lia pes anserinus

7/28/2019 Lia Pes Anserinus

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TECHNIQUE OF ANTERIOR CRUCIATE

LIGAMENT RECONSTRUCTION USING

PES ANSERINUS TENDONSS. PLAWESKI

A. Michallon University Hospital - Grenoble, France

A number of techniques have been found to work well inthe reconstruction of a torn anterior cruciate ligament(ACL). We agree with JY Dupont that the chief outcomecriterion in the long term is an anatomical one, with"complete restoration of the knee joint." However, inaddition to the modified Marshall-MacIntosh and similar

techniques for ACL reconstruction, which are known toprovide long-term stability, several arthroscopictechniques have been developed, which have thebenefit of being minimally invasive and of causing lessiatrogenic damage. This, obviously, is a majorconsideration in ACL surgery. With the development ofthese techniques, the choice of graft harvesting site hasalso become an important factor. It should be borne inmind that, in many athletes, the patellofemoral painfollowing graft harvesting from the extensor mechanism

will rule out a return to sports at the previous level.Using the pes anserinus as a donor site appears to be asafer alternative. While the long-term stability outcomeof semitendinosus-gracilis (STG) grafts is not yet fullyknown, there is a current trend to use these pestendons. With the advent of better arthroscopic aimingand graft fixation systems, an increasing proportion ofthe ACL reconstruction "market" is being catered for bySTG grafts. However, there are pes tendon grafts andpes tendon grafts, as may be seen from the history of

the use of these tendons in ACL reconstruction surgery(P Colombet). The 1999 Symposium of the FrenchSociety for Arthroscopy also stressed the fact that themany ways in which pes tendon grafts may beperformed make it difficult to assess the value of theconcept in a multicentre study. In the interest ofevaluation, ACL reconstruction with pes anserinustendons should be performed following certain rules.PATIENT POSITIONING


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The anteromedial portal for the instruments should bemore distal and more anterior, so as to provide the idealangle for drilling the femoral tunnel and for inserting theinterference screw, if arthroscopic aiming is being used.With unduly posterior placement of this portal, the

medial condyle would obstruct the view; withexcessively anterior placement, the ligamentummucosum would get in the way (Fig. 2a and b).

Fig. 2a and b Arthroscopic portals. L = lateral site; M = medial site. Arthroscopicaiming over the medial meniscus.

HARVESTING THE PES TENDONS

This stage of the procedure is a common feature,regardless of the fixation technique to be used. A skinincision is made between 6 and 7 cm distal to thetibiofemoral joint line, and 2 cm medial to the tibialtubercle. The incision is ca. 25 mm long, and requiresmeticulous haemostasis. Great care is taken not todamage the sensory branch of the saphenous nerve(Fig. 3).


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Fig. 3 Skin incision on anteromedial aspect, 2 cm from the tibial tubercleand 6 cm below the medial joint line

The tendons of of semitendinosus and gracilis (Figs. 4and 5) are identified under the fascia thus exposed,working from anterior to posterior; once the tendonshave been exposed, they are removed using a stripper.


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Fig. 4 Knee flexors (source: P. Kamina)Fig. 5 Pes anserinus tendons (medial view)(Source: P. Kamina)

Preserving the insertions of the tendons makes

harvesting easier. In order correctly to identify thecourse of the tendons at the deep surface of the fascia,a small longitudinal incision should be made very farforward, to partially detach the tibial insertion ofsartorius along the anterior aspect of the tibia. Thesartorius tendon will be found just in front of and overthe tendons of semitendinosus and gracilis, with which itforms a final common tendinous insertion. This allowsthe tendon sheath of the semitendinosus to beidentified. The fascial incision can then be very readily

extended horizontally along the upper margin of thesemitendinosus. The two tendons will then be visibledeep to the fascia. The gracilis, in front of thesemitendinosus, is taken on, and firmly pulled upwardswith, a right-angled clamp. This will allow part of thetendon to be pulled out of the incision, and to insert thestripper over a distance of ca. 22 cm, to themusculotendinous junction. The semitendinosus isharvested in like manner. This technical detail is ofgreat importance: if the stripper is pushed in withoutthe tendons having been pulled out of the incision, therewill be a mjaor risk of the tendon being prematurelyamputated half-way along its length. The correctprocedure, therefore, consists in "pulling" on thetendon, rather than in pushing on the stripper (Fig. 6).The distal portion of the tendon is detached from itstibial insertions (care being taken to ensure goodhaemostasis). The two tendons can then be readilyremoved distally (Fig. 7).

