ± 0.5) dB (p value < 0.05, ANOVA) (Table 2).

Table 2.

Pre-operative and post-operative audiometric assessment in mucosal and squamosal disease

Audiometric analysis		Mucosal disease (N = 39)		Diff	P value ANOVA	Squamosal disease (N = 36)		Diff	P value ANOVA
		Pre op	Post op			Pre op	Post op
Hearing loss (mean ± SD) dB	Boomerang	44.23 ± 3.6	27.33 ± 2.8	16.9 ± 0.8	< 0.001	51.38 ± 5.2	24.38 ± 3.2	27.00 ± 1.9	0.0002
	Umbrella	44.41 ± 4.5	26.75 ± 1.9	17.66 ± 1.1		52.43 ± 5.5	24.20 ± 2.3	27.13 ± 2.1
	TORP	47.44 ± 5.9	26.76 ± 2.1	20.68 ± 0.9		50.12 ± 3.7	27.78 ± 1.7	22.34 ± 1.6
	P value (ANOVA)	0.17	0.76			0.72	0.66
Air bone gap (mean ± SD) dB	Boomerang	28.42 ± 4.7	13.11 ± 2.6	15.31 ± 1.2	< 0.001	29.10 ± 3.8	16.12 ± 4.1	12.98 ± 0.8	0.0001
	Umbrella	27.23 ± 5.6	14.71 ± 1.9	12.52 ± 0.5		27.11 ± 3.3	16.21 ± 2.9	10.9 ± 0.6
	TORP	26.78 ± 4.2	12.10 ± 4.1	14.68 ± 0.9		28.61 ± 3.2	15.98 ± 3.4	12.63 ± 0.5
	P value (ANOVA)	0.67	0.09			0.59	0.99

While comparing post-operative assessment of hearing loss among patients undergoing canal wall up surgery for squamosal disease, mean improvement was 25.01 ± 1.1 dB, 27.73 ± 3.1 dB and 20.12 ± 1.8 dB in Boomerang, Umbrella and TORP group patients respectively. Among patients with canal wall down surgery, better post-operative improvement in hearing was seen in patients operated by Boomerang method (29.51 ± 0.9) dB followed by Umbrella (26.67 ± 1.2) dB and TORP groups (25.27 ± 0.8) dB. This difference in post-operative improvement was statistically significant (p value < 0.05, ANOVA). When ABG closure was assessed, in canal wall up surgery TORP showed a better result with ABG closure of 16.74 ± 1.1 dB whereas in canal wall down surgeries, Boomerang appeared to a better technique with 15.20 ± 1.2 dB closure. This difference was found to be statistically significant (p value < 0.05, ANOVA) (Table 3).

Table 3.

Audiometric assessment in patients with squamosal disease undergoing canal wall up/down surgery (n = 18)

Audiometric parameter	Surgery	Boomerang (n = 12)			Umbrella (n = 12)			TORP (n = 12)			P value ANOVA
		Pre op	Post op	Mean difference	Pre op	Post op	Mean difference	Pre op	Post op	Mean difference
Hearing loss dB (mean ± SD)	Canal wall up	48.21 ± 5.9	23.21 ± 1.2	25.01 ± 1.1	49.54 ± 7.4	21.81 ± 4.7	27.73 ± 3.1	47.34 ± 2.3	27.34 ± 2.7	20.12 ± 1.8	< 0.001
	Canal wall down	55.43 ± 2.8	25.92 ± 2.3	29.51 ± 0.9	56.28 ± 5.1	29.61 ± 1.8	26.67 ± 1.2	53.28 ± 0.9	28.01 ± 1.9	25.27 ± 0.8	< 0.001
Air bone gap in dB (mean ± SD)	Canal wall up	27.48 ± 3.7	15.65 ± 1.9	11.83 ± 0.7	26.34 ± 2.5	14.68 ± 2.9	11.68 ± 0.8	28.89 ± 2.7	12.15 ± 2.2	16.74 ± 1.1	< 0.001
	Canal wall down	31.32 ± 4.1	16.12 ± 2.8	15.20 ± 1.2	29.54 ± 2.2	19.81 ± 2.1	9.71 ± 1.1	28.97 ± 4.3	18.29 ± 3.3	10.68 ± 1.4	< 0.001

In two of our patients, TORP failure was seen during follow up in case of canal wall down surgery for squamosal case which were posted for revision surgery whereas in two mucosal cases graft uptake failed and we had residual perforation which was managed by endoscopic fat myringoplasty successfully.

