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Femoral Tunnel Creation Using the Zimmer Biomet SwitchCut Femoral Aimer
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SECTION IX Principles of Tunnel Formation
45
Femoral Tunnel Creation Using the Zimmer Biomet SwitchCut Femoral Aimer Jefferey Michaelson, MD, Dragomir Mijic, DO
Many factors influence the outcome of anterior cruciate ligament (ACL) reconstruction. Technical factors including surgical method, tunnel positioning, graft type, graft tension, and fixation, as well as clinical factors including rehabilitation and patient selection, all play an important role in the overall outcome.1 The ACL consists of two bundles: the anteromedial (AM) bundle and posterolateral (PL) bundle. The AM bundle is responsible for anteroposterior stability, whereas the PL bundle is responsible for rotational stability. Overall stability and proper kinematics of the knee are controlled by the combined action and interaction of the AM and PL bundles.2 The ACL femoral footprint forms a segment of a circle on the posterior aspect of the medial surface of the lateral femoral condyle.3 The anterior border of the footprint is straight, and the posterior border is convex.3 The anterior border of the footprint is located directly behind the lateral intercondylar ridge.4 The posterior border of the footprint is located 3.5–4 mm from the posterior articular surface of the lateral femoral condyle.3 In the coronal plane the femoral origin of the ACL is low in the notch. In the sagittal plane the ACL origin is posterior in the notch.3 Using a clockface method described in the study by Heming et al., the center of the femoral footprint averaged a position of 10:49 (left knee).4 The tibial footprint of the ACL is located on the fovea, just anterior to the tibial eminence.3 Four main techniques for creation of an ACL femoral tunnel or socket are transtibial (TT), AM transportal (either with a rigid reamer or with a flexible reamer; AMP), outside-in (OI), and a modification of OI technique using retrograde drilling (RD).3,5 Historically, nonanatomical TT has been the most widely used and reproducible technique. In the TT technique, location of the femoral tunnel is determined by the orientation of the tibial tunnel.2 Over the past several years there has been a movement away from using TT technique, due to creation of a vertically oriented graft resulting in graft impingement, rotational instability with persistent pivot shift, and abnormal knee kinematics.3 The goal of anatomical ACL reconstruction is to restore the physiological function of the native ACL by replicating native dimensions, collagen orientation, graft tension, and insertion site size.6 Accurate femoral tunnel placement is one of the most important factors for obtaining good clinical results in ACL reconstruction.2 An ideal femoral tunnel is located relatively low in the intercondylar notch and is oblique in its course, providing resistance to anterior translation and rotatory moment of the tibia.3 Transtibial, AM transportal, and OI techniques are all accepted ACL reconstruction techniques. Femoral tunnels created by AMP and OI techniques have demonstrated larger femoral PL bundle coverage than tunnels created by TT technique.7 A more obliquely placed femoral tunnel created by either AMP or OI technique resists rotational forces better than a vertically placed tunnel.3 Comparison of AMP and OI techniques in multiple studies suggests that OI technique is less technically difficult and is associated with fewer complications. There are multiple technical disadvantages to the AMP technique. The AMP technique requires a high angle of knee flexion (>110 degrees) for anatomical placement of the femoral tunnel.2 Hyperflexion results in shorter femoral tunnels or sockets (<30
mm) that may compromise or limit the type of fixation used.3 Knee hyperflexion may be difficult or impossible in obese population.3 A high degree of knee flexion limits the visibility of femoral insertion during drilling.3 Without knee hyperflexion, there is a risk of damage to the posterior wall of the lateral femoral condyle (posterior wall blowout).3 Lastly, AMP technique requires that a medial portal be placed low, risking injury to the anterior horn of medial meniscus. In comparison, the OI technique has significantly fewer disadvantages, making it a better choice for both primary and revision ACL reconstruction procedures for some surgeons. Using this technique the femoral tunnel is completely housed within the lateral femoral condyle, with very low incidence of posterior wall blowout.3 With OI technique, the femoral guide is freely positioned at the anatomical center of the ACL footprint.3 It