Anatomic single- versus double-bundle ACL reconstruction: a meta-analysis

KNEE

Anatomic single- versus double-bundle ACL reconstruction:a meta-analysis

Neel Desai • Haukur Bjornsson • Volker Musahl •

Mohit Bhandari • Max Petzold • Freddie H. Fu •

Kristian Samuelsson

Received: 19 October 2013 / Accepted: 30 November 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose To determine whether anatomic double-bun-

dle anterior cruciate ligament (ACL) reconstruction

compared to anatomic single-bundle ACL reconstruction

more effectively restored antero–posterior (A–P) laxity,

rotatory laxity and reduced frequency of graft rupture.

Our hypothesis was that anatomic double-bundle ACL

reconstruction results in superior rotational knee laxity

and fewer graft ruptures due to its double-bundle tension

pattern, compared with anatomic single-bundle ACL

reconstruction.

Methods An electronic search was performed using the

PubMed, EMBASE and Cochrane Library databases. All

therapeutic trials written in English reporting knee kine-

matic outcomes and graft rupture rates of primary anatomic

double- versus single-bundle ACL reconstruction were

included. Only clinical studies of levels I–II evidence were

included. Data regarding kinematic tests were extracted

and included pivot-shift test, Lachman test, anterior drawer

test, KT-1000 measurements, A–P laxity measures using

navigation and total internal–external (IRER) laxity mea-

sured using navigation, as well as graft failure frequency.

Results A total of 7,154 studies were identified of which

15 papers (8 randomized controlled trials and 7 prospective

cohort studies, n = 970 patients) met the eligibility crite-

ria. Anatomic ACL double-bundle reconstruction demon-

strated less anterior laxity using KT-1000 arthrometer with

a standard mean difference (SMD) = 0.36 (95 % CI

0.214–0.513, p \ 0.001) and less A–P laxity measured

with navigation (SMD = 0.29 95 % CI 0.01–0.565,

p = 0.042). Anatomic double-bundle ACL reconstruction

did not lead to significant improvements in pivot-shift test,

Lachman test, anterior drawer test, total IRER or graft

failure rates compared to anatomic single-bundle ACL

reconstruction.

Conclusion Anatomic double-bundle ACL reconstruction

is superior to anatomic single-bundle reconstruction in

terms of restoration of knee kinematics, primarily A–P

laxity. Whether these improvements of laxity result in

long-term improvement of clinical meaningful outcomes

remains uncertain.

Level of evidence II.

Keywords Anterior cruciate ligament � ACL �Reconstruction � Single-bundle � Double-bundle �Anatomic � Meta-analysis

Introduction

Anterior cruciate ligament (ACL) injuries can lead to long-

term functional deficits of knee function, often significantly

limiting the patients’ partaking in sporting activities, par-

ticularly those involving rapid changes of direction and

pivoting. One of the goals of ACL reconstruction is the

N. Desai � H. Bjornsson � K. Samuelsson (&)

Department of Orthopaedics, Sahlgrenska University Hospital,

431 80 Molndal, Sweden

e-mail: [email protected]

V. Musahl � F. H. Fu

Department of Orthopaedic Surgery, University of Pittsburgh,

Pittsburgh, PA, USA

M. Bhandari

Division of Orthopaedic Surgery, Department of Surgery,

McMaster University, Hamilton, ON, Canada

M. Petzold

Centre for Applied Biostatistics, Sahlgrenska Academy,

University of Gothenburg, Gothenburg, Sweden

123

Knee Surg Sports Traumatol Arthrosc

DOI 10.1007/s00167-013-2811-6

restoration of native anatomy and kinematics. Up to

recently, transtibial single-bundle ACL reconstruction has

been the standard surgical option to treat ACL-deficient

knees [7]. It was developed during an era where isometric

graft placement was the norm [37]. The concept of iso-

metric placement denotes that the distance between ACL

graft origin and insertion remains constant during flexion

and extension. The reasons for the adherence to the iso-

metric concept were that biomechanical studies had shown

irreversible elongation of the graft if stretched repetitively

more than four per cent, and surgeons believed that this

elongation was prevented when placing the graft isomet-

rically [35, 46]. In addition to this, to achieve effective

isometry, optimal graft placement was high in the interc-

ondylar notch of the femur close to the proximal limit of

Blumensaat’s line, and this graft position was outside the

native femoral ACL footprint.

Recent biomechanical and clinical studies have shown

suboptimal restoration of knee kinematics and sustained

pivot-shift with isometrically placed grafts in comparison

with those placed in the native ACL footprints [22, 30, 33].

