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TriLink: Anatomic Double-Bundle Anterior Cruciate LigamentReconstruction

Sam K. Yasen, M.B.B.S., B.Sc.(Hons), M.R.C.S.,James S. Logan, M.B.B.S., B.Sc.(Hons), M.R.C.S.,James O. Smith, B.M., B.Sc.(Hons), M.R.C.S.,

Tamara Nancoo, M.B.B.Chir., P.G.Dip.(SEM), F.R.C.S.(Tr&Orth),Mike J. Risebury, M.A.(Hons), M.B.B.S.(Hons), F.R.C.S.(Tr&Orth), and

Adrian J. Wilson, M.B.B.S., B.Sc.(Hons), F.R.C.S.(Tr&Orth)

Abstract: Cadaveric and clinical biomechanical studies show improved kinematic restoration using double-bundleanterior cruciate ligament (ACL) reconstruction techniques. These have been criticized in the past for being technicallychallenging. We present a novel 3-socket approach for anatomic “all-inside” double-bundle reconstruction using a singlehamstring tendon fashioned to create a trifurcate graft: the TriLink technique. The semitendinosus alone is harvested,quadrupled, and attached to 3 suspensory fixation devices in a Y-shaped configuration, creating a 4-stranded tibial limband 2 double-stranded femoral limbs. A medial viewing/lateral working arthroscopic approach is adopted using specifi-cally designed instrumentation. Anatomic placement of the 2 femoral tunnels is performed by a validated directmeasurement technique. A single mid-bundle position is used on the tibia. Both femoral and tibial sockets are created ina retrograde manner using outside-to-in drilling. This is a simplified operative technique for anatomic double-bundle ACLreconstruction that maximizes bone preservation. The TriLink construct replicates the 2 bundles of the ACL, conferringnative functional anisometry and improving femoral footprint coverage while avoiding the complexities and pitfalls ofdoubleetibial tunnel techniques. Preservation of the gracilis reduces the morbidity of hamstring harvest and allows greaterflexibility in graft choice in cases requiring multiligament reconstruction.

he goal of anterior cruciate ligament (ACL) re-

Tconstruction is to stabilize the injured joint withoutrestricting a normal physiological range of motion.Traditional reconstruction techniques are generallysuccessful when measured in the short-term; however,poor long-term outcomes have been reported, with anincreased incidence of early-onset degenerative arthrosisin the ACL-injured knee.1,2 ACL reconstruction has not

From Hampshire Hospitals NHS Foundation Trust, Basingstoke, England.The authors report the following potential conflict of interest or source ofnding: A.J.W. is a consultant for Arthrex and receives an honorarium foris time but did not bill any time for this project. A.J.W. receives money forresenting at meetings when there is relevance to his projects with Arthrex.ravel costs are paid directly and not to A.J.W.Received June 7, 2013; accepted August 8, 2013.Address correspondence to Sam K. Yasen, M.B.B.S., B.Sc.(Hons), M.R.C.S.,epartment of Orthopaedics, Hampshire Hospitals NHS Foundation Trust,ldermaston Road, Basingstoke, Hampshire, RG24 9NA, England. E-mail:myasen@doctors.org.uk� 2014 by the Arthroscopy Association of North America2212-6287/13378/$36.00http://dx.doi.org/10.1016/j.eats.2013.08.004

Arthroscopy Techniques, Vol 3, No 1

been shown to influence this irrespective of graft choiceor technique used.3,4 This has been attributed to variousfactors, including concomitant damage sustained duringthe original injury5; however, inadequate restoration ofnormal knee kinematics is possibly the most importantcause.6,7

Conventional techniques, such as transtibial drilling ofthe femoral tunnel, tend to put the graft in a nonan-atomic, relatively vertical position, contributing topersistent rotational laxity postoperatively.8 Clinicalkinematic evaluation corroborates this in the dynamicstate.7,9 This has led to a move toward “anatomic”reconstruction, focusing on locating the graft within thenative ACL footprint, as championed by Fu and Karls-son.10 Lateral placement of the femoral tunnel towarda mid-bundle position has been shown to be biome-chanically superior to traditional high and deep posi-tions, such as those achieved with the “over-the-top”guide.11 Despite this, even with mid-bundle positioning,some rotational laxity can still persist.12,13 Consequently,there is continued interest in double-bundle recon-struction. Although long-term clinical outcomes are not

