Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-06-21
2001-03-20
Buiz, Michael (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S064000, C606S062000, C606S075000
Reexamination Certificate
active
06203543
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to devices for securing objects to bones. More particularly, this invention relates to devices which releasably secure objects to bones such that the object is temporarily axially and rotationally secured to the bone.
BACKGROUND OF THE INVENTION
Various types of surgical procedures now require objects, such as tools or tracking devices, to be temporarily secured to a bone during a procedure. For example, during image guided surgery, it is sometimes necessary to attach active or passive trackers to bones in order to determine the location of a bone with respect to the image. This is required, for instance, for alignment procedures, such as fracture reductions. It is also often necessary to attach active or passive dynamic reference objects to bones. In addition, it is sometimes necessary to temporarily attach objects to bones, such as drill guides or templates to perform a subsequent drilling or sawing operation.
Furthermore, it is sometimes necessary to secure objects to the bone which must remain temporarily secured after the initial surgical procedure. For example, external fixation devices are sometimes secured to bones or bone fragments to hold the bone and bone fragments in place during healing. Also, spinal rods must sometimes be secured to vertebrae, thereby temporarily mechanically immobilizing areas of the spine, to treat certain types of spinal column disorders. Also, to analyze and treat certain joint pathologies, it is sometimes necessary to attach trackers to bones to measure the discrete joint movements, such as, for example, to measure the motion patterns of the human knee.
It has been known in the past to use bone screws to secure objects to bones. Bone screws generally have a coarse thread at one end for engaging the bone and a means at the other end to easily attach clamps or instruments thereto. While bone screws have worked well in the past, they are susceptible to rotational displacement which can either loosen or tighten the bone screw. This rotational displacement can be caused in different ways, such as by the normal cyclical force applied to the bone screw or through inadvertent contact with the object attached to the bone screw by an external source.
It is clear that rotational displacement of the bone screw will affect the object secured to the bone screw. For example, any rotational displacement of the bone screw may cause a rotational displacement of the object with respect to the bone. Furthermore, any rotational displacement of the bone screw may cause an axial displacement of the bone screw along the axis of rotation of the bone screw with respect to the bone. It is clear that any axial and/or rotational displacement of the bone screw with respect to the bone will also cause an axial and/or rotational displacement of the object with respect to the bone.
In some cases, any rotational or axial displacement of the screw can have a significant effect on the procedure. For example, during image guided surgery, the objects, such as tracking devices or instruments, secured to the bone screw will be registered in six degrees of freedom, namely three displacement degrees of freedom and three rotational degrees of freedom. Accordingly, any axial or rotational displacement of the bone screw will cause an axial or rotational displacement of the object and require re-registration of the object secured to the bone screw.
In the past, in order to avoid rotational displacement of the bone screw, and therefore rotational or axial displacement of objects attached to bone screws, more than one bone screw has been used to attach an object to a bone. For example, two or more bone screws, displaced along the bone, have been used to prevent detrimental effects caused by rotational displacement of one bone screw. However, using additional bone screws weakens the bones being treated and increases the length of time of the procedure. In addition, in some cases, it is not practical to use several bone screws because the bones or bone fragments are simply not large enough. Also, use of several bone screws restricts access to the operative site, which can be the case with the vertebrae of the spine.
Accordingly, there is a need in the art for a device which prevents rotational displacement of bone screws. In addition, there is a need in the art for a device which better axially and rotationally secures objects to bones.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to at least partially overcome the disadvantages of the prior art. Also, it is an object of this invention to provide an improved type of device which can better axially and rotationally secure objects to bones.
Accordingly, in one of its aspects, the present invention resides in a device for releasably securing an object to a bone, said device comprising: a rotation restricting member having an engaging element which engages the bone to restrict rotation of the member; a fastening mechanism for fastening the rotation restricting member to a bone screw engaging the bone; a clamp for releasably securing the object to the rotation restricting member or the bone screw; wherein after the fastening mechanism has fastened the rotation restricting member to the bone screw, the rotation restricting element is biased towards the bone such that the engaging element engages the bone to restrict rotation of the member; and wherein releasably securing the object to the clamp axially and rotationally secures the object to the bone.
In a further aspect, the present invention resides in a device for releasably securing an object to a bone, said device comprising: a clamp releasably securable to the object; an axial supporting member for axially securing the device to the bone; a rotation restricting member which, while engaging the bone, restricts rotation of the device; a fastening mechanism for fastening the axial supporting member with respect to the rotation restricting member; wherein the fastening mechanism fastens the axial supporting member to the rotation restricting member while the axial supporting member and the rotation restricting member are engaging the bone; and wherein objects can be releasably secured to the clamp, after the fastening mechanism has fastened the axial supporting member with respect to the rotational supporting member, to axially and rotationally secure the objects to the bone.
In a still further aspect, the present invention resides in a device to restrict rotational displacement of a bone screw, said device comprising: a rotation restricting member having an engaging element which engages the bone to restrict rotation of the rotation restricting member; a fastening mechanism for fastening the rotation restricting member to the bone screw; wherein the fastening mechanism fastens the rotation restricting member to the bone screw while the engaging element is engaging the bone, thereby preventing rotational displacement of the bone screw.
In a still further aspect, the present invention resides in a device for releasably securing an object to a bone, said device comprising: a rotation restricting member having an engaging element which engages the bone to restrict rotation of the member; a bone screw for engaging the bone; a biasing member for axially biasing the rotation restricting element with respect to the bone screw; wherein after the bone screw has engaged the bone, the biasing member axially biases the rotation restricting member with respect the bone screw such that the engaging element engages the bone to restrict rotation of the member; and wherein releasably securing the object to the rotation restricting member axially and rotationally secures the object to the bone.
In a further aspect, the present invention provides a method of releasably securing an object to a bone, said method comprising the steps of: fixing a biasing member to a longitudinal position on a bone screw, said bone screw having a bone engaging end; axially inserting a rotation restricting member onto the bone engaging end of the bone screw, said
Buiz Michael
King Anthony S.
Pervanas Jeffrey
Riches McKenzie & Herbert LLP
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