Biomechanics Following Isolated Posterolateral Corner Reconstruction Comparing a Fibular-Based Docking Technique with a Tibia and Fibular-Based Anatomic Technique Show Either Technique is Acceptable

Journal Pre-proof Biomechanics Following Isolated Posterolateral Corner Reconstruction Comparing a Fibular-Based Docking Technique with a Tibia and Fibular-Based Anatomic Technique Show Either Technique is Acceptable Peter S. Vezeridis, MD, Ian D. Engler, MD, Matthew J. Salzler, MD, Ali Hosseini, PhD, F. Winston Gwathmey, Jr., MD, Guoan Li, PhD, Thomas J. Gill, IV, MD PII:

S0749-8063(19)31199-5

DOI:

https://doi.org/10.1016/j.arthro.2019.12.007

Reference:

YJARS 56715

To appear in:

Arthroscopy: The Journal of Arthroscopic and Related Surgery

Received Date: 28 June 2019 Revised Date:

6 December 2019

Accepted Date: 8 December 2019

Please cite this article as: Vezeridis PS, Engler ID, Salzler MJ, Hosseini A, Gwathmey FW Jr., Li G, Gill TJ IV, Biomechanics Following Isolated Posterolateral Corner Reconstruction Comparing a FibularBased Docking Technique with a Tibia and Fibular-Based Anatomic Technique Show Either Technique is Acceptable, Arthroscopy: The Journal of Arthroscopic and Related Surgery (2020), doi: https:// doi.org/10.1016/j.arthro.2019.12.007. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier on behalf of the Arthroscopy Association of North America

Biomechanics Following Isolated Posterolateral Corner Reconstruction Comparing a FibularBased Docking Technique with a Tibia and Fibular-Based Anatomic Technique Show Either Technique is Acceptable

Peter S. Vezeridisa, MD; Ian D. Englerb, MD; Matthew J. Salzlerb, MD; Ali Hosseinic, PhD; F. Winston Gwathmeyd, Jr., MD; Guoan Lic, PhD; Thomas J. Gille, IV, MD

a

Excel Orthopaedic Specialists, 200 Unicorn Park Drive, Woburn, MA 01801

b

Tufts Medical Center, Department of Orthopaedics, 800 Washington Street, Boston, MA 02111

c

Massachusetts General Hospital, Department of Orthopaedic Surgery, Harvard Medical School,

175 Cambridge Street, Suite 400, Boston, MA 02114 d

University of Virginia, Department of Orthopaedic Surgery, 200 Jeanette Lancaster Way,

Charlottesville, VA 22903 e

Boston Sports Medicine, 40 Allied Drive, Dedham, MA 02026

Corresponding author: Matthew J. Salzler, MD, Tufts Medical Center, Department of Orthopaedics, 800 Washington Street, Boston MA 02111, 617-636-7846, [email protected]

ACKOWLEDGEMENTS The authors would like to thank Sarah Davis for medical illustrations. This study was aided by grants from the Orthopaedic Research and Education Foundation (OREF) with funding provided by

the Massachusetts General Hospital Department of Orthopaedic Surgery. Fixation devices were donated by DePuy Orthopaedics, Inc. Allografts were supplied by LifeNet Health (Virginia Beach, VA). Funding sources were not involved in conduct of the research, analysis or interpretation of the data, or in writing the manuscript.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 1

ABSTRACT

2 3 4 5 6 7 8 9 10

Purpose: To analyze the biomechanical integrity of two posterolateral corner (PLC) reconstruction techniques using a sophisticated robotic biomechanical system that enables analysis of joint kinematics under dynamic external loads.

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Results: Under external torque, ER significantly increased from the intact state to the PLCdeficient state across all flexion angles. At 30° of flexion, ER was not significantly different between the intact state (19.9°) and fibular-based (18.7°, P = 0.336) and anatomic reconstructions (14.9°, P = 0.0977). At 60°, ER was not significantly different between the intact state and fibular-based reconstruction (22.4°, compared with 19.8° in intact; P = 0.152) but showed overconstraint after anatomic reconstruction (15.7°; P = 0.0315). At 90°, ER was not significantly different between the intact state and anatomic reconstruction (15.4°, compared with 19.7° in intact; P =0.386) but was with the fibular-based technique (23.5°; P = 0.0125).

Methods: Eight cadaveric human knee specimens were tested. Five N·m external torque followed by 5 N·m varus torque were dynamically applied to each specimen. The 6 degrees of freedom kinematics of the joint were measured in four states (intact, PLC-deficient, fibular-based docking, and anatomic PLC reconstructed) at 30°, 60°, and 90° of flexion. Tibial external rotation (ER) and varus rotation (VR) were compared.

