The motion of conventional and novel total ossicular replacement prostheses during changes in static pressure

Long-Term Hearing Results of Endoskeletal Ossicular Reconstruction in Chronic Ears Using Titanium Prostheses Having a Helical Coil: Part 1-Kraus K-Helix Crown, Incus to Stapes

OBJECTIVES

1) To assess long-term hearing results after endoskeletal ossicular chain reconstruction (eOCR) using the titanium Kraus K-Helix Crown prosthesis, implanted incus to stapes, with glass-ionomer cement (GIC) in chronic ears and 2) to determine safety of the prosthesis and cement.

STUDY DESIGN

Prospective, nonrandomized, sequential, single center, single surgeon.

SETTING

Private practice, ambulatory surgical center.

PATIENTS

N = 15 males (42%) and 21 females (58%). Mean age was 40.4 years (range, 6-81 years); 38 ears (22 right ears [58%] and 16 left ears [42%]).

INTERVENTIONS

eOCR in chronic ears. Comprehensive preoperative and postoperative hearing measurements were performed for up to 9 years.

MAIN OUTCOME MEASURES

Postoperative hearing results at 1 year showed statistically significant improvement as compared with preoperative hearing. Long-term hearing results remained stable and showed no statistically significant change over 9 years.

RESULTS

Estimated mean pure-tone air conduction average improved by 14.5 dB (95% confidence interval = 10.3-18.7). Estimated mean speech reception thresholds improved by 15.5 dB (10.8-20.2). Word recognition scores improved by -2.2% (-5.3 to 1.0). The estimated mean postoperative air-bone gap was 10.5 dB (7.2-13.8). The estimated mean calculated air-bone gap was 11.3 dB (8.0-14.5). The estimated mean change in high-tone bone conduction (HTBC) average was +3.5 dB (0.9-6.0). Two prostheses extruded (5%). No patients experienced any unanticipated serious adverse effects or events.

CONCLUSION

eOCR using the K-Helix Crown prosthesis, incus to stapes, and GIC can significantly improve hearing at 1 year and maintain stable hearing over 9 years. Both prosthesis and cement are safe.

A new malleostapedotomy prosthesis. Experimental analysis by laser doppler vibrometer in fresh cadaver temporal bones

INTRODUCTION AND OBJECTIVES

One of the problems with total ossicular replacement prostheses is their stability. Prosthesis dislocations and extrusions are common in middle ear surgery. This is due to variations in endo-tympanic pressure as well as design defects. The design of this new prosthesis reduces this problem by being joined directly to the malleus handle. The aim of this study is to confirm adequate acoustic-mechanical behaviour in fresh cadaver middle ear of a new total ossicular replacement prosthesis, designed using the finite elements method.

METHODS

Using the doppler vibrometer laser, we analysed the acoustic-mechanical behaviour of a new total ossicular replacement prosthesis in the human middle ear using 10 temporal bones from fresh cadavers.

RESULTS

The transfer function of the ears in which we implanted the new prosthesis was superimposed over the non-manipulated ear. This suggests optimum acoustic-mechanical behaviour.

CONCLUSIONS

The titanium prosthesis analysed in this study demonstrated optimum acoustic-mechanical behaviour. Together with its ease of implantation and post-surgical stability, these factors make it a prosthesis to be kept in mind in ossicular reconstruction.

Flexibility within the middle ears of vertebrates

INTRODUCTION AND AIMS

Tympanic middle ears have evolved multiple times independently among vertebrates, and share common features. We review flexibility within tympanic middle ears and consider its physiological and clinical implications.

COMPARATIVE ANATOMY

The chain of conducting elements is flexible: even the 'single ossicle' ears of most non-mammalian tetrapods are functionally 'double ossicle' ears due to mobile articulations between the stapes and extrastapes; there may also be bending within individual elements.

SIMPLE MODELS

Simple models suggest that flexibility will generally reduce the transmission of sound energy through the middle ear, although in certain theoretical situations flexibility within or between conducting elements might improve transmission. The most obvious role of middle-ear flexibility is to protect the inner ear from high-amplitude displacements.

CLINICAL IMPLICATIONS

Inter-ossicular joint dysfunction is associated with a number of pathologies in humans. We examine attempts to improve prosthesis design by incorporating flexible components.

New total ossicular replacement prostheses with a resilient joint: experimental data from human temporal bones

HYPOTHESIS

New flexible total ossicular prostheses with an integrated microjoint can compensate for large static displacements in the reconstructed ossicular chain. When properly designed, they can mimic the function of the joints of the intact chain and ensure good vibration transfer in both straight and bent conditions.

BACKGROUND

Prosthesis dislocations and extrusions are frequently observed after middle ear surgery. They are mainly related to the altered distance between the coupling points because of large static eardrum displacements.

METHODS

The new prostheses consist of 2 titanium shafts, which are incorporated into a silicone body. The sound transfer function and stapes footplate displacement at static loads were evaluated in human temporal bones after ossicular reconstruction using prostheses with 2 different silicones with different hardness values. The stiffness and bending characteristics of the prostheses were investigated with a quasi-static load.

RESULTS

The sound transfer properties of the middle ears with the prostheses inserted under uncompressed conditions were comparable with those of ears with intact ossicular chains. The implant with the soft silicone had improved acoustic transfer characteristics over the implant with the hard silicone in a compressed state. In the quasi-static experiments, the minimum medial footplate displacement was found with the same implant. The bending characteristics depended on the silicone stiffness and correlated closely with the point and angle of the load incidence.

CONCLUSION

The titanium prostheses with a resilient joint that were investigated in this study had good sound transfer characteristics under optimal conditions as well as in a compressed state. As a result of joint bending, the implants compensate for the small changes in length of the ossicular chain that occur under varying middle ear pressure. The implants require a stable support at the stapes footplate to function properly.