RU2452391C1 - Method of dynamic multi-spiral computed tomographic pre-operation determination of stirrup prosthesis length in surgical treatment of otosclerosis - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medicine, namely to radiodiagnostics and otolaryngology, and can be used for selection of stirrup prosthesis at pre-operation stage of otoslerosis treatment. Performed is multi-spiral computed tomography with three-dimensional dynamic scanning with section thickness 0.5 mm and interval 0.25 mm in axial projection. Simultaneously performed is impact with probing audio signal, exceeding perception threshold by 15-20 dB, and with test frequency 1000 Hz on middle ear structures with 1 second interval for 4-5 seconds. Multiplanar and three-dimensional reconstructions are built. At pre-operation stage length of stirrup prosthesis is determined by measuring the distance from lower surface of stirrup stapes to medial surface of long process of anvil bone in the phase of their maximal moving away from each other. After that intraoperationally prosthesis of selected length is installed.

EFFECT: method makes it possible to increase efficiency of surgical treatment of otoslerosis, and reduce operation time.

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Description

The invention relates to medicine, in particular to otorhinolaryngology and radiation diagnostics, and can be used to treat otosclerosis, namely, to select a prosthetic stapes prosthesis at the preoperative stage.

Otosclerosis is a disease that affects the bone capsule of the labyrinth. Progressive conductive hearing loss, characteristic of otosclerosis, develops as a result of the formation of an otosclerotic lesion in the oval window, which gradually reduces the mobility of the foot plate of the stapes and eventually immobilizes it (Plester D., Hildmann H., Steinbach E. Atlas der ohrchirirgie - Stuttgart: Kohlhammer, 1989 . - 174 s.).

The main treatment for otosclerosis is surgical. The essence of the treatment is to remove the affected stapes and replace it with an artificial prosthesis. Currently, prostheses made of titanium and teflon (Kosyakov S.Ya., Pakhilina E.V., Fedoseyev V.I. Stapedoplasty: one technology, two types of prosthesis are most widely used // Bulletin of Otorhinolaryngology - 2008. - №1 . - S.42-46.). The prosthesis is fixed on a long process of the anvil, and the distal part is installed in the opening of the vestibule window.

To achieve a good functional result, an important step is to determine the length of the prosthesis. An overly long prosthesis is able to directly contact a spherical or elliptical sac and lead to severe dizziness, unstable gait and, in rare cases, tinnitus. Too short a prosthesis can shift with scar tissue and cease to fulfill its function. The distance between the long process of the anvil and the base plate is from 3.9 to 5 mm. The prosthesis should ideally fill the gap between the long process of the anvil and the vestibule, its end should extend 0.2-0.3 mm beyond the lower edge of the base plate (Plester D., Hildmann H., Steinbach E. Atlas der ohrchirurgie - Stuttgart: Kohlhammer, 1989 - 174 s.).

Unfortunately, at present, it is only possible to determine the exact length of the prosthesis intraoperatively, which causes organizational and economic problems. This approach requires the presence of several prostheses of various lengths at once in the operating room, which is not always feasible in a number of domestic clinics.

Some authors calculate the length of the prosthesis according to the following scheme: 0.25 mm (thickness of the stirrup foot plate) and 0.5 mm (margin for the prosthesis in the vestibule) are added to the distance from the medial surface of the long process of the anvil to the foot plate of the stapes (Brackmann DE, Shelton S., Arriaga MA Otologic surgery. - Philadelphia: Saunders elsevier. - 2009. - 831 p.).

This scheme is too arbitrary and may lead to errors. An improper prosthesis that has been in an operating wound is no longer suitable for further use, which increases the cost of treating a patient. Therefore, the development of an accurate and reliable method of non-surgical calculation of the length of the prosthesis used is quite relevant.

To select a prosthesis at the preoperative stage, visualization of the structures of the middle ear is necessary.

Radiography according to Schuler and Mayer does not allow to determine the subtle changes in the auditory ossicles and, accordingly, their size. Classical computed tomography (Valvassori GE, Buckingham RA Radiology of the temporal bone. - Radiology of the ear, nose and throat. - Stuttgart: Thieme, 1992. - 9-33 p., Zonneveld FW Computed tomography is widely used to visualize the structures of the temporal bone. of the temporal bone and orbit. - Munich - Wiev - Baltimor: Urban and Schwarzenberg, 1987. - P.183). Usually, studies are carried out according to the program of bone reconstruction in a step-by-step mode with a slice thickness of 1 mm, this already indicates insufficient resolution. This diagnostic method allows you to obtain information about the condition of the ligamentous apparatus of the tympanic cavity, allows you to evaluate the density characteristics of the auditory ossicles. However, it is not possible to estimate the maximum distance between the foot plate of the stapes and the lenticular process of the anvil at the time of maximum “divergence” during movement.