Conclusion: Both a fibular-based docking technique and an anatomic technique for isolated PLC reconstruction provided appropriate constraint through most tested knee range of motion, yet the fibular-based docking technique underconstrained the knee at 90°, and the anatomic reconstruction overconstrained the knee at 60°. Biomechanically, either technique may be considered for surgical treatment of high-grade isolated PLC injuries. Clinical Relevance: Our biomechanical study utilizing clinically relevant dynamic forces on the knee shows that either a simplified fibular-based docking technique or a more complex anatomic technique may be considered for surgical treatment of high-grade isolated PLC injuries. Keywords: posterolateral corner reconstruction, knee biomechanics, kinematics, fibular-based docking technique, anatomic technique

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 33

INTRODUCTION

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The posterolateral corner (PLC) of the knee is a region with complex anatomy that

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presents management challenges. The three major structures of the PLC are the fibular collateral

36

ligament, the popliteus tendon, and the popliteofibular ligament.1-3 Over the past several years,

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increased attention has been paid to the anatomy of the PLC and to injuries in this region.4-6

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While not as common as cruciate ligament pathology, PLC injuries may result in posterolateral

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rotatory instability of the knee.7-9 Injuries of the PLC are usually seen in conjunction with anterior

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cruciate ligament (ACL) injuries or posterior cruciate ligament (PCL) injuries.7, 8, 10-12 Untreated

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PLC injuries increase forces applied to the ACL and PCL and therefore may contribute to failure

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of ACL and PCL reconstructions.13-16 Multiple studies have shown good outcomes after PLC

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reconstruction.17-21

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Several surgical methods for treatment of PLC-deficient knees have been described in the

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literature.22-26 The fibular-based reconstruction, at times called the modified Larson technique,

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reconstructs the popliteofibular ligament and the fibular collateral ligament.25, 26 Femoral graft

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fixation is achieved with a screw and spiked washer or with a tunnel and docking of the graft.27,

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28

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the use of two separate grafts to anatomically reconstruct each of the three components of the

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PLC.24

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Laprade published a more complex reconstruction technique involving the tibia and fibula and

Despite a recent improvement in our recognition and understanding of PLC injuries as

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well as in surgical methods used to treat these injuries, there is still debate regarding the

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preferred method for surgical treatment. The fibular-based docking technique is less invasive,

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less technically demanding, less expensive, and easier to learn than more complex techniques

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 55

given the fewer tunnels and grafts used.29 The anatomic technique better recreates the true

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anatomy of the knee.24

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There is need for further investigation of the in vitro biomechanical outcomes of these

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PLC reconstruction techniques.24, 30-32 In such a complex anatomic area, biomechanical study is

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valuable to our understanding of how well we restore native knee kinematics with our

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reconstructions. Prior biomechanical studies have compared the fibular-based technique with the

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anatomic technique, but these show conflicting results.27, 28, 33 One study showed over-constraint

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with the anatomic technique (Miyatake), one showed under-constraint with the fibular based

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technique, and one found comparable results (Rauh). Each of these studies primarily applied

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loads statically with a simple testing apparatus. Loading the knee dynamically as it passes

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through a range of motion much better simulates true in vivo stresses on the knee and provides

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more clinically useful data, perhaps favoring one technique. As of now there is no clear

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consensus on the best technique for PLC reconstruction.

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The purpose of the present study was to analyze the biomechanical integrity of two PLC

69

reconstruction techniques using a sophisticated robotic biomechanical system that enables

70

analysis of joint kinematics under dynamic external loads. We hypothesized that a fibular-based

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docking technique and a more complex anatomic technique for PLC reconstruction would each

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restore knee joint kinematics under simulated external rotation and varus rotation loads.

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MATERIALS AND METHODS

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Specimen Preparation

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Eight fresh frozen cadaveric human knee specimens were tested (4 left, 4 right; age range, 50 to 70 years old). Eight specimens has provided sufficient power in prior research given this

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 78

repeated measure experiment design.15, 34, 35 No patients or cadaveric specimens were excluded.

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We used a biomechanical robotic testing method that has been validated and is able to learn the

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complex motion of the knee specimen in response to external loads.34, 36-38 Specimens were thawed

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12-18 hours at room temperature prior to testing. For each specimen, the fibula was fixed to the

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tibia using a screw to preserve their anatomic relationship. The femur and tibia were cut to

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approximately 25 cm from the joint line, fixed in bone cement, and secured in aluminum

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cylinders.39 Preconditioning was performed by manually flexing and extending each knee ten

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times.

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Each specimen was installed on the testing system. This consisted of the Kawasaki UZ150

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robotic manipulator (Kawasaki Heavy Industry, Japan) and a six degrees of freedom load cell

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(JR3 Inc., Woodland, California). The robot has a high degree of repeatability with respect to

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position and orientation. The system can be used in a position control mode, which measures the

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force required to place the knee in a certain position, and in a force control mode, which measures

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knee kinematics under a given loading condition. A PhD biomechanical engineer with extensive

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robotic expertise performed the specimen testing.

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Specimen Testing

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The passive flexion path of the knee from full extension to maximal flexion was

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determined with the following method. By using the robotic testing system in the force control

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mode through 1° flexion increments, the path along which the constraint forces and moments

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within the knee joint were minimal was recorded. At each flexion increment, the specimen was

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moved through the remaining five degrees of freedom until an equilibrium position was reached.

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Translation and rotation were quantified and recorded by the testing system.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 101

After determination of the passive flexion path, the specimen was then subjected to external

102

tibial torque (5 N·m), and knee kinematics were measured at 30°, 60°, and 90° of flexion. Next,

103

varus torque (5 N·m) was applied to the knee, and knee kinematics were again measured at 30°,

104

60°, and 90° of flexion. The robot recorded the kinematic response. These same steps were

105

repeated for each of the specimens. 5 N·m is a standard load used in prior biomechanical PLC

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reconstruction studies.24, 32, 33 External rotation and varus forces were chosen given that they

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have been found to be compromised with isolated PLC deficiency, whereas anterior, posterior,

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valgus, and internal rotation forces are unchanged in that setting.24

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Following testing of the intact specimen, dissection of the posterolateral aspect of the knee

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was performed by a fellowship-trained sports surgeon. A standard lateral knee incision for PLC

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reconstruction was used. Dissection was carried down through the skin and soft tissue. The

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iliotibial band was incised in line with its fibers using a 15 blade. Dissection was carried down

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further to the posterolateral corner. Sectioning of the three major PLC structures was performed:

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the fibular collateral ligament, popliteus tendon, and popliteofibular ligament. Each structure was

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sectioned in its midportion using a 15 blade. Biomechanical testing of the specimen was performed

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using the previously described method. Each specimen was hydrated regularly during the protocol

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with normal saline to prevent dehydration of the tissues.

