Endoscopic drill guide

Abstract: An endoscopic drill guide (1) for locating the proper position of a graft tunnel for endosteal fixation of a substitute ligament or graft between two bones, such as a tibia and a femur. The drill guide (1) includes a shaft (3) with an offset hook (4). The drill guide (1) is inserted through a graft tunnel drilled in the tibia, and the offset hook (4) is positioned so that it engages the posterior aspect of the femoral notch. A guide pin (6) is inserted through the drill guide (1) and driven into the femur to properly position drilling of a graft tunnel in the femur.

Description: The present invention relates to an endoscopic drill guide for properly locating the position to drill a tunnel for endosteal fixation of a substitute ligament or graft. When a ligament or tendon becomes detached from the bone, surgery is usually required to resecure the ligament or tendon. Often, a substitute ligament or graft is attached to the bone to facilitate regrowth and permanent attachment. The reattachment procedure involves drilling of a graft tunnel between two bones, for example, the tibia and the femur. To achieve optimal results, it is important that the graft tunnel be drilled at a particular angle and location through the tibia and femur. Ordinarily, an incision is made to access the proper area for drilling a tunnel through the tibia. A guide pin is placed through the incision and driven into the tibia. A drill is then placed over and guided by the guide pin during the drilling of the graft tunnel through the tibia. A problem arises in locating the proper position for drilling the graft tunnel in the femur. The ideal location for the graft tunnel is 7 mm in front of the posterior aspect of the femoral notch. Ordinarily, the location for drilling the graft tunnel in the femur is determined in one of two ways. The first method is to insert the guide pin through the incision and the graft tunnel in the tibia and into the femur. The drill is then placed over and guided by the guide pin during drilling of the graft tunnel in the femur. The problem with this method is that the femur is difficult to see through the graft tunnel in the tibia. Thus, determining the proper location for the graft tunnel in the femur must often be accomplished by guesswork. The second method is to drill the graft tunnel in the femur in the opposite direction from the outside. Although this method is more accurate, it involves making a second incision which results in unnecessary fluid loss and an additional scar. A further disadvantage of the above two methods is that neither permits testing of graft isometry or notch impingement prior to attachment of the graft. Such testing enables a more secure graft attachment, resulting in rapid healing and stronger regrowth. EP-A-0 495 487 discloses a surgical kit for arthroscopic repair or replacement of the interior cruciate ligament. Said surgical system comprises a placement guide which is placed through a medial port in the knee. A guide drill is inserted through a shaft of said placement guide to drill a pilot hole in the intercondylar notch. Said surgical kit comprises further means for forming a tibial osseous tunnel. Said means comprises a guide pin adapted to be placed through the tibia to define a center line for said tunnel and means for removing tibial cortical bone surrounding the guide pin. Said system further comprises a guide drill for drilling a femoral guide hole beginning at said pilot hole and a reamer adapted to be placed over the guide drill whereby said reamer may be guided through the femur along the guide drill to form a femoral osseous tunnel. Said EP-A 0 495 487 belongs to the state of the art with respect to Art. 54 (3) EPC only (novelty). The present invention overcomes the above-mentioned problems in the prior art by providing an endoscopic drill guide for properly locating the position to drill a tunnel for endosteal fixation of a substitute ligament or graft comprising a) a shaft equipped with a cannula for receiving a guide pin and with longitudinally spaced markings for indicating the required length of graft, and b) an offset hook at one end of said shaft for engaging a notch in a bone and positioning said shaft at a predetermined location relative to said notch. The offset hook engages a notch in the femur and automatically aligns the shaft on the femur at a predetermined distance from the notch. For proper alignment of a drill guide for drilling a graft tunnel in a femur, the offset hook is laterally displaced from the center of the shaft by a distance of 4 to 8 mm and in particular 7 mm, 6 mm, or 5 mm, or anywhere in between depending on the application. The shaft is cannulated for receiving a guide pin, the guide pin being pushed through the shaft and driven into the femur at the predetermined location relative to the notch. The guide pin serves to guide a cannulated drill to that location for drilling the graft tunnel. The shaft is provided with longitudinally spaced markings for indicating the required length of a graft to be passed through the tunnel, the markings preferably being spaced in predetermined longitudinal increments of about 10 mm. The drill guide is preferably provided with a cannulated handle, preferably made of aluminum. The shaft and offset hook are preferably formed of a high tensile strength steel, such as Carpenter 630. The cannulated drill guide of the present invention to locate the proper position for drilling a tunnel for endosteal fixation of a graft between a first bone (such as a tibia) and a second bone (such as a femur) is used in following manner: drilling a tunnel through the first bone; inserting the cannulated drill guide through the tunnel and engaging a notch in the second bone with the offset hook of the drill guide, the offset hook aligning the drill guide at a predetermined location relative to the position of the notch; pushing a guide pin through the drill guide and driving it into the second bone at the predetermined location; and drilling a graft tunnel into the second bone at the location of the guide pin. Optionally a cannula with a silicon dam is inserted into the tunnel prior to the insertion of the drill guide to reduce fluid loss from said tunnel. Advantageously, the present invention permits testing of graft isometry and notch impingement with the offset hook in place. If too much movement is observed during graft isometry testing, the position of the offset hook in the notch can be adjusted. Potential notch impingement can also be evaluated by extending the joint into 5° of hyperflexion. If the shaft of the drill guide restricts hyperextension, a notchplasty can be performed and impingement checked again. Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. Figure 1 shows the drill guide of the present invention. Figure 2 is a side view of the shaft of the drill guide with the guide pin inserted. Figure 3 is a front view of the offset hook of the present invention without the guide pin. Figure 4 shows the drill guide in use. Figure 5 is an expanded view of the offset hook in use with the guide pin inserted. Referring first to Fig. 1, the drill guide of the present invention, indicated generally by reference numeral 1, consists of a tubular shaft 3 with an offset hook 4 at one end. A handle 2 is preferably press fit onto the opposite end of shaft 3. Handle 2, preferably formed with aluminum, and shaft 3 are both cannulated for receiving a guide pin 6, as discussed in further detail below. Said cannula 5 is preferably arranged coaxially with the tubular shaft 3. The offset hook 4 is a substantially flat extension of one end of the tubular shaft 3. The hook 4 is preferably substantially S-shaped such that it initially extends in a direction parallel to the longitudinal axis of the shaft 3 and substantially in alignment with the outer jacket of the shaft 3 , then curves away from the longitudinal axis, then curves back to extend in a direction parallel to the longitudinal axis of the shaft, thus defining the S-shape. The hook 4 may be integrally formed with the shaft 3 The hook 4 is preferably about 2 to 3 mm and in particular about 2.4 mm wide and about 1 to 2 mm and in particular 1.14 mm thick. The length of the hook 4, from the end of the tubular shaft, is about 15 to 25 mm and in particluar 19 mm. The offset portion, which is offset from the longitudinal axis of the shaft 3 and extends parallel to the shaft 3, is preferably about 4 to 8 mm and in particluar 6.6 mm in length. Offset hook 4 is laterally displaced from the center of shaft 3, due to the S-shaped structure described above, preferably by a distance A of about 5 to 8 mm and in particluar 7 mm (as shown in the front view of Fig. 3), so as to provide proper positioning of guide pin 6 when offset hook 4 is engaged against the femoral notch. In alternative embodiments, offset hook 4 is displaced at a lateral distance A of 5 mm, 6 mm, or any distance between 5 mm and 8 mm. The offset hook 4 and tubular shaft 3 are preferably formed of a chromium-nickel alloy. Shaft 3 is shown as including longitudinally spaced markings 11. Markings 11 are laser engraved in rings around shaft 3, preferably at 10 mm increments. When shaft 3 is inserted into the graft tunnel of the tibia (as discussed below), the number of exposed markings 11 provides an indication of the length of the graft required. Referring now to the side view in Fig. 2 of the shaft 3 of the drill guide 1 it can be seen how the guide pin 6 is slidably inserted in the cannula 5 of the shaft 3 and extends through said shaft 3. Referring now to Figs. 4 and 5, the method of using the drill guide of the present invention for preparing a tibia 7 and femur 8 for endosteal fixation of a ligament will now be described, it being understood that endosteal fixation of a substitute ligament or graft is well known in the art. See, e.g. Kurosaka et al., "A Biochemical Comparison of Different Surgical Techniques of Graft Fixation in Anterior Cruciate Ligament Reconstruction," Am. Jour. Sports Med., Vol. 15, No. 3, pp. 225-229, herein incorporated by reference. As is the usual practice in the art, a graft tunnel 9 is first drilled in the tibia 7 through a previously prepared incision. A cannula 12 with a silicon dam is preferably inserted in tunnel 9 to prevent excessive fluid loss. The drill guide 1 of the present invention is then inserted through cannula 12 and graft tunnel 9 until offset hook 4 engages the posterior aspect of the femoral notch 10. Advantageously, notch impingement and graft isometry can be evaluated with the drill guide in place. If the shaft 3 restricts hyperextension, a notchplasty can be performed and impingement checked again. If too much movement is observed during graft isometry testing, the offset hook 4 can be adjusted further superior or lateral in the notch 10 and isometry tested again. After testing is completed and adequate results have been attained, guide pin 6 is inserted through the cannula 5 of drill guide 1 and driven into femur 8. As shown in Fig. 5, offset hook 4 automatically aligns the positioning of guide pin 6, in femur 8 at the proper distance (preferably 7 mm) from the rear aspect of femoral notch 10. Once guide pin 6 is in place, drill guide 1 is removed and a reamer with a cannulated head (not shown) is placed over the guide pin for drilling the graft tunnel in femur 8.

