Prospective randomized comparison of anatomic single- and double-bundle anterior cruciate ligament reconstruction

KNEE

Prospective randomized comparison of anatomic single-and double-bundle anterior cruciate ligament reconstruction

Yan Xu • Ying-fang Ao • Jian-quan Wang •

Guo-qing Cui

Received: 14 May 2012 / Accepted: 14 January 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose To determine if anatomic double-bundle anterior

cruciate ligament (ACL) reconstruction is superior to

anatomic single-bundle reconstruction in restoring the

stabilities and functions of the knee joint.

Methods A prospective randomized clinical study was

done to compare the results of 32 cases of anatomic single-

bundle ACL reconstruction and 34 cases of anatomic

double-bundle ACL reconstruction with average follow-up

of 16.3 ± 3.1 months. Tunnel placements of all the cases

were measured on 3D CT. Clinical results were collected

after reconstruction; graft’s appearance, meniscus status

and cartilage state under arthroscopy were compared and

analysed too.

Results Tunnel placements, confirmed with 3D CT, were

in the anatomic positions as described in literature both in

SB and DB group. No differences were found between SB

and DB groups in clinical outcome scores, pivot shift test

and KT 1000 measurements (average side-to-side differ-

ence for anterior tibial translation was 0.7 mm in SB group

and 1.0 mm in DB group). More than 70 % of the single-

bundle graft and AM bundle graft in DB group appeared

excellent, but only 44.1 % of PL bundle grafts in DB group

were excellent and 11.8 % were in poor state. No new

menisci tear was found either in SB or DB group, however,

in DB group cartilage damages in medial patella-femoral

joint occurred in 38.2 % cases. This rate was significantly

higher than in the SB group which is only 9.3 %.

Conclusion Both single- and double-bundle anatomic

ACL reconstruction can restore the knee’s stability and

functions very well. However, more incidences of poor PL

status and medial patellar-femoral cartilage damage may

occur in double-bundle ACL reconstruction.

Level of evidence Randomized controlled trial, Level I.

Keywords Anatomic � Single bundle � Double bundle �Anterior cruciate ligament � Arthroscopic evaluation

Introduction

Anterior cruciate ligament (ACL) reconstruction has been

the standard surgical treatment for ACL rupture for the last

three decades [7, 18]. Although good to excellent results

have been reported widely, the success rates vary between

69 and 95 % [7, 9, 18, 36] which is still far from excellent.

Many factors, such as the type of the graft, the fixation

device, the graft size, or the post-operative rehabilitation

protocol, are all thought to have impact on final results.

Many recent studies are focused on the anatomy of the ACL

and thus fostered the interest in reconstructing the ACL in

anatomic fashion [15, 27, 29, 30]. Anatomic ACL recon-

struction is believed to be the key to the success of this

operation and non-anatomic tunnel placement may result in

abnormal knee kinematics, graft impingement or stretching

of grafts. Anatomic and biomechanical studies have shown

that the ACL consists of two functional bundles [10, 13].

Laboratory and clinical studies [2, 16, 19, 33, 35] have also

demonstrated that double-bundle ACL reconstruction can

better restore the stability of the knee compared to single-

bundle ACL reconstruction. However, in most of the stud-

ies, an anatomic double-bundle technique was compared

with a single-bundle technique using traditional transtibial

tunnel positions. While some authors believed that transti-

bial femoral tunnel drilling does not reach the anatomic site

Y. Xu � Y. Ao (&) � J. Wang � G. Cui

Institution of Sports Medicine, Peking University Third Hospital,

49 North Garden Rd, Hai Dian District, Beijing 100191, China

e-mail: [email protected]

123

Knee Surg Sports Traumatol Arthrosc

DOI 10.1007/s00167-013-2398-y

of ACL insertion, but at a high tunnel position [1, 6],

however, to reconstruct an anatomic ACL the tunnel posi-

tions should be within the anatomic insertion site.

In this study, two groups of patients were compared, one

with anatomic single-bundle ACL reconstruction and the

other with double-bundle. The purpose of this study is to

determine if anatomic double-bundle reconstruction is

superior to anatomic single-bundle reconstruction in regard

to providing knee stability. Our hypothesis is that anatomic

single-bundle ACL reconstruction is equivalent to the

anatomic double-bundle ACL reconstruction in controlling

the knee stability but with much simpler techniques.

