OSSICULOPLASTY OF SMALL CRUS LONGUM DEFECTS WITH BONE CEMENT

Jacob Tauris, Chris L. Jacobsen, Kjell Tveterås, Michael Gaihede

Department of Otolaryngology, Head and Neck Surgery, Aarhus University Hospital, Aalborg, Denmark

Introduction

Ossicular erosion is frequently encountered in chronic otitis media (COM) with retraction pockets, atelectasis of the tympanic membrane and cholesteatoma.

The long process of the incus is most commonly affected.13 This condition results in irreversible conductive hearing loss, due to incudostapedial joint (ISJ) discontinuity, which can only be partially recovered by otosurgical reconstruction.4 In cases of isolated long process erosion, reconstruction of the ossicular chain can either be accomplished by bypassing techniques with ossicular replacement or bridging techniques with ossicular repair.1,2,57

Bypassing can be performed with interposition of an autograft or allograft, or by means of a partial os-sicular replacement prosthesis (PORP) with a broad range of available biomaterials to chose from, including plastics, ceramics and titanium. Bridging can be performed with different types of angular prosthesis (angular clip prosthesis, Applebaum prosthesis, Plester prosthesis), or as an alternative, by using bone cement such as glass ionomeric cement (GIC) and hydroxyapatite (HA) bone cement.1,2,6,8,9,10 In cases with smaller defects, bridging with bone cement seems an attractive approach compared to type-II reconstruction by interposition.

The aim of the present study was to describe the hearing results after ossiculoplasty with bone cement in cases with small defects of the long process of the incus.

Materials and methods

The surgical procedure performed in our study was an ossiculoplasty using SerenoCem cement.5,11 Cement application was performed as the last step of the tympanoplasty procedure to avoid disruption and mobilization of the new ossicular chain. Briefly, diseased or fibrous tissue around the ossicles was removed. Next, mucosa was stripped from the stapes head and the distal crus longum incudis to obtain a bloodless dry bony surface. Gel foam was then placed to avoid inadvertent spillage of cement. Bone cement was prepared and applied by a Rosen needle, with a working time of two to four minutes and a hardening time of five to seven minutes. The result was tested by application of pressure on the malleus. Finally, the tympanomeatal flap was brought back and the ear canal was packed.

The study is a retrospective study of 26 patients operated with SerenoCem cement ossiculoplasty. The inclusion criterion was an isolated smaller crus longum defect with an intact malleus and stapes. The exclusion criteria were tympanosclerosis, inducomallear joint laxity, incus luxation, concurrent otosclerosis, or a follow-up time shorter than one year. The outcome measures were hearing results represented by pre- and postoperative pure-tone-average (PTA) (500, 1000, 2000, and 4000 Hz) and Air-Bone-Gap (ABG) closure as well as post-operative complications.

Results

Twenty-six patients were identified in our database, in whom we performed ossiculoplasty with SerenoCem cement due to small defects of the crus longum. Two patients were excluded because of a follow-up time shorter than one year. Of the 24 patients included, 75% were adults, whereas 25% were children, giving a mean age of 39 years. The patient data included 18 cases of retraction pockets and eight cases of cholesteatoma. The mean follow-up time was 14 months and the mean follow-up rate was 92% (Fig. 1).

We registered the PTA pre- and post-operatively, as well as the improvement in ABG. The graphs shown in Fig. 2 represent the mean pre-operative air- and bone conduction thresholds compared to the mean postoperative thresholds. The pre-operative PTA was 36.8dB HL, whereas the post-operative PTA was 30.4dB HL. Our results showed a statistically significant improvement in mean PTA of 6.2dB HL (Fig. 3), as well as a statistically significant mean ABG closure of 11.1dB HL (Fig. 4), corresponding to a success rate of 77% (AAO-HNS Committee on Hearing and Equilibrium guidelines).

The only post-operative complication observed was an affected sense of taste in two patients (Fig. 5). In one of these patients, the chorda was lost during the operation. In the other patient, however, the chorda was described as intact by the end of the surgical procedure.

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Fig. 1. SereneCem cement ossiculoplasty study (overview).

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Fig. 2. Pre- and post-operative hearing levels.

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Fig. 3. Air conduction improvement.

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Fig. 4. Improvements in ABG.

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Fig. 5. Post-operative complications (n = 24)

Discussion

Erosion of the long process of the incus is the most commonly encountered ossicular chain defect in patients with COM.1,2 The prosthetic material chosen for reconstruction must be safe, biocompatible, easily handled and applied, capable of efficient sound transmission, and it should not be extruded or resorbed.2,9,12 Unfortunately, none of the biomaterials presently available meet all of these criteria.

Bypassing techniques with PORPs or incus interposition (type II) are widely used to reconstruct the ossicular chain, but all imply certain disadvantages, including a significant risk of dislocation, followed by deterioration of sound transmission.2,3,8 Additional risks include prosthesis extrusion, ossicular necrosis, ankylosis to bony surfaces, and implantation cholesteatoma.1,3,8,10

In contrast, bridging the ISJ with bone cement restores ossicular chain anatomy, leaving its inherent sound transmission efficacy intact, while eliminating the risk of prosthesis dislocation or extrusion.1,5,7,8 Furthermore, bone cement ossiculoplasty has the advantage of being a fast, safe and cost-effective procedure.2,6 Unfortunately, concerns still exist regarding bone cement breakdown or loosening of the re-sculptured incudo-stapedial joint over time.1,2,9 Moreover, studies have shown that certain bone cements including SerenoCem, exhibit pro-inflammatory properties13 and are potentially neurotoxic.2,6,14 There have been no reported cases of toxicity secondary to glass ionomeric cement ossiculoplasty.2,6 However, contact with the dura, perilymph and neural tissue (facial nerve, chorda tympani, Jacobson’s nerve) should be avoided during application.1,7,9 Postoperative adhesions between the middle-ear mucosa and the tympanic membrane (TM) as well as thickening of the TM have been described.6

Hydroxyapatite (HA) bone cements incite minimal inflammation and show better tissue tolerance than GIC’s as well as evidence of osseointegration with ossicular bone.1 Therefore, HA cements with short setting times, such as Otomimix, are preferred materials in the reconstruction of the ossicular chain.2,3,8

Almost all bridging techniques using angular prosthesis or bone cement preserve the physiological function of the ossicular chain including the malleoincudial joint, which may play a key role in ambient atmospheric pressure variations.15

Although bone cement techniques are faster and much more cost-effective, angular prostheses have the advantage of being easier to remove in case of revision surgery, since bone cement adheres firmly to the ossicles.15,16

In our study, we found acceptable short-term hearing results for ossiculoplasty with bone cement of smaller crus longum defects. The results are comparable to those obtained by conventional type II reconstructions by other authors.1,6,17 Limitations of the study include a relatively small sample size and a short follow-up period.

In conclusion, the present study indicates, that bone cement is a valuable and cost-effective alternative to ossiculoplasty with pre-formed prosthesis for reconstruction of the ossicular chain in patients with smaller crus longum defects. However, extended observation times are warranted to safely evaluate the stability of the re-sculptured incudostapedial joint and to ensure the long-term benefit from this approach.

References

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Address for correspondence: Jacob Tauris, tauris@dadlnet.dk

Cholesteatoma and Ear Surgery – An Update, pp. 261–265

Edited by Haruo Takahashi

2013 © Kugler Publications, Amsterdam, The Netherlands