Discussion

Ossicular discontinuity is one of the most common manageable cause of conductive hearing loss in COM. In our study 39 (68.42%) patients had mucosal COM and 18 (31.58%) had squamosal COM. In another study by Adhikari et al. 76% patients had mucosal disease while 24% had squamosal COM [9]. In a study by Sharma et al. [3], 90% patients had tubotympanic (mucosal) disease while 10% had atticoantral (squamosal) disease.

Cartilage has been extensively used for tympanoplasty or canal wall reconstruction but its use for ossiculoplasty has been a matter of debate especially in cases with absent stapes. Lack of firmness of cartilage in comparison to bone or metal is been given as the main cause of this. Ideal total ossicular reconstruction material should be biocompatible, stable over the oval window and should produce optimal hearing gain. Ayache et al. [10] referred the reconstruction of ossicular chain from stapes footplate to tympanic membrane as “cartilage ossiculoplasty from stapes to tympanic membrane (COST)”. Although authors like Ayache have tried comparing using cartilage with TORP, there are not many studies comparing cartilage ossiculoplasty with TORP. Ayache found better results using autologous cartilage than PORP with closure of ABG to within 20 dB in 79% of cartilage group compared to 56% of PORP group. They also reported extrusion of PORP which was not seen in use of cartilage. This is in agreement to our results which showed that use of autologous cartilage formed in a shape of umbrella and boomerang gives comparable auditory result to TORP. Its use is associated with a significant improvement in postoperative hearing gain and closure of ABG.

While preparing umbrella we should keep in mind that a uniform thickness disc is created otherwise uneven weight may cause it to be less stable once placed on footplate of stapes. Also, we should be careful that the vertical strut of umbrella is not broader than the size of footplate as an oversized strut will not fit over it is reducing effective sound conduction. Also, the vertical strut should not be too thin and long else it will bend and not transmit the movement of neotympanum effectively to footplate. We achieve it by measuring the cartilage disc and strut using a measuring grid and slicing the cartilage uniformly to size of 1 mm by cartilage slicer [7, 8]. While preparing boomerang it should be kept in mind that overcutting of thickness of cartilage bar may cause the boomerang to break causing graft to fail. One side of perichondrium should y be preserved to reduce chances of this complication. The length of boomerang should be such that it should be reaching the hypotympanum and not stay short else it will not be stable especially in canal wall down procedure.

The reduction in Air bone Gap (ABG) after surgery is taken as the single most important indicator of the success of specific ossicular reconstruction. In our study it was observed that all three procedures achieved adequate improvement in bone conduction, air conduction and reduction in AB Gap. To bridge the transformer mechanism gap, Desarda et al. [11] performed ossicuoloplasty with tragal cartilage and perichondrium in form of L type, T shape, Bow and Boomerang from footplate of stapes to neotympanum. They recorded a success rate of 84%. There was an ABG reduction to levels of 15–20 dB. The follow up of 50% cases for period of 4 year was done. They reviewed the literature and reported that whereas extrusion rates were 3.06% for isografts, 1.19% for autografts, 5.04% for synthetic materials, there was no evidence of extrusion of cartilage prosthesis in their study [12, 13]. Bojrab et al. [14] reported ABG closure to less than 20 dB in 43% cases and Brackmann and Sheely [15] reported ABG closure to within 10 dB in 55% and within 20 dB in 85% cases using TORP. In our study, 100% of patients had ABG closure within 20 dB. In a study by Jha et al. [16], recording audiometric success in terms of ABG reduction after 2 and 5 months of ossicuoloplasty surgery, the success of cartilage was around 57% while that for TORP was 40%. In a study by Gardner et al. [17] TORP success was seen in only 24% of patients undergoing ossiculoplasty. Surprisingly, Acharya et al. reported that all their cartilage L struts failed due to displacement of prosthesis from stapes footplate. They all had a post- op ABG of more than 45 db. In their study, 50% of TORP gave satisfactory ABG reduction and 50% were displaced and extruded [18].