Today, it is known that native ACL is in not isometric,

owing largely to its complex, non-uniform multiple-bundle

anatomy, with each bundle exhibiting different tensile

properties [2]. The antero-medial (AM) bundle is taut

predominantly during knee flexion with a maximum at

45�–60�, whereas the postero-lateral (PL) bundle is maxi-

mally taut with the knee in full extension. Efforts have

been made to develop techniques to reconstruct AM and

PL bundles separately, as well as focusing increased

emphasis on the positioning of the individual grafts to as

closely as possible resemble that of the native ACL bun-

dles, the so-called anatomic double-bundle reconstruction.

Recent biomechanical and clinical trials have shown

superior results in support of this technique [19, 31, 44].

The theoretical advantage is that the two bundles can be

tensioned separately, therefore mimicking more of the

native tension patterns of the ACL bundles. As a result, in

addition to restoring A–P laxity by reconstructing the AM-

bundle, it is believed that double-bundle ACL reconstruc-

tion more effectively re-establishes rotational laxity of

which primarily the PL bundle contributes. Striving for

anatomically placed single-bundled reconstruction with the

goal of placing the graft both in the centres of the tibial and

femoral footprints demands high technical ability of the

orthopaedic surgeon. Results from previous biomechanical

studies on elongation still stand true; thus, if single-bundle

reconstruction is performed with graft placement off-centre

with regard to ACL footprints, this poses a risk of elon-

gation and graft rupture [46]. A number of systematic

reviews and meta-analyses have recently emerged focusing

on single-bundle and double-bundle ACL reconstruction. A

shortcoming common to all these are that there are no strict

distinctions between anatomic and non-anatomic tech-

niques. In the clinical setting, this analysis is of great

importance as there is a growing interest in both techniques

as promising surgical intervention options.

Current comparative studies on anatomic single-bundle

and double-bundle ACL reconstruction with focus on knee

kinematics and graft ruptures were investigated. To obtain

true homogeneity, only studies comparing anatomically

placed single- and double-bundle ACL reconstruction were

included. Kinematic variables was the main focus of ana-

lysis, as we believe they are the most significant contributors

to subjective and objective outcomes in the long term and

that subjective short-term outcome measures are too coarse a

tool to detect differences between the two techniques.

It was hypothesized that anatomic single-bundle ACL

reconstruction was less effective than anatomic double-

bundle reconstruction in terms of restoration of knee

kinematics and leads to higher graft failure frequency.

Materials and methods

This systematic review was conducted in accordance with

the PRISMA guidelines (preferred reporting items of sys-

tematic reviews and meta-analyses) [27]. PRISMA is

comprised of a checklist including 27 items relating to the

content of systematic reviews and meta-analyses and a

four-phase flow diagram depicting the processing of this

content.

Eligibility criteria

Inclusion criteria were clinical studies comparing anatomic

single- and double-bundle primary ACL reconstruction.

Only studies on human adults with isolated total ACL

rupture were eligible for inclusion. Studies on patients with

open physes and cadavers were not included. Only thera-

peutic studies were included, whereas prognostic and

diagnostic studies were excluded unless the authors

reported a clear relation between the outcome measures

and the surgical technique. No Economical and Decision

analysis studies were included. Concomitant meniscus and

minor cartilage injuries were not grounds for exclusion

[36].

Information sources and search

Electronic search

A systematic electronic search was performed from Pub-

Med (MEDLINE), EMBASE and Cochrane Library


123

databases. Publication dates set for inclusion were from

January 1995 to August 2011. An additional updated

search was performed in July 2012 only from the PubMed

(MEDLINE) database and relevant publications between

August 2011 and July 2012 were included. Two experts in

electronic search methods at the **MASKED** Library

performed and validated the search. The following search

strings were used in the fields Title, Abstract and Key-

words: (‘‘Anterior Cruciate Ligament’’ [Mesh] OR ‘‘ante-

rior cruciate ligament’’ [tiab] OR ACL [tiab]) AND

(‘‘Surgical Procedures, Operative’’ [Mesh] OR surgical

[tiab] OR surgery [tiab] OR reconstruction [tiab] OR

reconstructive [tiab] OR reconstructed [tiab]) AND (Eng-

lish [lang] AND (‘‘1995’’ [PDAT]: ‘‘3000’’ [PDAT])).

Only papers written in English were included [36].

Data collection and analysis

Study selection

All the studies yielded from the electronic search were

sorted based on abstracts by three reviewers, each reviewer

sorting one database each that in turn was validated twice by

the other reviewers. The included studies were then cate-

gorized into study types proposed by the Oxford Centre for

Evidence-Based Medicine and into the category single-

bundle, double-bundle or single-bundle versus double-bun-

dle reconstruction. Studies were included if they fell into one

of the following categories: randomized controlled trial,

prospective comparative study and retrospective compara-

tive study. If a study belonged to several categories, it was

placed in the category of which the majority of study was

related. Only studies comparing anatomic single-bundle

versus double-bundle ACL reconstruction were included in

this meta-analysis regardless of graft type or fixation

method. The operative technique used to achieve anatomic

ACL reconstruction had to be clearly described by the

authors. The authors needed to state that grafts were placed

in the native ACL footprints on both the tibial and femoral

side in both single-bundle and double-bundle groups for the

technique to be regarded as anatomic and the article to be

eligible for inclusion. The study was analyzed in full text if

the abstract did not provide enough data to make a decision.