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Next, fibular-based docking PLC reconstruction was performed as described below. The

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knee was manually cycled ten times prior to testing. Biomechanical testing proceeded with

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application of external loading to the specimen using the previously described method. Finally,

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anatomic PLC reconstruction was performed as detailed below. Cyclic loading and biomechanical

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testing was again performed.

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Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 124 125

Fibular-based docking reconstruction PLC reconstruction was first performed using a fibular-based docking technique (Fig.

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1A).29 A tibialis anterior allograft tendon was prepared by removing any remaining muscle on the

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tendon and whip-stitching the tendon at both ends using Fiberwire suture (Arthrex, Naples,

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Florida). A 5 mm tunnel was drilled anterolateral to posteromedial in the proximal fibular head.

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This tunnel was filled with bone cement to prevent widening of the nearby graft tunnel throughout

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the course of the experiment, as has been seen in other studies.24 A second 5 mm fibular tunnel for

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the graft was drilled parallel and inferior to the cemented tunnel, 1 cm distal to the styloid through

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the widest part of the fibular head. Next a guide pin was placed in a lateral to medial direction in

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the femur from the origin of the fibular collateral ligament near the lateral epicondyle. Suture was

134

passed through the fibular tunnel and around the guide pin and secured before ranging the knee to

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ensure the optimal isometric point on the femur. The pin was moved if there was insufficient

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isometry. A 9 mm tunnel was drilled over the pin 35mm deep. The previously prepared tibialis

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anterior allograft was passed through the fibular tunnel. Each limb of the allograft was brought

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proximally, deep to the superficial layer of the iliotibial band and the anterior portion of the long

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head of the biceps femoris, and docked within the femoral tunnel with 30mm of graft in the tunnel.

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The graft was tensioned at 30° of knee flexion with a valgus force and neutral internal rotation,

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and a 9 mm interference screw was inserted between the graft limbs. Appropriate graft tension

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was noted along the knee flexion path.

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All interference screws used in the study were Milagro biocomposite interference screws (DePuy Mitek Inc., Raynham, MA).

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Anatomic reconstruction

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 147

The second technique was an anatomic PLC reconstruction (Fig. 1B).24 The graft was

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removed from the prior reconstruction, and the fibular and femoral tunnels were reused. The prior

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femoral tunnel represented the fibular collateral ligament insertion site. An Achilles tendon

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allograft was prepared by bisecting the tendon and attached calcaneus. Bone plugs were created to

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fit within a 9 x 20 mm femoral tunnel. The tendons were tubularized using suture.

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A K wire was placed anteroposterior in the tibia from an anterior point slightly distal and

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medial to Gerdy’s tubercle to a posterior point on the posterior tibial sulcus 10mm distal to the

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articular cartilage margin corresponding to the popliteus musculotendinous junction. This was

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overdrilled to establish a 9mm tibial tunnel. Next the femoral attachment site of the popliteus

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tendon was identified at the proximal half and anterior fifth of the femoral popliteal sulcus. A guide

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pin was inserted into this site in an anteromedial direction. A 9 mm diameter tunnel was drilled

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over the guide pin to a depth of 20 mm, leaving a bone bridge of approximately 9 mm between this

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tunnel and the previously drilled femoral tunnel.

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The two graft bone plugs were placed in the femoral tunnels and secured with a 7 x 23 mm

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interference screw. The graft originating from the popliteus tendon femoral insertion site was

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passed along the normal path of the popliteus through the popliteal hiatus and through the tibial

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tunnel from posterior to anterior. The graft originating from the fibular collateral ligament femoral

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insertion site was used to reconstruct the fibular collateral ligament and the popliteofibular

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ligament. This graft was passed deep to the superficial layer of the iliotibial band and the anterior

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portion of the long head of the biceps femoris. Next it was passed from anterior to posterior

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through the fibular head tunnel. The knee was cycled for one minute while placing distal traction to

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remove slack from the graft, and a 7 mm interference screw was inserted into the fibular canal with

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the knee in 60° of flexion, neutral rotation, and slight valgus. The 7 mm screw was oversized in the

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 170

5 mm tunnel. The remaining graft was pulled from posterior to anterior through the tibial tunnel.

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The two separate grafts were tightened simultaneously on the tibia by applying an anterior traction

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load to the grafts with the knee in 30° of flexion with a valgus force and neutral internal rotation.

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A 9 mm interference screw was inserted into the anterior aspect of the tibial tunnel to secure the

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grafts.

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Statistical Analysis At each flexion angle, knee movements in response to the applied loads were compared

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between the PLC-intact knee, the PLC-deficient knee, and the PLC-reconstructed knee conditions.

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Degrees of knee rotation were recorded. Statistical analysis utilized repeated-measures analysis of

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variance (ANOVA) and Student-Newman-Keuls test. Bonferroni correction was used for the

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repeated-measures ANOVA. Statistical significance was set as P < 0.05.

