THE MIDDLE EAR PROSTHESIS

Abstract

The subject of the invention is a middle ear prosthesis (1), in particular of the middle ear conductive chain, comprising a first spring element (2) constituting a spring of at least one coil, having a length Lm in the range from 0.2 mm to 10 mm, and possibly a second spring element (3) constituting a spring of at least one coil, having a length L.sub.k in the range from 0.1 mm to 4 mm, wherein N the first spring element (2) and the second spring element (3) are made of wire of a material having a Young's modulus E in the range from 7.Math.10.sup.10 N/m.sup.2 to 11.4.Math.10.sup.10 N/m.sup.2, a density p in the range from 4.Math.10.sup.3 kg/m.sup.3 to 20.Math.10.sup.3 kg/m.sup.3, a Poisson's ratio v in the range from 0.34 to 0.44, wherein the first spring element (2) is connected to the second spring element (3) in such a way that the rotational symmetry axis of the first spring element (2) is placed at an angle α.sub.−1 with respect to the rotational symmetry axis of the second spring element (3), included in the range from 5° to 160°.

Claims

1. A middle ear prosthesis (1), in particular of the middle ear conductive chain, characterized in that it comprises a first spring element (2) constituting a spring of at least one coil, having a length Lm in the range from 0.2 mm to 10 mm, and possibly a second spring element (3) constituting a spring of at least one coil, having a length L.sub.k in the range from 0.1 mm to 4 mm, wherein the first spring element (2) and the second spring element (3) are made of wire of a material having a Young's modulus E in the range from 7.Math.10.sup.10 N/m.sup.2 to 11.4.Math.10.sup.10 N/m.sup.2, a density p in the range from 4.Math.10.sup.3 kg/m.sup.3 to 20.Math.10.sup.3 kg/m.sup.3, a Poisson's ratio v in the range from 0.34 to 0.44, wherein the first spring element (2) is connected to the second spring element (3) in such a way that the rotational symmetry axis of the first spring element (2) is placed at an angle α.sub.1 with respect to the rotational symmetry axis of the second spring element (3), included in the range from 5° to 160°.

2. The middle ear prosthesis (1) according to claim 1, characterized in that it comprises a third spring element (4) attached to the second spring element (3) at the end opposite to the first spring element (2), wherein the third spring element (4) is a spring of at least one coil, having a length Ls in the range from 0.1 mm to 1 mm, made of wire of a material having a Young's modulus E in the range 7.Math.10.sup.10 N/m.sup.2 to 11.4.Math.10.sup.10 N/m.sup.2, a density p in the range from 4.Math.10.sup.3 kg/m.sup.3 to 20.Math.10.sup.3 kg/m.sup.3, a Poisson's ratio v in the range from 0.34 to 0.44, wherein the third spring element (4) is connected to the second spring element (3) in such a way that the rotational symmetry axis of the third spring element (4) is placed at an angle α.sub.2 with respect to the rotational symmetry axis of the second spring element (3), included in the range from 5° to 160°.

3. The middle ear prosthesis (1) according to claim 1, characterized in that the spring elements (2, 3, 4) form a continuous structure.

4. The middle ear prosthesis (1) according to claim 1, characterized in that the spring elements (2, 3, 4) form a compression cylindrical spring, preferably with an outer diameter D.sub.z in the range from 1.0 mm to 1.6 mm.

5. The middle ear prosthesis (1) according to claim 1, characterized in that the spring elements (2, 3, 4) are made of wire of a circular cross section having a diameter d in the range from 0.1 mm to 0.3 mm.

6. The middle ear prosthesis (1) according to claim 1, characterized in that the spring elements (2, 3, 4) have a spring pitch P in the range from 0.1 mm to 1.0 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a front view of the middle ear prosthesis according to the first embodiment of the invention.

[0018] FIG. 2 is a partial cross-sectional front view of the first spring element of the solution from FIG. 1.

[0019] FIGS. 3A-3C show different variants of L-shaped middle ear prostheses in axonometric projection.

[0020] FIGS. 4A-4B show different variants of C-shaped middle ear prostheses in axonometric projection.

[0021] FIG. 5 is a photograph of an implanted middle ear prosthesis according to one embodiment of the present invention replacing a damaged anvil.

[0022] FIG. 6 is a photograph of an implanted middle ear prosthesis according to one embodiment of the present invention, stabilizing a disengaged incudostapedial joint.

[0023] FIG. 7 presents Tables 2 and 3.

