Systematic Review
Experimental Execution of the Simulated Pivot-Shift
Test: A Systematic Review of Techniques
Fabio V. Arilla, M.D., Marco Yeung, M.D., Kevin Bell, Ph.D., Ata A. Rahnemai-Azar, M.D.,
Benjamin B. Rothrauff, M.Res., Freddie H. Fu, M.D., D.Sc.(Hon), D.Ps.(Hon),
Richard E. Debski, Ph.D., Olufemi R. Ayeni, M.D., M.Sc., F.R.C.S.C., and
Volker Musahl, M.D.
Purpose: To conduct a systematic review to identify and summarize the various techniques that have been used to
simulate the pivot-shift test in vitro. Methods: Medline, Embase, and the Cochrane Library were screened for studies
involving the simulated pivot-shift test in human cadaveric knees published between 1946 and May 2014. Study parameters including sample size, study location, simulated pivot-shift technique, loads applied, knee flexion angles at which
simulated pivot shift was tested, and kinematic evaluation tools were extracted and analyzed. Results: Forty-eight studies
reporting simulated pivot-shift testing on 627 cadaveric knees fulfilled the criteria. Reviewer inter-rater agreement for
study selection showed a k score of 0.960 (full-text review). Twenty-seven studies described the use of internal rotation
torque, with a mean of 5.3 Nm (range, 1 to 18 Nm). Forty-seven studies described the use of valgus torque, with a mean of
8.8 Nm (range, 1 to 25 Nm). Four studies described the use of iliotibial tract tension, ranging from 10 to 88 N. Regarding
static simulated pivot-shift test techniques, 100% of the studies performed testing at 30 of knee flexion, and the most
tested range of motion in the continuous tests was 0 to 90 . Anterior tibial translation was the most analyzed parameter
during the simulated pivot-shift test, being used in 45 studies. In 22% of the studies, a robotic system was used to simulate
the pivot-shift test. Robotic systems were shown to have better control of the loading system and higher tracking system
accuracy. Conclusions: This study provides a reference for investigators who desire to apply simulated pivot shift in their
in vitro studies. It is recommended to simulate the pivot-shift test using a 10-Nm valgus torque and 5-Nm internal rotation
torque. Knee flexion of 30 is mandatory for testing. Level of Evidence: Level IV, systematic review of basic science
studies.
he anterior cruciate ligament (ACL) of the knee is
the primary restraint to anterior tibial translation
(ATT). Therefore clinical examinations such as the
Lachman and anterior drawer tests were designed to
diagnose ACL insufficiency. Reports by Palmer1 and
Smith2 in the early 1900s showed that the ACL also
plays a role as a restraint to rotation of the knee. By
adding external rotation to the anterior drawer test,
Slocum and Larson3 were the first authors to describe a
clinical examination that assessed the rotatory stability
T
of the knee. Galway and MacIntosh4 expanded on their
work and, on the basis of previous studies performed
by Jakob and Noesberger5 and Lemaire et al.,6 coined
the term “pivot shift” to describe the anterolateral rotatory laxity often seen with ACL insufficiency. The pivot
shift is a complex and multiplanar maneuver that incorporates 2 main components: translation and rotation.
Despite the lack of standardization in the literature,7-9 it
has been shown to be the most specific diagnostic test
to detect ACL insufficiency.10 Furthermore, it has been
From the Department of Orthopaedic Surgery (F.V.A., A.A.R.-A, B.B.R.,
F.H.F., V.M.), Department of Bioengineering (K.B., R.E.D., V.M.), and Orthopaedic Robotics Laboratory (F.V.A., K.B., A.A.R.-A., B.B.R., R.E.D.,
V.M.), University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A.; Division of
Orthopaedic Surgery, McMaster University Medical Center (M.Y., O.R.A.),
Hamilton, Ontario, Canada; and Department of Orthopaedic Surgery, University Hospital of Canoas (F.V.A.), Canoas, Rio Grande Do Sul, Brazil.
The authors report the following potential conflict of interest or source of
funding: The Department of Orthopaedic Surgery of the University of
Pittsburgh receives research and educational funding from Smith & Nephew
for research in the field of anterior cruciate ligament reconstruction, not
directly related to the research presented in this manuscript. O.R.A. receives
support from Smith & Nephew.
Received February 24, 2015; accepted June 18, 2015.
Address correspondence to Volker Musahl, M.D., Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh, 3200 S
Water St, Pittsburgh, PA 15203, U.S.A. E-mail: [email protected]
Ó 2015 by the Arthroscopy Association of North America
0749-8063/15186/$36.00
http://dx.doi.org/10.1016/j.arthro.2015.06.027
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol
-,
No
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(Month), 2015: pp 1-10
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F. V. ARILLA ET AL.
shown to be correlated with clinical outcomes including
patient satisfaction and return to sports after ACL
reconstruction surgery in contrast to uniplanar examination maneuvers.11-14
However, the value of the pivot shift is limited
because of variable maneuvers among examiners and
the subjective grading system.15 In an attempt to
address these limitations, several research groups have
simulated the pivot-shift test in vitro using robotic
testing systems or custom-built devices that are able to
apply constant and repeatable loads to the knee. The
first attempt was performed in 1990 by Matsumoto,16
who simulated the pivot-shift test by building an
apparatus to apply 12.5 Nm of valgus torque while the
knee was manually flexed from 0 to 90 of flexion.
