Discussion

In this report, an incus bridge between the relocated manubrium and footplate was used as an ossicular chain reconstruction method, and its functional outcomes were demonstrated. The ABG significantly decreased after surgery, and no tympanic membrane perforation or retraction was observed during follow up. Manubrio-incudo-stapedioplasty ossiculoplasty provided better hearing outcomes compared to autologous incus and TORP ossiculoplasties.

Autologous or allograft ossicles, biocompatible middle-ear prostheses, and bone cement are used to reconstruct the ossicular chain system. In patients with Austin–Kartush type B ossicular defects, the TORP, PORP and autologous incus are used to provide sound transmission. However, the extrusion rates of TORP or PORP were between 4 per cent and 9 per cent in previous studies.^{Reference House and Teufert9,Reference Emir, Kizilkaya Kaptan, Gocmen, Uzunkulaoglu, Tuzuner and Bayiz12,Reference Vassbotn, Moller and Silvola13} Displacement and/or extrusion of the TORP was the most common reason for hearing impairment over the long term.^{Reference Smyth14} Surgeons have addressed this issue by using cartilage grafts to prevent prosthesis extrusion. It was shown that a cartilage graft used with a TORP resulted in increased success rates over the long term.^{Reference House and Teufert9}

Different techniques have been shown to stabilise the TORP on the footplate for satisfactory hearing outcomes.^{Reference Beutner, Luers and Huttenbrink15–Reference Berenholz, Burkey and Lippy17} Vincent et al.^{Reference Vincent, Rovers, Mistry, Oates, Sperling and Grolman18} described a malleus relocation technique with Silastic banding to stabilise the TORP in the middle ear, and demonstrated better hearing outcomes with that technique compared to placement of the PORP on the stapes head. In addition, placement of the prosthesis between the malleus and footplate provided better hearing outcomes, compared to placement between the malleus and stapes head.^{Reference Murugasu, Puria and Roberson19}

A previous study showed a 56 per cent failure rate in autologous incus ossiculoplasty.^{Reference Zakzouk, Bonmardion, Bouchetemble, Lerosey and Marie11} The loss of incus–footplate contact, lateralisation of the incus, fall of the incus into the middle ear, and contact of the incus with the bony annulus were reported as reasons for failed autologous incus ossiculoplasty.^{Reference Zakzouk, Bonmardion, Bouchetemble, Lerosey and Marie11}

The manubrio-incudo-stapedioplasty appears to be a more stable ossiculoplasty technique than TORP or PORP placement on the footplate. Stabilisation between the incus and manubrium was strengthened with bone cement. Thus, using this technique, extrusion or displacement of the reconstruction material is less likely. When using an autologous incus, supporting this ossicle with the manubrium and bone cement provides a significant benefit, as compared to our results in the autologous incus group and those of previous reports. In addition, the incus will remain stable in the middle ear and the risk of hearing deterioration will decrease. In support of this hypothesis, we did not observe any hearing deterioration over a one-year follow-up period in patients who underwent manubrio-incudo-stapedioplasty.

Functional outcomes of different ossiculoplasty techniques for the reconstruction of Austin–Kartush type B ossicular defects have been presented in previous reports (Table 4).^{Reference Gerard, De Bie, Franceschi, Deggouj and Gersdorff7,Reference De Vos, Gersdorff and Gerard8,Reference Stankovic20–Reference Redaelli de Zinis22} Gerard et al.^{Reference Gerard, De Bie, Franceschi, Deggouj and Gersdorff7} mentioned in their study that the use of a titanium prosthesis with bone cement in Austin–Kartush type B cases provided an increase in hearing of 9.1 dB. In that study, ABG improved from 32.5 dB to 23.4 dB post-operatively, and an ABG of less than 20 dB was observed in 50 per cent of patients.^{Reference Gerard, De Bie, Franceschi, Deggouj and Gersdorff7} De Vos et al.^{Reference De Vos, Gersdorff and Gerard8} reported a post-operative ABG of 16.6 dB in cases of Austin–Kartush type B erosions reconstructed with a titanium prosthesis. In a study comprising 200 patients, the reconstruction of Austin–Kartush type B ossicular defects with autologous bone and cartilage resulted in a post-operative ABG of 10.9 dB.^{Reference Stankovic20} In a different study, the post-operative ABG was 11.9 dB in 46 patients.^{Reference Dornhoffer and Gardner21} Post-operatively, Zakzouk et al.^{Reference Zakzouk, Bonmardion, Bouchetemble, Lerosey and Marie11} reported an ABG of 24 dB in their TORP group and 30 dB in their incus group. Using manubrio-incudo-stapedioplasty, the present study found that hearing gain was 13.6 dB, post-operative ABG was 12.3 dB, and 100 per cent of cases had an ABG of less than 20 dB.

Table 4.

Reconstruction of Austin–Kartush type B damage in different studies

ABG = air–bone gap; TORP = titanium ossicular replacement prosthesis

The presence of the manubrium mallei is important to provide satisfactory hearing outcomes and prevent lateralisation of the tympanic membrane.^{Reference Vincent, Oates, Sperling and Annamalai23} Direct placement of the manubrium over the stapes head has also been proposed as an ideal reconstruction method for improving hearing outcomes.^{Reference Vlaming and Feenstra24} Using this reconstruction method, vibrations could be transmitted to the stapes footplate with minimal energy loss. Asai et al.^{Reference Asai, Roberson and Goode25} reported that removal of the malleus head and section of the tensor tympani muscle may improve hearing outcomes after placement of the prosthesis between the malleus and stapes footplate. Ashraf et al.^{Reference Ashraf, Ghonim, Eladl and Elsisi10} stated that malleus head removal and malleus relocation can be used to eradicate cholesteatoma and improve hearing. Sennaroglu et al.^{Reference Sennaroglu, Gungor, Atay and Ozer26} described manubrio-stapedioplasty as a reconstruction method in patients with incus–malleus fixation due to tympanosclerosis, and demonstrated satisfactory hearing outcomes using this technique. The disadvantages of manubrium relocation include the potential risk of medialisation of the tympanic membrane. As structures supporting the malleus are dissected, the manubrium can shift towards the middle ear. Nevertheless, the incus on the footplate acts as a lever to prevent medialisation of the manubrium.

Cost-effectiveness is an important consideration in hearing reconstruction when comparing different materials. The TORP is the most common material used in the reconstruction of Austin–Kartush type B ossicular defects. In the present study, we used bone cement to stabilise the manubrium–incus connection, which cost approximately $10 USD per case. In comparison, the cost of one TORP is approximately $150 USD.

One limitation of this report is the small number of patients, as Austin–Kartush type B ossicular defects are not common in our clinical practice. However, the power of the study was high, at greater than 0.8.