Materials and methods

From December 2009 to December 2010, a prospective

randomized clinical study was carried out to compare the

results of anatomic single- and double-bundle ACL recon-

struction. Ethical approval was obtained from the institu-

tional review board of the university, and 80 patients were

randomized into 2 groups before the operation: single-bun-

dle group (SB group; n = 40) and double-bundle group (DB

group; n = 40). A computer-generated randomization was

done with inclusion criterion of primary ACL rupture in

adult patients and exclusion criteria of multi-ligamentous

injuries, severe osteoarthritis or contralateral ACL-deficient

knee. Patients with concomitant reparable meniscus injuries

were also excluded, because of different rehabilitation pro-

tocol required. Pre-operatively, all patients received pre-

operative examination, including Lachman, anterior drawer,

pivot shift testing and were also tested with KT-1000

arthrometer with knee flexion of 30 and 90�, respectively, at

134 N and manual maximum force (MEDmetric, San Diego,

California, USA). All patients were also evaluated with the

IKDC subjective score, Lysholm score and Tegner score.

Standard radiographs and 3D CT were taken for all patients

after the operation to check the tunnel positions. All patients

were educated beforehand and they agreed to come back to

remove the hardware at least 1 year after the operation and

arthroscopic evaluation was taken simultaneously. By the

end of study, 8 patients in the SB group and 6 in the DB group

could not be followed for the latest follow-up. So there were

32 subjects of the SB group and 34 subjects of DB group

included in this study with a 16.3 ± 3.1 (12–36) months’

follow-up. There were no demographic differences between

the 2 groups and the time period between the first trauma and

the operation was similar as displayed in Table 1.

Operative technique

The semitendinosus and gracilis tendons were harvested

and graft preparation was made either in single-bundle or

in double-bundle. Average diameter of single-bundle graft

was 7.3 ± 0.5 cm (7–8), anterior medial graft was

6.9 ± 0.5 cm (6–8) and posterior lateral graft was

5.6 ± 0.5 (5–6 cm). Before the ACL reconstruction, any

meniscal or chondral injuries were treated first.

Anatomic double-bundle reconstruction

AM and PL tunnel on femur were drilled based on the

identified insertion sites through the accessory medial

portal. In chronic cases, the tunnels were drilled just below

the resident ridge and anterior the post-cartilage edge

which was taken as the insertion site as described in lit-

erature [12]. AM and PL Tibial tunnels were drilled with

the tibial tunnel guide, PL graft was first put through the PL

tunnel and AM passage was followed through the AM

tunnel, the button was flipped in the standard fashion to

achieve femoral fixation of each graft. At first, AM bundle

graft was fixed with a bio-absorbable interference screw in

conjugation with a staple and was manually tensioned with

the knee in 60� of flexion under posterior drawer force;

then the PL bundle was also fixed with a bio-absorbable

interference screw and a staple and was manually tensioned

with the knee in 0� also under a manual posterior drawer

force.

Anatomic single-bundle reconstruction

The procedure was similar to anatomic double-bundle

reconstruction. The femoral tunnel was also created

through the accessory medial portal, but the centre of the

tunnel was placed in the middle of the insertion site. Button

was utilized for femoral fixation, and bio-absorbable

interference screw in conjugation with a staple was utilized

in tibial side with the knee at 30� of flexion under a forced

posterior drawer load.

Rehabilitation

The knee was kept in full extension in a brace for a couple

of days. Same standard post-operative rehabilitation pro-

gramme was followed both in SB and in DB group, full

weight bearing was allowed in 4 weeks, and full range of

motion was obtained within 8 weeks. Running was allowed

only after 4 months, but contact sports were not recom-

mended until 8 months after the operation.

Evaluation of the tunnel placement in 3D CT

3D CT and standard X-rays imaging were performed after

the operation.