is not inhibited by the flexed position of the knee nor the anatomy of the lateral wall. Coronal obliquity of the femoral tunnel is not dependent on hyperflexion of the knee during surgery.6 In addition, the OI technique provides unobstructed visualization of the medial wall of the lateral femoral condyle throughout the case. Low and oblique placement of the ACL graft using this technique rarely requires notchoplasty.3 Addition of an RD device, such as the SwitchCut reamer (Biomet, Warsaw, Indiana), to the OI technique provides an option for minimally invasive bone-sparing femoral socket creation.8 In addition, OI RD technique allows for all epiphyseal drilling in skeletally immature patents, measurement of femoral intraosseous distance before socket creation, minimization of fluid leakage, and ability to tension graft after passage with the use of adjustable graft-loop buttons.5 In summary, although multiple techniques for ACL reconstruction are currently in use, some surgeons feel that the OI technique with use of an RD device provides the most anatomically accurate femoral socket creation and has many technical advantages with equal or better clinical outcomes when compared with other techniques. The Zimmer Biomet SwitchCut reamer is designed to allow access to any point on the medial or lateral wall of the femur. The handle and arm are designed to allow firm ergonomic grip of the aimer, which reduces the possibility of the drill missing its mark. The rigidity of the 4.5-mm drill also allows for superb tactile feel during the drilling process (Fig. 45.1). The U-shaped intra-articular guide is 8 mm in its inner diameter and 12 mm on its outer diameter, which allows for the posterior-most aspect of the guide to rest on the periosteal hinge. This will most place the center point of the drill in the direct fiber attachment of the ACL femoral footprint. The femoral incision should rest anterior to the femoral epicondyle as a simple landmark. Measurement of the femoral channel length is made from the numbers between the bullet and guide. The measurement of the channel length is then made off the drill. This tells the surgeon the channel length between the femoral cortex and the entrance to the femoral notch. Regardless of femoral implant used for fixation, it is helpful to know the distance between the socket and the cortex. After the drill has been passed into the knee, the guide is removed and the bullet is impacted down to the bone (Fig. 45.2). Before placing the drill in reverse, the blue rubber grommet is placed flush to the bullet. The drill is then pulled backward on reverse, and the depth of the socket is measured from the blue ring to the back of the bullet (Fig. 45.3). Once the drill is started in reverse, the side
CHAPTER 45 Femoral Tunnel Creation Using the Zimmer Biomet SwitchCut Femoral Aimer
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Fig. 45.3. Before placing the drill in reverse, the blue rubber grommet is placed flush to the bullet. The drill is then pulled backward on reverse, and depth of the socket is measured from the blue ring to the back of the bullet. Fig. 45.1. The U-shaped intra-articular guide in place. This puts the center point of the drill in the direct fiber attachment of the anterior cruciate ligament femoral footprint.
Fig. 45.4. After the socket has been drilled, the Jacobs chuck is removed from the SwitchCut drill and the green trochar is removed. This leaves a cannulation in which the nitinol passing wire is passed.
Fig. 45.2. After the drill has been passed into the knee, the guide is removed and the bullet is impacted down to the bone.
of the drill will engage the bone and the surgeon will feel the drill smoothly engage the bone and begin creation of the socket. After the socket has been drilled, the SwitchCut drill will remain in the femur. The Jacobs chuck is then removed from the SwitchCut drill, and the green trochar is removed (Fig. 45.4). This will leave a cannulation in which the nitinol passing wire is passed. The kite of the passer will pass into the knee and is grasped either from the arthroscopic portal or from the tibial tunnel, if this has already been drilled. Now that the wire has been passed, the tunnels are complete and the implant and graft are ready for passage. SELECTED READINGS
Gadikota HR, Sim JA, Hosseini A, Gill TJ, Li G. The relationship between femoral tunnels created by the transtibial, anteromedial portal, and outside-in techniques and the anterior cruciate ligament footprint. Am J Sp Med. 2012;40(4):882–888. Larson Andrew I, Bullock Daniel P, Pevny Tomas. Comparison of 4 femoral tunnel drilling techniques in anterior cruciate ligament reconstruction. Arthroscopy. 2012;28(7):972–979.
