Tissue graft impingement device

A device for determining possible impingement of a replacement tissue graft with a portion of a bone at a joint, the replacement tissue graft of the type to be inserted and secured within a bone passage at the joint. The device includes (1) an elongated support shaft having a longitudinal axis and (2) a head disposed at a distal end of the support shaft. The head has (a) an engagement passage having an axis, the engagement passage configured to engage a guide wire disposed within the bone; and (b) an impingement surface corresponding to the shape of a portion of the replacement tissue graft, the impingement surface spaced from the axis of the groove by a pre-determined distance corresponding to a dimension of the tissue graft.

BACKGROUND OF THE INVENTION 
This invention relates to tissue grafting. 
An increasing number of surgical techniques are now performed 
arthroscopically. For example, arthroscopic procedures include 
reconstructing the anterior cruciate ligament (ACL) as well as the 
posterior cruciate ligament (PCL) in the knee. 
When the ACL has ruptured and is nonrepairable, it is usually replaced in 
the knee using a substitute graft harvested from the patient or from a 
donor. For example, the substitute ACL graft may be selected, according to 
surgeon preference, from a portion of a patellar tendon having a bone 
block or plug at each end. Alternatively, artificial grafts formed 
synthetically or with a combination of artificial and natural material, 
such as a ligament augmentation device (LAD) to which tissue is sutured, 
may be used as a substitute graft. The term "graft" is used herein to 
encompass all of these tissue replacement items. Several ACL 
reconstruction techniques are described in U.S. Pat. No. 5,139,520, 
incorporated herein by reference. 
Referring to FIG. 1, in one technique, an ACL graft 1 is inserted through 
bone passages 2 and 3 formed in a femur 4 and a tibia 5, respectively. 
These bone passages are formed by first using a drill tipped guidewire 
(not shown) to provide a hole extending through the bone followed by a 
larger drill which provides a closed-ended socket larger than the guidance 
hole and having a width at least as large as the width of the ACL graft 1. 
For example, with respect to femur 4, the drill-tipped guidewire initially 
forms a hole 8, and bone passage 2 is formed in the femur only after a 
larger drill is used to ream the original hole 8, so that graft 1 is 
allowed to pass through the roof of the intercondylar notch 6 (the portion 
of femur 4 flanked by two femoral condyles 7). Similarly, bone passage 3 
in tibia 5 is formed by reaming with a larger drill only after a hole 9 is 
drilled by the guidewire. Subsequently, ACL graft 1 is secured in bone 
passages 2 and 3 by sutures 11 and suture anchors 13. The fully formed 
bone passage 3 passing through tibia 5 and accommodating ACL graft 1 is 
hereby referred to as the tibial tunnel. 
A successful ACL graft reconstruction depends on the proper positioning of 
the tibial tunnel through which the graft passes. If the tibial tunnel is 
not correctly positioned, the graft may impinge on the roof of the 
intercondylar notch of the femur when the knee fully extends, potentially 
rupturing the graft. In order to properly locate the position of the 
tibial tunnel to be drilled so that the ACL graft passing through it will 
not impinge on the roof, tibial guide devices such as the ones described 
in U.S. Pat. No. 5,300,077 and PCT publication WO94/00058 are often used. 
These devices use the roof of the intercondylar notch as a reference point 
to position the guidewire for drilling the initial hole. 
The surgeon can also relieve impingement of an ACL graft on the roof of the 
intercondylar notch by performing a notchplasty procedure in which a 
portion of the bone forming the roof of the notch is removed. In general, 
the surgeon removes a portion of the bone of a size large enough to 
prevent impingement. 
SUMMARY OF THE INVENTION 
The invention features an impingement device for determining possible 
impingement of a replacement tissue graft (e.g., an ACL graft) with a 
portion of a bone (e.g., a tibia) at a joint (e.g., a knee-joint), the 
replacement tissue graft of the type to be inserted and secured within a 
bone passage (e.g., a tibial tunnel) at the joint. 
In a general aspect of the invention, the device includes an elongated 
support shaft having a longitudinal axis and a head disposed at a distal 
end of the support shaft. The head includes an engagement passage 
configured to engage a guidewire disposed within the bone and an 
impingement surface corresponding to the shape of a portion of the 
replacement tissue graft and spaced from an axis of the passage by a 
pre-determined distance corresponding to a dimension of the tissue graft. 
Among other advantages, the impingement device allows a surgeon to 
determine whether the graft would impinge upon a portion of a bone before 
the bone passage for the graft is fully formed by the surgeon. For 
example, in an ACL reconstruction, the impingement device allows a surgeon 
to insert a tibial guidewire through the tibia and into the knee joint and 
attach the engagement passage of the device near the end of the guidewire. 