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RESULTS

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The means of external rotation (ER) and varus rotation (VR) of the tested knee joints in response

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to applied loads of external tibial torque (Table 1) and varus load (Table 2) are presented.

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External and varus rotation under application of external tibial torque

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Under application of external tibial torque, ER increased from 19.9° in the intact state to

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30.0° in the PLC-deficient state at 30° of knee flexion (Fig. 2A; P = <0.001). The fibular-based

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reconstruction decreased ER to 18.7°, while the anatomic reconstruction reduced it further to

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14.9° (P = <0.001and P = <0.001, respectively, compared to the PLC-deficient state). There was

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no significant difference between the intact state and the fibular-based (P = 0.336) or anatomic

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 193

(P = 0.0977) reconstructed states. At 60° of flexion, ER was 19.8° in the intact state and

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increased to 29.3° with PLC deficiency (P = <0.001). ER decreased to 22.4° after fibular-based

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reconstruction (P = 0.00118) and further decreased to 15.7° after anatomic reconstruction (P =

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<0.001), which was significantly less than the intact state (P = 0.0315). There was no significant

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difference between the intact state and the fibular-based reconstructed state (P = 0.152). At 90°

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of flexion, ER increased from 19.7° in the intact state to 26.3° with PLC deficiency (P = 0.0145).

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The fibular-based reconstruction non-significantly decreased ER to 23.5° (P = 0.196 compared

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with deficient state; P = 0.0125 compared with intact state), while the anatomic reconstruction

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significantly reduced ER to 15.4° (P = <0.001 compared with deficient state). There was no

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significant difference between the intact state and the anatomic reconstructed state (P = 0.386).

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In the external tibial torque loading condition, VR did not significantly change at

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different knee states (intact, deficient, and reconstructed) at 30° of flexion (Fig. 2B). At 60° of

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flexion, VR increased from 1.1° in the intact state to 4.0° in the deficient state (P = 0.00475) and

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was restored to the intact state following fibular-based and anatomic reconstructions (1.6° and

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1.1°, respectively; P = 0.00631 and P = 0.00770, respectively). There was no significant

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difference between the intact state and the fibular-based (P = 0.514) or anatomic (P = 0.969)

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reconstructed states. At 90° of flexion, PLC deficiency significantly increased VR from 1.8°

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(intact) to 3.1° (deficient) (P = 0.0303). At this flexion angle, fibular-based reconstruction non-

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significantly reduced VR (2.8°, P = 0.421), whereas anatomic reconstruction had a significant

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reduction (1.8°, P = 0.0414). There was no significant difference, though, between the intact

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state and the fibular-based (P = 0.175) or anatomic (P = 0.899) reconstructed states.

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External and varus rotation under application of varus load

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 216

Under application of a varus load, ER significantly increased from 11.2° in the intact

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state to 20.5° in the PLC-deficient state at 30° of knee flexion (Fig. 3A; P = 0.00260). ER was

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restored after PLC reconstruction with 11.5° of ER in the fibular-based (P = 0.00126 vs.

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deficient state) and 7.7° in the anatomic (P = <0.001) reconstructions. There was no significant

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difference between the intact state and the fibular-based (P = 0.128) or anatomic (P = 0.645)

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reconstructed states. Similarly, at 60° of knee flexion, ER was significantly increased from 11.9°

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in the intact state to 22.0° in the deficient state (P = 0.00146) and was restored to 16.6° in the

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fibular-based reconstruction (P = 0.0387 vs. deficient state) and 9.9° in the anatomic

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reconstruction (P = <0.001). There was no significant difference between the intact state and the

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fibular-based (P = 0.0631) or anatomic (P = 0.897) reconstructed states. PLC deficiency

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increased ER at 90° of flexion (14.9° to 20.5°), even though it was not significantly different (P

227

= 0.0646). After PLC reconstruction, ER was reduced to 18.9° (P = 0.502 vs. deficient state) and

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10.7° (P = 0.00223) in the fibular–based and anatomic reconstructions, respectively. There was a

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significant difference between the intact state and the fibular-based reconstructed state (P =

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0.0127) but not the anatomic reconstructed state (P = 0.400).

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In the varus loading condition, VR increased from 0.4° in the intact knee to 5.0° with

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PLC deficiency at 30° of knee flexion (Fig. 3B; P = 0.0182). Fibular-based reconstruction

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decreased VR to 0.4° (P = 0.0296), and anatomic reconstruction decreased VR to 1.6° (P =

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0.0351). There was no significant difference between the intact state and the fibular-based (P =

235

0.988) or anatomic (P = 0.535) reconstructed states. At 60° of flexion, VR increased from 2.5° in

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the intact state to 6.1° in the PLC-deficient state (P = 0.00279) and subsequently decreased to

237

1.8° after fibular-based reconstruction (P = 0.00193) and to 1.6° following anatomic

238

reconstruction (P = 0.00241). There was no significant difference between the intact state and

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 239

the fibular-based (P = 0.648) or anatomic (P = 0.545) reconstructed states. Finally, at 90° of knee

240

flexion, VR was 3.2° in the intact knee, 3.5° in the PLC-deficient knee (P = 0.605), 2.7°

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following fibular-based reconstruction (P = 0.530 vs. deficient state), and 1.8° following

242

anatomic reconstruction (P = 0.180 vs. deficient state). There was no significant difference

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between the intact state and the fibular-based (P = 0.632) or anatomic (P = 0.868) reconstructed

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states.

