- Email: [email protected]
Ossicular reconstruction using hydroxyapatite prostheses with interposed cartilage
Ossicular Reconstruction Using Hydroxyapatite Prostheses With Interposed Cartilage Taisuke Kobayashi, MD, Kiyofumi Gyo, MD, Takayuki Shinohara, MD, and Naoaki Yanagihara, MD Purpose: Despite the excellent biocompatibility of hydroxyapatite ossicular prostheses, extrusion of the prosthesis may be found during long-term follow-up, mainly due to the retraction of the eardrum. Although interposition of autologous cartilage between the eardrum and the prosthesis is empirically used to prevent extrusion, the clinical effect of this procedure has not been confirmed. The purpose of this study was to evaluate the effect of interposing a cartilage on the extrusion rate and hearing outcome. Materials and Methods: Fifty-four ears in which cartilage was interposed with a hydroxyapatite prosthesis were compared with 53 ears without interposition. Three years after surgery, the otoscopic findings and hearing outcome were evaluated. Results: The extrusion rate was 1.9% in the group with interposition and 13.2% in the group without interposition. The difference between the two groups was statistically different (2 ⫽ 4.986; P ⫽ .03). There was no significant difference between the two groups in the postoperative air-bone gap. Conclusion: This procedure is an effective method for reducing the extrusion rate of hydroxyapatite prostheses without reducing the hearing gain resulting from ossiculoplasty. (Am J Otolaryngol 2002;23:222-227. Copyright 2002, Elsevier Science (USA). All rights reserved.)
Hydroxyapatite (HA) prostheses are widely used for ossicular reconstruction because of their excellent biocompatibility.1,2 Compared with ossicular prostheses of other materials, the extrusion rate of the HA prosthesis is considered to be low. Nevertheless, extrusion is seen during long-term follow-up. To prevent extrusion, we have interposed sliced cartilage between the prosthesis and the eardrum since 1990. Although this method is empirically assumed to be effective, this conclusion has not been confirmed by long-term follow-up study. The purpose of this study was to evaluate the effect on the extrusion rate and hearing outcome of interposing a cartilage graft between the HA prosthesis and the eardrum. From the Department of Otolaryngology, Ehime University School of Medicine, Ehime, Japan. This paper was presented at the 4th Extraordinary International Symposium on Recent Advances in Otitis Media, Sendai, Japan, April 16-20, 2001. Address correspondence to Taisuke Kobayashi, MD, Department of Otolaryngology, Ehime University School of Medicine, Shigenobu-cho, Onsen-gun, Ehime 7910295, Japan. E-mail: [email protected]. Copyright 2002, Elsevier Science (USA). All rights reserved. 0196-0709/02/2304-0001$35.00/0 doi:10.1053/ajot.2002.124191 222
MATERIALS AND METHODS Patients Between April, 1990, and March, 1997, ossicular reconstruction using HA prostheses with interposition of cartilage was carried out in 74 ears. Of these reconstructions, 54 ears were able to be followed-up for more than 3 years. The patients’ ages ranged from 8 to 68 years with a mean age of 42 years. The pathology in the group included middle ear cholesteatoma in 41 ears (76%) and chronic otitis media in 13 ears. The surgical results for this group were compared with the results for a second group that had undergone ossiculoplasty with HA prostheses but without interposition of cartilage between 1982 and 1989. Although the number of ears operated on was 79, 53 ears were followed up for more than 3 years. These patients were the subjects of the second group. Their ages ranged from 6 to 65 years with a mean age of 35 years. The pathology in the second group included middle ear cholesteatoma in 36 ears (68%) and chronic otitis media in 17 ears. This study compared the 2 groups after the same 3-year follow-up period.
Surgical Procedures Two types of Apaceram (Pentax Asahi Optical Co., Ltd., Tokyo, Japan) HA prostheses were used for the ossiculoplasties. The type P Apaceram (Fig 1a) is a partial ossicular replacement prosthesis (PORP), designed to be positioned between the
American Journal of Otolaryngology, Vol 23, No 4 (July-August), 2002: pp 222-227
HYDROXYAPATITE PROSTHESIS
223
Fig 1. (a) Type P hydroxyapatite prosthesis. (b) Type T hydroxyapatite prosthesis. (c) The length of the prosthesis shaft was adjusted by a diamond bar. (d) The sliced cartilage with perichondrium (arrow) was placed on the head of the hydroxyapatite prosthesis; PW, posterior wall of external auditory canal.
stapedial head and the eardrum; the type T Apaceram (Fig 1b) is a total ossicular replacement prosthesis (TORP), designed for interposition between the stapedial footplate and the eardrum. To get an appropriate tension between the stapes and the eardrum, the length of the prosthesis shaft was adjusted by an umbrella type diamond bar (Fig 1c). The interposed cartilage including the perichondrium was obtained from the concha of the patient’s ipsilateral auricle. Fibrin glue was usually used to attach the cartilage and HA prostheses (Fig 1d). Hearing reconstruction following mastoidectomy was carried out most often as a planned 2-stage operation. Eighty-five percent of the cases were operated on with a 2-stage tympanoplasty in the group without interposed cartilage, 83% in the group with interposition. Canal wall reconstruction was not carried out in patients who previously had been operated on with a canal wall down technique. Thus, 3 ears in the group without interposition and 8 ears in the group with interposition underwent canal wall down tympanoplasty. Two of the senior authors (K.G. and N.Y.) carried out the operations in both groups.