The knee joint is then fully extended and the impingement surface of the 
head is observed (via an endoscope, for example) to determine whether the 
surface contacts the roof of the intercondylar notch of the femur. The 
surgeon, therefore, is able to thereby determine whether impingement would 
occur if the tibial tunnel were to be drilled at the present position of 
the hole formed by the guidewire. In essence, the device serves as a 
surrogate ACL graft for determining impingement. 
Unlike a tibial guide, the impingement device allows the surgeon to 
determine impingement given a selected position of the guidewire 
representing the future position of the tibial tunnel. This is a critical 
distinction, since the surgeon may wish to reference the tibial tunnel 
using anatomical landmarks other than the roof of the intercondylar notch 
of the femur. In contrast, known tibial guides require the surgeon to 
drill the initial hole, and consequently the tibial tunnel, in a specific 
position relative to the roof of the notch. 
Embodiments of this aspect of the invention may include one or more of the 
following features. 
In one embodiment, the head includes a detent mechanism which provides a 
spring-loaded fit between the engagement passage and guidewire, thereby 
facilitating engagement and disengagement of the passage with the 
guidewire. The detent mechanism includes a cantilever member defined by a 
slot formed in the head of the device. 
In other embodiments, the engagement passage may be formed as a groove or a 
hole, either of which engages the guidewire via any suitable fit, 
including an interference fit, facilitates attaching and detaching and/or 
a sliding fit. When the passage is formed as a groove, the impingement 
device is attached and detached to and from the side of the guidewire. On 
the other hand, when the passage is a hole, the impingement device is slid 
over the distal end of the guidewire. The distal end of the support shaft 
can include a neck having an axis offset from the longitudinal axis of the 
shaft. In addition, the axis of the engagement passage can be at an angle 
(e.g., between 45.degree. and 60.degree.) from the axis of the neck so 
that the support shaft does not interfere with nearby bones. 
The pre-determined distance between the axis of the engagement passage and 
the impingement surface can represent a dimension of the cross-sectional 
thickness of the replacement tissue graft (e.g., about 3 mm to about 6 
mm). In addition, the impingement surface can be rounded to more closely 
approximate the shape of the tissue graft at the site of potential contact 
with the bone. 
The device can include a second head at a second distal end of the shaft, 
the second head being used for a bilaterally symmetric joint. For example, 
the head at one end of the device can be used in a left knee ACL 
reconstruction, and the head at the other end of the device can be used in 
a right knee ACL reconstruction. The head of the device is configured to 
be removably detached from the distal end of the support shaft. A number 
of different size heads, each removably detached from the support shaft, 
can be provided, the size of the head related to the particular knee 
involved in the surgical procedure. The device may be made from a material 
such as stainless steel, titanium, or plastic. 
In another aspect of the invention, a method includes steps for determining 
possible impingement of a tissue graft with a portion of a bone at a 
joint, the replacement tissue graft of the type which is to be inserted 
and secured within a bone passage at the joint. 
The steps include: (a) inserting an end of a guidewire into a bone at a 
joint; (b) positioning a device at the end of the guidewire having an 
impingement surface; (c) extending the joint to full extension; and (d) 
determining if the impingement surface of the device contacts the bone, 
thereby determining possible impingement of the replacement tissue graft 
with the portion of the bone at the joint. 
In certain embodiments, steps (b)-(d) above can also be repeated, with the 
surgeon removing a small portion of the bone responsible for graft 
impingement after determining if the impingement surface of the device 
contacts the bone, until no impingement occurs. Thus, the method minimizes 
the amount of bone that the surgeon needs to remove to alleviate 
impingement. 
Fully forming bone passage is generally performed after determining whether 
impingement occurs. 
Other advantages and features of the invention will be apparent from the 
following description and from the claims.

DETAILED DESCRIPTION 
Referring to FIGS. 2A and 2B, an impingement device 10 includes an 
elongated support shaft 12 having a longitudinal axis 14. Impingement 
device 10 includes heads 24, 25 positioned at opposite ends of support 
shaft 12 and supported by narrowed neck regions 18 of shaft 12. Each of 
heads 24, 25 are mirror images of each other relative to plane 13 so that 
one head 25 is used in procedures involving the left knee and the other 
head 24 for the right knee. 
Focusing on the right half of the device (e.g., used to determine possible 
impingement of a left knee ACL graft), narrowed neck region 18 has a neck 
axis 20 offset from longitudinal axis 14 of shaft 12 at an acute angle 22 
to facilitate positioning of head 24 within the joint of the knee. Angle 
22 helps ensure that, when the device is attached to a drill-tipped 
guidewire 40 (FIG. 4A), the device does not interfere with nearby portions 
of bone when initially positioning the impingement device into the joint 
(see FIGS. 4B and 4C and related discussion below). 
