Audiologic Results of Ossiculoplasty Using Malleus Footplate Assembly: The Comparison between Autologous Incus and Hydroxyapatite

Abstract

Introduction A disruption of the ossicular chain of the middle ear causes conductive hearing loss. Ossicular reconstruction is performed to restore hearings in those patients with congenital ossicular chain anomaly or ossicular chain disruption caused by chronic otitis media or cholesteatoma. A study from Japan with 52 auditory ossicular malformation revealed that 44% of the patients had a fixation of the stapes, 40% had incudostapedial joint defects followed by fixation of the malleus and/or incus and defects in the incudostapedial joint with a fixation of the stapes.1) One of the most common ossicular chain anomalies in Korea was a stapes footplate fixation (54.5%) followed by a mobile stapes footplate with other anomalies (19.7%) including a stapes without suprastructure and an incus long process, stapes without anterior crus and an incus long process.2) One of the most common ossicular chain anomalies is the absence of an incus with or without an intact stapes suprastructure. In incudostapedial deformed ears, ossiculoplasty is mandatory to restore the hearing process. Ossiculoplasty is also needed in cases with incus long process erosion with inflammation. As the most vulnerable ossicles, one report said that incus erosion is found in 80% of the chronic otitis media.3) Austin-Kartush classified ossicular chain disruptions into four categories after 1,151 operation on chronic otitis media. Group A ears with an intact malleus handle and a stapes suprastructure was found in 59.2% followed by group B ears with an intact malleus handle but an eroded stapes suprastructure group.4) In the group of a tympanic membrane and malleus preserved but a stapes suprastructure eroded, ossicular continuity can be restored between the stapes footplate and manubrium of the malleus with the method of malleus footplate assembly (MFA) using either the incus body or if the incus is unavailable, a biocompatible material such as hydroxyapatite (HA).5,6,7) Until now, MFA has proven to be the safe and effective way to restore hearings in such patients.8,9,10,11,12)Though successful results using MFA with either incus body or biocompatible material are reported world widely, there were a few reports on audiologic results after MFA ossiculoplasty in Korea. Authors reviewed our procedure and report hearing results of ossiculoplasty with MFA using either incus or HA. In this paper, a single-surgeon series of 32 MFA operations was analyzed. The cases were limited to autologous interposition grafts performed on Austin-Kartush group B ears in order to provide consistency within the analysis. Subjects and Methods Data collection A retrospective evaluation has been carried out on patients who underwent MFA ossiculoplasty between September 2001 and March 2010 in Seoul National University Hospital. A total of 55 patients with Austin-Kartush type B defect repaired with incus body or HA were identified. Of those, 20 were excluded due to a failure to recover operation records or a lack of no more than 1 year postoperative audiograms. Three patients who had undergone MFA with a homologous incus were excluded in order to provide consistency within the analysis. Finally, 32 cases were enrolled into the study. All procedures were conducted by a single surgeon. All data including previous operations, follow-up duration, age, sex, etiology, materials which were used in the operation, combined mastoidectomy, complications, and revision operations were analyzed. Eustachian tube function was analyzed according to the results of the Eustachian tube test. The status of the middle ear mucosa was described as either 'healthy' or 'inflamed' according to the operation records. Demographic data are presented in Table 1. Analysis of audiologic data Preoperative and postoperative hearing results were evaluated according to the guidelines of the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head Neck Surgery Foundation13) and Classification and Hearing Result Reporting Guideline in Chronic Otitis Media Surgery published in 2006, Korea.14) The air conduction (AC), bone conduction (BC) as well as air-bone gap (ABG) at 0.5, 1, 2, and 3 kHz were calculated before surgery and at 3 months, 6 months, 1 year, and 2 years after surgery. Closure of the average ABG to within 20 dB was defined as successful outcomes in this study. Operation methods Ossicular reconstruction was performed using either autologous incus body or the HA. Autologous incus was used in 17 cases and HA