Spinal implant

p0001The invention relates to an implant for spinal surgery, and more generally the osteosynthesis and arthrodesis device.

p0002According to the invention, the spinal implant comprises at one end means for fixing to a vertebra and at its second end a mounting head extending along an axis xx ', said head having an open housing side opposite the means fixing and having a cross section substantially U-shaped, said head being adapted to receive a connecting rod extending transversely to the axis xx 'and the interlock via holding means and by clipping means locking.

p0003Such an implant is already known in document <patcit id="pcit0001" dnum="FR2780269"><text>FR 2780269</text></patcit>. It relates to a spinal implant of the type mentioned above, comprising holding means by clipping which is in the form of a protrusion located in the housing and extending inwardly thereof. To be maintained, the connecting rod is clipped into the lower housing through the protuberance.

p0004In a second step, the rod is locked by an outer ring which is screwed in the mounting head. The outer ring is operative to clamp the side limbs of the mounting head, or at least prevent them deviate. To do this, its inner diameter is substantially equal to the outer diameter of the mounting head, in order to be able to slide on the mounting head and thereby maintain the lateral branches clamped.

p0005This outer ring is essential for ensuring the locking of the rod. In the absence of the ring, the walls could be removed because of the effort that has been provided to insert the rod in the clipping means, particularly after many uses of the implant. Therefore, the rod is not sufficiently clamped in the housing and thus could become detached from the implant.

p0006The use of an outer ring as a locking means substantially increases the dimensions of the implant and forces the surgeon, during the operation, to predict in advance enough space around the implant and then square outer ring.

p0007Another disadvantage arises during assembly of the outer ring, more generally, any element that can come screwed onto the outer surface of the mounting head of such an implant.

p0008Indeed, during the locking operation requiring an outer ring, it is possible that tissue, veins or nerves are rotated by the ring or become lodged between the ring and the mounting head. In addition, in the mounted position, the outer parts and threaded holes present edges that can cut the tissues near the implant. We understand very well that it is desirable to avoid as far as possible, damage human tissues.

p0009Yet another drawback of the known implants to date, lies in the fact that the surgeon must constantly maintain itself while the rod adjusts the position thereof, or when it locks the mounting head.

p0010The invention proposes to remedy these drawbacks.

p0011This object is achieved by the fact that, in mounted position, the holding means by clipping and the locking means are completely accommodated in the mounting head, and that the holding means by clipping (40) are mechanically decoupled means lock (50).

p0012holding means is defined by clipping a means for preventing easy removal of the pin, leaving him free to turn on itself and to translate in a direction.

p0013Means locking means, a means for preventing any movement of the rod relative to the mounting head.

p0014By clipping the holding means are adapted to hold the connecting rod in the mounting head by themselves; in other words, the holding means can perform their function in the absence of locking means, or even before the locking of the mounting head.

p0015It is understood that it avoids the surgeon from having to hold the connecting rod for adjusting the position of the implant or rod, and / or during the locking of the mounting head.

p0016In addition, all means necessary for the fixing of the connecting rod is contained in the mounting head. No element is screwed or inserted on the outer surface of the mounting head, so that it eliminates any risk of damage tissues or veins that are close to the implant.

p0017By clipping the holding means are constituted by a separate piece and are preferably releasable from the mounting head.

p0018Thus, it is possible to change the clipping means in order to adapt to the diameter of the connecting rod that is to be used. This change may also be required if, after several uses, the clipping means no longer perform their function.

p0019The locking means comprise a latch adapted to be screwed into an internal thread in the mounting head.

p0020Thus, in the mounted position, the lock will be completely housed in the mounting head.

p0021The invention will be better understood and its advantages will appear better on reading the following detailed description of embodiments given by way of nonlimiting examples. The description refers to the accompanying drawings in which:<ul><li>the <figref idrefs="f0001">figure <b>1</b></figref> is a front view in exploded view the various components of the spinal implant and the connection rod;</li><li>the <figref idrefs="f0001">figure <b>2</b></figref> is a cross sectional front, in the installed position of the spinal implant and the connecting rod;</li><li>the <figref idrefs="f0002">figure <b>3</b></figref> is an exploded perspective view of the various components of the spinal implant and the connecting rod;</li><li>the <figref idrefs="f0002">figure <b>4</b></figref> is a perspective view of the implant in mounted position and the connecting rod; and</li><li>the <figref idrefs="f0003">figure <b>5</b></figref> is a perspective view of another variant of the spinal implant.</li></ul>

p0022The <figref idrefs="f0001">figure 1</figref> represents the spinal implant in a perspective sectional front.

p0023As seen in this figure, the spinal implant <b>10</b> comprises at its one end fastening means <b>20</b> being in the form of a hook. The latter serves to secure the spinal implant to a vertebra pedicle (not shown here).

p0024The second end of the implant comprises a mounting head <b>22</b> which allows the attachment of connecting rods <b>thirty.</b> These serve to correct the orientation of the spine of a patient suffering from scoliosis, for example.

