ST/G ACL reconstruction: double strand plus extra-articular sling vs double bundle, randomized study at 3-year follow-up

ST/G ACL reconstruction: double strand plus extra-articularsling vs double bundle, randomized study at 3-year follow-up

S. Zaffagnini1, D. Bruni1, A. Russo1, Y. Takazawa2, M. Lo Presti1, G. Giordano1, M. Marcacci1

1Rizzoli Orthopaedic Institute, Biomechanics Laboratory, Bologna, Italy, 2Department of Orthopaedic Surgery, Juntendo University,Bologna, ItalyCorresponding author: S. Zaffagnini, MD, Rizzoli Orthopaedic Institute, Biomechanics Laboratory, Via Di Barbiano 1/10,40136 Bologna, Italy. Tel: 139 051 6366506-6366520-6366518; Fax: 0039 051 583789, E-mail: [email protected]

Accepted for publication 11 April 2007

Several investigators have reported the presence of biome-chanical, kinematic, anatomic, fiber orientation patternsand biological differences between the anteromedial bundleand the posterolateral bundle of ACL. The purpose of thisprospective randomized study was to compare the clinical,instrumental and X-ray outcome of two ACL reconstructiontechniques with hamstring tendons: one with a single intra-articular bundle associated to an extra-articular sling, thesecond with a more anatomic double-bundle technique thatreproduces better the native ACL function. From an initialgroup of 100 patients who underwent ACL reconstruction,72 patients (35 single bundle plus lateral plasty and 37

double bundle) were evaluated with IKDC, Tegner score,KT2000 arthrometer, Activity Rating Scale, PsychovitalityQuestionnaire and Ahlback radiographic score at a mean 3years follow-up. Double-bundle group showed significantlybetter results regarding IKDC, ROM, Activity RatingScale and time to return to sport. Also KT 2000 showedsignificant differences in objective stability. The double-bundle technique for ACL reconstruction described in thispaper has demonstrated significantly better subjective,objective and functional results compared with a double-stranded hamstrings plus extra-articular sling at a minimum3-year follow-up.

Many clinical reports have demonstrated almost suc-cessful results for ACL reconstruction in a short-term follow-up (Jomha et al., 1999; Marcacci et al.,2003b; Giron et al., 2005). However, the durability ofthese operative options is sometimes unsatisfactory,most of all in high level athletes, owing to thedevelopment of clinically symptomatic instabilityand to degenerative knee changes observed with theresults in long-term studies (Shelbourne & Gray,2000; Jarvela et al., 2001; Williams et al., 2004;Hart et al., 2005).Recently, several investigators have reported the

presence of biomechanical (Takai et al., 1993; Race& Amis, 1994; Sakane et al., 1997), kinematic (Gab-riel et al., 2004), anatomic (Amis & Dawkins, 1991;Takahashi et al., 2006) and fiber orientation patterns(Neurath & Stofft, 1992; Baek et al., 1998; Zaffagniniet al., 2004) differences between the anteromedial(AM) bundle and the posterolateral (PL) bundle ofACL. Single-bundle ACL reconstruction techniqueshave been found to be less effective in resistingcombined axial and planar stresses and do notguarantee rotational stability because they are pri-marily focused on the reproduction of the AMbundle and they are dependent upon the orientationof the femoral tunnel (Loh et al., 2003; Sbihi et al.,

2004; Giron et al., 2005). Based on a kinematicanalysis of cadaver knees, Yagi et al. (2002) repor-ted that anatomic two-bundle ACL reconstructionguarantees more similar results to the physiologicallyintact knee and provides a better biomechanicalbehavior, especially against rotational stresses com-pared with standard, single bundle, ACL reconstruc-tion. Moreover Gabriel et al. (2004) demonstratedthat the PL bundle plays an important role resistingrotatory instability, most of all with the knee nearcomplete extension.With the aim to reproduce a ligament more similar

to the original native ACL and to restore opti-mal rotational stability, several techniques of dou-ble-bundle ACL reconstruction have been described(Muneta et al., 1999; Takeuchi et al., 2002; Marcacciet al., 2003a; Cha et al., 2005). However, the realadvantage of any specific surgical option for double-bundle ACL reconstruction has not been completelyestablished. On this argument, Adachi et al. (2004)recently reported the lack of significant advantage ofdouble-bundle ACL reconstruction vs a single-bun-dle one, both in terms of stability and proprioception.In our clinical experience, we normally use a

modified semitendinosus and gracilis (STG) techni-que, which combines an intra-articular passage with