was used in 15 cases. The prosthesis was fitted between the malleus neck and the footplate. The tendon of the tensor tympani was severed to facilitate insertion of the prosthesis and to relieve tension in the reconstruction system. The distance between the malleus and the footplate was measured to decide on the adequate length of the incus body or the HA. When the incus body is remained and useful, it was removed and remodeled. A groove was made on the incus acetabulum with a 1 mm diamond burr for positioning of the malleus handle. If the incus was not feasible, HA was used with a groove on the head of the HA. The shaft of the HA was placed on the footplate and sliced tragal cartilage was interposed between the HA and the tympanic membrane to prevent prosthesis extrusion. Statistical analysis SPSS version 18.0 software (SPSS, Chicago, IL, USA) was used for analyses and a p-value<0.05 was considered to be significant. The preoperative and postoperative hearing results were compared using Wilcoxon signed rank test. The hearing results between incus and HA were compared using Mann-Whitney U test and Fisher's exact test. Audiologic results among etiologies were analyzed using Kruskall-Wallis test. Ethic consideration The study was approved as a review exemption by Institutional Review Board of Seoul National University Hospital, Seoul, Korea. Results Demographic data of MFA patients with either incus and HA are presented in Table 1. Age ranged from 3 to 63 years. Mean follow-up period was 32.6±20.8 months. Three patients underwent revision ossiculoplasty due to the unsatisfactory hearing results. The ossicular chain reconstruction was performed during the second stage of a planned two-stage procedure in two patients diagnosed as congenital cholesteatoma and one patient with chronic otitis media with cholesteatoma. Twenty-two patients (68.8%) underwent MFA without mastoidectomy. Canal wall up mastoidectomy was performed in 8 patients (25.0%) and canal wall down mastoidectomy, in 2 patients (6.2%). The etiology of the ossicular disruption was ossicular chain anomaly in 13 patients (40.6%), congenital cholesteatoma in 9 patients (28.1%), chronic otitis media with cholesteatoma in 8 patients (25.0%), and chronic otitis media in 2 patients (6.3%). Preoperative valsalva results and Eustachian tube function test, intraoperative middle ear mucosa status, and combined mastoidectomy, which can affect the result of the operation, were analyzed using Fisher's exact test and there were no significant statistical differences between the incus and the HA groups. Mean preoperative AC was 48.7±10.7 dB with a range of 24 to 66 dB. Mean preoperative BC was 11.9±7.5 dB with a range of 1 to 35 dB. Mean preoperative ABG was 37.9±9.3 dB with a range of 16 to 58 dB and there was no significant statistical difference between the incus and HA groups. Significant improvements in AC and ABG were observed at 3 months, 6 months, 12 months and 24 months after the operation, compared with preoperative pure tone audiometry. There was no significant change in BC before and after the surgery (Fig. 1). The closure of ABG to within 20 dB occurred in 59.3% of the patients at postoperative 1 year and 73.9% at postoperative 2 years. Although there was no statistical significance of postoperative ABG, the HA group showed a smaller ABG, compared to the incus group (14.8±11.6 dB in HA and 19.4±12.3 dB in incus in 2 years; p=0.563)(Fig. 2). Audiologic results were compared according to the etiology. Postoperative 3 months and 1 year ABG showed statistically significant decrease in ossicular chain anomaly, compared to other disease entities (p=0.002 and p=0.012, respectively)(Fig. 3). Although no significant difference of postoperative ABG was observed between the primary and the revision ossiculoplasty, the primary cases showed smaller ABG than the revision cases in postoperative 1 year and 2 years (p=0.161 and p=0.294, respectively)(Fig. 4). There was no significant difference between the combined tympanomastoidectomy and the tympanoplasty (p=0.555). There was no prosthesis extrusion as a complication. However, 6 patients needed revision surgery due to poor surgical audiologic outcomes. Among them, 4 cases previously had performed the MFA with incus body, and 2 cases, with the HA. One of the incus bodies was displaced and replaced to the HA and showed better hearing results after the revision surgery. The other three incus bodies also showed displacement and were realigned. The revision surgery included adhesiolysis and rearrangement in one HA case due to fibrous tissue around the prosthesis and the