Comparison of 'Lenticular Process of Incus Replacement Prosthesis [LPIRP]' with 'Conventional Autologous Tissue Ossiculoplasty Techniques' in Lenticular Process of Incus (LPI) Necrosis

To compare the outcome of ossiculoplasty using 'lenticular process of incus replacement prosthesis [LPIRP]' with that of 'conventional autologous tissue ossiculoplasty techniques' in patients with lenticular process of incus necrosis [LPI] in terms of: 1. Hearing results. 2. Graft take-up. 3. Complications like extrusion. Total 16 patients found intraoperatively to have LPI necrosis were allocated randomly using (simple random sampling technique) in two groups. Total 8 patients in group A underwent ossicular chain reconstruction using titanium prosthesis-LPIRP (manufactured by Decibel's gold prosthesis pvt. ltd.) and total 8 patients in group B underwent ossicular chain reconstruction using autologous cartilage/cortical bone. At the end of 4 weeks status of graft uptake was assessed and follow up pure tone audiogram [PTA] was performed at average 4th, 12th and 24th post-operative week. No significant difference in mean hearing gain (i.e. air-bone conduction gap closure) between two groups at 1 month, 3 months and 6 months post operatively [p > 0.05]. However postoperative 3 months and 6 months results have better air bone conduction gap closure in group A as compared to group B. Titanium LPIRP prosthesis can be a good alternative in patients undergoing ossiculoplasty where autografts are not available for ossicular reconstruction or there is inadequate surgical expertise for remodelling autologous bone/cartilage.

Keywords: Ossiculoplasty; Lenticular process of incus necrosis; Titanium LPIRP; Tragal/conchal cartilage; Hearing outcome; Air bone gap closure

One of the most intriguing topics in middle ear surgery is the reconstruction of the conductive mechanism. Ever since matte's [[1]] first myringostapediopexy in 1901, there has been a quest for the ideal middle ear implant. The plethora of prostheses available is witness to the ongoing research for the 'ultimate prosthesis'. The ideal middle ear prosthesis is the one, that is light, versatile, biocompatible and is able to reproduce and perhaps improve upon the natural impedance matching system at key hearing frequencies. Initially, autografts and allografts were the ossicular replacement material used most widely by otologists. However, because of the fear of prion disease (including creutzfeldt-jakob disease), use of allografts came to a near halt. Autografts in form of cartilage [conchal/tragal] and remodelled mastoid cortical bone are still being used for ossiculoplasties. The advent of various bio-inert prosthetic materials has witnessed a shift in favour of prosthetic implants over last few decades. Today, the otologist has a wide array of middle ear implants from which to choose but may find it difficult to know which works best. It is clear, however, that optimal results in ossicular reconstruction depend not only on the qualities of the prosthesis, but also on the environment in which it is placed and the surgical techniques used.

Titanium is an excellent biocompatible material. It has proved to be a suitable material for ossicular reconstruction because of its biostability and low ferro magneticity. Titanium is light and strong, allowing versatility in the prosthetic design; thus, the prosthesis can be thin and yet rigid making it a good sound conductor [[2]].

