WO1998009577A1

WO1998009577A1 - Apparatus for intraoral distraction osteotomy

Info

Publication number: WO1998009577A1
Application number: PCT/BE1997/000101
Authority: WO
Inventors: Maurice Yves Mommaerts
Original assignee: Maurice Yves Mommaerts
Priority date: 1996-09-04
Filing date: 1997-09-04
Publication date: 1998-03-12
Also published as: BE1010602A4

Abstract

A distraction apparatus for lengthening a lower jaw after cortical osteotomy, comprising: a distal anchoring screw (1), the screw section (2) of which is screwed into a bore in a rising branch of the lower jaw (ramus mandibularis) (3), and the free end of which has a polygonal head (4), preferably a hexagonal head, and a hinge bush (5); an expansion screw (6) which is hingedly connected to the above-mentioned anchoring screw (1) by means of a fastening screw (7), which also serves as a joint pivot which fits into the above-mentioned hinge bush (5); a screw stopper (8) which holds the joint member in a rigid position in an unchangeable direction, and a connecting piece (9) with internal screw thread (10) for the attachment of a fastening plate which is arranged, by means of screws (12), on one side of the chiselled-through mandibular arch.

Description

APPARATUS FOR INTRAORAL DISTRACTION OSTEOTOMY

The present invention relates to a distraction apparatus for lengthening a lower jaw after cortical osteotomy and adjustable attachment of at least two bone segments, with a view to dynamic osteosynthesis with reconstruction of the lower jaw bone by expanding the distances between the two mutually opposite bone segments by means of gradual stretching. It is used in maxillofacial surgery, in particular in orthognathic surgery in patients with mandibular retrognathia . This involves a facial shape in which the lower jaw, which is too short, lies behind the frontal plane of the forehead. The object of the invention is to remedy the occlusal closure of the teeth, to improve the breathing and to bring the face into proportion. It provides a better alternative for younger patients, who hitherto have been treated with functional orthodontic equipment without permanent skeletal results. Lengthening of the lower jaw is nowadays performed routinely, in general after the second growth spurt by means of a "sagittal split". However, lengthening of the lower jaw at a younger age is indicated for syndrome patients with pronounced hypoplasia of the lower aw.

DE-A-195,023 (Kreidler-Wangerin) describes an apparatus for distraction osteotomy with stretching of at least two bone segments. The distraction apparatus is introduced into the two corners of the aw after exposure of the bone and a sagittal split osteotomy. A bicortical screw fixation is arranged on the base of the mouth by transoral access. After boring through the mucous membranes, the distraction cylinder passes through the long vestibulum and ends in front of the inner corners of the mouth. The internal apparatus has to be arranged via incisions n the skin of the cheek. The apparatus lies parallel to the lower row of teeth, so that bilateral application can lead to a moment of force in the temporomandibular joint. The present invention a ms to rectify the abovementioned drawbacks and provides a distraction apparatus of the type described in the introductory part of the appenαed Claim 1, which can be activateα via the mouth.

This is achieved according to the invention by the apparatus comprising the following parts: a distal anchoring screw, the screw section of which is screwed nto a bore in a rising branch of the lower jaw (ramus mandibulans) , and the free end of which has a polygonal head, preferably a hexagonal head, and a hinge bush; an expansion screw which is hmgedly connected to the abovementioned anchoring screw by means of a fastening screw, which also serves as a joint pivot which fits into the abovementioned hinge bush; a screw stopper which holds the joint member in a rigid position in an unchangeable direction, and a connecting piece with internal screw thread for the attachment of a fastening plate which is arranged, by means of screws, on one side of the chiselled- through manαibular arch.

The distraction section comprises a telescopic screw. The telescopic screw allows the distraction section to be kept extremely compact, so that it remains inside the mouth even after complete extension following distraction. The limited length of the apparatus allows the lips to close, resulting in more comfort when eating and drinking. The system remains inconspicuous, which is an advantage in social terms. An adapted screw length for the distal anchoring screw and the small screws for fastening the lateral fastening plate make it possible to avoid the n. alveolaris inferior, and also the teeth roots, which is not true of external distracters with oicortical pins. Feeling in the lip and the chewing function remain guaranteed, so thai, there is no risk of bite injuries to the lip, the tongue or the cheek. One week after the intervention, the parents can begin to activate the distractor. The activation amounts to 1 mm each time, per day. The distractor is removed about two months later. Complete bone consolidation of the distraction location takes place on both sides.

According to a particular feature of the invention, the anchoring screw is provided at its free end with a polygonal head, preferably a hexagonal head, and a hinge bush and is introduced into a bore m a perpendicular piece of bone.