Fig. 6 Stripping of gracilis, with firmFig. 7 The two tendons have beenstripped, and will subsequently be


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countertraction to deliver the tendon out ofthe incision detached from their distal insertions.

Even with the precautions described above, things can

go wrong, and part of a tendon may be lost. While thisis obviously not ideal, some extra material may begained by going further down along the tibial periostealinsertion; three strands may be sufficient to fashion agraft with a minimum diameter of 7 mm. If an entiretendon is lost, the intended technique will have to beabandoned. This is why a longitudinal incision is soimportant: if need be, it can be extended proximally, toallow, for instance, a Jones procedure to be performed.Once the graft has been harvested, it is prepared on the

workbench. Any muscle remnants are removed, and thetwo tendons are laced together with a No. 2 Ethibondsuture (Fig. 8). The two tendons thus united are thenfolded in half, so as to produce four parallel strands atleast 9 cm in length (Figs. 9 and 10).

Fig. 8 The tendons have been sutured

together.

Fig. 9 Schematic diagram of the graft


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Fig. 10 Measuring graft length Fig. 11 Sizing the four-strand graft

Traction sutures are inserted at either end of the graft.The four-strand graft is sized to a uniform diameter of

7-10 mm (Fig. 11). The total length of the graft shouldnot be less than 85 mm; ideally, it should be 110 mm.The length must be taken into account when fashioningthe femoral socket. Once the graft has been prepared inthis way, it is wrapped in a moistened sponge, to awaitfurther use. On no account should the graft besubmerged in saline, since doing so would causeswelling. Some surgeons stitch the tendons togetheronly over the last 2 cm at either end. The questionarises whether this will allow better positioning of the

bundles as the knee is being mobilized. We think that,given the great elasticity of the pes tendons, stretchingduring intraoperative mobilization should be avoided.Therefore

- the graft should be cyclically stressed, either on theworkbench, after preparation, or following insertion intothe knee, prior to tibial fixation; and- the compliance of the graft should be reduced, bysuturing the two limbs together over their entire length.

This basting with a nonabsorbable suture willprecondition the bundles and thus "stiffen" the graft.

IV ARTHROSCOPIC SURGERY

A - Intra-articular preparation

The remnants of the torn ACL are debrided with ashaver or with basket forceps. At the tibial attachment

site, care should be taken to ensure that there is notany bulky ligamentous tissue left standing. However,


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preserving a little tissue at the native footprint of theACL may be useful, not only to mark the intra-articularexit site of the tibial tunnel, but also in order to placethe graft against tissue containing sensory neurons, inthe interest of proprioception. Graft sizing to 8 or 9 mm

will allow the tibial attachment fibres of the torn ACL tobe preserved. This is an advantage of pes grafts over aJones procedure, which involves the use of a muchwider graft. The notch is debrided with a shaver. Wenever perform a notchplasty. However, it helps tostraighten the medial aspect of the lateral condyle, in astrictly sagittal plane, so as to expose the over-the-topposition on the posterior cortical rim at the intercondylarnotch. Attention should be paid to the "resident's ridge"two thirds of the way posteriorly, which may cause

faulty placement of the femoral socket entry point. Thecorrect site is beyond this ridge, towards the over-the-top position, into which the aiming device is hooked.

The "black hole" of the notch should appear on thescreen. Aiming can then be performed to suit thepattern of the patient's knee, at a distance of ca. 5 mmforward from the over-the-top position This so-calledisometric point should be at 11 o'clock in the right knee,and at 1 o'clock in the left knee (Fig. 14).

Fig. 14a Frontal view Fig. 14b Sagittal view

Fig. 14a-cFemoral socket entry point: isometric

position in the notch


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Fig. 14c Femoral aimer (5-7 mm anterior tothe over-the-top position)

Tibial tunnel

The tibial tunnel exit hole inside the joint is not alwayseasy to establish. This is why it is useful to leave thenative footprint of the ACL standing. The guide pincannula of the drill guide is applied to a point ca. 3 to 4cm below the joint line, medial to the tibial tubercle.The tip of the tibial drill guide is hooked in the posteriorfibres of the footprint. The back of the tip should be ca.2 to 3 mm anterior to the forward-most fibres of thePCL. The device is placed in such a way as to form an

angle of about 45 degrees with the long axis of the tibia(Figs. 12 and 13a). Regardless of the device used, theangle between the tibial tunnel and the horizontal armof the guide should always be set at 55. This producesoptimal guide pin orientation to allow drilling thefemoral tunnel through the tibial tunnel, if desired. Thepin should protrude a few centimetres into the joint, tomark the femoral socket entry point. An arthroscopiccheck is made to ensure that the tip of the pin is at thecorrect site on the femur (Fig. 13b). Some surgeonsinsist on checking the pin position on the imageintensifier. With the knee fully extended, the position ofthe pin relative to Blumensaat's line is checked, to ruleout trochlear impingement. The intersection ofBlumensaat's line with the tibial plateau must be at theanterior border of the tibial tunnel. If the tunnel isexcessively anterior, there will be graft impingement,which may result in the graft being guillotined or in lossof extension postoperatively.


