The invention relates to spinal osteosynthesis systems.
Spinal osteosynthesis systems generally comprise bone screws, such as pedicle screws. Sometimes, during the surgical operation, one or more screws are not screwed fully home, that is, the cortical thread is not fully engaged in the bone of the vertebra. This occurs for various reasons. One reason may be because the screw is too long and because, if it were screwed fully home, the distal end of the thread would re-emerge from the bone on the opposite side to the side via which the screw entered, digging into the tissues located on that side. Another reason may be an anatomical defect leading to the fact that, if the screw were screwed fully home, it would be screwed in further than the other screws of the osteosynthesis system. This leading to exaggerated and difficult-to-achieve bowing of the connecting member. To avoid this, the surgeon does not screw the screw fully into the bone, leaving the proximal part of the cortical thread disengaged from the bone. However, this has the disadvantage of making the screw unstable in the bone because this screw is not tight, as well as the disadvantage of leaving bone threads outside the bone in which the member is anchored, which leads to damage to the surrounding tissue because of the presence of the sharp corners of the screw thread.
One object of the invention is to provide a system which makes it possible to better stabilize an anchoring member while at the same time better isolating the non-engaged anchoring part from the adjacent environment.
This and other objects are achieved by the present invention, which is a spinal osteosynthesis assembly comprising an anchoring member having a head with a bone engaging portion, and at least one packer that contacts bone, and is able to be coupled to the anchoring member.
Advantageously, the part of the bone engaging portion of the anchoring member which is not engaged in the bone finds itself at least partially surrounded by the packer which isolates it from the adjacent environment. Additionally, since the packer contacts the bone, this provides better stability. In consequence, the anchoring member is stabilized and the non-engaged part of the bone engaging portion can no longer damage the tissue surrounding the anchoring member.
Advantageously, the packer has a slot such that the packer forms a non-closed annulus.
Advantageously, the packer is elastically deformable to facilitate movement of the bone engaging portion through the slot. Thus, the packer can be fitted over the anchoring member when the latter is already anchored in the bone.
Advantageously, the packer is in the shape of an annulus and the packer has a lip, while the anchoring member has a groove such that engagement of the lip with the groove facilitates coupling the packer to the anchoring member. Thus, the packer may be clipped onto the anchoring member in a simple movement. Also advantageously, the lip may be discontinuous.
Advantageously, in addition to the lip, the packer has a recess and is stackable to another packer via engagement of the lip of one packer to the recess of another packer.
There is also provided, according to the invention, a surgical method exhibiting the steps of fitting the packer onto the anchoring member, and inserting the anchoring member into the bone.
Advantageously, the method exhibits the steps of fitting the anchoring member into the bone, and then fitting the packer to the anchoring member.
Advantageously, the method exhibits an additional step of anchoring the anchoring member to the extent that the packer contacts the bone.