other HA was remodeled and realigned in the revision surgery. One patient underwent the revision surgery due to a recurrence of chronic otitis media with cholesteatoma. Discussion In 1978, Austin15,16) identified five categories of anatomic defects in the middle ear sound-conducting system and described them. According to the classification, an ossicular interruption with an intact tympanic membrane resulted in a maximal conductive hearing loss of 55 to 60 dB. An intact eardrum reflected sound energy back into the external auditory canal, causing an additional 17 dB conductive loss beyond what was expected from the removal of the hydraulic and catenary lever action. The decreased sound pressure also reached the round and oval windows nearly simultaneously, inducing a phase cancellation in the labyrinthine fluids. To restore the ossicular chain, many techniques have been proposed. Mostly, long columella using an autologous incus or a total ossicular reconstruction prosthesis (TORP) is used in the case of the absence of a stapes suprastructure and an incus long process between the tympanic membrane and the stapes footplate.3) Though these methods are effective in reestablishing hydraulic lever action, a catenary lever action, which yields a two-fold hearing gain, cannot be established by a long columella or TORP. Theoretically using MFA between the malleus and stapes footplate can convey sound from the tympanic membrane to the malleus and then the stapes footplate, and can obtain the catenary effect. It is supposed to be the audiologically physiologic method of sound transfer. A study on a cadavaric model has reported that a malleus to stapes head sound transfer with the HA was better than a tympanic membrane to stapes head sound transfer.17) These results suggest that malleus is more important for the middle ear mechanics than stapes although stapes attributes the stability of ossicular prosthesis. In our study, two MFA methods were compared. Though the results were not compared with long columellization or TORP, similar results are expected and will be continued in our future study. Among the two MFA methods, no significant differences were found between the incus and the HA groups. However, there was a tendency of decreasing ABG in the HA group, compared to the incus group in postoperative 2 years. When exploring the cases with revision, 4 cases were the incus MFA cases, compared to the 2 cases of HA MFA cases. Most of them were due to a displacement of the MFA and one HA needed adhesiolysis due to fibrous tissue. It is suspected that though a groove was made for the placement for the malleus handle, the alignment can be changed during the absorption period of inner packings and during postoperative activity. As HA is very symmetrical and premade in its shape, it is suspected that displacement rarely occurs. The authors regarded that HA can result in much inflammation or fibrosis due to biological reactions, but, at the operation field of revision surgery, only one HA case had adhesion with soft tissue. Thus, a longer follow-up with audiologic results is mandatory. The ideal prosthesis is considered to be easy for modeling and handling, biocompatible, stable after the ossiculoplasty and delivers optimal sound. HA is easy to insert and remodel although a possibility of decreased biocompatibility and some rate of immunologic reaction exist18,19) and cost is higher compared to autologous incus. On the other hand, autologous incus is biocompatible so there is a reduced risk of inflammation or immunologic reaction and does not increase price. However, it is time consuming work to prepare autologous incus with the sculpturing of an appropriate shape. A homologous ossicular prosthesis could be another option, but there is a risk of transmitted disease such as hepatitis, syphilis, AIDS, and Creutzfeldt-Jacob disease.20) In this study, a homologous incus was excluded due to suspicious different demineralization rate with an autologous incus by time. Comparison among the etiology showed that ossicular chain anomaly showed the best audiologic result in postoperative 3 months and 1 year. The reason is considered to be that an ossicular chain anomaly has relatively normal Eustachian tube function and healthy middle ear mucosa compared to chronic otitis media with cholesteatoma, congenital cholesteatoma, or chronic otitis media. The authors can suspect that when the middle ear mucosa appears healthy and well aerated, ossicular chain reconstruction can be done with the highest rate of success. The closure of ABG to within 20 dB was obtained in 59.3% in one year (16/27) and 