Measurements of tunnel placements were performed

using the digital radiography system (PACS, Siemens) with


123

the built-in digital rule. On femoral side, a snapshot of the

medial–lateral (M–L) view of the lateral femoral condyle

was obtained using the method described by Lertwanich

et al. [22]. The medial femoral condyle was virtually

removed at the highest point of the anterior aperture of the

inter-condylar notch to generate the view of the lateral

femoral condyle. Then, the measurements were taken on

this snapshot based on the quadrant method described by

Bernard et al. [8] as following:

The femoral length was measured as the distance from

the most posterior contour of the lateral femoral condyle

parallel to the inter-condylar notch roof, and femoral height

was measured as the perpendicular distance from the inter-

condylar notch roof to the deepest borders of the condyle.

Centres of femoral tunnels were measured and normalized

to the ratio of posterior–anterior length and ratio of prox-

imal–distal height of the lateral femoral condyle, respec-

tively (Figs. 1, 2).

On tibial side, the measurements were taken on the plain

radiograph in order to compare with the results found in

literature. Tibial tunnel with respect to the tibial plateau

along the Amis and Jakob line (Tibia%) was measured [5]

(Fig. 3), and tibial width was measured using the AP

radiograph from the most medial point of the tibial plateau

to the most lateral point of the tibial plateau. And, the result

was normalized to the ratio of medial–lateral distance on

the tibial plateau.

All the measurements were carried out by one observer,

who repeatedly measured half of the objects approximately

6 months after the initial measurements to evaluate the

intra-observer reliability. The initial measurements were

not accessed while the measurements were repeated to

make sure of independence among the measurements.

Clinical follow-up

All patients were examined post-operatively after 1, 3, 6,

and 12 months, and they were asked to come back for

removal of the hardware at least 1 year after the operation.

In the final visit, an arthroscopic evaluation was performed

and the status of the graft, the meniscus and the cartilage

were recorded and compared with that of the first opera-

tion. The classification system depicted by Kondo and

Yasuda [20] was utilized to evaluate the graft; total score of

4 points was defined as excellent, 2 or 3 points as fair, and

0 or 1 point as poor.

Clinical outcomes were also assessed including range of

motion, joint laxity testing which was evaluated with KT

1000 (MedMetric Inc., USA), pivot shift test, Lachman

test, IKDC subjective score, Lysholm score and Tegner

score.

Statistical analysis

Statistical study was carried out with the SPSS statistical

analysis package (version 13.0, SPSS Inc., USA), descrip-

tive statistics of continuous variables were collected

including age, length of follow-up, and average tunnel

Table 1 Demographic data of the two groups

Gender (M/F) AGE (years) Height (cm) Weight (kg) Time from injury to surgery (months)

SB 25/7 33.3 ± 12.8 171.7 ± 6.6 71.0 ± 2.6 24.5 ± 58.5

DB 24/10 30.2 ± 7.7 172.3 ± 8.9 72.1 ± 12.1 21.5 ± 33.9

Fig. 1 a Femoral length (FL)

represents the distance from the

most posterior contour of the

lateral femoral condyle parallel

to the inter-condylar notch roof

femoral height (FH) represents

the perpendicular distance from

the inter-condylar notch roof to

the deepest borders of the

condyle. Femoral tunnel

position on 3D CT is measured

according the quadrant method.

b Red points represent all the

femoral tunnel positions of SB

group


123

positions. The calculations between the differences of

means were done by analysis of variance (ANOVA) and an

independent sample t test. Those of the frequencies were

done by the 92 test. The significance level was set at

P \ 0.05.

Before the investigation, the sample size was estimated

on the basis of the hypothesis that there was no difference

between the two groups in clinical scores. The expected

improvement between control and test group would be

10 %. For a t test at a = 0.05 and to achieve 0.8 power, a

sample size of at least 32 subjects were needed.

Intra-class correlation coefficients and the standard error

of measurement were used to evaluate the intra-observer

reliability.

Results

Clinical outcomes

The average follow-up was 16.3 ± 3.1 (12–36) months,

and the clinical results of last follow-up are manifested in

Tables 2, 3. At the latest follow-up, there was no re-rupture

case observed in all the subjects.

The stability of the knee and the clinical scores were

significantly improved after the operation both in single-

and double-bundle group, but no difference was observed

between the two groups.

Tunnel placement

In single-bundle group, the average centre of the femoral

tunnel was located at 29.0 ± 4.0 % of the femoral length

and at 36.4 ± 6.5 % of the femoral height.

Femoral tunnel positions of all the cases in SB group are

manifested in Fig. 1.