This study was conducted at the department of E.N.T. and Head-Neck Surgery, Medical College and Sir Sayajirao General Hospital, Vadodara. The study period was from November 2016 to November 2018. All patients of chronic suppurative otitis media were assessed with detailed history, systemic examination, comprehensive E.N.T. examination, pure tone audiometry and microscopic examination of ear. Patients found intraoperatively to have lenticular process of incus necrosis were allocated equally to either group A- titanium prosthesis group or group B-cartilage/bone interposition group using a simple randomization process. Patients in the titanium prosthesis group underwent ossicular chain reconstruction using titanium prosthesis-LPIRP (manufactured by Decibel's gold prosthesis pvt. Ltd.) and patients in cartilage/bone interposition group underwent ossicular chain reconstruction using autologous cartilage/cortical bone. Ethical approval was obtained from the Institutional Ethics Committee for Research on Humans of Medical College Baroda, Vadodara. Written informed consent was obtained from all participants using a standardised consent form approved by the ethics committee.All surgical procedures were performed under general anaesthesia along with 20 cc normal saline with 8 drops (24 G 1.5 inch needle) of 1 in 100,000 adrenaline infiltration into four quadrants of the canal wall at the bony cartilaginous junction and at the retroauricular groove. A Wilde's post-aural incision was made about 5 mm behind the retroauricular groove, extending from the highest point of attachment of the pinna to the tip of the mastoid. A temporalis fascia graft was then harvested and standard tympanomastoidectomy or tympanoplasty was performed to clear disease from the middle-ear cleft prior to ossicular reconstruction. Takagi surgical operating microscope was used for all surgeries. All patients were discharged next day after surgery. Follow up dressings were done on 5th postoperative day and suture removal was done on 7th postoperative day. Patients were given oral antibiotics [Cefpodoxime 5 mg/kg/dose 12 hourly + Clavulanic acid 125 mg 12 hourly] and decongestant analgesic [Paracetamol 15 mg/kg + Chlorpheniramine Maleate 250/micrograms/kg in 3 divided doses] for 3 weeks. At the end of 4 weeks the canal was cleared of gel foam and status of graft uptake was assessed. Follow up PTA was performed at average 4th, 12th and 24th post-operative week. All audiograms were done by the same audiologist in sound proof audiology room of the department. The audiometer used was MAICO MA 53 and was calibrated regularly.

Anatomical results i.e. closure of tympanic membrane perforation, graft take up (examined otomicroscopically) and PTA evaluations were analysed after mean 1 month, 3 months and 6 months postoperatively.Comparison of pre-operative and post-operative pure tone average of air bone conduction gap closure were performed at frequencies 0.5, 1, 2, 4 kHz. All the relevant data was entered in the MS Excel sheet 2016 & tabulated accordingly. Appropriate statistical tests were applied to determine the outcome of the comparative study. For quantitative parameters, the mean, median and standard deviation were calculated. Student's t-tests (unpaired) were used to determine significant differences in hearing outcome between the two groups. Paired t-tests were used to compare pre and post-operative hearing results within each group. Statistical significance was set at a p value less than 0.05.

As mentioned in Table 1, there were total 5 males [group A = 3 group B = 2] and 11 females [group A = 5 group B = 6] subjects in this study. Total of 8 Patients [group A = 4 group B = 4] were operated for right ear surgery and an equal number of patients [group A = 4 group B = 4] got their left ear operated. All ossiculoplasties were performed during primary operation. In Groups A and B mean age of patients was 36.37 years and 28.25 years, respectively. In Group A, 3 patients [37.5%] were males as compared to 2 patients [25%] in Group B. In Group A, 5 patients [62.5%] were females as compared to 6 patients [75%] in Group B. Preoperative mean air–bone gap was 27.27 dB (standard deviation [SD] = 5.09) in Group A as compared to 30.375 dB (SD = 9.13) in Group B. These intergroup variables were not statistically significant. Tables 2 and 3 showed pre-operative and post-operative air bone gap at 1 month, 3 months and 6 months in group A and group B respectively.

Basic characteristics of two groups

pre-operative and post-operative air bone gap at 1 month, 3 months and 6 months in group A

pre-operative and post-operative air bone gap at 1 month, 3 months and 6 months in group B

Table 4 show inter-group post-operative air-bone conduction gap [ABG] closure comparison. In our study, at 1 month, mean ABG closure was 6.75 dB (7.08 SD) in group A and 9 dB (5.63 SD) in group B. At 3 months mean ABG closure was 12.625 dB (7.85 SD) in group A and 10.375 dB (6.84 SD) in group B, whereas at 6 months mean ABG closure was 14 dB (6.07 SD) in group A and 13.375 dB (6.92 SD) in group B.

