WO2009003256A2

WO2009003256A2 - Introduced improvements in surgical procedure and in the bone distractor device

Info

Publication number: WO2009003256A2
Application number: PCT/BR2008/000122
Authority: WO
Inventors: Ariel Lenharo; Túlio VALCANAIA
Original assignee: Sin Sistema De Implante Nacional Ltda
Priority date: 2007-07-05
Filing date: 2008-04-24
Publication date: 2009-01-08
Also published as: WO2009003256A3; BRPI0705103A

Abstract

Introduced improvements in surgical procedure and in the bone distractor device, intends to produce a group of parts denominated distractor device kit, composed of two biologically compatible titanium anchors (1 ) six screws of varying lengths (7), two contention rings (8), one activation key (9) and two systems of transference, where the biologically compatible anchors are installed in the bone of the alveolar ridge in such manner as to allow the tractioning of a block of bone upward in a vertical direction in patients who are previously selected and informed about the procedure.

Description

"INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE"

This in reference to a patent request for the invention of "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE" which was developed to produce a device named distractor device kit, which consists of two biologically compatible titanium anchors, six screws of varied lengths, two contention rings, an activation key and two systems of transference, where the biologically compatible titanium anchors are implanted in the edge of alveolar bone in such a way as to enable the tractioning of a section of bone vertically within previously selected and informed patients.

Study of the Method

So that the bone can be lengthened, the compact circumferencial bone should be sectioned first, taking care to maintain the medular cortex and the periostomy, a process which is called corticotomy. The two sections of bone are gradually and evenly separated from one another, which induces the proliferation of bone between them and increases the length of the bone. The traditional device utilized to obtain this result is a pin

(passing through the soft tissue) on either side of the corticotomy, with a screw between them, maintaining the pins and the bone in a rigid state. The screw is turned to allow the separation (distraction) of the extremities of the bone. When the distractor is in place, it should remain in this position for approximately five days. After this time, the corticotomy is distracted through the turning of the screw. This action can be performed by the patient after orientation from their physician or by the physician. The scale of distraction is crucial; not enough velocity may allow the joining of the bone while the incorrect adjustment may cause fibrosis. It is widely believed that lmm por day in adults is enough, and for younger patients, 2mm are possible. This movement should be gradual and incremental over a period of 24 hours, to guarantee the best quality bone.

When the bone is extended to the correct length, the device remains in place in a stable condition to allow the healing of the bone. In the craniofacial complex, this period of scarring usually lasts around 6 to 8 weeks.

As the bone separates, the central area being separated becomes a region of great cellular activity and blood flow. In the regenerated portion there are fibroblasts which produce collagen, which act as support for the development of osteoids. The osteoids place themselves in parallel columns along the direction of the distraction, between the extremities of the bone and the regenerated central portion. The bone which is produced is less dense and has less volume when compared to the original bone, but it is widely believed that the potential for growth is the same. As the bone is elongated, the conjunctive tissue is stretched.

The stretching of the nerve fiber results in the increase of the internodal distance; however, whether or not this affects the propagation of the sensitivity of the nerves is still under debate. The muscles are stretched, although these have the capability of regeneration. In the mean time, the stretched conjunctive tissue remains under considerable tension, which causes reports of fracturing of the pins belonging to the distractor device. Distractor devices can be classified according to the type of distraction: monofocal, bifocal or trifocal. These devices consist of bicortical pins which are inserted on each side of of the segments of corticotomy and to the "bone transport discs" when these are used; they are connected to the distraction rod by means of fixation clamps. When the device is activated, the rod pushes the clamps, separating the bone segments of the osteotomy.

The devices can be further classified as intramouth or extramouth. The extramouth systems are made of flexible external pins and arches which permit its adaptation to new sizes as the device is activated. On the other hand, the innermouth systems have a rigid fixation method which is obtained through plaques and screws.