The centre of the tibial tunnel was located at

36.7 ± 5.6 % of tibial plateau along the Amis and

Jacob line and 45.0 ± 1.9 % of the tibial width,

respectively.

In double-bundle group, the centres of the AM and PL

bundles’ femoral tunnels were located at 26.3 ± 5.4 and

39.8 ± 7.5 % of the femoral length, and at 30.3 ± 9.0 and

49.5 ± 10.1 % of the femoral height, respectively.

Femoral positions of all the cases in DB group are

manifested on Fig. 2.

The centres of the AM and PL tibial tunnels were

located at 31.1 ± 5.9 and 45.1 ± 6.1 % of tibial plateau

along the Amis and Jacob line, and at 41.5 ± 2.8 and

46.3 ± 3.0 % of the tibial width, respectively.

Fig. 2 a Femoral tunnels of

double-bundle ACL

reconstruction are measured on

3D CT in similar way. b Bluepoints represent all the positions

of AM, and Red points represent

all the positions of PL tunnels of

DB group

Fig. 3 Tibial tunnels with respect to the tibial plateau along the Amis

and Jakob line(S) (Tibia%) are measured Line P rests on the medial

tibial plateau, while line S is parallel to P, passing through the

posterior corner of the shelf


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Arthroscopic evaluation

No big complications were observed during the follow-up.

According to Kondo and Yasuda’s classification system,

among the anatomic SB group 78.1 % cases showed

excellent graft status.

In double-bundle group, 73.5 % of the cases showed

excellent AM bundle, but only 44.1 % cases showed

excellent status PL bundle (Table 4). There was no corre-

lation found between the clinical outcomes and the graft

status either in SB or DB group while comparing excellent

and fair results. Concomitant meniscus injuries of both

groups are presented in the Table 5. Cases with cartilage

lesions were counted and listed in Table 6 and were more

severe than grade II in different part of the knee joint

before and after the reconstruction.

In single-bundle group, there were 4 cases (12.5 %) with

new cartilage lesions, while in double-bundle group there

were 13 cases (38.2 %) with new cartilage lesions which

was significantly higher than SB group (P = 0.009). The

increased lesions were all in medial patellar-femoral joints.

There was no difference found in the cartilage lesions

cases with excellent PL appearance (7/20) and cases with

fair or poor PL appearance (6/14) in DB group.

Intra-observer reliability

Intra-observer reliability was greater than 0.8 for all of the

radiographic measurements, the corresponding standard

error of measurement ranged from 1.5 to 3.9 %.

Discussion

The most significant finding of the present study was that

double-bundle ACL reconstruction did not show any

advantages over single-bundle ACL reconstruction either

in clinical outcomes or in knee stability. In addition, the

rate of cartilage injury incurred during the operation in the

DB group was significantly higher than in the SB group.

Table 2 Clinical results of the SB and DB groups

KT 30 (mm) KT 90 (mm) Lysholm IKDC Tegner

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

SB 7.0 ± 2.3 0.7 ± 0.8 3.9 ± 2.3 0.4 ± 0.5 59.8 ± 20.9 82.2 ± 12.9 46.4 ± 1.5 82.5 ± 15.4 3 (2–4) 6 (4–7)

(n = 32) P \ 0.001 P \ 0.001 P = 0.034 P = 0.005 P = 0.002

DB 5.6 ± 1.7 1.0 ± 0.9 3.2 ± 0.8 0.5 ± 0.1 67.8 ± 18.8 91.0 ± 11.6 49.1 ± 9.7 81.1 ± 9.4 3 (1–5) 6 (3–8)

(n = 34) P \ 0.001 P \ 0.001 P = 0.014 P \ 0.001 P \ 0.001

P value

(S vs B)

n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.

Table 3 Result of pivot shift of the SB and DB groups

0 1 2 3

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

Pre-

Operative

Post-

Operative

SB 9 30 17 2 5 0 1 0

(n = 32) P \ 0.001 P \ 0.001

DB 9 32 19 2 6 0 0 0

(n = 34) P \ 0.001 P \ 0.001

P value

(S vs B)

n.s.