Postoperative Follow-up In postoperative follow-up, the ear was observed under a surgical microscope by the surgeons. In the audiologic evaluation, pure tone air and bone conduction thresholds were obtained before the first stage operation and 6 months, 1 year, and 3 years after the second stage operation. The average thresholds at 500, 1,000, and 2,000 Hz were used to calculate the air-bone gap to evaluate hearing outcome.
RESULTS Extrusion The otoscopic findings 3 years after surgery are presented in Table 1. In the group without interposition, good findings were seen in 37 ears (70%), whereas extrusion of the prosthesis occurred in 7 ears (13%) between 10 and 22 months after the operation. The extruded
224
KOBAYASHI ET AL
TABLE 1. Otoscopic Findings 3 Years after Surgery
Good Retracted eardrum Cholesteatoma recurrence or adhesion Extrusion of HA Total
HA, No. of Ears (%)
HA ⫹ Cartilage, No. of Ears (%)
37 (70) 6 (11)
45 (83) 6 (11)
3 (6) 7 (13) 53 (100)
2 (4) 1 (2) 54 (100)
Abbreviation: HA, hydroxyapatite prosthesis.
prostheses included 1 PORP and 6 TORPs. Extrusion occurred as a result of inflammation in 1 ear and of cholesteatoma recurrence or adhesion of the eardrum in 6 ears. In the interposed group, good findings were observed in 45 ears (83%) and an extrusion in 1 ear in which a TORP prosthesis was extruded 29 months after surgery due to inflammation. The extrusion rate in the group with interposition was 1.9%, whereas that of the group without interposition was 13.2%. The extrusion rate was significantly lower in the group with interposed cartilage (chi-square ⫽ 4.986; P ⫽ .03). Hearing Figures 2 and 3 illustrate the postoperative air-bone conduction difference 1 and 3 years after the operation, respectively. The reconstructed ears with cartilage interposition had hearing results equal to those without interposition in the ears using PORPs, whereas in the ears using TORPs, the hearing results for ears with cartilage interposition were slightly
Fig 2. The air-bone gap 1 year after surgery. Numbers within bars indicate the number of ears. PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis.
Fig 3. Air-bone gap 3 years after surgery. Numbers within bars indicate the number of ears. PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis. See Fig 2 for gap legend.
better. When tympanoplasty success was defined as an air-bone conduction gap of 20 dB or less, the overall success rate in the group with interposition was 75.0%, whereas that of the group without interposition was 75.5%. Table 2 summarizes the hearing outcome in each group. Two of the patients in the interposed group were excluded from this evaluation because of the lack of an audiologic examination. The table presents the mean airbone gap, the mean closure of the air-bone gap 3 years after surgery, and the overclosure/ damage 3 to 6 months after surgery. The closure of the air-bone gap is the gap before surgery minus the air-bone gap after surgery. The preoperative minus the postoperative bone conduction is the overclosure or operative damage to hearing. Therefore, if the value of overclosure/damage is in the positive range, the bone conduction threshold has improved, while it has deteriorated if the value is negative.3 With both types of prosthesis, there was no significant difference in the airbone gap or in the reduction of the air-bone gap between the group without interposition and the group with interposition (Student t test). In the ears using PORPs, the group with interposition was significantly improved in overclosure compared with the group without interposition (Student t test, t ⫽ 2.403, P ⫽ .008). When TORPs were used, the group without interposition showed -1.3 dB of overclosure, which indicated that bone conduction had deteriorated. There was a significant difference between the 2 groups (Student t test, t ⫽ 2.145; P ⫽ 0.03). This occurred pri-
HYDROXYAPATITE PROSTHESIS
225
TABLE 2. Hearing Ability 3 Years After Surgery
Prosthesis Type/Group PORP/ Without interposition (n ⫽ 32) With interposition (n ⫽ 22) TORP/ Without interposition (n ⫽ 21) With interposition (n ⫽ 30)
Air-Bone Gap (dB), Mean (SD)
Closure Air-Bone Gap (dB) Mean (SD)
Overclosure/Damage (dB)* Mean (SD)
8.1 (9.7) 4.8 (15.1)
16.6 (11.4) 16.5 (20.6)
5.8 (10.5) 14.4 (11.8)
17.2 (13.5) 12.1 (13.8)
7.7 (15.2) 9.9 (16.1)
⫺1.3 (17.0) 7.7 (7.9)
NOTE. Reduction in the air-bone gap is the difference between the preoperative and postoperative air-bone gaps. The difference between the preoperative and postoperative bone-conduction average is a measure of overclosure or operative damage to hearing. Abbreviations: PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis. *Results were obtained between 3 and 6 months after the operation. PORP and TORP comparisons are significantly different by the Student t test: PORP, P ⫽ .008; TORP, P ⫽ .03.