Scand J Med Sci Sports 2008: 18: 573–581 Copyright & 2007 The Authors

Journal compilation & 2007 Blackwell MunksgaardPrinted in Singapore . All rights reservedDOI: 10.1111/j.1600-0838.2007.00697.x

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an extra-articular lateral sling for single-bundle ACLreconstruction (Marcacci et al., 1998). In 2000, wealso started using an original technique for double-bundle ACL reconstruction using hamstring tendons(Marcacci et al., 2003) with the aim to reproduce ananatomically and biomechanically normal ACL.The purpose of this prospective randomized study

was to compare the clinical, instrumental and X-rayoutcome of these two ACL reconstruction techni-ques with hamstring tendons: one with single intra-articular bundle associated to an extra-articular sling,the second with a more anatomic double-bundletechnique.

Materials and methods

We included in this study 100 consecutive patients (50 malesand 50 females) with unilateral ACL insufficiency. Inclusioncriteria were a positive Lachman and Pivot shift test respect tocontralateral healthy knee. Associated lesions included menis-cal injuries, grade 2 MCL injuries and Outerbridge grade 1and 2 chondral injuries. Of these patients, 10 were lost to finalfollow-up because they were unavailable for final follow-upexamination. Four patients with grade 3 MCL injuries and 12patients with associated partial PCL injuries at arthroscopicalevaluation were excluded. Other two patients were excludedbecause they showed Outerbridge (1961) grade 3–4 chondralinjuries at arthroscopical evaluation. We finally included in

this study 72 patients (40 males and 32 females) with unilateralACL insufficiency who were operated by the same surgicalstaff between 2000 and 2002.

All the patients were assigned to single- or double-bundleACL reconstruction technique with autologous STG ham-string tendons, systematically following a completely rando-mized protocol based on the use of computer-generatedrandomization tables.

Thirty-five patients (20 males and 15 females) underwentthe single bundle plus lateral plasty and the other 37 patients(20 males and 17 females) were treated with the double-bundletechnique. By a statistical point of view, the compositionof the two groups in terms of mean age results highlyhomogenous (single-bundle mean age: 26 years; range: 19–45years; double-bundle mean age: 27 years; range: 21–46 years;SD5 9.5; b5 0.9). Ethical approval was obtained fromthe internal review board. All subjects were informed aboutthe study procedure, the purpose of the study and any knownrisks, and they all gave informed consent.

All patients were evaluated at minimum follow-up of 3years (min. 3; max. 5; mean 3.9 years.).

There were no significant differences preoperatively be-tween the two groups in terms of gender, body weight(b5 1), interval from injury to surgery (b5 1), and level ofsports activity determined according to Activity Rating Scale(Marx et al., 2001) (double bundle: 13.4; range 4–16; SD5 2.6;single bundle: 12.9; range 1–14; SD5 2.6; b5 0.8). No statis-tical difference was found also regarding associated surgery.On the other hand, we have found a significant differenceregarding pre-operative Psychovitality Questionnaire score(Gobbi & Francisco, 2006) between the two groups (doublebundle: 15; single bundle: 13; P5 0.009) (Table 1).

Table 1. Demographics and preoperative findings

Surgical procedure Single bundle plus lateral plasty Double bundle

Number of patients 35 37Males 20 20Females 15 17Mean age and range (b5 0.93) 26 years

(19–45 years; SD 5 10.2)27 years(21–46 years; SD 5 9)

Mean height (b5 1) 174 cm(155–192 cm; SD 5 7.4)

175.4 cm(163–195 cm; SD 5 7.6)

Mean weight (b5 1) 76.6 kg(50–115 kg; SD 5 14.6)

69.8 kg(50–90 kg; SD 5 10.1)