(February), 2014: pp e13-e20 e13

Table 1. Summary of Technical Steps in TriLink ACLReconstruction

Procedure Stage Details

Patient setup Supine, thigh tourniquetKnee at 90�, side support, footrest

Arthroscopicapproach

Low AL portal, central AM portalMedial viewing/lateral working (TransLateral)approach for femoral work

Graft harvestand preparation

Single semitendinosus tendon harvestTendon looped through 2 TightRopes and suturedend to end, then attached to third TightRope toform Y-shaped graft

Femoralpreparation

Double bundle: 2 sockets at AM and PL positionsSockets created by outside-to-in drilling withFlipCutter device (typically 5.5 to 6 mm)

Tibial preparation Single-bundle: socket created in mid-bundleposition

Use of FlipCutter (typically 8 to 8.5 mm)Graft deployment Two FiberSticks passed through FlipCutter guide

holes into femoral sockets and single TigerStickinto tibial socket as lead sutures

Sutures collectively grasped through AM portaland attached to 3 limbs of TriLink graft

Graft pulled into knee and limbs docked intosockets

Graft fixationand tensioning

Tibial limb drawn into socket to depth of 20 mm(pre-marked)

AM bundle tensioned in extension, then PLbundle in extension

AM bundle re-tensioned at 30� to 40� of flexionKnee cycled, followed by re-tensioning of alllimbs

e14 S. K. YASEN ET AL.

yet available, robust biomechanical studies and em-erging clinical evidence support the superiority ofdouble-bundle reconstruction techniques.14-20

Double-bundle ACL reconstruction presents a techni-cal challenge to the surgeon. Numerous 4-tunnel tech-niques,21-23 aswell as variationsusing3 tunnels,24-26havebeen described. These have all been criticized because oftheir associated increased operative complication ratesand higher patient morbidity rates.27,28 Specifically,problems with fracture of the lateral femoral condyle ortunnel communication have been cited.29 In addition,graft choice and fixation remain widely debated. Graftsthat have been used include semitendinosus and gracilistendons, a split boneepatellar tendonebone graft,22

a combination of gracilis and boneepatellar tendonebone,23 and tibialis anterior or tibialis posterior allograft.21

All have potential drawbacks, such as the small size of thegracilis graft, the morbidity of patellar tendon harvest, orthe cost of allograft.We present a novel approach for anatomic double-

bundle ACL reconstruction using a single semitendinosusgraft, which we term the TriLink technique. This isa simplified “all-inside” operative procedure with 2anatomically placed femoral tunnels and a single mid-bundle tibial tunnel. The tendon is quadrupled andattached to 3 adjustable suspensory fixation devices ina Y-shaped trifurcate configuration, creating a 4-strandedtibial limb and 2 more slender double-stranded femorallimbs. The technique was developed and refined usingcadaveric specimens, and the senior author has nowstarted using this in the clinical setting. There have beenno early operative complications.

TechniqueThe surgical approach is based on the TransLateral ACL

reconstruction technique previously published by ourgroup30 (Video 1). A summary of the pertinent steps ispresented in Table 1. A medial viewing/lateral workingarthroscopic philosophy is adopted for femoral prepara-tion, using instrumentation specifically designed by thesenior author. These instruments are able to navigatearound the lateral femoral condyle without impingingmedially against the patellar tendon. They include anOpes radiofrequency (RF) probe (Arthrex, Naples, FL) forsoft-tissue debridement, a modified curette (Arthrex),a curved marking/measuring device (Arthrex) (Fig 1),and an anatomic aiming arm for a retrograde drill(Arthrex). The senior author uses the FlipCutter(Arthrex) for this purpose. Recently, a calibrated versionof the RF probe, the Caliblator (Arthrex), has also beenintroduced.