Lee Yong Seuk, Lee Beom Koo, Chun Dong Il. Flipping method of a retrobutton during acl reconstruction with outside-in femoral drilling using a FlipCutter. Orthopedics. 2012;35(10):861–864. Robin Brett N, Jani Sunil S, Marvil Sean C, Reid John B, Schillhammer Carl K, Lubowitz James H. Advantages and disadvantages of transtibial, anteromedial portal, and outside-in femoral tunnel drilling in single-bundle anterior cruciate ligament reconstruction: a systematic review. Arthroscopy. 2015. Matsubara Hirokazu, Okazaki Ken, Osaki Kanji, et al. Optimal entry position on the lateral femoral surface for outside-in drilling technique to restore the anatomical footprint of anterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc. 2014. Pearle AD, McAllister D, Howell SM. Rationale for strategic graft placement in anterior cruciate ligament reconstruction: I.D.E.A.L. femoral tunnel position. Am J Orthop. 2015 June;44(6):253–258. Rahr-Wagner LR. Increased risk of revision after anteromedial compared with transtibial drilling of the femoral tunnel during primary anterior cruciate ligament reconstruction. Results from the danish knee ligament reconstruction register. Arthroscopy. 2013;29(1):98–105. Sinha Skand, Naik Ananta K, Meena Durgashankar, Jain Vijay K, Arya Rajendra K. Creation of femoral tunnel by outside-in technique for acl reconstruction: an analysis. Arch Orthop Trauma Surg. 2014;134(12):1709–1716. Zavras TD, Race A, Amis AA. The effect of femoral attachment location on anterior cruciate ligament reconstruction: graft tension patterns and restoration of normal anterior-posterior laxity patterns. Knee Surg Sports Traumatol Arthrosc. 2005;13(2):92–100.
A complete reference list can be found online at ExpertConsult.com.
REFERENCES
1. Seo SS, Kim CW, Kim JG, Jin SY. Clinical results comparing transtibial technique and outside in technique in single bundle anterior cruciate ligament reconstruction. Knee Surg Relat Res. 2013;25(3):133. 2. Sohn OJ, Lee DC, Park KH, Ahn HS. Comparison of the modified transtibial technique, anteromedial portal technique and outside-in technique in ACL reconstruction. Knee Surg Relat Res. 2014;26(4):241. 3. Sinha S, Naik AK, Meena D, Jain VK, Arya RK. Creation of femoral tunnel by outside-in technique for ACL reconstruction: an analysis. Arch Orthop Trauma Surg. 2014;134(12):1709–1716. 4. Larson AI, Bullock DP, Pevny T. Comparison of 4 femoral tunnel drilling techniques in anterior cruciate ligament reconstruction. Arthroscopy. 2012;28(7):972–979. 5. Robin BN, Jani SS, Marvil SC, Reid JB, Schillhammer CK, Lubowitz JH. Advantages and disadvantages of transtibial, antero-
medial portal, and outside-in femoral tunnel drilling in single-bundle anterior cruciate ligament reconstruction: a systematic review. Arthroscopy. 2015;31(7):1412–1417. 6. Matsubara H, Okazaki K, Osaki K, et al. Optimal entry position on the lateral femoral surface for outside-in drilling technique to restore the anatomical footprint of anterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc. 2016;24(9):2758–2766. 7. Michaelson JE. Zimmer biomet switchcut reaming system for ACL reconstruction. Images with approval. Surgical Protocol PDF available at: http://www.zimmerbiomet.com/content/dam/zimmer-biomet/medical-professionals/000-surgical-techniques/sports-medicine/ switchcut-reaming-system-for-acl-reconstruction.pdf. 8. Lee YS, Lee BK, Chun DI. Flipping method of a retrobutton during acl reconstruction with outside-in femoral drilling using a flipcutter. Orthopedics. 2012;35(10):861–864.