245 246 247

DISCUSSION Our results partially support our hypothesis that both techniques of isolated PLC

248

reconstruction restore knee joint kinematics under simulated muscle loads. Both techniques

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appropriately reestablished knee kinematics in our tested conditions with the following

250

exceptions. Under application of external torque at 60° of knee flexion, the anatomic

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reconstruction decreased ER significantly more than the intact specimen and the fibular-based

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PLC reconstruction. This indicates that the anatomic technique overconstrained ER at 60° of

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knee flexion in response to external torque. Overconstraint in the anatomic reconstruction has

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been seen in past studies.33, 40 Under an external torque load at 90° of knee flexion, the anatomic

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reconstruction significantly reduced the PLC-deficient ER and VR, while the fibular-based

256

reconstruction did not. This shows underconstraint of the fibular-based reconstruction at 90°.

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Both techniques have benefits and drawbacks with regards to restoration of knee joint

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rotation. The restoration of ER and VR at 30° by both techniques is particularly significant, as

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prior studies have established the PLC as contributing the largest amount of ER41 and VR9

260

constraint at 30°. Sixty degrees is a more common knee flexion angle in the functional use of the

261

knee in most athletics compared to 90°, making it more relevant to the patient population and

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 262

activities often associated with PLC injuries. Therefore the anatomic reconstruction’s

263

overconstraint at 60° could be more problematic than the fibular-based technique’s

264

underconstraint at 90°.

265

Under application of varus loading, both techniques restored normal kinematics at 30°

266

and 60° of knee flexion. At 90° of knee flexion, the PLC-deficient state was not significantly

267

different from the intact state, rendering calculations of a significant decrease in rotation between

268

the deficient state and the reconstructed states unhelpful.

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As expected, PLC-deficient knees had significantly increased ER and VR under external

270

and varus torque compared to intact knees at nearly all tested knee flexion angles. The PLC is

271

vital to constraining the knee against excess external and varus rotation.

272

We found three similar biomechanical studies that compare variations of the fibular-

273

based and anatomic techniques in the isolated PLC-deficient knee. Nau et al. determined that

274

anatomic reconstruction was comparable to the modified Larson technique in static testing and

275

comparable to the intact knee but caused excess tibial internal rotation throughout dynamic knee

276

range of motion.33 This finding suggests that the anatomic reconstruction may overconstrain the

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knee in tibial rotation, perhaps by reconstructing the dynamic popliteus tendon with a static

278

ligament. In contrast, Miyatake et al. concluded that a 4-strand anatomic reconstruction more

279

closely recreated anatomic rotational knee constraint with ER and posterior translation loads

280

compared to the modified Larson technique without a difference in varus constraint.28 They

281

proposed that their laxity-matching technique, in which each graft was tensioned at different

282

tensions in different positions based on the knee-specific laxity present, may have helped avoid

283

overconstraint. They advocated for use of the anatomic technique over the modified Larson.

284

Rauh et al. used a screw and spiked washer for femoral fixation of the fibular-based technique

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 285

and found that both techniques were effective in restoration of knee joint rotation.27 The authors

286

tested more limited conditions, including ER laxity in response only to ER force, and varus

287

laxity only in response to varus force, in solely 30° and 90° of flexion.

288

Our study found overlapping results with each of these studies. Our largely similar results

289

between techniques is concurrent with many of Rauh et al.’s findings.27 Yet we also found

290

evidence of overconstraint with the anatomic reconstruction, as did Nau et al.,33 and

291

underconstraint with the fibular-based reconstruction, as observed by Miyatake et al.28

292

Differences in methodology prevent close comparisons of exact degrees of laxity between this

293

study and these studies.

294

Both overconstraint and underconstraint can be concerning following ligament

295

reconstruction. Underconstraint may lead to knee instability and thus graft failure.

296

Overconstraint has been shown to contribute to knee stiffness and osteoarthritis.42 These topics

297

warrant further investigation. As a biomechanical study, our findings reflect constraint at time

298

zero. Some surgeons may err on the side of overconstraint initially, factoring in possible graft

299

relaxation. Particularly in the setting of revision reconstruction, preference may be given to the

300

anatomic technique given its tendency towards increased constraint.

301

Our methods aimed to overcome an important limitation of the existing literature. Each of

302

the aforementioned studies primarily exerted the external load in a static fashion, often with

303

weights and pulleys, once the knee was flexed to the desired degree.27, 28, 33 Our robot, on the

304

other hand, exerts a consistent torque throughout the arc of motion, capturing the knee

305

kinematics along the way. This is a more dynamic force that can better simulate the functional

306

movements responsible for ligamentous knee injury and inform the true level of constraint in a

307

reconstruction. Furthermore, our fibular-based technique docked the graft within the femur

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 308

instead of using cortical fixation with a screw and spiked washer, which has implications for

309

tensioning the graft and potentially for graft healing in vivo.

310

Though not a direct comparison of two techniques, Laprade demonstrated the

311

biomechanical validity of the anatomic technique, showing no difference between intact and

312

reconstructed states.24 He subsequently demonstrated good clinical outcomes with the

313

technique.43 To our knowledge, a comparison of clinical outcomes between these techniques has

314

not been performed.

315

Unfortunately it is challenging to elucidate the clinical significance of the significant

316

differences in our data and similar biomechanical studies. There is no clear correlation between

317

laxity in cadaveric specimens and in vivo biomechanics and outcomes given the inherent

318

differences between the subjects. Further research may clarify this relationship. The goal with

319

our robotic testing apparatus was to more closely simulate in vivo biomechanics than prior

320

biomechanical studies through the application of dynamic force with accurate analysis of six

321

degrees of freedom.

