FR2722679A1 - Expansible arthrodesis implant for insertion between vertebrae - Google Patents

Abstract

The implant is dimensioned to fit between a pair of adjacent vertebrae, and has a composite cylindrical structure including a rigid external shell with a series of perforations through which retractable projections may extend. The projections are supported by a ring of shape-memory material which is ductile when refrigerated. The ring is initially cooled to allow insertion into the cylinder with the projections in a retracted position. When the ring is allowed to reach the temperature of the human body, it changes shape to allow the projections to extend through the perforations into the intervertebral space. The cylinder may be associated with one or more special surgical instruments designed to simplify its implantation.

Description

The object of this patent aims to arthrode two vertebrae

  consecutive, by fixing them together, at the level of the vertebral bodies,

using an expansive implant.

  There are numerous indications for arthrodesis of the vertebral column, either to remedy instabilities of traumatic or degenerative origin, or to straighten an uert4braZe column deflected by scoliosis or kyphosis. The seat of choice for arthrodesis between the vertebrae is located at the vert4brauz bodies which represent the center of rotation of the motion

o0 of the spine.

  It has been proposed to bind the vertebral bodies together by means of screws, fixed in the vertebral bodies and joined together by rods, plates or cables, but the anterior approach necessary for the installation of the material is extremely dilapidated. for the abdominal or thoracic wall and the holding of the osteoarthritis material. internal synthesis of the bodies

  vertebral, in the cancellous bone is random.

  We. a propos4 ds to set up implants, of various shape, cylindrical, conical or prismatic in Z 'intercorporeal space, separating deu = vertebral bodies consecutive and occupied, in the healthy subject, by the

intervertebral disc.

  These implants pose two problems: A) the choice of the approach first: - either anterior with all the dangers of crossing the superficial planes and the thoracic or abdominal viscera;

  - either later with - the danger of injuring the nervous system and Za lasts -

  mother. B) mounting stability can be achieved: - either by screwing the implant into a previously milled and tapped orifice, but these are dangerous maneuvers near the neuron at the back and viscera at the front, - or at pZacer the implant between the vertebral bodies preaZabZlement separated by uo any device, but this spacing maneuver obige

enlarge Za track first.

  rtL therefore seemed wise to us to propose an inter-corporaZa implant

  expanding vertebral, allowing to restore an intervertebral space

  normal and securely fix two consecutive vertebral bodies.

  As this implant is presented in a retracted form during placement, it can be placed by a reduced first route, preferably by a laparoscopic, transperitoneal, subperitoneal or

pleuroscopic.

  lBAD ORIGINAL The implant object of the present patent is composite in ceZa that its structure includes a rigid external shell, which can be made either in metaZ, preferably Ze titanium, or other biocomnpatibZe material, resistant and non-magnetic and internal parts intended, in activated position, protrude into holes in the shell, provided for this purpose and placed

  perpendicular to the axis of the hull.

  The internal parts are retractable appendages intended to protrude into the inter-corporeal space when the implant is definitively

  placed between two vertebral bodies.

  On the contrary, when you set up the implant, they are retracted within the hull which allows for easy and atraumatic fitting. The device which is the subject of this patent has two parts to be described: A) The shell made of titanium or any other non-magnetic and resistant material, has the preferential shape of a hollow cylinder including a diameter

  corresponds to the thickness of the intervertebral disc that one wishes to pair.

  Progressive lengths are to be expected according to the size of the different cervical, dorsal or lonbar vertebrae and according to the morphology of the

different individuals.

  Lengths of about 1 cm to 3 cm are expected to be 5 mm in 5 minutes.

  The diameter of the seal must correspond exactly to the height of a normal intervertebral disc on the floor to be measured and can be caZlcuZé with

  precision on the pre-operative radiographs.

  It is necessary to provide for successive diameters ranging approximately from

5 to d15 mm.

  the thickness of the hollow cylinder must allow good resistance of the implont

with pressure.

  At least four perpendicular orifices of the cylinder axis are provided on the shell, diaro'tralZement opposite two by two and located nearby

from both ends of the cylinder.

  Each of these curved quadrangular orifices has a calculated length so as to represent a third of the circumference of the cylinder and a width sufficient to allow the soft friction passage of the appendage

  expandable or aiZette once it is in the deployed position.

  The two ends of the hollow cylinder are fixed: - a cone, the base of which is fixed to the base of the cylinder at the same circumference as the latter and the blunt end of which is intended to facilitate the penetration of the impentant into the space between vertebral, safe to

  trauma to the peri-vertebral soft tissue.

2 SAD ORIGINAL

  - ur. a screw is provided at the other end of the cylinder allowing the attachment of the impZant to a threaded introducer plate, for setting in place

  place and handling of the impZant.

  - a mark is fixed on the introducer rod so as to control the rotation of the implant. Indeed, the orifices located on the cylinder must be located, when the implant is in place, facing the vertebral plates so that, when activating the distracting and stabilizing fins, the latter are applied forcefully against the endplates

adjacent and fix the implant.