The researchers were not blinded to author, year and journal

of publication. Disagreement between the reviewers was

resolved by consensus or by discussion with the senior

author when consensus was not reached.

Data collection process

Data from each study was extracted using a computerized

database created in Microsoft Access (Version 2010,

Microsoft Corporation, Redmond, WA, USA). Extraction

was performed by the first, second and senior author and

validated twice by the first author.

Data items

The data extracted from the included studies were as follows:

author, year, title, journal, volume, issue, pages, ISSN, DOI,

abstract, author-address, database provider, category, study

type, level of evidence and country. Where stated, we

extracted sample size and follow-up time. Surgical details

regarding technique used in each case was also obtained and

included drilling technique, placement of tibial and femoral

tunnels and tension patterns of the grafts used. Data regarding

kinematic tests were extracted and included pivot-shift test,

Lachman test, anterior drawer test, KT-1000 measurements,

A–P laxity measures using navigation and total internal–

external (IRER) laxity measured using navigation. No

predefined concept of what constitutes a graft failure was

created. The number of graft failures were extracted from the

included studies if the authors explicitly stated the terms graft

failure or graft rupture. In the case of pivot-shift test and

Lachman test, outcomes were dichotomized, yielding only

‘‘positive/normal’’ or ‘‘negative/abnormal’’ results. Several

authors reported rotational laxity and A–P laxity measured at

multiple flexion angles, and we chose to include those mea-

sured at 30� flexion for statistical analysis. Data regarding

rotational laxities measured with pilot navigation were

extracted; values of rotational laxity obtained using EMS or

camera motion analysis were not extracted and were excluded

from statistical analysis. Trials comparing double-bundle

ACL reconstruction to two separate single-bundle groups (e.g.

AM and PL) were included, but only data from the AM group

were extracted and analyzed [43]. One study compared a

double-bundle group to two single-bundle groups, one using

metallic screws to anchor the graft and the other group using

bioabsorbable screws; there was no statistical difference

between the two single-bundle groups, and therefore, we

chose to only include data from the bioabsorbable screw group

in the analysis [40]. One study reporting internal and external

rotation separately did not specify where the authors set the

starting position and how they consistently used the same

starting position, and thus, values were combined to yield a

total rotation measurement [8]. In those cases where relevant

unpublished results were desired, the authors were contacted

[8, 13, 16, 34], and replies with the requested data from three

of the authors were received [8, 16, 34]. To allow for statistical

analysis, sample sizes were adjusted for each group taking into

account patients lost to follow-up [8, 34].

Synthesis of results

Statistical meta-analysis of the data was performed using

the metan command version sbe24_3 for Stata (Version


123

12.1, StataCorp LP, Texas, USA). In some studies, zero

events were reported. Following the Cochrane recom-

mendation, 0.5 was added to cases and non-cases in both

study groups (http://handbook.cochrane.org). In the cases

that standard error was not obtainable from the studies or

after requesting these from the authors, standard errors

were instead calculated based on the values reported in the

studies within the same group with regard to that particular

variable. Results were expressed as odds ratios (OR) with

95 % confidence intervals (CI) for dichotomous outcomes

and for continuous outcomes as standardized mean differ-

ences (SMD) with 95 % CI. Random effect meta-analysis

was used to account for heterogeneity. The I2 is provided in

the graphs for each analysis to show the level of hetero-

geneity. The I2 index can be interpreted as the percentage

of the total variability in a set of effect sizes that is

attributable to genuine heterogeneity between the groups

[10].

Assessment of risk of bias

Until recently, the use of checklists and scores has been

the modus operandi when evaluating the risk of bias in a

study or trial. However, the Cochrane Collaboration has

recommended against using such tools [9]. The reasons

for this are numerous but include the fact that scores and

checklists are suboptimal tools for evaluating internal

validity as opposed to external validity. With scores and

checklists, emphasis is often on the extent of reporting

rather than on the conduct in that particular study.

Another example is that to arrive at a score, the criteria

therein must be weighted somehow and it is often difficult

and unclear to justify how and why those weights are

assigned. We chose to utilize the Cochrane Collabora-

tion’s tool for assessing risk of bias developed by the

Cochrane Bias Methods Group [9]. The assessment tool

covers six domains of bias: sequence generation, alloca-

tion concealment, blinding, incomplete outcome data,

selective outcome reporting and other sources of bias.