marily because the bone conduction threshold in 2 cases had increased 38 dB and 18 dB after the second stage of the operation. The reason for the deterioration was unknown; however, both these TORPs were extruded with a retraction of the eardrum and recurrence of cholesteatoma. DISCUSSION Many kinds of biocompatible materials have been used for ossicular reconstruction. In the mid 1970s, polytetrafluoroethylene vitreous carbon (Proplast, Vitek, Inc, Houston, TX) and high-density polyethylene sponge (Plasti-pore, Richards Medical Co, Memphis, TN) were used for ossicular reconstruction. In short-term studies of these prostheses, the extrusion rate varied from 2 to 9%. However, Smyth4 reported an 11% extrusion rate and unsatisfactory hearing results in a 5-year follow-up. Murakami et al5 reported a 23% extrusion rate and abandoned the use of Plastipore. In addition to these clinical results, foreign body reaction has been noted histologically with implanted Plasti-pore.6 At the end of the 1970s, ceramic implants for ossiculoplasty were introduced. One of the ceramics, HA, was first used as a prosthesis by Grote et al7 in 1981, and these investigators described good stability in the middle ear and good hearing outcomes. They insisted that the excellent biocompatibility made any interface between the prosthesis and the eardrum unnecessary. After this report, many otologists began to use HA prostheses because they were readily available and did not transmit danger-
ous diseases, such as HIV. However, extrusion was sometimes seen during long-term followup. Our previous study described a 16% extrusion rate for ossiculoplasties using HA prostheses at a 5-year follow-up.8 To reduce the extrusion rate, 2 operative procedures that prevent direct contact between the eardrum and the HA prosthesis have been employed. In one procedure the HA columella is positioned beneath the manubrium of the malleus.9,10 This method can only be used when the malleus handle is present. Sometimes this method cannot be used even if the malleus handle remains because of the design of the prosthesis. The other method, which we have employed since 1990, interposes autologous cartilage between the HA prosthesis head and the eardrum, as was carried out in the operation using Plasti-pore.11 In the present study, we compared ears reconstructed with HA prostheses, with and without cartilage interposition. In the group without interposition, extrusion occurred in 7 of 53 ears (13.2%), whereas it occurred in only 1 of 54 ears (1.9%) in the group with interposition. This result demonstrates that the interposition of cartilage is able to reduce the extrusion rate of HA prostheses. The result is similar to that of Zo¨llner12 with glass ceramic (Table 3). The only factor that was not assessed in both groups was eustachian tube function. Because successful surgery for chronic ear disease depends on normal tubal function, the extrusion rate may be affected by tubal function. Once the eardrum becomes retracted owing to tubal insufficiency, the ep-
226
KOBAYASHI ET AL
TABLE 3. Comparison of Extrusion Rate and Hearing Outcome of Ossiculoplasty With and Without Cartilage
Authors
Materials
No. of Ears
Follow-up Period
Extrusion Rate (%)
⬍15-20 dB (%)
Sanna et al11
Plasti-pore Plasti-pore ⫹ cartilage Glass ceramic (PORP) Glass ceramic (PORP) ⫹ cartilage Glass ceramic (TORP) Glass ceramic (TORP) ⫹ cartilage Hydroxyapatite (PORP) Hydroxyapatite (PORP) ⫹ cartilage Hydroxyapatite (TORP) Hydroxyapatite (TORP) ⫹ cartilage
65 54 27 29 28 24 32 22 21 32
⬎3 mo ⬎3 mo 24 mo 16 mo 31 mo 17 mo 3 yr 3 yr 3 yr 3 yr
15.4 1.9 22 3 21 0 3.1 0 28.6 3.1
53.8 51.9 81 93 55 83 84.4 81.8 61.9 70
Zo¨llner12
Present study
NOTE. Data of Zo¨llner evaluated only for ears in which the prostheses were not extruded. Abbreviations: PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis.