Table 4 Graft status

Graft status SB (n = 32) DB (n = 34)

AM bundle PL bundle

Excellent 25 (78.1 %) 25 (73.5 %) 15 (44.1 %)

Fair 7 (21.9 %) 9 (26.5 %) 15 (44.1 %)

Poor 0 0 4 (11.8 %)


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Many factors have impact on the outcomes of ACL

reconstruction, but accurate tunnel position is the key to the

successful operation. Anatomic ACL reconstruction has

gained popularity in recent years; many studies showed that

anatomically reconstructed ACL graft could restore the knee

function better than non-anatomic graft [17, 27, 30, 38]. To

anatomically reconstruct the ACL, the placement of the

femoral or tibial tunnel should be within the original inser-

tion site area. Many cadaver studies were carried out to find

the average position of the original footprints of ACL

insertion on femoral side, quadrant method in radiograph

was widely used to evaluate the tunnel position [11, 38]. In

live cases, true lateral radiograph of knee cannot always be

obtained; minor rotation of the knee will impair the accuracy

of the measurement. Compared to plain radiograph, three-

dimensional CT of knee joint can locate the tunnel position

more precisely and it makes the tunnel evaluation more

accurate and reliable [14].

In this study, 3D CT was used to evaluate the femoral

tunnel position according to Forsythe B’s method [14]. In

their study, the reconstruction of double-bundle ACL was

on the original insertion sites in eight cadaver knees and

utilized 3D CT to determine the tunnel positions in fem-

oral side with the quadrant method. AM and PL tunnels

were measured at 21.7 and 35.1 % from the proximal

condylar surface (parallel to the Blumensaat line), and at

33.2 and 55.3 % from the notch roof (perpendicular to the

Blumensaat line). In our study, the double-bundle group’s

AM and PL bundle were located at 26.3 and 39.8 % from

the proximal conlylar, and at 30.2 and 50 % from the

notch roof, respectively, which were quite consistent with

the previous anatomic studies [11, 14, 38]. In double-

bundle group, the centres of AM and PL tunnels were

located at 31.1 and 45.1 % along the Amis and Jakob line,

which were quite consistent with Zantop’s cadaver’s study

[38]. In his study, the native AM and PL bundles were

located at 30 and 44 % of the Amis and Jakob line,

respectively.

From these measurements, we can see that AM and PL

tunnel positions in our case were matched with the previ-

ous positions of the insertions sites both in femoral and

tibial side. We thus concluded that the operation techniques

and the references we used during the DB reconstruction

can reproduce the ACL graft in an anatomic position.

In the single-bundle group, the femoral tunnel’s centre

was located at 29.0 % from the proximal condylar surface

(parallel to the Blumensaat line) and at 36.4 % from the

notch roof (perpendicular to the Blumensaat line). This

position was located between the anatomic positions of

AM and PL bundle. In tibia side, our single-bundle tibia

tunnel’s centre was located at 36.7 % along the Amis and

Jacob line, which was also located between the AM and PL

bundle’s insertion sites according to the previous anatomic

study, so the tunnel positions in our single-bundle ACL

were also within the original insertion area.

Many papers compared single- and double-bundle ACL

reconstruction with controversial conclusions, for example,

in Aglietti’s level 1 study [3], 70 patients were randomized

to receive a single-bundle or double-bundle reconstruction.

In the 2 year minimum follow-up, DB ACL reconstruc-

tions showed better VAS, knee laxity and final objective

IKDC scores than SB. Kondo et al. [21], in their pro-

spective comparative study of 328 patients, showed that the

double-bundle group had significantly better results in

anterior laxity and pivot shift than single-bundle group.

Yasuda et al. [35] prospectively compared anatomic

double-bundle, single-bundle, and non-anatomic double-

bundle procedures; the results showed that the anatomic

double-bundle were significantly better than single-bundle

on anterior–posterior and rotation stability. In a recent

study, Hussein et al. [18] compared conventional single-

bundle, anatomic single-bundle, and anatomic double-

bundle ACL reconstruction in 281 cases. In their study,

they separated cases of anatomic single-bundle ACL

reconstruction from conventional single-bundle and found

that anatomic double-bundle ACL reconstruction was sig-

nificantly superior to conventional single-bundle ACL

reconstruction and better than anatomic single-bundle

reconstruction. Obviously, anatomic single-bundle recon-

struction was superior to conventional single-bundle

reconstruction. Park et al. [25] compared the clinical results

Table 5 Meniscus status

Injured medial meniscus

(cases)