Matsumoto evaluated ATT using biplanar photography.
Since then, several research groups have attempted to
simulate the pivot-shift test using different techniques.17-19 Although these simulations often used a
static test with the knee tested at a few fixed flexion
angles,17,18 other studies performed the pivot-shift test
continuously through a range of motion in an attempt
to mimic the test performed clinically.19,20 Currently,
there are various techniques described in the literature,
and researchers do not have a guide regarding the advantages and disadvantages of each technique.
Therefore the purpose of this study was to systematically review the current literature to identify and
summarize all the techniques that have been applied to
simulate the pivot-shift test in vitro. We hypothesized
that this literature review would be able to recognize
the techniques that most reliably simulate the pivotshift test, thereby guiding researchers who plan to
simulate the pivot-shift test in future studies. In this
study a simulated pivot-shift test was defined as a test in
which the loads were not manually applied (i.e., the
amount of load applied is known and controlled).
Methods
Search Strategy
Electronic databases (Medline, Embase, and Cochrane
Library) were searched for simulated pivot-shift studies
from 1946 up to May 2014, when the search was performed. The search strategy used the following search
terms: (1) “pivot shift” AND (2) “knee” or “Knee”
subheading. The results were uploaded into a bibliographic management database (RefWorks, version 2.0;
ProQuest, Bethesda, MD).
Eligibility Criteria
The inclusion criteria for the studies in this systematic
review were as follows: (1) use of human cadaveric
knees; (2) reporting on the use of a simulated pivotshift test of the knee, defined by a test in which the
loads were not manually applied; and (3) publication in
the English language. The exclusion criteria were (1)
clinical studies involving pivot-shift testing in vivo, (2)
studies exclusively using manually performed pivotshift testing, and (3) review articles. A title and abstract review to screen for eligible studies was
completed in duplicate. A full-text review was then
conducted, also in duplicate, and references were hand
searched for other eligible studies. Any discrepancies
regarding inclusion were resolved through discussion
and consensus between reviewers (F.V.A., M.Y.).
Data Collection/Analyses
Data were collected from the included articles by the 2
reviewers (F.V.A., M.Y.) in an electronic spreadsheet
(Microsoft Excel 2011; Microsoft, Redmond, WA).
Abstracted data included the following information:
title, author, year of publication, location, sample size,
simulated pivot-shift technique (static v continuous),
degrees of knee flexion at which simulated pivot shift
was tested, loads at which simulated pivot shift was
tested, use of a robotic system, and kinematic evaluation
tools used. These data were compared across studies.
Inter-rater agreement regarding the inclusion and
exclusion of studies in the title/abstract review and
full-text review was assessed by calculating k scores,
reported with 95% confidence intervals. Statistical
analysis was performed using MedCalc Statistical Software, version 14.8.1 (MedCalc Software, Ostend,
Belgium). We interpreted the k scores as follow: 0.20 or
less, poor; 0.21 to 0.40, fair; 0.41 to 0.60, moderate;
0.61 to 0.80, good; and 0.81 to 1.00, excellent.
Methodologic Quality Assessment
Typical quality assessments of studies performed in
systematic reviews, such as the Methodological Index for
Non-Randomized Studies scale21 or the criteria of Detsky et al.,22 were deferred because all of the studies
included in this systematic review were cadaveric biomechanical studies and did not involve patients. Furthermore, much of the criteria (e.g., patient follow-up
duration, patients lost to follow-up, and inclusion of
consecutive patients) were not relevant or applicable. To
assess the methodologic quality of the included articles,
an adapted Methodological Index for Non-Randomized
Studies scale for in vitro experiments was developed by
2 reviewers (F.V.A., B.B.R.) (Appendix 1 and Appendix
Table 1, available at www.arthroscopyjournal.org). The
scale consists of 12 items, each scored from 0 to 2,
providing a total possible score of 24. On the basis of the
total score for a given study, methodologic quality was
graded as follows: less than 13, poor; 13 to 16, moderate;
17 to 20, good; and 21 to 24, excellent (Appendix 2,
available at www.arthroscopyjournal.org). All included
studies were scored independently, with agreement
between reviewers assessed by determination of the
intraclass correlation coefficient when comparing total
3
15.0
12.4
11.0
scores of each study. Average scores were also calculated
based on testing apparatus, thereby providing insight
into the advantages and disadvantages of using a particular testing method (Table 1).