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m

Fig. 12 Tibial aiming (using the AcufexDirektor)

Fig. 13a Tibial aiming. Angle between

horizontal arm and guide pin cannula =55.broche guide = guide pin

Fig. 13b Establishing the femoral socketentry point (knee flexed to 80)

The tibial tunnel is created using a cannulated reamermatching the diameter of the graft. It is essential to

have matching tunnel and graft diameters, so as toprevent graft micromotion inside the bony tunnels.


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C - Femoral socket

The blind-end femoral tunnel may be created in twoways - either through the tibial tunnel, which has the

advantage of providing an excellent view of the femoralentry site, with the knee flexed to 90 degrees; orindependently of the tibial tunnel, with the knee inhyperflexion. In the latter case, the femoral socketwould be on a different axis from that of the tibialtunnel. This approach has the disadvantage of giving aless good view of the so-called isometric position on thefemur, since the ligamentum mucosum obstructs thedrill guide at the back.

A - Arthroscopic aiming The knee is placed inhyperflexion. The femoral aimer is hooked into the over-the-top position. The device comes in a range of offsets(mean, 5-6 mm). The choice will depend on theanatomical pattern of the notch. The guide pin isintroduced into the femur, and pushed until the lateralcortex has been pierced. The socket is then reamed tomatch the diameter of the tibial tunnel. The depth of thesocket will be a function of the graft length measuredearlier on (mean depth, 35 mm). A traction wire is

placed in the slot of the guide wire, which will allow awire loop to be brought out of the tibial tunnel. This loopwill then be used to pull the graft through the tibialtunnel. The graft should move easily, but fit snuglythroughout the tibial tunnel. The proximal end of thegraft engages into the blind end of the femoral socket(Figs. 21-23).

Fig. 21 Arthroscopic aiming for femoral socket, through the medial portal,


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with knee fully flexed

Fig. 23 Arthroscopic insertion of femoral interference screw (RCI technique)

B - Concentric aiming The axis of the femoral socket isin line with the tibial tunnel axis. For this to beachieved, the knee will need to be flexed to between 70and 90 degrees. The femoral aimer is introducedthrough the tibial tunnel, and positioned as described

above (ca. 5 mm anterior to the over-the-top position).The reaming of the socket, and the depth attained (35-40 mm), can be readily observed through thearthroscope (Fig. 15).

Fig. 15 Creating the femoral socket through the tibial tunnel


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GRAFT FIXATION

Many different ways of graft fixation have been devised.Rosenberg has shown that a four-strand STG graft that

is fixed inside the bone at each end and subjected totensile stress along its axis will tear in mid-substance in5% of cases; in 40%, the tear will be at the bony tibialinsertion; and in 55%, at the bony femoral insertion.The calculated (theoretical) isometry of the graft cannotbe obtained with current ligament reconstructiontechniques. Unfortunately, the construct is not veryforgiving: if the tunnels are only slightly off the correctisometric position, the substitute ligament may slackensecondarily. The way in which it stretches will be a

function of the initial graft fixation strength.

Where the tensile stress exceeds the the yield strengthof the fixation system, the graft will loosen. This earlylaxity is directly related to the fixation system used. If,on the other hand, the systerm is not mechanicallystressed beyond its initial failure strength, further stressmay cause gradual stretching of the graft fibres. Someauthors have shown that initial graft micromotion in thetunnels occurs in 90% of the reconstructions; this is

thought to be due to the fact that ideal isometry wasnot obtained. These findings show the importance of thetwo fundamental features of knee ligamentreconstructions: isometry, and graft fixation.

Femoral fixation:Three main meansof fixation (Fig. 16)


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Fig. 16 Arthrex femoral guide and marking hook(1) - Systems with purely cortical support, the best-known of which is the EndoButton. This systemconsists of a metal device that is placed flat against the

anterolateral cortex of the lateral condyle. The graft isattached to the EndoButton by a 5-mm polyester tapeor by a braided suture of the surgeon's choice. Two-limbtendon grafts may be fixed with one EndoButton, orhave each limb fixed with a separate button. The tensilestrength of these devices has been tested and found tobe reasonably satisfactory; however, correct positioningof the button on the lateral cortex is not easy toachieve, and requires accurate calculation of the totallength of the femoral tunnel.