Patient Positioning and Surgical ApproachThe patient is positioned supine with the knee flexed

to 90�. There is no requirement for knee hyperflexionthroughout the procedure. A side support and footrest

are used. A thigh tourniquet is used throughout. Amodified lateral portal (Fig 2) is created, which is slightlylower and more medial than the traditional high ante-rolateral (AL) portal position. A 30� inclined arthroscopeis inserted through the AL portal. The anteromedial(AM) portal is established under direct vision. Routinearthroscopic assessment of the knee is performed, andappropriate surgery is undertaken to address any chon-dral or meniscal pathology.

Graft Harvest and PreparationThe semitendinosus alone is harvested in the standard

fashion using a curved incision over the pes anserinus.Two TightRope (Arthrex) tensionable suspensory fixa-tion devices are placed along the tendon. The tendonends are sutured with a nonabsorbable highetensilestrength suture to form a continuous loop (Fig 3A). Thedouble-stranded graft is then effectively positioned withthe knot centrally and the 2 loaded TightRopes at eachend (Fig 3B). A third TightRope is passed, placed at themidpoint of the looped graft, and secured at 1 end ofthe preparation table. The other 2 TightRopes aresecured at the other end of the table to form a Y-shapedtrifurcate graftdthe TriLink. Further nonabsorbablehighetensile strength sutures are used to fix the posi-tions of the TightRopes (Fig 3C). The graft is tensioned

Fig 1. TransLateral instrumentation. (A) Aiming jig for retrograde drill (FlipCutter). (B) Calibrated RF ablator (Caliblator). (C)Calibrated measuring/marking tool. (D) Use of femoral aimer and FlipCutter in a left knee.

Fig 2. Representation of modified positions of AL and AMportals used for TransLateral technique, as depicted in a dra-ped left knee.

ANATOMIC DOUBLE-BUNDLE ACL RECONSTRUCTION e15

and compressed. A more detailed description of graftpreparation is available (unpublished data, S.K.Y.,August 2013).

Femoral Socket PreparationThe medial wall of the lateral femoral condyle is

prepared with the curved RF probe. Use of an RF devicefor soft-tissue debridement is preferable to shavinginstruments because this allows better preservation ofthe bony anatomy of the ACL footprint.Graft positioning in double-bundle reconstruction can

be performed at the discretion of the surgeon. Weadvocate using a direct measurement technique foranatomic placement of the femoral sockets by locatingthe AM and posterolateral (PL) bundles based on thework by Ziegler et al.31 (Fig 4). This is performed withthe curved measurement/marking tool and is nowpossible with a new calibrated RF devicedthe Cali-blator (Arthrex). We aim to leave a 3-mm bone bridgebetween the sockets in the femoral notch. The directmeasurement technique has previously been validatedfor single mid-bundle ACL reconstructions.32

The FlipCutter aiming device (Arthrex) is insertedthrough the AL portal and positioned at the pre-markedanatomic femoral origin of the AM bundle. A drillsleeve is attached to the aiming arm and pushed down

to abut against the femoral cortex through a small stabincision in the thigh. This permits the FlipCutter guidepin (with a diameter of 3.5 mm) to be inserted fromoutside to in, entering the joint under direct vision.After sizing of the TriLink, an appropriately sized Flip-Cutter is selected. We have found this to be 5.5 to 6 mmfor the double-stranded femoral sockets. Once in thejoint, the tip of the FlipCutter is flipped and retrogradedrilling of the femoral socket is undertaken. Graduated

Fig 3. Preparation of semiten-dinosus tendon as trifurcate Tri-Link graft. (A) Two TightRopesare loaded onto the semiten-dinosus, which is looped andsecured. (B) A third TightRope isloaded at the mid position. (C)The tibial end is sutured, creatinga 4-stranded limb and 2 double-stranded femoral limbs.

e16 S. K. YASEN ET AL.

laser markings on the guide pin can be read against theedge of the drill sleeve to produce a socket of appro-priate depth. We routinely create a 25-mm femoralretro-socket. The procedure is repeated for the PLsocket.

