Variants of "Surgical Angle" of approach
to the Antrum Method of "Slit-like" Antro-Atticotomy Method Repair of the Hinged Mechanism of the Stapes
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Repair of the hinged mechanism of the stapes(Repair of the hinged mechanism of the stapes. XYI World Congr. Of Otolar. Head Neck Surg.(Sydney, Australia, 2-7 March, 1997: 1077-1080.) |
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SUMMARYA new method of stapedioplasty is described aimed at restoration of the protective and accommodative properties of the middle ear due to recovery of the "hinged" mechanism at the posterior edge of the fenestra vestibuli. The method was named stapedioplasty with the "hinged" mechanism. An experience with application of this method in 200 patients with otosclerosis has proved its efficiency, as the protective and accommodative mechanism of the auris media is restored. Therefore, it was possible to use the method in treating children, whereas adult people could return to their profession after they were cured with this method. The method is recommended for a wide use, especially for rehabilitation of children.INTRODUCTIONAlthough the advent of hearing-improving microsurgery permitting a recovery of all the auditory ossicles has resulted in a similarly high success rate (over 90%, whichever the particular method was applied), the problem of disability of these patients after surgery remains open. Hyperacusis and vestibulopathy do not allow a tractor driver or a pilot to return to their previous work. Besides, these affections bring about a lot of unpleasant problems in everyday life. Therefore, there is hardly a surgeon who would assume responsibility for endowing a child with such troubles, although it is children who need this kind of surgery in the first place, as their hearing adaptation to the outward conditions is related to the efficiency of their development, which, in its turn, influences a success in their further life. Therefore, shortcomings of current hearing-improving surgical methods are obvious and well-known. The reason underlying these defects is also known. They are caused by the impaired protective and accommodative mechanism of the middle ear, providing for a perfect protection to the middle ear from the acoustic and vestibular overloads. However, after stapedioplasty or stapedectomy this mechanism is not regained, despite the opinion expressed by certain authors, who suggest that retention of the M.stapedius and its connection with the long process of the anvil (crus longum inci) is enough for such regaining.PATIENTS AND METHODTo solve the problem, we have decided to carry out a more detailed analysis of the protective and accommodative mechanism of the middle ear (Fig. 3). The basis stapedis (3) and the arcus stapedis (2) form a complex whose function is to transfer sound vibrations from the crus longum inci (5) through the fenestra vestibuli (A) into the vestibulum cochleae (B). In doing this, the whole complex (stapes) turns around the posterior edge of the basis stapedis (3) which is in a movable joint with the posterior edge of the fenestra vestibuli (A), forming a kind of a hinge (C), whereas the anterior edge of the basis stapedis (3) plunges and goes up from the vestibulum cochleae (B), conveying the sound vibrations to the labyrinthine fluid. As a result, when the M.stapedius (4) contracts, the anterior edge of the stapes emerges from the labyrinth, whereas when the M.tympanicus contracts, the crus longum inci (5) presses against the caput stapedis, so that the anterior edge of the stapes plunges into the vestibulum cochleae. Therefore, the protective mechanism of the middle ear consists in the following phenomenon: an acoustic overload causes both muscles of the middle ear (M.tensor tympani and M.stapedius) to contract in opposite directions, leading thereby to immobility of the stapes and preventing too loud sounds from entering through the stapes into the vestibulum cochleae. We have paid special attention to the following features in these movements of the stapes. The direction of traction of the M.stapedius (4 - Fig. 1) takes place under an angle of 90o to the direction of the transfer of the anterior edge of the basis stapedis (3). And it is not by accident, as the protective mechanism of the middle ear can function only thanks to this very interaction. If these features are not taken into due consideration in performing stapedioplasty (e.g., the so-called piston-like stapedioplasty - Fig. 2), even retention of the connection of the M.stapedius (4) and the caput stapedis (1) with the crus longum inci (5) does not recover the protective mechanism of the middle ear, as a contraction of M.stapedius causes only a shift of the caput