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Medial Portal Drilling: Effects on the Femoral Tunnel Aperture Morphology During Anterior Cruciate Ligament Reconstruction
Daniel Hensler, MD; Zachary M. Working, BSEng; Kenneth D. Illingworth, MD; Eric D. Thorhauer, BS; Scott Tashman, PhD; Freddie H. Fu, MD, DSc(Hon), DPs(Hon)
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Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

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Department of Orthopaedic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Pittsburgh, PA. E-mail address for F.H. Fu: ffu@upmc.edu
Investigation performed at the Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Nov 16;93(22):2063-2071. doi: 10.2106/JBJS.J.01705
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A goal of anatomic anterior cruciate ligament (ACL) reconstruction should be to create a femoral tunnel aperture that resembles the native attachment site in terms of size and orientation. Aperture morphology varies as a function of the drill-bit diameter, the angle in the horizontal plane at which the drilled tunnel intersects the lateral notch wall (transverse drill angle), and the angle of knee flexion in the vertical plane during drilling.


A literature search was conducted to determine population-based dimensions of the femoral ACL footprint. The tunnel aperture length, width, and area associated with the use of different drill-bit diameters and transverse drill angles were calculated. The effect of the knee flexion angle on the orientation (anteroposterior and proximodistal dimension) and size of the femoral tunnel aperture relative to the native femoral insertion of the ACL were calculated with use of geometric mathematical models.


The literature search revealed an average femoral insertion site size of 8.9 mm for width, 16.3 mm for length, and 136.0 mm2 for area. The use of a 9-mm drill bit at a transverse drill angle of 40° resulted in a tunnel aperture area of 99.0 mm2 and a tunnel aperture length of 14.0 mm. Decreasing the transverse drill angle from 60° to 20° led to an increase of 152.9% in length and of 153.1% in tunnel aperture area. When a 9-mm drill bit and a transverse drill angle of 40° were used, the aperture seemed to best match the native ACL footprint when drilling was performed at a knee flexion angle of 102°; deviations from this angle in either direction resulted in increasing tunnel area mismatch compared with the baseline aperture. Increasing the knee flexion angle to 130° decreased the proximodistal dimension of the aperture by 2.78 mm and increased the anteroposterior distance by 0.65 mm, creating a mismatched area of 13.5%.


The drill-bit diameter, transverse drill angle, and knee flexion angle can all affect femoral tunnel aperture morphology in medial portal drilling during ACL reconstruction. The relationship between drilling orientation and aperture morphology is critical knowledge for surgeons performing ACL reconstruction.

Clinical Relevance: 

This study can help the surgeon to understand how drilling parameters affect the morphology of the femoral tunnel aperture during ACL reconstruction.

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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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