Injured lateral meniscus (cases)

Pre-

Operative

Post-

Operative

Pre-Operative

(cases)

Post-

Operative

SB 18 0 12 0

DB 12 0 14 0

Table 6 Cartilage status

Patellar Trochlea Medial condyle Medial plateau Lateral condyle Lateral plateau

Pree Post Pree Post Pre Post Pre Post Pre Post Pre Post

SB 9 9 6 9 9 9 12 15 9 9 9 9

DB 4 10 4 14 14 14 12 12 10 10 10 10


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of arthroscopic single-bundle and double-bundle ACL

reconstruction in 113 patients; they found that double-

bundle reconstruction of the ACL showed no differences in

stability results or any other clinical aspects and in terms of

patients’ satisfaction. Song et al. [31] did a prospective

study of ACL reconstruction using double-bundle and

single-bundle techniques; their results showed that the two

methods were similar in terms of clinical outcomes and

post-operative stabilities after a minimum of 2 years of

follow-up, although double-bundle ACL reconstruction

produced better intra-operative stabilities than single-

bundle. Among those studies, the exact tunnel positions

were seldom manifested and not specified whether the

tunnel placement was truly at anatomic position. In our

study, all the tunnels were checked with 3D CT, and the

placements were anatomic both in single-bundle and dou-

ble-bundle groups as described above.

Our study did not find any difference between SB and DB

group either in clinical outcomes or in anterior–

posterior and rotational stabilities. Although theoretically

double-bundle ACL graft resembles more close to normal

anatomy, single-bundle graft produced clinical outcomes

with the same satisfactory level. Sastre et al. [26] did a ran-

domized prospective study with 20 patients in both single-

and double-bundle groups; they concluded that placing the

femoral tunnel in a more horizontal position in the single-

bundle group produced similar rotatory and anteroposterior

laxity to that obtained in the double-bundle group. In our

opinion, the more horizontal position was closer to the ana-

tomic position. Consistent with their study, our study showed

that the anatomic single-bundle graft can restore the normal

knee’s function just like the anatomic double-bundle graft.

These should be more obvious in Asian patients for they

often have smaller knees than white counterpart [37]. For

Asian people, an accurate single-bundle tunnel could have

occupied majority of the original insertion site area of the

ACL and can provide enough stability.

Kondo and Yasuda [20] performed a prospective eval-

uation of 132s-look arthroscopies performed on 178 knees

that underwent anatomic double-bundle ACL reconstruc-

tion. Otsubo et al. [24] evaluated sixty-eight second-look

arthroscopies and similarly, AHn et al. [4] retrospectively

studied 37 knees that underwent second-look arthroscopy

after double-bundle ACL reconstruction. Compared to their

studies, the status of AM bundle in our double-bundle

group matches their observation; more than 70 % of the

AM grafts were in excellent condition and there was no

rupture observed, however, our results showed a more

inferior status of PL graft. Kondo [20] and Yasuda reported

75.8 % excellent, 21.2 % fair and 3.0 % poor appearance

of PL grafts; Otsubo et al. [24] reported 11 % of the PL

grafts showed substantial damage around the femoral tun-

nel aperture. In AHn et al. [4] study, 64.9 % of PL grafts

were found in excellent status, 18.9 % in fair and 16.2 % in

poor appearance. In our study, only 44.1 % PL grafts

showed excellent status, and 11.8 % were in poor appear-

ance. Kondo and Yasuda [20] and Yagi et al. [34] believed

that posterolateral bundle was at higher risk of failure

because more tension is applied to the posterolateral graft

at full knee extension. Unlike AM bundle graft, PL bundle

is not an isometric graft, it undergoes greater length change

for it slackens as the knee flexes [39]. The change in length

will impair PL bundle’s total remodelling process. Among

Asian people usually a small size of PL graft was applied,

which was also a possible reason for poor look of PL under

abrasion. When we reviewed our double-bundle ACL

reconstruction techniques, we first fixed AM with the knee

in 60� of flexion under posterior drawer force, under this

fixation the knee had already been reduced, and PL bundle

was then fixed with the knee in 0 degree once more under a

manual posterior drawer force. The double posterior force

may excessively load the PL bundle to an overloaded sta-

tus. Under these circumstances, the PL graft may easily

sustain elongation and cause partial rupture and poor

remodelling.