The prototype of the present invention can be considered intraoperative measurement of the length of the prosthesis during traditional stapedoplasty. Moreover, after performing such stages of the operation as: infiltration of the external auditory canal with an anesthetic solution, endoural incision, opening of the tympanic cavity according to Rosen, separation of the anvil-stirrup joint, intersection of the tendon of the stirrup muscle, removal of the head and legs of the stapes, using a special probe, measure the distance between the medial surface of the long process of the anvil and the surface of the base plate of the stapes. Then 0.2 mm is added to the thickness of the base plate and 0.3 to contact with the inner ear fluid (perilymph) (Plester D., Hildmann H., Steinbach E. Atlas der ohrchirurgie - Stuttgart: Kohlhammer, 1989. - 174 s.) .

However, as indicated above, the described measurement method has a significant drawback: it is not possible to prepare a prosthetic stapes of the required length before surgery.

The objective of the invention is a method for the preoperative determination of the length of the prosthetic stapes.

This problem is solved by the method consisting in the fact that they carry out multispiral computed tomography with volume dynamic scanning with a slice thickness of 0.5 mm and an interval of 0.25 mm in axial projection, while simultaneously acting with a sounding sound signal exceeding the perception threshold by 15-20 dB and with a test frequency of 1000 Hz, on the structures of the middle ear with an interval of 1 second for 4-5 seconds, build multi-planar and three-dimensional reconstructions, preoperatively determine the length of the prosthetic stapes by measuring the distance from neither it grazing the surface of the plate to the medial surface of the stirrup long process of the incus in the phase of their maximum distance from each other.

In practice, the method of preoperative determination of the length of the prosthetic stapes is as follows:

1. The patient’s head is located in a standard head stand, fixed to prevent a change in position.

2. A system is inserted into the external auditory meatus that delivers sound vibrations of a given frequency and intensity to the auditory ossicles chain. For sound delivery, an impedance audiometer (Impedance Audiometer AT235h, Interacoustics, Denmark) with an integrated audiometry unit is used. Two air telephones are connected to the connector of the audiometer of the specified apparatus in a modification of the in-channel sound conduction with silicone tubes attached to them for conducting sound. The tubes, in turn, are connected to disposable earbuds that fit tightly into the ear canal of the test ear. For the purity of the test and the elimination of sound loss, the absolute tightness of the system is required. In cases of the patient having hypertrichosis, excess hair growing in the external auditory meatus must be removed in advance, because they can create an air gap between the earmold and the skin.

3. To mark the study area perform a tomogram. Tomography begins from the lower edge of the mastoid process and ends at the level of the upper edge of the mastoid process.

4. Tomography is carried out according to the protocol:

MSCT protocol of the temporal bone.

Tomography mode surround dynamic Cut thickness 0.5 mm Gantry Tilt 0 Field of study about 4 cm Voltage 80 kV Amperage 300 mA Type of reconstruction Bone

1. After performing tomograms, the first series of sections is carried out in axial projection. Scanning progression from the temporal bone to the cranial vault. At the same time, in the manual mode of audiometry for 4-5 seconds, a probing sound signal is intermittently supplied to the test ear with a test frequency of 1000 Hz and an intensity exceeding the perception threshold by 15-20 dB (i.e., sound is transmitted for the first second, to the second second - not served, etc.). The sound intensity is selected on the basis of a previously made audiogram or on the basis of a test audiogram conducted immediately before MSCT examination.

5. Then, the investigated temporal bone is reconstructed with a 0.5 mm enlargement and reconstruction.

6. After obtaining sections in the axial projection, multiplanar reconstruction (MPR) in the coronary projection is performed.

7. The preoperative length of the stapes prosthesis is determined by measuring the distance from the lower (medial) surface of the foot plate of the stapes to the medial surface of the long process of the anvil at the time of their maximum distance from each other.

8. Intraoperatively install the prosthesis of the selected length.

9. Pre-intraoperatively determine the acuity of hearing.

10. Perform tonal threshold audiometry to confirm a positive functional result.

22 patients with suspected otosclerosis were examined on a Toshiba 320-spiral computer tomograph Aquilion ONE of the proposed method.