The theoretical advantage of cortical fixation is offset bythe technical problems at surgery, and by worries aboutthe strength of the linkage material between the graftand the button. Another mechanical disadvantage is theincrease in the total length of the graft that will besubject to strain (since the proximal fixation site will be8-10 cm away from the joint surface). This is whysurgeons using an EndoButton would be well advised tofully stabilize the graft in the tunnel by inserting a

supplementary interference screw into the femoralsocket.


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Fig. 20 TransFix (Arthrex) femoral fixation system andtibial interference screw

(2) - Transfixion devices, such as the TransFix (Fig.20). The TransFix technique involves the insertion of a

metal implant into the lateral condyle, strictlyperpendicular to the axis of the femoral socket. Thedevice passes between the two limbs of the graft. Oncethe femoral socket has been fashioned with concentricreaming, a marking hook, which is firmly mounted onthe femoral guide, is introduced. The hook (whichmatches the socket diameter) is pushed home in thesocket. A guide pin is drilled through the distal femur,from lateral to medial. This pin passes through anopening in the marking hook, in the depth of the

femoral socket (Figs. 16 and 17a). The guide pin isreplaced by a guide wire, which is brought out throughthe tibial tunnel (Fig. 17b). The graft is loaded into thewire loop. Pulling on the two ends of the wire will takethe graft through the tibial tunnel and into the femoralsocket (Fig. 18). The TransFix implant is slid over thewire, through the axilla of the graft, and impacted intothe lateral femoral cortex (Figs. 19 and 20). The implantmust not sit proud laterally, since hardware protrusionmay cause soft-tissue irritation. The advantage of this

mode of fixation is that it produces ideal tensile-strength conditions. However, there are twodisadvantages: the technique is complex, and requires alearning period; and - as with the technique describedabove - the distance of the fixation construct from thejoint surface increases the total length of the graft thatmay undergo strain.


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Fig. 16 Arthrex femoral guide and markinghook

Fig. 17a A guide pin is drilled through thedistal femur.

Fig. 17b The pin is replaced by a wire,which is brought out through the tibialtunnel.

Fig. 18 The graft is pulled up into the tibialtunnel.


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Fig. 19 The TransFix implant is impacted.fil de traction du transplant = graft traction sutures

(3) - Interference systems (interference screws). Manyinterference screw patterns have been devised and arecommercially available.

The RCI screw has a blunt thread, which protectsagainst graft damage, and a round head, whichminimizes the stress on the graft fibres at the femoralsocket entrance (Fig. 22). The screw has a 2.4 mmcannulation, which accommodates the largest-diameterguide pin, thus facilitating arthroscopic screw insertion(Fig. 23).

Fig. 22 Femoral tunnel positioned independently of tibial tunnel. Graft pulled throughin two stages


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Fig. 23 Arthroscopic insertion of femoral interference screw (RCI technique)

It comes in a range of diameters, from 7 mm to 9 mm,several lengths (from 25 mm to 40 mm), and withnormal or reverse thread. Pinczewski recommends astandard diameter of 7 mm for the femoral screw (or of8 mm, in poor bone stock or where the socket has beenmade too wide in relation to the graft diameter). For asocket diameter of 7 mm or 8 mm, a 7-mm screw

should be used; for a 9-mm or 10-mm socket, thepreferred screw diameter would be greater (8 mm or 9mm). Since the interference screw must be placedanterior to the graft, with the graft residing against theposterior wall, Pinczewski has developed a reverse-thread screw (reverse RCI), for use in the right knee ofpatients. With this hardware, he observed significantlyless graft stretching. Currently, the screw is made oftitanium; it will soon be available in a polylactide PLA100 version. There are many other metal or

bioabsorbable screws on the market. At our presentstate of knowledge, and in the light of our clinicalexperience with PLA 98 screws, we would recommendthe use of polylactide screws. However, these resultswere reported in bone-to-bone fixation studies (Jonesprocedure). The long-term behaviour of bone-tendonfixation constructs using polylactide interference screwsis as yet unkown. This aspect will need to be closelymonitored; studies of direct interference screw fixationon the femoral side using PLA interference screws are

ongoing.