Advantageously, the expansion screw is a mechanical ackscrew, which comprises three parts which fit into one another, the central element having the largest diameter, in order to act as a connecting sleeve, and being provided at its ends with internal turns of opposite direction and different sizes, into which two mutually opposite telescopic arms fit, which are able to move into one another and have virtually the same length as the central connecting sleeve, so that they can move completely into and out of the central connecting sleeve.

A washer allows the anchoring to be positioned tightly against an edge of a bone without the latter being able to break off, as can happen when a conical head is screwed on.

There are no external incisions n the face. The risk of cosmetic damage is reduced to zero.

The intervention is less traumatic and can be carried out as a one-day case, without hospital admiss- ion for several days, since there is no need to apply force during the osteotomy.

When removing the wisdom tooth germ, the bone is easily weakened further both buccally and lingually by means of a cortical osteotomy. The incision for removal of the germ is lengthened rearwards in order to attach the anchoring elements . The vertical hinge point between the distal anchoring section and the lateral fastening plate allows a physiological repositioning of - . -

the mandibular cσndyle from the biomecnanical standpoint. A purely sagittal lengthening can also be selected, without being dependent on the horizontal corner between the rising branch ana the horizontal branch.

The apparatus is made from titanium. This material is well known for its optimum biocompatibi- lity, both for incorporation into the bone (osteo- mtegration) and for incorporation into the soft parts. No allergies to titanium have been described. Bimetals are ruled out.

The limited volume of the apparatus according to the invention by comparison with external activators allows the material costs to be reduced drastically. There is less risk of the apparatus or the bone fixation being damaged during sport, playing or sleeping than with external flxators .

These and other characteristics of the invention will emerge from the following description, in which reference is made to the appended drawings, which show an exemplary embodiment of an apparatus according to the invention, and in which:

Figure 1 shows a side view of a distraction apparatus according to the invention on a scale of 4:1; Figure 2 shows a side view, identical to that of Figure i, of the distraction apparatus in the extended position;

Figure 3 shows an exploded view of tne distraction apparatus depicted in Figures 1 and 2; Figure 4 shows a top view of the joint of the distraction apparatus depicted in Figures 1 to 3; Figures 5 and 6 show an exploded view and a side view of the connection fitting between the expansion screw and the fastening plate; Figure 7 shows a top view of a lower ja-v provided with some components of the distraction apparatus according to the invention; Figure 8 shows a top view of the lower aw depicted in Figure 6 equipped with the distraction apparatus; Figure 9 shows a side view, looking from the outside of the mouth mwarαs on the left-hand side of a lower aw, of a distraction apparatus in the contracted position prior to activation, and

Figure 10 shows a side view, which is identical to that of Figure 9, of the distraction apparatus in the extended position after activation. In these figures, identical numerals refer to identical or similar elements .

A distraction osteotomy is a surgical operation for correcting deformity or curvature of a bone which is curved or too short, the bone being split into at least two bone segments and the bone segments being joined together again by dynamic osteosynthesis, that is to say gradual repositioning and fixation of the bone segments with the aid of guided rods, small metal plates, screws, p ns, bone pegs or hoops. A washer allows the anchoring to be positioned tight against an edge of a bone, without the latter being able to break off, as can happen when a conical head is screwed on.

The distraction apparatus depicted in Figure 1 serves to lengthen the lower jaw, after a cortical bilateral osteotomy. It comprises the following parts: a distal anchoring screw 1, the screw section 2 of which is screwed into a bore in a rising branch of the lower jaw (ramus mandibularis) 3, and the free end of which has a polygonal head 4, preferably a hexagonal head, and a hinge bush 5; an expansion screw 6 which is hmgedly connected to the abovementioned anchoring screw 1 by means of a fastening screw 7, which also serves as a joint pivot which fits into the abovementioned hinge bush 5; - a screw stopper 8 which holds the joint member in a rigid position in an unchangeable direction, and a connecting piece 9 with internal screw thread 10 for the attachment of a fastening plate 11 which is arranged, by means of screws 12, on one side of the chiselled-through mandibular arch.

The neck of the screw section bears a washer and serves as a shoulder piece for the washer 13 to be pushed over, which washer has to effect outstanding connection to the rising branch of the lower jaw. The opening of the hinge bush 5 is located in a distal position, so that the male joint pivot which fits into it has a rotational freedom of virtually 20° about the vertical axis of a fastening screw 7, on both sides of the vertical axis (Figure 4).

The joint pivot is primarily intended to hold the extension direction of the expansion screws parallel to the longitudinal axis of the mouth, in contrast to distraction apparatuses which are already known and are unable to guarantee that the expansion guides are parallel (Figure 5).

The expansion screw 6 s a mechanical jack- screw, which comprises three parts which fit into one another. The central element has the largest diameter. It functions as a connecting sleeve 14 and is provided at its ends with internal turns of opposite direction and different sizes, in which two mutually opposite telescopic arms 15, 16 fit, which are able to move into one another and have virtually the same length as the connecting sleeve 14, so that they can move completely into and out of the central connecting sleeve 14.