stapedis and the prosthesis of the stapes (7) in the direction of the traction of the M.stapedius, rather than to the direction of traction under an angle of 90o which is needed. An analysis of the structural alterations between the elements of the described stapedioplasty and the stapes has led us to a conclusion that to recover the protective mechanism of the middle ear it is necessary to recover the "hinged" mechanism (C) at the posterior edge of the fenestra vestibuli (A), which would be similar to the natural one, i.e., around which the complex of the caput stapedis (1) and the prosthesis of the stapes (7) would shift. This could be achieved only through making the prosthesis of the crus posterius in the shape of a cross-bar (9) between the caput stapedis (1) and the posterior edge of the fenestra vestibuli (A), forming thereby a hinged mechanism (C) at the posterior edge of the fenestra vestibuli (Fig. 3). It is this relationship of the caput stapedis (1) and the sound-conducting prosthesis of the stapes (7) that provides for their turning around the hinge (C) as a unified bloc and starting to shift under an angle of 90o to the direction of the traction of the M.stapedius. In this way, the protective and accommodative mechanism of the middle ear is recovered. As the hinged mechanism is the main component in this method of stapedioplasty, the method has received a name of the hinged method of stapedioplasty (patent of the USSR No 1792649). The essence of the hinge-making method of stapedioplasty is as follows. After the arcus stapedis (2) is mobilized and shifted, the crus anterius stapedis (6) is cut off (Fig. 4). Then the sound-conducting prosthesis of the stapedis (7), e.g. in the shape of the piston-like stapedioplasty, is set in place, whereas the caput stapedis (1) is put where the crus anterius stapedis was, whereas the crus posterius (8) is placed on the posterior edge of the fenestra vestibuli (A). As a result, when the M.stapedius (4) contracts, the distal edge of the sound-conducting prosthesis of the stapedis (7) emerges from the vestibulum cochleae (B), whereas the place of the rest of the crus posterius stapedis in the posterior edge of the fenestra vestibuli begins to play the role of the hinge (C). If the length of the crus posterius stapedis (8) is insufficient, the latter is cut off and the prosthesis in the shape of the cross-bar is put in its place (Fig. 3 - 9). However, this method of stapedioplasty with a cross-bar (9) is connected with additional difficulties, as increased technical demands are placed on the otological surgeons performing this procedure and the operative time is longer. Therefore, we have developed a special complex prosthesis for the hinged-type stapedioplasty (Russian Federation's Patent No 016372), which permits a simultaneous recovery of the sound-conducting mechanism and the cross-bar mechanism (Fig. 5). In placing this stapes prosthesis, all the surgeon has to perform is to shift the caput stapedis behind two superior projections of the prosthesis (10), between which the tendon of the M.stapedius is put. An experience with application of this method in 200 patients with otosclerosis has proved its efficiency. After going through this procedure, patients were free from hyperacusis and vestibulopathy despite all kinds of strains. The age of the patients varied between 15 and 55 years. There were 133 women. The tractor driver and the pilot could return to their previous work. Stable results after a follow-up of over ten years have confirmed the efficiency of the method, which has allowed us to apply the method also in children. On the one hand, this has widened considerably the scope of our patients, whereas on the other hand, this has demanded an increase in otological surgeons whose number is apparently insufficient. |
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A - Fenestra vestibuli.
B - Vestibulum cochleae. C - The hinged mechanism formed at the posterior edge of the fenestra vestibuli. 1. Caput stapedis.
REFERENCESUljanov J. P.. The method of creation
of a ''hinge'' at the posterior edge of
Uliyanov Y.P. . Stapedoplasty and stapedectomy with ''hinge'' at the posterior edge of the fenestra ovalis. File from: ''Stapedoplasty and stapedectomy with teflon-piston''. The Master's thesis (Dissertation of the candidate) of medical sciences. Moscow,1967, 345 p. ( In Russian). Uliyanov Y.P. The method of ''hinge-like''
stapedoplasty. From:
Uliyanov Y.P. The Russian
PATENT ¹ 1792649, on the invention under the application ¹ 0910378
from 6 July 1964. Repair of the hinged mechanism of the stapes. The Bulletin
of the Inventions and Opening Russian. ¹ 5; 07.02.1993. ( In Russian).
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M.stapedius force