Inter-group comparision of postoperative mean air bone gap closure at 1 month, 3 months and 6 months

Graph

The numerous techniques and middle ear prostheses available to otologic surgeon lend credence to the idea that ossicular chain reconstruction techniques remain to be perfected [[3]]. For more than five decades, otologists have been in search for perfect prostheses. Three general classes of prostheses are used today: autograft, homograft, and allograft [[4]]. Autograft prostheses include ossicles (incus, malleus), cartilage and cortical bone. The autograft prostheses have a very low extrusion rate, no risk of transmitting disease, biocompatibility and no necessity for reconstitution. Displacement, complete absorption, small remnant size and possibility of harbouring microscopic disease have been cited as potential disadvantages to their use [[5]]. Various new alloplastic prostheses made up of plastic, ceramic, teflon, wire prosthesis such as stainless steel, tantalum, platinum, hydroxyapatite and titanium are in use, but none had fit in the criteria of an ideal graft. Extrusion of the prostheses is reported as high as 39% and can be significantly reduced by placing cartilage or bone between the tympanic membrane and the prostheses [[6]]. In our study Decibel's titanium lenticular process of incus replacement prosthesis-LPIRP and autologous conchal cartilage/tragal cartilage/mastoid bone chip was used as ossiculoplasty material. Anatomical and functional results were compared between two groups. The postoperative follow up period was 6 months. We found that overall graft take up rate was better in prosthesis group. The hearing assessment postoperatively was done at mean 1 month, 3 months and 6 months. We found no statistically significant difference in mean air bone conduction gap closure between two groups at 1 month, 3 months and 6 months post operatively [p > 0.05]. However, post operative 3 months and 6 months results have better air bone conduction gap closure in prosthesis group as compared to autologous conchal cartilage/tragal cartilage/mastoid bone chip used group (though not statistically significant because of low number of patients in each group). Intra group air bone conduction gap closure were significant in both groups at end of post operative 1 month, 3 months and 6 months [p < 0.05].

Amith I Naragund et al. [[7]], carried out study on 24 patients comparing autograft incus and titanium prosthesis in primary ossiculoplasty for hearing gain. All patients were divided in two groups [each of 12 patients] for ossiculoplasty with autograft incus and ossiculoplasty with titanium prosthesis. Mean age of patients was 22.75 years and 23.25 years in autologous incus group and titanium prosthesis group respectively as compared 28.25 years and 36.38 years in cartilage/bone group and titanium prosthesis group respectively in our study. There were 50% male, 50% female in autograft incus group as compared to 25% male, 75% female in cartilage/bone used group in our study. There were 58.38% male, 41.67% female in titanium prosthesis group as compared to 37.5% male, 62.5% female in prosthesis used group in our study. Preoperative mean air bone gap was 43.3 dB [SD = 8.34] in autograft incus group as compared to 30.37 dB [SD = 9.13] in our cartilage/bone used study group. However preoperative mean air bone gap was 42 dB [SD = 5.7] in titanium prosthesis group as compared to 27.25 dB [SD = 9.05] in our LPIRP used group. At 6th postoperative month mean air-bone conduction gap closure was 25 dB in prosthesis group and 24.5 dB in autograft incus group as compared to 14 dB in LPIRP used group and 13.37 dB in cartilage/bone used group in our study.

There was no graft extrusion with residual perforation in autograft incus group as compared to 2 graft extrusion with residual perforation in our study group of cartilage/bone used group. There were 2 case of graft extrusion with residual perforation noted in titanium prosthesis group as compared to no graft extrusion with residual perforation in our LPIRP used group.

Naragund Amith et al. [[8]], carried out study on 40 patients comparing autograft incus and titanium prosthesis in primary ossiculoplasty for hearing gain. All patients were divided in two groups [each of 20 patients] for ossiculoplasty with autograft incus and ossiculoplasty with titanium prosthesis. Mean age of patients was 24 years and 25 years in autologous incus group and titanium prosthesis group respectively as compared 28.25 years and 36.38 years in cartilage/bone group and titanium prosthesis group respectively in our study. There was 65% male, 35% female in autograft incus group as compared to 25% male, 75% female in cartilage/bone used group in our study. There was 45% male, 55% female in prosthesis group as compared to 37.5% male, 62.5% female in prosthesis used group in our study.