Claims: An endoscopic drill guide (1) for properly locating the position to drill a tunnel for endosteal fixation of a substitute ligament or graft comprising a) a shaft (3) equipped with a cannula (5) for receiving a guide pin (6) and with longitudinally spaced markings (11) for indicating the required length of graft and b) an offset hook (4) at one end of said shaft (3) for engaging a notch in a bone and positioning said shaft (3) at a predetermined location relative to said notch. Endoscopic drill guide according to claim 1, characterized in that, the offset hook (4) is laterally offset from the shaft (3) by a distance of about 8 to 4 mm. Endoscopic drill guide according to claim 2, characterized in that, the offset hook (4) is laterally offset from said shaft (3) by a distance of about 7, 6 or 5 mm. Endoscopic drill guide according to any of the preceeding claims, characterized in that, the markings (11) are spaced in predetermined longitudinal increments of about 10 mm. Endoscopic drill guide according to any of the preceeding claims, characterized in that, it further comprises a handle (2) attached to the shaft (3). Endoscopic drill guide according to claim 5, characterized in that, the handle (2) is aluminum. Endoscopic drill guide according to any of the preceeding claims, characterized in that, the shaft (3) and the offset hook (4) are formed of a high tensile strength steel.

Inventors: SCHMIEDING REINHOLD, SCHMIEDING, REINHOLD
Applicants: ARTHREX MED INSTR GMBH, ARTHREX MEDIZINISCHE INSTRUMENTE GMBH
Application year: 1993
Main classification: A61B17
IPC codes: A61B17