EXAMPLES

Example 1

[0024] FIG. 1 is a schematic front view of the middle ear prosthesis 1 according to one possible embodiment of the present invention, while FIG. 2 is a partial cross-sectional front view of the first spring element 2 of the solution from FIG. 1. The middle ear prosthesis presented in FIG. 1 is a structure comprising three segments, made of one wire, constituting a continuous structure. The middle ear prosthesis 1 consists of the first spring element 2, which is a compression cylindrical spring having a length Lm in the range from 0.2 mm to 10 mm (depending on the needs). FIG. 2 indicates important structural parameters of the first spring element 2, also applicable to other spring elements 3, 4 of the discussed middle ear prosthesis 1. The second spring element 2, which is also a compression cylindrical spring having a length L.sub.k in the range from 0.1 mm to 4 mm is connected at one end of the first spring element 2. The first spring element 2 is connected to the second spring element 3 in such a way that the rotational symmetry axis of the first spring element 2 is oriented at an angle α.sub.1 with respect to the rotational symmetry axis of the second spring element 3, included in the range from 5° to 160°. Furthermore, the middle ear prosthesis presented in FIG. 1 comprises a third spring element 4 attached to the second spring element 3 at the end opposite to the first spring element 2. Similarly to the spring elements 2 and 3, the third spring element 4 is a compression cylindrical spring of at least one coil, having a length Ls in the range from 0.1 mm to 1 mm. Moreover, the third spring element 4 is connected to the second spring element 3 in such a way that the rotational symmetry axis of the third spring element 4 is placed at an angle α.sub.2 with respect to the rotational symmetry axis of the second spring element 3, included in the range from 5° to 160°.

[0025] The whole middle ear prosthesis, or the spring elements 2, 3, 4 are made of wire of a circular cross section having a diameter d in the range from 0.1 mm to 0.3 mm. Each of the spring elements 2, 3, 4 has an outer diameter D.sub.z in the range from 1.0 to 1.6 mm and a spring pitch P in the range from 0.1 mm to 1.0 mm. The wire used for the construction of the middle ear prosthesis is made of a material having a Young's modulus E in the range from 7.Math.10.sup.10 N/m.sup.2 to 11.4.Math.10.sup.10 N/m.sup.2, a density p in the range from 4.Math.10.sup.3 kg/m.sup.3 to 20.Math.10.sup.3 kg/m.sup.3, a Poisson's ratio v in the range from 0.34 to 0.44,

[0026] Individual embodiments of the presented middle ear prosthesis 1 will be shown in the following embodiments.

Example 2

[0027] According to the present invention, ten variants of middle ear prostheses, divided into two groups: L-shaped (variants I-VI) and C-shaped (variants VII-X) have been made. Design parameters of these variants are summarized in Table 1.

TABLE-US-00001 TABLE 1A Parameters of prostheses most often used in the implantation Variant Cross of the section d P α.sub.1 α.sub.2 L.sub.m L.sub.k L.sub.s prosthesis shape [mm] [mm] [°] [°] [mm] [mm] [mm] I “L” 1.35 0.4 90 0 0.4 0.8 — II “L” 1.35 0.4 90 0 0.4 1.6 — III “L” 1.5 0.5 90 0 0.5 1.0 — IV “L” 1.5 0.5 90 0 0.5 2.0 — V “L” 1.5 0.5 90 0 1.0 1.5 — VI “L” 1.35 0.4 90 0 0.8 1.2 — VII “C” 1.5 0.5 90 90 1.0 1.0 1.0 VIII “C” 1.5 0.5 90 90 0.5 1.0 1.5 IX “C” 1.35 0.4 90 90 0.8 0.8 0.8 X “C” 1.35 0.4 90 90 0.4 0.8 1.2