Within each domain, an independent judgment by the two

first authors of high, low or unclear risk of bias is made.

Any discrepancies were resolved by consensus or by

discussion with the senior author when consensus was not

reached. Although primarily a tool intended for imple-

mentation on randomized controlled trials, we chose to

use it on the prospective comparative studies in addition

to the randomized controlled trials included in this meta-

analysis. In those cases that insufficient information was

reported by the authors of a study with regard to the

parameters in the bias assessment tool, we awarded them

an ‘‘unclear risk’’ grade. If sufficient information was

reported by the author to determine the risk of bias, then

they were awarded ‘‘high risk’’ or ‘‘low risk’’ for that

particular bias parameter.

Results

An electronic search yielded 5,608 studies in PubMed

(MEDLINE), 5,421 studies in EMBASE and 700 studies in

the Cochrane Library. Fifteen duplicates were removed from

PubMed, 4,048 from EMBASE and 512 from Cochrane

Library. There were 7,154 studies left in which 3,757 were

excluded based on the abstracts and 1,887 based on full-text

assessment. A total of 1,510 studies were included in the

database and categorized into single-bundle, double-bundle

and single-bundle versus double-bundle ACL reconstruc-

tion. Fifty-one studies were categorized as studies compar-

ing single- and double-bundle ACL reconstruction. Two

studies reported from the same pool of data in different

publications with different outcomes, population sizes and

follow-up times [14, 40], only the most recently published of

these two studies was included for analysis [40]. Further

screening of these 51 studies using the aforementioned

inclusion criteria yielded eleven Level I or II studies that

were regarded as having performed anatomic single-bundle

and double-bundle ACL reconstruction. An updated search

was performed in July 2012 only from the PubMed database

yielding 596 studies. Of these, a total of 4 studies met the

aforementioned selection process and were included in our

analysis. This finally amounted to 15 studies in total, 8 RCTs

and 7 prospective cohort studies that were included in our

analysis [1, 3, 4, 6, 8, 11–13, 16, 23, 26, 34, 38, 40, 43]

(Fig. 1).

Characteristics of the studies

Of the 15 studies included (n = 970 patients), 8 were

randomized controlled trials (n = 513 patients) and 7 were

prospective comparative studies (n = 457 patients). The

included studies were published between 2007 and 2012.

Follow-up times varied with mean follow-up times ranging

from 5 months to 5 years. Three studies reported data

obtained intra-operatively (using computer navigation) [13,

16, 34]. Where stated, information on drilling technique,

tunnel placement and knee flexion angle at graft tensioning

was noted (Table 1).

Kinematic results

Ten of the 15 included studies reported values of pivot-

shift test [3, 4, 6, 11, 12, 23, 26, 38, 40, 43]. Ten studies

reported values of side-to-side difference in A–P laxity

measured with KT-1000 [1, 3, 4, 11, 12, 23, 26, 38, 40, 43]


123

http://handbook.cochrane.org

and one using Rolimeter [6]. Three studies reported A–P

laxity measured by navigation [13, 16, 34]. Rotational

laxity was reported in 5 studies using perioperative navi-

gation [8, 13, 16, 23, 34] (Table 2; Figs. 2, 3, 4, 5, 6, 7, 8).

Risk of bias in included studies

Of the 15 studies included, the majority exhibited a high

risk of selection bias illustrating poor methods of ran-

domization or inadequate reporting of methods of ran-

domization and allocation concealment, and these included

both prospective comparative studies as well as certain

randomized controlled trials [4, 6, 8, 11, 13, 16, 26, 34, 43].

One study clearly reported their method for allocation

concealment, however, failed to describe how the ran-

domization was performed and was graded accordingly

[40]. One study states clearly how both randomization and

allocation concealment was performed and therefore was

determined to exhibit low risk of selection bias [12]. One

study was graded ‘‘high risk’’ of other bias due to a base-

line imbalance [13] (Table 3).

Reported significant findings from included studies

Knee laxity

Three studies reported a significant difference between

single-bundle and double-bundle groups in laxity mea-

surements with KT-1000, with results favouring double-

bundle ACL reconstruction [1, 12, 38]. Two studies

showed significant differences in manual pivot-shift test

between single-bundle and double-bundle groups in favour

of double-bundle ACL reconstruction, [12, 38]. Only two

studies reported significantly less rotatory laxity in the

double-bundle ACL reconstruction group compared to

single-bundle reconstruction [23, 34] (see Table 4).

Graft failure

Graft failures were reported in six studies [1, 4, 6, 11, 38,

40]. Only one study performed statistical analysis of graft

failures and reported statistically significant better results

in the double-bundle group [40] (Table 5).