Preoperative mean air bone gap was 42.14 dB (standard deviation [SD] = 6.96) in autograft incus group as compared to 30.37 dB [SD = 9.13] in our cartilage/bone used study group. However preoperative mean air bone gap was 44.37 dB (standard deviation [SD] = 9.54) in titanium prosthesis group as compared to 27.25 dB [SD = 9.05] in our LPIRP used study group.

At 6 months postoperative mean air-bone conduction gap closure was 13.05 dB in prosthesis group and 17.91 dB in autograft incus group as compared to 14 dB in LPIRP used group and 13.37 dB in cartilage/bone used group in our study.

There was no graft extrusion with residual perforation in autograft incus group as compared to 2 graft extrusion with residual perforation in our cartilage/bone used group. There was 3 case of graft extrusion with residual perforation noted in titanium prosthesis group as compared to no graft extrusion with residual perforation in our LPIRP used group.

Very few randomized clinical trials from the Indian subcontinent are available in literature comparing hearing outcome of ossiculoplasty with autologous incus and titanium prostheses and, therefore, there is scope for more similar studies with longer follow-up in near future.

An isolated ossicular defect of 'Lenticular Process of Incus Necrosis' can be reconstructed with multiple techniques. Reconstruction in these cases by 'Remodelled Autologous Cartilage' or 'Remodelled cortical bone chip' has stood the test of time. Titanium LPIRP has lately been introduced as a prefabricated reconstruction material in cases with such isolated ossicular defects. This prosthesis reduces the time consumed and doesn't need the expertise needed for remodelling the Bone chip/ Cartilage and moreover gives comparable results. The graft uptake in cases where LPIRP is used is similar and sometimes even better than cases where conventional bone chip/ cartilage was used. Although the hearing improvement starts earlier in Cartilage/Bone ossiculoplasty cases but the peak attained is lower than LPIRP cases. Results in terms of air bone conduction gap closure are analogous after 6 months for both LPIRP and Cartilage/Bone ossiculoplasties. Cost and size mismatch (as the said prosthesis is available in only one size) can be the unfavourable factors for not allowing widespread LPIRP use. It is worthwhile to conclude that many more clinical trials with a larger study group and a longer follow-up are required to establish the above results more firmly. Inspite of the unfavourable factors, Titanium LPIRP prostheses can be a good alternative in patients undergoing ossiculoplasty where autografts are not available for ossicular reconstruction or there is inadequate surgical expertise for remodelling autologous Cartilage/Bone.

There was no source of external funding. All expense of prosthesis used in surgery was done by authors.

I am thankful to our beloved Head of Department, Dr. Ranjan G. Aiyer, and Associate Professor Dr. Rahul Gupta, for providing me excellent infrastructure for conducting the study. I am also thankfull to Dr.Nikhil Patel, Dr.Jayman Raval, Dr.Hitesh Gangani and Dr.Anand Palas, for encouraging me to involve in research. We thank our statistician, Dr.Vidhi Parmar, for helping us in statistical analysis of the data.

All data used in study was taken from hospital records of patients operated in Department of E.N.T. Head-Neck Surgery, Baroda Medical College, Sir Sayajirao General Hospital with prior approval from ethics committee.

All the authors declare that they have no conflict of interest in the submission of this manuscript.

All procedures performed in the study involving human participant were in accordance with the ethical standards of the institutional research committee and ethical standards.

This article does not contain any studies with animals performed by any of the authors.

Informed consent was obtained from all individual participants included in the study.

All authors has given consent for publication.

• LPIRP

• Lenticular process of incus replacement prosthesis

• LPI

• Lenticular process of incus

• PTA

• Pure tone audiogram

• E.N.T.

• Ear nose throat

• ABG

• Air bone conduction gap

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