  B) the 6 retractable parts of the implant are formed by four fins, or appendages, arranged two d deu-x on Za circumference of a ring of n "taZ

o memory of form ".

  It should be remembered that "shape memory metals", in principle titanium alloys and other metals, have the characteristic

  particular to be maZlléables after cooling.

  This allows to give them a shape facilitating their implementation.

  The shape memory material returns to its initially determined geometry

  as soon as it is the temperature of the human body.

  The fins have a parallelepiped shape, designed to be able to slide freely into the orifices of the cylindrical shell so as to protrude by one to a few millimeters in the expanded position and to withdraw completely.

  in the cylinder in the retracted position.

  These fins are oriented perpendicular to the axis of the cylinder.

  A curved cylindrical groove for retentively receiving a ring of shape memory material is provided at the axial base of each appendage.

  Two = rings of this material are provided for each implant.

  The fins are mounted two by two, diametrically opposite

on each of the rings.

  At the ordinary temperature of the human body, the implant is presented as a cylinder with a conical ex-end and a threaded end with four fins diametrically opposite two by two and located asymmetrically with respect to the middle of the axis of the cylinder. These fins make eaiZZie of

  one to a few millimeters on the surface of the cylinder.

  Other arrangements of these fins can be envisaged to meet

  with particular deformation of the spine.

3 ORIGINAL BAD

  After the impassant has cooled, either by freezing in a cooling device, or by simply using a cryogenic bomb, the ring of memory material retracts, allowing the fins to enter the interior of the hollow cylinder so that the implant has a smooth external surface for Z introduction into the inter-vertebra space. Once Z 'implant introduced in its cylindrical form Zisse in Z' intervertebral space, Z 'ring of memory material resumes its primitive form in a few minutes, under the effect of the temperature of the human body and Zez aiZettes fixed symmetrically on its periphery , emerge through the holes provided for this purpose in the cylinder and forcefully press against

  the corresponding vertebral plateau.

  This gives a spacing of the two adjacent vertebrae, restaurant

  a normal intervertebral space and a solid fixation of the implant.

  The implant, in its cooled form, can be placed by a minimal approach, by laparoscopy, or by thoracoscopy, or by retropz4ritoneat approach. The implant may have, in addition to the four orifices intended for the attachment of the retracted appendages, other orifices intended to fill the cylinder

  hollow with bone grafts to obtain an intervertebral arthrodesis.

  The pZace placement process is as follows: - The intervertebral disc is approached by the route first chosen by

  Operator, preferably under extemporaneous radioZogic control.

  - The intervertebral disc is excised by means of forceps, curettes, rotary devices, vacuum cleaners, the space thus created is cleaned of all free fragments which could emerge in the vertebral canal Iors

the introduction of the implant.

  - the height of the intervertebral space is measured by means of templates

successive diaintres.

  - During these maneuvers, the vertebral endplates must not be used because iZs represent the resistant part of the vertebraZ body on which

  will support the expandable appendages.

  - The diameter of the implant is chosen similar to the diameter of the largest

  template that can be introduced with gentle friction.

  - The Zongueur ds the implant was calculated according to the taiZZle of the body

  vertebral on pre-operative pictures.

  - The implant chosen, previously cooled, is introduced. Its position is

radiologically controlled.

  àAD ORIGiNAL - the ring of memory material resumes its primitive form, under the effect of the warmth of the human body and its retractable effects make it a

the surface of Z'impZant.

  - The importance of the distraction can be chosen by varying the size of the tabs and the mechanical characteristics of the ring of memory material. - If the operator wishes to perform a complementary arthrodesis, it is advisable to fill in, by the orifices provided for this purpose, a hollow cytometric aid

  of spongy bone grafts taken from the patient's iZiac crest.

  - Following the pre-operative pZan u. or more impZante can be mie

in place.

ORIGINAL BAD

Claims (4)

RESELL   1) ImpZant intended to be placed between the vertebral bodies of two adjacent vertebrae and characterized by a composite structure including a rigid external shell perforated with orifices and internal retractable appendages intended to protrude into the intervertebral space when they are expanded6. 2) Device according to Za claim 1, characterized in that tee retractiZes appendages are arranged on a ring of memory material, having the property of becoming ductiZle Zi when cooled, allowing to enter Zes appendages Z 'inside the cylinder in poeition introwduction and regain its shape and mechanical qualities when it is uhwain body temperature, thus causing the protrusion of the appendages in Z 'space intervertebraZ.   3) Device according to Zes claims 1 and 2 combining an outer shell   rigid, whatever shape and material eZZe is and one or more parts   internal expandable under the action of a shape memory material.   4) Devices according to claims 1, 2 and 3 for putting   in place Z'implant surgically, as templates, introducer tubes,   introduction and orientation rods of the implant. BAD ORmGièL