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Tibial fixation

Fig. 24 Femoral and tibial interference screws

fil de traction du transplant = graft traction sutures

(a) - Interference screws For the tibial side, too, manyscrew patterns are on offer (Fig. 24). We prefer a PLA98 screw of a diameter matching that of the tibialtunnel. PLA 98 is resorbed slowly, which permitsexcellent primary fixation to be obtained, and ensuressound secondary fixation up to and beyond the stage ofingrowth. In our study, no granuloma formation orresorption products were seen at 3 years' follow-up.

Complementary fixation (with a cortical staple) may beconsidered. In a study of female patients with poor bonestock, Pinczewski showed significantly less residualstretch in the patients managed with a screw andstaple, as compared with those who had only aninterference screw inserted (Figs. 25-27).


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Fig. 25 Radiographic check of correct graftpositioning, using radiological criteria(Blumensaat's line, Aglietti index, etc.)

Fig. 26 Check radiograph (4-strand STGgraft fixed with TransFix and a Phusistibial screw)

Fig. 27a and b Postoperative check radiographs (TransFix + tibial RCI screw)

(b) - Tibial anchors, isolated tibial staples These deviceshave the disadvantage of lesser pull-out strength and agreater graft length subject to strain (bony fixation sitewell away from the exit of the tibial tunnel in the joint).

Technical variants: The femoral tunnel may be createdusing an outside-in technique; the tendons may be leftattached at their distal insertion. Other femoral and


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tibial fixation systems have been devised: Rigid-fix,Endofix, LinX HT, spiked washers, belt-buckle,anchors, etc.).

The choice of fixation technique will depend upon a

number of considerations:- Fixation should be as close as possible to the joint line,to prevent a windshield wiper effect causing gradualtunnel expansion, and a bungee effect , as a result oflongitudinal graft-tunnel motion. Correctly sizedinterference screws may be a solution. In the tibia,these devices are commonly used; in fact, somemanufacturers have developed new systems using morethan one screw (Tri-Cortical). In the femur, finding agood fixation system is more of a problem: interference

screws meet the requirement for fixation close to thejoint line; however, mechanical studies have shownthese screws to have less pull-out strength on theirown, as compared with their use in conjunction withother fixation devices. A hybrid construct may be ideal(e.g. EndoButton + interference screw, or TransFix +interference screw).

Graft isometry is tested , prior to tibial graft fixation, bymeasuring the change in length of the substitute ACL

while ranging the knee from extension to 90 degrees offlexion. The graft is mulitply cycled, to preventsubsequent stretching. The tibial fastener is insertedwith the knee in slight (30-40) flexion; the tibialapproach is closed in layers over a suction drain; andthe arthroscopic portals are closed.

POSTOPERATIVE MANAGEMENT

In the immediate postoperative period, the patient willbe on an analgesic and anti-inflammatory regimen(femoral nerve block, drugs). A splint may be used, forpain relief only. Active extension exercises are startedthe day after surgery, as is walking with weight-bearing,using crutches that will be discontinued as soon as goodknee locking has been obtained (between two weeks toa month postoperatively).

REHABILITATION

The rehabilitation protocol is aimed at


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- Full active extension: electrostimulation, relief of graftharvest site pain (which may cause an earlypostoperative flexion contracture).

- During the healing phase, the hamstrings should not

be worked with active concentric resisted exercises(which may cause muscle sprains).

- Patellar mobilization is performed immediately. Inpatients with excessive knee laxity, exercises involvinghyperextension may cause a recurvatum deformity, andshould be avoided.Proprioceptive training is started in the third week,using closed kinetic chain exercises, with isometriccocontraction of the quadriceps, hamstrings, and

gastrocnemius.

- The gradual return to dynamic work is achievedthrough lower-limb closed-chain exercises. Restorationof exercise capacity starts at 6-7 weeks, with aquaticexercises and cycling on firm ground. A return to non-pivot, non-contact sports is allowed at between 2 and 3months.

CONCLUSION

Four-strand STG grafts are being increasingly used inclinical practice. At the 1999 Symposium of the FrenchSociety for Arthroscopy, the following indications wereestablished:

- quadriceps-dominant sports;- kneeling jobs;- revision of failed reconstructions using patellartendon;- anterior knee pain;- patients > 40 years of age.The recognized contraindications are:

- prior surgery of the medial soft tissues;- contact sports;- major anterior instability (more than 10-mmdifference in anterior translation between the affectedand the well knee);- excessive knee laxity;

- female patients practising little or no sport.


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Other clinical studies are ongoing. The important aspectof this evaluation will be the collection of so-calledanatomical results, and the creation of homogeneousseries. With strict attention to the details of surgicaltechnique, and with the use of a fixation system of

proven efficacy, more patients should be allowed tobenefit from this form of ACL reconstruction.

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