The extramouth devices can be uni, bi or multidirectional. The distraction devices classified as unidirectional are able to correct in only one direction, horizontal or vertical. The devices with bidirectional distraction allow by means of corticotomies on a dual level, performing corrections in backward or forward movements and vertical ones at the same time. These kind of devices allow the correction of deformities which involve angle, rami and body of the mandible. The later modifications of the bidirectional devices allow angular adjustments through the manipulation of the bone segments. Unlike the extramouth devices, innermouth devices are inserted within the oral cavity and therefore are less bulky. These may be fixated in bone (osseous support), in teeth (dental support) or in both (hybrid support). The extramouth distraction devices offer simplicity of fixation, easy manipulation, and bi and multidirectional distraction but have the drawbacks of their size, ugly scarring and psycho-social difficulties for the patient. However, innermouth devices, although they have the advantages of the absence of scarring and are much smaller, they are very difficult to manipulate due to restricted access via the oral cavity.

Some authors suggest that the choice of which device, the locale and the direction of the corticotomy, the locations for insertion of the pins and the amount of distraction should be made only after obtaining the following:

- articulative models,

- panoramic radiographs and teleradiographs, - extramouth and innermouth photographs,

- a stereolithograph model Craniofacial Osteogenic Distraction

As with any new surgical technique, many scenarios have been proposed in order to guarantee that osteogenic distraction is considered beneficial.

Theoretically, it is possible to elongate facial bones on any spacial plane; vertically, horizontally or laterally. Orthodontists are regularly involved in procedures which affect the growth of the craniofacial complex, which justifies increasing interest in osteogenic distraction. With the craniofacial region, it is virtually impossible to create a true corticotomy, due to the fact that the periosteum is inevitably damaged during the surgical process.

However, the abundant supply of blood in this region clearly justifies the necessity for a corticotomy; therefore a more adequate name would be osteotomy.

Tissue Reaction:

The process of regeneration between the two segments of the osteotomy for craniofacial bones was explained by the authors Karp et al. 9 in the year 1992. These authors divided the process into four stages: central zone, stretched tissue zone, remodeling zone and the mature bone zone. The central zone is the area which will be subjected to surgery; which, while under traction by means of the distractor, stimulates the fibroplasts in the repositioning of collagen type I in the stretched tissue zone. The osteoprogenitor cells dislocate from the extermities to the center, producing bone tissue with plates which are positioned in the same direction as the vector of the distraction. The last stage is the maturation of the bone tissue which has been deposited in the lengthened area. According to this study, as well as that by Califano et. Al. 14 in 1994, the process of bone formation occurs predominantly through intramembranous ossification. Radio graphically, the first stage is represented by a lucid area. Thereafter, this zone begins to be filled by thin bone spicula which correspond to the bone trabecula seen in histological examinations, which, at the end of the distraction period, are characterized by a much more mature and consolidated bone structure. Bell et al. 15 , in 1997, noted the need for alveolar bone contigious to the adjacent teeth to induce the formation of the new bone through osteogenic distraction in order to increase the transversal dimensions of the mandibula.

Osteogenic distraction can be divided into four clinical stages: - osteotomy (This is where osteoclast occurs; maximum preservation of the blood supply to the periosteum and endosteum to assure blood supply to the initial bone callus which will play an important osteogenic role in the distraction process); - latency period (The formation of the fracture callus; regeneration of the soft tissue, periosteums, blood vessels and the proliferation of osteogenic cells);

- distraction; (mechanical induction of the formation of the new bone through the gradual separation of the segments of the osteotomy; this traction should provide adequate stimulus so that the periosteum cells are able to transform into cells which have osteogenic potential) and

- consolidation (the device is kept in a fixed position so that the consolidation of the segments between the extremities of the osteotomy can occur).