73.9% (17/23) in 2 years. The success rate was similar to the previous study with 73.5% in 1 year and 70.8% in 5 years.3) The success rate of an incus MFA was 46.7% in 1 year, 70.0% in 2 years. On the other hand, the success rate of HA MFA was 75.0% in 1 year, 76.9% in 2 years. ABG greater than 30 dB was 7.4% in 1 year and 13.0% in 2 years postoperatively. Extrusion is often reported as a complication in ossiculoplasty. A study on the extrusion rate of 5 years with HA showed the results vary from 0.9% to 4%.21,22) There was no data for autologous extrusion rate, but a recent study mentioned on homologous prosthesis with the data of 2%.23,24) In our study, however, there were no extrusion cases. It is suspected that tragal cartilage interposition which can avoid direct contact of prosthetic materials with the tympanic membrane and drum erosion works well to prevent the extrusion of the prosthesis. However, a long-term follow-up is needed to draw the 5 year results. Conclusion There was no ABG difference in between incus and HA, but reasonable hearing gain was obtained in either method. In the MFA, either incus or HA can be an option to restore hearing in patients with erosion of an incus long process or ossicular chain anomaly. REFERENCES: 1.Hashimoto S, Yamamoto Y, Satoh H, Takahashi S. Surgical treatment of 52 cases of auditory ossicular malformations. Auris Nasus Larynx 2002;29:15-8. 2.Park K, Choung YH. Isolated congenital ossicular anomalies. Acta Otolaryngol 2009;129:419-22. 3.Colletti V, Fiorino FG. Malleus-to-footplate prosthetic interposition: experience with 265 patients. Otolaryngol Head Neck Surg 1999;120:437-44. 4.Austin DF. Ossicular reconstruction. Otolaryngol Clin North Am 1972;5:145-60. 5.Wehrs RE. Homograft ossicles in tympanoplasty. Laryngoscope 1982;92:540-6. 6.Colletti V, Fiorino FG, Sittoni V. Minisculptured ossicle grafts versus implants: long-term results. Am J Otol 1987;8:553-9. 7.Goldenberg RA. Hydroxylapatite ossicular replacement prostheses: results in 157 consecutive cases. Laryngoscope 1992;102:1091-6. 8.Martin TP, Weller MD, Kim DS, Smith MC. Results of primary ossiculoplasty in ears with an intact stapes superstructure and malleus handle: inflammation in the middle ear at the time of surgery does not affect hearing outcomes. Clin Otolaryngol 2009;34:218-24. 9.Grote JJ. Reconstruction of the ossicular chain with hydroxyapatite prostheses. Am J Otol 1987;8:396-401. 10.Mills RP. Hearing results in tympanic membrane footplate and malleus-footplate assemblies. Clin Otolaryngol Allied Sci 1995;20:522-3. 11.Black B. Spanner malleus-stapes/footplate assembly. Laryngoscope 1994;104:775-7. 12.Vercruysse JP, Offeciers FE, Somers T, Schatteman I, Govaerts PJ. The use of malleus allografts in ossiculoplasty. Laryngoscope 2002;112:1782-4. 13.Committee on Hearing and Equilibrium guidelines for the evaluation of results of treatment of conductive hearing loss. American Academy of Otolaryngology-Head and Neck Surgery Foundation, Inc. Otolaryngol Head Neck Surg 1995;113:186-7. 14.Kim HJ. Classification and hearing result reporting guideline in chronic otitis media surgery. Korean J Otolaryngol-Head Neck Surg 2006;49:2-6. 15.Austin DF. Sound conduction of the diseased ear. J Laryngol Otol 1978;92:367-93. 16.Austin DF. Acoustic mechanisms in middle ear sound transfer. Otolaryngol Clin North Am 1994;27:641-54. 17.Bance M, Morris DP, Vanwijhe RG, Kiefte M, Funnell WR. Comparison of the mechanical performance of ossiculoplasty using a prosthetic malleus-to-stapes head with a tympanic membrane-to-stapes head assembly in a human cadaveric middle ear model. Otol Neurotol 2004;25:903-9. 18.Smyth GD. Five-year report on partial ossicular replacement prostheses and total ossicular replacement prostheses. Otolaryngol Head Neck Surg 1982;90:343-6. 19.Merritt K, Shafer JW, Brown SA. Implant site infection rates with porous and dense materials. J Biomed Mater Res 1979;13:101-8. 20.Glasscock ME 3rd, Jackson CG, Knox GW. Can acquired immunodeficiency syndrome and Creutzfeldt-Jakob disease be transmitted via otologic homografts? Arch Otolaryngol Head Neck Surg 1988;114:1252-5. 21.Goldenberg RA. Hydroxylapatite ossicular replacement prostheses: a four-year experience. Otolaryngol Head Neck Surg 1992;106:261-9. 22.Truy E, Naiman AN, Pavillon C, Abedipour D, Lina-Granade G, Rabilloud M. Hydroxyapatite versus titanium ossiculoplasty. Otol Neurotol 2007;28:492-8. 23.Wehrs RE. The homograft tympanic membrane after 12 years. Ann Otol Rhinol Laryngol 1982;91:533-7. 24.Schuring AG, Lippy WH. Solving ossicular problems in tympanoplasty. Laryngoscope 1983;93:1151-4.