Sport injury (b5 0.8) 27 30Dominant leg injury (b5 0.5) 18 22Meniscus lesions (b5 0.51) 25 20Chondral outerbridge I1–II1 lesions (b5 0.5) 1 1From injury to surgery time (b5 1) 8.2 months

(1–48 months; SD 5 10.4)6.9 months(1–48 months; SD 5 10.4)

IKDC (b5 0.8) A B C D A B C D0 0 2 33 0 0 3 34

KT 2000 (b5 1) o3 mm 3–5 mm 45 mm o3 mm 3–5 mm 45 mm0 0 35 0 0 37

Manual pivot shift (b5 0.51) 1 11 111 1 11 1110 2 33 0 3 34

Tegner score (b5 0.7) 7(1–10; SD 5 2)

7.5(2–9; SD 5 1.5)

Pre-operative activity rating scale score(max. 16) (b5 0.8)

12.9(1–14; SD 5 3.5)

13.4(4–16; SD 5 2.6)

Pre-operative psichovitality questionnairescore (max. 18)

(P 5 0.009)(b5 0.52)

13(6–18; SD 5 3)

15(6–18; SD 5 3)

SD, standard deviation.

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This score describes the patient motivation and tries to eva-luate his compliance regarding post-operative rehabilitationprogram and his expectations after surgery respect to sportactivity resumption.

The majority of injuries were non-contact type injuries thatoccurred during sports activities.

Operative procedures

Graft harvesting and preparation

The ACL reconstruction was performed by using autogenoussemitendinosus and gracilis tendons (ST1G) from the ipsilat-eral limb. Tendons were harvested with a blunt tendonstripper (Acufex, Microsurgical, Mansfield, MA, USA). Thetibial insertions of the two tendons were left intact. Theharvested tendons were then tightly sutured and loopedaround the edges of the free proximal ends to obtain asufficient strength for traction and to allow easy passage ofthe tendons through the tibial and the femoral drill holes.

Double strand plus extra-articular sling

This technique has been published in 1998 (Marcacci et al.,1998). The tibial tunnel was located in the medioposterior partof the ACL tibial insertion. After drilling the tibial tunnel,an over-the-top passage was performed, creating a 2–3mmgroove in the PL aspect of the femur. The two strands graftwas passed through the tibial tunnel and over the top, andcycled in tension through complete range of motion (ROM)before fixing it with double staples in the groove of lateralcondyle while maintaining the knee at 901 of flexion and thefoot and tibia in external rotation. The groove in the PL femurwas made to increase the biological fixation and to put thegraft more closely to the normal anatomical position. Theremnant part of the combined graft was then fixed to Gerdy’stubercle with a metal staple passing under the fascia to serve asan extra-articular lateral plasty with the knee kept in the sameposition (Fig. 1).

Double-bundle reconstruction

The tibial tunnel is executed as for single-bundle reconstruc-tion. For the femoral tunnel, the knee is flexed to approxi-mately 1201 and the guide pin is advanced in the groove fromthe medial portal at 10 o’ clock position 3mm anteriorly to theposterior margin of the notch, until it passes the lateralfemoral cortex. The exit point in the lateral aspect of thefemur should be immediately above the end of the lateralfemoral epicondyle, at about 5mm from the over-the-topposition. After a lateral incision, the tendons are passed overthe top. A suture loop is introduced into the joint through theAM portal using a suture passer and then pulled into thefemoral tunnel under the arthroscopic view. The stitches onthe free end of the tendons are looped again onto the passingsuture, which are pulled through the femoral tunnel, kneejoint, and tibial tunnel to retrieve the graft from the tibialincision. The graft is tensioned, and the knee cycled through afull range motion approximately 20 times, checking the iso-metry of the neoligament, the freedom for flexion and exten-sion, and knee stability. The over the top AM bundle is fixedat 901 and secured with staples at the lateral condyle, while thePL bundle passing through the femoral and tibial tunnel isfixed at 301 and secured with staples or otherwise with atransosseus suture knot, according to the length of the auto-logous tendons.

This technique attempts to reproduce the kinematic effectsof both AM and PL bundle of the ACL with a four-bundlereconstruction (Marcacci et al., 2003a) (Fig. 2).