Fig. 1 Flow diagram of created

ACL reconstruction database

and the selection of studies for

the meta-analysis


123

Results of meta-analysis

Anterior laxity measured using KT-1000 arthrometer

readings showed statistically significant results favouring

double-bundle reconstruction (p \ 0.001) with a SMD of

0.36 (95 % CI 0.214–0.513). A significant difference was

observed in favour of double-bundle reconstruction when

measuring A–P laxity using navigation (p = 0.042) with

SMD of 0.29 (95 % CI 0.01–0.565). No significant

differences were seen regarding pivot-shift, Lachman test,

anterior drawer, IRER or graft failure (Table 6).

Discussion

The most important findings of this meta-analysis were that

anterior laxity as measured with the KT-1000 arthrometer

and A–P laxity measured by navigation showed results

Table 1 Study characteristics

Author Year Study

type

LoE Sample size

(n)

Surgery Follow-up

(months)

Drilling Tension pattern

(flexion angle at

tensioning)

Fujita et al. [4] 2011 PCS 2 36 SB (n = 18) Mean 31.9 (SB)

and 33.7 (DB)

TT 60 AM/15 PL

DB (n = 18) TT (AM)/TP (PL) 60 AM/15 PL

Gobbi et al. [6] 2011 PCS 2 60 SB (n = 30) Mean 46.2

minimum 36

TP Not spec

DB (n = 30) TP 20 AM/0 PL

Hemmerich et al. [8] 2011 PCS 2 29 SB (n = 17) 5.2 TP 45

DB (n = 12) TP 45 AM/15 PL

Ishibashi et al. [13] 2008 PCS 2 125 SB (n = 45) 0 TT 0

DB (n = 80) AM not spec/TT (PL) 15 AM/15 PL

Misonoo et al. [26]. 2011 PCS 2 44 SB (n = 22) 9–20, minimum

12

TT 20

DB (n = 22) TT (AM)/TP or TT (PL) 20

Plaweski et al. [34] 2011 PCS 2 62 SB (n = 32) 0 Not spec Not spec

DB (n = 30) TP Not spec

Aglietti et al. [1] 2010 RCT 1 70 SB (n = 35) Minimum 24 TP 20

DB (n = 35) TP 40 AM/20 PL

Araki et al. [3] 2011 RCT 1 20 SB (n = 10) Mean 12 (SB),

13.5 (DB)

TP 15


Kanaya et al. [16] 2009 RCT 1 26 SB (n = 13) 0 TT or TP 30

DB (n = 13) TT or TP (AM ? PL) 30 AM/15 PL

Siebold et al. [38] 2008 RCT 1 70 SB (n = 35) Mean 19 months

(range 13–24)

Not spec 60


Yagi et al. [43] 2007 RCT 1 40 SB (n = 20) 12 TT 60


Hussein et al. [11] 2012 PCS 2 101 SB (n = 32) Mean 30 (range

26–34)

TP 0

DB (n = 69) TP 0 AM/60 PL

Hussein et al. [12] 2012 RCT 1 209 SB (n = 78) Mean 51.15

(range 39–63)

TP 0

DB (n = 131) TP 0 AM/60 PL

Lee et al. [23] 2012 RCT 1 37 SB (n = 18) 24 Not spec Not spec

DB (n = 19) TT or TP 10 AM/0 PL

Suomalainen et al. [40] 2012 RCT 1 41 SB (n = 21) 60 TP Not spec

DB (n = 20) TP Not spec

PCS prospective comparative study, RCT randomized controlled trial, LoE level of evidence, SB single-bundle, DB double-bundle, TT transtibial,

TP trans-portal, AM antero-medial, PL postero-lateral, Not spec not specified


123

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DB

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Go

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.4±

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3.4

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(n=

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0.8

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.41

0.4

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.22

1.2

Ish

ibas

hi

etal

.[1

3]

12

5S

B(n

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38

.1±

5.7

4.8

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.5

DB

(n=

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1.1

Mis

on

oo

etal

.[2

6]

44

SB

(n=

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1.4

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.41

7.7

±4

.2b

DB

(n=

22

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2/0

1.3

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.51

7.5

±4

.1b

Pla

wes

ki

etal

.[3

4]

62

SB

(n=

32

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7.5

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.01

1.5

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.53

0±

3.0

4.5

±2

.6

DB

(n=

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3.2

±4

.99

.1±

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22

.5±

4.2

3.4

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.7

Ag

liet

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[1]

70

SB

(n=

35

)2

.3±

1.4

DB

(n=

35

)1

.3±

1.3

Ara

ki

etal

.[3

]2

0S

B(n

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1.7

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(n=

10

)9

/11

0/0

0.7

±1

.8

Kan

aya

etal

.[1

6]

26

SB

(n=

13

)8

3

DB

(n=

13

)1

22

Sie

bo

ldet

al.

