Results obtained with a new superelastic nitinol stapes prosthesis in stapes surgery

Abstract

Objective: The trimmable nitinol-polytetrafluoroethylene stapes prosthesis is a novel prosthesis that features a band-shaped nitinol loop. Unlike the SMart prosthesis, which uses the heat-activated self-crimping property of the alloy for fixation to the long process of the incus, this new prosthesis uses the property of superelasticity. The objective of the present study was to assess the hearing outcomes and intraoperative handling of the first 31 prostheses to be implanted in a primary stapes operation and to compare the results and experience thus obtained with those previously achieved with SMart prostheses.

Study design: Retrospective clinical study.

Setting: Tertiary reference center.

Patients: The results obtained in the first 31 patients (16 women and 15 men) in whom a nitinol prosthesis was implanted in a primary stapes operation between May 2009 and April 2010 were assessed and compared with those obtained in the first 31 patients (23 women and 8 men) to receive a SMart prosthesis between October 2004 and September 2005.

Intervention: Primary stapes surgery.

Main outcome measures: Audiometry was performed preoperatively, and after a mean follow-up period of 26.9 days (standard deviation [SD], ± 16 d) in the nitinol group and 26.2 days (SD, ± 22 d) in the SMart group. Audiometry was repeated in 18 patients in the nitinol group and in 21 patients in the SMart group after a mean period of 480 days (SD, ± 118 d) and 495 days (SD, ± 160 d), respectively.

Results: All the nitinol-polytetrafluoroethylene prostheses were implanted without problem. Fixation was simpler than with the SMart piston prosthesis. In the nitinol group, mean ABG3000 and ABG4000 were 9.5 dB (SD, ± 5.7 dB) and 10.7 dB (SD, ± 6.1 dB), respectively, with an improvement of 21.8 dB (SD, ± 8.0 dB) and 21.7 dB (SD, ± 7.9 dB), respectively. The corresponding values in the SMart piston group were 8.9 dB (± 4.3 dB) and 10.0 dB (± 5.2 dB), respectively, with an improvement of 21.2 ± 8.2 dB and 20.8 ± 8.3 dB, respectively. At the second follow-up, the values in the nitinol group were 4.4 dB (SD, ± 3.1 dB) for ABG3000 and 6.5 dB (SD, ± 4.3 dB) for ABG4000, with a mean improvement of 27.9 ± 6.0 dB and 27.0 ± 6.9 dB, respectively, whereas in the SMart group, the values were 5.7 ± 5.0 dB for ABG3000 and 6.4 ± 4.0 dB for ABG4000, with a mean improvement of 24.9 ± 7.2 and 24.7 ± 7.9 dB, respectively. These results did not differ to a statistically significant extent between the 2 groups.

Conclusion: The hearing outcomes obtained with the new superelastic nitinol prosthesis were similar to those that we had obtained previously with the SMart prosthesis. The fixation mechanism is simpler than with other types of prosthesis; however, the loop of the prosthesis seems not to be equally suitable for all diameters of the long process of the incus.