Threaded bone tunnel dilator

Details Threaded bone tunnel dilator Threaded bone tunnel dilator

1999-11-01

2003-04-01

Robert, Eduardo C. (Department: 3732)

Surgery

Instruments

Orthopedic instrumentation

Reexamination Certificate

active

06540752

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to attaching tissue and non-tissue members to bone. More specifically, this invention relates to dilating a bone tunnel so as to improve member attachment to a bone.
BACKGROUND OF THE INVENTION
Many medical procedures involve attaching tissue or an artificial member to, or inside of, a bone. For example, repairing a detached ligament frequently involves re-attaching the detached ligament to the bone. Often, the repair involves removing the damaged tissue and replacing it with a graft or artificial substitute.
Many techniques exist for attaching a natural or artificial member to a bone. Sometimes the member is drawn to, and/or secured in, a bone tunnel in the bone. For example, referring to
FIG. 1
, to repair a damaged knee ligament, such as an anterior cruciate ligament (ACL) or a posterior cruciate ligament (PCL), the damaged ligament is often replaced with a graft ligament. Replacing the damaged ligament with a graft ligament involves attaching the graft ligament to the patient's femur and tibia. This is typically done by forming a bone tunnel B
1
in the tibia T, and a coincidental bone tunnel B
2
in the femur F. A graft ligament L is then threaded into the bone tunnels B
1
and B
2
. One end of the graft ligament L is attached to the tibia T, and the other end of the graft ligament L is attached to the femur F.
In some cases, the distal end of the graft ligament L is secured to the femur F with an interference screw (not shown) which wedges the graft ligament laterally against the side wall of the bone tunnel B
2
. The interference screw simultaneously engages both the side wall of the bone tunnel and a portion of the graft ligament L, thereby fixing the graft ligament to the bone with an interference coupling. It will be appreciated that with such an arrangement, secure attachment of the graft ligament L in the bone tunnel depends on the quality and integrity of the side wall of the bone tunnel, as well as the effectiveness of the attachment mechanism which is used to attach the graft ligament to the bone.
Sometimes a member. (both tissue and non-tissue) is mounted on, rather than in, a bone. Although the member may be mounted on the bone, the attachment mechanisms for securing the member to the bone are frequently secured in a bone tunnel. For example, and referring now to
FIG. 2
, to mount a ligament L on a bone N, the surgeon may create a bone tunnel B
3
in the bone N and then insert a suture anchor A in the bone tunnel so that the suture anchor's sutures S extend out of the bone tunnel. Thereafter, the sutures S may be used to secure the ligament L to the bone in ways well known in the art, e.g., by tying a knot K atop a washer W. Again, secure attachment of the anchor A in the bone tunnel depends on the quality and integrity of the side wall of the bone tunnel, as well as the effectiveness of the attachment mechanism of the anchor.
Typically, the surface and integrity of a bone is not highly predictable. For example, a bone does not have constant consistency and hardness throughout. Typically, a bone has a hard cortical outer shell and a soft cancellous inner core. The shell is relatively thin as compared with the core, especially in large bones such as the tibia and femur. This is significant because, when a member (both tissue and non-tissue) is attached to a bone by means of a bone tunnel, a significant portion of the attachment typically occurs in the soft cancellous bone. Thus, the quality of the attachment is typically heavily dependent on the quality of the cancellous bone defining the side walls of the bone tunnel. The quality of the cancellous core varies significantly from person to person and bone to bone.
To achieve a high-quality attachment, the cancellous bone tunnel must provide a high-quality surface and integrity. If the side wall of the bone tunnel provides a poor-quality surface, for example with too many fractures and/or striations, the member may not be well secured to the bone. Similarly, if the side wall of the bone tunnel provides poor integrity, e.g., an integrity like unpacked snow, the member also may not be well secured to the bone.
Furthermore, where a ligament is being mounted directly in one or more bone tunnels (e.g., such as in the ligament reconstruction depicted in FIG.
1
), it is generally important that the ligament osseo-integrate with the side wall(s) of the bone tunnel(s). If the side wall of a bone tunnel provides a poor-quality surface or poor integrity, such osseo-integration will be impeded.
To enhance high-quality attachment in a bone tunnel, surgeons have developed a procedure to enhance the quality and integrity of the side wall of the bone tunnel. This is done by dilating the bone tunnel so as to enhance the density of the bone forming the side wall of the bone tunnel. More particularly, such dilation involves packing the soft cancellous bone outward, in a fashion similar to compacting soft snow. Such prior art dilation typically involves drilling a hole of a pre-determined size into the bone. The drill is typically then removed and a dilator, slightly larger than the aforementioned pre-determined size, is forced through the hole, commonly by hammering. As the dilator advances through the hole, the dilator pushes interfering cancellous bone radially outward. The dilator also pushes the interfering cancellous bone distally.
Because the prior art dilation process typically involves intermittent, sudden forward surges of the dilator, the process is traumatic and may result in inconsistent compacting of the bone. This inconsistent compacting of the bone can also cause the quality and integrity of the side wall of the bone tunnel to vary. Surge advancement also increases the potential for the dilator to assume a path which may be aligned with the direction of the dilator-driving force, rather than the path defined by the original bone hole. In this respect it should be appreciated that an incorrectly-located bone tunnel may cause significant mis-alignment of a ligament attached therein. This can be especially true in the case of an ACL or PCL reconstruction, where such mis-alignment can have serious, long-term, debilitating consequences for the patient.
Thus, what is needed is a novel dilator that accurately advances through a bone and dilates a bone tunnel in a gentle, controlled manner.
SUMMARY OF THE INVENTION
The present invention is a threaded bone tunnel dilator that accurately advances through a bone and dilates a bone tunnel in a gentle, controlled manner. The invention is applicable to any attachment in a bone tunnel or bone canal. The invention provides for progressively expanding a bone tunnel or canal laterally, without significant expansion longitudinally. The invention also provides for dilating a bone tunnel in a gentle, yet extensive manner, without substantial drilling or cutting. The invention also provides for defining a compacted bone tunnel with a smooth or textured surface. The invention provides improved elements and arrangements thereof, in an apparatus and method for the purposes described, which are inexpensive, dependable, and effective in accomplishing its intended purposes.
An embodiment configured according to the principles of the present invention includes a distal, tapered threaded tip and a body mounted on the distal end of a shaft. The proximal end of the shaft includes a drive attachment for rotating the dilator so as to threadingly advance the dilator through bone. The dilator is preferably cannulated so that it can be advanced along a guidewire.
In one preferred method of use, the surgeon first drives a guidewire into the bone. Once the guidewire is emplaced, the surgeon places the dilator over the guidewire, advances the dilator along the guidewire, and engages the bone. Rotating the dilator clockwise threadingly advances the dilator through the bone, until the dilator reaches a desired depth. The tapered leading threads of the dilator open the bone through dilation so as to define the bone tunnel. The trailing smooth cylindr

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