ithelium overlying the prosthesis is pulled toward the middle ear cavity. This action causes tissue ischemic and decubitus necrosis of the epithelium of the prosthesis head and results in the extrusion of the prosthesis. The relationship between tubal function and extrusion rate should be studied in more depth. Because HA does possess an excellent biocompatibility, the extrusion of HA implants cannot be caused by a foreign body reaction.12 Inflammation of the middle ear or dysfunction of the eustachian tube is believed to cause prosthesis extrusion. To prevent extrusion due to infection, we usually use a planned staged tympanoplasty. The HA prosthesis is implanted in the second stage operation after the inflammation has subsided. In ears with insufficient tubal function, such as in adhesive otitis media or cholesteatoma, it is difficult to correct eustachian tube function surgically. The placement of a ventilation tube in the eardrum during tympanoplasty is one method to correct insufficient tubal function.13 In the second operation, we obliterate the mastoid cavity with porous HA blocks in those ears with either a retraction pocket or a poorly aerated middle ear cavity.14 This procedure is based on the assumption that even an insufficient eustachian tube can aerate a smaller capacity middle ear. Our thinking is that this procedure is able to prevent eardrum retraction and thus reduce the extrusion rate. The effect of these procedures on preventing prosthesis extrusion should be further studied. There are few reports on prostheses and cartilage interposition (Table 3). Sanna et al11
reported a 15.4% extrusion rate in a group without cartilage interposition and a 1.9% rate in a group with homologous cartilage interposed between Plasti-pore and the eardrum. However, this was a short-term study, and the hearing outcome was unsatisfactory. Since histologic examination had revealed a giant cell reaction to Plasti-pore in the middle ear,6 this prosthesis is no longer used. Zo¨llner12 reported that interposition of a disk of autologous cartilage between the eardrum and glass ceramic reduced the extrusion rate and resulted in an improved audiometric outcome. He also examined the implanted cartilage histologically and found no foreign body reaction to the glass ceramic. However, Mangham and Lindeman15 reported 2 patients who had experienced progressive hearing loss attributable to the resorption of the glass ceramic implants. At present, this ceramic prosthesis is not used. Although Sanna11 reported no difference in the hearing outcome, Zo¨llner12 demonstrated better hearing results in ears with cartilage interposition. In this study, there was no significant difference in postoperative air-bone gap and closure of air-bone gap between the 2 groups. This means that the interposition of cartilage does not reduce the hearing gain resulting from the ossiculoplasty. In an experimental study, Nishihara and Goode16 studied in detail the effect of prosthesis mass on sound transmission in the middle ear. The cartilage used in the operation was 0.2 to 0.5 mm in thickness and weighed 30 to 50 mg. The type P and T HA prostheses used weighed 54 and 44 mg, respectively, with their original shaft lengths. Therefore, the to-
HYDROXYAPATITE PROSTHESIS
tal weight of the prostheses with cartilage ranged from 70 to 100 mg. In an experiment using cadaver temporal bone, the ideal weight of prostheses was less than 40 mg. Nishihara and Goode16 reported that adding a 40-mg mass brought about a deterioration in stapes displacement of between 0.9 and 4 kHz with a peak reduction of 22 dB at 1.1 kHz. This mass effect may cause a postoperative difference in the hearing success rate. In the present study, however, there was no significant clinical difference in the hearing results. CONCLUSION The interposition of cartilage between the HA prosthesis and the eardrum reduced the extrusion rate, and the interposed cartilage did not reduce the hearing gain achieved with the ossiculoplasty. The results confirmed that the procedure is an effective method for reducing the extrusion rate in ossiculoplasty using HA prostheses. REFERENCES 1. Yamanaka E, Yanagihara N, Nakajima T, et al: Hydroxyapatite ossicular prosthesis in the cat middle ear, in Babighian G, Veldman JE (eds): Transplant and Implant in Otology. Amsterdam, Kuglger & Ghedini, 1988, pp 305315 2. Blitterswijk CA, Grote JJ: Biocompatibility of clinically applied hydroxyapatite ceramic. Ann Otol Rhinol Laryngol Suppl 144:3-11, 1990 3. Committee on Hearing and Equilibrium: Committee on Hearing and Equilibrium guidelines for the evaluation
227
of results treatment of conductive hearing loss. Otolaryngol Head Neck Surg 113:186-187, 1995 4. Smyth GD: Five-year report of partial ossicular replacement prostheses and total ossicular replacement prostheses. Otolaryngol Head Neck Surg 90:343-346, 1982 5. Murakami Y, Hisamatsu K, Nozawa I, et al: Ossicular chain reconstruction with use of alloplastic prostheses; A comparative study in chronic middle ear disease (Japanese). Otologica Practica (Kyoto) Suppl 79:77-84, 1995 6. Belal A, Odnert S: TORPs and PORPs. A transmission and scanning electron microscopic study. J Laryngol Otol 96:49-55, 1982 7. Grote JJ, Kuypers W, Groot K: Use of sintered hydroxyapatite in the middle ear surgery. ORL J Otorhinolaryngol Relat Spec 43:248-254, 1981 8. Shinohara T, Gyo K, Saiki T, et al: Ossiculoplasty using hydroxyapatite prostheses: Long-term results. Clin Otolaryngol 25:287-292, 2000 9. Wehrs RE: Incus interposition and ossiculoplasty with hydoxyapatite prostheses. Otolaryngol Clin North Am 27:677-688, 