Results
Identification of Studies
The initial electronic search yielded 1,748 studies;
after removal of duplicate studies and application of all
the criteria, 48 studies (Appendix 2, available at www.
arthroscopyjournal.org) were included in this review
(Fig 1). Inter-rater agreement in both the title/abstract
review and the full-text review was found to be
excellent, with k scores of 0.906 (95% confidence interval [CI], 0.860 to 0.951) and 0.960 (95% CI, 0.904 to
1.000), respectively.
Study Characteristics
In the 48 included studies, 18 institutions were
involved. Of the studies, 34 (74%) were performed in
the United States, 5 (10%) were performed in the
United Kingdom, 4 (8%) were performed in Germany,
and 4 (8%) were performed in Japan. A total of 627
human cadaveric knees were subjected to simulated
pivot-shift testing. The mean age of the cadaveric knees
(among the studies that provided a mean cadaver age)
was 52.4 years (range, 16 to 78 years).
19.3
19.1
16.7
17.5
10.5
15.3
13.5
14.5
1.6
2.0
1.1
1.7
1.4
0.6
1.0
1.7
1.6
1.0
0.4
1.0
1.8
1.7
1.2
1.7
1.2
0.9
1.3
0.6
0.4
0.9
0.2
0.6
1.0
2.0
1.0
1.5
1.0
0.0
1.0
2.0
1.5
0.0
0.0
0.0
1.5
2.0
1.0
2.0
1.0
1.0
1.0
2.0
1.5
0.0
0.0
1.5
1.8
2.0
1.0
1.2
1.5
0.0
1.0
2.0
2.0
1.3
0.0
1.5
0.8
2.0
1.5
0.9
1.0
0.0
0.0
1.6
1.5
0.5
0.0
0.8
2.0
2.0
1.0
2.0
2.0
2.0
1.0
1.5
1.0
2.0
0.0
1.0
2.0
2.0
1.0
2.0
1.5
1.3
1.0
1.5
2.0
1.3
0.0
1.0
2.0
2.0
1.3
2.0
2.0
0.5
1.3
2.0
2.0
1.3
1.7
1.2
1.9
2.0
1.1
1.9
2.0
0.3
1.6
2.0
2.0
1.6
1.6
1.1
Item
1. Purpose
2. Control groups
3. Specimen demographics
4. Specimen preparation
5. Experimental procedure
6. Power analysis
7. Statistics
8. Testing kinematics
9. Testing torque/forces
10. Tracking system accuracy
11. Loading system accuracy
12. Rationale for simulation
parameters
Total score
Rig
(n ¼ 3)
1.0
2.0
1.0
1.5
1.0
0.0
1.0
2.0
2.0
1.0
0.0
1.0
Specially
Designed
Jigs
(n ¼ 1)
Experimental
Arrangement
(n ¼ 1)
Experimental
Setup
(n ¼ 1)
Pivot-Shift Test
Apparatus
(n ¼ 3)
Mechanical
Pivot-Shift
Apparatus
Device
(n ¼ 1)
(n ¼ 4)
Biomechanical
Testing
Apparatus
(n ¼ 3)
Robotic
System
(n ¼ 11)
Table 1. Quality-Assessment Scores Overall and for Groups of Devices Used to Simulate Pivot-Shift Test
Mechanized
Pivot Shift Average
(n ¼ 20)
(n ¼ 48)
SIMULATED PIVOT-SHIFT TEST
Fig 1. Summary of literature search and inclusion/exclusion
process.
4
Table 2. Summary of Studies Using Static and Continuous Simulated Pivot-Shift Techniques
Study
Anderson et al.41
Diermann et al.17
Engebretsen et al.40
Fukuda et al.36
Goldsmith et al.18
Herbort et al.32
Herbort et al.31
Kanamori et al.29
Kanamori et al.38
Kondo et al.43
Kondo et al.20
Kondo et al.44
Lie et al.48
Markolf et al.23
Markolf et al.24
2010
17
Continuous
20 to 40
Markolf et al.25
Matsumoto et al.45
Matsumoto et al.47
Matsumoto et al.46
Matsumoto16
Sena et al.19*
2008
1994
1993
1993
1990
2013
10
5
29
1
29
6
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
20 to 40
0 to 90
0 to 90
0 to 90
0 to 90
0 to 60
NA
NA
12.5
12.5
12.5
12.5
5.5
2.5
Parameters Assessed
ATT
ATT, IR
ATT
ATT, IR, and ISF
Robotic
System
No
Yes
No
Yes
ATT
ATT
ATT
ATT, IR, and ISF of ACL
ATT, IR, ER, and ISF
Yes
Yes
Yes
Yes
Yes
Failure strength in ACL graft
ATT
ATT and IR
ATT and ISF in graft
ATT, IR, and ISF
ATT
ATT and IR
No
No
Yes
Yes
Yes
Yes
No
ATT
ATT and IR
ATT and IR
ATT and IR
No
No
No
No
ATT, IR, and relation of pivot-shift
magnitude and AP laxity
ATT, IR, and relation between pivot-shift
magnitude and AP laxity
ATT, IR, graft tension, and ISF of graft
IR
IR
IR
ATT, IR
ATT, IR, and velocity of ER and PTT
No
No
No
No
No
No
No
No
ACL, anterior cruciate ligament; AP, anteroposterior; ATT, anterior tibial translation; ER, external rotational; IR, internal rotational; ISF, in situ forces; NA, not applicable; Nm, Newton
meters; PTT, posterior tibial translation.