Tibial Socket PreparationTibial socket preparation is performed with arthros-

copic viewing from the AL portal and instrumentspassed through the AM portal. A single tibial socket isproduced in a similar retrograde manner using a Flip-Cutter mounted by the tibial aiming arm. This entersthe knee in the mid-bundle position and is generallyaround 8 to 8.5 mm in diameter to accommodate the4-stranded tibial limb of the TriLink construct. Weroutinely create a 30-mm retro-socket. The sum of thetibial and femoral sockets, along with the intra-articulardistance, must be greater than the overall graft length toallow adequate graft tensioning.

Fig 4. Referencing of anatomic locations of AM and PLfemoral bundles by direct measurement technique.

Graft DeploymentLooped sutures are introduced into the joint by use of

stiffened plastic sleeves through the three 3.5-mm guidepin tunnels. Our preference is to use a TigerStick(Arthrex) on the tibial side and 2 FiberSticks (Arthrex)on the femoral side. A Passport cannula (Arthrex) isinserted into the AM portal, through which these suturesare collectively grasped and withdrawn, ensuring nosoft-tissue ensnarement (Fig 5). The sutures are indi-vidually attached to the 3 TightRopes of the TriLink andact as lead sutures to draw the graft into the knee. Eachlimb is docked into the femoral and tibial retro-socketsby pulling the TightRopes through the guide pin tunnels.Once the TightRope buttons are beyond the femoral andtibial cortices, they are flipped to allow subsequenttensioning.

Graft Fixation and TensioningA TightRope RT (reverse tension) (Arthrex) is used on

the tibial side and for the AM femoral bundle. A stan-dard TightRope is used on the PL bundle. The tibial limbis gently tensioned by use of the RT system to draw itinto the tibial socket to a pre-marked depth of 20 mm.On the femoral side, the AM bundle is first tensioned inextension using the TightRope RT, followed by the PLbundle with the standard TightRope. The AM bundle isthen re-tensioned at 30� to 40� of flexion. This is basedon the typical physiological angles when these bundlesbecome taut in the normal knee.33 It is vital to ensurethat the femoral sockets have sufficient depth to take upany slack in the graft. Insufficient tunnel depth willcause the graft to bottom out, leaving residual laxity,which is difficult to correct at this stage of the

Fig 5. Passport cannula in the AM portal of a right kneeused for retrieval of passing sutures during TriLink graftdeployment.

ANATOMIC DOUBLE-BUNDLE ACL RECONSTRUCTION e17

procedure. The knee is cycled, and any further ten-sioning can be performed before cutting the leadtensioning sutures of the TightRope buttons.

Postoperative RehabilitationThe wounds and hamstring harvest tract are infil-

trated with large-volume, dilute local anesthetic.34 Thewounds are closed with absorbable sutures and stan-dard dressings applied. The postoperative regimen isunchanged from standard ACL surgery. Patients areallowed to bear weight immediately, but this is pro-tected with crutches for the first 2 weeks. A full range ofmotion is encouraged, while avoiding hyperextension.Closed-chain activities are started at an early stage, andopen-chain exercises are introduced at 3 months.Sport-specific training is allowed starting at 6 months,with the gradual introduction of cutting movements.Return to contact sports is delayed for a minimum of 9to 12 months.

