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Effect of Tibial Drill Angles on Bone Tunnel Aperture During Anterior Cruciate Ligament Reconstruction
Sebastian Kopf, MD1; Daniel E. Martin, MD1; Scott Tashman, PhD1; Freddie H. Fu, MD, DSc(Hon), DPs(Hon)1
1 Department of Orthopaedic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Pittsburgh, PA 15213. E-mail address for F.H. Fu: ffu@upmc.edu
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Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

Investigation performed at the Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania

Copyright ©2010 American Society for Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Apr 01;92(4):871-881. doi: 10.2106/JBJS.H.01680
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Anatomic reconstruction of the anterior cruciate ligament has received greater attention as patient outcome assessment has become increasingly sophisticated. A goal during anatomic reconstruction should be the creation of a tibial tunnel aperture that is similar in size and orientation to the native anterior cruciate ligament insertion. Aperture morphology depends primarily on three factors: (1) drill-bit diameter, (2) the angle at which the tunnel intersects the tibial plateau (drill-guide angle), and (3) the tibial tunnel orientation in the transverse plane (transverse drill angle). We evaluated the influence of the aforementioned factors on tibial bone-tunnel aperture size and orientation.


With use of various drill-bit diameters at different drill-guide angles, tunnel aperture areas were calculated on the basis of an elliptical shape. The change in tunnel aperture orientation within the transverse plane (along the tibial plateau surface) was quantified by calculating the change in anteroposterior and mediolateral lengths of the aperture.


Use of a 9-mm drill-bit at a 45° drill-guide angle created a 90-mm2 bone-tunnel aperture area. Decreasing the drill-guide angle from 65° to 30° resulted in an increase in area of 81%. An aperture oriented 45° relative to the orientation of the native insertion of the anterior cruciate ligament in the transverse plane fell short of the anatomic anteroposterior distance by 2.3 mm and exceeded the mediolateral distance by 1.4 mm on the basis of a 9-mm drill-bit at a drill-guide angle of 45°.


During anterior cruciate ligament reconstruction, the drill-bit diameter, sagittal drill angle, and transverse drill angle can all affect tibial tunnel aperture size and orientation. An improperly sized and oriented tunnel aperture may increase the risk of damaging surrounding structures. An optimal combination of these parameters should be chosen during anatomic reconstruction of the anterior cruciate ligament.

Clinical Relevance: 

It is important to consider drill-guide angle, transverse drill angle, and drill-bit diameter when recreating the native tibial insertion of the anterior cruciate ligament during anatomic reconstruction of the ligament.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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