Referring to FIGS. 3A and 3B, the head 24 includes an engagement passage, 
here a groove 26, having a groove axis 28 and an impingement surface 30 
bordered on one side by an edge 34. The groove axis 28 is at an angle 32 
from neck axis 20 (e.g., any angle from 45.degree. to 60.degree.) which 
approximates the angle between a tibial plateau 48 (FIG. 4A) and axis 28 
and positions axis 20 parallel to the tibial plateau. Angle 32, together 
with angle 22, helps ensure that the device does not interfere with nearby 
portions of bone not involved in possible impingement of graft 1 (FIG. 1). 
Groove 26 is sized to substantially surround the periphery of the distal 
end of drill-tipped guidewire 40 already positioned in the joint. Slots 
38, 39 are formed to extend through head 24 so that groove 26 can be 
expanded sufficiently to provide a snap-fit engagement to the side and 
outer periphery of guidewire 40. In essence, slots 38, 39 provide a 
spring-like detent for ensuring reliable engagement of impingement device 
10 to guidewire 40 while also permitting removal and replacement of the 
impingement device when necessary. Slot 38 extends from a wall 41 defining 
groove 26 towards an outer surface 42 of head 24, and bends upward towards 
impingement surface 30. Slot 39 extends from an outer surface 44 of head 
24, and curves around the inner surface of groove 26. Thus, slots 38, 39 
form cantilever members 50, 52, respectively for forming the spring-like 
detent mechanism. 
The impingement surface 30 is spaced from groove axis 28, by a 
predetermined distance ranging from A to B (e.g., 3 mm to 6 mm), thereby 
providing an impingement surface which reflects the exterior dimensions of 
ACL graft 1 (FIG. 1). 
FIGS. 4A-4C illustrate an approach for using impingement device 10 in 
determining possible impingement of a replacement ACL graft. Referring to 
FIGS. 4A and 4C early in the ACL reconstruction procedure, drill-tipped 
guidewire 40 is passed from an anterior surface 46 of tibia 5 through the 
bone at an angle oblique to the long axis of tibia 5 into the knee joint. 
Preferably, the lower leg (containing tibia 5) is flexed in the direction 
of arrow 54. Referring to FIG. 4B, the impingement device 10 is next 
inserted through an incision in the skin and soft tissue into the knee 
joint and attached to guidewire 40 via groove 26 of head 24. Again, the 
lower leg is preferably flexed to allow device 10 access to guidewire 40. 
With the knee flexed as shown, impingement surface 30 of head 24 is spaced 
from the surface of roof 6 of the intercondylar notch. In this example, 
only the right half of device 10 is used in the flexed left knee joint so 
that shaft 12 protrudes anteriorly from the knee and does not interfere 
with tibia 5 or femur 4. If the ACL reconstruction were to be performed on 
the right knee, the left half of device 10 must be used. Once device 10 is 
attached to guidewire 40, the impingement surface 30 of device 10 is now a 
surrogate for the exterior surface of ACL graft 1. 
Referring to FIG. 4C, the lower leg containing tibia 5 is then fully 
extended in the direction indicated by arrow 43. Possible impingement is 
determined by observing contact between roof 6 of the intercondylar notch 
of femur 4 and impingement surface 30 of device 10. If there is no contact 
between impingement surface 30 and roof 6, the surgeon can be confident 
that forming bone passages along the hole formed by guidewire 40, followed 
by proper placement of the replacement ACL graft, will result in a 
successful procedure without impingement of the graft. On the other hand, 
if contact is made, the surgeon knows before drilling the bone passage 
through the tibia that there is a possible impingement problem if the 
tunnel is drilled at the position established by guidewire 40. In that 
case, the surgeon can avoid impingement by (1) removing and redrilling the 
guidewire in a new position, or (2) performing notch plasty on roof 6. 
However the surgeon rectifies the possible impingement problem, the 
position of hole 9 formed by guidewire 40, which defines the position of 
the finished tibial tunnel 3 (shown in FIG. 1), is a matter of surgeon 
choice. 
Other embodiments are within the scope of the following claims. 
Although the above embodiment is made from an integral piece of stainless 
steel, variants can be made from any number of suitable materials or 
consist of more than one piece. 
Referring to FIG. 5, for example, a device can include a set of removable 
heads 24A, 24B, 24C of different size having different impingement 
surfaces or different pre-determined distances from the engagement passage 
axis. Heads 24A, 24B, 24C, include a screw portion 60 which is received 
within a corresponding threaded hole 62 formed within the distal end of 
shaft 12. 
Moreover, other arrangements of slots may be formed or otherwise provided 
within the head of the impingement device to provide the spring-like 
"snap-on" engagement of the device to a guidewire. Indeed, in lieu of a 
slot arrangement, other approaches including magnetic means, may be used 
to reliably attach the device to a guidewire. Alternatively, the 
engagement passage can be a hole, in which case the device is slipped onto 
the end of the guidewire. 
It is also appreciated that an impingement device may be suitably 
configured to determine possible impingement of other types of grafts in 
other joints.