*This study applied 38 N of axial compression load during the pivot-shift test.
F. V. ARILLA ET AL.
Stapleton et al.26
Tsai et al.42
Wijdicks et al.33
Xu et al.34
Yamamoto et al.37
Zantop et al.35
Bull et al.27
Load Applied, Nm
Simulated
Internal
Iliotibial
Year
Sample
Pivot-Shift
Valgus
Rotation
Band Tension
Published
Size
Test Technique Knee Flexion Tested, 2010
12
Static
0, 20, 30, 60, and 90
10
5
2009
7
Static
0, 30, 60, and 90
10
4
2012
12
Static
0, 20, 30, 60, and 90
10
5
2003
10
Static
0, 15, 30, 45, 60, and 90 0, 0.7, 1.7, 3.3,
5.0, 6.7, 7.5,
8.3, or 10
2013
18
Static
0, 15, 20, and 30
10
5
2013
9
Static
0, 15, 30, 60, and 90
10
4
2010
9
Static
0, 30, 60, and 90
10
4
2000
12
Static
0, 15, 30, 60, and 90
10
10
2002
19
Static
15
10
0, 1.7, 3.3, 5.0,
6.6, 8.3, or 10
1998
12
Static
30
NA
2010
14
Static
0, 20, 30, 60, and 90
10
5
2013
18
Static
0, 20, and 30
10
5
2011
7
Static
15 and 30
7
5
2006
10
Static
15, 30, 45, and 60
10
5
0, 22, 44, or 88
2010
10
Static
0, 30, 60, and 90
10
4
1999
15
Continuous
0 to 120
0, 5, or 10
0, 10, 20, 30,
40, or 50
2011
8
Continuous
0 to 110
5
1
2010
8
Continuous
0 to 110
5
1
2014
14
Continuous
0 to 110
5
1
2007
8
Continuous
0 to 120
0, 5, or 10
0, 10, 20, 30,
40, or 50
2010
17
Continuous
20 to 40
NA
NA
NA
SIMULATED PIVOT-SHIFT TEST
Fig 2. Summary of loads in 20 studies that applied constant
values of internal rotation and valgus torques during simulated pivot-shift test.
Simulated pivot-shift tests were performed for various
purposes: 29 studies (61%) assessed ACL reconstruction
techniques, 4 studies (8%) compared intact knees with
ACL- or meniscus-deficient knees, 13 studies (27%)
reported the biomechanical characteristics of the pivotshift test, 1 study (2%) evaluated reconstruction of the
medial collateral ligament, and 1 study (2%) analyzed
the relation between the pivot-shift and Lachman tests.
Of the included studies, 22% used a robotic system for
the pivot-shift simulation whereas 78% described
various testing systems built by the authors.
Methodologic Quality Assessment
Methodologic quality scores were highly consistent
between reviewers, with an intraclass correlation coefficient of 0.971 (95% CI, 0.938 to 0.985) when
the total scores of the studies were compared. As shown
in Table 1, the average total score of all studies was
15 of 24 (range, 7 to 21) overall, being graded as
moderate, yet the studies using a “robotic system” or
“biomechanical testing apparatus” received the
highest total scores (Appendix 2, available at www.
arthroscopyjournal.org). Of particular note, these 2
systems were capable of applying specific and highly
repeatable forces to the specimen (index item 11),
whereas several additional methods could provide
similar accuracy when tracking joint kinematics (index
item 10). However, because the robotic system and
“mechanized pivot shift” studies accounted for 11 and
20 of the 48 included studies, respectively, comparisons
of methodologic quality across the numerous pivot-shift
testing systems must be performed with caution.
Collectively, only a few studies adequately justified the
sample size by performing a priori power analyses;
moreover, most studies did not confirm a normal distribution of data before performing parametric statistical tests. Generally, the best average scoring (2 of 2) was
found when we evaluated if appropriate control groups
were used, and the worst scoring (0.4 of 2) was found
in the description of loading system accuracy and
repeatability.
5
Knee Flexion Angles
The knee flexion angles used for simulated pivot-shift
testing were somewhat variable among studies: 31% of
the studies simulated the pivot-shift test at static flexion
angles, whereas 69% used a continuous range of motion. Among the studies using static flexion angles, the
most commonly tested angle was 30 , and the most
common range of motion tested in the continuous tests
was 0 to 90 . Data extracted from the studies that used
both static and dynamic techniques are reported in
Table 2.