DiscussionThe ACL was first described as a double-bundle struc-

ture in 1975.35 This has been confirmed by anatomicstudies of fetal specimens.36 The AM and PL bundles arenamed according to their tibial insertions. On the femur,the AM bundle lies more superiorly and anteriorly,which corresponds to a high and deep location in thenotch when viewed arthroscopically with the knee at90�. The PL bundle lies lower and further toward theshallow articular margin, that is, in a more posterior anddistal position anatomically.37 The relative contribution ofeach bundle to knee stability has been debated, but thisdoes vary throughout the arc of knee flexion. The PLbundle is taut in extension but slackens at higher flexionangles, with the AM bundle taking the majority of the

load.35,38 The biomechanical importance of the PL bundlein controlling rotational laxity has been emphasized.39

Traditional single-bundle reconstruction techniquestend to put the graft in a nonanatomic high and deepfemoral position, which may be outside of the nativeACL footprint. Transtibial drilling is unable to achieveanatomic positioning of the femoral bundles of theACL.40 At best, this matches a PL position on the tibia toan AM position on the femur.41 Graft impingementagainst the posterior cruciate ligament or femoral notchmay occur, predisposing to early failure.41 This nonan-atomic position results in inadequate kinematic restora-tion and has been blamed for residual pivot glidepostoperatively. It may also be responsible for progres-sion toward early degenerative joint disease.6,7

Anatomic single-bundle reconstruction has heraldeda move toward placing the graft within the ACL foot-print, typically using a mid-bundle position on both thetibia and femur. Drilling can be undertaken through anaccessory AM portal or with our TransLateral tech-nique.30 ACL footprint anatomy has been defined,42

and identification of the mid-bundle position on thefemur can be achieved with the direct measurementtechnique, which has been validated.32 Biomechanicaltesting has shown that single-bundle anatomic posi-tioning confers advantages over traditional graft place-ment, but further improvements may be obtained bydouble-bundle reconstruction.12,13

Such reconstructions have been criticized in the past fortheir operative complexity and potential for increasedcomplications. Outside-to-in drilling reduces the risk ofintraoperative cartilage damage during preparation of thefemoral tunnels associated with the accessory AM portaltechnique.43,44 Tunnel confluence can be a particular riskin the smaller knee and is a more significant problem onthe tibial side.29 The advantage of the TriLink technique isthat it obviates the need for 2 tibial tunnels by havinga single 4-stranded tibial limb. This is placed in theanatomic mid-bundle position.The concept of double-bundle ligament reconstruc-

tion using 3, rather than 4, tunnels is not new. It isa well-established technique for posterior cruciateligament reconstruction and represents the procedureof choice for many surgeons. It has also been describedin ACL surgery, using either a single tibial tunnelmatched to 2 femoral tunnels25,26 or a single femoraltunnel with 2 tibial tunnels.24 The kinematic stability ofdouble-bundle/single-tibial 3-tunnel techniques versus4-tunnel techniques has been confirmed in a cadavericmodel.45

The distance between the femoral and tibial attach-ment sites of the ACL changes as the knee flexes andextends, indicating that the positions are not isometric.There is growing evidence showing that the ACLexhibits favorable anisometry during knee range ofmotion. Raunest46 reported that femoral malpositioning

Table 2. Advantages and Limitations of TriLink ACLReconstruction

Description

AdvantagesDouble bundle onfemur

Matching femoral anatomyImproved biomechanical stabilityImproved femoral footprint fill

Anatomic positioningof femoral bundles

No need for knee hyperflexionMatches functional ACL anisometry

Single tibial bundle Avoids technical difficulties with 2 tibialtunnels

No risk of tunnel confluence and/orfracture

Sockets created,not tunnels

Bone preservation

Single semitendinosustendon used

Excellent size of graftdless risk of graftfailure than traditionally “smaller” PLbundle

Preservation of gracilis for multiligamentcases or as secondary medial stabilizer

Cortical suspensoryfixation usingTightRopes

Robust and reliable fixation methodAllows in situ adjustment of tension

LimitationsTechnicallychallenging

More challenging than single-bundlereconstruction but easier than double-bundle techniques

Graft/sutureentanglement

Meticulous suture management isrequired,which canbe facilitated byuseof Passport cannula through AM portal

e18 S. K. YASEN ET AL.

had a greater effect on disturbing isometry thanchanges with respect to the tibia, with the over-the-top position giving the most unsatisfactory result. Arecent study using 3-dimensional computed tomog-raphy confirmed the anisometry of mid-bundle graftplacement, with the greatest intra-articular distancebeing found in full extension and decreasing withknee flexion.47 This suggests that single-bundlereconstructions can potentially allow the graft toslacken as the knee flexes.Cadaveric studies by our group (unpublished data,