Stabilities of all the cases were restored satisfactorily;

KT 1000 measurements and pivot shift test all improved

significantly both in single- and double-bundle group. The

fact that no new meniscus injuries were found in arthro-

scopic evaluation was also in line with the knee’s stability

after the operation. The most unexpected finding in this

study was the cartilage status during the second-look

arthroscopic evaluation, in double-bundle group there were

38.2 % cases with new cartilage lesions which was sig-

nificantly higher than in the SB group, and the increased

lesions were all in medial patellar-femoral joints. It has

been observed that ACL-deficient knee could lead to

patellar-femoral damage. Oksman et al. [23] reviewed 250

cases with ruptured ACL and found patellar cartilage injury

in 28.8 % cases, and the time period from the first injury to

the reconstruction was significantly correlated with aggra-

vation of these lesions which involved the lateral facet

area. So the medial patellar-femoral cartilage injuries in

our study were quite different from the damage incurred

from the natural history of the ACL-deficient knee. In our

case, maybe ACL reconstruction restored not only the

stability but also caused some adverse impact on the

patellar-femoral joint. Shin et al. [28] utilized magnetic

resonance image-based 3-dimensional patellofemoral knee

models showed that ACL injuries change patellofemoral

kinematics including patellar tilt and patellar lateral

translation, but ACL reconstruction enlarged the patel-

lofemoral contact area and restored normal contact area.

Tajima et al. [32] tested on 7 cadaveric knees and also

found that ACL deficiency resulted in an increase in the

lateral PF contact pressure; anatomic DB ACL


123

reconstruction more precisely restored normal PF contact

area and pressure than non-anatomic SB ACL reconstruc-

tion. In our study, the double-bundle grafts were all in

anatomic positions as described earlier, it was supposed to

restore the knee’s biomechanics properties more precisely

to normal than single-bundle graft. The undesired results

may also were caused by the fixation method that we used.

The second time posterior drawer force when PL was fixed

seemed to produce an over tension on PL which not only

influenced the remodelling process but also changed the

knee’s biomechanics especially in patellofemoral joint, and

this could lead to cartilage damage. Although in single-

bundle group, there were also new manifested cartilage

damages, however, the incidence was quite lower than

other studies [4]. We may conclude that anatomic single-

bundle ACL restored the knee’s normal biomechanics

pretty well. Although there were significant differences in

cartilage damage between the two groups, however, clini-

cal comparison didn’t show the correlation. The reasons

may be that the cartilage injuries were not serious enough

and/or the recovery period after the surgery was not long

enough. Actually, from what we found in this study, we

recommend no posterior force should be applied in PL

fixation especially after AM fixation has been done. Further

clinical and laboratory studies need to be done to prove it.

There are some limitations in this study. First, we used

pivot shift test as the method to evaluate the rotational

stability; although no difference was found, but in our

opinion, the sensitivity of the pivot shift test is not high and

it is a subjective test which is prone to inter-examiner

variation. A more objective clinical test needs to be applied

to reflect the true functions of the knee. Second, although

arthroscopic observation is a reliable and direct way to

evaluate the knee’s status, the surgeon who performed the

primary reconstruction also did the second-look arthros-

copy evaluations which may produce a bias. In our study

though, this bias was minimized by manual evaluation on

the recorded data. Third, the potentially improper step of

the double posterior force applied in PL fixation, which

was not proven by biomechanical experiment yet.

Clinical relevance of this study is that double-bundle ACL

reconstruction may not bring better outcomes as we have

expected. Although theoretically, it could make the graft

more close to the anatomic status, but the more complicated

techniques also increase the chances of mistakes. Since

anatomic single-bundle ACLR could lead to the similar good

results, it should be the main technique we stick to at present.

Conclusion

Patients with the anatomic ACL reconstruction can obtain

satisfying clinical outcomes both in SB and DB groups and

no differences were found. Undesired PL bundle abrasion

and increased medial patellofemoral cartilage damage may

happen in double-bundle ACL reconstruction.

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Prospective randomized comparison of anatomic single- and double-bundle anterior cruciate ligament reconstruction