Alignment system for bone fixation

An alignment guide for setting the position and depth of a guide pin to be inserted into a bone. The alignment guide includes a mechanical assembly for deploying a calibrated guide rod along a selected external surface of the bone and for adjusting the guide rod so it lies parallel to a desired path extending through the bone for a selected distance. The position and orientation of the guide rod may be adjusted using imaging means for viewing the location of the desired path extending through the bone parallel to the guide rod. The alignment guide is mechanically linked to apparatus for subsequently inserting a guide pin into the bone parallel to the guide rod. In one embodiment the alignment guide is designed to aid a surgeon in centering the guide pin to be inserted in the femoral head and neck without repeated trial-and-error drilling. This shortens the operation time and reduces the radiation due to prolonged exposure to fluoroscopic equipment and reduces the risk of possible complications from the surgery.

BACKGROUND OF INVENTION

This invention relates to apparatus and methods for more precisely aligning guide rods and guide pins into bones for bone fixation.

To better understand the problem faced by the inventor and resolved by the invention reference will first be made to the prior art shown inFIGS. 1-4.

Currently available femoral nail systems for the fixation of femoral or certain types of hip fracture and the prophylactic fixation of pending hip or femoral fracture have been described in several trade publications including: (a) The Titanium Femoral Nail System (Synthes); (b) TRIGEN® IM Nail System (Smith+Nephew, Inc.); (c) Intramedullary Hip Screw Nail (Smith+Nephew, Inc.); (d) M/DN® Intramedullary Fixation (Zimmer, Bristol Myers Squibb Co.); (e) AIM® Titanium Femoral Nail System (DePuy ACE, Johnson & Johnson Co); (f) GAMMA Locking Nail (Howmedica); and (g) UNIFLEX Nailing System (BIOMET). These known systems have design features, as shown inFIGS. 1A,1B, and1C, which allow insertion of metal rods (e.g.,102), also referred to herein as an intramedullary nail (IM nail), into the medullary canal of the femur (e.g.,104) and insertion of additional lag screws (e.g.,106) or blades (e.g.,108) through slots in the intramedullary nail (IM nail),102, into the femoral head (110) and neck (112) for additional stability of fracture fixation.FIG. 1Ashows the use of two lag screws in the femoral head.FIGS. 1B and 1Cshow the use of a single blade108or screw106along the center line of the femoral head and neck. As shown inFIG. 2, known fixation systems include a device commonly called a drill guide, a targeting device, or aiming arm (120) attached to the top end of the IM nail to ensure the correct insertion of lag screws (106) or blades (108) through slots in the IM nail.

Correct positioning of the IM nail102is critical to ensure the lag screws or blades are placed in the center of the femoral head110and neck112in both anteroposterior (AP) and lateral planes for the single screw or blade. For the two screw system as shown inFIG. 1A, the IM nail102must also be positioned to cause the two screws to be placed parallel to each other in the AP view and in the center of the femoral head and neck in the lateral view. However, no device or guide is available at this time to aid in the correct placement of lag screws or blades in the center of the femoral head and neck. As shown in the cross-sectional diagram ofFIG. 3(AP view), since the depth of the IM nail102is not exactly defined relative to the femoral head and neck, a guide pin130driven by means of guide120(seeFIG. 2) into the femoral head may be too high (position A) or too low (position B), rather than being in the correct center position C. Likewise, as shown in the top (lateral) view ofFIG. 4, since the rotation of the IM nail102is not exactly defined relative to the femoral head and neck, a guide pin130driven via the drill guide120into the femoral head may be too anterior (position D), or too posterior (position E), rather than being in the correct center (position F). Thus, in order to obtain correct placement of the guide pin in the center of the femoral head and neck, the surgeon must perform fine-tuning, trial-and-error adjustment by changing the depth and rotation of the IM nail to vary the position at which the guide pin is inserted and repeatedly drilling with the guide pin130under fluoroscopic image intensification until a correct guide-pin position is confirmed by anteroposterior (vertical) and lateral (horizontal) views.

This trial-and-error adjustment increases the length of time a patient has to undergo an operation. It also increases the risk of bleeding, wound contamination and subsequent infection. It also increases the likelihood of bone damage from repeated drilling and potential iatrogenic fractures. This also adds unnecessary radiation exposure to the patient, surgeon, and other operating room personnel.

It should also be noted that inadvertent drilling beyond the articular surface of the femoral head is a problem with the presently available systems.

Also, it is frequently difficult to confirm the position of the guide pin in central axis or near the central axis line of the femoral neck and head because the drill guide and its handle hide the true lateral view of the femoral head and neck even where a radio-lucent drill guide is used.

It is an object of the invention to provide apparatus and methods to overcome the problems discussed above.