TABLE-US-00002 TABLE 1B Parameters of exemplary implanted prostheses under clinical conditions Variant Cross of the section d P α1 α2 Lm Lk Ls prosthesis shape [mm] [mm] [°] [°] [mm] [mm] [mm] A “L” 1.18 0.4 90 0 0.4 0.8 — B “L” 1.18 0.4 90 0 0.4 1.2 — C “L” 1.18 0.4 90 0 0.8 0.8 — D “L” 1.18 0.4 90 0 0.8 1.2 — E “L” 1.35 0.4 90 0 0.4 0.8 — F “L” 1.35 0.4 90 0 0.4 1.2 — G “L” 1.35 0.4 90 0 0.8 0.8 — H “L” 1.35 0.4 90 0 0.8 1.2 — I “C” 1.18 0.4 90 90 0.4 0.8 0.4 J “C” 1.18 0.4 90 90 0.8 1.2 0.8 K “C” 1.18 0.4 90 90 1.2 1.6 1.2 L “L” 1.18 0.4 0 0 1.2 0 — M “L” 1.18 0.4 0 0 1.6 0 — N “L” 1.18 0.4 0 0 2.0 0 — O “L” 1.35 0.4 0 0 1.2 0 — P “L” 1.35 0.4 0 0 1.6 0 — R “L” 1.35 0.4 0 0 2.0 0 — S “L” 1.5 0.5 0 0 0.8 0 — T “L” 1.5 0.5 0 0 1.2 0 — U “L” 1.6 0.5 0 0 0.8 0 — W “L” 1.6 0.5 0 0 1.2 0 —

[0028] Some of the variants of the middle ear prostheses 1 are shown in the axonometric projections in the figures: variant I— FIG. 3A, variant II— FIG. 3B, variant VI—FIG. 3C, variant VII—FIG. 4B and variant VIII— FIG. 4A, respectively.

[0029] For the variants of the middle ear prosthesis presented in Table 1, the transmission of the acoustic wave, which can be described as a function of the spectral transmittance, i.e. the ratio of the input signal (acoustic wave) to the output signal as a frequency function, was determined according to the formula:

[00001]$G\left(j.Math..Math.\omega \right)=\frac{Y\left(j.Math..Math.\omega \right)}{X\left(j.Math..Math.\omega \right)}$

[0030] For the safe and proper operation of the middle ear prosthesis 1, the function G(jω) value for any frequency in the range 20 Hz+20 kHz should be in the range of ±20 dB. This range corresponds to a 10-fold amplification or attenuation of the acoustic signal in a linear scale. Particular attention should be paid to high attenuation values (greater than −10 dB) for the frequency band from the range of audiometry tests, or 125 Hz+8 kHz. This fact is associated with good transmission of the acoustic wave in the range of speech signal occurrence. The stimulation in the study was a forcing sinusoidal variable pressure level of 80 dB (corresponding to an acoustic pressure equal to 0.2 Pa).

[0031] Table 2 presents the function G(jω) value for the following variant of material parameters: E=11.38.Math.10.sup.10 N/m.sup.2, v=0.34, ρ=4.43.Math.10.sup.3 kg/m.sup.3.

[0032] Table 3 presents the function G(jω) value for the following variant of material parameters: E=6.7.Math.10.sup.10 N/m.sup.2, v=0.33, ρ=2.7.Math.10.sup.3 kg/m.sup.3.

[0033] Analysis of the obtained results indicates that the amplitudes do not reach critical values in the low frequency range (20 Hz-400 Hz). Therefore, the middle ear prosthesis 1 in the presented variants propagates well vibro-acoustic energy, without posing a threat of dangerous resonance in low frequencies.

Example 3

[0034] The middle ear prosthesis 1 according to the present invention was examined in simulation tests on middle ear and auditory ossicles models. Simulations were performed on temporal bone models using an operating microscope, a surgical drive together with its equipment and adequate surgical instruments, so as to simulate the intraoperative conditions of the reconstruction of the middle ear transmission system the most precisely possible. In the trials, pathologies of individual auditory ossicles were simulated. The results showed the following indications for the application of the proposed prosthesis: PORP-type reconstruction, TORP-type reconstruction, incudostapedial anastomosis, anvil interposition, aid in solving various difficult and unusual situations (e.g. “empty cavity”).

[0035] FIG. 5 is a photograph of an implanted middle ear prosthesis 1 according to one embodiment of the present invention replacing a damaged anvil, whereas FIG. 6 is a photograph of an implanted middle ear prosthesis 1 according to one embodiment of the present invention, stabilizing a disengaged incudostapedial joint. In the example presented in FIG. 5 the middle ear prosthesis 1, and in fact the first spring element 2, was attached to the head of the stapes 5, while on the other side, the third spring element 4 was attached to the manubrium of the hammer 6. In this case, the middle ear prosthesis 1 served as an acoustic transducer ensuring the reconstruction of the middle ear conductive chain. On the other hand, in the example presented in FIG. 5 the middle ear prosthesis 1 was attached between the head of the stapes 5 and the long crus of the anvil 7. In this case, the usefulness of the middle ear prosthesis 1 according to the present invention as an annular stabilizer of the incudostapedial joint was demonstrated.