Torques Applied
The loads applied in performing simulated pivot-shift
tests were also variable among studies (Fig 2). The use
of a valgus torque was described in 98% of the studies,
with a mean torque of 8.8 Nm (range, 1 to 25 Nm). In
58% of the studies, the use of an internal rotation (IR)
torque was described, with a mean torque of 5.3 Nm
(range, 1 to 18 Nm). Only 12% of studies described the
tension applied (ranging from 10 to 88 N) to the iliotibial band (ITB) during the simulated pivot-shift test.
Only 2% (1 study) applied axial compression of 38 N.
Specific Studies
Twenty-four studies are not fully described in the
tables because these studies either did not adequately
describe the applied forces or used variable magnitudes
of force to induce a pivot-shift phenomenon on a
specimen-by-specimen basis. More specifically, in 3
studies the combination of valgus moment and ITB
force necessary to elicit a pivot-shift phenomenon in
the ACL-deficient knee, as well as the knee flexion
angle at which the pivot-shift phenomenon occurred,
was determined by trial and error.23-25 In another study
the specimens were mounted on specially designed jigs
on the Instron Model 1125 Test System (Instron,
Canton, MA).26 The tibia was kept at 30 of IR and was
displaced anteriorly until the ACL failed. The authors
called it a re-creation of the clinical pivot-shift maneuver. Twenty studies described the use of a mechanized pivot-shifter device developed by the authors.
The mechanized pivot shifter consisted of a continuous
passive motion machine with a custom-made foot
holder that allowed application of IR and valgus
moment at the knee. The amount of IR torque was not
described in any study. Seven studies described the use
of 50 N (or 5 kg, equivalent to 49 N) of force applied 5
cm below the joint line on the lateral side of the
proximal third of the leg to create a valgus torque. The
remainder of the studies (13 studies) did not explicitly
specify the force applied to create a valgus torque.
The knee flexion angle at which the data were
extracted was not described in these articles either. The
studies were published between 2009 and 2012, and
the range of motion tested varied among studies, not
6
F. V. ARILLA ET AL.
Table 3. Summary of Studies That Applied Increasing Amounts of Load and Corresponding Relevance
Study
Fukuda et al.36
Loads Applied
0.0, 0.7, 1.7, 3.3, 5.0, 6.7, 7.5. 8.3,
or 10.0 Nm of valgus torque
Yamamoto et al.37
10-Nm valgus torque þ 5-Nm
internal rotational torque þ 0,
22, 44, or 88 N of ITB tension
Kanamori et al.38
10-Nm valgus torque combined
with either internal or external
rotational torque of 0.0, 1.7,
3.3, 5.0, 6.6, 8.3, or 10.0 Nm
Findings
Lower levels of valgus torque
(<5.0 Nm) may be preferable
because the risk of additional
damage to knee structures or to
the ACL graft is minimal but a
clinically significant simulated
pivot-shift test can be
performed.
The tibial subluxation elicited by a
simulated pivot-shift test in an
ACL-deficient knee was
significantly diminished by high
(88 N) ITB forces at high flexion
angles.
Internal tibial torque, rather than
external, resulted in more
coupled anterior tibial
translation; however, the
amount of internal tibial torque
should be small (<2 Nm).
Relevance
A valgus torque <5 Nm should be
applied when simulating the
pivot-shift test.
It is not clear whether researchers
who are going to simulate the
pivot-shift test in vitro should
consider the ITB tension as an
imperative part of their protocol
or not.
An internal torque, rather than
external, should be applied
when simulating the pivot-shift
test.
ACL, anterior cruciate ligament; ITB, iliotibial band; N, Newtons; Nm, Newton meters.
being described in all of them. The range of motion
tested, when described, varied between 0 and 120 of
knee flexion.
Outcome Measurement Parameters
ATT (in the medial, center, or lateral compartment)
was the most common parameter assessed as an
outcome measure during simulated pivot-shift testing
(44 studies, 91%). The second most assessed parameter
was internal tibial rotation (18 studies, 37%), and the
third most assessed parameter was the in situ force
either in the native ACL or in the graft (6 studies, 12%).
Tracking Systems
There was great variability in the tracking systems
used to acquire the kinematics among the studies that
did not use robotic systems with an incorporated
kinematic assessment tool. Two studies used the Polhemus Liberty electromagnetic system (Polhemus,
Colchester, VT). In 4 studies the kinematics of the
tibiofemoral joint was measured using a Polaris optical
system (Northern Digital, Waterloo, Ontario, Canada).
In another 4 studies, movement of the tibia relative to
the femur was recorded by taking a series of biplanar
photographs at every 5 of flexion. In 3 studies, tibial
rotation was recorded by a rotary potentiometer
attached through a bar linkage to the tibial shaft. One
study used the electromagnetic tracking device Flockof-Birds (Ascension Technology, Burlington, VT). In 1
study the displacement of the ACL graft was evaluated
using an Instron Model 1125 Test System. In 20 studies
the Praxim ACL Surgetics Navigation System (Praxim
Medivision, Grenoble, France) was used for kinematic
data acquisition.