322 323

Limitations

324

There are several limitations to the present investigation. First, this study did not

325

investigate the effect of concomitant PCL or ACL injury or reconstruction in an effort to narrow

326

our scope and minimize variables. Though PLC and cruciate ligament injuries often coexist, this

327

investigation was designed to clarify the effect of isolated PLC reconstruction without the

328

variable of cruciate ligament injury. Combined PLC and cruciate ligament injuries have been

329

examined in other studies.32, 40, 44, 45 The present investigation has the inherent limitations of a

330

cadaveric study, such as older age of specimens and not being able to evaluate reconstruction

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 331

methods in vivo or past time zero. Therefore, this study did not address graft relaxation over time

332

or especially the in vivo knee kinematics of patients after PLC reconstruction. Our knowledge of

333

the relevance of biomechanical constraint to clinical outcomes is limited. Another limitation is

334

that the same sequence of graft testing was used with each specimen instead of randomizing the

335

order of reconstruction tested. If the soft tissues of the knee experienced creep over time, they

336

may have contributed variably to the stability of the knee during the testing of each method of

337

reconstruction. Finally the sample size of eight specimens could preclude adequate power.

338

Though this is a limitation, eight specimens are commonly used in biomechanical studies of the

339

knee.15, 34, 35 Nearly all of our comparisons between the intact and PLC-deficient states reached

340

statistical significance, suggesting that the study was adequately powered.

341 342 343

CONCLUSIONS Both a fibular-based docking technique and an anatomic technique for isolated PLC

344

reconstruction provided appropriate constraint through most tested knee range of motion, yet the

345

fibular-based docking technique underconstrained the knee at 90°, and the anatomic

346

reconstruction overconstrained the knee at 60°. Biomechanically, either technique may be

347

considered for surgical treatment of high-grade isolated PLC injuries.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 348

FIGURE LEGENDS

349 350

Figure 1. Diagrams of two posterolateral corner (PLC) reconstruction techniques. (A) Fibular-

351

based docking PLC reconstruction. The anterior limb reconstructs the fibular collateral ligament.

352

The posterior limb reconstructs the popliteofibular ligament. (B) Anatomic tibial-fibular-based

353

PLC reconstruction. The anterior limb reconstructs the fibular collateral ligament. The

354

tibiofemoral limb reconstructs the popliteus tendon. The tibiofibular limb reconstructs the

355

popliteofibular ligament.

356 357

Figure 2. Mean biomechanics of the knee joint under application of external torque with intact,

358

PLC-deficient, and PLC-reconstructed conditions in 30º, 60º, and 90º knee flexion angles. (A)

359

External rotation. (B) Varus rotation. Error bars represent standard deviation. Statistically

360

significant differences are denoted by *.

361

Figure 3. Mean kinematics of the knee joint under application of varus load with intact, PLC-

362

deficient, and PLC-reconstructed conditions in 30º, 60º, and 90º knee flexion angles. (A)

363

External rotation. (B) Varus rotation. Error bars represent standard deviation. Statistically

364

significant differences are denoted by *.

365

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 366 367 368

Table 1. External and varus rotation of the tibia under application of external tibial torque. SD = standard deviation. External Rotation Intact PLC-deficient Docking fibular reconstruction Anatomic reconstruction Varus Rotation Intact PLC-deficient Docking fibular reconstruction Anatomic reconstruction

369

30° knee flexion Mean (SD) 19.9 (3.7) 30.0 (2.9) 18.7 (3.9)

60° knee flexion Mean (SD) 19.8 (3.7) 29.3 (4.4) 22.4 (4.4)

90° knee flexion Mean (SD) 19.7 (4.9) 26.3 (3.1) 23.5 (3.9)

14.9 (4.5)

15.7 (4.1)

15.4 (4.0)

-0.60 (0.27) 3.0 (1.3) -0.24 (0.39)

1.1 (1.4) 4.0 (3.8) 1.6 (2.6)

1.8 (2.0) 3.1 (2.9) 2.8 (2.8)

0.55 (0.31)

1.1 (2.5)

1.8 (2.5)

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 370 371 372

Table 2. External and varus rotation of the tibia under application of varus load. SD = standard deviation. External Rotation Intact PLC-deficient Docking fibular reconstruction Anatomic reconstruction Varus Rotation Intact PLC-deficient Docking fibular reconstruction Anatomic reconstruction

373

30° knee flexion Mean (SD) 11.2 (6.8) 20.5 (7.5) 11.5 (3.9)

60° knee flexion Mean (SD) 11.9 (6.6) 22.0 (6.5) 16.6 (3.7)

90° knee flexion Mean (SD) 14.9 (7.2) 20.5 (6.4) 18.9 (4.5)

7.7 (4.3)

9.9 (3.4)

10.7 (4.9)

0.4 (1.8) 5.0 (4.1) 0.4 (1.3)

2.5 (2.1) 6.1 (4.2) 1.8 (2.5)

3.2 (2.2) 3.5 (2.9) 2.7 (2.8)

1.6 (2.4)

1.6 (2.4)

1.8 (2.5)

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 374

REFERENCES

375

1.

Maynard MJ, Deng X, Wickiewicz TL, Warren RF. The popliteofibular ligament.