However, for all these stages to occur, it is necessary to observe a few some biological principals:

- a corticotomy with maximum preservation of the periosteum and endosteum,

- a latency period varying between 5 and 15 days, as to allow the development of a fine fracture callus,

- a rate varying between 0.5 to 1.5mm ,

- stability of the osteotomy fragments. While planning an osteogenic distraction, one should keep in mind the principles which guide the tissue alterations that occur during mechanical traction, making it necessary to be aware of biomechanical principles, which according to Samchukov et. Al. 16 (1999), can be divided into the following: • extrinsic,

• intrinsic and

• those relating to the vector of the distraction. The extrinsical parameters are those related to the stability of the fixation device. This parameter is crucial since it is this which will determine the standard of bone neoformation. Literature which refers to tissue reaction states that defective endocondral ossification of the bone neoformation between the segments of the osteotomy is related to incorrect fixation. These parameters often vary from author to author and from publication to publication. Among the main extrensic parameters noted are:

• quantity, length and diameter of the fixation pin, • rigidity of the fixation mechanism, and

• the materials used in creating the distraction device. Intrinsic parameters are those related to the tissues involved, such as:

• geometric form, area of the transversal section, density of the elongated bone segments,

• length of the bone neoformation, and

• the tension of the soft tissue of the segment, including muscles, ligaments and fasciae.

All these parameters affect the tridimensional movement of the bone segments during the osteodistraction.

The studies which follow, regarding the vector of distraction, were based upon anatomic conformation of the mandible. The mandible is made of two halves, formed by the body and the rami, which unite at the ends to the body, forming a sharp angle. This angle gives the mandible its "V" shape.

To evaluate the biomechanical effects of the distraction devices which are placed parallel to the anatomical axle of the mandible and parallel to the vector of the distraction, one can use a bidimensional model of the mandible with a transversal perspective. Mandibular Distraction

There are reports concerning the use of distraction to increase the length of the rami, length of the body, amplitude of the medium line or any combination of these. Although it appears to be a simple concept at first, one must keep in mind that the mandible is a three dimensional bone structure, curved, with articulations occuring on both extremities.

Most distractors only work in one direction and simply open the site of the corticotomy. However well this principle has been accepted for long bones, this simple device is not a perfect solution for the craniofacial complex - the bones of this complex do not require only a simple lengthening but a repositioning on all three dimensions of the face.

The problem with three dimensional control can be resolved in the following manner:

- extreme caution in choosing the distraction site to maximize the amount of movement in the desired direction and minimize undesirable side effects;

- the use of more than one distractor simultaneously to be able to control more than one spacial plane at once; and

- the use of a new multi directional distractor.

Careful pre-operatory planning of this procedure is essential to assure accurate vectorization. Correct placement of the distractor can be made easier through the study of a combination of bidimensional cephalometric radiographs, three dimensional computerized tomographies, and computer generated three dimensional models.

Maxillary Distraction The maxilla has been subjected to distraction according to the osteotomy technique established by Le Fort I. Better results appear to be obtained with a osteogenic extraction pushing in an outward direction toward an external structure. This device is fitted through pins in the cranium. The maxilla is fixed to the distractor device through the insertion of an orthodontic instrument (similar to an extra oral arch) or with a fork inserted into the oclusal surface of the upper teeth.

Unfortunately for the patient, this apparatus is wide, grotesque and ugly.

Nowadays, the surgical techniques available for increasing the alveolar ridge are limited, which restricts the placement of implants in a patient with small bone height.

Aiming to perfect current surgical techniques, with the development of a technique based upon the principles of osteogenic distraction which allows the augmentation of the alveolar ridge in a predictable and safe manner, the inventor, after performing studies, has developed an "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", characterized by the surgical process which begins with the fixation of the distractor with internal hexagons and the alveolar ridge, after which you suture these and await a stipulated time period for osseointegration, after which time the patient goes back for a distractor to be fixated, inserted through an inner thread a mold with a counterclockwise thread which then receives on its opposite end a regulating washer followed by a transference guide, so that, by performing this procedure, a measurement is taken for the creation of a prosthesis, and in a second stage, a prosthetic device is adapted to the pillar teeth and placed in the internal cavity of the distractor by a traction screw which was formerly embedded in a contention ring, after which procedure the patient has to return after seven days for suture removal, at which time the activation of the aforementioned traction screw is performed using an activation key with an external hexagonal head. So one can have a clear and perfect idea of what was developed, attached are illustrative drawings which refer directly to the numerical references together with a detailed description of each item as follows:

Figure 1 shows a blown up perspective of the distractor device including the transference guide.