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SECTION IX Principles of Tunnel Formation
45
Femoral Tunnel Creation Using the Zimmer Biomet SwitchCut Femoral Aimer Jefferey Michaelson, MD, Dragomir Mijic, DO
Many factors influence the outcome of anterior cruciate ligament (ACL) reconstruction. Technical factors including surgical method, tunnel positioning, graft type, graft tension, and fixation, as well as clinical factors including rehabilitation and patient selection, all play an important role in the overall outcome.1 The ACL consists of two bundles: the anteromedial (AM) bundle and posterolateral (PL) bundle. The AM bundle is responsible for anteroposterior stability, whereas the PL bundle is responsible for rotational stability. Overall stability and proper kinematics of the knee are controlled by the combined action and interaction of the AM and PL bundles.2 The ACL femoral footprint forms a segment of a circle on the posterior aspect of the medial surface of the lateral femoral condyle.3 The anterior border of the footprint is straight, and the posterior border is convex.3 The anterior border of the footprint is located directly behind the lateral intercondylar ridge.4 The posterior border of the footprint is located 3.5–4 mm from the posterior articular surface of the lateral femoral condyle.3 In the coronal plane the femoral origin of the ACL is low in the notch. In the sagittal plane the ACL origin is posterior in the notch.3 Using a clockface method described in the study by Heming et al., the center of the femoral footprint averaged a position of 10:49 (left knee).4 The tibial footprint of the ACL is located on the fovea, just anterior to the tibial eminence.3 Four main techniques for creation of an ACL femoral tunnel or socket are transtibial (TT), AM transportal (either with a rigid reamer or with a flexible reamer; AMP), outside-in (OI), and a modification of OI technique using retrograde drilling (RD).3,5 Historically, nonanatomical TT has been the most widely used and reproducible technique. In the TT technique, location of the femoral tunnel is determined by the orientation of the tibial tunnel.2 Over the past several years there has been a movement away from using TT technique, due to creation of a vertically oriented graft resulting in graft impingement, rotational instability with persistent pivot shift, and abnormal knee kinematics.3 The goal of anatomical ACL reconstruction is to restore the physiological function of the native ACL by replicating native dimensions, collagen orientation, graft tension, and insertion site size.6 Accurate femoral tunnel placement is one of the most important factors for obtaining good clinical results in ACL reconstruction.2 An ideal femoral tunnel is located relatively low in the intercondylar notch and is oblique in its course, providing resistance to anterior translation and rotatory moment of the tibia.3 Transtibial, AM transportal, and OI techniques are all accepted ACL reconstruction techniques. Femoral tunnels created by AMP and OI techniques have demonstrated larger femoral PL bundle coverage than tunnels created by TT technique.7 A more obliquely placed femoral tunnel created by either AMP or OI technique resists rotational forces better than a vertically placed tunnel.3 Comparison of AMP and OI techniques in multiple studies suggests that OI technique is less technically difficult and is associated with fewer complications. There are multiple technical disadvantages to the AMP technique. The AMP technique requires a high angle of knee flexion (>110 degrees) for anatomical placement of the femoral tunnel.2 Hyperflexion results in shorter femoral tunnels or sockets (<30
mm) that may compromise or limit the type of fixation used.3 Knee hyperflexion may be difficult or impossible in obese population.3 A high degree of knee flexion limits the visibility of femoral insertion during drilling.3 Without knee hyperflexion, there is a risk of damage to the posterior wall of the lateral femoral condyle (posterior wall blowout).3 Lastly, AMP technique requires that a medial portal be placed low, risking injury to the anterior horn of medial meniscus. In comparison, the OI technique has significantly fewer disadvantages, making it a better choice for both primary and revision ACL reconstruction procedures for some surgeons. Using this technique the femoral tunnel is completely housed within the lateral femoral condyle, with very low incidence of posterior wall blowout.3 With OI technique, the femoral guide is freely positioned at the anatomical center of the ACL footprint.3 It is not inhibited by the flexed position of the knee nor the