J.O.S., July 2013) support this. We have found thatvariations at the tibial attachment sitemakes significantlyless difference to overall anisometry than changes on thefemoral side. Changing the femoral attachment sitecauses large alterations in the intra-articular distancebetween the tibial and femoralfixation points of the graftduring knee range of movement. These findingshave been confirmed using mathematical modeling(unpublished data, J.O.S., July 2013) and suggest thatmaximum stability may be gained using a graft witha single tibial attachment and multiple femoral attach-ments. Respecting the femoral attachments of the nativeACL is thus evidently more important than tibial posi-tioning. Using 2 bundles on the femoral side alsoimproves footprint coverage, which has been shown tobe beneficial when compared against single-bundlereconstructions.48 This provides strong biomechanicaljustification for the use of a refined trifurcate graft, whichallows the surgeon to maximize stability by re-creatingthe anatomic functional anisometry of the 2 bundleswhile minimizing operative complexity.ACL anisometry underlines the importance of ten-

sioning the AM and PL bundles independently at theappropriate knee flexion angle. The triple suspensoryfixation system of the TriLink construct makes thispossible, in contrast to previously published double-bundle/single-tibial techniques.25 We tension the PLbundle in extension and the AM bundle in 30� to 40� offlexion to better replicate normal functional anatomy.Other limitations of double-bundle/single-tibial tech-

niques include the requirement for double-tendonhamstring harvest or the use of allograft. An additionaladvantage of the TriLink is that it uses a quadrupledsemitendinosus graft. Single-tendon hamstring harvestallows the gracilis to be preserved as a secondary medialstabilizer in the ACL-injured knee. Furthermore, preser-vationof the gracilis has alsobeen shownto reducedonor-site morbidity and limit loss in knee flexion strength.49

In addition, it may be useful in cases requiring multi-ligament reconstruction. Quadrupling of the semiten-dinosus provides anexcellent graft diameter inmost cases.In our TransLateral series, our mean graft diameter is8.6 mm. The femoral limbs are double strandedand typically measure 5.5 to 6 mm. This representsa significant advantage over the use of more traditional

doubleehamstring tendon techniques, inwhich 1 bundleis made up of a doubled semitendinosus graft and theother is a doubled gracilis graft. The doubled gracilis isfrequentlymuch smaller and is therefore at risk of failure.One of the limitations of the described procedure is that

it does remain more technically challenging than single-bundle techniques, but it is simpler than double-bundleapproaches, while conferring similar advantages. Metic-ulous suturemanagement during the procedure is key toavoid inadvertent soft-tissue ensnarement or entangle-ment of the graft during deployment. Table 2 summa-rizes the advantages and limitations of the technique.TransLateral ACL reconstruction with the TriLink graft

is a novel technique for anatomic double-bundle, all-inside surgery. This represents an opportunity to conferthe biomechanical and kinematic benefits of double-bundle reconstruction using a simplified operativeprocedure, in addition to the advantages of single-tendon hamstring harvest. The TransLateral philosophyallows the surgeon to maintain an excellent view fromthe medial portal for anatomic placement of the femoraltunnels while working from the lateral side. Tunnelplacement can be confirmed by directmeasurement. Theall-inside approach is bone preserving and achievesexcellent cortical fixation on both the femur and tibia. Asingle tibial tunnel avoids the risk of tunnel confluence,which is a particular concern in smaller knees, but theconstruct still permits independent tensioning of the AM

ANATOMIC DOUBLE-BUNDLE ACL RECONSTRUCTION e19

and PL bundles. These factors decrease operativecomplexity, reducing surgical time, and positively impactthe cost and safety/efficacy profile of the procedure.Early clinical results have been encouraging.

AcknowledgmentThe authors thank Arthrex for supplying materials,

facilities, and its expertise in developing the describedtechnique.

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