1994 10. Dornhoffer JL: Hearing results with the Dornhoffer ossicular replacement prostheses. Laryngoscope 108:531536, 1998 11. Sanna M, Gamoletti R, Magnani M, et al: Enhancement biofunctionality of plastipore ossicular prostheses with the use of homologous cartilage. Am J Otol 4:138141, 1982 12. Zo¨llner C: Interposed cartilage as a precaution against extrusions of ceramic ossicular replacement implants. Ann Otol Rhinol Laryngol 96:207-209, 1997 13. O’Hare T, Goebel JA: Anterior subannular T-tube for long-term middle ear ventilation during tympanoplasty. Am J Otol 20:304-308, 1999 14. Yanagihara N, Gyo K, Sasaki Y, et al: Prevention of recurrence of cholesteatoma in intact canal wall tympanoplasty. Am J Otol 14:590-594, 1993 15. Mangham CA, Lindeman RC: Ceravital versus Plastipore in tympanoplasty: A randomized prospective trial. Ann Otol Rhinol Laryngol 99:112-116, 1990 16. Nishihara S, Goode RL: Experimental study of the acoustic properties of incus replacement prostheses in human temporal bone model. Am J Otol 15:485-494, 1994
Hydroxyapatite (HA) prostheses are widely used for ossicular reconstruction because of their excellent biocompatibility.1,2 Compared with ossicular prostheses of other materials, the extrusion rate of the HA prosthesis is considered to be low. Nevertheless, extrusion is seen during long-term follow-up. To prevent extrusion, we have interposed sliced cartilage between the prosthesis and the eardrum since 1990. Although this method is empirically assumed to be effective, this conclusion has not been confirmed by long-term follow-up study. The purpose of this study was to evaluate the effect on the extrusion rate and hearing outcome of interposing a cartilage graft between the HA prosthesis and the eardrum. From the Department of Otolaryngology, Ehime University School of Medicine, Ehime, Japan. This paper was presented at the 4th Extraordinary International Symposium on Recent Advances in Otitis Media, Sendai, Japan, April 16-20, 2001. Address correspondence to Taisuke Kobayashi, MD, Department of Otolaryngology, Ehime University School of Medicine, Shigenobu-cho, Onsen-gun, Ehime 7910295, Japan. E-mail: [email protected]. Copyright 2002, Elsevier Science (USA). All rights reserved. 0196-0709/02/2304-0001$35.00/0 doi:10.1053/ajot.2002.124191 222
MATERIALS AND METHODS Patients Between April, 1990, and March, 1997, ossicular reconstruction using HA prostheses with interposition of cartilage was carried out in 74 ears. Of these reconstructions, 54 ears were able to be followed-up for more than 3 years. The patients’ ages ranged from 8 to 68 years with a mean age of 42 years. The pathology in the group included middle ear cholesteatoma in 41 ears (76%) and chronic otitis media in 13 ears. The surgical results for this group were compared with the results for a second group that had undergone ossiculoplasty with HA prostheses but without interposition of cartilage between 1982 and 1989. Although the number of ears operated on was 79, 53 ears were followed up for more than 3 years. These patients were the subjects of the second group. Their ages ranged from 6 to 65 years with a mean age of 35 years. The pathology in the second group included middle ear cholesteatoma in 36 ears (68%) and chronic otitis media in 17 ears. This study compared the 2 groups after the same 3-year follow-up period.
Surgical Procedures Two types of Apaceram (Pentax Asahi Optical Co., Ltd., Tokyo, Japan) HA prostheses were used for the ossiculoplasties. The type P Apaceram (Fig 1a) is a partial ossicular replacement prosthesis (PORP), designed to be positioned between the
American Journal of Otolaryngology, Vol 23, No 4 (July-August), 2002: pp 222-227
HYDROXYAPATITE PROSTHESIS
223
Fig 1. (a) Type P hydroxyapatite prosthesis. (b) Type T hydroxyapatite prosthesis. (c) The length of the prosthesis shaft was adjusted by a diamond bar. (d) The sliced cartilage with perichondrium (arrow) was placed on the head of the hydroxyapatite prosthesis; PW, posterior wall of external auditory canal.
stapedial head and the eardrum; the type T Apaceram (Fig 1b) is a total ossicular replacement prosthesis (TORP), designed for interposition between the stapedial footplate and the eardrum. To get an appropriate tension between the stapes and the eardrum, the length of the prosthesis shaft was adjusted by an umbrella type diamond bar (Fig 1c). The interposed cartilage including the perichondrium was obtained from the concha of the patient’s ipsilateral auricle. Fibrin glue was usually used to attach the cartilage and HA prostheses (Fig 1d). Hearing reconstruction following mastoidectomy was carried out most often as a planned 2-stage operation. Eighty-five percent of the cases were operated on with a 2-stage tympanoplasty in the group without interposed cartilage, 83% in the group with interposition. Canal wall reconstruction was not carried out in patients who previously had been operated on with a canal wall down technique. Thus, 3 ears in the group without interposition and 8 ears in the group with interposition underwent canal wall down tympanoplasty. Two of the senior authors (K.G. and N.Y.) carried out the operations in both groups.
Postoperative Follow-up In postoperative follow-up, the ear was observed under a surgical microscope by the surgeons. In the audiologic evaluation, pure tone air and bone conduction thresholds were obtained before the first stage operation and 6 months, 1 year, and 3 years after the second stage operation. The average thresholds at 500, 1,000, and 2,000 Hz were used to calculate the air-bone gap to evaluate hearing outcome.