[38]

70

SB

(n=

35

)2

5/1

01

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1.3

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(n=

35

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4/1

1.0

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[43

]4

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B(n

=2

0)

15

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5/5

1.9

±1

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DB

(n=

20

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7/3

17

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1.2

Hu

ssei

net

al.

[11

]1

01

SB

(n=

32

)2

7/5

1.6

±0

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DB

(n=

69

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9/1

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0.9

Hu

ssei

net

al.

[12

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09

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(n=

78

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2/2

61

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0.8

DB

(n=

13

1)

12

2/9

1.2

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.9

Lee

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.[2

3]

37

SB

(n=

18

)1

2/6

10

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3/5

2.7

4±

1.6

51

3.7

±3

.91

2.8

±3

.72

6.6

±4

.8

DB

(n=

19

)1

3/6

14

/51

6/3

2.6

2±

1.7

21

1.5

±4

.11

2.5

±4

.82

4.0

±7

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Su

om

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etal

.[4

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41

SB

(n=

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123

favouring anatomic double-bundle ACL reconstruction.

These results may to some extent give more information

about the conditions reached in the reconstructed knee

under dynamic conditions and what degenerative

implications this may have on the joint with time [15].

Recently published meta-analyses on the subject revealed

similar findings [25, 41, 42, 47]. Gadikota et al. [5] found

no statistically significant differences in A–P laxity

Fig. 2 Forest plot showing standard mean difference in KT-1000 arthrometer measurements between anatomic double- and single-bundle ACL

reconstructions

Fig. 3 Forest plot showing standard mean difference in navigation measured antero–posterior laxity after anatomic double- versus single-bundle

ACL reconstructions


123

between groups in an in vivo group. It appears the most

recent meta-analysis and more importantly, the only meta-

analysis that like ours compares exclusively anatomic

reconstruction supports these findings [42]. The present

meta-analysis, however, is unique in comparison with the

above-mentioned studies as it focuses solely on anatomi-

cally performed single- and double-bundle ACL recon-

struction and in addition includes a far more

comprehensive database search resulting in inclusion of

double the number of studies on anatomically performed

single- and double-bundle ACL reconstructions compared

with that of van Eck et al. [42].

Results from this meta-analysis of anatomic single-bun-

dle and double-bundle ACL reconstruction revealed no sta-

tistically significant differences between the single- and

double-bundle groups in terms of restoration of rotational

laxity as measured by pivot-shift test or navigation. How-

ever, the results do point to a trend in support of that anatomic

double-bundle ACL reconstruction is superior to single-

bundle reconstruction in these regards. Kinematics and in

particular rotatory laxity are important postoperative out-

come measures in the short term [17, 18, 39]. We conclude

that these measures, as opposed to subjective outcome

scores, provide a more precise means to objectively evaluate

differences in outcome between anatomic single-bundle and

anatomic double-bundle ACL reconstruction.

Restoration of rotatory laxity in particular is paramount

to re-establish as closely as possible the pre-injury

conditions in the knee. Suboptimal restoration of rotational

laxity, resulting in, for example, residual positive pivot

shift after ACL reconstruction, has deleterious effects on

meniscal and chondral structures in the knee and can at

least theoretically be regarded as a predictor of future

osteoarthritis (OA) [15, 24]. In addition to this, previous

studies have also shown that excess persistent rotational

laxity negatively affects patient reported outcomes and

patient satisfaction [17, 18].

It should be noted, however, that the pivot-shift test is

subjective and entails inter-observer variability that may

prove it to be a rather crude test of rotational laxity [21,

32]. An important finding of this meta-analysis is the clear

relationship observed between negative pivot-shift test and

double-bundle reconstruction, where we observed signifi-

cant differences with regard to number of negative pivot-

shift test in favour of the double-bundle group. van Eck

et al. [42] also compared anatomic single-bundle to ana-

tomic double-bundle ACL reconstructions. They included

12 studies, 7 of which they classify as anatomic single-

bundle versus double-bundle reconstruction. Sub-group

analysis comparing these anatomic groups revealed sig-

nificant differences in favour of double-bundle recon-

struction for restoration of rotational laxity using the

pivot-shift test. There was, however, a discrepancy with

regard to four studies classified as anatomic by van Eck

et al. that we chose to classify as non-anatomic [20, 28,

29, 45]. All studies included in the present meta-analysis

Fig. 4 Forest plot showing odds ratio of a normal pivot-shift test after anatomic double- versus single-bundle ACL reconstructions


123

were selected on the premise that both single-bundle and

double-bundle procedures were performed anatomically,

and in accordance to that, the authors needed to clearly

state that grafts were placed in the native ACL footprints

on both the tibial and femoral side in both single-bundle

and double-bundle groups. Two recently published meta-

analysis one of which is a Cochrane meta-analysis com-

paring single- and double-bundle ACL reconstruction

report findings of significantly higher number of negative

pivot-shift test in the double-bundle group [41, 47]. In

addition to these, one meta-analysis reports no significant

difference between single- and double-bundle groups with

regard to negative pivot-shift test [25], and one meta-

analysis presents data on the subject from 7 in vitro and 3

in vivo biomechanical studies but performs no statistical

analysis [5]. A shortcoming common to all these

meta-analyses is that no distinction is made between

anatomic and non-anatomic techniques.