Associated surgery (Table 2)

Associated pathology noted at the time of surgery included asingle tear of the medial meniscus in 21 cases (11 in singlebundle, 10 in double bundle), a single tear of the lateral me-niscus in 13 (eight in single bundle, five in double bundle), anda tear of both meniscus in 11 (six in single bundle, five indouble bundle). A total of 44 patients (22 in single bundle, 19in double bundle) underwent partial meniscectomy and onlyone case in double-bundle group had the treatment of lateralmeniscus suture by using Fast-Fix system. Grade I–II tears of

Fig. 1. Single bundle plus lateral extra-articular sling.

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the medial collateral ligament (MCL) were associated in ninecases (five in single bundle, four in double bundle) and werenever repaired. There were no significant statistical differencesin the incidence of associated meniscus and chondral injuriesbetween the two groups (b5 0.5).

Post-operative protocol

All patients of both groups underwent the same post-operativerehabilitation protocol, regardless of the presence of asso-ciated injuries. Muscle strengthening exercises were started onthe first post-operative day with isometric quadriceps contrac-tions and progressed to active closed chain exercise. Thepatients were allowed to partially weight bear without a bracefrom the first week. At the same time, isometric and openchain proprioceptive exercises were performed as well as activeand passive full-range motion. Full weight-bearing was al-lowed from the third week. At 1 month, isotonic and closedchain exercises were started. Running was recommended at 2months, and cutting and lateral sports were allowed at 3–4months after surgery depending on their performance level.The criteria to allow sport resumption were isokinetic testswith less than 10% difference between healthy and operatedknee and good firm point at objective clinical evaluation. Thedecision was taken in combination by the surgeon, physicaltherapist and patient.

Patient evaluation

All patients were clinically evaluated pre-operatively and atfinal follow-up, that is the first observation point of a long-term evaluation. For clinical objective evaluation, the IKDCknee examination form (Hefti et al., 1993) was recorded, aswell as subjective evaluation. The functional capability of theknee before surgery and at the observation time point wastested by the Tegner score (Tegner et al., 1986).

The stability of knee joint was evaluated by a KT-2000arthrometer (MEDmetric, San Diego, CA, USA). Injured anduninjured knees were evaluated by performing the 30 lbsanterior drawer test, the manual maximum displacement testand the quadriceps active test.

All evaluations were performed by an independent observer(a surgeon from internal scientific board of our institute) whowas blinded due to the coverage of scars by doilies disposed inthe same manner.

For evaluation of muscle recovery and strength, thigh cir-cumference measurements at 5 and 15 cm proximal to thesuperior patellar apex was used.

Furthermore, the Activity Rating Scale (Marx et al., 2001)and the Psychovitality Questionnaire were tested to evaluaterecovery of sport activity related to the pre-injury activity levelas well as the time to return to sport.

Standard anteroposterior and lateral X-ray projectionwere performed to evaluate the tunnel enlargement accordingPeyrache score (Peyrache et al., 1996) and the degenerativeknee changes according to Ahlback’s score (Ahlback & Ryd-berg, 1980).

Statistical methods

All continuous data were expressed in terms of mean and SDof the mean. To test hypotheses about differences between andamong groups one-way ANOVA test evaluated by monte-carlo method for small samples was performed.

Post hoc power analysis was performed to non-significanttests.

For all tests Po0.05 was considered significant.Statistical analysis was performed using SPSS 7.5 software.

Fig. 2. Double-bundle ACL reconstruction.

Table 2. Associated lesions and surgery

Associated lesions Single bundleplus lateralplasty

Single bundleplus lateralplasty

Medial meniscus tear (b5 0.51) 11 10Lateral meniscus tear (b5 0.7) 8 5Medial1lateral menisci tear (b5 0.5) 6 5Selective meniscectomy 25 19Meniscal suture 0 1Grade I–II MCL tear(no reparation performed) (b5 0.5)