SUMMARY OF THE INVENTION

Apparatus and methods embodying the invention include an alignment guide for setting the position and depth of a guide pin to be inserted into a bone. The alignment guide includes means for deploying a guide rod along a selected external surface of a bone, and for adjusting the guide rod so it lies parallel to a desired path extending through the bone and for a selected distance along the length of the bone. The apparatus includes means for subsequently enabling a guide pin to be inserted within the bone along the desired path, parallel to the guide rod. The means for adjusting the guide rod may include imaging means for viewing the location of the desired path extending through (e.g., the center line) the bone and the spatial relationship between the desired path (e.g., the center line) of the bone and the guide rod whereby the apparatus may be used to drill a hole through and along the desired path (e.g., the center) of the bone for a distance also identified by the guide rod. Note that in the discussion to follow the term “guide pin” refers to a pin driven into, or through, a bone producing a path which functions as the axis and guide for a screw or blade to be subsequently inserted into the bone. The term “guide rod” as used herein and in the appended claims refers to a rod positioned externally (over, below or on either side, but not within the bone) to a bone to enable a drill guide to be properly positioned to propel the guide pin in the corresponding bone.

In one embodiment an alignment guide mounted on a drill guide is used to control the position or point at which the guide pin is inserted into the bone and the distance to which guide pin is drilled/inserted into the bone. The alignment guide includes a guide rod which is deployed externally to and along the bone to be drilled (i.e., non-invasively to the bone) and includes adjusting means for positioning the guide rod until it lies parallel to a desired plane running through the bone to be drilled. A drill can then be used to propel a guide pin along a desired (anticipated) path.

One embodiment of the invention is directed to a new alignment guide to aid a surgeon in centering the guide pin to be inserted in the femoral head and neck without repeated trial-and-error drilling. This shortens the operation time and reduces the radiation due to prolonged exposure to fluoroscopic equipment and reduces the risk of possible complications from the surgery.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 5-7show various aspects of the apparatus embodying the invention. Different views of the alignment guide10embodying the invention are shown inFIGS. 5A,5B,5C and5D. The alignment guide10is designed to be mounted on a drill guide120(seeFIGS. 6A,6B) to help determine the positioning and orientation of the drill guide120to ensure that a guide pin130is inserted into a selected bone at the appropriate angle (laterally and vertically) and for the desired distance (depth). The alignment guide10includes a mechanical assembly for deploying a calibrated guide rod24along the surface of a selected bone. The tip of the guide rod24may be pointed to enable it to penetrate soft tissue surrounding the selected bone; but the tip of the guide rod is blunt enough to avoid injury to neurovascular structures. The alignment guide10is linked to the drill guide120so that when the drill guide is used to insert a guide pin into the selected bone, the guide pin is inserted into the selected bone along a path parallel to the guide rod.

The alignment guide10includes a base12with positioning slots14aand14band a post16extending vertically upwards from the base. Base fastening screws15may be used to secure the alignment guide10to drill guide120. The base12is designed to enable the alignment guide10to be attached to an existing drilling guide120, also denoted as a targeting device, or an aiming arm, and includes means (slots14a,14b) for producing fine longitudinal adjustment to obtain correct AP (vertical) alignment between a guide rod24and a guide pin130.

The alignment guide also includes a guide rod holder18with two tubes20and22for holding one or two calibrated guide rods24. In a single blade or lag screw system (seeFIG. 1Bor1C), one of the two guide holder tubes (20,22) holds one guide rod24. In a double lag screw system (see FIG.1A), each one of the two tubes (20,22) of the guide rod holder18holds a guide rod24. The guide rod holder18can be moved up and down post16and can be fixed in position via a set screw181, or any suitable pinning arrangement. As discussed below, moving the guide rod holder18enables the guide rod to be moved closer to, or away from, the selected bone in order to image the guide rod and guide pin path within a selected viewing screen and/or to accommodate persons having more or less soft tissue about the selected bone. Thus, the post16includes means for vertical height adjustment of the guide rod holder18to enable the obtaining of a correct lateral alignment between a guide rod24and a guide pin130and the long axis of the selected bone (e.g., femoral head and neck).

The tip of the guide rods which extends beyond the guide holder18may be positioned to within a given distance (e.g., 5 mm seeFIG. 6B) of the articular surface of the femoral head. The guide rod24is calibrated to measure the maximum desired distance to the articular surface and to then use that information to set the maximum allowable penetration depth of the guide pin130into the femoral head to avoid inadvertent penetration into the hip joint.