RESULTS Extrusion The otoscopic findings 3 years after surgery are presented in Table 1. In the group without interposition, good findings were seen in 37 ears (70%), whereas extrusion of the prosthesis occurred in 7 ears (13%) between 10 and 22 months after the operation. The extruded
224
KOBAYASHI ET AL
TABLE 1. Otoscopic Findings 3 Years after Surgery
Good Retracted eardrum Cholesteatoma recurrence or adhesion Extrusion of HA Total
HA, No. of Ears (%)
HA ⫹ Cartilage, No. of Ears (%)
37 (70) 6 (11)
45 (83) 6 (11)
3 (6) 7 (13) 53 (100)
2 (4) 1 (2) 54 (100)
Abbreviation: HA, hydroxyapatite prosthesis.
prostheses included 1 PORP and 6 TORPs. Extrusion occurred as a result of inflammation in 1 ear and of cholesteatoma recurrence or adhesion of the eardrum in 6 ears. In the interposed group, good findings were observed in 45 ears (83%) and an extrusion in 1 ear in which a TORP prosthesis was extruded 29 months after surgery due to inflammation. The extrusion rate in the group with interposition was 1.9%, whereas that of the group without interposition was 13.2%. The extrusion rate was significantly lower in the group with interposed cartilage (chi-square ⫽ 4.986; P ⫽ .03). Hearing Figures 2 and 3 illustrate the postoperative air-bone conduction difference 1 and 3 years after the operation, respectively. The reconstructed ears with cartilage interposition had hearing results equal to those without interposition in the ears using PORPs, whereas in the ears using TORPs, the hearing results for ears with cartilage interposition were slightly
Fig 2. The air-bone gap 1 year after surgery. Numbers within bars indicate the number of ears. PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis.
Fig 3. Air-bone gap 3 years after surgery. Numbers within bars indicate the number of ears. PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis. See Fig 2 for gap legend.
better. When tympanoplasty success was defined as an air-bone conduction gap of 20 dB or less, the overall success rate in the group with interposition was 75.0%, whereas that of the group without interposition was 75.5%. Table 2 summarizes the hearing outcome in each group. Two of the patients in the interposed group were excluded from this evaluation because of the lack of an audiologic examination. The table presents the mean airbone gap, the mean closure of the air-bone gap 3 years after surgery, and the overclosure/ damage 3 to 6 months after surgery. The closure of the air-bone gap is the gap before surgery minus the air-bone gap after surgery. The preoperative minus the postoperative bone conduction is the overclosure or operative damage to hearing. Therefore, if the value of overclosure/damage is in the positive range, the bone conduction threshold has improved, while it has deteriorated if the value is negative.3 With both types of prosthesis, there was no significant difference in the airbone gap or in the reduction of the air-bone gap between the group without interposition and the group with interposition (Student t test). In the ears using PORPs, the group with interposition was significantly improved in overclosure compared with the group without interposition (Student t test, t ⫽ 2.403, P ⫽ .008). When TORPs were used, the group without interposition showed -1.3 dB of overclosure, which indicated that bone conduction had deteriorated. There was a significant difference between the 2 groups (Student t test, t ⫽ 2.145; P ⫽ 0.03). This occurred pri-
HYDROXYAPATITE PROSTHESIS
225
TABLE 2. Hearing Ability 3 Years After Surgery
Prosthesis Type/Group PORP/ Without interposition (n ⫽ 32) With interposition (n ⫽ 22) TORP/ Without interposition (n ⫽ 21) With interposition (n ⫽ 30)
Air-Bone Gap (dB), Mean (SD)
Closure Air-Bone Gap (dB) Mean (SD)
Overclosure/Damage (dB)* Mean (SD)
8.1 (9.7) 4.8 (15.1)
16.6 (11.4) 16.5 (20.6)
5.8 (10.5) 14.4 (11.8)
17.2 (13.5) 12.1 (13.8)
7.7 (15.2) 9.9 (16.1)
⫺1.3 (17.0) 7.7 (7.9)
NOTE. Reduction in the air-bone gap is the difference between the preoperative and postoperative air-bone gaps. The difference between the preoperative and postoperative bone-conduction average is a measure of overclosure or operative damage to hearing. Abbreviations: PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis. *Results were obtained between 3 and 6 months after the operation. PORP and TORP comparisons are significantly different by the Student t test: PORP, P ⫽ .008; TORP, P ⫽ .03.