5 4

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Results

IKDC evaluation showed highly satisfactory resultsfor both groups. The double-bundle reconstructiongroup reported a higher percentage of normal knees(A) (86.5%) compared with the single-bundle group(62.9%). Moreover, only in the single-bundle groupthere were patients graded in class C (5.7%), while nopatients in either group resulted in a class D result.These data were significant (P5 0.04). The manualpivot-shift test had a similar trend respect to IKDCform (Table 3).The ROM measurement at final follow-up showed

superposable values, both in passive and in activeROM for the two groups.On the other hand, a higher percentage of patients

with mild harvest site pain was found in the double-

bundle group (8.9%) compared with the single-bundle (2.9%) patients. This data was not statisti-cally significant, but it seems to be a well-definedtrend as it approached statistical significance (P5

0.056; b5 0.6).The subjective evaluation was not significant (Ta-

ble 3).The Tegner score was almost equal in the two

groups (b5 0.7).The side-to-side muscle thigh circumferences at 5

and 15 cm proximal to the superior patellar pole weresimilar for the two groups (b5 0.8 and 0.5, respec-tively) (Tables 4 and 5).Although mean values of KT 2000 were compar-

able in both groups, in double-bundle group nopatient showed laxity higher than 5mm in all tests.In particular, AP displacement at 30 libres andquadriceps active test showed a significantly inferiornumber of patients with more than 5mm side-to-sidedifference for double-bundle group (P5 0.022 and0.036, respectively) (Table 6).The results for the Activity Rating Scale following

ACL reconstruction were higher for double-bundlegroup (12.2) than for single-bundle group (9.6)(P5 0.003), while the pre-op Activity Rating Scaleresults were similar for the two groups (doublebundle: 13.4; single bundle: 12.9; b5 0.8) (Table 5).Regarding the post-operative recovery, although it

is not statistically significantly different (b5 0.8), it isimportant to stress that 100% of double-bundlereconstruction patients were able to return to sportactivity at their same pre-operative level as comparedwith only 91% of single-bundle reconstruction pa-tients. Furthermore, double-bundle patients wereable to return to their previous sport activity in ashorter period of time following reconstruction ascompared with the single-bundle group (3.8 vs 6.4months; P5 0.001) (Table 7).Radiographic evaluation post-operatively revealed

no errors in tibial tunnel and femoral placement andthere were no differences in tunnel enlargement.Moreover, there were no differences regarding ar-thritic degenerative changes related to surgery be-

Table 3. IKDC and manual pivot shift results; P 5 0.04

IKDC class(P 5 0.04)

Single bundleplus lateral plasty

Double bundle

A22 (62.9%) 32 (86.5%)

B11 (31.4%) 5 (11%)

C2 (5.7%) 0 (0%)

D0 (0%) 0 (0%)

Manual pivot shift(b5 0.5)

1 11 111 1 11 1112 0 0 0 0 0

Table 4. Harvest site pain and subjective evaluation

Surgical procedure Single bundleplus lateral plasty

Double bundle

Mild harvest site pain(P 5 0.056)(b5 0.66)

2.9% 8.9%

Subjective evaluation(P 5 0.09)(b5 1)

83.9%(40–100%;SD 5 12.7)

88.4%(70–100%;SD 5 9.1)

SD, standard deviation.

Table 5. Side-to-side muscle thigh circumference 5 and 15 cm proximal to superior patellar pole, tegner score and post-operative activity rating scale


Side-to-side muscle thigh circumference 5 cmproximal to superior patellar pole (b5 0.8)

0.2 cm(min. � 5; max. 2; SD 5 1.3)

0.6 cm(min. � 4; max. 2; SD 5 1.4)

Side-to-side muscle thigh circumference 15 cmproximal to superior patellar pole (b5 0.5)

0.6 cm(min. � 5; max. 4; SD 5 2)

0.6 cm(min. � 4, max. 3; SD 5 1.5)

Tegner score (b5 0.7) 6(1–10; SD 5 2)

6.5(2–9; SD 5 1.5)

Post-operative activity rating scale score (max. 16)(P 5 0.003)(b5 0.8)

9.6(1–14; SD 5 3.5)

12.2(4–16; SD 5 2.6)

min., minimum, max., maximum; SD, standard deviation.


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tween the two groups, although at a relatively shortfollow-up.No hardware removal was necessary in the any of

the patients in either group.In both groups, no graft failure and no complica-

tions due to the surgical procedure were observed.