anatomy of the lateral wall. Coronal obliquity of the femoral tunnel is not dependent on hyperflexion of the knee during surgery.6 In addition, the OI technique provides unobstructed visualization of the medial wall of the lateral femoral condyle throughout the case. Low and oblique placement of the ACL graft using this technique rarely requires notchoplasty.3 Addition of an RD device, such as the SwitchCut reamer (Biomet, Warsaw, Indiana), to the OI technique provides an option for minimally invasive bone-sparing femoral socket creation.8 In addition, OI RD technique allows for all epiphyseal drilling in skeletally immature patents, measurement of femoral intraosseous distance before socket creation, minimization of fluid leakage, and ability to tension graft after passage with the use of adjustable graft-loop buttons.5 In summary, although multiple techniques for ACL reconstruction are currently in use, some surgeons feel that the OI technique with use of an RD device provides the most anatomically accurate femoral socket creation and has many technical advantages with equal or better clinical outcomes when compared with other techniques. The Zimmer Biomet SwitchCut reamer is designed to allow access to any point on the medial or lateral wall of the femur. The handle and arm are designed to allow firm ergonomic grip of the aimer, which reduces the possibility of the drill missing its mark. The rigidity of the 4.5-mm drill also allows for superb tactile feel during the drilling process (Fig. 45.1). The U-shaped intra-articular guide is 8 mm in its inner diameter and 12 mm on its outer diameter, which allows for the posterior-most aspect of the guide to rest on the periosteal hinge. This will most place the center point of the drill in the direct fiber attachment of the ACL femoral footprint. The femoral incision should rest anterior to the femoral epicondyle as a simple landmark. Measurement of the femoral channel length is made from the numbers between the bullet and guide. The measurement of the channel length is then made off the drill. This tells the surgeon the channel length between the femoral cortex and the entrance to the femoral notch. Regardless of femoral implant used for fixation, it is helpful to know the distance between the socket and the cortex. After the drill has been passed into the knee, the guide is removed and the bullet is impacted down to the bone (Fig. 45.2). Before placing the drill in reverse, the blue rubber grommet is placed flush to the bullet. The drill is then pulled backward on reverse, and the depth of the socket is measured from the blue ring to the back of the bullet (Fig. 45.3). Once the drill is started in reverse, the side
CHAPTER 45 Femoral Tunnel Creation Using the Zimmer Biomet SwitchCut Femoral Aimer
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Fig. 45.3. Before placing the drill in reverse, the blue rubber grommet is placed flush to the bullet. The drill is then pulled backward on reverse, and depth of the socket is measured from the blue ring to the back of the bullet. Fig. 45.1. The U-shaped intra-articular guide in place. This puts the center point of the drill in the direct fiber attachment of the anterior cruciate ligament femoral footprint.
Fig. 45.4. After the socket has been drilled, the Jacobs chuck is removed from the SwitchCut drill and the green trochar is removed. This leaves a cannulation in which the nitinol passing wire is passed.
Fig. 45.2. After the drill has been passed into the knee, the guide is removed and the bullet is impacted down to the bone.
of the drill will engage the bone and the surgeon will feel the drill smoothly engage the bone and begin creation of the socket. After the socket has been drilled, the SwitchCut drill will remain in the femur. The Jacobs chuck is then removed from the SwitchCut drill, and the green trochar is removed (Fig. 45.4). This will leave a cannulation in which the nitinol passing wire is passed. The kite of the passer will pass into the knee and is grasped either from the arthroscopic portal or from the tibial tunnel, if this has already been drilled. Now that the wire has been passed, the tunnels are complete and the implant and graft are ready for passage. SELECTED READINGS
Gadikota HR, Sim JA, Hosseini A, Gill TJ, Li G. The relationship between femoral tunnels created by the transtibial, anteromedial portal, and outside-in techniques and the anterior cruciate ligament footprint. Am J Sp Med. 2012;40(4):882–888. Larson Andrew I, Bullock Daniel P, Pevny Tomas. Comparison of 4 femoral tunnel drilling techniques in anterior cruciate ligament reconstruction. Arthroscopy. 2012;28(7):972–979.