marily because the bone conduction threshold in 2 cases had increased 38 dB and 18 dB after the second stage of the operation. The reason for the deterioration was unknown; however, both these TORPs were extruded with a retraction of the eardrum and recurrence of cholesteatoma. DISCUSSION Many kinds of biocompatible materials have been used for ossicular reconstruction. In the mid 1970s, polytetrafluoroethylene vitreous carbon (Proplast, Vitek, Inc, Houston, TX) and high-density polyethylene sponge (Plasti-pore, Richards Medical Co, Memphis, TN) were used for ossicular reconstruction. In short-term studies of these prostheses, the extrusion rate varied from 2 to 9%. However, Smyth4 reported an 11% extrusion rate and unsatisfactory hearing results in a 5-year follow-up. Murakami et al5 reported a 23% extrusion rate and abandoned the use of Plastipore. In addition to these clinical results, foreign body reaction has been noted histologically with implanted Plasti-pore.6 At the end of the 1970s, ceramic implants for ossiculoplasty were introduced. One of the ceramics, HA, was first used as a prosthesis by Grote et al7 in 1981, and these investigators described good stability in the middle ear and good hearing outcomes. They insisted that the excellent biocompatibility made any interface between the prosthesis and the eardrum unnecessary. After this report, many otologists began to use HA prostheses because they were readily available and did not transmit danger-
ous diseases, such as HIV. However, extrusion was sometimes seen during long-term followup. Our previous study described a 16% extrusion rate for ossiculoplasties using HA prostheses at a 5-year follow-up.8 To reduce the extrusion rate, 2 operative procedures that prevent direct contact between the eardrum and the HA prosthesis have been employed. In one procedure the HA columella is positioned beneath the manubrium of the malleus.9,10 This method can only be used when the malleus handle is present. Sometimes this method cannot be used even if the malleus handle remains because of the design of the prosthesis. The other method, which we have employed since 1990, interposes autologous cartilage between the HA prosthesis head and the eardrum, as was carried out in the operation using Plasti-pore.11 In the present study, we compared ears reconstructed with HA prostheses, with and without cartilage interposition. In the group without interposition, extrusion occurred in 7 of 53 ears (13.2%), whereas it occurred in only 1 of 54 ears (1.9%) in the group with interposition. This result demonstrates that the interposition of cartilage is able to reduce the extrusion rate of HA prostheses. The result is similar to that of Zo¨llner12 with glass ceramic (Table 3). The only factor that was not assessed in both groups was eustachian tube function. Because successful surgery for chronic ear disease depends on normal tubal function, the extrusion rate may be affected by tubal function. Once the eardrum becomes retracted owing to tubal insufficiency, the ep-
226
KOBAYASHI ET AL
TABLE 3. Comparison of Extrusion Rate and Hearing Outcome of Ossiculoplasty With and Without Cartilage
Authors
Materials
No. of Ears
Follow-up Period
Extrusion Rate (%)
⬍15-20 dB (%)
Sanna et al11
Plasti-pore Plasti-pore ⫹ cartilage Glass ceramic (PORP) Glass ceramic (PORP) ⫹ cartilage Glass ceramic (TORP) Glass ceramic (TORP) ⫹ cartilage Hydroxyapatite (PORP) Hydroxyapatite (PORP) ⫹ cartilage Hydroxyapatite (TORP) Hydroxyapatite (TORP) ⫹ cartilage
65 54 27 29 28 24 32 22 21 32
⬎3 mo ⬎3 mo 24 mo 16 mo 31 mo 17 mo 3 yr 3 yr 3 yr 3 yr
15.4 1.9 22 3 21 0 3.1 0 28.6 3.1
53.8 51.9 81 93 55 83 84.4 81.8 61.9 70
Zo¨llner12
Present study
NOTE. Data of Zo¨llner evaluated only for ears in which the prostheses were not extruded. Abbreviations: PORP, partial ossicular replacement prosthesis; TORP, total ossicular replacement prosthesis.
ithelium overlying the prosthesis is pulled toward the middle ear cavity. This action causes tissue ischemic and decubitus necrosis of the epithelium of the prosthesis head and results in the extrusion of the prosthesis. The relationship between tubal function and extrusion rate should be studied in more depth. Because HA does possess an excellent biocompatibility, the extrusion of HA implants cannot be caused by a foreign body reaction.12 Inflammation of the middle ear or dysfunction of the eustachian tube is believed to cause prosthesis extrusion. To prevent extrusion due to infection, we usually use a planned staged tympanoplasty. The HA prosthesis is implanted in the second stage operation after the inflammation has subsided. In ears with insufficient tubal function, such as in adhesive otitis media or cholesteatoma, it is difficult to correct eustachian tube function surgically. The placement of a ventilation tube in the eardrum during tympanoplasty is one method to correct insufficient tubal function.13 In the second operation, we obliterate the mastoid cavity with porous HA blocks in those ears with either a retraction pocket or a poorly aerated middle ear cavity.14 This procedure is based on the assumption that even an insufficient eustachian tube can aerate a smaller capacity middle ear. Our thinking is that this procedure is able to prevent eardrum retraction and thus reduce the extrusion rate. The effect of these procedures on preventing prosthesis extrusion should be further studied. There are few reports on prostheses and cartilage interposition (Table 3). Sanna et al11