[0036] The methodology for the use of middle ear prosthesis 1 according to the present invention consisted in the appropriate selection of the correct length and shape, changing the obtained length by cutting with a surgical knife or scissors of a relevant fragment of the produced element and/or changing the form made by the operator using microsurgical needles bending the prosthesis 1 to obtain a required shape.

Example 4 Clinical Tests

[0037] The prostheses according to the invention have been used in the surgical treatment of middle ear disorders requiring a reconstruction of the ossicular chain.

[0038] The results of observations of patients qualified for the clinical trial “UNISPRING—a new system of modelled microprostheses of auditory ossicles reconstructing the middle ear conductive chain”.

[0039] In the group participating in the clinical trial, different variants of the prostheses according to the invention were implanted in 13 patients divided into two groups: 7 people and 6 people.

[0040] The second group of patients has not completed the full observation period yet, but the results are so far encouraging. The results presented below originate from the analysis of data collected during the observation of patients from the first group.

TABLE-US-00003 Manufacture Type of surgery Description Prosthesis method INCUDO- incudostapedial UNISPRING L: STAPEDOPEXIA anastomosis 1.18 short segment: 1-2 UNISPRING coils 1.35 long segment: 2-3 coils MALEO- maleotapedial UNISPRING C: STAPEDOPEXIA anastomosis 1.18 1. arm: 1-3 coils UNISPRING central arm: 2-4 1.35 coils 3. arm: 1-3 coils PORP partial ossicular UNISPRING straight segment of replacement 1.50 the length: 2-3 coils prosthesis UNISPRING 1.60 TORP total ossicular UNISPRING straight segment of replacement 1.18 the length: 3-5 coils prosthesis UNISPRING 1.35

[0041] The prosthesis according to the invention has proved to be a safe, effective, functional and ergonomic solution intended for the surgical treatment of the ossicular conductive chain.

[0042] The table below presents the scope of applications for which the prosthesis according to the invention was used, allowing for individual adjustment to the anatomical conditions of the patient and the type of pathology.

Designation of Prosthesis Type:

[0043]

TABLE-US-00004 Prosthesis designation Description UNISPRING A cylindrical spring with an outer diameter of 1.18 mm, 1.18 and length and shape adapted to anatomical conditions UNISPRING A cylindrical spring with an outer diameter of 1.35 mm, 1.35 and length and shape adapted to anatomical conditions UNISPRING A cylindrical spring with an outer diameter of 1.50 mm, 1.50 and length and shape adapted to anatomical conditions UNISPRING A cylindrical spring with an outer diameter of 1.60 mm, 1.60 and length and shape adapted to anatomical conditions

[0044] Detailed evaluation of the effectiveness of the so far collected material for the whole I group has been made based on the analysis of the results of the pure tone audiometry, speech audiometry and a subjective assessment and it is presented below:

A.:

[0045] Pure tone audiometry—mean values of pre-operative reserve and improvement (reduction in the post-operative reserve by the following values):

TABLE-US-00005 Average improvement by: The value of the auditory reserve [dB] frequency before the procedure 12 months after [Hz] [dB] the procedure 125 39 18 250 44 35 500 39 25 1000 27 20 2000 16 7 4000 15 15 8000 5 0

[0046] An improvement of the results within the described spectrum, including the so-called “closing reserve” phenomenon (value of the auditory reserve below 10 dB) for frequencies relevant to speech reception was obtained—for the following frequencies: 250 Hz, 500 Hz, 1 000 Hz, 2 000 Hz, 4 000 Hz.

B.:

[0047] Speech audiometry—mean values:

TABLE-US-00006 loudness level Understanding [%] [dB] Before the procedure 12 months after the procedure 10 0 0 20 0 0 30 0 0 40 0 0 50 0 2 60 7 2 70 40 72 80 69 87 90 85 87 100 87 87

[0048] A significant improvement in the threshold of understanding was achieved—a reduction in the loudness level by 20 dB (from 60 to 40 dB). The maximum capacity of using the auditory capabilities (90-100% of test understanding) in the loudness range of 60-80 dB was achieved in all operated patients. Before the procedure, a similar situation occurred in 1 patient (100% understanding at 60 dB).

C.:

[0049] Average value of subjective assessment:

TABLE-US-00007 Average value of subjective assessment [points] Before the procedure 12 months after the procedure 2.6 8.7

[0050] In all patients, an improvement of hearing assessed subjectively in the scale of 0-10 points was achieved.