Table 4. Summary of Studies That Reported Loads and Flexion Angles to Elicit Pivot-Shift Phenomenon
Bull et al.27
Markolf et al.25
Markolf et al.23
Load/Angle at Which Pivot-Shift Phenomenon Occurred
Range of
Knee Flexion
Motion
Valgus Torque, Nm
ITB Tension, Nm
Angle, Loads Applied
Tested, 0-, 5-, or 10-Nm valgus torque þ
0-120
7 4 (mean SD)
30
56 27 (mean SD)
0, 10, 20, 30, 40, or 50 N of ITB
tension
20-40
3.4 0.7 (mean SD) 29.0 5.6 (mean SD) 26.7 2.9 (mean SD)
The combination of valgus
20-40 3.06 1.3 (mean SD) 25.65 6.7 (mean SD) 27.8 3.5 (mean SD)
moment and iliotibial tension
necessary to pivot the ACLdeficient knee and the knee
flexion angle at which the pivot
occurred were determined by
trial and error for each
specimen.
ACL, anterior cruciate ligament; ITB, iliotibial band; N, Newtons; Nm, Newton meters.
SIMULATED PIVOT-SHIFT TEST
Relevant Findings
Several studies sought to identify the optimal forces
and torques necessary to simulate the pivot-shift test
in vitro. Some of them used a combination of ATT and
internal tibial rotation and considered ACL in situ forces
as the parameters to determine the most reliable
magnitude of forces and torques to simulate the pivotshift test. Combinations of forces and torques that
induced the greatest dislocation were considered optimal
(Table 3). These studies used robotic systems to apply a
simulated pivot shift in a static manner; thus the findings
may not be applicable to researchers who are planning to
perform a continuous simulated pivot-shift test.
However, several other studies that performed
simulated pivot-shift tests continuously over a range of
knee flexion also sought to determine the loads and
joint angles required to elicit the pivot-shift phenomenon in the specimens. Accordingly, the exact magnitudes of torque that were able to elicit the pivot-shift
phenomenon were recorded. The kinematic and kinetic
data were then pooled and reported. However, the
definition of pivot-shift phenomenon varied among
different studies. Bull et al.27 defined the pivot-shift
phenomenon as a sudden external tibial rotation,
whereas Markolf et al.23-25 defined it as the spontaneous reduction of the anteriorly subluxated lateral
tibial plateau. Their findings are shown in Table 4.
Discussion
The most important findings of this review were that
10-Nm valgus and 5-Nm IR were the most common
torques used to simulated the pivot-shift test, whereas
the most common knee flexion angle tested was 30 , at
which the shift also most commonly happened. Fortyeight studies using 10 different techniques were identified and summarized. Several techniques have been
used to simulate the pivot-shift test in vitro, and no
methodology can be defined as the gold standard.
Recently, a systematic review by Lopomo et al.28
identified 22 studies using simulated pivot-shift tests.
However, their aim was to describe the kinematic parameters that have been used to quantify the pivot-shift
test both in vivo and in vitro.
One of the limitations of elucidating a pivot-shift
phenomenon during a simulated pivot shift in vitro is
that, to date, the loads that clinicians apply during examination in vivo have not been determined. This is
because of the complexity of this test, which is performed dynamically with different forces and torques
applied simultaneously. To overcome this limitation,
researchers started to decompose the loads in vitro to
analyze the role of each torque separately. Matsumoto,16 in a seminal study on the topic at hand, found
that an absence of subluxation was seen in knees with a
flat or less convex tibial plateau. Bull et al.27 in 1999
also deconstructed the loads of the pivot shift and
7
analyzed different amounts of valgus torque and ITB
tension. They found that tibial translation during the
pivot-shift test cannot be predicted from anteroposterior laxity. Furthermore, Kanamori et al.29 in
2000 compared the effect of an IR torque when combined with a valgus torque and showed that applying
the combined loads significantly increased ATT in the
ACL-deficient knee.
Variation in performing the pivot-shift test has long
been regarded as the principal challenge for achieving a
repeatable objective and quantitative measurement,30
with the simulated pivot shift partially addressing this
challenge by allowing a highly repeatable maneuver
with specified loads and kinematics, especially when
using a robotic system. This systematic review identified
11 studies using robotic systems.17,18,29,31-38 The accuracy of these systems ranged from 0.1 to 0.2 mm for
translation and from 0.02 to 0.2 for rotation, which is
of great importance when aiming to detect small
changes in kinematics, such as assessing partial ACL
tears or analyzing the effect of different tunnel positions
found among different ACL reconstruction techniques.
These changes in kinematics are too small to be
distinguished during manual examinations.39 The loads
were also applied under very accurate control, with the
control of the systems being described as a range of 0.2
to 0.4 N for forces and 0.01 Nm for moments. All robotic systems were able to precisely control the forces
and torques applied, acquiring the maximum score in
this parameter (Appendix 1, index item 9, available at
www.arthroscopyjournal.org), whereas non-robotic
studies averaged 1.5 of 2. Furthermore, robotic systems had the advantage of high repeatability. The limitation of the simulated pivot-shift test performed on
robotic systems is that 100% of the techniques identified in this review were performed in a static manner
and confined to a few flexion angles. Besides, in 9
studies (81% of the studies using robotic systems) only
valgus torques or IR torques (or both) were applied,
which do not fully represent the combination of dynamic loads applied during the pivot-shift test in vivo.