We observed that although hearing gain was better in umbrella technique than boomerang and TORP, the ABG was better in Boomerang and TORP in cases of mucosal disease. Authors suggest that cartilage used in ossiculoplasty undergoes morphological changes and interacts with the surrounding structures giving complete auditory results with passage of time. TORP on other hand undergoes no change like cartilage and therefore gives the ABG result early on after surgery. Boomerang and Umbrella are relatively newer techniques and long term auditory follow up studies need to be done in them for better understanding. We are of opinion that these different techniques result in variation of tympanic membrane movement (due to different area of contact between cartilage and neotympanum in boomerang and umbrella which may cause changes in vibratory area and amplitude of membrane movement) and movement of stapes footplate (cartilage is less rigid than commercial TORP so the pressure exerted on footplate is different) and these may be some underlying mechanism which affect the findings on PTA which being a subjective test relies on feedback of the patient. Such parameters were beyond the scope of this study and authors believe that this is an area for further exploration and more such studies need to be done with larger number of patients and longer follow up (comment 1).

In our study, the maintenance of posterior canal wall was an important prognostic factor identified in squamosal cases for success of various forms of ossiculoplasty grafts. In canal wall up cases, Umbrella gives efficient coupling to the TM for transfer of sound energy, and it also supports the neotympanum creating a voluminous middle ear. Also, the cartilage touches the edge of oval window and posterior canal wall, there is no osteogenesis, seen with autologous ossicles and sometimes with TORP and so hearing outcome is better. In canal wall down cases, Boomerang has an added advantage that one limb of Boomerang is snugly fitting in hypotympanum and so there are less chances of graft displacement and it does not need an intact posterior canal wall for its stability. Audiological success after ossiculoplasty is only partly dependent on the surgical technique or skill. There are various other factors like adhesion formation, neo-osteogenesis and formation of fibrous/ mucosal bands around the prosthesis. These tissue responses compromise the end result by ossicular strut displacement, ankylosis or fixation of footplate of prosthesis and sometimes adhesion of neotympanum.

Extrusion rate of titanium prosthesis has been reported to be between 5 and 20%. This can be reduced by using cartilage. The exclusion rates of cartilage are very minimal as compared to other graft materials. Review of literature highlighted chances to be: Analogous 1.19%, Isografts 3.06%, synthetics 5.04%, human dentine 7.14% and gold prosthesis 8.7% [10]. In allograft prosthesis, extrusion is reported up to as high as 39% of cases [1]. We experienced two cases of TORP failure whereas none of the cartilage’s grafts showed failure till the time of patient follow up. The most common complication implicated with long term results in autograft cartilage graft is contraction or resorption causing displacement resulting in failure of surgery [1].

Some surgeons prefer to stage ossiculoplasty in squamosal cases having cholesteatoma keeping in mind the worsening of hearing after cholesteatoma removal (cholesteatoma hearer). In our setup, most patients are from poor background come from far off rural areas and only a very small percentage of patients turn up for staged surgery. Authors perform majority of mastoid reconstructions as single stage reconstruction after adequate clearing of cholesteatoma and granulations. Authors admit that this factor (effect of cholesteatoma removal on hearing status) was not included in study and may have affected results, and this may be accepted as a shortcoming/ limitation of this study. This factor may be included in further studies as no research is ever complete (comment 3).

Because of small sample size of this study, there is further need of larger study to improve upon the interpretation of results. Also, a study of longer duration is needed to assess sustainability of hearing gain in long term for these promising techniques.

Conclusion

Cartilage ossiculoplasty is a reliable and effective method of ossicular chain reconstruction. In mucosal disease, all the three techniques gave good outcome and the difference in hearing gain was statistically significant between cartilage ossiculoplasty groups and TORP therefore using cartilage can be recommended as it is an autograft and easy to harvest. In cases with squamosal disease significant difference between postoperative hearing gains was present in between various groups based on the type of surgery performed. In canal wall up procedure, the use of cartilage umbrella over TORP or boomerang is recommended. In patients requiring canal wall down procedure, boomerang gave better auditory results than umbrella or TORP. Cartilage ossiculoplasty has the added advantage of reduced chances of TORP extrusion.

Funding

None received.

Declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Informed Consent

A written and explained consent was obtained from all the participants before enrolling them for the study.

Ethical Approval

Ethical clearance was obtained from institutional ethical clearance committee before starting the study involving human participants.