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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: kristian@samuelsson.cc
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
Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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]
Knee Surg Sports Traumatol Arthrosc
123
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
Knee Surg Sports Traumatol Arthrosc
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
DB (n = 10) TT (AM)/TP (PL) 60 AM/15 PL
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
DB (n = 35) TT (AM)/TP (PL) 60 AM/20 PL
Yagi et al. [43] 2007 RCT 1 40 SB (n = 20) 12 TT 60
DB (n = 20) TT (AM)/TP (PL) 60 AM/15 PL
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
Knee Surg Sports Traumatol Arthrosc
123
Ta
ble
2K
inem
atic
resu
lts
Au
tho
rS
amp
lesi
ze(n
)S
urg
ery
Piv
ot
shif
t
(neg
/po
s)
Lac
hm
an
(neg
/po
s)
An
teri
or
dra
wer
(neg
/po
s)
KT
-10
00
(mm
±S
D)
IR(�
±S
D)
ER
(�±
SD
)
IRE
R
(�±
SD
)
A–
Pla
xit
y
(Pil
ot
Nav
)
(mm
±S
D)
Fu
jita
etal
.[4
]3
6S
B(n
=1
8)
15
/31
.6±
2.3
DB
(n=
18
)1
6/2
0.3
±2
.6
Go
bb
iet
al.
[6]
60
SB
(n=
30
)2
5/5
1.4
±0
.3a
DB
(n=
30
)2
6/4
1.4
±0
.2a
Hem
mer
ich
etal
.[8
]2
9S
B(n
=1
7)
13
.4±
6.0
10
±3
.52
3.4
DB
(n=
12
)1
0.8
±6
.41
0.4
±5
.22
1.2
Ish
ibas
hi
etal
.[1
3]
12
5S
B(n
=4
5)
38
.1±
5.7
4.8
±1
.5
DB
(n=
80
)3
7.0
±5
.84
.6±
1.1
Mis
on
oo
etal
.[2
6]
44
SB
(n=
22
)2
2/0
1.4
±0
.41
7.7
±4
.2b
DB
(n=
22
)2
2/0
1.3
±0
.51
7.5
±4
.1b
Pla
wes
ki
etal
.[3
4]
62
SB
(n=
32
)1
7.5
±4
.01
1.5
±3
.53
0±
3.0
4.5
±2
.6
DB
(n=
30
)1
3.2
±4
.99
.1±
3.6
22
.5±
4.2
3.4
±3
.7
Ag
liet
tiet
al.
[1]
70
SB
(n=
35
)2
.3±
1.4
DB
(n=
35
)1
.3±
1.3
Ara
ki
etal
.[3
]2
0S
B(n
=1
0)
7/3
10
/01
.8±
1.7
DB
(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
.6±
1.3
DB
(n=
35
)3
4/1
1.0
±1
.0
Yag
iet
al.
[43
]4
0S
B(n
=2
0)
15
/51
5/5
1.9
±1
.6
DB
(n=
20
)1
7/3
17
/31
.3±
1.2
Hu
ssei
net
al.
[11
]1
01
SB
(n=
32
)2
7/5
1.6
±0
.9
DB
(n=
69
)5
9/1
01
.5±
0.9
Hu
ssei
net
al.
[12
]2
09
SB
(n=
78
)5
2/2
61
.6±
0.8
DB
(n=
13
1)
12
2/9
1.2
±0
.9
Lee
etal
.[2
3]
37
SB
(n=
18
)1
2/6
10
/81
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
.0
Su
om
alai
nen
etal
.[4
0]
41
SB
(n=
21
)1
0/1
12
.2±
2.8
DB
(n=
20
)7
/13
1.6
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Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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
Knee Surg Sports Traumatol Arthrosc
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
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