Moreover, to clamp the specimens to the robotic system, the femur and tibia were sectioned around 13 to
20 cm from the knee joint line and muscular loads were
not simulated, which may affect the pivot-shift phenomenon. Overall, it is more preferable to use robotic
systems because of better control of loading and higher
accuracy of tracking systems.
In this systematic review we identified 37 studies that
did not use a robotic system. The testing devices were
named differently by the authors: “biomechanical
testing apparatus,”40-42 “rig,”20,43,44 “mechanical pivot
shift device,”19 “apparatus,”16,45-47 “pivot-shift test
apparatus,”23-25 “experimental setup,”27 “experimental
arrangement,”48 “specially designed jigs,”26 and
“mechanized pivot shifter” (Appendix 2, available at
8
F. V. ARILLA ET AL.
www.arthroscopyjournal.org). Of these alternative devices, 92.5% allowed the simulated pivot-shift test to be
performed continuously through the range of motion.
This continuous methodology is able to give researchers
more comprehensive data; however, the starting position of each trial is not strictly controlled, in contrast to
robotic systems, because the flexion/extension path is
manually performed. Moreover, the loads are not under strict control. ATT was the most commonly
measured parameter to evaluate tibiofemoral joint
motion. This is consistent with the literature that has
described ATT as the most reliable parameter when
evaluating the pivot-shift test.39,49,50
There were differences across studies regarding the
flexion angle at which the pivot shift was observed,
probably because of the differences in their testing
systems. As observed both clinically and during
continuous simulated studies in vitro, the pivot-shift
phenomenon occurs most commonly around 30 of
flexion. This was the most common flexion angle tested
in both static and dynamic simulations. Accordingly,
future studies that attempt to simulate the pivot shift
should include assessment of kinematics at 30 of
flexion. Moreover, it is recommended to apply a valgus
torque of 10 Nm and IR torque of 5 Nm.
Not all studies in this review used the same definition
for the pivot-shift phenomenon. Sena et al.19 called the
pivot-shift event the anterior and internal rotatory subluxation that was observed at between 10 and 30 of
flexion followed by a posterior and external rotatory
reduction at between 40 and 60 . However, most
studies considered only the reduction phase as the pivotshift phenomenon. Musahl et al.51 reported that the
reduction in the subluxated knee occurred at between
25 and 35 in all knees with both a manual and
mechanized pivot-shift technique. Studies that applied
increasing amount of loads to elicit the pivot-shift phenomenon found that the critical loads and joint positions
varied among specimens, showing the different responses that the same load causes in different knees.
The strengths of our study are the duplicated
comprehensive search, high agreement found between
reviewers, and application of a novel qualityassessment scale. Despite all the research that has
been developed regarding the pivot-shift test, no technique has been able to create ACL injury through a
pivot-shift mechanism. This limitation may be attributable to different mechanisms of injury when
comparing in vitro models with the in vivo knee. ACL
injury in in vitro models is performed by surgical
transection, whereas most in vivo injuries occur
through a pivoting mechanism, which may damage
additional surrounding structures that may play an
important role in providing rotational knee stability. In
particular, structures of the lateral capsule have
recently received increased attention, with some
authors suggesting that damage to these structures may
underlie the pivot shift.
In the future, a standardized methodology for simulating the pivot-shift test in vitro needs to be established. Such methodology must re-create the kinetics of
the clinical maneuver, thereby consistently producing
the pivot-shift phenomenon while simultaneously
capturing joint kinematics. This highly accurate and
repeatable simulation will in turn make the findings
from these studies more applicable to the care of
patients.
Limitations
A limitation of this study is that the analyses of heterogeneous techniques did not allow the reviewers to
make direct comparisons across studies, such as summarizing the relation between the loads applied and
ATT. In addition, the proposed index for evaluating the
methodologic quality of the included studies has not
been validated.
Conclusions
This study systematically reviewed the methodology
for simulating the pivot-shift test as available in the
current literature. It is recommended that researchers
who aim to simulate the pivot-shift test apply torques of
10 Nm for valgus and 5 Nm for IR, with analysis of knee
kinematics at 30 of flexion serving as a minimum.
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SIMULATED PIVOT-SHIFT TEST
Appendix
Appendix 1: Methodologic Index for Cadaveric
Studies
The items of the methodologic index were scored as
follows: 0, not reported; 1, reported but inadequately;
and 2, reported adequately. The total score ranged from
0 (lowest) to 24 (highest).
1. Purpose: The aim or objective is clearly stated, with
an associated hypothesis that is testable by statistical methods.
2. Control groups: Appropriate, healthy controls are
included.