376

Rediscovery of a key element in posterolateral stability. Am J Sports Med. 1996;24:311-

377

316.

378

2.

Veltri DM, Deng XH, Torzilli PA, Maynard MJ, Warren RF. The role of the

379

popliteofibular ligament in stability of the human knee. A biomechanical study. Am J

380

Sports Med. 1996;24:19-27.

381

3.

Veltri DM, Deng XH, Torzilli PA, Warren RF, Maynard MJ. The role of the cruciate and

382

posterolateral ligaments in stability of the knee. A biomechanical study. Am J Sports

383

Med. 1995;23:436-443.

384

4.

385 386

anatomic study. Am J Sports Med. 1997;25:439-443. 5.

387 388

6.

Terry GC, LaPrade RF. The posterolateral aspect of the knee. Anatomy and surgical approach. Am J Sports Med. 1996;24:732-739.

7.

391 392

Seebacher JR, Inglis AE, Marshall JL, Warren RF. The structure of the posterolateral aspect of the knee. J Bone Joint Surg Am. 1982;64:536-541.

389 390

LaPrade RF, Hamilton CD. The fibular collateral ligament-biceps femoris bursa. An

Baker CL, Jr., Norwood LA, Hughston JC. Acute posterolateral rotatory instability of the knee. J Bone Joint Surg Am. 1983;65:614-618.

8.

Fleming RE, Jr., Blatz DJ, McCarroll JR. Posterior problems in the knee. Posterior

393

cruciate insufficiency and posterolateral rotatory insufficiency. Am J Sports Med.

394

1981;9:107-113.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 395

9.

Gollehon DL, Torzilli PA, Warren RF. The role of the posterolateral and cruciate

396

ligaments in the stability of the human knee. A biomechanical study. J Bone Joint Surg

397

Am. 1987;69:233-242.

398

10.

399 400

Hughston JC, Jacobson KE. Chronic posterolateral rotatory instability of the knee. J Bone Joint Surg Am. 1985;67:351-359.

11.

Noyes FR, Barber-Westin SD. Surgical restoration to treat chronic deficiency of the

401

posterolateral complex and cruciate ligaments of the knee joint. Am J Sports Med.

402

1996;24:415-426.

403

12.

O'Brien SJ, Warren RF, Pavlov H, Panariello R, Wickiewicz TL. Reconstruction of the

404

chronically insufficient anterior cruciate ligament with the central third of the patellar

405

ligament. J Bone Joint Surg Am. 1991;73:278-286.

406

13.

Markolf KL, Graves BR, Sigward SM, Jackson SR, McAllister DR. Effects of

407

posterolateral reconstructions on external tibial rotation and forces in a posterior cruciate

408

ligament graft. J Bone Joint Surg Am. 2007;89:2351-2358.

409

14.

Harner CD, Vogrin TM, Hoher J, Ma CB, Woo SL. Biomechanical analysis of a posterior

410

cruciate ligament reconstruction. Deficiency of the posterolateral structures as a cause of

411

graft failure. Am J Sports Med. 2000;28:32-39.

412

15.

LaPrade RF, Muench C, Wentorf F, Lewis JL. The effect of injury to the posterolateral

413

structures of the knee on force in a posterior cruciate ligament graft: a biomechanical

414

study. Am J Sports Med. 2002;30:233-238.

415

16.

LaPrade RF, Resig S, Wentorf F, Lewis JL. The effects of grade III posterolateral knee

416

complex injuries on anterior cruciate ligament graft force. A biomechanical analysis. Am

417

J Sports Med. 1999;27:469-475.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 418

17.

Geeslin AG, LaPrade RF. Outcomes of treatment of acute grade-III isolated and

419

combined posterolateral knee injuries: a prospective case series and surgical technique. J

420

Bone Joint Surg Am. 2011;93:1672-1683.

421

18.

Geeslin AG, Moulton SG, LaPrade RF. A systematic review of the outcomes of

422

posterolateral corner knee injuries, part 1: surgical treatment of acute injuries. Am J

423

Sports Med. 2016;44:1336-1342.

424

19.

Moulton SG, Geeslin AG, LaPrade RFJTAjosm. A systematic review of the outcomes of

425

posterolateral corner knee injuries, part 2: surgical treatment of chronic injuries.

426

2016;44:1616-1623.

427

20.

Yoon KH, Lee JH, Bae DK, Song SJ, Chung KY, Park YW. Comparison of clinical

428

results of anatomic posterolateral corner reconstruction for posterolateral rotatory

429

instability of the knee with or without popliteal tendon reconstruction. Am J Sports Med.

430

2011;39:2421-2428.

431

21.

Yoon KH, Lee SH, Park SY, Park SE, Tak DH. Comparison of anatomic posterolateral

432

knee reconstruction using 2 different popliteofibular ligament techniques. Am J Sports

433

Med. 2016;44:916-921.

434

22.

435 436

Arciero RA. Anatomic posterolateral corner knee reconstruction. Arthroscopy. 2005;21:1147.

23.

Jakobsen BW, Lund B, Christiansen SE, Lind MC. Anatomic reconstruction of the

437

posterolateral corner of the knee: a case series with isolated reconstructions in 27

438

patients. Arthroscopy. 2010;26:918-925.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 439

24.

LaPrade RF, Johansen S, Wentorf FA, Engebretsen L, Esterberg JL, Tso A. An analysis

440

of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and

441

development of a surgical technique. Am J Sports Med. 2004;32:1405-1414.

442

25.