Figure 2 shows a blown up lateral view of the distractor device without the transference guide.

Figure 3 shows a blown up lateral view of the distractor device including the activation key. As illustrated in the figures and as described above in detail, the "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", characterized by the surgical process being initiated by the fixation of the distractor (1) with an internal hexagon to the alveolar ridge, after which it is sutured and there is a stipulated waiting period until osseointegration is complete, when the patient returns and has a distractor fixated (1) receiving through the internal thread a mold (2) with counterclockwise threads, which receives on its opposite end, (3) a regulating washer (4) immediately followed by a transference guide (5) so that through this process a measurement is made for the creation of a prosthesis, which is then, in a second stage the prosthetic device is adapted to the pillar teeth; then (1) a traction screw inserted into the internal cavity (6) of the distractor (7) formerly embedded in a contention ring (8) (7) through the use of an activation key (9) with an external hexogonal head (10).

Based on what has been described and illustrated, one easily notes that the "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE" was developed in order to increase the alveolar ridge in a predictable and safe method, thus opening new perspectives for oral rehabilitation. A method utilizing a distractor device which consists of one or more biologically compatible titanium anchors, a temporary fixed prosthesis, with a metallic contention ring positioned over each region where the biologically compatible anchors and a traction screw for each of these.

The surgical procedure begins with the fitting of the prosthetic device, followed by making a small incision and detachment of the mucoperiosteum above the alveolar ridge of the desired region. Using the prosthetic device as a guide, holes are drilled and the anchors installed at the previously defined locations and depths. Afterwards, the wounds are sutured and then begins the waiting period for osseointegration.

After this waiting period, a new incision is made along with the detachment of the periosteum and with the aid of a number 701 drill bit at high rotation, an osteotomy is performed at the desired location.

The prosthetic device is adapted to the pillar teeth and the traction screws are inserted through the contention rings and attached to the internal orifice of the biologically compatible anchor. The patient returns after seven days to have the sutures removed and to begin the activation of the traction screw. The activation is 0.6mm per day (one and a half turns of the traction screw) for as long as necessary, without fail, until the implant rests upon the contention ring.

Because it is innovative and thus far not included in the scope of this technique, the proposed process fits perfectly into the criteria which define a patent for inventions. Its claims are the following.

Claims

1- "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", is characterized by a titanium distractor screw, traction screws, contention ring, activation key and two transference systems.

2- "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", is characterized by the distractor screw being installed in the alveolar bone, in such a manner that allows the tractioning of a bone block in a vertical direction.

3- "INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", is characterized by the surgical procedure which begins with the fitting of the prosthetic device followed by the making of an incision and detachment of the mucoperiosteum covering the alveolar ridge in question, using the prosthetic device as a guide, perforations are made and the anchors are installed at previously defined locations and depths.

4- ""INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", is characterized by the surgical procedure which begins with the fixation of the distractor (1) with the internal hexagon and alveolar ridge, after which sutures are made and a there is a stipulated waiting period for osseointegration, after which the patient returns and the distractor (1) is fixated (1) by means of its internal thread a mold (2) with counterclockwise threads receives on its opposing end (3) a regulating washer (4) followed next by a transference guide (5) 5- ""INTRODUCED IMPROVEMENTS IN SURGICAL PROCEDURE AND IN THE BONE DISTRACTOR DEVICE", is characterized by the adaptation on the pillar teeth of the prosthetic device and inserted in the internal cavity (6) of the distractor (1) a traction screw (7) formerly embedded in a contention ring (8) after this procedure, the patient returns after a seven day period for removal of the sutures, when the activation of the aforementioned traction screw (7) by using an activation key with an external hexagonal head. (10)