reported a 15.4% extrusion rate in a group without cartilage interposition and a 1.9% rate in a group with homologous cartilage interposed between Plasti-pore and the eardrum. However, this was a short-term study, and the hearing outcome was unsatisfactory. Since histologic examination had revealed a giant cell reaction to Plasti-pore in the middle ear,6 this prosthesis is no longer used. Zo¨llner12 reported that interposition of a disk of autologous cartilage between the eardrum and glass ceramic reduced the extrusion rate and resulted in an improved audiometric outcome. He also examined the implanted cartilage histologically and found no foreign body reaction to the glass ceramic. However, Mangham and Lindeman15 reported 2 patients who had experienced progressive hearing loss attributable to the resorption of the glass ceramic implants. At present, this ceramic prosthesis is not used. Although Sanna11 reported no difference in the hearing outcome, Zo¨llner12 demonstrated better hearing results in ears with cartilage interposition. In this study, there was no significant difference in postoperative air-bone gap and closure of air-bone gap between the 2 groups. This means that the interposition of cartilage does not reduce the hearing gain resulting from the ossiculoplasty. In an experimental study, Nishihara and Goode16 studied in detail the effect of prosthesis mass on sound transmission in the middle ear. The cartilage used in the operation was 0.2 to 0.5 mm in thickness and weighed 30 to 50 mg. The type P and T HA prostheses used weighed 54 and 44 mg, respectively, with their original shaft lengths. Therefore, the to-
HYDROXYAPATITE PROSTHESIS
tal weight of the prostheses with cartilage ranged from 70 to 100 mg. In an experiment using cadaver temporal bone, the ideal weight of prostheses was less than 40 mg. Nishihara and Goode16 reported that adding a 40-mg mass brought about a deterioration in stapes displacement of between 0.9 and 4 kHz with a peak reduction of 22 dB at 1.1 kHz. This mass effect may cause a postoperative difference in the hearing success rate. In the present study, however, there was no significant clinical difference in the hearing results. CONCLUSION The interposition of cartilage between the HA prosthesis and the eardrum reduced the extrusion rate, and the interposed cartilage did not reduce the hearing gain achieved with the ossiculoplasty. The results confirmed that the procedure is an effective method for reducing the extrusion rate in ossiculoplasty using HA prostheses. REFERENCES 1. Yamanaka E, Yanagihara N, Nakajima T, et al: Hydroxyapatite ossicular prosthesis in the cat middle ear, in Babighian G, Veldman JE (eds): Transplant and Implant in Otology. Amsterdam, Kuglger & Ghedini, 1988, pp 305315 2. Blitterswijk CA, Grote JJ: Biocompatibility of clinically applied hydroxyapatite ceramic. Ann Otol Rhinol Laryngol Suppl 144:3-11, 1990 3. Committee on Hearing and Equilibrium: Committee on Hearing and Equilibrium guidelines for the evaluation
227
of results treatment of conductive hearing loss. Otolaryngol Head Neck Surg 113:186-187, 1995 4. Smyth GD: Five-year report of partial ossicular replacement prostheses and total ossicular replacement prostheses. Otolaryngol Head Neck Surg 90:343-346, 1982 5. Murakami Y, Hisamatsu K, Nozawa I, et al: Ossicular chain reconstruction with use of alloplastic prostheses; A comparative study in chronic middle ear disease (Japanese). Otologica Practica (Kyoto) Suppl 79:77-84, 1995 6. Belal A, Odnert S: TORPs and PORPs. A transmission and scanning electron microscopic study. J Laryngol Otol 96:49-55, 1982 7. Grote JJ, Kuypers W, Groot K: Use of sintered hydroxyapatite in the middle ear surgery. ORL J Otorhinolaryngol Relat Spec 43:248-254, 1981 8. Shinohara T, Gyo K, Saiki T, et al: Ossiculoplasty using hydroxyapatite prostheses: Long-term results. Clin Otolaryngol 25:287-292, 2000 9. Wehrs RE: Incus interposition and ossiculoplasty with hydoxyapatite prostheses. Otolaryngol Clin North Am 27:677-688, 1994 10. Dornhoffer JL: Hearing results with the Dornhoffer ossicular replacement prostheses. Laryngoscope 108:531536, 1998 11. Sanna M, Gamoletti R, Magnani M, et al: Enhancement biofunctionality of plastipore ossicular prostheses with the use of homologous cartilage. Am J Otol 4:138141, 1982 12. Zo¨llner C: Interposed cartilage as a precaution against extrusions of ceramic ossicular replacement implants. Ann Otol Rhinol Laryngol 96:207-209, 1997 13. O’Hare T, Goebel JA: Anterior subannular T-tube for long-term middle ear ventilation during tympanoplasty. Am J Otol 20:304-308, 1999 14. Yanagihara N, Gyo K, Sasaki Y, et al: Prevention of recurrence of cholesteatoma in intact canal wall tympanoplasty. Am J Otol 14:590-594, 1993 15. Mangham CA, Lindeman RC: Ceravital versus Plastipore in tympanoplasty: A randomized prospective trial. Ann Otol Rhinol Laryngol 99:112-116, 1990 16. Nishihara S, Goode RL: Experimental study of the acoustic properties of incus replacement prostheses in human temporal bone model. Am J Otol 15:485-494, 1994