EXAMPLE 1. Patient P., 37 l. Directing diagnosis of otosclerosis. The patient underwent dynamic multispiral computed tomography of the right temporal bone. The study was performed on a Toshiba 320-spiral Aquilion ONE computed tomograph with volume dynamic scanning with a slice thickness of 0.5 mm. The patient's head was located in a standard head stand, fixed to prevent a change in position. A one-time earmold is inserted into the external auditory canal, connected to an air telephone (in the modification of in-channel sound conduction), which in turn is connected to the audiometry connector of an impedance audiometer (Impedance Audiometer AT235h, Interacoustics, Denmark). There is no sound yet. To mark the study area, a topogram was performed. Tomography was performed from the lower edge of the mastoid process and finished at the level of the upper edge of the mastoid process, the field of study was about 4 cm, the voltage was 80 kV, the current strength was 300 mA, the type of reconstruction was bone. After completing the topogram, the first series of sections in axial projection was performed. Scanning progression from the temporal bone to the cranial vault. At the same time, for 4-5 seconds, they were exposed to a sounding sound signal of 65 dB (45 dB + 20 dB) and with a test frequency of 1000 Hz, using an impedance audiometer on the structures of the middle ear with an interval of 1 second (i.e., for the first second, sound is heard , for the second second - not served, etc.). Then, a reconstruction of the right temporal bone was performed with an increase and reconstruction of a 0.5 mm section. After obtaining sections in the axial projection, a multiplanar reconstruction (MPR) was performed in the coronary projection. On tomograms received pneumatic drum cavity. The chain of auditory ossicles is traced throughout. The base of the stirrup is compacted, with a functional test, there is a restriction in the mobility of the base of the stirrup. The distance between the lower (medial) surface of the foot plate of the stapes and the medial surface of the long process of the anvil at the time of their maximum distance from each other is 4.2–4.3 mm. In the bone capsule of the labyrinth, the focus of spongiosis is determined anterior to the vestibule window with a size of 1.8 × 0.9 mm. The remaining structures of the inner ear without visible pathological changes. The internal auditory meatus is not dilated. Based on the dynamic MSCT data, otosclerosis was diagnosed, and the estimated preoperative length of the prosthesis was 4.2–4.3 mm. Subsequently, the patient underwent stapedoplasty on the right, a pre-selected 4.25 mm K-Piston prosthesis was installed (it was selected from prostheses 4 mm, 4.25 mm and 4.5 mm long according to the “pitch” of the prosthesis length), a good functional result was obtained ( the gap was reduced by 20 dB), which confirmed the accuracy of the dynamic MSCT data.

EXAMPLE 2. Patient S., 35 l. Directing diagnosis of otosclerosis. The patient underwent a similar dynamic multispiral computed tomography of the right temporal bone. On the tomograms received: temporal bone of a pneumatic structure. The cells of the mastoid process are aerial. The drum cavity is pneumatized. The chain of auditory ossicles is traced throughout. The base of the stapes is compacted, thickened to 0.9 mm, with a functional test it practically does not shift. The distance between the lower (medial) surface of the foot plate of the stapes and the medial surface of the long process of the anvil at the time of their maximum distance from each other is 4.2 mm. In the bone capsule of the labyrinth, the focus of spongiosis is determined anterior to the vestibular window 2 × 2 × 3.5 mm in size. The remaining structures of the inner ear without visible pathological changes. The internal auditory meatus is not dilated. Based on dynamic MSCT data, otosclerosis was diagnosed, and the estimated preoperative length of the prosthesis was 4.2 mm. The prosthesis was prepared in advance, and the patient underwent stapedoplasty on the right, a 4.25 mm K-Piston prosthesis was installed (it was selected from prostheses 4 mm, 4.25 mm and 4.5 mm long according to the “pitch” of the prosthesis length), a good one was obtained functional result (the gap decreased by 15 dB), which confirmed the accuracy of the dynamic MSCT data.

The developed method has the following advantages:

1. Allows you to accurately determine the thickness of the foot plate of the stapes, the distance between the lower surface of the foot plate of the stapes and the medial surface of the long process of the anvil, which allows us to calculate the optimal length of the stapes prosthesis for this patient even at the preoperative stage.

2. Allows you to pre-prepare the necessary prosthesis for the operation, which is economically beneficial and significantly facilitates the organization of the treatment process.

3. Significantly reduces the time of surgery stapedoplasty.

4. Due to the accurate determination of the required length of the prosthesis allows you to get the best functional result of the intervention.

Thus, the developed method for the preoperative determination of the prosthesis length using dynamic multispiral computed tomography makes it possible to increase the effectiveness of surgical treatment of otosclerosis and reduce the time and cost of surgery.

Claims (1)

The method of dynamic multispiral computed tomography preoperative determination of the length of the stapes prosthesis in the surgical treatment of otosclerosis, which consists in conducting multispiral computed tomography with volumetric dynamic scanning with a slice thickness of 0.5 mm and an interval of 0.25 mm in axial projection, while simultaneously acting with sounding sound with a signal exceeding the perception threshold by 15-20 dB and with a test frequency of 1000 Hz, a multiplan is built on the middle ear structures with an interval of 1 s for 4-5 s nye and three-dimensional reconstruction, determine the length of the stapes prosthesis by measuring the distance from the bottom surface underfoot plate to the medial surface of the stirrup long arm of the anvil in a phase of their maximum distance from each other.