p0025The implant shown here has transverse and longitudinal dimensions of between 5 and 20 mm. The connecting rods<b>thirty</b> can have multiple diameters, preferably 5 to 6 mm.

p0026The mounting head <b>22</b> of the spinal implant has a substantially cylindrical outer shape of axis xx '. It has an internal thread<b>24</b> and two side openings <b>26.26 '</b> which define two side walls <b>28,28 '.</b>

p0027As seen in <figref idrefs="f0001">figure 1</figref>, The section of the mounting head along a plane (XOY) orthogonal to the implant plane of symmetry, is substantially U-shaped and the lower edge of openings has a semi-cylindrical profile <b>23</b> for supporting the outer surface of the connecting rod <b>thirty.</b>

p0028Internal thread <b>24</b> of the mounting head <b>22</b> is of the "artillery", that is to say, he has an asymmetrical trapezoidal thread.

p0029The advantage of this type of net is that it reduces the radial component of the tightening force. Such an advantage will be explained in more detail subsequently.

p0030The mounting head <b>22</b> further comprises two orifices <b>21,21 '</b> in the side walls <b>28,28 '.</b> During surgery, the surgeon uses an instrument to place the implants. This instrument has at one end two pins which are received in these holes<b>21,21 '</b> to hold the implant.

p0031Once the surgeon has determined the type of connecting rod <b>thirty</b> it will use it instead holding means clipped <b>40</b> in the mounting head <b>22</b> which will serve to maintain the connecting rod in the mounting head before it is locked. The known advantage is to avoid the surgeon to maintain itself the connecting rod while he adjusts the position of the rod and while it locks thereof. During the adjustment of the position, the rod can translate in the holding means<b>40</b> and also rotate around itself. For against, the holding means<b>40</b> can not come out of the mounting head <b>22.</b>

p0032This holding means is in the form of a clip insert <b>40.</b> There are several corresponding inserts of shank diameters <b>thirty</b> different.

p0033These inserts are adaptable in one assembly head <b>22.</b>

p0034The insert <b>40</b> is in the form of a cylindrical part of diameter slightly less than the inner diameter of the opening of the mounting head and has on its lower part a thread <b>42</b> to be attachable to the head by screwing a quarter turn.

p0035It has on its upper part a cylindrical opening <b>44</b> open diameter substantially equal to the diameter of the connecting rod and the opening is slightly less than 180 ° so as to partially cover the connecting rod when the latter is engaged in the insert. It is understood that this commitment is done by applying a light force to the connecting rod to temporarily deform the top<b>46</b> of the cap. This forcible engagement performs clipping of the connecting rod in the insert<b>40</b>.

p0036When the rod <b>thirty</b> is correctly positioned, the surgeon proceeded to lock.

p0037The locking means comprise the internal thread <b>24</b> already mentioned above as well as a lock <b>50</b> intended to be screwed into this internal thread <b>24</b>. As seen in<figref idrefs="f0001">Figures 1 and 2</figref>The latch has a cylindrical shape and has a thread <b>52</b> Type "artillery" capable of cooperating with the tapping <b>24</b> of the mounting head <b>22</b>.

p0038When the latch <b>50</b> is screwed into the mounting head <b>22</b>, Its lower part <b>54</b> is in contact with the outer surface of the rod so as to secure the rod to the implant. The upper part of the lock comprises in a manner known 6-sided orifice<b>56</b> for receiving the clamping tool (not shown here).

p0039The use of thread like "artillery" has the advantage of reducing the radial force when screwing the bolt. Therefore, the side walls<b>28.28 '</b> no longer undergo a radial force which would tend to separate them from each other. Thanks to this type of thread, it avoids the use of an external clamping ring intended to maintain the spacing of the walls.

p0040In any event, even if the residual radial force tending to remove the walls <b>28.28 '</b>The insert <b>40</b> continue to hold the rod <b>thirty</b> since the insert and the mounting head are mechanically decoupled, that is to say that the mechanical forces to which the mounting head <b>22</b> are not transmitted to the insert <b>40</b>.

p0041We now understand that the use of an external clamping ring is completely unnecessary in this device.

p0042Another benefit is explained below:

p0043In locked position, as seen in the <figref idrefs="f0002">figures 4</figref> and <figref idrefs="f0003">5</figref>, the lock <b>50</b> is completely housed in the mounting head <b>22</b> so that the outer profile <b>29</b> the implant is smooth: that is, it has no thread, boss, grooves or roughness which could damage the surrounding tissue.

p0044In the same vein, there are no additional parts to the outer surface of the mounting head, for example clamping rings, that could have sharp edges that can damage the surrounding tissue.

p0045In other embodiments, the implant may have other forms of smooth surfaces <b>29</b> like "smooth profile" is inserted securely into the human body without the risk of internal injury.

p0046Without leaving the invention, the implant can therefore have a profile with a surface of revolution whose meridian feature is a continuous curve and continuously differentiable. In other words, said curve is free of inflection point or cusp so as to obtain a smooth profile.

p0047According to another variant of the invention, shown in <figref idrefs="f0003">5</figref>, The fastening means comprise a screw <b>60</b> intended to be anchored in a vertebra.