Lee Yong Seuk, Lee Beom Koo, Chun Dong Il. Flipping method of a retrobutton during acl reconstruction with outside-in femoral drilling using a FlipCutter. Orthopedics. 2012;35(10):861–864. Robin Brett N, Jani Sunil S, Marvil Sean C, Reid John B, Schillhammer Carl K, Lubowitz James H. Advantages and disadvantages of transtibial, anteromedial portal, and outside-in femoral tunnel drilling in single-bundle anterior cruciate ligament reconstruction: a systematic review. Arthroscopy. 2015. Matsubara Hirokazu, Okazaki Ken, Osaki Kanji, et al. Optimal entry position on the lateral femoral surface for outside-in drilling technique to restore the anatomical footprint of anterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc. 2014. Pearle AD, McAllister D, Howell SM. Rationale for strategic graft placement in anterior cruciate ligament reconstruction: I.D.E.A.L. femoral tunnel position. Am J Orthop. 2015 June;44(6):253–258. Rahr-Wagner LR. Increased risk of revision after anteromedial compared with transtibial drilling of the femoral tunnel during primary anterior cruciate ligament reconstruction. Results from the danish knee ligament reconstruction register. Arthroscopy. 2013;29(1):98–105. Sinha Skand, Naik Ananta K, Meena Durgashankar, Jain Vijay K, Arya Rajendra K. Creation of femoral tunnel by outside-in technique for acl reconstruction: an analysis. Arch Orthop Trauma Surg. 2014;134(12):1709–1716. Zavras TD, Race A, Amis AA. The effect of femoral attachment location on anterior cruciate ligament reconstruction: graft tension patterns and restoration of normal anterior-posterior laxity patterns. Knee Surg Sports Traumatol Arthrosc. 2005;13(2):92–100.
A complete reference list can be found online at ExpertConsult.com.
REFERENCES
1. Seo SS, Kim CW, Kim JG, Jin SY. Clinical results comparing transtibial technique and outside in technique in single bundle anterior cruciate ligament reconstruction. Knee Surg Relat Res. 2013;25(3):133. 2. Sohn OJ, Lee DC, Park KH, Ahn HS. Comparison of the modified transtibial technique, anteromedial portal technique and outside-in technique in ACL reconstruction. Knee Surg Relat Res. 2014;26(4):241. 3. Sinha S, Naik AK, Meena D, Jain VK, Arya RK. Creation of femoral tunnel by outside-in technique for ACL reconstruction: an analysis. Arch Orthop Trauma Surg. 2014;134(12):1709–1716. 4. Larson AI, Bullock DP, Pevny T. Comparison of 4 femoral tunnel drilling techniques in anterior cruciate ligament reconstruction. Arthroscopy. 2012;28(7):972–979. 5. Robin BN, Jani SS, Marvil SC, Reid JB, Schillhammer CK, Lubowitz JH. Advantages and disadvantages of transtibial, antero-
medial portal, and outside-in femoral tunnel drilling in single-bundle anterior cruciate ligament reconstruction: a systematic review. Arthroscopy. 2015;31(7):1412–1417. 6. Matsubara H, Okazaki K, Osaki K, et al. Optimal entry position on the lateral femoral surface for outside-in drilling technique to restore the anatomical footprint of anterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc. 2016;24(9):2758–2766. 7. Michaelson JE. Zimmer biomet switchcut reaming system for ACL reconstruction. Images with approval. Surgical Protocol PDF available at: http://www.zimmerbiomet.com/content/dam/zimmer-biomet/medical-professionals/000-surgical-techniques/sports-medicine/ switchcut-reaming-system-for-acl-reconstruction.pdf. 8. Lee YS, Lee BK, Chun DI. Flipping method of a retrobutton during acl reconstruction with outside-in femoral drilling using a flipcutter. Orthopedics. 2012;35(10):861–864.
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