3. Specimen demographics: Characteristics of cadaveric specimens are adequately described, including
number of specimens, age (mean and variance, i.e.,
standard deviation or range), gender, and inclusion/exclusion criteria.
4. Specimen preparation: The process for specimen
preservation (i.e., freezing, thawing) and positioning in the pivot-shift simulation device are
clearly described.
5. Experimental procedure: The testing protocol is
described in sufficient detail so as to be independently replicable.
6. Power analysis: A priori justification of the sample
size for both the experimental and control groups
needed to determine statistical significance is
described, in particular noting the resulting power
and/or a values.
7. Statistics: A description and implementation of
statistical tests appropriate to the dataset, with reported P values, are provided. Confirmation of the
normal distribution of data must be explicitly stated
if parametric statistical tests are to be used.
10.e1
8. Testing kinematics: The joint angles, with particular
focus on the knee, at which the simulated pivotshift test is performed and from which data are
measured, are clearly stated. If proximal (e.g., hip)
or distal joints are constrained during testing, an
explanation is provided.
9. Testing torque/forces: Application of joint forces
imparted by the simulated pivot-shift system is
provided, including valgus/varus, tibial rotation,
and tibial translation. It should be noted that torque
is the more rigorous measure.
10. Tracking system accuracy: The accuracy/repeatability of the system used to measure joint kinematics (joint angles, translation distances, and
so on) is explicitly stated or the study in which
these details were originally determined is clearly
cited.
11. Loading system accuracy: The accuracy/repeatability of the system used to apply joint forces
(torque, translational forces, and so on) is explicitly
stated or the study in which these details were
originally determined is clearly cited.
12. Rationale for simulation parameters: Because
consensus on proper clinical performance of the
pivot-shift examination does not exist, nor are the
in vivo dynamics necessary to induce a pivot shift
clearly established (and it will be variable across
individuals), the authors provide justification of the
simulation parameters (flexion angles, torque
magnitude, and so on) as a measure of external
validity. Equally appropriate is the application of
specific loads to each individual specimen (on a
trial-and-error basis) as necessary to induce the
pivot-shift phenomenon, but these values must be
reported.
10.e2
F. V. ARILLA ET AL.
Appendix 2: Devices Used and
Methodologic Quality Score for 48
Included Studies That Performed
Simulated Pivot Shift
The methodologic quality was graded based on the
score as follows: 21 to 24, excellent; 17 to 20, good; 13
to 16, moderate; and less than 13, poor (Appendix
Table 1).
Appendix Table 1. Devices Used and Methodologic Quality
Score
Study
Robotic system (n ¼ 11)
Diermann et al.17
Goldsmith et al.18
Xu et al.34
Herbort et al.31
Herbort et al.32
Kanamori et al.29
Wijdicks et al.33
Zantop et al.35
Fukuda et al.36
Yamamoto et al.37
Kanamori et al.38
Biomechanical testing apparatus (n ¼ 3)
Engebretsen et al.40
Anderson et al.41
Tsai et al.42
Rig (n ¼ 3)
Kondo et al.20
Kondo et al.43
Kondo et al.44
Mechanical pivot-shift device (n ¼ 1)
Sena et al.19
Apparatus (n ¼ 4)
Matsumoto16
Matsumoto et al.45
Matsumoto et al.46
Matsumoto et al.47
Pivot-shift test apparatus (n ¼ 3)
Markolf et al.23
Markolf et al.24
Markolf et al.25
Experimental setup (n ¼ 1)
Bull et al.27
Experimental arrangement (n ¼ 1)
Lie et al.48
Specially designed jigs (n ¼ 1)
Stapleton et al.26
Mechanized pivot shifter (n ¼ 20)
Bedi et al.52
Bedi et al.53
Bedi et al.54
Bedi et al.55
Citak et al.56
Citak et al.57
Citak et al.58
Cross et al.59
Dawson et al.60
Score
Grade
19.5
21
18
21
20
20.5
17.5
19.5
19
18.5
16
Good
Excellent
Good
Excellent
Good
Good
Good
Good
Good
Good
Moderate
18.5
18
21.5
Good
Good
Excellent
14
18
18
Moderate
Good
Good
17.5
Good
11
11
8.5
11.5
Poor
Poor
Poor
Poor
16
16
14
Moderate
Moderate
Moderate
13.5
Moderate
14.5
Moderate
11
13
14
12.5
11.5
13
10.5
12
9
16
Poor
Moderate
Moderate
Poor
Poor
Moderate
Poor
Poor
Poor
Moderate
(continued)
Appendix Table 1. Continued
Study
Galano et al.61
Musahl et al.62
Musahl et al.63
Musahl et al.51
Musahl et al.64
Petrigliano et al.65
Suero et al.66
Suero et al.67
Suero et al.68
Voos et al.69
Voos et al.70
Score
7
16
12.5
15
15
15.5
11.5
10
10
13.5
11
Grade
Poor
Moderate
Poor
Moderate
Moderate
Moderate
Poor
Poor
Poor
Moderate
Poor