When analyzing graft failure, six studies reported data,

one of which reported significantly less graft failures in the

double-bundle group [40]. In the current meta-analysis, we

also found results pointing to a trend favouring anatomic

double-bundle reconstruction when it comes to graft failure

rate without being able to show statistically significant fewer

graft failures in the anatomic double-bundle group. Results

reported by Tiamklamg et al. [41] in their Cochrane meta-

analysis support our beliefs in that statistically significant

differences were seen in favour of double-bundle recon-

struction for newly occurring traumatic ACL rupture.

Striving for anatomically placed single-bundled recon-

struction with the goal of placing the graft both in the centres

of the tibial and femoral footprints demands high technical

Fig. 5 Forest plot showing odds ratio of a normal Lachman test after anatomic double- versus single-bundle ACL reconstructions

Fig. 6 Forest plot showing odds ratio of a normal anterior drawer test after anatomic double- versus single-bundle ACL reconstructions


123

ability of the orthopaedic surgeon. This placement is difficult

to achieve and is of essence to create a graft that does not

elongate over time and potentially rupture. It is of the

authors’ belief that if anatomic single-bundle reconstruction

is performed with graft placement off-centre with regard to

ACL footprints, this may result in excessive force to the graft

which poses a future risk of future graft elongation and

rupture. Overcoming this is achieved through reconstruction

of each individual graft and anatomic placement of each graft

in the native bundle footprints.

The present meta-analysis is unique in that, to our

knowledge, it is the only meta-analysis to date addressing

the aspect of kinematics in strictly anatomically performed

single-bundle and double-bundle ACL reconstruction. An

additional strength of this meta-analysis lies in its extensive

and comprehensive database search, and adherence to strict

Fig. 7 Forest plot showing standard mean difference of total internal–external rotation after anatomic double- versus single-bundle ACL

reconstructions

Fig. 8 Forest plot showing odds ratio of negative graft failures after anatomic double- versus single-bundle ACL reconstructions


123

inclusion criteria further increases its quality. In those cases

where relevant unpublished results were desired, the

authors were contacted [8, 13, 16, 34], and we received

replies with the requested data from three of the authors [8,

16, 34] increasing its comprehensiveness. By dichotomiz-

ing variables with otherwise graded values, e.g., pivot-shift

test and Lachman test, we compared ‘‘normal’’/‘‘negative’’

results to all other results thereby allowing us to determine

whether anatomic double-bundle reconstruction resulted in

more ‘‘normal’’ results which was the hypothesis under

study.

Limitations of this meta-analysis include the fact that

date restrictions were set to the electronic search and

restricted the search to published studies and studies

published in English which may contribute to an element

of publication bias. The extensiveness of the search

yielded a large number of studies to categorize, and there

is a chance that some relevant articles were overlooked.

Studies of Levels I and II were included, which inevitably

lowers the overall Level of Evidence of the meta-analysis

somewhat and, however, creates a more complete cover-

age of the trials on the topic. Bias assessment of the

included studies using the Cochrane Collaboration’s tool

for assessing risk revealed a limitation of this meta-ana-

lysis in that numerous studies showed systematic meth-

odological errors (or simply lacking documentation) in,

for example, randomization methods and allocation con-

cealment deeming them to have an unclear or in cases

high risk of bias. The tool is primarily designed for use in

evaluating bias in randomized controlled trials; however,

we applied it to prospective comparative studies to which

to a certain extent accounts for the high number of

‘‘unclear’’ and/or ‘‘high risk’’ grades. The very nature of

some prospective comparative studies entail an inevitable

selection bias, which is why all of them in this meta-

analysis received a ‘‘high risk’’ grade with regard to

selection bias.

In the clinical setting, optimal restoration of knee

function and improvements in patient reported outcomes

still remain a challenge. This has been observed and

extensively studied regarding single-bundle ACL recon-

struction primarily which to date has been the surgical

method of choice. Recent evidence has emerged that both

anatomic single- and double-bundle are proving to be

promising surgical options. The results of this meta-ana-

lysis may illustrate the importance of the anatomic resto-

ration of both the AM and PL bundles.