FIG. 6Ais a perspective diagram showing the alignment guide10mounted on the drill guide120. Note that when the alignment guide10is mounted on the guide drill, the guide rod24held in tube20(or22) will run parallel to the anticipated line that the guide pin130will follow when inserted into the bone. A drill (not shown) is coupled to the guide pin130to impel it forward as further discussed below. The handle123of the drill guide120is connected to an arm124which at its distal end is coupled to the IM nail102and secured thereto via a screw125. The drill guide120, the handle123and the arm124are secured to each other by means of a screw122. As already noted, in the apparatus shown inFIGS. 6A and 6B, the guide rod24is coupled to the drilling guide120such that the anticipated path of the guide pin130runs parallel to the path defined by guide rod24. For the single screw or blade system, using an imaging device to view the femoral head110and the neck112and the projection of guide rod24, the drilling device120may be moved up and down and rotated until the AP (vertical) view and the lateral view indicate that the anticipated path of guide pin130, which will be parallel to guide rod24, would in fact pass through the center of neck region112and femoral head110. Furthermore, by using a calibrated guide rod24, it is possible to determine how far the guide pin130should be inserted into the bone to be within the predetermined distance (e.g., 5 or 10 millimeters) of the articular surface of femoral head110.

A method for using the alignment guide10linked to the drill guide unit120, as shown inFIGS. 6A and 6B, may be as follows:1 The medullary canal of the femur118is prepared for the insertion therein of an IM nail102. The IM nail-drill guide unit120is assembled and the IM nail102may be introduced into the prepared medullary canal of the femur, as shown in FIG.2.2. The alignment guide10is attached to the drill guide as shown inFIGS. 6A and 6Bby use of base fasteners15in slots14a,14b, as shown inFIGS. 5A and 5D.3. A calibrated guide rod24is inserted into the tube20or22of guide rod holder18mounted on post16of base12as shown inFIGS. 5C and 5D. Using the base fastener arrangement (slots14a,14band base fasteners15) of alignment guide101fine longitudinal adjustment may be made until the guide rod24is aligned with the center line of the drill sleeve26, or partially inserted guide pin130, as shown inFIGS. 6A and 6B. The alignment between the guide rod24and the guide pin130remains fixed during the remainder of the procedure. This is significant since guide pin130will then follow an anticipated path through the neck and femoral head bone section which is parallel to the guide rod24as deployed along the bone.4. The length of the guide rod24extending over the bone is adjusted to position its tip within, for example, 5 mm of the articular surface of the femoral head as shown inFIGS. 6A and 6B. Using a calibrated guide rod enables the determination of the preferred distance the guide pin has to be inserted within the selected bone.5. The IM nail102may be raised or lowered or rotated by, for example, applying manual pressure to handle123and/or arm124and/or tapping on screw125. For a single screw or blade system (seeFIGS. 1B and 1C) the IM nail102is slowly advanced under fluoroscopy, or under any similar imaging system, until the guide rod24is aligned with the center line of the femoral head110and neck112, as shown inFIGS. 6A and 6B. For a two screw system, as shown inFIG. 1A, two parallel guide rods would be mounted in tubes20and22to produce the two parallel paths for the guide pins to follow.6. To achieve lateral (rotational) adjustment, the guide rod holder18is lowered along post16(seeFIGS. 5A,5D) until the guide rod rests on the skin surface of the anterior aspect of the patient's hip joint as shown for position A in FIG.7. The lateral (top) view of the femoral head and neck and the guide rod may be displayed on a screen (not shown) which would display an image as shown in FIG.4. From the lateral display and knowing the projection of the guide rod24onto the bone, the anticipated line which the guide pin will take when inserted into the femoral head and neck may be deduced. [Note: If it is not possible to obtain a lateral view of the femoral head and neck and the guide rod in the same screen, the guide rod is withdrawn and reintroduced through the soft tissue along the anterior aspect of the femoral head and neck as shown for position B inFIG. 7, without going into the bone.]7. The IM nail drill guide120with the alignment guide10is rotated until the guide rod24is parallel to the long axis of the femoral head and neck as shown in FIG.7.8. The distance the guide pin130is driven into the selected bone is set according to the measurement obtained from the calibrated guide rod.9. The IM nail drill guide unit120with the alignment guide10is now positioned to provide correct placement of the guide pin130in the center of the femoral head and neck in both the AP (elevation) and lateral (horizontal) planes.10. A drill attached to the guide pin can then propel the guide pin through the bone along the anticipated path for the desired length. Subsequently, a reamer may be used to increase the size of the hole and a screw or a blade may be superimposed over the guide pin to hold together the trochanter, the neck112and the femoral head110.

The invention has been illustrated by showing how the alignment guide10is attached to an existing drill guide120. However, it should be appreciated that the invention may be practiced using any specially designed piece of equipment incorporating the function of the drill guide120and the alignment guide10. That is, the invention is directed to a guide rod which may be manipulated to lie in a plane parallel to a bone through which a guide pin is to be inserted. The guide rod is coupled to a guide-drill in such a manner that the guide pin, propelled through the bone by a drill (not shown), follows a path through the bone which is parallel to that of the guide rod.

The invention has been illustrated for the case of the hip bone. But it should be appreciated that the invention is suitable to take care of any other bone (e.g., the humerus).

The invention has been illustrated with the path of the guide pin going through the center of a selected bone. But it should be understood that other paths may be selected, as in the case of the two screw system.