Discussion

Our study reveals that the double-bundle ACL re-construction results in a significantly higher IKDCscore compared with a single-bundle reconstructionwith extra-articular plasty using two strands ham-string tendons.Although both groups have a high percentage of

satisfactory results, the double-bundle techniqueseems to permit a faster recovery, return to sportsand better global knee performance compared withthe single-bundle reconstruction. In fact, analyzingfunctional parameters as time to resume sport andActivity Rating Scale, patients undergoing the double-bundle ACL reconstruction technique achieved sig-nificantly better results in these categories. In parti-cular, the higher Activity Rating Scale result obtainedin the double-bundle group at final follow-up could berelated to a better rotational stability in high demand-ing sportsmen achieved with this technique.Subjective evaluation, although not significant,

showed a trend to a better result for double-bundletechnique.

On the other hand, with regard to ROM, Tegneractivity score and muscle thigh circumference, thetwo reconstruction techniques were not significantlydifferent.Also objective evaluation using the KT 2000

arthrometer confirmed the results obtained withIKDC, showing a significant higher knee stabilityfor double-bundle technique.In literature, Hamada et al. (2001) and Adachi

et al. (2004) and recently Jarvela (2007) have pro-spectively compared single- and double-bundle tech-niques for ACL reconstruction. At 2 years meanfollow-up, Hamada and Adachi were not able to finda significant difference in clinical outcome, proprio-ceptive performance and objective stability althougha trend was observed for better stability in double-bundle technique, similarly observation of Yasudaet al. (2006).Jarvela has found significantly better stability in

pivot-shift test for double-bundle technique and ahigher rate of graft failure in single-bundle group.Muneta et al. (1999) at a 2-year follow-up found a

significantly higher degree of stability for double-bundle reconstruction, comparing this results to hisprevious series of single-bundle reconstruction. Ourresults are consistent with Yasuda et al. (2006),Muneta et al. (1999) and Jarvela (2007) regardingobjective stability. Moreover, we were able to achievea statistically significant better clinical outcome. Infact, we found a higher percentage of excellentresults, a higher functional capability and a faster

Table 6. KT2000 30 lbs anterior drawer test, manual maximum displacement and quadriceps activity test


Mean value o3 mm 3–5 mm 45 mm Mean value o3 mm 3–5 mm 45 mm

KT2000 30 lbs anteriordrawer test

(P 5 0.022)(b5 0.67)

1.7 (min. � 4;max. 10; SD 5 3.2)

25 (71.4%) 5 (14.3%) 5 (14.3%) 1.6 (min. � 3;max. 5; SD 5 2)

26 (70.3%) 11 (29.7%) 0 (0%)

KT2000 manual max.displacement (b5 0.8)

0.7 (min. � 4;max. 9; SD 5 2.4)

28 (80%) 5 (14.3%) 2 (5.7) 1.1 (min. � 3;max. 5; SD 5 1.9)

30 (81.1%) 7 (18.9%) 0 (0%)

KT2000 quadricepsactive test

(P 5 0.036)(b5 0.64)

1.5 (min. � 7;max. 8; SD 5 3.5)

21 (60%) 8 (22.9%) 6 (17.1%) 1 (min. � 5;max. 5; SD 5 3)

27 (73%) 10 (27%) 0 (0%)

min., minimum, max., maximum.

Table 7. Return to sport activity


Return to sport activity(b5 0.8)

Yes No Yes No32 (91%) 3 (9%) 37 (100%) 0 (0%)

Time to recover sportactivity (P 5 0.001)

Mean time o4 months 4–6 months 46 months Mean time o4 months 4–6 months 46 months6.4 months(3–24)

6 (18.8%) 18 (56.2%) 8 (25%) 3.8 months(3–8)

19 (51.4%) 14 (37.8%) 4 (10.8%)