The left-hand telescopic arm 16 has a hexagon which runs outwards and the sides of which are thus smaller at the end than at the start. The inclination of 1° is provided n order to fix the connecting piece 9 using the__ clamping screw 17 in such a manner that the necessary rigidity m the connection fitting between the expansion screw 6 and the connecting plate is maintained. On the inside, the narrowing hexagon has a screw thread in order to receive the clamping screw 17. The clamping screw 17 is provided with a polygonal socket head. The free end of the left-hand telescopic arm of the expansion screw 16 bears a spindle with an internal axial winding on which a connection fitting with a coaxial clamping screw 18 is clamped. The connecting piece 9 may have any desired form in order to implement an optimum connection between the expansion screw 6 and the fastening plate 11 which is fastened to the lower aw 3.

At the top, the connecting piece 9 has an internal hexagon, and also the same conicity as the spindle 19 of the left-hand telescopic arm 16. At the bottom of the connecting piece 9 is situated an internal elongate chamber which fits onto the protruding section of the lateral fastening plate 11.. As a result, the distraction forces and the chewing forces arise on the fastening plate 11 and not on the fastening screw 12 (Figure 8).

The connecting piece 9 has a lower elongate chamber, which is arranged on the top of the fastening plate 11 on the elongate raised portion by means of two screws. The five bores in the bottom of the fastening plate 11 serve to anchor this element on the lower jaw 3 (Figures 7 and 9). The fastening plate 11, which is fastened to the right-hand side of the jaw, is identical to the left-hand fastening plate, but as a mirror image of the latter.

Figure 10 shows the distraction apparatus in the extended position, on the left-hand side of a head, after activation. The activation is carried out via the mouth and can be performed by the parents of the child being treated.

Claims

1. Distraction apparatus for lengthening a lower aw after cortical osteotomy and adjustable attachment of at least two bone segments, with a view to dynamic osteosynthesis with reconstruction of the bone by expanding the distances between the two mutually opposite bone segments by means of gradual stretching, characterized in that it comprises the following parts: - a distal anchoring element (1), the screw section (2) of which is introduced into a bore in a rising branch of the lower jaw (ramus mandibulans ) (3), and the free end of which has a polygonal head and a hinge bush (5 ) ; - an expansion element (6) which is hingedly connected to the abovementioned anchoring element (1) by means of a fastening element (7), which also serves as a joint pivot which is suitably provided to fit in the abovementioned hinge element (5); a stopper element (8) which holds the joint member m a rigid position in a virtually unchangeable direction, and a connecting piece (9) with inner wall (10) provided for the attachment of a fastening plate (11) wnich is arranged, by means of further fastening elements (12), on one side of a mandibular arch.

2. Distraction apparatus according to Claim 1, characterized in that the said anchoring element (1) is formed by an anchoring screw, the said expansion element (6) is formed by an expansion screw, the said fastening elements (7 and 12) are formed by fastening screws, the said stopper element (8) is formed by a screw stopper and the said inner wall (10) is formed by an internal screw thread, with the said arch being chiselled through.

3. Distraction apparatus according to Claim 1 or

2 , characterized in that the anchoring element (1) is orovided at its free end with a polygonal head (4), preferably a hexagonal head, and a hinge bush (5) and is introduced into a bore in a perpendicular piece of bone . . Distraction apparatus according to one of Claims 1 to 3, characterized in that the expansion screw (6) is a mechanical ackscrew, which comprises three parts which fit into one another, the central element having the largest diameter, in order to act as a connecting sleeve (14), and being provided at its ends with internal turns of opposite direction and different sizes, into which two mutually opposite telescopic arms (15, 16) fit, which are able to move into one another and have virtually the same length as the central connecting sleeve (14), so that they can move completely into and out of the central connecting sleeve (1 ) .

5. Distraction apparatus according to one of the preceding claims, characterized in that a washer (13) is provided in order to position the anchoring tightly against an edge of a bone without the latter being able to break off, as can happen when a conical head is screwed on.

6. Distraction apparatus according to one of the preceding claims, characterized in that the connecting piece (9) is a screw cap (22), to which a fastening plate (11) is fastened.

7. Distraction apparatus according to one of the preceding claims, characterized in that the right-hand and left-hand parts are virtually symmetrical or identical in mirror image.

8. Distraction apparatus according to one of the preceding claims, characterized by the adjustable attachment of at least two bone segments obtained by sagittal bilateral split osteotomy, with a view to dynamic osteosynthesis with reconstruction of the lower aw bone by expanding the distances between the two mutually opposite bone segments by means of gradual stretching .