Cooley VJ, Harrington RM, Larson RV. Effect of lateral ligament reconstruction on

443

intra-articular posterior cruciate ligament graft force and knee motion. University of

444

Washington Research Report. 1996:37-41.

445

26.

Larson RV, Sidles JA, Beals CT. Isometry of lateral collateral and popliteofibular

446

ligaments and a technique for reconstruction. University of Washington Research Report.

447

1996:42-44.

448

27.

Rauh PB, Clancy WG, Jr., Jasper LE, Curl LA, Belkoff S, Moorman CT, 3rd.

449

Biomechanical evaluation of two reconstruction techniques for posterolateral instability

450

of the knee. J Bone Joint Surg Br. 2010;92:1460-1465.

451

28.

Miyatake S, Kondo E, Tsai TY, et al. Biomechanical comparisons between 4-strand and

452

modified Larson 2-strand procedures for reconstruction of the posterolateral corner of the

453

knee. Am J Sports Med. 2011;39:1462-1469.

454

29.

Larson RV. Isometry of the lateral collateral and popliteofibular ligaments and techniques

455

for reconstruction using a free semitendinosus tendon graft. Oper Tech Sports Med.

456

2001;9:84-90.

457

30.

458 459

Wascher DC, Grauer JD, Markoff KL. Biceps tendon tenodesis for posterolateral instability of the knee. An in vitro study. Am J Sports Med. 1993;21:400-406.

31.

Chun YM, Kim SJ, Kim HS. Evaluation of the mechanical properties of posterolateral

460

structures and supporting posterolateral instability of the knee. J Orthop Res.

461

2008;26:1371-1376.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 462

32.

Apsingi S, Nguyen T, Bull AM, Unwin A, Deehan DJ, Amis AA. A comparison of

463

modified Larson and 'anatomic' posterolateral corner reconstructions in knees with

464

combined PCL and posterolateral corner deficiency. Knee Surg Sports Traumatol

465

Arthrosc. 2009;17:305-312.

466

33.

Nau T, Chevalier Y, Hagemeister N, Deguise JA, Duval N. Comparison of 2 surgical

467

techniques of posterolateral corner reconstruction of the knee. Am J Sports Med.

468

2005;33:1838-1845.

469

34.

Li G, Gill TJ, DeFrate LE, Zayontz S, Glatt V, Zarins B. Biomechanical consequences of

470

PCL deficiency in the knee under simulated muscle loads--an in vitro experimental study.

471

J Orthop Res. 2002;20:887-892.

472

35.

Gelber PE, Erquicia JI, Sosa G, et al. Femoral tunnel drilling angles for the posterolateral

473

corner in multiligamentary knee reconstructions: computed tomography evaluation in a

474

cadaveric model. Arthroscopy. 2013;29:257-265.

475

36.

Li G, Rudy TW, Sakane M, Kanamori A, Ma CB, Woo SL. The importance of

476

quadriceps and hamstring muscle loading on knee kinematics and in-situ forces in the

477

ACL. J Biomech. 1999;32:395-400.

478

37.

Gadikota HR, Seon JK, Kozanek M, et al. Biomechanical comparison of single-tunnel-

479

double-bundle and single-bundle anterior cruciate ligament reconstructions. Am J Sports

480

Med. 2009;37:962-969.

481

38.

Yoo JD, Papannagari R, Park SE, DeFrate LE, Gill TJ, Li G. The effect of anterior

482

cruciate ligament reconstruction on knee joint kinematics under simulated muscle loads.

483

Am J Sports Med. 2005;33:240-246.

Biomechanics of Fibular-Based Docking and Anatomic Techniques for Posterolateral Corner Reconstruction 484

39.

Li G, Rudy TW, Allen C, Sakane M, Woo SL. Effect of combined axial compressive and

485

anterior tibial loads on in situ forces in the anterior cruciate ligament: a porcine study. J

486

Orthop Res. 1998;16:122-127.

487

40.

Markolf KL, Graves BR, Sigward SM, Jackson SR, McAllister DR. How well do

488

anatomical reconstructions of the posterolateral corner restore varus stability to the

489

posterior cruciate ligament-reconstructed knee? Am J Sports Med. 2007;35:1117-1122.

490

41.

Grood ES, Stowers SF, Noyes FR. Limits of movement in the human knee. Effect of

491

sectioning the posterior cruciate ligament and posterolateral structures. J Bone Joint Surg

492

Am. 1988;70:88-97.

493

42.

Schon JM, Moatshe G, Brady AW, et al. Anatomic anterolateral ligament reconstruction

494

of the knee leads to overconstraint at any fixation angle. Am J Sports Med. 2016;44:2546-

495

2556.

496

43.

497 498

LaPrade RF, Johansen S, Agel J, Risberg MA, Moksnes H, Engebretsen L. Outcomes of an anatomic posterolateral knee reconstruction. J Bone Joint Surg Am. 2010;92:16-22.

44.

Nau T, Chevalier Y, Hagemeister N, Duval N, deGuise JA. 3D kinematic in-vitro

499

comparison of posterolateral corner reconstruction techniques in a combined injury

500

model. Knee Surg Sports Traumatol Arthrosc. 2005;13:572-580.

501

45.

Sekiya JK, Haemmerle MJ, Stabile KJ, Vogrin TM, Harner CD. Biomechanical analysis

502

of a combined double-bundle posterior cruciate ligament and posterolateral corner

503

reconstruction. Am J Sports Med. 2005;33:360-369.

504