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recovery to normal knee function in our patientsundergoing double-bundle ACL reconstruction.The differences in our results when compared with

other series could be related to the evaluation meth-ods and statistical tests used for data analysis orgeographic differences in patient populations andgoals. In fact, the double-bundle group showed sig-nificantly higher pre-operative Psychovitality Ques-tionnaire results, that could represent an enhancedmotivation, taking to a better final result. Moreover,every double-bundle technique also has its owntechnical features that could affect the final clinicaloutcome. In fact, a large variety of different surgicaltechniques have been proposed for double-bundleACL reconstruction in literature. These procedurescan use a single- or double-tibial tunnel and, morefrequently, a double femoral tunnel.One of the key issues in double-bundle reconstruc-

tion techniques is the correct placement of the fe-moral tunnels. Yasuda et al. (2006), Muneta et al.(1999) and Yamamoto et al. (2004) have studied theimportance of tunnel location, most of all regardingthe postero-lateral bundle, for which the correct posi-tioning is extremely hard to achieve.In the presented technique, the PL bundle is placed

in a femoral tunnel that is drilled in the lower andanterior part of the femoral native ACL insertion asthe normal PL bundle should be (Giron et al., 2006).The risk of malpositioning the femoral tunnel is mini-mized by placing the AM bundle over the top and thesurgeon can easily find the correct placement of PLfemoral tunnel. Further, this technique avoids the riskof PCL impingement (Lawhorn & Howell, 2003) anddoes not require a wide notchplasty for a betterarthroscopic visualization of femoral tunnel placement.In this way, the surgical morbidity for the patient

and surgical time are both minimized and should arevision surgery be necessary, it can be performedwithout excessive technical difficulties.Certainly, the use of a non-anatomic over-the-top

passage could be a limitation of these procedures andfurther investigations with the use of double femoraltunnels could be interesting. The double-bundle ACLsurgical techniques become more demanding when adouble femoral tunnel has to be performed, and, asstated by Harner and Poehling (2004), there could bean increased risk of intra-operative complicationsdue to the higher technical difficulty of the proce-dure, making revision surgery even more difficult toperform. In the double-bundle technique reportedhere, the tibial hamstring insertion is left intact,preserving the tendons’ vascular and neurologicalsupply (Zaffagnini et al., 2003) which the authors be-lieve can promote a faster neoligamentization pro-cess. Schultz et al. (1984) has described the presenceof mechanoreceptors in native ACL structure andhas suggested their proprioceptive function. A faster

recovery of somatosensory function, related to betterkinematic performance and more anatomic repro-duction of native ACL, could possibly explain thebetter results of the functional parameters found inthe double-bundle group post-operatively.The significant differences observed in this study

cannot be related to the weakness of the graft in thesingle bundle plus external augmentation technique,which has demonstrated highly satisfactory results atlong-term follow-up (Marcacci et al., 2003a). More-over, compared with four strands hamstrings andpatellar tendon techniques, double-bundle ACLreconstruction has shown at 5 years superposableresults regarding objective stability and knee function(Zaffagnini et al., 2006). We believe that extra-articu-lar augmentation reduces the stress on the intra-articular portion of the graft, allowing a better inte-gration and reducing the risk of lesions to the neo-ACL, representing a restraint to peripheral rotations.In conclusion, the double-bundle technique for

ACL reconstruction described in this paper hasdemonstrated significantly better subjective, objec-tive and functional results compared with a single-bundle reconstruction with extra-articular plasty at aminimum 3-year follow-up.However, many variables can affect the final clin-

ical outcome and this fact could explain the differentresults reported in literature. Many aspects of thisdemanding procedure have still to be completelyclarified and the relative importance of these aspectsunderstood before it may be considered as thestandard of care and can be widely accepted as theoptimal surgical procedure for ACL reconstruction.For further evidence of the various factors affect-

ing ACL double-bundle reconstruction, a quantita-tive intra-operative assessment of ACL kinematicscould be very helpful.

Perspectives

In our experience, double-bundle ACL reconstruc-tion has demonstrated a slightly higher knee stabilityand most of all a faster recovery of sport activitycompared with the single bundle plus lateral Plastytechnique. Our findings are consistent with the trendsobserved in Hamada et al. (2001), Adachi et al.(2004) and Yasuda et al. (2006).

Key words: ACL reconstruction, arthroscopy, doublebundle, surgical technique, comparative study.

Acknowledgements

The research development was in collaboration with March-eggiani Muccioli Giulio Maria, MD and Bassini Silvia,Laboratorio di Biomeccanica, Istituti Ortopedici Rizzoli,Bologna, Italy.


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