- Email: [email protected]
Experimental Execution of the Simulated Pivot-Shift Test: A Systematic Review of Techniques
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
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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
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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
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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.
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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.
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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.
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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
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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
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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
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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 10. Benjaminse A, Gokeler A, van der Schans CP. Clinical diagnosis of an anterior cruciate ligament rupture: A meta-analysis. J Orthop Sports Phys Ther 2006;36:267-288. 11. Kaplan N, Wickiewicz TL, Warren RF. Primary surgical treatment of anterior cruciate ligament ruptures. A long-term follow-up study. Am J Sports Med 1990;18: 354-358. 12. Kocher MS, Steadman JR, Briggs KK, Sterett WI, Hawkins RJ. Relationships between objective assessment of ligament stability and subjective assessment of symptoms and function after anterior cruciate ligament reconstruction. Am J Sports Med 2004;32:629-634. 13. Leitze Z, Losee RE, Jokl P, Johnson TR, Feagin JA. Implications of the pivot shift in the ACL-deficient knee. Clin Orthop Relat Res 2005:229-236. 14. Ayeni OR, Chahal M, Tran MN, Sprague S. Pivot shift as an outcome measure for ACL reconstruction: A systematic review. Knee Surg Sports Traumatol Arthrosc 2012;20: 767-777. 15. Hefti F, Muller W, Jakob RP, Staubli HU. Evaluation of knee ligament injuries with the IKDC form. Knee Surg Sports Traumatol Arthrosc 1993;1:226-234. 16. Matsumoto H. Mechanism of the pivot shift. J Bone Joint Surg Br 1990;72:816-821. 17. Diermann N, Schumacher T, Schanz S, Raschke MJ, Petersen W, Zantop T. Rotational instability of the knee: Internal tibial rotation under a simulated pivot shift test. Arch Orthop Trauma Surg 2009;129:353-358. 18. Goldsmith MT, Jansson KS, Smith SD, Engebretsen L, LaPrade RF, Wijdicks CA. Biomechanical comparison of anatomic single- and double-bundle anterior cruciate ligament reconstructions: An in vitro study. Am J Sports Med 2013;41:1595-1604. 19. Sena M, Chen J, Dellamaggioria R, Coughlin DG, Lotz JC, Feeley BT. Dynamic evaluation of pivot-shift kinematics in physeal-sparing pediatric anterior cruciate ligament reconstruction techniques. Am J Sports Med 2013;41: 826-834. 20. Kondo E, Merican AM, Yasuda K, Amis AA. Biomechanical comparisons of knee stability after anterior cruciate ligament reconstruction between 2 clinically available transtibial procedures: Anatomic double bundle versus single bundle. Am J Sports Med 2010;38:1349-1358. 21. Slim K, Nini E, Forestier D, Kwiatkowski F, Panis Y, Chipponi J. Methodological index for non-randomized studies (MINORS): Development and validation of a new instrument. ANZ J Surg 2003;73:712-716. 22. Detsky AS, Naylor CD, O’Rourke K, McGeer AJ, L’Abbe KA. Incorporating variations in the quality of individual randomized trials into meta-analysis. J Clin Epidemiol 1992;45:255-265. 23. Markolf KL, Jackson SR, McAllister DR. Relationship between the pivot shift and Lachman tests: A cadaver study. J Bone Joint Surg Am 2010;92:2067-2075. 24. Markolf KL, Jackson SR, McAllister DR. A comparison of 11 o’clock versus oblique femoral tunnels in the anterior cruciate ligament-reconstructed knee: Knee kinematics during a simulated pivot test. Am J Sports Med 2010;38: 912-917. 25. Markolf KL, Park S, Jackson SR, McAllister DR. Simulated pivot-shift testing with single and double-bundle anterior
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56. Citak M, Bosscher MR, Citak M, Musahl V, Pearle AD, Suero EM. Anterior cruciate ligament reconstruction after unicompartmental knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2011;19:1683-1688. 57. Citak M, O’Loughlin PF, Citak M, et al. Influence of the valgus force during knee flexion in neutral rotation. Knee Surg Sports Traumatol Arthrosc 2012;20:1571-1574. 58. Citak M, Suero EM, Rozell JC, Bosscher MR, Kuestermeyer J, Pearle AD. A mechanized and standardized pivot shifter: Technical description and first evaluation. Knee Surg Sports Traumatol Arthrosc 2011;19: 707-711. 59. Cross MB, Musahl V, Bedi A, et al. Anteromedial versus central single-bundle graft position: Which anatomic graft position to choose? Knee Surg Sports Traumatol Arthrosc 2012;20:1276-1281. 60. Dawson CK, Suero EM, Pearle AD. Variability in knee laxity in anterior cruciate ligament deficiency using a mechanized model. Knee Surg Sports Traumatol Arthrosc 2013;21:784-788. 61. Galano GJ, Suero EM, Citak M, Wickiewicz T, Pearle AD. Relationship of native tibial plateau anatomy with stability testing in the anterior cruciate ligament-deficient knee. Knee Surg Sports Traumatol Arthrosc 2012;20:2220-2224. 62. Musahl V, Bedi A, Citak M, O’Loughlin P, Choi D, Pearle AD. Effect of single-bundle and double-bundle anterior cruciate ligament reconstructions on pivot-shift kinematics in anterior cruciate ligament- and meniscusdeficient knees. Am J Sports Med 2011;39:289-295. 63. Musahl V, Citak M, O’Loughlin PF, Choi D, Bedi A, Pearle AD. The effect of medial versus lateral meniscectomy on the stability of the anterior cruciate ligamentdeficient knee. Am J Sports Med 2010;38:1591-1597. 64. Musahl V, Voos JE, O’Loughlin PF, et al. Comparing stability of different single- and double-bundle anterior cruciate ligament reconstruction techniques: A cadaveric study using navigation. Arthroscopy 2010;26:S41-S48. 65. Petrigliano FA, Musahl V, Suero EM, Citak M, Pearle AD. Effect of meniscal loss on knee stability after single-bundle anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2011;19:S86-S93 (suppl 1). 66. Suero EM, Citak M, Choi D, et al. Software for compartmental translation analysis and virtual three-dimensional visualization of the pivot shift phenomenon. Comput Aided Surg 2011;16:298-303. 67. Suero EM, Citak M, Cross MB, Bosscher MR, Ranawat AS, Pearle AD. Effects of tibial slope changes in the stability of fixed bearing medial unicompartmental arthroplasty in anterior cruciate ligament deficient knees. Knee 2012;19:365-369. 68. Suero EM, Njoku IU, Voigt MR, Lin J, Koenig D, Pearle AD. The role of the iliotibial band during the pivot shift test. Knee Surg Sports Traumatol Arthrosc 2013;21: 2096-2100. 69. Voos JE, Musahl V, Maak TG, Wickiewicz TL, Pearle AD. Comparison of tunnel positions in single-bundle anterior cruciate ligament reconstructions using computer navigation. Knee Surg Sports Traumatol Arthrosc 2010;18:1282-1289. 70. Voos JE, Suero EM, Citak M, et al. Effect of tibial slope on the stability of the anterior cruciate ligament-deficient knee. Knee Surg Sports Traumatol Arthrosc 2012;20:1626-1631.
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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.
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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.
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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
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
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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.
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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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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.
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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.
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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