Conclusion

Anatomic double-bundle ACL reconstruction is superior to

anatomic single-bundle reconstruction in terms of restoration

of knee kinematics, primarily A–P laxity. Whether these

improvements of laxity result in long-term improvement of

clinical meaningful outcomes remains uncertain. Interest-

ingly, the only significant differences we observed favouring

anatomic double-bundle ACL reconstruction in this meta-

analysis were those of instrumented laxity measurements

(using KT-1000 and navigation). This illustrates the

Table 3 Bias evaluation

Author Random

sequence

generation

(selection bias)

Allocation

concealment

(selection

bias)

Blinding of

participants and

researchers

(performance bias)

Blinding of

outcome

assessment

(detection bias)

Incomplete

outcome data

(attrition bias)

Selective

reporting

(reporting

bias)

Other

bias

Fujita et al. [4] - - - - ? ? ?

Gobbi et al. [6] - - ? ? ? ? ?

Hemmerich et al. [8] - - ? - ? ? ?

Ishibashi et al. [13] - - - - ? ? -

Misonoo et al. [26] - - - - ? ? ?

Plaweski et al. [34] - - - - ? ? ?

Aglietti et al. [1] ? ? ? ? - ? ?

Araki et al. [3] - ? - - ? ? ?

Kanaya et al. [16] - - - - ? ? ?

Siebold et al. [38] ? ? - ? ? ? ?

Yagi et al. [43] - - - - ? ? ?

Hussein et al. [11] - - - ? ? ? ?

Hussein et al. [12] ? ? - ? ? ? ?

Lee et al. [23] ? ? ? ? ? ? ?

Key ?, low risk of bias; -, high risk of bias; ?, unclear risk of bias


123

Table 4 Reported significant findings from included studies

Study Lachman

test

Anterior

drawer test

KT-1000 A–P laxity Pivot-shift test Rotatory laxity

sign/non-

sign

Sign/non-

sign

Sign/non-sign Sign/

non-sign

Method Sign/

non-sign

Sign/

non-sign

Method

(navigation

system)

Fujita et al. [4] nsa nsa

Gobbi et al. [6] ns Rolimeter ns

Hemmerich et al. [8] ns 8 camera

MAS

Ishibashi et al. [13] ns Ortho-

pilot

ns Ortho-pilot

Misonoo et al. [26] ns ns ns ns 9 camera

MAS

Plaweski et al. [34] ns Praxim ns DB sig

(p \ 0.001)

Praxim

Aglietti et al. [1] ns DB sig

(p \ 0.03)

ns

Araki et al. [3] ns ns nsb

Kanaya et al. [16] ns Ortho-

pilot

ns Ortho-pilot

Siebold et al. [38] DB sig

(p = 0.054)

DB sig

(p = 0.01)

Yagi et al. [43] ns ns nsb

Hussein et al. [11] ns ns

Hussein et al. [12] DB sig

(p = 0.002)

DB sig

(p \ 0.001)

Lee et al. [23] ns ns ns ns Ortho-

pilot

ns DB sig

(p \ 0.05)

Ortho-pilot

Suomalainen et al.

[40]

ns ns

DB double-bundle, MAS motion analysis system, sig significant, ns not significanta Double-bundle group better than PL group but not better than AM groupb Not significant with manual pivot-shift test but significant with quantitative measurement with electromagnetic sensor

Table 5 Graft failures

SB single-bundle, DB double-

bundle, AM antero-medial, PL

postero-lateral, ACL anterior

cruciate ligament

Study Graft

failure

Comment

SB DB

Fujita et al. [4] 2 0 Two single-bundle groups, AM and PL. Both graft failures were in PL

group and were reported as graft re-ruptures

Gobbi et al. [6] 0 0

Aglietti et al. [1] 3 1 One traumatic graft rupture in single-bundle group, the rest non-

traumatic graft failures of instability

Siebold et al.

[38]

0 1 One traumatic graft rupture

Hussein et al.

[11]

1 1 One from each group succumbed to graft failure defined as graft ruptures

due to new injury

Suomalainen

et al. [40]

7 1 All graft failures in both SB and DB group were defined as traumatic graft

ruptures


123

underlying importance of developing and implementing

standardized and quantified clinical examination tests in the

future.

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Lachman [3, 23, 43] 1.99 0.72 to 5.45 n.s. (p = 0.182) 0

Anterior drawer [23] 2.05 0.41 to 10.24 n.s. (p = 0.381) –

KT-1000 [1, 3, 4, 6, 11, 12, 23, 26, 38, 40, 43] 0.36 0.21 to 0.51 sig (p \ 0.001) 0

Total internal–external rotation [8, 13, 16, 23, 26, 34] 0.27 -0.51 to 1.05 n.s. (p = 0.501) 89.9

Antero–posterior laxity [13, 16, 34] 0.29 0.01 to 0.57 sig (p = 0.042) 0

Graft failure [1, 4, 6, 11, 38, 40] 2.96 0.96 to 9.18 n.s. (p = 0.060) 0

SMD standardized mean difference, CI confidence interval, sig significant, n.s. not significant


123

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